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first of the hydrocarbon gases, and subsequently of the chlorine gas, are even more disagreeable to the analyst than the nitrous fumes evolved during the nitrohydrochloric acid process. 3rd. it is not so rapid the nitrohydrochloric acid process. 4th. The results do not exhibit a greater accuracy than is obtainable by solution of the iron in nitrohydrochloric Mr. Hamilton, in his article, says: "I have analysed several specimens of pig-iron according to the solution in the nitrochloric acid method, with all due precautions, which, although exceedingly important, are often omitted in explanations of the process." As Mr. Hamilton has also omitted to mention the precautions necessary to observe in carrying out the nitrohydrochloric acid process, I will describe in detail the manner in which I estimate sulphur in iron and steel by that method, having always found the results trustworthy and accurate.

A weighed quantity (about 3 grammes) of iron is placed in a beaker of about 800 cubic centimetres' capacity, and having a clock-glass cover. 20 cubic centimetres of strong hydrochloric acid are mixed with 10 cubic centimetres of strong nitric acid in a small beaker, and gently heated until the acid liquid assumes a slightly yellowish tint. The acid is then poured, little at a time, into the beaker containing the iron, the glass cover being moved just sufficient to allow of the acid being poured into the beaker. A very strong reaction takes place, and great heat is generated; but the capacity of the beaker, and the large cooling surface presented by it prevents any loss by effervescence. The solution of the iron is thus effected in two or three minutes, and the whole of the sulphur is oxidised to sulphuric acid. The sides of the beaker and the clock-glass cover are now rinsed by means of the wash-bottle, and the liquid is evaporated nearly to dryness over the water-bath, or on the steam-chest, to remove excess of acid. A few drops of hydrochloric acid are poured on to the residue when nearly dry, and water is added, a gentle heat being applied to hasten the solution. The liquid is then filtered in the ordinary way, the filter paper washed with cold water, and the filtrate diluted to about 100 or 150 cubic centimetres. A solution of chloride of barium is added in excess to the filtrate, which is allowed to stand in a warm place for several hours. The precipitate soon makes its appearance, and settles down at the bottom of the beaker, leaving the liquid above it quite clear. The liquid is now filtered, and the precipitated sulphate of barium collected on the filter paper; but it is important to note that the filter paper must not be washed with hot water until the whole of the yellow solution of iron has been removed from it by washing with cold water. I mention this particularly, as Mr. Hamilton in his paper says:-"After filtering and washing it well with boiling water, it is seldom, if ever, possible to render it white, which is objectionable to a careful chemist." This statement and the context would lead one to infer that washing with boiling water is necessary to render the precipitate white, whereas the reverse is the case. After the liquid has passed through the filter paper, the latter should be washed with cold water, and if a trace of yellow colour remains in any part of the paper, a few drops of hydrochloric acid added, and further washing with cold water, will entirely remove it; the washing may then be continued with hot water. With proper care, and the observance of those precautions. the precipitate, when dried, ignited, and weighed, will be obtained perfectly white. On the other hand, if the paper be washed at first with boiling water, it will assume a brown coloration, owing to the precipitation of oxide of iron, the complete removal of which from the paper is very difficult.

In estimating the sulphur in steel and wrought iron, it is advisable to use a larger quantity, say 5 grammes of the metal and 50 cubic centimetres of the mixed acids. The weighings must be made on a balance capable of weighing accurately to the tenth part of a milligramme. I use one of Ladd and Oertling's balances, furnished with supports for the scale pans, and having agate plane and knife edges.

The acids sometimes contain a trace of sulphurous acid, waich during the solution of the iron becomes oxidised to sulphuric acid. Before making any estimation of sulphate in iron, it is therefore necessary to estimate the weight of sulphate of barium obtained from a given volume of the mixed acids. Thus, if 60 cubic centimetres be the volume experimented on, and four milligrammes of sulphate of barium be obtained, then in a determination of sulphur in iron, using 3 grammes of iron and 30 cubic centimetres of acid, a deduction of two milligrammes from the sulphate of barium obtained will be necessary on account of the impurity in the acid. The following are some of the results which I have obtained by solution in nitrohydrochloric acid. In my opinion they are sufficient evidence of the accuracy of the method, and the difference between the results of the first and second analyses is in each case less than the differences obtained by Mr. Hamilton in his experiments:

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THE SOPER RIFLE.

The one I am

SIR,-Some readers may recollect a description of a rifle invented by Mr. Soper, in Vol. VII., p. 339. Certainly our inventor must be credited with no small amount of ingenuity and perseverance in being able to produce to the world another and a far superior arm than the previous one. The former was rejected by the Small- Arms Committee for its seeming-I say seeming intentionally complication. about to describe is simplicity itself. By a very unfortunate decision, however, of the Government, the gun of which I give diagrams, has not been considered in the competition, as it could not by any possible means be got ready by the day stated as the last when new inventions would be received. There. fore, for the moment, it has the cold shoulder, but if rival inventors, experienced mechanicians, the most eminent engineers of England, France, Germany, and the United States, give, as they have given, their opinion that this rew gun is the best in the world, how long will it be before Government is compelled to admit it in competition with others? The requirements of a breech-loader are simplicity, strength, and certainty of action, We will consider for a moment how far the gun we are discussing answers to these requirements. Its constituent parts are reduced to a minimum, and therefore, of necessity we get simplicity. "The cocking of the piece, the opening of the breech, and the extracting of the empty cartridge shells are simultaneously effected by one movement of the hand without changing the position of the piece. The breach is closed by a block which is hinged or pivotted at one side of the rear of the barrel, and which is raised and turned laterally on its pivot to open the breech" (specification). Fig 1, A, the breechblock is perforated to allow the insertion of the striker,

FIG.L

Fig. 1, B, by means of which the blow of the hammer
is transmitted to the cartridge.
above-mentioned are caused by the motive power
The movements
being applied to a lever, Fig. 1. D, mounted on the
right side, moving in a circular direction, but only to
plain the marvellous rapidity with which this gun has
the extent of 55°. The ease of the operation will ex-
been fired. At the late Basingstoke Exhibition no less
minute, work which has never yet been equalled. The
than 60 rounds were fired by Mr. Warwick in one
only springs used in the mechanism are the ordinary

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ber, and still when tried, of course before being cleaned, its action was perfect.

The whole mechanism will however be understood have given references to the peculiar parts only; the much better by reference to the following diagrams. I others, as the barrel, cock, &c., are similar to the ordinary rifle.

Fig. 1 represents a side view; Fig. 2 a longitudinal section; Figs. 3 and 4 are end views, with the breechblock raised and closed respectively; Fig. 5 shows the breech block.

the extractor, E. Fig. 2. By the diagram it will be It may be necessary to say a few words regarding seen the end of the extractor is raised, and it is this part which catches the rim of the cartridge. The extractor is moved by means of a lever, and by a peculiar formation of the hammer it is started back with a slow motion, which is gradually accelerated, and finished with a jerk. By this peculiar motion great force may be exerted upon the cartridge shell in starting it from the cartridge, or some other means, has caused to stick the barrel, which is necessary when the explosion of tightly in the barrel. One screw secures the whole. The stock of the gun is in one, and, therefore, very strong.

C. H. W. B.

P.S.-Just at the moment of writing I hear another trial is to be made as regards rapidity of firing, which I hope to witness, and if more than 60 rounds per minute are fired, the Editor shall be duly informed.

INGREDIENTS FOR GOOD PAINT. him the ingredients necessary to form a good paint are SIR,-In answer to " Surveyor," (qy. 2500), I may tell as follows:

Ist. A genuine well gound material or paint proper for the body.

2nd. Siccaline or boiled linseed oil, as a vehicle for the convenient retention of the paint itself.

3rd. "Patent" or other dryers, to assist the paint in hardening and drying.

4th. Turpentine or petroleum spirit, to give sufficient fluidity to the above mixture, so that it will work readily under the brush. It also acts as a dryer.

The proportions of the above vary, (1) according to the nature of the paint, (2) according to the kind of surface to be covered, and (3) according to the weather.

