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bargain 12-candle gas; according to Dr. Frankland they give 121, that is they have fulfilled their agreement, and it is travelling out of the question to say that under other conditions other cities have better gas. The real truth, however, is that only on very rare occasions is the gas anything like this, and the average is probably over 13 candles, and in no single instance that ever I heard of has the gas ever been, as stated, 9 candles, unless absurdly burnt.

Such an assertion as that the gas now is worse than it was years ago is really too absurd. The only real basis for it is an apparent increase in the quantity of sulphur, while there is really a great decrease; but within the last few years the process of testing has been so greatly improved that what previously passed undiscovered is now detected, as the gas referees appointed in the interest of consumers pointedly show, and thus as fast as the companies succeed in removing more impurity, so previously unascertained impurities are presented. The best answer is that it pays to purify, as the impurities, when collected, are valuable and SIGMA.

saleable matters.

ELECTRO-MAGNETISM AS A MOTIVE POWER. [813] SIR,-Many people have endeavoured to utilize electro-magnetism to work machinery, and it is easily accomplished in many ways, but it is extremely improbable that it ever will become a practical source of mechanical force, except for small work and special purposes. The only thing which would render this probable is the discovery of such a source of electricity as would be nearly costless, and this is quite possible, as many chemical changes are carried out on a large scale for their final results in which the force they give out is thrown away. In fact I quite clearly foresee that the day will come when chemical works will concentrate themselves, and distribute the electrical force they now throw away, and send it out by conductors for use elesewhere, just as is now done with gas and water. But the ordinary conditions reverse this state of things: our batteries are worked for their electric force, and their chemical products thrown away, and under these conditions the cost is so great that it cannot compete

with steam.

**Thinker" (p. 544) has correct views to some extent, but he has not yet carried that extent far enough. His idea that a coal fire is an electrical battery, is thus only a partial truth, thongh a favourite notion some time ago, before the grand doctrines of the correlation of the force were established, and the modern clear ideas of the nature of force fully devoloped. Every chemical action and every mechanical motion is a translation of energy from one form to another; whether it is to take the form of heat or electricity, or mechancial motion, or be stored up quiescent to be again set free, is governed by the conditions of each case. But let me beg "Thinker" to cast away all notions as to" electricities uniting" to canse heat, &c., because these were the roundabout inventions of days when the nature of forces was little understood, and men were determined to have some definite embodiment of what they did not comprehend, instead of waiting for fuller knowledge. The real point lies here: in burning ordinary fuel we seldom utilize more than one-tenth of the force, that is, we waste nine-tenths in the process of conversion of latent force into motion. We can convert electrical force into motion with less loss, but the present known means of conversion of latent force into electricity are much more costly than those by which we can obtain heat; in fact, they are generally the results of several previous processes in which force has been rendered latent by chemical decompositions, as by reducing the ores of zinc, a much more expensive proces than the exactly similar one of reducing what we may call the ore of carbon, i.e., carbonic acid, by heat from the sun and storing it as wood and coal. The economy of electro-magnetism as a motive force depends, therefore, upon the relative costs and proportional losses of these

several processes.

Now we do not, as "Thinker " supposes, collect all the force of a battery in the two wires and utilize it; part is lost in the liquids which are heated, so also in the wires themselves, and in fact throughout the whole circuit. The point on which "Thinker," like most others, really fails is, however, I think, in overlooking the fact that an electro-magnet requires time to develop force; although the current generates magnetism in an infinitesimal period, the full power is only reached gradually in a time dependent on the quality of the iron or its specific resistance to molecular changes; the purer and softer the iron the less time needed; therefore when numerous changes take place in the circuit, the magnetic force generated is small, the power developed by the battery is used up in producing molecular changes, passes into heat, and is lost, instead of into magnetic power and motion.

SCIENTIFIC EDUCATION.

SIGMA.

[314] SIR, Generally speaking he must be a bold man who would introduce innovations amid old established and well-known customs, but there are times when it is necessary to speak plainly, and this must be my excuse for troubling the readers of the ENGLISH MECHANIC with a long dissertation upon education. The topic has lately and will be again in the minds of every one. Unfortunately a great calamity has fallen upon the nations of the earth, and the surprise and consternation created by a dreadful war erases every other subject for the time being from the tablets of our memory. The Quakers are right; it is inhuman and barbarian to lead our fellow-men to the shambles for wholesale slaughter. Let our cry arise compelling the great ones to submit their differences to arbitration,

COMPOSITION OF THE METEOT [315] SIR,-Can you, or any of year readers, tell me if it is correct that orgsewr The metten k been found in meteorites ? contain, it is said, 6 per cent. of age or M. Wohler inferred from this that are a teorites came from organic matter and in. must have existed. The organic matter is Le as a kind of black mould of carbon, styen, aus. drogen, in the same proportions as they dota 2 p and is it possible that this sabotan vara enke the meteorites along with the seal increas stituents) could have originaliter fra the se place as the meteorites themes, vilt a lang substance entirely?

and let us determine to evade to the utmost being public do not know the percentage d
drawn into a sanguinary war, declared for no earthly sent).
4. The institution of a club-home a
reason except the ambitions designs of one or two
men. But I must not allow myself to be led into a de- appointments could be made, bacLS &
clamatory essay upon war. This is not the time, not and some means attached to it b
the place, for such a subject. The aim of every English- agents could be avoided. I need
maushould be to seek the welfare of his native country; the agents prey upon the weakes
but in order to do this we must know exactly what she assistant pays all, and the all i
has, and what is wanting. Very tritely a con- whilst the rich principal gets of
tributor to Nature summed up this question: "Edu- both benefited to the same exten
cation and science," he says, "at the present moment bear the fine if it be found needi
are England's greatest needs." And he is quite right. 5. Periodical meetings, &C."
Just for a moment then we will endeavour to inquire Such, then, is a rough draft
into the exact position of England as regards these sub- by the editor of the Quarterly
jects. Education may conveniently be divided into who has already issued invitas
three kinds: a Primary, 8 Secondary, and Highest. sentative gentlemen for a prelim.
Of these the first has but just now been dealt with by to be held immediately, wien ina
Parliament, and I am sure the Bill passed during the decided upon. Till now a mass o
last session, through the exertions of Mr. Forster will plined men, mingled with stalwar
not lack the hearty good wishes of the whole popula- leaders capable of understanda
tion for its success. Time, and time alone, will prove been fruitlessly contending against
its worth. The last of these three kinds will scarcely of ignorance. Is this to conta"
claim our attention at the present time; so it is Second-wide and exposed, the ramparts to se
ary education, the education of the mechanical and before the combined efforts of the ret
middle classes, the stay and backbone of England, do not for a moment believe that the 26
that attracts our notice. What can be said for it? noble men will be fruitless, but
Little that is good. Certainly here and there, good prove conquerors. Men, be up and de
schools under ablo conductors have sprang up. tight; the task is difficult; but, with E...
but they are the exception not the rule. The ma- wheel, who dare stand in the road?
jority of these schools are under the direction of
speculators, men incapable to doing the work required,
caring nothing whether that work be done or not, so
that they live comfortably and are never required to
exert themselves. I am writing this from a town
containing some two score of so-called middle
class schools, and of these there are but about
three deserving to be called schools. I could not
describe the principle of the remainder, or the,
ordinary, "school routine," without giving some clue to
their whereabouts. Perhaps, however, it may open
the eyes of parents to hear such facts as the following:
-A friend of mine was engaged by a lady to give
lectures to the young ladies of her establishment. During
a conversation which occurred, the lady principal said
"Could you not, Mr. M, teach Miss A, B, and C, so-
and-so? It would be a good thing for them to go home
and say, I am doing such and such lessons at school.'
It would be mentioned to friends, the prestige of the
school would be raised, and an increase of pupils would
be the ultimate result." Thus the useful was to give
way to the worthless; but happily Mr. M was not
compelled to remain in a situation in which he could
not conscientiously perform his duties, so he did
nothing of the kind, and left at the end of the term.
I constantly read in the correspondence columns of
our ENGLISH MECHANIC, that English houses cannot
turn out certain work to equal that of Continental
labourers. There must be a reason for this, and may
it not be assigned to the lack of scientific training? The
eye has not been trained by the inspection of beautiful
works of art-the hand has not been trained to draw
cunningly devised and elaborate designs of machinery
or architecture-the head has not been trained to adapt
the natural laws which regulate the universe, and hence
so much heartburning over ill-adapted inventions, in-
ventions utterly worthless, but over which men have
spent years of labour, and scores of pounds. Even now we
are constantly be-dinned-ay, and by experienced Sigma" might have been a little more exp
workmen too-with the feasibility of "eternal motion." explanation of the sulphate of lead and
Friction, wear-and-tear, &c., &c., can all be overcome.
batteries. I have had a six-cell battery in co
It was but last year that many pounds were spent upon for fourteen months for domestic purposes,
a machine in this town for the above object; the the whole of that time I have had no trouble v
originators knew they could do it, but they haven't, they only requiring water to compensate ten-
nor would they listen to advice. Again, but lately, tion, and I can assure "M.R.C.S." that, pla
another idea concerning " 'perpetual motion," was
mooted and worked out in the brains of two workmen, charged. They are made as follows:-Get a
speaking, they are as powerful now
and they would, but for your humble servant's objec-glazed inside, in which fit a cylinder of zine a
tion, have spent their all upon a worthless scheme. In
every town it is so, and will be till scientific education
has entered upon another phase of its history. Our
schools, under the present system, are useless. How
can a man teach science who is utterly ignorant of it
himself? We have here a clue to our failures. The
masters are incompetent, and the work is not done.
Let us have some recognized diploma which every pro-
fessional man shall be compelled to obtain before
entering upon his scholastic career. A plan has lately
been mooted which meets with approbation from men
celebrated for their knowledge of the subject. It is
this-that we start de novo, gaining experience from
previous failures. A society of principals, assistants,
and all interested in the question must be formed, for
individual exertion is of no avail. I will, again, take
the liberty of quoting from a letter which appeared in
the columns of a contemporary on August 4:-

"This society should have certain objects, and its
members combined should use their utmost endeavours
to assist in carrying out these objects. A few of the
aims would be as follows:-

1. The institution of normal colleges for the training of gentlemen who wish to enter the scholastic profession.

2. To recognise some examination, diploma, &c., as sufficient guarantee of the capabilities of gentlemen entering the profession, and insist that such gentlemen shall have this diploma. The evils arising from the incapability of so many of our masters cannot be overestimated.

