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what he might have vaguely guessed from the aspect of the crcpnficular curve. "T. A." founds his views o:» the admitted difficulties inTOlved in the problems presented by the sky and its varying lights. But these difficulties need not cause ua to bllud ourselves to clear evidence of another sort. As for "T. A.*s" explanation, 1 must say it is too wild for serious comment. If, indeed, he could show reasons for believingeither—1st, that iron, magnesium, &c, can combine chemically with oxygen apart from the conditions which have hitherto been found necessary for such combination ; or—2ndly, that these conditions exist in the upper regions of the air, he will doubtless be listened to gladly by scientific men—always supposing those reasons to be founded either on observation or on experiment.

1 do not consider the ordinary employment of the photographer to involve "a series of very delicate

111 Vnilt Wriif inns r-AId'ornino- flu* nfllnpn nnd rxmnat-tiac nf

puuiu^rapiicr w involve a series 01 very aeiicate investigations concerning the nature and properties of light," so far as the subject "T. A.' has In hand is concerned. All photography can teach on that subject is that the light from such and such parts of the sky tins nt such nnd such times a greater or loss active power. The conclusions to be drawn from this are by uo means necessarily such as " T. A." imagines.

R. A. Pboctor.

FAIRY WHEELS.

Sib,—After having read the letter, p. 233, several times, I cannot discover of what kind of stone those discs are made. If they were not so great, I might havo taken them for parts of fossil encrlnites, but "Subscriber" says none of them were the same size or thickness; they must then have been made by man, cut, Ac: but for what purpose? Two suggestions present themselves. They were intended for throwing with thongs, or lassoes, or for stringing them as a necklace, or wearing as ornament. Very often pierced objects are found in caves, tumuli, Ac. Might not these beads, Ac, forming part of necklaces, have become, later, objects of exchango —a primitive money? Might it not be possible to trace by that means the communication ancient tribes had one with another? The note of ".Subscriber" affords me the occasion of communicating this idea to my brother correspondents. I hope some other, more acquainted with the question, will bring also bis stock of information. Meanwhile I quote a fow examples, briefly. Mr. Editor, saying all notes should be drawn up as accurately as possible.

Plorted objects have been found in many excavations in France, Belgium, Ac, among what are called the remains of prehistoric times. A necklace of human teeth was found in Belgium; in North America, in the tumuli of Columbia Klver, Walla Walla, many beads, dental ium necklaces, Ac, were found. One tumulus lu Virginia gave 1700 grains or beads; with the Celtic warrior found in England, near Salisbury, were two fragments of fossil encrinito and a bead of pottery; a Celtic nocklace, made of •hells, was found near Dijon, in Krance; many Indians, negroes, Ac, have their shell necklaces; remark among them the cowries—in many places at the same time a money and an ornament. The Egyptian beads, necklaces, Ac, of so many different substances, aro well known to all those who have visited the British Museum. The Chinese have yet pierced metal discs for their money; the English Hong-Kong coinage is another specimen of it. I have said a word, in another number, about the whainpum of North America, also a necklace and a money.

1SERNARDIN.

COLOUR BLINDNESS. Sir,—Concerning the remarks of "An Idipot," in your laBt impression, I have little to say. I have never met with a person to whom red appeared black, and I therefore thought it undesirable to dwell upon that particular form of the malady, though I know such an abnormal vision is repeatedly to be found described in books on the subject, though it is generally allowed that such an anomalous vision is only occasional notwithstanding Sir David Brewster attempted to show tr.at red colour blmdneit is most frequently to bo met with, and that a normal eye loses its sensibility to red more readily than to any other colour, and that a defect In the vision of any person will be most strongly marked when examined by red light. Though " An Idipot" makes no mention of the fact, I should suppose that the combination of red with other colours does not produce the same sensation of colour that a normal eye perceives. For instance, in a purple the red is not missing, but it appears black, whence it is to be inferred that purple appears as a very dark blue I would invite "An Idipot" to make some further observations upon his anomalous vision, for it must be admitted that a colour-blind person is better ad apted to form a perfect conception of his defect than a normal-eved person, and can more readily collect his tacts; for let him (the colour-blind) be the inquirer Instead of the witness, and he may collect evidence' about colours iu every possible shape, from the scientific investigations of the philosopher to the artless remarks of the child. He need not go far for an answer to any question he may choose to put, however abstruse; and as to common facts, almost every one he meets is a competent witness from whom he mav gather them. *