Speaking generally, and taking best ground white lead as an example, lcwt. lead, 6gal. boiled oil, 21lb. patent dryers, and 1gal turpentine, would make a paint suitable for second coat work. For priming or first coat, say Igal. oil less, 1gal. turpentine more; this would cause the work to dry "dead" or flat, as is required. oak varnish. Unless you buy from a good house you Pale oak varnish is the best for grained woodwork. If the work is exposed to the weather, ask for outside will get varnish made with softer and cheaper guins; this is only fit for inside work.

adulteration) is unmistakably apparent, or you have pure paint by you to serve as a standard. In this latter You cannot well detect adulterated paints unless the example, you may detect adulteration in this way: Take, say, 50 parts lead to 1 part ground Prussian blue case, and taking ground white lead again as an or vegetable black, mix together with a given quantity of oil and turpentine, and observe the shade of blue or grey. Proceed in the same manner with the sample to be tested. If this latter test gives you a darker blue or grey than the former, you may be sure that the latter is the most adulterated. By repeating the tests and diminishing the quantities of lead in the first sample, you may make both shades coincide. Note then the difference in the number of parts of lead to the one part of blue or black, and that will be your estimate as to the superiority of one sample over the other. This method may be adopted with most colours. The writer makes an oxide of iron paint that will stand this test favourably against any other he meets with. It is the method he adopts with every sample that comes within his reach, and by it he can test each maker's assertions with tolerable accuracy.

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If

As to the last clause of the inquiry, I should think petroleum or other oils would certainly spoil any paint. Petroleum spirit, or mineral turpentine, as it is sometimes called, will answer very well for conmon outdoor purposes, but at the present price of good turpentine there is very little saving in the use of petroleum spirit. Consumers usually buy paint in the ground or stiff state, and thin it themselves. bought ready for use (a mode the writer would not generally recommend), the smell of it would determine whether petroleum spirit, or spirits of turpentine, had been used. If "Surveyor' will insert his address in the advertise ment columns, I shall he happy to forward him further details. Being in the trade I do not wish further to speak of this subject, as it would make an advertisement of this reply. LLAH.

WROUGHT IRON AND STEEL.

1st Analysis. 2nd Analysis. Diffrnce 0.004 0-023 0-008 0.002

11. Percentage of sulphur 0014

12.

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THE ORGAN.-SOUNDBOARD, OR BELLOWS

mainspring taken from an Enfield rifle, and a flat of the utmost importance, the gun has many times trigger spring. Regarding strength, which is properly been fired with a charge of 200 grains of powder and SIR,-Having made the acquaintance of the ENGLISH 530 grains of lead. Lastly, respecting certainty of MECHANIC Some three months ago, being introduced action, so simple and so certain is it that misfires are to him by a friend who referred me to one of his unknown in the vocabulary of its inventor. The articles in elucidation of some mechanical contrivances ordinary sand clogging has been tried without effect, in which we were mutually interested, I need scarcely the base of the cartridge has been sawn asunder, but say that I have derived much pleasure in availing mystill no failure, it has been left for a fortnight under self of a copy of his weekly visits ever since. I have water, and during the next two weeks left out in the felt much gratified in the perusal of his pages geneopen air, recollect this was done during foggy Novem- rally, and more particularly of late by an article on

organ pipe construction, by," An Adept," whose very
simple, clear, and minute instructions gave me en-
couragement to proceed at once in the construction of
an instrument which, for a long period, I have been
very anxious to commence. I have followed his instruc-
tions in making several experimental pipes (and very
satisfactorily, as open ones), but, unfortunately, like
another of your inquirers, am totally at a loss how to
construct stopped pipes; and, taking a hint from
Adept's" reply to Inquirer," on page 609. No. 258,
I had made up my mind to shelve the pipe operations
for the present, and proceed with soundboard, or bel-
lows. But here again I find myself in a fix; for, not
knowing the scale or relative sizes of the pipes, I con-
not set out my soundboard: and again, as I wish the
bellows to be just as large as my soundboard and wind-
chest will conveniently admit, I am consequently
brought to a stand. I am desirous that the instrument
should comprise-1, stopped diapason, CC to F in alt.
or G (medium scale), wood; 2, principal; 3, fifteenth;
and 4, trumpet metal. And to this end I should esteem
as a particular favour, answers to the following
the ENGLISH
queries:-1. In what number of
MECHANIC can I find "Adept's" wind-chest and
soundboard instructions? 2. Would soundboard 4ft.
Gin. by 2ft. be sufficiently large (placing the largest
octave of pipes in front and at sides)? 3. What should
be the sizes of blocks and thickness of stuff for the dia-
pason CC to For G?

SIMPLEX.

I

WOOD PIPES VERSUS ORGAN METAL PIPES.
B.,"-Glad to find the
DEAR "HARMONIOUS
"gout" has not suppressed your defiant crow.
always hoped wood pipes would come to the fore.
"Adept" must be convinced by this time that metal is
not a sine qua non for an organ. His communications,
as original experiments, are of the highest value, and
I hope he will arrive at speedy convalescence, and be
There must be men capa-
allowed to complete them.
ble of doing this work, and some don't care much for
the trammels of the "practical organ builders." I
even think the tones of the American organ may be
rivalled in delicious wood, and I like to hear the tone
We
and smell the fragrance of the goodly cedar.
can judge of good tone without the aid of the organ
builders, just as we may pronounce upon a vintage of
the "real thing" without the intervention of the
licensed victualler. After all" Adept" has done and
said, the difficulty ought to vanish.

HENRY USSHER, B.A., M.B., Surgeon.

EXTRACTS FROM CORRESPONDENCE.

AMATEUR FARMING. -"A Country Vet." writes:-"Seeing a paragraph in your valuable journal whether it would not be advisable to give a column to questions and answers respecting the breeding, keeping, and rearing of horses, &c. I think myself it would be a good idea; but would it not be advisable to add to the abovementioned list that of dogs and poultry, especially as dog and poultry shows are becoming so extremely fashionable; and a few hints occasionally on the different diseases in the said animals would not be amiss. I shall be only too happy at any time in my humble position to render anything towards its advancement."

REPLIES TO QUERIES.

[1935.]-EQUATION.

x + y + z = a + b + c

bx + cy + az ex + ay ay + bz = a2 + D2 + c2
this problem has been duly solved. I beg to add a
few observations which might extend its utility: 1
remark that these equations solve the problem: a
circle being inscribed in a triangle, the sides of which
are 2a, 25, 2c, to find the segments x, y, z, formed on
the sides by the circle, the relations between these
segments are expressed by the given equations.-
GREGORY.

[2007]-TEMPERING DRILLS.-"S. T." is obliged
for the loop hole J. B." has so confiderately left
him to leap through, but is not disposed to take the
leap, or make use of the printer's shoulders, as his
Tempering,
way out of the suggested difficulty.
be it that of a drill, or anything else, is the art
of bringing the metal to a certain condition by
the application of heat, and by sudden cooling
causing it to retain such characteristics as are thus
developed. The condition of the metal is known by
a superficial oxidation producing the colours before
named; this may be effected in two ways, by harden-
ing and letting down the temper, or by softening,
and then raising it. The both systems are adopted,
the preference being given to the latter, especially
for new tools, as all the finish of surface can be
better obtained in the soft condition of the metal,
which finish is uninterfered with by the process ad-
vocated, that of laying it on a lump of iron heated
to a sufficiently strong heat in the forge or other fire.
The desired temper may be thus secured with the
greatest facility and exactitude, as the clean bright
metal shows the degrees of oxidation from the
blue upwards most distinctly, which oxidation can
be arrested at will. Cleanliness-i.e., brightness
a sine qua non. Smoke, scale,
of surface, is
or other obliterative media, prevent the manipulator
satisfactorily judging of the stages of the process.
The criti-
and failure is frequently the result.
cism of "J. B." had escaped my notice, or I
should have replied in the next issue.-S. T.
[2223.]-WATER POWER. In my reply to
"G. P.," 2323, there is an error in the number
of cubic feet. G. P." stated 200 and not "203" cubic
feet, and at the former I calculated his available
power for a turbine. I am the more desirous to be
accurate, because the "astounding machine" (I can
call it no other) of Mr. J. C. Shewan (which imme-
diately follows my own reply), upsets all practice of
hydraulic engineering. All I can say is, that if Mr.
Shewan can produce a machine as given in his
reply, I, as an engineer in good practice, can make
his fortune. His statement that pressure is no ob-
ject," I do not understand; but let that pass.-
SENEX.

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[2234.]-COLOURED OBJECT GLASS.-SOLOMON'S TELESCOPE.-Whether this is your printer's error or mine, I certainly did not intend to write such nonsense; of course it is the eye-glass I refer to. I may here mention, that to each of the day eye-pieces I have pancratic tubes made, which vastly increases their power, both for earth and sky. By merely pull ing out this tube, a change can at once be made, from an viewing the sun or moon in their entirety, to inspection of a highly-magnified portion of their BLUE MAHOE WOOD.-"Joe" surfaces.-AMATEUR. says:-"I enclose you a splint of the so-much-praised wood for our humerous friend, The H. Blacksmith.' It looks to me very like mahogany in texture. The price I was asked for a rod of it was about 75 per cent. over what I can procure first-class fishing-rods for in hickory, lance, or greenheart. Will the H. B.' kindly favour me with length and weight of his rods without reel or bag? I might be of service to him if he is in the market for fly rods. I have given up bait fishing."