3. The necessity of Government or other central supervision and examination of every school. At the present moment the standard of a school is calculated by nothing. . . . It is impossible to decide upon the general tone of a school by the examination of a few of the best boys. (In many schools a few of the best boys are regularly sent to the Oxford or Cambridge middle-class, and other similar examinations. The

If any of your astronomis crescendents wald give me some informater enga of the meteorites, I should feeland to tama; sad can any reason be given the terms in int stones are so rich in n VA, SÅ STEV tively poor in oxygen ?

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(I believe among them Profesor Bak
suppose the earth to have been fed by
gation of meteorites; but from wheat & "ALL SEN
originally derived? and what is its presenc

P. S.-Is it likely that meteorites, indica el b the remnants of former worlds, are the mat as a of which worlds are forming? and how do th on the nebular theory of Laplace?

BATTERIES.

[316] SIR,-I am inclined to agree wi M.R.C.S. & New Sab. marks of " 4050, 915

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cylinders; now get some thin sheet-copper
four copper cups about 2in. diameter and so
one above the other and about 1in. apart
Now mix sulphate of lead with water to the a
copper rod in diameter, this will be the cre
of clay, and fill the copper cups with it.
in the porous cell and fill with water, charg
cell with sea-salt and water and it is ready:
examined mine the other day and found b
wear in the zinc, in the copper the loss
of which I have had in use seven months,
ceptible. I am now trying the manganese bá
I am very much pleased with their action.
a sketch to scale (if worth inserting) of the leg:
JOHN

thick next get a porous cell that will fit eaără

2

NORFOLK GEOLOGY.-At the recent meeting London Geological Society the Rev. John read a paper "On the Relative Position * -j Forest Bed of the Chillesford Clay in Norfolk Suffolk, and on the real Position of the F Bed," in which he stated that both at Easton & and at Kessingland the Forest Bed is to ex underlying the Chillesford clay. He considered forming part of the beach or of the foot of the el the soil of the Forest Bed had been deposited estuary, and that, after its elevation, trees of which stools are now visible along the coast, grew upon it, the true forest bed was formed. After the submer of this, first freshwater, then fluvio-marine, and al marine deposits were formed upon it; and the s proposed to give the whole of these deposits the sa of the "Forest Bed Series." The author suggested tr bed which lies immediately upon the chalk and betwe the Forest Bed itself is represented inland by the the it and the fluvio-marine and marine crags, his the being that the surface of the chalk, after supportia forest bed fauna, was gradually covered up by success crag deposits.

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REPLIES TO QUERIES.

ested to mention in each instance the title and
ber of the query asked.

and ammonia it is precipitated as a crimson powder; of course depends on the work it has to do. Third, the alkaline earths give purple precipitates." Green Smee's. Fourth, answered by the second. Lastly, yes.precipitate is obtained by mixing solutions of cupric R. M. sulphate (or nitrate) and sodic carbonate. I have often In their answers, Correspondents are respectfully obtained this precipitate, but not recently, and I do not remember whether it is dark or light.-OxONIENSIS. [4224.]-TREATMENT OF A CHRYSALIS.-Pupe of such insects as require to be kept damp should be kept in a common flower-pot filled with light earth. In this they should be buried about fin., and on top of the earth there should be kept a rag moistened about once a week, just sufficient to prevent the earth becoming dry. Other kinds do not require any particular treatment. S. C.

12.1-GAS METERS.-Among your "Unanswered
ies" is the above. I should have answered it at
ime, but was in hopes that some more able pen
mine would have done so. The following details-A.
I hope, be understood:-Fig. 1 is a dry meter, with

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of force the front taken off; Fig. 2 is a plan of the same at the sare farine AB; D D is the diaphragm, the face is of stout tin, theory and the sides of very supple leather; B is a bracket, onnected to same at the joints or hinges, H H; G is -he guide rod, carrying the bracket B; L, the lever ixed at top of guide rod; S T, the stuffing-box, to preRA ent the gas getting into the top of meter; T, tangent or regulating meter; W, toothed wheel, fixed on spindle onnected with index; S, spiral screw to turn W; C, rank to work valves; V, valves. I have only shown ne lever and valve in Fig. 1, to prevent confusion. C s a little brass catch, with a weight at one end to keep had upright, which catches the tangent rod each revoluhs for de-ion, and prevents the meter being worked backwards timely dishonest persons. The gas goes in at the pipe aarked "inlet," and through the one shown by the dotted ine from A, and enters the valve box at the hole shown Fig. 2. It then passes through the valves into the piaphragms or measuring chambers, back again mades hrough the valves, and along the other pipe, shown by ich flotted line to B. The inlet and outlet pipes are carried roadtown the sides of the meter below the dotted line, but hey only act as siphons to catch the condensation. The liaphragms move backwards and forwards like two pair f bellows, and as the outside is used as well as the inide, it thus makes four measuring chambers, which re filled and employed alternately by the action of the valves. The distance over which the diaphragms travel pper pt each revolution is regulated by the tangent T being ill toved nearer to or farther from the centre spindle to afer and hich it is fixed. The valves have three holes or ports; daye middle one, marked No. 2, is always covered by the p of the valve, which is hollow and just large enough the man cover two holes at once, which are then connected.

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Copper t

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At the as the guide rods.

B

[4481.]-A DIFFICULTY.-In answer to "T. A. Burge" (p. 502), I may say that the standard barometer is usually provided with an ivory or metal point, as mentioned by Tomlinson, to which the surface of the mercury in the chamber is raised or lowered by means of the screw before reading. In some, however, the scale and point are moved to the mercury, instead of the mercury to the point. This adjustment, far from being clumsy, is extremely fine and accurate.-A. M. W.

[4490.]-WELDING CAST-STEEL.-Take 1oz. smelts blue, oz. rock salt, 2oz. borrocks, pounded together and fused in a ladle over the fire, and when cool reduce to powder; heat the steel to what smiths call a greasy heat; use the powder the same as sand. The weld will be much stronger if veed together instead of common

scarfed.-A BLACKSMITH.

[4517.]-STAINING GUT FISHING LINES.-Gut may be stained a pale brown and favourite colour by steeping it in a strong decoction of warm tea. A blue colour may be given by steeping in a weak logwood decoction for about five minutes, and rinsing afterwards in alum-water.-VIVIS SPERANDUM.

[4518.]-MYROBALANS are dried fruits of different sorts of Terminalia, myrobalan order or Combretacea, imported from India for the use of dyers and tanners.

[4242.]-INCRUSTATION IN BOILERS, ETC.-The
following description of an invention for the prevention
of incrustation in boilers, is extracted from the Student
and Intellectual Observer, No. XIII. (February, 1869).-
"Among the many inventions for effecting this object,
one by Mr. C. Weightman Harrison, of Clapham June-
tion, is simple, and seems to be founded on a scientific
principle. He suspends in the boiler a plate of metal-
of course immersed in the water-which is connected
with the metal of the boiler. The boiler forms one elec-
trode, the suspended plate the other. The size of the
metal plate is so proportioned to that of the boiler, that
the electro-chemical action upon its interior surface
shall be what he terms nascent, or nearly so; and he
states that he finds it merely necessary, under ordinary
circumstances, to impart a polarity to the shell of the
boiler, in order to prevent the adhesion of the precipi--BERNARDIN.
tated matters. Sometimes he varies the method of carry-
ing out his invention by means of an additional electrical
source, so arranged as to transmit alternately positive
and negative currents to the shell of the boiler, and to the
suspended plate. This arrangement is found greatly to
facilitate the production of steam." It is possible, how-
ever, that as "A New Subscriber" dates from Brussels
he would meet with many difficulties-leaving cost en-
tirely out of the question-the extent whereof alone
would prevent the adoption by him of the above inven-
tion, although fully convinced of its utility. To obviate
this (assumed) difficulty, to a certain extent, I may
mention that sal-ammoniac is capable of re-acting
chemically, to dissolve, in part, the incrustation; and
carbonate of potash, to decompose without completely
dissolving it, leaving, it must be admitted, at least car-
bonate of lime insoluble, and capable, under certain
circumstances, of still forming a scale.-S.... R.