Omicron.

had 110 poles of garden allotment and orchard under my hand alone besides my daily work and law work, accounts, Ac of an evening, insomuch, that I have often seen the sun rise before I went to bed. Pigs, poultry, bees, Ac,hare also hadmv attention. I know rrench and Latin thoroughly. I may, therefore, be said to know what work is, both mental and physical. It is not so muchifor my own as for the children's sake I wish to go abroad. 1 should prefer the trade o( "earth tlokliug" to any other, being the only one I know well. Will "F.R.G.S" either pat me on the back or knock me down at once In the matter of hope?

Railway Clerk.

THE

'GERM THEORY" AND DEDUCTIONS
THEREFROM.

Sir—The freat interest attached to the •' Germ Theory " in any of its relations is myexcuse for asking your insertion of this letter. It is an acknowledged fact, that on elevated lands of high altitude, 7000ft. to 8030ft. and upwards, the inhabitants enjoy a striking immunity from may diseases, particularly from phthisis. It appears also to be the case that a sojourn in such derated rlgions is a sure means of arresting any further phthisical development which might have had its origin at tower levels.

These facts I have always thought most interesting and well worth of investigation, but although I have continually been on the lookout for a solution of them I have never yet seen a logical, or even plausible reason propounded. A considerable amount of investigation and attention to the subject—all the pros and cons duly considered, but into which I need not enter—has convinced me very strongly, or I may say entirely, that the "germ theory " would bo found to account completely for the phenomena.

Cold is a well-known arrester of germ development and consequently ot their physiological, pathological, and putrefactive effects,but I have never observed it advauced that a rarefied atmosphere may be so also— although of course from quite different reasons— simply from the fact that nir of great tenuity will not siu

pend the germs mechanically and carry them, about. If experimental research proves this hypothisis to be correct, I think it may be logically iuferred that those diseases which never appear amongst the inhabitants of high altitudes, or are arrested in others upon goin" to reside there, are really due to, and sustained by" the presence of animalcular life. This is particularly self-evident I think as regards phthisis, and suggests the trial of a simple means for arresting and curing that dreaded disease.

I propose it might be done either by Altering the atmosphere thoroughly before inhalation-much in the way some of Professor Tyndall's experiments suggest—or otherwise, first heating the animalcular air (to a degree sufficient to destroy the vitality of the germs and consequently multiplying their morbid action) and then cooling previous to using for respiratory purposes.

Taking for granted that the practical correctness ol my theory is demonstrated, let me by way of Illustration, suppose that such a building as the Palace of .Sydenham, for instance, were applied for utilising It, when hundreds, nay, thousands of invalids could lire comfortably and pleasantly together for some months, being all the time quite excluded from the—to them—morbid atmosphere of the outer world and that thin air supply was treated, prerlous to introduction Into the building, in either of the ways I hare suggested. I think the same constitutional effects would be found to be produced—and for similar reasons—as already by a few months' residence at high altitudes. A similar arrangement, and for a like object, might be carried out in hospital practice Such experiments as would place the correctness of my views beyond a doubt are entirely beyond my

This being so, my object in bringing the matter before your readers is that, perhaps, in the event of tlieir thinking my ideas worthy of investigation, some of them will not only experiment themselves, and put the theory to the test, but also, it maybe advocato the matter amongst their scientific and medical friends.

With your permission, Mr. Editor, I beg to as k for a dtscnsBion and opinions of my proposal in the columns of your widely-known journal.

J M o.

represented. 1 think, on p. 176, last number, is known io many places, destroying the trees in the pobllc wtlkn for nioreparticularalseo " DleForst Inecctin." v«nl> Ratzeburg. 3 vols., in 4to; " Kntomologie Horticol-,"' by A ph. Dubois, Brussels, 1865, 1 vol., in »vo, with tine plates; "The Farm Insects," by Curtis, Ac . &c.