ELECTRICAL PSYCHOLOGY.-"B. Q." writes:"T. D. Workington says that a positive person can control the will of one who is negative. Now, Sir, I once proposed to a young lady, and was very positive, and found her equally negative; and, notwithstanding, utterly failed to control her will! T. D.' also says that Dr. Dods' showed the sighing lover how to choose a congenial partner for life. The sighing lover,' I suppose, was like the Irishman of the Irish tales, who first fell in love, and then began to consider who he should be in love with! On re-reading T. D.'s letter, I find I have made a slight mistake. He says that the positive person either paralyses' or causes motion' in the negative individual. I did both in my own affecting case. The young lady was first paralysed with astonishment, and then vanished with truly electrical rapidity!"

[2270.]-MOTION

OF WATER. I refer to "Q.Q. R.'s" answer, April 15th, who states that 929 cubic feet per hour, or nearly 15.5 cubic feet per minute, would pass the orifice; but Mirabile Dictu," "Anthony" (April 22) states that 25-7 cubic feet would be discharged! (The latter's calculation by his own figures is wrong also).-SENEX.

[2280.]-CHINA GRASS

SEED.-The seed

of Urtica nivea, of which China grass is a variety, is quoted 5 francs a loth, in the catalogue of MM. Haage and Schmitz, seedsmen, at Erfurth, Prussia, correspondents, I think, of the great London seedsmen.-BERNARDIN.

[2286]-GENEVA CYLINDER. This is bought, as shown in Fig. 1. In selecting, the measurement is taken from the height of the lip or pallet E (I, Fig. 1). If there is a very slight difference it is of no importance, as it will only make the part A a little thicker or thinner. Further on will be shown how to get the height when there are no broken pieces to guide. The diameter is taken by placing a tooth of the 'scape wheel inside the cylinder, and then the cylinder between two of the teeth; when the play the tooth bas inside the cylinder, and the cylinder between the two teeth, ought to be equal, taking care not to put them too far into each other, or else the measurement will THE SPHERICAL FORM OF THE EARTH.-Z. be false, but just inside the roundings of the lips. It M. T. Tydeman says:-"There is one argument in is best tried (and a second measurement is usual) in a support of the spherical form of the earth, of an depthing tool, increasing the depth till the tooth falls fairly outside and inside, and fails to turn the cylinder. eminently practical character that I have never yet Proceeding to turn it in, the broken piece is placed at seen insisted on, but have repeatedly put to the test from the cliffs and shores. If looking towards the sen 2, Fig. 1, so that the end of its pivot is level with the on a clear day, a perfectly straight edge be held lower edge of the lip E, when the corresponding part of the old piece will show how much to shorten the some distance from the eye, and then be arbor D. Remember always in shortening the arbors gently lowered down so as just to graze the horizon to allow for the point to be flattened in finishing the (where the sea and sky appear to meet), it will be pivots, and a slight wear in the process of turning in; readily perceived that the waterline is not straight, and taking as much into account in every measurebut convex, and that the rule and the sea, if the former is held perfectly level and steady, first touch ment. Place the part A (3 Fig. 1) on the point of the n the centre of the straight edge. This, I think, is shortened arbor, and the end of the pivot will show loccular demonstration, and is almost as good a proof how much to turn away for the shoulder the balance is to rest on. 4. Fig. 1 shows how to proceed with of the earth's rotundity as its shadow on the moon. the lower position. Before rivetting on the balance, USEFUL WORK.-" Bernardin" writes: "To my the point marked on its rim ought to be in a position brother readers who may understand German, I e- to correspond with the centre one of the three marked commend the following work (printed in Latin type) on the plate, when the wheel is acting in the cylinder: Chemisch-technisches Repertorium, herausgegeben von which can be effected by turning the balance round Dr. Emil Jacobsen, Berlin, R, Gaertner, 150 p., in Svo. It on the cylinder till it does so. Fig. 2 shows how to issues every 6 months, and contains extracts, recipes, proceed in "new work." The balance cock, centre &c., from 105 foreign reviews, on bleaching, building wheel and cock, and 'scape wheel and cock being materials, dyeing, oils, varnishes, textile fabrics, screwed on the plate, invert the cylinder to be turned leather preparing, metallurgy, photography, chemicals, in; placing the surface of the lower plug on the sur&c., and, moreover, a bibliographical index of all face G of the balance cock, shorten the arbor till the that has been published on these matters in those re-point comes just below the 'scape wheel. (The cylinviews: to be obtained, I think, at every German der turned in complete is shown merely to facilitate.) bookseller's in London. Since the bottom of the 'scape wheel occupies exactly

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the middle of the notch in the cylinder, by placing the shortened point on one of the spokes (allowing for flattening and the thickness of the spoke), it can be seen if the surface G comes exactly in the middle of the notch.

Here the adjustments for the balance and hairspring collet may be safely turned away (but after the other arbor is shortened and before its pivot is turned in), roughly taking the height by placing the point of the shortened arbor in the middle of the space between the 'scape cock S and the centre wheel E, and seeing where the surface G comes on the collet. With a callipers P P, the upper and lower endstones FF being off, take the height from hole to hole; shorten the other arbor and pivot it in. Placing the pivot in its hole, the lower endstone being screwed on again, and the balance cock slipped on to keep the cylinder upright, see if the notch is too high for the 'scape wheel; in which case shorten the pivot with piece of oilstone or very smooth file to nearly the proper height. Finish fitting on the balance, letting it down till it occupies exactly the middle of the space between the centre wheel E and the 'scape cock S; taking care that it fits pretty t'ghtly in its hole, as this is essential to its turning true when rivetted on. Prass it well down all round on the shoulder before trying for the height. Fit on the hairspring-collet DD also pretty tightly, and turn in the top pivet. Screw on the balance cock without the endstone, and if the pivot projects through the hole, shorten it flush with the top. Then try again with the index and endstone screwed on, and if the cylinder is bound, just free it. See that the balance clears the curb-key or pins and stud for the hairspring. Round up and polish the ends of the pivots, which will give the proper endshake, and rivet on the balance.-NOBODY.

[2338]-SAW TEETH.-In answer to "R. T. S." I send him a sketch of my favourite form of circular and deal frame saw teeth, the segment of C saw teeth are drawn half size for 30" C saw, the deal saw teeth are the proper size and deptb for A speed saw table of

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150 or 170, both are sharpened with the flat file, both top and gullet, with about as much lead as is shown in the drawing. If" R. T. S." has a less speed than 700 or 750 he must not carry so much hook on C, saw teeth. The way I get so much hook on my saw teeth is by means of thin grindstones, which I put on the saw spindle. I grind on the back of the stone, the saw being laid flat on the table, having a small jet of water running on the point of contact. The operation requires tact and care, as the stones are easily broken.MILL SAWYER.

[2370.]-PEPPER MOTH.-The following answer will perhaps satisfy "Pupa." The caterpillar of the Phalana Bitularia is of a pale colour, and has at the back two black spots. It feeds and is found on the elms, birch, rose, and the willow.-A. TOLHAUSEN, [2426]-PIG IRON.-"Ironworker" will find that pig irou, after having been stocked for the length of time he mentions, has little or no sand on it, whereas

new iron is generally well covered with this substance.
I scarcely need tell him that that the sand (silica)
excites a scouring action in the furnace, and that
it causes the iron to melt thin; no doubt he has
observed, that after putting clay on the bridge, in
the jambs, or elsewhere, in the furnace, if it (the clay)
has got on the bottom, or into the iron in any way, the
This
heat has been harder to work than usual.
arises from the presence of too much silica, as in the
case of the new iron, and, as in the process subsequent
to puddling, it cannot be eliminated; the result is, a
hard and brittle finished iron.-CINDER.
[2376]-LIFTING SACKS.
-I think the following ar-
rangement of pulleys will
suit "Rusticus. A power
of 125lb. applied at P will
keep 250lb. at Win equilibrio,
and if the power be increased
it will lift it.-W. H. THORPE,
Reading.

[2374.]-BREWING." A Reader of Old Books" gives "New Subscriber," incorrect information respecting works on Brewing. Levesque on Brewing," is published at

BEAM

V

218,, aud Donovan's work can be had in one vol. for 3s. 6d. If New Subscriber is in London, and will call at No. 20, Hop Exchange, Southwark-street, he can see copies of all the works in print on the subject.-W. L.