[4270.]-CHEMICAL.-The following is taken from
Fownes's "Elementary Chemistry":"Magnesium may
be prepared by reducing with metallic sodium the
double chloride of magnesium and sodium, which is
formed by dissolving caustic magnesia in hydrochloric
acid, and adding an equivalent quantity of common salt,
This
evaporating to dryness, and fusing the residue.
product, heated with sodium in a wrought-iron crucible,
yields magnesium, which may be freed from impurities
by distillation. Metallic sodium may be prepared in
the laboratory by distilling in an iron retort 717 parts of
dry sodic carbonate, 175 parts of dry charcoal, 108 parts
of dry chalk. These materials must first be well
pounded together. Potassium is prepared in the same
way from its carbonate, which is prepared by passing
carbonic acid through a solution of caustic potash."-
OXONIENSIS.

[4274.]-CUPELLING.-The best and most practicable method of cupelling is to make a thick crucible of calcined bone-dust, using stale beer to make it into a paste and shape it, then bake, and when thoroughly dry, place in a muffle furnace and then put in the metal. The bone dust will absorb all but the gold and silver, which will remain in the cupel in the form of bead. The gold can then be separated from the silver by putting the bead into a parting glass nearly filled with aquafortis, using a sand bath with heat, the gold remaining at the bottom perfectly pure. Pour off the solution (nitrate of silver) and add common salt to precipitate it.-M.R.C.S. (A New Subscriber).

[4275.]-TESTING GOLD.-The only method of testing gold otherwise than applying pure nitric acid to the surface (as far as my knowledge of the subject goes) consists in cupelling" (see answer to No. 4274). The metal should be weighed during each stage of the process.-M.R.C.S. (A New Subscriber).

[4518.] MYROBALANS OR MYROBALONS.Under that name, are imported from India the dried fruit (a drupe) of several species of Terminalia, chiefly T. Bellerica and T. Chebula, which are used by tanners and in calico-printing for producing a black dye.SAMUEL.

[4520.]-PERCH FISHING.-The best time for perch fishing is just coming on, and good sport should be had (that I could ever find) nearer London than, say, Hampfrom now right up to Christmas. There are no fish ton. Fish for them in deep holes, dark corners, under steep banks and near large beds of weeds; as a rule, with a stout top and running tackle, good red worms or big fish are never found in shallow water. Use a rod (for large fish) minnows; hook the minnows through the back under the back fin, in preference to the lip, as the perch seizes the bait crossways; by this method, the hook is at once in his mouth, and you can strike immediately. The " paternoster" is a very killing way to fish for perch, but I would not recommend an amateur to try it as it requires some considerable practice to get into the way of using it.-TERMINAL.

[4520.]-PERCH FISHING.-The season for perch fishing is from February till October, during which long period they bite with various degrees of readiness, at all hours of the day; a little ruffle on the water assists the angler somewhat. For small perch a "general rod" will suffice; a common line with good-sized gut, and a No. 4 or 5 hook baited with lob worm, grub, or caterpillar; a paternoster line, armed with various baits, is useful for an unknown locality; and perch swim and feed at all depths. For large perch, a strong rod line and swivel trace, armed with minnow or gudgeon, is hook is also successful, the latter especially in water usually the most killing bait; spinning by tail and gorge where there are many weeds. Most canals or slowrunning streams afford perch fishing.-VIVIS SPERANDUM.

[4521.]-EXTRACTING HONEY FROM THE COMB. -Cut the combs in a horizontal direction into small pieces and place them in a sieve over an earthen jar. Draining may take two or three days, but the greatest portion and the best quality will be drained off in a few hours. When all that can be got by draining is obtained, the combs may be pressed by hand, but the honey so obtained will be inferior both in quality and colour, as a portion of bee-bread would be pressed through the sieve. If an "Amateur Bee-keeper" wishes to get honey of the finest quality, he must strain the combs from the outside of the hives by themselves, keeping the first drainings separate, as the combs from the centre of the hives are usually darker coloured, and the honey not so good. They should be put to drain in a [4861.]-METHYLATED SPIRIT.-It is no doubt true, warm place near a fire. The remaining combs can be as "A Revenue Officer" says, that persons have been made into wax, which I should be glad to explain, if an fined for disguising methylated spirit and passing it off" Amateur Bee-keeper" desires; but he will find a great as a drinkable alcohol without the naphtha, but notwith- deal of very useful information on all points relating to standing this, methylated spirit may undoubtedly be bee-keeping in No. 3 of "Manuals for the Many,"-S. W. drunk as such by any person who finds the flavour to his liking. As a rule all the tinctures now sold in chemists' shops, are prepared with the methylated spirit, and many of such tinctures are for internal application. If "Shellac" desires, I will give him the address of a chemical factory where tinctures of all kinds are made from methylated spirit.-T. L. H.

[4524.]-STEAM JOINT.-I think if "Schemer" had a joint made like the one I send a sketch of, he would

he hole that is uncovered is open to the gas coming [4376.]-COD-LIVER OIL, to prevent nausea, should Com the inlet, and No. 2 is always open to the outlet be taken floated on a little cold water, in which had with the ipe. Nos. 1 and 3 are connected with the inside and previously been mixed ten to twelve drops of diluted utside chambers, which are thus alternately connected phosphoric acid, which has a tonic effect, and makes with inlet and outlet. There is a cover to the valve box, the oil agree better with the stomach. The chest should o that the gas does not get into the top of the meter, likewise be well rubbed night and morning with equal ind the crank spindle works in a stuffing-box, the same parts of cod-liver oil and whisky, to be well shaken be- find it answer his purpose exactly, although I never fore applied. The whisky causes the oil to strike into tried it myself. 1 is a ball-joint, 2 a common stuffing he Government stamps. They are put there because the lung. To prevent the oil staining the linen a piece box and gland, 3 pipe from the engine, and 4 pipe from Relat he meter cannot be altered to register faster or slower, of oil silk with a bit of flannel next the skin will be rehard (Wxcept by taking the top off and moving the tangent.- quired. My wife has tried the above for the last three the boiler.-J. S. S. months, and am thankful to say has derived much benefit.-H. K. N.

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The two marks at top of meter are

[4159.]-PHOTOGRAPHY.-I would advise "Young Photo" to give "Newman's Diamond Negative Varnish" trial, and I don't think he will give it up. It requires very little heat, dries a clear surface, and never gets backy. I have used it for some time, therefore speak levation, from experience.-JOHN TERRAS.

the cost o

ed. After the

[4200.]-PRECIPITATING COCHINEAL.-The folChemistry," Vol. III.:-" After treating the powdered in

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Davis lowing is taken from W. A. Miller's "Elements of seed," says Mr. P. L. Simmonds, in his "Dictionary of addition to the two pans, "Soda Crystal" will require a

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Trade Products."-BERNARDIN.

[4450.]-BATTERIES.-As "M.R.C.S." desires some thes Sects with ether to remove the fat, the insoluble portion | one else to answer his queries, I will do so, though, I The dis digested with water, and precipitated as a purple lead | lake by plumbic acetate. This must be well washed, think, if he carefully reads our ever-obliging friend "Sigma's" answer,and substitutes the word dear" for solution evaporated to dryness in vacuo over sulphuric" clear," it will be much the same in substance. To acid. The resulting body is of a purple brown colour, very query first, no. Second, the bichromate is the strongest,

upon the cal decomposed by sulphuretted hydrogen, and the filtered

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[4531.]-SODA CRYSTALS.-According to promise, I now beg to give "Soda Crystal" the requisite information respecting the manufacture of this article on a small scale. The soda ash, or, as it is termed, "white ash," from which this article is made, may be purchased from any of the alkali manufacturers in such quantities as he requires, and if there are any in the vicinity in which he resides so much the better as regards his profits. In cistern to serve as a settler. If he has nothing better, let him get a large cask that will contain about 160 gallons, and let him provide this with a tap 3in. or 4in. above the bottom, the use of which will be referred to further on. "S. C." must also fix one of the pans over a fireplace, and the other must be left uncased, so that air may play all round it. In the pan over the fire water must be put in to within 6in. of the top, and brought to

ally coverariable, and soluble in alcohol or water. By adding alum but the Smee keeps in action longest: the length of time a boiling heat, after which the ash must be thrown in in

small quantities until the density reaches 45° Twaddell, or thereabouts. Care must be taken when putting in the ash that it is kept continually stirred, so as to dissolve every particle of it, for unless this is attended to some of it will get into hard cakes, which it is difficult to dissolve. When this density is attained, the liquid is drawn off into the settler, where all the sediment soon falls to the bottom. In large manufacturing establish ments it is customary to throw in a few spadefuls of bleaching powder, which facilitates the deposit of the sediment and causes the crystals to be clearer than they would otherwise be. The clarified liquor is now drawn from the settler by means of the tap at the bottom and conveyed to the pan again. The fire is urged, and the contents of the pan kept in a state of ebullition until the density reaches 54 Twaddell. It is then allowed to cool to about 90 Fahr., when it must be run off into the crystallizing pan, or it may be allowed to crystallize in the same pan, but in this case the crystals will take a longer time before they begin to form, on account of the heat in the surrounding brickwork. Iron rods must be laid across the pan, and just beneath the surface, on purpose to support the crust which forms on the top, and to which a quantity of purer crystals attaches. The crystals will very soon begin to form themselves, and will continue to grow until the density gets too low. When completely crystallized, the liquor, which is termed mother-liquor, is siphoned off, and the crystals allowed to drain, after which they may be cut out with chisels and stored in a dry place ready for sale. The time occupied in the formation of a crop of crystals varies according to the state of the weather: in winter, or very cold weather, it takes about six days, whereas in summer it will require eight or nine days. The quantity of crystals obtained will be above double the weight of ash used. The mother liquor may be used again in making a further quantity instead of fresh water. "S.C." must not expect very large profits from the small quantity that he will be able to produce, but still I have proved by experience that as small a quantity as dewt. of crystals can be made for less than they can be bought from the manufacturers, calculating at the rate per ton. If" S. C." will take particular notice of the quantity of soda ash he uses the first time to bring a certain number of gallons of water to the requisite density, he will have no need to use any of Twaddell's hydrometers at all; to ascertain when the liquor is boiled up to its crystallizing density, viz. 54, let him take a small quantity in a ladle or cup, and blow on it with his mouth, when, if it forms a scum on the surface he may conclude that it is boiled enough. I trust that I have given the information sufficiently clear to be understood by S. C." if not let him ask again for what is deficient.