Bernabdiv.

THE EARTH AND ITS FIGURE. Sir,—Iu discussing any matter with such gentlemen as Mr. Beardsley, It is necessary to adhere to one point persistently, and have it distinctly settled before passing on to Rnother. Arguing for victory, and not with a sole aim at ascertaining the truth, such a writer acts very much like a small quantity of water contained in a bladder; grab it as forcibly as you will It is sure to elude your grasp, and immediately shlft'irs position to some other portion of the receptacle nnd can only be fairly captured when it Is driven up tig litly into a corner. Mr. Beardsley, like all men of his stamp, never recurs to a shattered argument nor when he finds that an argument has been crushed by a reduetio ad ahnirJum, does he either try to rehabilitate it or acknowledge his fdlurc. Thus, with reference to the explanation of the sun's setting by its gettingbeyond the focal distance of vision, whatever that means, ho declines ta answer the question as to how it Is that the sun docs not appear to decrease in size as it, according to his crotchets,Increases in distance.

I wish to ask an explanation of a passage in Mr Beardsley's last letter, and to state a fact which will be something new to that learned astronomer. I refer first to a vessel homeward-bound. In the approarlito » vessel "the upper masts " and sails are, according tS Mr. B., in focus. If so, how comes the hull to be out of focus, for it is as near osthe.salls (In fact nearer' > Again, how come the upper masts and sails to be apparently growing out of the sea If the curvature of the ocean does not intercept the view? Are we "to believe our eyes," and that the hull and lower sails are under water? Or lastly, are we to believe that the sails have left the hull behind?

.. Vi.1' '*?,' ' ProP080 t° ««te i» relative to the passage 'The sailor knows by the chart the relative position of one country or island toanother." Now that is jun what, but for the invention of a distorted chart constructed on the supposition of the earth being g'iobu lar, the sailor never could know from a plane chart Mercator's chart is so constructed that in orderto preserve the relative bearing the distances are distorted to an unlimited extent, so that a new scale of measurement has to be be used for every degree of latitude, and even then it is only an approxiiaation Had the true distances of the places been preserved' on the plane surface, the sailor would have found the bearings oil distorted and pointed wide of the truo mark.

Then Sir, when Mr. Beardsley has made acquainted with the Mercator chart in universal use, he will explain to us why it is that we cannot draw the surface of the earth on a plane without monstrously distorting either the bearings on the distances. I may have something further to say on the subject, bat certainly not

[It is better that this controversy should now cease — t.i». L.M.]

F. H. N.

EMIGRATION.—TO "F.R.G.8" SiR,-Iamglad to see "Cotton Clerk's" letter in t lie Mr en A»ic for this week. Let me also anneal to "F.R.G.S." Will he kindly tell me if thereta any hope for me abroad, and where, and how ? Although a clerk, I think I know a spade, ahoe, axe,prong, Ac, when 1 see one. I am fast learning how many beans make ->, and can already see nearly as far through a stone wall as some people. I am a clerk 37 years of age married^ with 3 children, eldest 10, youngest 6 (Wth boys). We hare sared a few pound*, and could realise a few more. For the last 3 years I have lived 4 miles from my work, I therefore know bow to walk. I have

BORING INSECTS, Ac.

Sm,—The notice on "Boring Insects," p. 176 of our English Mechanic induces me to forward a few lines on the damage sometimes caused by insects I extracted them from several agricultural papers

In 1832 the Hessian fly, Ceridomgia destructor, destroyed corn in the State of Maine, Vermont, aud in North America, to a value of five millions of dollars

In 1840 another small fly, CeJdomyut trilici, caused in Belgium a loss of 92 millions of francs to the wheat

From 17*0 to '49 nearly all the meadows in Sweden were annihilated by the caterpillar of a phalssna Choreas graminu.'