[2382.]-STARTING VALVE.-I think the following form of starting valve will suit A. W. T." It was designed by myself some time ago. It combines a reversing apparatus and starting valve in one. When

STEAM. PIPES

STARTING HANDLE

the slide A is in the position shown in the engraving,
the steam flows from the steam-pipe, through the hole
in the slide, and through the hole B in the block to
the cylinder. Now if the slide be brought forward so
that the other hole in it is opposite the hole C, the
engine will be reversed. But if the slide is put in the
middle the steam will be shut off. D is a plan of the
face of slide, next the steam-pipe. I have made two
holes in it, so that it shall not have to slide far either
way, and consequently take up less room. If "A.
W. T." adopts this plan, I should like to know if he
makes it answer.-W. H. THORPE, Reading.
[2430.]-FROM MR. G. BATES.-It would hardly
become me, as Messrs. Hopkinson and Co's agent, to
answer your Leamside correspondent's questions in
the manner suggested by him. The best answer I can
give is, that several of the valves are now in working
operation at Leamside, which place I pass through
weekly, and if he will be good enough to send me his
address I shall be glad to explain the working of the
valve personally to him, and also fix him one on ap-
proval free of cost, which is our usual way of doing
business.-GEORGE BATES, Engineer, Eastbourne,
[2435.]-PROJECTION.-Proceed as in No. 2376, up
to finding the line a N; then on any line take mk and
nk, equal to A N and a M, and draw k l perpendicular
to mk and equal to a a'; join m and n 1, and set off
lo, pl, and a' e', equal to 1, the side of the cube. Draw
07 and pr parallel to k, and set off baqk and d a
equal to v k; then a projector from e' will mark off a e
ou the plan, and projectors from c and d on the plan,
will mark off c' and d' on the elevation. A few parallel
lines will then, in the usual manner, complete the plan
and elevation of the cube. I have given this solution
and that to No. 2376, because it contains all the lines
of construction necessary, and they are simpler, and I
have always found them more readily understood than
the more general form given by Bernardin;" indeed
I believe these are about the shortest and simplest
solutions that can be given to these problems.-T.
BROWN.

Darlington.

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been thus prepared (a small quantity of water is some-
times added), they are placed in a tray or vessel, con-
taing water which is gradually raised to a tempera-
ture of 212, which converts all, or I should say, a por-
tion of the water into steam, which displaces the air
previously contained in the case and in the pores of the
meat; when this is done, the hole is closed with solder,
and the meat will keep for a very lengthened period.
T. S. CONISBEE.

[2450.]-FASTENING PIN TO BROOCH.-I find
that shellac answers very well. The way that I
fasten pins on brooches is to melt the shellac on the
brooch with a small rod of iron made red-hot, then
heat the pin in the flame of a candle or gas-light,
then stick the pin when hot in the melted shellac on
the brooch. Care to be taken not to handle it until
the shellac sets.-J. O.

[2451.] DIAMETERS.-TO "AMATEUR." Amateur" is not right in the way in which he set about finding the size of the sun. The proper way would be to estimate its size as seen by the naked eye, and then to multiply it by the power he has applied. Say the sun appears as ift. in diameter to the naked eye, then with a power of 60 it will appear to be 60ft.

in diameter.-SCORPIO.

[2465.- COIL.-"Induction asks, is an inch spark from a coil containing 2lb. of wire as much as he can expect? This is not near a proportionate result; he ought to get about double that length, and as the faults of coils generally lie in the bad insulation of the secondary, I should advise him instead of adding more wire, to make perfect what he has done by winding the wire again, and taking greater care with the insulation. In such a coil the wire ought not to be brought nearer the vulcanite ends than in. Also the farther he works out from the centre the more insulating material he must use between each layer of He can overcome the second grievance by using a solution of bichromate of potash as a substitute for his enemy, filling both the porous and earthenware pots with it, thus converting a Grove's into a bichromate battery; it will not be quite so energetic in action, but at the same time there will not be the least smell.-A. E. TUCKER.

wire.

while afloat, but the tenacious adherence of barnacles. seaweed, and slime, renders all such efforts futile.PATIENCE AND PERSEVERANCE.

[2471.]-SUMMER BEVERAGE-LEMONADE.oz. citric acid, two pennyworth essence of lemon, Pour one pint of boiling water on 1lb. loaf sugar, dissolve the acid in a little of the liquor in a teacup, drop the essence of lemon on a piece or two of the loaf sugar, and drop them in the liquor, stir it well; when all dissolved, strain through a piece of muslin or a wire strainer into a decanter; it will keep for a long time; mix it as you would greg. It a little more water is used it will not matter; it will not be quite so strong. Tried and approved. Some think a dash of wine or brandy is an improvement.-GROCER.

[2474.]-APPOLD PUMP.-The makers publish the sizes of the pumps, and the particulars of the quantity of water thrown: sizes of pipes required, &c.. but they do not give the number of revolutions the themselves, for what reason I do not know; I have pump requires to make, which I believe they keep to adduced the following formula from experience. For diameter, and so on: instance: class 1, 6" diameter, class 2,8' dia, class 3, 12

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The useful effect is said to average about 73 per cont. Molesworth's formula is very incomplete, and requires the divisional number as above to smit be different sizes or diameters of the pumps.-Nr.

[2479.]-MUSIC.-" Clerk " having eng red music plates, had better send them to some litho musie printer, who would transfer copy of same on to stone. This process is much cheaper than printing from the plate, and far better in appearance.- ZETUS.

"Sub

[2482.]-FUEL FOR PORTABLE ENGINE.- I have never found that coke of ordinary quality injured the fire-box of a portable engine more than coal, in fact, from the relative cheapness of the two fuels, coke is more economical, even supposing that the fire box were more rapidly deteriorated by its use. scriber" will, however, find his tubes require cleaning out more frequently when using coke, owing to the quantity of fine dust caused by its combustion. With the worst samples of coke (those containing the most sulphur), the wear and tear is very slight indeed, and the difference between coal and coke would be so small, as hardly to admit of being described as a percentage.

[2465.]-COIL-The length of primary coil-viz., two
layers No. 16, is rather vague, as given by "Induc-
tion," as he does not give either the length or the dia-
meter. If the primary wire bears the proper propor-
tion to the secondary coil, he ought to obtain at least
a 2in. spark, or supposing a slight fault to have been
made in the insulation of two or three of the layers,
1in. It is a point often lost sight of in making coils,
that their action (as their name denotes) depends on
the principle of induction, and when this is taken
into account, it is evident that the ultimate result ofT. S. CONISBEE.
the secondary coil must be in exact ratio to the cause,
ie, the primary coil and core. If the proportions are
right, I do not think it would be of the slightest use
to add more wire, but I should be better able to judge
if I had the length of the primary wire given. I
have recently been favoured by M. Faurr, with one of
his newly invented batteries, which I hear has been
tested in competition with one of Groves's. In the
former case, the galvanometer needle was deflected 39°,
and in the latter 409, while the permanency was in fa-
vour of the former by some hours. Its construction is as
follows:-In place of a platinum plate, we have a vessel
made like an ordinary ginger beer bottle, but instead
of earthenware, it is made of some plumbago compo-
sition, this is filled with nitric acid, and the mouth is
stopped with a carbon plug, into which is screwed a
binding screw of ordinary construction; the bottle is
placed inside a zinc plate, bent to encircle it, and the
whole is placed in an ordinary round battery jar. The
fluid used in the outer cell is common salt and water.
In use, this battery gives off little if any fumes, is cheap
to work, and may be obtained at Elliott, Brothers,
Charing-cross. I do not find the fumes from Groves'
battery at all inconvenient, as it can generally be
wires covered with gutta percha, carried through a
easily placed outside a window, and the connecting
small crack left between it and the sill into the room
to the coil. The bichromate battery gives a very
powerful current, no fumes, and lasts a very short
time. It is practically useless, at least I have found it
so, for lectures, or where it is required for any
lengthened period.-T. 8. CONISBEE.

[2485]-GALVANIC ENGINE.-I beg to inform "Old Salt" that the electro magnetic engine which he wishes for information about was invented by Professor Jacobi, of St. Petersburg. That engine is said to have propelled a boat carrying 12 persons against the stream on the river Neva. The construction was as follows:-There were 8 electro magnets fixed on to 2 discs of wood; the one dise stationary, and the other movable. The faces of the poles of the magnets were made to pass almost, but not The commutators quite, in contact with each other. of the engine were so arranged that as the moveable disc revolved, and its inagnets were approaching those on the fixed discs, the poles were of the opposite kind, therefore they were attracted towards each other; but as soon as the momentum of the machine had carried it so far that the centres of the magnets had passed each other, the current was changed, so that the poles became of the same kind; and therefore they repelled each other, and thus rotation was produced. I never saw a detailed account of the above invention, and this account which I send is mainly taken from Lardner's Electricity and Magnetism." My own opinion is that in such an engine, there would be very little power, as of course you only get the effect of the lateral pull of the maguet. I have had some experience in electro magnetic engines, and the more I know of the matter, the less probability I see of any practicable application of electro motive power as a

substitute for steam.-HENRY CHAPMAN.