J. ROSKELL.

Felix Augustus.) Reverse: a woman standing, holding
a branch in her right hand, and a spear in her left.
Inscription: COMES AVG. (Comes Augusti.) Common,
worth 9d. to 1s. The brass one is not a coin at all, but
a common card counter, quite worthless.-HENRY W.
HENFREY, M.N.S., &c.

of the Roman family of Antestia. Obverse: the winged
[4564.)-TWO SILVER COINS.-No. 1 is a denarius
head of the Pallas to the right; X for the value in front;
and C. ANTESTI. behind (Caius Antestius). Reverse:
Castor and Pollux on horseback to the right, with their
lances in rest.
ROMA. This coin is common, worth 24. Coined about
A dog running below. In the exergue
40 years B.C. The second coin is ancient Greek, but the
drawing is very indistinct.-HENRY W. HENFREY, M.N.S.,

&c., &c.

[4573.] METHYLATED SPIRIT.-In common with every other article of commerce methylated spirit varies in quality with the price, or dishonesty of the vendor. The commoner kinds contain considerably more than the regulation quantity of wood naphtha, and again, the wood naphtha itself contains a greater or less amount of tarry matter, according to the purification which it has undergone. The well-known empyreumatic odour of methylated alcohol is due to the presence of tar and other products of destructive distillation.-AN ASSOCIATE OF ROYAL SCHOOL OF MINES.

[4577.) INDUCTION COIL.-The inductive effect of torium" stated, that of the coil is so because it depends a magnet is greatest at its middle, hence, as "Inducupon the magnetism of the core. The partitions do not waste the power as "Operator" supposes, because they are not additions but substitutions. They are sectional or vertical insulators in place of the ordinary horizontal ones. I consider good paper soaked in paraffine better than gutta-percha tissue of the same thickness. As I have several times said I have not had such experience in making induction coils as to justify my going into such details as are asked for, though I have made many of the coils as fitted for medical use, and have described them. I only make instruments for my own experiments, and induction coils are somewhat serious affairs, and have not, as yet taken up much of my attention.-SIGMA.

[4579.] DUTIES OF GAS ENGINEER.-These are very extensive, and vary very much with the size of the works. In any case he has to keep up good discipline. To watch the quality of coal; the perfect state of repair of all the works; to decide upon the degree of heat and duration of carbonisation, &c., all of which can only be acquired by experience based on knowledge. This latter should be a moderate acquaintance with chemistry, and the qualities of materials. In large works the ordinary knowledge of a civil engineer is needed, such as relates to strength of materials and forms, as well as the principles of construction, and a good acquaintance with mechanical drawing. There are many books upon the subof which perhaps Clegg's is the best, Bowditch's are useful, and Hughes is a hush-up of a compilation published in Weales' series: I do not remember the titles, and have no list at hand.-SIGMA.

[4532.]-TELESCOPIC, ETC.-In reply to "H. A. C.," it cannot fairly be considered good work for an 84in. silvered glass reflecting telescope to render the satellites of Jupiter visible in sunshine. One of the satellites, the 3rd, has been seen with only 2in. aperture,ject, 50 minutes before sunset, by Mr. C. Grover. I have very frequently observed the satellites before sunset with a 4in. O. G., and have no doubt that the 3rd could be seen throughout an entire day with 3in. of aperture. Let your correspondent turn his telescope on Andromeda and if he sees the components fairly divided he may be sure that his telescope is a very excellent one.HESPERUS.

[4541.3-EMBROIDERING MACHINE. - The machine which I think will suit "A Braider" and recommend him to see is the "Excelsior," Whight & Mann, 143, Holborn-hill, price from £6 68. It makes the double chain stitch the same as the Grover & Baker, with the advantages of a straight needle and a simpler mechanism. It has no feed, therefore the work can be turned right round with the needle for a pivot. I have had one nine months and am quite satisfied with it. The work though quite strong unpicks readily.-O. E. R.

[4546.]-DIVISION PLATE.-"Wahsrof" evidently has not given much attention to this subject or he

would not recommend such numbers as he does. For example, a man who has a circle of 720 holes (who ever had ?) cannot possibly have any occasion for 360, 144, or 120. The numbers 221 and 209 are the most absurd possible, as one is 11 times 19 and the other 18 times 17, and you cannot obtain twice or three times any of those numbers, as they are all primes, so that you have to pay for boring 430 holes, of which only 60 are of any use at all, the rest not even for "fine rings or flutes." I must confess I cannot understand the lines against which he writes "divide into differences."-J. K. P.

[4546.] DIVISION PLATE.-I have a lathe by Holtzapfiel and one by Buck, the division plate on the former contains the following 360, 192, 144, 120, 112 and 96, that on the latter 240, 180, and 108.-T. W. BOORD.

[4554.]-PENDULUM.-In answer to "Lex "I beg to inform him that it is not the simple lengthening or shortening of the stroke of the pendulum which regulates the clock, but the alteration in the length of the pendulum itself.-F. J. WALKER.

[4556.]-TELEGRAPHY.-In reply to "Mus," I think the band which he describes is to conduct the atmospheric electricity to the ground.-JOHN LEGG. [4556.]-TELEGRAPHY.-In answer to "Mus," he is right in supposing that "A" in the diagram is to prevent the wire slipping off the pole. It is termed a "wire guard," but on all new lines a "hoop guard" is used, that is, a galvanised-iron inch-wide strap, arched over the insulator and fastened both sides. By the way, his diagram is quite wrong, he never saw two wires fastened to one insulator.-TERMINAL.

Chemicus

red chalk, or crocus powder, I believe, but it is done to
[4582.]-GOLD LEAF.-Gold books are rubbed with
prevent the gold leaf adhering to the paper, and not, as
supposes, to prevent its flying about. The
leaf is nearly always laid on the gold cushion before
being applied to the work to be gilt. There are four
methods of lifting the leaf from the cushion. 1st. A
piece of thin beech, called a trindle, is rubbed on the
workman's head, and then applied to lift the gold. 2nd.
A piece of stout paper. 3rd. A gilder's tip. 4th. A
piece of cotton wool.-AB INITIO.

relief if he turns his stockings inside out, and rubs them
[4589.]-TENDER FEET.-I think J. T. Hill will find
well with a piece of soap moistened in water. Boots
with thick soles are not so apt to blister the feet as thin
ones. Blisters also sometimes arise from boots being
much too large. Tight boots also have the same effect

-W.

teeth of the wheel which always drives do not c
cutting much below the pitch line, in fact only even
to clear the shortened teeth of the other who i
not quite understand what "C. C." means by the me
line of his query, as I never knew of any partcar
for the case he proposes, beyond what I hav
-J. K. P.

Saib, the Sultan of Mysore, about the yar
[4597.]-INDIAN COIN.-It was strac
be remembered that Tippoo was sist
inga patam on the 4th of May, 1799. E
copper coins from the Mohammedan
peisah, or pice, also called dudu N
(A.D. 1799). These coins were th interest,
peisah, and the quarter peisah.
are remarkably distinguished by
elephant upon them. If "J. N. D. U.
ward me his coin, I could tell him it Hos
ham House, Brighton.

value.-HENRY W. HENFREY, M.N.S., & Mark

[4599.]-EFFECTS OF CARBONIC ALtaining more than 15 per cent. of carb to animal life; in its natural state it em of carbonic acid in 2,500 parts (by measures. portion than this acts upon the nervous narcotie poison.-T. W. BOORD.

[4599.]-EFFECTS OF CARBONIC ACTRES proportion of carbonic acid is greater this? cent. it acts as a poison.-OXONIENSIS.