In .*?? £e 6malJ turnlP flv- IMHca nemorum. devastated in Devonshire to the value of £100000

It is said that in 1784, the wheels of a mill'on the Severn were stopped by the abundance of cockchafers in the water, what may be tho truth of that assertion in our times, in 1866, in the Department of '.Seine Inferleure * ranee, the premium paid for the destruction of the larva; or grubs of the cockchafers was 18,00fif., and the quantity gathered 160.(100 kllog In 1*15 the Department of the Sarthe allowed a premium of 30 centimes for an hectolitre, and 300 millions of cockchafers or larrte were collected. In 1«07 5150 millions were killed in Switzerland.'

e Jhc1»«'rV(r*w l&osropkai, or "printer," committed J^TM,164? *2 18i? lnc»1<:«|ible depredations in She TM''of'?« Harz, in Germany, and caused the stopping of the mine works, and nearly tho total ruin of some villages. In l?s:i alone, 1,501,000 trees were destroyed. There are actually more than 40,000oak trees attacked by the scolytus in the Bois de Vincennes. The common elm scolytus, Seelytm destructor

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RUSHES.—"Bernardin" says: — "In reply to 'Camclford.' p. 207,1 think he might do better to inquire at a paper mill in his neighbourhood, or to the t.ditor of the Paper Trade Rcvieic, 97, Newgate-street London, as I am not able to give him the particularhe desires about price, sic. I believe rushes should bicut and dried, and packed, so as to present the less 11»Ik possible."

wL^' W,?I'FE'S "ORIGINAL" CONTRIBUI lOAb.— \ Ibrator" writes :—" I was rather surprised on looking over a would-be rival to find my method of trisecting published in No. 264, p. 89 of the i-NGLieu Mechanic, copied and contributed without any acknowledgment by a Mr. Isaac W. Wolfe If be wished it to appear iu that paper he might at least have had the courtesy to acknowledge where he saw it, and mot contribute It as the result of his own researches,"

INDUCTION COIL.—ANSWER TO "SIGMA,""M. (i. Cunningham " writes :—'• Permit me to offer my best thanks to 'Sigma' for replying to my letter,

S. 207, I was quite aware of the theory he propounds, ut at the same time not quite satisfied about It, and as my plan only involves a slightly increased bulk I think I will persevere with it. Experience has proved that division of the coll by ebonite discs intensifies the current, and the reason is theoretically explained as 'Sigma' puts it. Why, however, if it be so, employ covered wire, which is expensive, and far more bulky tbaupliiin, the only object being to insulate the layers? \nrnish, paper, tissue or other medium could be employed with greater certainty than any silk covering at a tenth of the price. My coll, now at its 12th layer, aud working with four quart Bunsen elements, gives well-defined improvement as each layer Is finished and I think it will answer well; should It not, however, I will not be so thinskinned as to keep my failure from those whom it may interest."

TESTED RECIPES.-" A.Boughey" write.:-" A 'Morayshire Man" is quite right in his remarks about the above. Some time ago a recipe was given in the English Mechanic for ' brillantlne.' The mixture cost more than what is sqld in the shops, and turned out to be a very greasy mixture, with a—certainly not a perfume—which would effectually prevent any one from using it."

THE "PHANTOM" BICYCLE.-"Donald W. treston says :—" I can recommend the " Phantom" velocipede wheels to your readers as the best I have na\e seen, and as fully answering their description iu the advertisement. J. Tvdeman's uuwarrautable letter made me hesitate in ordering a pair; bnt now I have them, and cun say that his description of the

•Spider' in tho English Mechanic la quite inapplicable to the ' Phantom ' wheel"

READINGS FBOM THE GLOBKS.—" Ab Initio" writes :—"J. Dyer, p. 236, in attempting to correct "T 8 H.' appears to me to confound the words tun and tint* with each other. Philadelphia, for instance, has its time 5 honrn wirlirr than London, it being only 7 a-m, therewhen It Is noon here."

REPLIES TO QUERIES.