[2497.]-FROM "A THINKER-In answer to "Costant Subscriber," the width of frame at seat is 20in.. the width between the centres of tiers of grinding wheels, 2ft. 7 in.; length of cranks, 74in.; distance of bar (on which the front levers work) from the seat, 16in.; height of said bar from the ground, 2ft.; length of levers below fulcrum to centre of working joint, 184in.; length above fulcrum, 22in.; length of connecting rods from centre to centre, 3ft. 9in.; distance between centres of levers, 13in.; distance of axle of driving wheel from axle of guiding ditto, 2ft. 5in.; height of top of seat board, above axle of guiding wheels, 94in, a vertical line from front edge of seat board would be 24in. from axle of guiding wheels; the lower board iin. less; the box lid slopes and turns downwards; extreme width of sest board, 19in.; extreme breadth of ditto, liin.; foot treadle from fulcrum of levers, 16in.; length of guiding levers, 2ft.; distance of their connecting rods from zontal line from the axle, and their working joints are rather large, so as to give some play room when in use; the guiding levers are enclosed at each end of the lower board, in a light iron rail to support them; the The above dimensions are for an average-sized mar form and composition of the frame may be judged objectionable, but with the addition of only about 5lb. to the weight, I have at once firmness and steadiness, also durability and lightness in appearance. - A

[2442,]-MOUNTING 'LARGE CYLINDER.-Mr. Woodleigh can mount his electrical cylinder in the following manner. The caps should be made of metal, as they are neater and stronger than wood, and they should fit over the necks of the cylinder, which should be slightly roughened with an old file and a little emery and water. The caps should fit loosely, and the easiest way to make them is out of brass tube, tances, to be afterwards filled up with the bolts fasten- fulcrum, 7in. The connecting rods run in an bri

with the axis soldered into it. The cement which have found to answer best for fixing the caps on to a cylinder is made of a mixture of about 1lb. of resin, 3oz. beeswax, and a small quantity of red ochre.HENRY CHAPMAN.

[2442.] MOUNTING LARGE CYLINDERS. Cylinders for electrical machines are generally mounted on wood axles, never metal ones, and as the hole in the centre is generally truer than the rim round the same, the wooden axis is inserted in the hole, and secured by an electrical cement, made of 4 parts rosin, 4 parts beeswax, and 1 part red ochre, all melted together and applied hot. Care must be taken that the mixture is not so hot as to crack the cylinder, and for this purpose it would be as well to warm the latter before applying the former. -T. S. CONISBEE,

[2446.]-MEAT PRESERVING.-The simplest way of preserving meat in tins for a long voyage, consists in placing the required commodity in a tin case. soldering on the lid, leaving merely a small orifice uusoldered. When a sufficient number of tins have

[2466.] SHEATHING IRON SHIPS WITH COPPER-I think our friend, "The Harmonious Blacksmith," is misinformed about the Admiralty having adopted permanently, any plan of sheathing iron ships with wood, and afterwards coppering or zincing them. Many patents have been taken out with this view, but, so far, none have come into use, from the difficulty of making complete adherence, also perfect insulation, and cost of working. Muutz's Metal Company brought before the Society of Civil Engineers, in June 1863, the following plan-viz., a large number of holes, of small diameter, are drilled in the plates of the ship's sides, a sheet of india-rubber is then so applied, that it not only covers the holes, but completely fills them up, the sheathing is then applied and fixed with suitable nails, ebonised. The cost of working the above would be a bar to its general adoption. Another patent leaves out bolts at certain dising the wooden sheathing; here the difficulty, as in many others, is so to cover the heads of the iron bolts with some composition as to prevent galvanic action. Zinc sheathing is not a good detergent from fouling, and was introduced some years since to cover the bottom of colonial built vessels, iron fastened; were it efficacious in preventing fouling, it would be easy to galvanise the iron of vessels; but galvanised fron rapidly fouls, and vessels using it require constant clearing. Copper and Muntz metal seem to be the only preventives so far known, and many compositions having copper, &c. for their base, have been tried with varying success; the latest, and I believe the most successful is a thick coating of some adhesive material, painted on hot, and copper in minute particles, dredged on and rolled to make a smooth surface. Arsenious acid has also been tried, but it soon destroys the plates; so does the red lead paints, and so far the right thing has yet to be discovered. Several patents have also been advertised to clean the bottoms of vessels by brushes, &c.,

THINKER.

2499.J-APPARENT ANOMALY. My inquiring friend is quite correct in stating that the avoirdupois weight contains 7000 grains troy, but the 24 grains to the dwt. does not belong to avoirdupois, but to troy weight, which contains 5760 graius, the ounce trov being quite different to the ounce avoirdupois.-H. STEPHENSON.

[2505.]-WEIGHT OF WATER-A cubic foot of rain water, when the barometer stands at 29-5 metres, weighs 1000oz., or 62.5lb. Sea water = 64 14lb.SENEX.

APBIL 29, 1870.]

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2509.-PUMPS -You cannot raise 4000 gallons of water (or 64 cubic feet per minute) with a fall of vater 8ft., and only 50 gallons per minute (or 8 cubic eet). The ram would be quite inadequate.-SENEX. The caterpillar of A. [2510.)-PEPPER MOTH. Bitularia is ground colour various from almost putty colour, some with green tinge and some tinge of red brown. On each side of 5th, 6th, 7th, 8th, 10th, and 11th segment is a reddish-raised spot, and there are two such spots on back of 9th and 12th segments. It feeds in August on acacia, lime-birch, oak, and It turns to a chrysalis in the round in September, the moth comes out in May; The above is taken from Newman's Illustrated History of British Moths." £1. best work I ever saw.-A. NIOBE.

many other trees.

not common.

The

2519-VULCANISING INDIA RUBBER.-The apparatus used by dentists will do for vulcanising of any kind. The smaller the proportions of sulphur in the rubber, and the lower the temperature used, the About 10 or 15 per cent. of sulphur, and a temperature fter and more elastic will be the india rubber. of 270° or 275° for 4 hours, will make an elastic rubber. per cent. of sulphur and a temperature of 315° for 2 hours will make a hard vulcanite like ivory.-A 728-WATERPROOFING PAPER.-To waterin 1 quart of water.

DENTIST.

proof packing paper, dissolve 1lb. of white soap In another quart of water 1 ounce of gum nitric, and 6 ounces of glue; e two solutions, beat them and soak the paper quid then hang it up to dry. From "The Best ything."-BUSY BEE.

i

different sized sheets of paper, the dimensions of which I give, and he has merely to fold a sheet to take in either 8, 16, 24, 32, 36, or 64 pages to get at the measurement of any sized book he is likely to meet in the ordinary course of life. If I had a rule and the books handy I would give the dimensions he asks for; but I think I have made it sufficiently plain. A slight reduction should of course be made for" trimming edges, but that again is compensated for by the covers of the book. Sizes of sheets of paper :-Imperial, 30 by 22; super-royal, 28 by 20: royal, 24 by 19; medium, 33, by 18; demy, 22 by 17; large post, 21 by 16; post, 19 by 15; foolscap, 17 by 13in. With these dimensions given it will be easy to fold up a sheet to any required size of page and the measurement will then be plain enough. But if "F. F." cannot understand, and will let me know, I will " try again."

-SAUL RYMEA.