[4599.]-EFFECTS OF CARBONIC ACIDing to Professor Huxley, the direct poisonous d carbonic acid have been greatly exaggerated, tra been found that air containing from 15 to 20 pe of this gas may be breathed without produc immediate evil effect, providing the quantity of ca in the air be increased in a like proportion. The periments go to show that the destructive pore carbonic acid depends more on the fact that its pose in air renders the proportion of oxygen to smal thus a species of suffocation or asphyxis is produ together with any poisonous effects the gas may have. the air were confined, as in badly ventilated rooma, carbonic acid would continue to increase and the oxyge to diminish as long as the individual remained, ani air with the corresponding removal of oxygen asphyxia when 10 per cent. of carbonic acid is thus added to the will take place. When a much smaller proportion of pure air, say 4 per cent., is replaced by carbonic acid, headache and languidness are produced, and these often end in fainting.-EXHIBITIONER AF HOTAL COLLEGE OF

SCIENCE.

gold-size instead of the ordinary ins, and apply gold-leaf
[4600.] PRINTING IN GOLD OE BRONZE-Use
or bronze powder when the saeis scently dry. The
material warehouse, as, for example, at 7. Ullmer's, Old
size, &c., may be obtained ready yor ve at any printing
Bailey, E.C.-T. W. BOORD.

[4600]-PRINTING IN GOLD OR BRONZE.-Th
may be easily and cleanly performed by rolling the typ
with gold size instead of the ordinary pristing in
powder is dusted over the paper, and the whole wiped
After the impression is "pulled," gold, silver, or brone
Common printing ink
with a piece of cotton wool.
answers just as well; but in this case, in wiping of the
superfluous metal, care must be taken not to smear the
letters, as the black ink would, of course, show o
paper. Any colour may be printed in the same maner
and particularly those which lose their lustre whe
mixed with varnish.
Thus, ordinary red in
"brought out" much better when it is dusted
vermilion powder afterwards. - SAUL RYMEA.
should moisten his type with size, or some glut
[4600.]-PRINTING IN GOLD.-"Amateur Te
damp, dust it with gold or bronze; when quite dry.
composition, then print, and while the card is
carefully brush off the superfluous metal with cott

wool.-AB INITIO.

[4600.]-PRINTING IN GOLD OR BRONZE"Amateur Typo" should use gold size in place of on taken dust the work over with bronze-procurable fr any artist's colourman-afterwards very lightly clean far too expensive, whilst bronze will answer every the surface with a pad of cotton wool. He will find pose. The operation should be performed in a

room.-H. T. R.

[4590.]-TOWN GARDENING."A Factory Lad" will not succeed in growing geraniums and fuchsias any-nary printing ink, and so soon as the impression where if they are exposed to the fumes of burning gas. Notwithstanding the purification which gas now undergoes there is still too much sulphur in it, and plants of any kind exposed to its effects cannot thrive, and will scarcely live. If " A Factory Lad" will accept my advice he will not attempt to grow anything from seed, but will go to a gardener or a nursery, and buy what he wants just as they are coming into flower, or at any rate when [4601.]-GILDING BOOK EDGES." A. H. asters, and numerous others will bloom almost anywhere been cut, wash with a mixture of one part candy well established. Wallflowers, sweet williams, stocks, should proceed in this fashion:-After the edges a if well grown before removal. If, however, he will try to four of Armenian bole, ground thoroughly seed, let him get Collinsia bicolor, Lupinus nanus, EnsiAdd the white of an egg and some water. The mum Peroffskianum, Nemophila insignis, Virginia stock, must now be thoroughly beaten together, till suf larkspur, convolvulus, candytuft, and some of the other thin to be applied with a brush. Use a c hardy annuals. I have seen these blooming even in brush to apply the fluid, and when nearly dry, London areas, where they get very little light, not to with a wet rag and apply the gold-leaf on a mention sunshine. When the seed comes up leave only cotton wool. Some binders apply gum wate two or three in a pot, so as to give them room to grow. laying on the mixture of bole and sugar; othe don windows. Sunshine is not a necessity, but they and lay on the gold-leaf when nearly dry.-S Geraniums and fuchsias I have seen flourishing in Lon-paint the edges with a solution of isinglasses, should have as much light as possible. The creeping jenny does well to hang down in front and hide the boxes. Above all things give the plants good wholesome mould, such as turfs ent from a meadow, 2in. thick, and crumbled up with a little sand if necessary. Always keep the leaves clean by syringing or watering, as they act as lungs, and town soot and dust soon block up their pores, and so" choke" the plants.-SAUL RYMEA. [4592.]-CHANGE WHEELS.-I think "C. C." had better beg, buy, or borrow Binns' second course, and read therein the chapters on wheel teeth. The scriber for striking the epicycloids is always a portion of a circle of one half the diameter of the smallest wheel of the set, which Willis puts at twelve teeth, and Binus proposes to make fourteen the universal standard for, as it makes anyhow. If the wheel is always to drive the pinion, as a better shaped tooth, the wheels will then interchange the scribing circle requires to be the whole diameter, instead of half the pinion; but as the pinions of clocks are commonly only half the size of those used in other machinery, the result is much the same tooth for the wheels in either case. Where a wheel is always driven it requires no top to the teeth, which may all be turned off down nearly to the pitch line, and consequently the

[4601.] GILDING BOOK EDGES.-Screw the book up as tightly as possible between boards placed b with the edges, scrape the edges perfectly smooth will a steel scraper, burnish with an agate, then colour ove with red bole, or chalk ground in soap, rub inmedisi dry with fine clean paper shavings and burnish ague The size, prepared by well beating up the white of a egg with three times the quantity of water, must the be applied evenly with a large camel's-hair pencil, a the gold laid on with a tip. When dry burnish carefni to avoid rubbing off the gold.-T. W. Boord.

should gild his edges as soon as cut, and if he wishes the [4601.]-GILDING BOOK EDGES.-" A. H. D. the edges with vermilion mixed with glaire, and a little edges to show red under the gold, he should first colou liquor ammonia; when dry moisten the edge with a little

[4560.]-PAINTING CISTERN.-If your cistern is well scraped and dried, a light coat of red lead paint ought to remain good for years.-VIVIS SPERANDUM. [4563.]-BRASS COIN-is & Nuremberg counter; observe the letters RECHP. "Rechenpfenning" or counter; those letters are always sufficient for classing a coin among the German counters. The present bears in clocks, and supposing the pinion to be a lantern, then gold size, and while the edge is damp lay on the gold even the English word "Counter."-BERNARDIN.

[4568.]-COPPER AND BRASS COINS.-The first one is a Roman coin of the Emperor Probus, who reigned from A.D. 276 to A.D. 282. It is of the size called 3rd or small bronze. The obverse bears the crowned bust of the emperor to the right, circumscribed IMP. C. PROBVS. P. F. AVG. (Linperator Caius Probus Pius

(see reply to 4582). When thoroughly dry burnish with a bloodstone burnisher.-AB INITIO.

into a saucepan or melting pot, and cover with water. [4602.]-MELTING GLUE-Break up your cakes of glue Let it stand a few hours to soak; place it on the fire until dissolved; bring it to boiling point, and strain it through a cloth, and it is completed. If found too thick

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[4602.] MELTING GLUE.-Soak a cake of glue from 12 to 24 hours in cold water, then drain off the water, put it (the glue) in the glue pot, fill the outer vessel with boiling water and apply heat. The glue will speedily run into a liquid fit for use. The longer it is soaked the more liquid it will be. Glue improves in quality by frequent melting.-J. W. BOORD.

[4603.]-FISHING.- Mr. Jamieson" will find plenty of bleak and gudgeon in the Lea, either at Rye House, Tottenham, or Temple Mills; but he must remember that gudgeon swima near the bottom and bleak near the surface. A good method of angling for bleak is to have a light fly-rod and line, and a No. 1 hook mounted on a bit of the very finest gut, stained greyish green. About 1 or 2ft. from the hook place a round piece of cork, about as large as a good-sized pea, which will do for a float. Bait with one nice large gentle, and have ready some bran, mixed with sufficient water to cause it to adhere on pressure and yet to crumble up readily when thrown into the water. Choose a likely spot for a swim, which is easily discovered by the bleak rising, throw a handful of bran up stream, and drop the baited hook on the water, letting it float down with the bran till you get a bite. This is considered the best method, but bleak can be taken with anything, only you must fish on the top. They are found in most streams producing dace and roach; and gudgeon are to be caught in nearly every running river in the kingdom. Stone-loach are to be found underneath stones; and the best way to catch them is to wade into the water, remove the large stones, and net or spear them. Thames fishermen always rake the bottom when fishing for gudgeon; this is as good as ground bait, or better.-A. T., Staines.

[4604.]-PICRIC ACID is formed by the action of fuming nitric acid upon many organic substances containing nitrogen, such as silk, indigo, salicin, &c., &c., but more cheaply by treating carbolic acid and its derivatives with nitric acid. It is a bright, yellow crystalline substance, possessing great tinctorial properties. It dissolves in about 90 parts of cold water, to which it imparts a yellow colour, and a bitter taste; it is on account of this latter property that it has been substituted for hops in brewing, although, from what I can glean, more importance has been attached to this means of adulteration than it deserves, for it is not so commonly used as is generally supposed. A test which can readily be applied by persons not conversant with chemical manipulation is to take a skein of white silk, and allow it to remain in the ale under trial for a short time, when, if there be any appreciable amount of picric acid present, the silk will be found to have acquired a yellow tint. Another test is to shake the ale well until a good froth is obtained; this, if the acid be present in any quantity, will have a yellow shade.-AN ASSOCIATE

OF THE ROYAL SCHOOL OF MINES.