[2«S.]-MUSICAL BOX.—I most apologise to Harry Bertram for too severely criticising his description, which, however, 1 Mid tu well repeated as far aa the lesson was lcarat. He means that the end of the roller has a flange which mores in the notch of right laver. This may be the case in very common boxes that only play two tunea. unil I do not tluak would act for three: and it is bad, aa it enables you to shift the barrel while playing, which has a bad effect, or erea to shift the barrel when not playing, which is destruction to the boi. In good boxes it is done by a wheel of the same number of teeth or rather spokes (and no rim) as the number of tunes to be played, which is fixed between the barrel and the first toothed wheel, only fixed eccentrically near the outside of that wheel, and every time it is carried round by the barrel turning, one of the spokes is caught by a fixed stud, and is held by it till the next spoke comes to the right place to be itaelf caught by the stud at the next revolution of the barrel. On the Trass of this spoked wheel is a short piece of a screw or a camb which keeps pushing the barrel further and further until the end of the camb is reached, when a spiral spring pushes the barrel back ready for the first tune again. The music is not stopped by the L-shaped lever dropping into the hole in the end of barrel, but when it does drop in, the curved arm shown in the drawing, p. 164, on the opposite side to the hook, catches hold of one fan of the fly and stops the work*. It is a fan-fly not a fly-wheel, as it is not a wheel at all.—J. K. P.

12«S0.]—OPINIONS WANTED.—Thanks to Mr. Harrison lor his advice about the links and the eccentric. When the lever is in the centre notch the valve spindle end is in preciselv the centre of the link, and the eccentrics are properly set, out I think he is wrong when he says the link ought to vibrate on the centre without imparting any motion to either spindle or valve, for I have noticed several since, and they all work the valve a little, but not enough to open the parts, which is caused by the action of the two eccentrics one against the other. If our paper is an International Mutual /mpeovenlent Society I am surprised that the subject has not been taken up by more of its members.—John W. B«dpoed. [S640.]—OIKDEE PATTEBNS.—In "N.L.'s" answer tomy query he save that making the pattern bent would not do much good, as the moulder would ram it out of shape. Now aup

Ci.se the girder to be 40ft. long, section as per skeich (Fig. 1), ottora flange »iin. thick, rib ljin. thick, how will he ram down the ends, and if he ran bend it to auit his requirements is it not just aa possible to make the pattern bent, and so save time, and with more surety, for what is to prevent the ends from springing out again, as it would be moulded on its side? Again, a gutter of this section 28ft. long (Fig. 2), thickness at A Jin., and at bottom fin., whieh would be moulded on a block to fit the inside, how would he bend that, and what weight would he require on the middle to keep it down, as it would be

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moulded with the bottom downhill. And again a foundation plate 33fL section (Fig. 3) thickness of side ABCI) {in., and the top l,io., moulded with the top or round side down hill; and lastly one of a smaller pattern, a tile plate bearer for malt kiln floors of the same sise (Fig. 4) section, thickness at point of web tin., A at top R tin., and thickness of top flange tin. and 4ft. Gin. long, which he might bend in the pattern with a bit of trouble ana some weights to keep it there; but which ■ Hid be safest, his plan or to make the pattern bent? And 'b :a he finishes by saying that It is a question whether one

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oa-ce of practice is worth a pound of theory, but I think fnic the manner in which he writes he haa not got an ounce of Li-eery with a proportionate leas part of practice on that sabjt-:t. The above examples have all been cast, and the -.-. holt went straight except one of the foundations, and then the pattern had to be made a little more round. I hope this will be received, as Bent, in a free open spirit.—John W. BauroaD.

[S675.}—POLISHING PIVOTS.—The ridges mentioned by "C. R." are caused by the polisher having the side that polishes the shoulder too much inclined to the side that polishes the pivot. It ought to be nearly at right angles. Pressing too hard against the shoulders has also a great deal 1 to do with it. The polisher ought to have a side as well as a length motion given to it now and then, to cross the marks as it were. The bow takes long strokes, while the polisher moves very little; and always contrary to the direction the pivot turns. "Cylinder " will do well to attend to the above; and I may add, in answer to his query, the conical pivot he marks B is need only for good and best work, in holes furnfshed with endstones. Cylindrical pivots with the oboulder bevelled off are for more common work, though I have never seen but once or twice a Geneva cylinder with

conical points, even in the best work. Cylindrical pivots are the easiest to make, and in foreign work a Swiss pivoting tool and burnishers are used. All English pivots are made with a polisher. I have seen a brass ceutre used, the pivot laying full length' on it, but I prefer the point only supported. "J. A. E." uses the right word when he says * catching " the centre, lie must not file away all the broken pivot, but leave the mark where it was; he will find it much easier to catch the centre of that small ring than if he made the surface uniform. If he cannot mark the point exactly at once he must try to draw it afterwards to its proper plsce.— Noaonv.