W

suggests that we (your readers) should bring our "bricks," and I therefore venture to contribute mine. I have always considered the study of galvanic batteries, with a view to economy and constancy, to gether with intensity, as most interesting and most important to science in many directions, and I shall endeavour to describe (briefly) those batteries which I consider the most useful. They will be mentioned under two heads, first, single fluid batteries, and second, double fluid ones; amongst the first there are Cruikshank's, which consists of plates of copper and zinc, cemented into a wooden trough and excited by a weak solution of sulphuric acid and water. This battery, although a most important improvement at the time it was invented, is now entirely superseded. Smee's battery is a very useful arrangement for experimental use if it is not wanted to be very constant, or to be kept in action for a long time. The con[2563.] SMALL COPPER COIN. The great struction of it is as follows: There is an earthenware vessel to contain the exciting solution, which consists scarcity of halfpennies and farthings, coined by of one part sulphuric acid to about 7 of water. The copper and brass pieces called "tradesmen's tokens."' held in a wooden or gutta percha frame between the They were struck, as their name indicates, by private negative plate is made of platinised silver, and that is government, led to the issue, abont 1648, of the small two positive plates, which are made of zinc. By far tradesmen, for the use of their customers; and also, but more rarely, for the use of a whole village, These latter were usually the most powerful battery that I have seen or used is one invented about 1852 by Mr. Martyn, J. Roberts, borough, town, or city. both as regards constancy, intensity, and quantity called "town pieces," and your correspondent's coin It consists of an earthenware pot to hold the exciting is one of them. It is engraved in Snelling's "Copper solution, undiluted nitrous acid, the positive plate is Coinage," plate 1, No. 32, and is most lik ly a halfpenny made out of pure tin, and it is placed between the struck by the corporation of Dover.-HENRY two negative plates, which are made of pure platinum. HENFREY, M.N.S., &c., &c., Markham-house, Brighton. [2563.]-SMALL COPPER COIN.-This copper coin I have used a battery of that kind continually for many was probably issued by the town authorities of Dover, consecutive hours, for the electric light, without being able to detect the slightest variation in the current. The disadvantages are the cost of construction and such coins, or tokens as they are more correctly -CURIOUS AFFECTION OF THE TEETH. working, and; the large quantity of fumes evolved from termed, being very numerous at that period. The is is only a deposit of tartar from want of clean- the nitrous acid. There are several other kinds of single design on the rev. is described by Boyne in his list of Wine 18 on the teeth at present must be care-fluid batteries, but those I have mentioned I think the 17th century tokens, p. 130, No. 160,"St. Martin on tussy choped off with a fine thin-edged instrument, are the most important of them, and I now pass on to horseback, dividing his cloak with a beggar, who is To which is appended the following following him." Daniel's constant battery conbut at angle near the joint to enable it to be got the double fluid kind. note:-St. Martin in Roman Catholic times was patron, into any crevice with ease, and the teeth must be kept sists of a copper vessel, which at one and the same Saints of Dover, and the Church of St. Martin-leclean aiterwards with a strong rough tooth brush and time holds one of the fluids (a saturated solution of camphorated chalk and water. If the tartar is sulphate of copper), and forms the negative plate. copped clean away and the teeth kept clean the gum Within the copper vessel is placed the porous cell, and will grow up again in a week or two.-A DENTIST. in that is placed the positive plate, made of a thick [224]-LONGITUDE.-Difference in time between rod of zinc, and the other fluid, 1' of sulphuric acid to 6 of water. This battery is a very convenient one Belfast and Glasgow, 6 min. 40 sec.-D. B. [2526.-SUBMARINE LAMP.-No lamp could be from the constancy of its action and the absence of The Maynooth battery, invented by Pro"red" with air by a single tube. Every miner fumes. knows that to obtain a proper supply, a current must fessor Callan, is a very powerful, but a very un7 be established by means of a "down cast" and "up pleasant one to work with, on account of the nitrous cast" shaft. This could be effected without much fumes given off from it. It is arranged as follows:difficulty in the case of Mr. W. A. Hackett's lamp, There is an outer vessel made of cast iron, which which may be taken to represent a mine on a small forms the negative plate, and holds the one fluid (unGroves's scale. But common india-rubber tubing will not do, as diluted nitrous acid), in other respects the arrangeit would be throttled by the pressure of the water. "H" ment is the same as the preceding one. must get some tubing kept disturbed by a coil of wire battery is one of the most useful, I think the most. It This is enough on the is made as follows:-An outer cell of earthenware inside, such as the divers use. general question; but if Mr. Hackett has any practical and an inner porous cell; the negative plate is made object in view, I shall be happy to supply him with of platinum, and the two positives are zinc, the fluids used are, for the negative plate in the porous cell pure nitric acid, although I think nitro-sulphuric is better. The fluid for the positive plate is 1 of sulphuric acid to 6 or 7 of water. Bunsen's battery is similar to Groves's, excepting that the negative plate is made of carbon cut from the graphite deposited in gas retorts. Some years since (with a view to economy) I tried aluminium instead of platinum for a negative plate, but although I got a fair current from it, I did not consider it at all equal to Groves's, and one thing fatal to it was that the aluminium was slowly dissolved by the nitric acid, and I therefore discontinued to use it. In all the above arrangements the zinc is amalgamated with mercury.-HENRY CHAPMAN. NAMES ON PLANS.-A [2547.]-PRINTING

further details.-THICLORIUS.

[2534.]-SOLUTION WANTED-If "Minnehaha " will draw the figure of his problem, using the same letters as in his query, and join D E, he will find that, since A C2E C, and BC= 2 CD, and the angle A C B is common to the two triangles AB C, DCE, A B = 2 E D, and the angles CED, CDE = CAB, CB A, respectively; therefore D E is parallel to A B; therefore the angles B E'D, ADE ABE, BÄ D respectively; therefore the triangles A B G D G E are similar; and AG: DG:: A B:DE:2:180 that AG 2 D G.-HUGO. [2534]-SOLUTION WANTED.-Join D with E, then by similar triangles A B G and E D G we have AG: DGAB: DE ACCE=2:1 (by construction) therefore

AG 2 DG.

E

G is the centre of gravity of the plane A B C.
A. TOLHAUSEN.
[2534.]-SOLUTION WANTED.-The straight lines
AD, BE bisecting the sides of B C, AC of a triangle,

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[2549.]-SCREW STEAMER.-I consider that an
engine of one horse power would be ample for such a
boat as Mr. Douglass M'Carthy mentions, but a verti-
cal direct acting engine would be better than a hori-
zontal one.-HENRY CHAPMAN.

[2555.]-ECHO.-An Ayrshire amateur can produce
an echo on the cornet by simply putting a silk hand-
kerchief up the bell, but it is usually done by putting
a mute (to be had at any music warehouse) into the
bell. Some cornets have a special arrangement for
producing the above effect.-HENRY CHAPMAN.
[2557.]-COPP ER COIN.-A German counter, I
believe, I have several varieties of it, all thin and
with badly engraved inscriptions. No value.-BER-

NARDIN.

[2561.]-BOOKS.-The following dimensions are, I believe. correct :-Imperial 8vo., 11 by 7; super, royal 8vo., 10 by 67; royal 8vo., 10 by 6; demy 8vo. 8 by 5; post 8vo., 7 by 2; crown 8vo., 7 by 5; demy 12mo., 7 by 4; royal 18mo., 6 by 41; foolscap 8vo., 31; foolscap, 12mo., 5 by 31; royal 32mo., 5 by 34 demy 32mo., 4 by 23; demy 48mo., 3 by 24in.; edges

intersect at G: show that A G is double of G D-6 by 43; imperial 32mo., 5 by 3; deay 18mo., 51 by making figure. I have

triangle C D E sim. to C B A (Euc. vi. 6)
.. A B = 2DE

triangle D G E sim. to B G A (Euc. vi. 4)
.. AG 2 G D.
FRANCK.
[2535,]-COIN.-Is a coin of Christina, Queen of Swe-
den, struck. I think, for the province of Dalekarlen :
DAL.
-BERNARDIN.

[2539.]-OKE-A Turkish oke is as nearly as possible equal to 2lb. 12oz. avoirdupois. A kilogramme is about 1lb., so there is not much difference.-EDAR

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uncut.-BUSY BEE.

[2561.]-SIZES OF BOOKS.-It is almost impo3-
sible to give "F. F." the exact sizes of books, because
"' but I will endeavour to
papers are not made "true;
explain the matter to him. When a book is described
as being crown 8vo, or fcap 8vo, it is meant that the
"sheet" is folded so as to print, on the two sides, 16
pages. In the same way 12mo means that the sheet
is so folded as to contain 12 pages on each side, i.e.,
24 pages. 18mo would therefore be 36 pages to the
sheet; 32mo. 64 pages. When no description of the
paper is given, demy is usually the size meant; but in
this particular the wording of advertisements is very
arbitrary. The size of the last volume of "
MECHANIC was demy 4to, though to suit the exigen-
cies of printing the 32 pages were printed on one
sheet, equal to four sheets of demy. As "F. F." is
doubtless aware, there are various names given to

our

The

Grand the mother-church. Amongst its other privi-
leges was that of beginning service before all the
other churches and chapels in the district.
church was destroyed at the time of the Reformation,
Dover Fair is still called St. Martin's Fair. The
same device is on the tokens on the Borough
Counter-seal which dates as far back as the year
1305. This has been described by Browne Willis as
"a highwayman robbing a man on foot."-D. T.
BATTY.

[2564.]-LEADEN COIN.-Is probably a token of the
be of that period, but cannot bring any authority to
time of Elizabeth. I possess similar ones reputed to
bear. I shall be equally obliged with "Old Coin "
for any authoritative information upon it.-D. T.
BATTY, 9, Fennell-street, Manchester.
[2566.]-TOOTH-POWDER.-Camphorated chalk is
very good, and economical as well. The following is
also recommended:-Orris root, ounce; gum myrrh,
ounce; nutmeg, finely powdered, 1 scruple; chalk 1
ounce; mix. Proved.-BUSY BEE.

[2566.]-TOOTH POWDER.-Prepared chalk lb., camphor 1dr. The camphor must be finely powdered by moistening it with a little spirits of wine, tracted.-MINNEHAHA. and then intimately mixed with the chalk.