[4604.]-PICRIC ACID.-Picric acid or tri-nitrophenic acid, one of the coal-tar dyes, of canary-yellow colour, and very bitter taste. It's tinctorial power is very great, one part distinctly tinging 300,000 parts of water. A simple solution in water is sufficient to dye animal fabrics a fast canary yellow, although it is generally applied with alum and tartar. Its use as a substitute for hops is objectionable, as it is said to yellow the eyes of those who partake of it. It may be easily detected as follows:-Take a sma 1 test tube, say 4in. by ĝin., half fill this with the liquid to be tested; add a small bit of potash or soda, about the size of a grain of wheat; warm this over a gaslight until dissolved; now add a small crystal of green copperas; hold the test tube up to the light, and watch the change of colour; if picric acid be present the liquid becomes a reddish brown, but if not present, it becomes a dirty greenish white.CROW TREES.

as they are arranged to give a current of high tension or
shocks, instead of quantity.-SIGMA.

[4618.]-MANAGEMENT OF BEES.-The best bee-
feeder is a wide-mouthed glass bottle holding about 1
pints. Half fill with syrup and tie a piece of coarse
cloth tightly over the mouth, place a piece of wire
gauze over one of the openings in the board form-
ing the top of the hive, and turn the bottle quickly
upside down placing it at once on the gauze. Last win-
ter my bees consumed about a pint in ten days, as nearly
as I recollect, but they had very little stock honey in
their hive. The bottle, complete, may be had at Neigh-
bour's, Regent-street.-J. W. BOORD.
[4621]-CHLORIDE OF GOLD.-Dissolve the gold
cuttings, which should not be too large, in aqua regia,
this should contain more hydrochloric acid than
nitric; evaporate down on a water bath, when a red deli-
quescent mass of chloride of gold will remain. If a
pale yellow powder be left on taking up with water do
not throw it away, for it is the sparingly soluble proto-
chloride of gold. The readiest way to get rid of this is
to ignite it and re-dissolve the metallic gold thus ob-
tained in some more aqua regia, and proceed as before.
-AN ASSOCIATE OF THE ROYAL SCHOOL OF MINES.

[4621.]-CHLORIDE OF GOLD.-Dissolve the gold
in aqua regia and evaporate to dryness over a water
bath. The residue may then be dissolved in water.-
EXHIBITIONER AT ROYAL COLLEGE OF SCIENCE.

[4621 & 4622.] CHLORIDE OF GOLD AND NITRATE OF SILVER.-Chloride of gold, or more properly ter chloride of gold, is made by dissolving pure gold, one part, in three parts of nitro-muriatic acid (composed of by the assistance of heat, the solution is complete, nitric acid one part, and muriatic acid two parts); when, evaporate until fumes of chlorine are disengaged (to be distinguished by the smell) and set aside to crystallize. To utilize your old solution of silver add a solution of common salt in excess, i.e., until no further precipitate is produced; collect the chloride thus produced on a filter, wash and dry it, then throw it carefully and by small portions into a red hot hessian crucible contain ing twice its weight of fused carbonate of potash with a little borax, waiting until the effervescence ceases each time before adding a fresh quantity; when all is in raise the heat considerably to prevent the silver from adhering in globules to the side of the crucible, and allow the whole to cool slowly. The silver thus obtained may be dissolved in nitric acid and crystals obtained in the usual way. The salts obtained in both the above processes should be re-crystallized twice to insure purity; Cuttings of paper filters, &c., containing silver should be burnt, the ashes treated with nitric acid, and the resulting liquid as above.-J. W. BOORD.

[4622.]-NITRATE OF SILVER.-Do as you say. Evaporate down to dryness; powder it, and mix with some carbonate of soda, as a flux, and a little charcoal powder, and then fuse.-AN ASSOCIATE OF THE ROYAL SCHOOL OF MINES.

[4627.] DISCOLORATION OF LEATHER. In the process of tanning, leather is made to take up tannic and gallic acids; these combine with iron, derived from the metallic surfaces of the press, and form tannate principally, and some gallate of iron, both of them are black, hence the stained leather; in fact black ink is formed. This discoloration may be prevented by not allowing the iron surfaces to come in contact with the wet leather. Would it be feasible to apply a thick cont of paint to the presses and so prevent direct contact between the two?-AN ASSOCIATE OF THE ROYAL SCHOOL OF MINES.

[4627.] DISCOLORATION OF LEATHER.-When the iron-mould comes into contact with the leather, which contains tannin, a combination is formed similar to that which gives its colour to ink. If the moulds and leather were perfectly dry this would not take place. Brass moulds would not be open to the same objection. W. Boord.

[4604.]-PICRIC ACID.-This acid is formed by the action of nitric acid on indigo. Brilliant yellow scales, very bitter and highly poisonous; used in dyeing yellow.-J. its salts are mostly explosive with heat. It throws down a yellow crystalli e precipitate, soluble in water, with caustic potash.-J. W. BooRD.

[4605.]-PROPELLING A VESSEL BY A WINDMILL. -A vessel could not be propelled head to wind by a windmill, for even supposing friction to be put out of the question, and the whole of the power exercised by the wind on the windmill to be utilized by the screw, the result would simply be that the vessel would remain stationary; but as more or less of the power would be lost on account of the friction of the machinery, and as the wind would moreover be acting on the hull and rigging of the ship, the practical result would be that the vessel would go backwards instead of forwards, though not perhaps so readily as if the machinery were not at work.-W.

[4627.] DISCOLORATION OF LEATHER. — "G. A. G." is certain to get his leather discoloured while he uses iron upon damp leather. Cannot he use boxwood or something similar ?-AB INITIO.

[4631.]-LATHE.-TO H. WILLIAMS.-I should say No. 12 gauge-wheels would do very well. The size of screw may be lin., unless it is a very long one, in which case it is desirable, I think, to have a bearing close to where the thread terminates on the left of the gap. Of course the smaller the diameter of screw the less the force required to work it, and that is considerable when you are cutting a screw of high pitch. I may as well take this opportunity of stating my firm opinion, that in this case, as in most others where screws are used for any purpose, except as what Holtzapffel calls the "cement" that binds portions of machinery together, a very great economy of force is obtainable by the use of a high-pitched screw. And for your case one of lin. pitch and lin. diameter, would, I am quite positive, give a most satisfactory result in working. It would be, perhaps, difficult to get cut, and still more to get a nut made for it; and is moreover so at variance with usual practice, that I should not advise you to act on my opinion, however firm it may be, as I have not tried such a screw yet-though I have everything nearly ready for doing so. You might safely have one of in. pitch, with a 4in. threaded screw, cut with a No. 8 screw-tool. I advocate the plan of making the screw in two parts, viz., the plain part at the left-hand of the lathe terminating in a socket, into which either end of the screw may be keyed, a portion of the thread, say an inch at behind the socket comes the extra bearing I propose bove, and then you may safely reduce the diameter of vour screw. I should strongly advise you to send your screw to Wilkinson, No. 42, St. George's-road, London, to be cut, as you will then have it of a true number of hreads to an inch, which is commonly not the case in Lathe screws.-J. K. P.

[4607.]-ORGAN BUILDING.-To make stop diapason speak louder. This can be done-providing the scale will admit-by "cutting-up" the mouths of the pipes higher, as well as by taking out the plugs, which are sometimes put by the builders into the feet to soften the tone by reducing the supply of wind. This requires considerable experience to do; and unless "W. Por ters" is a first-class hand at voicing I should recommend him to take his stop to a regular organ-builder, who will, if the thing is practicable, very soon do what he requires, whereas his own efforts may only render his stop uneven and perfectly unbearable. As regards hardening brass wire for pallet-springs, don't have an inch of it in an organ at all, unless you wish to have a constant source of annoyance in the shape of repairs. Steel and gal vanized iron wire are almost universally used by buildersach end, being turned away for the purpose. for pallet-springs.-H. T. R.

[4611.)-POLISHING VULCANITE.-"G. N. L." can get a perfect surface on his vulcanite by removing the scratches with a smooth waterayr stone (wet), and then giving it a good pumicing at his lathe with fine pumice and stiff brush. After washing the pumice off he can polish it with whiting and soft brush. He must keep turning his work about in different directions, so as not to keep brushing in one direction, for if he does, he will never get a surface.-J. C. P.

[4614.]-ELECTROLYSIS. - This can be easily effected by an electro-magnetic apparatus, if arranged to give a "quantity" current, and in one direction only. The ordinary instruments sold would be totally useless,

Close

[4638.)-SILK WINDING.-The cocoons must be well steeped in a warm soap-lye, and the floss taken off un'i the fibre will run easily: then five or six of the fibres are aken together, passed through a small eyelet, or guide, nd wound upon a large reel. As soon as any cocoon becomes exhausted or runs down to a mere skin, it must e replaced by a fresh one so as to keep the reeled thread uniform in thickness.-CROW TREES.

[4640.]-SOUTH KENSINGTON EXAMINATION PAPERS.-These papers are to be had of Messrs. Chapman & Hall, Piccadilly, London, stitched together in batches of four or five different subjects, price about sd. or 4d.-CROW TREES.