[3707]—TWISTING POWER OF SHAFTS.—The relative strength of shafts to resist torsion is as the cubes of their diameters, the description of metal being the same. The relatioe strengths of different metals are as follows:—

Taking cast iron = 1,

then wrought „ = 113

shear steel = V7S

cant „ = i0; .

and a shaft to be equal in strength to a cast-iron one, must

be. if of wrought iron — less in diameter, shear steel -S3 »

1 cast steel --.

8 Q Q, R.

[3714.]— BOILER.—" One in a Fix," may stop the humming noise made by his boiler by getting two sheet iron plates to fit each aah-pit. and having them drilled with a quantity of j'' holes ; the plates may be attached by hinges, or made to lift away when the ashes are got out; if he will try this I am confident it will cure his noise, having tested it frequently myself. Do not put too many holes in at first, but add them afterwards if the draught requires it.—J. B. Caossi.KV.

[3780.]—AREA OF SAFETY VALVES.—The'difference of the areas of the flat and concave valves may be found as

follows :—

Area of flat valve = 42 x 78o4 = 12-5664 sq. in.

The area of the concave valve may be found by adding the Bquare of the radius of the valve (-in.) to the square of the

depth of concave FM^—in./and multiplying the result by

8 3 1410. nencewehave

2» + [ —\ x 31416

Ihen

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13-0081 sq. in.

0-4417, the difference of the areas of the two valves.—Wit.liam afooa, Jun.

[3717]—COPPER COIN".—I beg to inform S. Smith that tins is a coin of Emmanuel de Rohan, M.M. of the Knights of Malta. 1 am sorrv I cannot give any particulars; should I be able at some future time I shall be glad to do so,—D. T. Batty, 9, Fennell-street, Manchester.

[3743 ]—SYPHON PIPES.—I think "Calculus" will find that the quuutity of water discharged by a syphou will be equal (or thereabouts) to that discharged by a plain pipe of the same bore and length aa the ayphon, and with a Bead equal to the difference of level between surface of water in vessel or reservoir, and lowest end of syphon pipe. This ean be found by any of the ordinary rules for that purpose, and perhaps the following (I believe by Hawkaley) is as good as any:—

C = 2*5« 4 x D»

C = cubic feet per minute L

L = length in feet

h height „ „ D = diameter of pipe in feet. The dimensions and quantities are here given as in feet, but will, of course, do just as well in inches, or any other unit of measurement.—Q. Q. R.

[3744.]—SILVER COIN.—I think there are errors in the legends; the nearest approach to it is a silver penny of James 1st, which reads on obv. "IDG. ROSA. SINE. SPINA." and on rev. "1VEATVR. VNITA. DEV8." If there is no mistake in J. Nash's description, the query must stand, but if otherwise, it had better be put right in your next.—D. T. BAiyr.

[3745.]—STEA.M PIPE JOINTS—I always use loz. of sal ammoniac to every lib. of borings, with just a dash of sulphur to quicken it in hardening.—Anti-eotptian.

[3746.]-TESTING BOILER.—It will beof no use of Thos. Edwards testing his boiler without he can see the surface and seams of all his plates. If his boilers are only single rivetted, he cannot work them at more than 151b. pressure. I had two boilers which I worked at 151b. pressure. I had my boilers tested to 1201b., indicated by Bourdon's pressure gauge: they stood it better than they could be expected, although they (the engineers) will not allow them to be worked with more than 151b. pressure, being single rivetted boilers.—Anti-eotptian.