Ex

[2577.]-BORING GLASS.-"C. H." can bore a hole in his glass sheet, in the following way: Let himmark or scratch a ring, of the size and in the place required on each side of the sheet. These rings will, of course, exactly correspond. Then let him mark out a series of Points pretty near each other, round the circumference of the rings, taking care that these points shall also, in every respect, exactly correspond with each other. He should then fix uprightly in a vice a smooth pointed steel punch, and arming himself with a similar punch and small hammer, get some assistant to hold the glass sheet horizontally with one of the circumferential points, steadily resting upon the upright punch. Applying his own punch to the same point on the upper surface of the glass, and using gentle blows of the hammer, he will soon work his way down through the sheet, until the two punches meet, leaving a small perforation without causing the slightest "star" (unless he is clumsy). Repeating the process at other points, all round the circle, he will find at last that the included disc can be readily kuocked out by a slight tap, leaving the required hole; where rough edge, can be amoothed off by a file.-MECHANICUS.

FILES SHARPENED BY GALVANIC CURRENT.-A very interesting and economical process for re-sharpening files has been exhibited before the Société d' Encouragement of Paris by M. WerderWell-worn files are first carefully cleaned by mana. means of hot water and soda; they are then placed in connection with the positive pole of a battery, in a bath composed of 40 parts of sulphuric acid, 80 parts of nitric acid, and 1000 parts of water. The negative pole is formed of a copper spiral surrounding the files, but not touching them; the coil terminates in a wire which rises towards the surface. This arrangement is the result of practical experience. When the files washed, and dried, when the whole of the hollows will have been ten minutes in the bath they are taken out, be found to have been attacked in a very sensible manner; but should the effect not be sufficient, they are replaced for the same period as before.

RESTORING LIFE.-In consequence of the experiments of M. Labordette, the National Lifeboat Institution has decided on omitting from its new instructions the statement that among the appearances which generally accompany death the "jaws are clenched and the fingers semi-contracted." Dr. Labordette's nine of twelve cases, after clenching of the jaws, &c., experiments on animals, have clearly proved that in had been observed, life had been restored; and has given several instances of human beings having been resuscitated under similar circumstances. also in the strongest manner expressed his opinion, founded on these facts, that the clenching of the jaws and contraction of the fingers, after short immersion, indicated remaining vitality, and that the same should enconrage perseverance in the efforts to restore life.

He has

ment.

NOTES AND QUERIES.

[2580.]-LARGE TELESCOPES.-I would ask some correspondent who can give a reply, if he knows where it is possible for a working man like myself, who cannot afford to purchase a large telescope, to obtain the privilege of occasionally looking at some of the wonders of the heavens with a powerful instruI have a small, but beautiful defining telescope, of 17in. aperture, which will divide double stars as close as 33"; for instance, and Bootis, Aquarii Pegasi, but when I read the accounts of astronomers, and what they have seen with their gigantic telescapes, I long to see some of the wonders they describe. Some years ago, I believe, Mr. Slater, the optician, used to exhibit a large Equatoreal at his house in the Euston-road, but it has now disappeared. Two or three street telescopes, of 4in. or 5in. aperture, I have looked through, but not one of them was of any

account?-G. F.

[2381]-GUTTA PERCHA SHOES.-Will some of the obliging correspondents of our journal, favour me with information on the following queries ? 1. Are gutta percha shoes injurious for the eyesight, if so, why? 2. Which way shall I proceed to re-sole an old pair of gutta percha shoes? If possible, state price of the material (gutta percha), and how sold?-D. E. WILLIAMS.

obliged to any reader of the MECHANIC, who may have
the knowledge and experience, for any hints which
would enable me to get the machine into working
order?-G. F. L.

[2594.] BORING WOODEN HANDLES IN
LATHE.-Will some reader tell me how to bore
wooden handles in the lathe, after they are turned
ready for driving the tool in. There was a query on
this subject December 17th, but I have seen no
answer. Perhaps "J. K. P." will oblige by recom-
mending a method of doing it ?-A. B.
[2595.]-PROJECTION.-TO "BERNARDIN."—

Your able reply on this subject on page 93, induces me
to ask if you would inform me of any work that
explains the whole subject thoroughly. I have gone
early through Davidson's book in Cassell's series,
but there is evidently much beyond what that book
teaches ?-J. H. YEwDALL.

[2596.]-BUSY BEE.--Could some of my fellow sub-
scribers kindly reply to a few queries contained in the
last dozen back numbers, bearing the above signature?
One answer to 12 or 14 queries!-BUSY BEE.
[2597.)-BEESWAX.-I shall feel much obliged if
some contributor will kindly give a recipe for making
beeswax, common, only sold in th eoil and colour shops,
the principal ingredient of which is yellow resin, or
could any one name & book, where I could find a
recipe for making it?-Hoмo.

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In dividing the angle into five equal parts, M Fis trisecting the angle, La is marked off from F or E marked off from H on B H, and in dividing the angle into seven equal parts, N T is marked off from on BK, &c., &c., whilst the distance S E, marked on the last arc, remains the same for all divisions of the angle.-Y. P. W.

[2606.] - DAWN, &c.-What countries have the longest dawn and twilight, and why -DAVID E. WILLIAMS.

[2007]-HEATING GREENHOUSES. -W any

[2598.]-ELECTRIC.—Will "Sigma," or some other
electrical correspondent, kindly state if a Leyden jar
may be charged by a glass tube, excited by being reader give me some practical instructions for sting
rubbed with flannel, sufficiently to give shocks, &c.,
and if so, what ought to be the length and diameter of
the tube ?-SLASHER.

[2582]-WEIGHT OF FRUSTRUM, &c-A frustrum of an iron cone has a height of 12ft., the diameter at the smaller end is 2ft., and at the larger end 4ft. A cubic foot of iron 410lb.; what will the weight of the frustrum be, and supposing that 4 tons weight be[2599.] — HANDRAILING. cut off the lesser end of the frustrum, what will be the diameter at the p,ane of section, and the height of the frustrum left?-Ó. H. S.

[2583.]-THE "ENGLISH" VELOCIPEDE.-Will "A Thinker" oblige me. with a further description of the steerage of the "English" velocipede, (a descrip. tion of which occurs in the ENGLISH MECHANIC of April 8th), as I think of making one on his principle, but cannot quite understand how he guides it, whether from the front or hind wheels? Likewise, will some reader inform me if it is best, previous to driving in the spokes, to soak the wooden nave of a wheel in hot water, or not?-C. T. W.

[2584.]-SULPHATE OF LEAD BATTERY.-I should feel obliged if "A Good Boy" will send full directions for charging the battery, also if the zinc should be amalgamated, and how much lead should be put into a 6n. porous pot; by so doing, he will much oblige, as I have the materials ready, according to directions given in Query 2184?-CARFAX.

[2585.]-FLOCK PAPERHANGINGS.-I should be obliged by any one practically acquainted with the manufacture of paperhangings, to inform me how "flock" paper is made; also, if the gold patterns on same are printed on the paper before or after the flock is laid on? Information in detail is sought.-ZETUS. [2586.]-WHEEL MAKING.-Will some mechanic give me information relative to the best kind of machinery for forming carriage or cart wheel spokes, and any other part of wheels?-INQUIRER. [2587.)-CHINA GRASS.-Can any of my fellow subscribers inform me where I can get a small quantity of China grass ?-C. KATKA.

brother

[25881-EQUATOREAL MOUNTING.-I should feel obliged if "Hyperion" would answer my query respecting his mounting, No. 1792, in No. 256, Vol. X. -NEPTUNE, No. 1.

[2589.-RAISING WATER.-With respect to my former query, respecting raising water, as "Machinator" did not seem to understand me, I will try to explain myself more fully. I do not want the water rased to the dam above, as he seems to think, but to supply a cistern with fresh water. It is not needful to be a continuous stream. I want it from a mill tail, so as not in any way to interfere with the working of the water-wheel. It will require to be raised 8 or 10ft. High, but no particular quantity.-NEPTUNE, No. 1. [2590.]-BOOKS WANTED.-Can any of my fellowcaders tell me the names and prices of any works now published, on the construction and details of small engines, from 1 to 3 horse power, either vertical

or horizontal ?-E. B.

Can any brother reader inform me of a cheap work on handrailing and staircasing, or whether there is an American work out, and the price of it ?-PATELEY BRIDGE.

a small greenhouse, say 10 x 4? I have read all the notes recently inserted, but they do not contain anything sufficiently detailed. I want particulars of cost of the various methods. The small amount of attention requisite, economy, and durability, are essential desidorata. Does any one know anything of Mussett'a system? Information will be useful to many besides. SAUL RYMEA.