[4641.]-MILL BILLS.-"R. D." can get his bills to stand if he is careful not to heat them beyond a bright cherry-red when drawing down the points. The process requires skill, no chemical being used in the water. Begin by carefully and regularly heating the point to be first drawn, and sledging it down to about one-half more than the intended thickness, tapering it in width so that when drawn by the hand-hammer to the proper thickness it is of equal width throughout, as hammering the edge now will cause the corners to fly. After cutting square, and flatting the point, thrust the bill through the fire and heat well up before attempting to heat the end, turning it round so as not to burn the edges; draw the point into the fire and heat to a brightish red, being careful of the corners. Harden by plunging about 2in. of the If "R. D." accomplishes all this skilfully, being sparing point perpendicularly into a pailful of cold spring-water. of heat, though not of labour, his bills will stand dressing the hardest millstone.-T. A.

[4641.]-MILL BILLS.-"R. D." should use yellow prussiate of potash, and plunge into urine, while red hot. As far as my experience goes, that never fails if the metal be good.-AB INITIO.

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[4646.]-MAGNETO-ELECTRIC MACHINE.-Would some kind brother reader inform me if any experiments can be performed with one of these machines apart from their ordinary medical use,-if so, I should like to know what and how to be performed-so as a number of persons could see it at one time? or if by any means the current of electricity can be made more powerful? Would a coil of wire or helix add to the strength? The answer of some reader will oblige.-ENQUIRER.

[4647.]-PHOTOGRAPHIC.-TO "MUS," OR " OPERATOR."-Will either of the above gentlemen kindly assist me in the following matters ?-1st. By mistake I mixed the nitrate of silver in filtered soft water. Does it matter? If it does, what had I better do? 2nd. In looking on the focus screen, the figures (houses, pigeonhouse, saw-mills) are not only upside down, but reversed (saw-mills on left hand, &c.). I don't think the latter position can be correct. If it is not, how shall I alter it? 3rd. I can get no image on the plate when the developer is poured on. What is the remedy for this? I have taken the ENGLISH MECHANIC regularly for several months, but as I do not see any information applying to my case, I have acted on "Mus's "advice to another correspondent and beg leave to ask for it.-MENDICUS.

[4648.]-TWO COINS.-If any reader of the ENGLISH MECHANIC Would inform me through the medium of your pages the value and other particulars of the two

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coins in my collection of which the above are sketches, they would greatly oblige.-CONSTANS LECTOR.

[4649.]-FRICTIONAL ELECTRICITY.-I have a cylinder electrical machine, the cylinder (length 18in., diameter 8in.) being supported on two brass pillars screwed into a brass table, into which is also screwed the brass spring to which the rubber is attached; and would esteem it a favour if any reader would kindly explain why I can only get a fin. spark from the prime conductor (which is mounted upon a separate glass)?

-PATTY.

[4630.]-FRENCH LANGUAGE.-Would any reader favour me with the name of a first-class book from which an English person might study the above, also the cost and publisher ?-PATTY.

[4651.]-POWER OF WATER-WHEEL.-I shall feel thankful if any of my fellow-readers will kindly assist me with a plain rule to find the horse-power of an overshot water-wheel, diameter 16ft., breadth 4ft. Also, would a penstock of 8ft. or 10ft. above the wheel increase If so, in what ratio ?its power and also its velocity? MILLER.

[4652.]-TONING BATH.-I am often troubled with my toning bath not working well. Would any of your readers oblige me with a good, trustworthy formula, giving good uniform tone? I think "Mus." "Operator," and others can supply me with sound information.JOHN TERRAS.

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[4653.]-SUNDIALS.-One of our friends, "E. L. G. [4131), says sundials can be easily made to show clock time throughout the year, by having two gnomons used alternately for nearly half a year each. He leaves the problem to be solved by your readers. fortunately the problem is beyond my ingenuity, I shall feel obliged if he will favour me with further informa

tion.-SUNDIAL.

As un

[4654.] OCCULTATION OF SATURN. Will "F.R.A.S.," Mr. R. A. Proctor, or some other spondent, kindly explain the following ?-It is stated in the Nautical Almanac that the planet Saturn is occulted by the moon on the evening of the 30th September. The disappearance is predicted to occur at 6h. 4m., and the re-appearance at 7h. 18m. So far this is perfectly clear, but on referring to the " Elements of Occultation," in the same volume, I find that the planet will be in conjunction with the moon at 6h. 12m. on the same date and that at the time of conjunction the planet will be situated 56m. of arc distant from our satellite. How can this be, when at 6h. 12m. the planet will be actually

occulted by the moon ?-HESPERUS.

Loader" recommend fine emery-paper for cleaning gun- quisite to become a C.E., the cost of examine
barrels every time that they get foul? I should imagine-TERMINAL.
that it would wear them much more than tow wrapped
round the cleaning-rod would.-NEEDLEGUN.

[4680.]-BLEACHING CALICO-P
brown calico ?-N2.
spondent can give a few hints on the bat

[4681.]-INSULATION.-What is the la
of solid ebonite to safely insulate the
secondary coil giving 4in. sparks in ubi
the comparative resistance of guts
new insulating material (Dr. Mat.
Field & Co.? On writing to the me
mation on this point, they simp
which I find to be softer than th
contains paraffine. But the above grams
soluble in chloroform, &c., and meltz
to accurately determine. Also, what
wires with to prevent them sccum d
gold when hanging articles in the g
lution (cyanide) attacks gutta-perch & Dest
week, if possible, will greatly oblige..
Mo

[4668.)-THE LATHE.-TO "J. K. P."-I am just
going to have a 4in. centre lathe, with back gear, over-
head, and screw-cutting motion, and do not exactly
know how to get it: whether I must buy it complete of a
maker, or if I could get the castings and have them
corre-planed up, and do all the other part that I can myself,
and put what I cannot do out to a lathe-maker to be
done, such as the leading screw, &c., &c. I have en-
quired of a great many lathe-makers the price of such a
lathe (first-class work, and all the borings hardened
£100, and others gradually lower in price down to £25,
steel), and find that some, such as Evans, say about
which is the lowest estimate I can get. A man in
Compton-street, Clerkenwell, offers to make it for that.
Now, I consider that £25 is a fair price for this kind of
lathe without any chucks, but from what I have heard
the higher-priced makers say, I shall not get such a
lathe as I expect for that money. The mandrel will be
iron, case-hardened, and all the borings of the same
[4682.]-TONING BATH.-Will
material, which would never suit me, as I want this parple tint? I cannot find it in back o
as to give me his formula for toning
lathe to last me a life-time, if used with care, as an ama-only taken it a few months.-PHOTOGRAFE
teur would use a lathe; besides I have not got £70 or
£80 to lay out, and it would take me years to save so
much, and I want the lathe with as little delay as possible.
If, on the other hand, I can get the castings, and have
them planed up, for about £6 or £7 (the lathe-makers
estimate them ready planed at from £10 to £4 10s.) I
ought to get a very good set of castings to work upon,
and I think that as I could get through a great deal of
the work myself, get the long leading screw cut by a
lathe-maker, also the slide-rest screws, and have the
pulley divided, &c., &c. (I could fit them in their places
myself), it would reduce the cost very considerably-as
my time is my own, and, therefore, should not be
reckoned in the expense. I have a very good 6in. lathe,
3ft. Gin. bed, with slide-rest, face-plate, and chucks,
and I know how to use it perhaps as well as the general
run of workmen. Could I on this lathe with my experi-
ence, make an attempt with any chance of success to
make the kind of lathe I have endeavoured to describe
in this letter, or, at least, the greater part of it? Will
"J. K. P." kindly say what I had better do under these
circumstances?-TOMETER.

[4655.]-MANGANESE BATTERY.-I have seen Mr. Stone's reply to "M. D." in the last number, regarding the manganese battery, and I am very glad to hear they answer so well. I wish I could say that two cells I use for bell-ringing, had gone untouched for as long a period. The fact is that in my case the connections of the battery corrode, so that I am obliged at least once a fortnight to disconnect, and file binding screws, &c., until quite bright. This is the only trouble I have with the battery, and surely if it will go in one case months without any attention, it will in another. Perhaps Mr. Stone will give me a hint or two on the subject,especially as to some less rough process of cleaning the connections, which at the rate I file them will soon be worn out.-E. H. B. [4658]-GOLD COIN.-Will Mr. Henfrey or some numismatic friend kindly inform what the gold coin is,

and the value, of which I send the exact size and copy? Plain on one side. Weight 2 dwt. 23 grs.-HENRY HOAD.

[4657.] KNOT-STITCH SEWING-MACHINE.Would "Practical Hand," or some other brother reader, kindly answer the following? I want to make a knottedstitch sewing-machine, but do not quite understand how to make the looper, nor yet the length of stroke the needle should travel.-J. S. S.

[4658.]-CLEANING GILT FRAMES.-I should be glad to know the best way to clean the gilt frame of a chimney glass. As it is not of recent (cheap) manufacture, I think the gilt will bear operating upon. The gilt is not damaged by accident, but is of a smoky appear. ance, and being highly ornamental will cost too much to regild.-W. E. M.

[4659.]-TURNING HARMONIUM INTO AN AMERICAN ORGAN.-Could Mr. E. H. Jones (who wrote relating to American organs) tell me if I could make or alter an harmonium into an American organ ?-J. W. [4660.]-WELDING FORKS.-Would some reader be so good as to state the process of welding cast-steel, such as the prongs of forks, &c ?-J. W.