[3750.]—SILVER COIN.—"A Beginner" will see his coin in Ruding's Appendix, plate 99, No. IS. It is thus described, p. 300:—"Ohv, BALDRE1) REX. Head rudely drawn, Rev., + ETHEL..D MONETA. Double cross with an amulet in the centre. Bodlean Library." I imagine it to be at least scarce, if not very tare.—D.T. Battt.

[3751.]—ASCARIDES.—"A Great Sufferer" should take half a glass of good port wine (not the cheap (!) advertised poison) every morning, fasting, for three mornings, then stop three mornings, after which repeat the dose. This will cure him in a month, provided he is careful in his diet, avoiding fruit, and especially cake or pudding with currants. Proved. —F. H. ,

[3755.]- TURBINE WHEEL.—" Senex" seems to have asked me almost the same question as I have asked him, which was, what quantity of water and height of fall was necessary to drive au one-horse wheel. However, as near as I can get at it, the fall would be 20ft. through a pipe of Jin. internal diameter. I would also aBk what height of fall or pressure of water is termed high pressure, as in some street mains ?—A. B.

[3757.]-A BOOKBINDER'S PLOUGH.—Enolosed Is u sketch on the scale of t of an inch to an Inch, A A is the right hand cheek of the plough, 18in Ions by 4J high, 1| thick i the left hand cheek Is of the same di

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pirt Ib Hln. iu diameter, at the shoulder of the handle p-'tit U ia 2ia.,a groove | wide Is turned in tho plain part, which allows the bolt D to pass through, and act as a sort of garter pin, to cause the two cheeks to recede from or approach each other ; tho bolt D Is of iron | square, and bevelled out to } square at the bottom, so as to grip theknifo l*\ which has a squaro hole, bevelled, to match the bolt. K la a nut, which screws down on a lozenge-shaped piece of iron, so Ha to grip the knife very tight. C C are two guide rods 13m. long, i| square, firmly fasteued into the cheek A, the handle of the screw is 5fn. long, as tho knife cuts the handle should be gradually turnod, so as to keep the knife to the work.—Ab Initio.

[3765.]—NAVAL ARCHITECTURE —" G. E. J" should write to C. W. Merrincld, Esq., (Principal of the Softool of Naval Architecture,) South Kensington Museum, who will give him any information he may aik for aa to the evening classes.— R. M.

[3708.J—POISONING BY CANTHARIDES,— I am very sorry to see "M. D." states in page 237. VoL XI. that the effects of cantharides are only transient, &c. They are uot so; in small doses it is an irritant of thobladder; in larger or improper doses it produces serious bleedings often resultiug in death. It is administered surreptitiously under the idea that it is provocative of physical love, for which purpose >t is absolutely useless. No man conscious of his moral responsibility would ever administer it, excepting under and in strict accordance with the orders of a well qualified medical practitioner. I believe any person administering it for improper purposes is liable to a criminal prosecution.—E. Dbacon.

[3772.]— OLD COINAGE.—Old copper coins may be sent to the Master of tbe Mint, Tower-hill, London, who will, no doubt, take them at, I believe, their full value.—E. M.

[3773.]—l-PLATE PHOTO CAMERA.—It" "Snatch Block" will tell me whether he wants to make a portable camera, or one for the studio, I will tell him how I made mine. Of course, if the Editor, be agreeable, I could describe both, i-plate is not too small to begin with.—Mus.

[3774.]—LQOSE PULLEYS, &c.— The best plan will be to bore the pulleys about fin. larger than the shaft, and sweat a brass bush in it, or one composed of the following alloy:— (Babbitt's metal) tin 10 parts, copper 1, und antimony 1. I have proved the latter to be a very good wearing metal— Stakm.

[3774 ]—LOOSE PULLEYS, fee.—Wm. Corlett should turn the shaft end true, then bore out the loose pulley, and let the pulley work on a loose bush, bored and turned to fit the two, with a small collar and set pin at the outer end for fastening on the shaft; this would be a much better job thau any composition, and is a very general thing nowadays; cast iron and cast iron would then work together, which is to be desired.—Mutual Improvement.