[2608.)-SULPHATE OF ATROPIA.-Sometimes sulphate of atropia, however neutral, irritates the skin; could any kind brother reader tell me the reason?-OCULUS.

[2609]-OLD COIN.-While digging in the garden size of a halfpenny. On one side is a head and some a short time ago, I found an old brass coin, about the letters; all I can inake out are, VES-ASIANVS...... AVC; on the other side is represented a tree, with a human figure on each side, one in a sitting and one in a standing posture; under these are the letters 8 C, and round it, -VDAEA CAPTA. Will some brother reader tell me what coin it is, and if of any value?

[2600.]-CLEANING OF DIATOMS.-Will any of your readers have the kindness to give a little information how to overcome the following difficulty? I have tried two or three times to prepare diatoms for the microscope, but with only partial success-not those found in guano and other earths, but the living diatoms. I can succeed, by the aid of muriatic and nitric acids, in getting the diatoms quite clean, and to show the markings very well; but I cannot get rid of a fine filamentous sort of network, which appears to be some sort of vegetable remains. I have boiled them in nitric acid till the diatoms have been injured or destroyed, but the result has been the same. I should feel truly obliged to any one who will tell me how to vanquish this enemy to a neat and perfect slide. I have read several books on the subject, but can get no [2810]-ANILINE DYES FOR FEATHERS.information on this particular point. What I now seek for is, some brother reader's practical experience.-me of the method for obtaining the colour known as Will some subscriber to your excellent journal, inform BEATEN. Bismarck brown, for feathers? Detailed particulars of the process, or any other useful information on the subject, will be thankfully received.-AN AMATEUR

2601.]-VENUS.-On the 1st of November, 1871,
Venus will be at her greatest brilliancy; will" Omi-
cron," or some other clever astronomer, please to show
how the computation is to be made, according to the
formula given at page 509, Vol. X., viz. :-
+ R) (~ + A R)
2 43

Where

T

(r +

9-9965.
R radius vector of the earth = 9919, its log. =
A = log. dist. of Venus from the earth = 96234.
= radius vector of Venus 7215, its log. 9-8583.
G. FIRTH.
[2602.J-LOSS OF TASTE.-Can any reader inform
smell and taste, lost for some months, from a bad
me of a preparation, medical or other, for restoring
cold?-W. P.

[2003.]-BOOK WANTED.-I am in want of a prac-
tical work upon the duties of a rail mill manager,
with instructions as to the various calculations which
enter into that business. If such a work is in exist-

X. I. D.

DYER.

[2611]-RE-GILDING BANNER.-Can any of your readers inform me how to gild or re-gild a silk banner, such as used by Sunday schools in processions. I have tried by marking out the letters with gold size, and then laying on the gold leaf, but the size penetrates through the silk, and makes the other side of the banner look anything but neat. I have seen several banners, and the impression of the letters does not penetrate through the silk, so I think I must have got hold of the wrong process, although the person I got it from was a professional gilder?-INQUIRER.

[2612]-NEWARK'S CEMENT.-Would any one above cement, used very much at New York for conbe so kind as to give me some information about the crete building; how is it made (if not a secret); if it has been, or is used in this country, and how is it sold? Any information would oblige.-JOHN HUDSON, Sunderland.

[2613.]-SOCIAL SCIENCE. - Will some brother reader kindly let me know if I could procure the pamphlets which are printed after the Social Science meetings, and if so, to whom should I write? Could I become a member without being present at the meetings?-THOMAS J. O'CONNOR.

[2614.]-WRITING ON GLASS.-What acid must I use, so as to have the letters white when burned in? Perhaps "Engraver" will kindly assist.-THOMAS

ance, will some fellow subscriber give publisher's name and address, and title of book ?-J. JONES. [2604.]-PROBLEM.-I beg to thank Mr. Tolhausen and Mr. Biggs for their replies to my query (2180), in last week's and this week's MECHANIC. Would some of your mathematical correspondents kindly give me a few hints as to the solution of the following, which I extract from the Science and Art (2591.7-FLYING MACHINE.-I wish Department Examination papers a year or two ago? J. O'CONNOR. to make a model of a flying machine; could "Two points are 2 and 2:5in. from the centre of a circle some kind of lin. radius, and 3in. from each other. Draw the brother reader give me the following information? circle which, passing through these two points, shall How much gas in a bladder would it require to raise touch the given circle."-Y. P. W. 3oz. ? What kind of bladder would be the best to contain the gas, also size of same, and also what kind of gas? Would the common coal gas do?-CASUAL OBSERVER.

[2592]-DEW-CAPS TO TELESCOPES-Would Mr. Blacklock or Mr. Purkiss, be so kind as to say whether it is necessary to use a dew-cap with a reflecting telescope (aperture 6in.), in order to prevent the condensation of moisture on the plane mirror; if so, what length should it be, or if there be any other

method of protecting the plane ?-HUGO.

tried the method recommended by "Vibrator," in this
[2605.]-TRISECTION OF AN ANGLE.-I have

week's ENGLISH MECHANIC, and have found it to act as described in the case of the obtuse angle, but in the case of the acute angle, does not the point page 89), fall on the outside of BA? I make it so. I suppose the distance FP would be added to BD, In that case and the arc described from B with B D + D2 as radius. Would not the same principle apply to the division of angles into any number of equal parts, with this difference-viz., Suppose the angle A B C (page 89), to [2593.]-DEFECTIVE BATTERY.-For a number be divided into five equal parts; on B C mark off five of years I have been unable to labour through ill equal distances, proceed as before; mark off the dishealth. For several month I have been using one of tance H L on the fifth arc, join the fifth point with B, Smee's electric machines, and feel slightly better. It and where this straight line cuts the are E HI (say in went well for a time, but of late has been going very the point r), mark off Er from the fifth point on BC, feebly, the vibrating often stopping. Occasionally it and proceed as in the other case. Again, suppose the would go a few minutes or seconds, if the finger were angle A B C is to be divided into seven equal parts; gently pressed on the screw above the vibrator. on BC mark off any seven equal distances, B D, DE Recently, when trying to discover what was wrong......I K, draw the arcs LD, ME, NF,OG. PH, with it, two of the zinc plates got loose when in the 2 I, and RK, bisect the angle ABC by the line B X, acid, and in trying to tighten the screw, the silver cutting M E in S, mark off the distance S E on the are plate bent and touched one of the former, producing a R K from the point K-viz, the points 1, 2, 3, 4, 5, 6, hissing sound, whitening and thickening the acid. I and 7; join 7 B, cutting the arc NF in the point T, removed it as quickly as possible, and straightened and fastened it properly. Since then I can get no vibratory action, whether from the above cause or not, I cannot say. The zine plates were amalgamated immediately before it stopped. I put in fresh acid (1 to 8 of water), but this brought no improvement. Perhaps the silver plates require platinising. May I ask if they are done with the same material (mercury), and in the same way, as the zinc plates? I would be truly

from the point K mark off K V, equal to N T, and from
B with BV as radius, describe the are V U, and the
distance S E will divide the arc U V into seven equal
parts, whence the angle A B C is divided into seven
equal part as required. On seeing the article on the
Trisection of an Angle," in this number of the ME-
CHANIC, it struck me that by a somewhat similar
method, an angle might be divided into any number
of equal parts, and I have thus attempted it in the

[blocks in formation]

spondents supply me with a simple and cheap indoor
[2616.)-WET RAGS.-Would one of your corre-
ton per diem?-DRYER.
method for drying wet rags, say to the extent of one

[2617.]-GLYCERINE AND OLEIC ACID.-Can oleic acid are made?-EXPERIMENT.

any of my fellow readers tell me how glycerine and

[2618.)-TOF.R.A.S."-I feel obliged to "F.R.A.S." for his answers to my inquiries. I am sorry I did not describe my telescope sufficiently; it is an Shin, silvered glass, reflecting instrument, equatoreally mounted. I wished to know how to set it absolutely level, N r, S. r. E, S, so that I should find the declination of a star right according to Mr. Webb's book, iu whatever point of the heavens the instrument was pointed. It has all the motions necessary, but I do not know how to ses about it, or where to begin ?-H. A, C.

(2619.]-TO "TANGENT."-Will" Tangent" oblige by giving a drawing and description of Raumkort double mercury contact breaker for induction coil, and also say if I can use anything better than about five layers of gutta percha tissue to insulate the layers of secondary wire, the amount about 1lb. of No. 35. 1 find a difficulty in getting the tissue to lay flat and snooth; would a solution of gutta percha in bisulphide of carbon, laid on in several coats, answer as well as the tissue?-VACUUM TUBE.

[2620.)-BARTON'S BUTTONS.-Diffraction, say Sir J. Herschel's ("Familiar Lectures on Scientific Sub

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