[4661.]-CATERPILLAR.-Will some reader of the ENGLISH MECHANIC inform me what is the name of this caterpillar? It has a broad white stripe down the back; a horn on the third segment, black; broad black stripe down the sides, which is marked dimly with orange; head and claspers black.-J. HAMPTON.

[4662.]-COIL.-I have made an induction coil with 1b. No. 16 primary wire, and 1lb. No. 35 secondary wire, gin. long. How much battery power can I use with safety, and how much spark ought I to get without condenser? How long a spark can I expect from a single pint bichromate battery ?-TOMETER.

[4663.]-BRAKE PIECE.-Can any one favour me with a description of a brake piece that reverses the current of electricity suitable for a coil?-TOMETER.

[4664.]-PRESSURE OF WATER.-Can any reader of the ENGLISH MECHANIC tell me if there is any difference in the pressure of water at the bottom of two pipes, both 12ft. high? One is 4in. diameter the whole length; both are vertical; the other 8in. diameter for Sft. of its length, the bottom 4ft., are 4in. diameter. Is there any difference at the bottom of the two pipes in pressure per square inch ?-HOLBECK.

[4665.]-PROBLEM.-Would any reader give me a solution of the following problem, taken from the first B.A. Algebra paper, London University? a. "An express train which ought to travel at uniform speed, after being an hour in motion, was delayed half an hour by an accident; after which it proceeded at three-fourths of its original rate of speed, and in consequence arrived at the end of its journey 1h. 50m. behind time. Had the accident occurred (and the same delay and subsequent retardation taken place) after the train had been an hour and a half in motion, the train would have been 1h. 40m. behind time. Find the length of the line. B. Supposing the above question were varied in the latter part of it by your being informed that had the accident occurred when the train had gone half-way, it would have arrived 1h. 20m behind time;' would that information have been incorrect?" Would it have enabled you to determine the length of the line."

BEVERLEY.

[4666.]-LIQUID BONE MANURE.-I shall be obliged if some of our correspondents can tell me how to dissolve bones, so as to make a liquid bone manure which may be used without injury to plants ?-S. W. [4667.]-CLEANING GUN-BARRELS.-Does "Muzzle

[4669.]-OXYHYDROGEN MICROSCOPE.-Can I use
my achromatic microscope lenses (lin. and 2in.) with an
oxyhydrogen lantern, 8in. condenser, for showing
microscopic objects on a screen? A description of the
mounting required would oblige, if possible.-E. H.
JONES.

[4670.]-SATURN.-Will any subscriber kindly in-
form me what part of the heavens to look to to find
Saturn, and the same for Jupiter, about from eight till
ten in the night?
they will be in about the time your reply will appear.
Please to name the constellations
I looked for Saturn for weeks, but not knowing in what
part to look I have not succeeded in finding it.-YOUNG
AMATEUR.

[See "Astronomical Notes," by "F.R.A.S.," in this
number.]

[4671.]-ICEBERGS.-Can you or any of your readers
say why icebergs were met this year (1870) on the banks
of Newfoundland in March?
Baffin's Bay before the sun was seen there. Could they
They must have left
have been detached by an earthquake ?-C. J. R.

tioned kite to be properly balanced and inclined in a
[4672.]-KITE.-Suppose a large and well-propor-
favourable wind, being free from all direct attachment
with the earth, and also the common appendages, would
it mount, and if necessary, on a change of inclination,
the aforesaid counterbalance being dependent from a
make progression against the said wind by the virtue of
proper position to some distance beneath, and the in-
clination being rigid? A speedy reply will much oblige.

-W. J.

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86

[4883.]-VALVE FACINGS OF CYLIN J. C. Molton or any other obliging subice if the valve facings of model cylinders 23 whether they are put or brazed on after its if cast on how is the cylinder finished of? I put anything in my crucible (brass) to ca free in casting, and how to avoid the scenes going in with it, as it chokes up the mould moulds require to be heated? Thanks to Jun his last instruction on cylinders.-AMATI FOUNDER.

[4684.]-TYPE.-Would any reader be kind m inform me whether there is any decisive test tinguish "pirated" from genuine "fices in types whether, if in equal quality of metal, the former serviceable to the printer ?-COUNTRY PRISTER. [4685.]-GILDING ELECTRO-Will some pract electrician give me some known to the trade as solid depositing-i.. mandis information upon whate turing solid articles by depositing gold in the way the copper is deposited? Is the solution worked warm o cold? What battery power is used, arranged for gasntity or intensity? What is the right proportion of the areas exposed of the anode and the cathode? What is the best surface to deposit upon? I believe there must be a large quantity of gold in the solation.-W. H. COFFIN.

[4686.]-INSULATION. TO INDUCTORIUM.”—I wish to ask "Inductorium," who describes a mode of making a coil on page 472, No. 175, if he finds the inse lation between the primary and secondary colle cient? In coils of the ordinary construction only a small part of the secondary circuit approach the primary, being the layer next to the reel. In the vertical mode the two extremities of the secondary coil are sepa rated from the primary by only the thickness of the that thickness plus the resistance of the primary be reel, and from communicating with each other by re tween the two points. In his case the terminals are thickness of the reel, and one of the rings plus the leng sulated from each other by their silk covering twice th of the primary with its cotton covering. This am certainly being not equal to fin. of the same. Is i to only in. solid ebonite, the rest of the res ebonite enough insulation between the terminals d wire giving 3in. and 4in. sparks in air? For his sa certainly hope so.-W. H. COFFIN.

[4687.] PANCREATINE" AND "PANCREAT EMULSION."-The above preparations are exceless cod-liver oil, but to buy them comes expensive. Le medies for indigestion, and are very useful for takia reader would inform me how I could prepare sa should feel greatly obliged.-H. H.

[4688.)-SEPARATING BEESWAX FROM RE &c.-I should feel greatly obliged if any reader con form me how to separate beeswax from resin and foot oil, with which it has been mixed?-CABINET-MAS [4689.]-PEDOMETERS.-Would any brother give me a description of the action of the pedome AN ENQUIRER.

any kind reader will describe the Indian copper coin, the balance? What kind of bow am I to use-it

of which I forward sketch.-COLLECTOR.

circle,draw a chord which will be cut by the circumference
[4674.]-PROBLEMS.-a, through a point given in a
in extreme and mean ratio at the given point. b, same
problem, an angle being substituted for the circle.-X. Y.
which I keep roach, gudgeons, and minnows.
[4675.]-POND FOR GOLD-FISH.-I have a pond in
I am
about to put gold-fish in it. Shall I be able to keep them
alive all winter, or must they have protection? If so,
what way should I proceed to afford it them? The
pond is fed by a spring-water pipe, and is about 20 yards
square, and 6ft. deep.-VIVIS SPERANDUM.

[4676.]-NITRATE OF SILVER.-I have a quantity of
nitrate of silver precipitate, thrown down with salt from
photographic slops. Would some reader kindly tell me
how to re-dissolve it, so as to be perfectly neutral and
fit for either bath or exciting paper ?-PADDY.
[4677.]-WATER POWER.-Would any brother reader
fifteen feet through an inch pipe, if applied to a turbine
inform me what power I could get from a fall of water
And what size, &c., of a turbine would do?
Also what kind of a turbine would be best?-A REGULAR
SUBSCRIBER.

wheel?

[4678.]-BOURNE ON THE STEAM ENGINE.-I am about to purchase a work on the steam engine. Is there a better work on the subject than Bourne's? If there is would one of your readers tell me the price, publisher, &c. ?-THOS. WATSON.

[4679.]-CIVIL ENGINEERS' EXAMINATIONS.Would some kind correspondent give me a little information about the Institute of Civil Engineers? What is necessary to become a member? and what is re

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[4690.]-HOROLOGICAL.-Will some of our b logical friends who are adepts at the use of the give me some practical instructions how I am ceed in turning down the collet of a verge orig strength, and string-also what kind of grav speed to suit best; aud, above all, whether i use; size of cutting angle it must have, positi hand in using, length of stroke for the bow, cut with the work revolving to the graver the graver? I find in practice that I cannot progress when I attempt to cut the work re its upper surface towards the graver. All do appears to be a mere scrape. But in the ran st when the under surface of the work revalve k the graver I make better progress. Where is the fault, is it in the bow, the grave, In fact I te quently taken hold enough to break the verge to fis self? My friends may judge for themselves of progress when I tell them that it will take me of hard cutting, scraping, and scratching to turnd the collet of a polished verge, previous to punis the balance when an adept could do the same wars half an hour. I also wish to know how the pivots pinions are got to the required size. Are they tu with the graver or filed down! I have frequently pu new pinions, but always file them down to the requ size in the turns, by placing the end of the pinion notch at the end of the centre of the turns with end of the rest as a guard, to keep the edge of the from running away from the shoulder of the pivot. it the proper way ?-SCRAPE.

nus" give me the power of an engine whose cylinder i [4691.]-POWER OF ENGINE.-Would "Vertue 2in. in the bore and of 4in. stroke, by the rule he mais tains in your last week's issue (4474), and what will b the necessary thickness of builer plate, and pressure d steam to work at to attain the power of one horse?R. W.

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