[3774.]—LOOSE PULLEYS, Stc.—When worn in. the hole should be bored out sufficiently large enough to allow substance for the bush, which may be good gun metal, and will wear very well; the bush should be pressed iu tight, tost it in nv not move in the hole, and when it wears out, which will not be for a long time, if properly oiled it can be knocked out, and a now bush put in without doing anything to the hole in the pulley.—J Ok Ath.

[87760—BOILER SAFETY-VALVE.—"One in Need." has not given quite enough information to enable me to answer his question exactly. Does the weight of valve and lever, as stated by him to be 7$H>., give the true pressure exerted by them on the valve when in place? I expect not, and should imagine their effective pressure on the valve to be at least 21 lb. Since the area of a 3-inch valve is 7 square inches, this will give Sib. per square inch. So the weight will have to balance only S71b. per square inch, and will be found thus:—

7 sq. in. x 571b x 3Jin

. ■ = about 561b.

20in. + Siin.

[3776.]—CASE FOR FERNS AND MOSS.—The best form is to make the legs and upright rods which hold the glass in one length, with a light rod running round the top, in the underside of which is a groove, There should also be a groove ou the top edge of the box which holds the soil, and the glass made to shde on one side to allow the plants to be got at

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glasses can he easily removed for cleaning. &c. A hot water tank in the bottom heated with a small gas jet underneath will make a tropical store on a small scale, or a hot water, pipe round the inside, and a small copper boiler underneath wilt do even better. 1 have one, and for two years have grown with success the rarest tropical plants, orchitis, &c. One year I had orchids only, the next I had caladiums, Egyptian papyrus plant, dwarf palms, tree ferns, &c. Now I have aquatic plants from the Amazons and Borneo, pitcher plants, Sec. It costs me little or nothing, as the plants always increase in value, and 1 have no difficulty in exchanging them. So far as treatment goes, he will learn more from the persons he buys his plants from than any one else, M each plant has peculiar habits. The case should have a reasonable amount of ventilation, so there is no need for care in fitting the glasses and woodwork closely ; mine is open i m at every corner all the way up, and we burn a large quantity of gas in the room without the slightest effect on the most delicate plants ; if they are quite close they get mouldy.—A Djemtist.

[3779.}— BOILER.— ■« One in Need," should give the effective weight of his lever, and the weight of the valve; if he is unacquainted with any method ef finding the same, he may apt it as follows :—Place the lever at the fulcrum on a three

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sided file, and fix the short end, at the centre of motion, hang weight sufficient to balance the long end, thus the effective w«ight is the weight required to balnnce, and the weight of lever, to which he must add weight of valve—Jonath.

[377».]—BOILER SAFETY VALVES.—According to "One in Need's" figures, the weight required on end of lever would be 671b. 10oz., but I am afraid the 71b. 14ox. weight of lever and valve does not include the effect ire weight of lever, in which case he is altogether wrong.—Mutual Iui'&oveMent.

[S779.]-BOILER.—A weight of 681841b. placed on the end of the lever will give the required pressure. This weight is not exactly correct, bat it is as correct as can be calculated from his description of the valve. If he requires the exact weight, he must give the weight of the valve and lever separately; if the lever be of the same breadth and thickness through nut, its effective pressure can easilybe calculated, but if tapered lie must disconnect it, and try what weight will balance it, makingthepointin a line with the centre of the valve, the fulcrum.—Thomas J. O'connor. [3780.]—AKEA OF SAFETY-VALVES.—The area of the r_ valves for pressure is not at all affected by the difference of form shown in the two sketches. They are, however, not good forms of valve, as when the steam is blowing off strongly the current is considerably impeded by meeting the flat or concave surface of the valve before escaping. The form of valve ordinarily used on locomotive engines is, perhaps, the best of be simple valves, and is somewhat thus, the

seating being a very small mitre, or sometimes a narrow fiat ring of bearing surface.—Q. Q. R.

[3786.1-AREA OF SAFETY VALVES —I think "Flat and Concave Valves " will find on a little consideration that there is no difference between the two, because if there seems to be more surface in the concave, the column of steam is only tm. dia. in the pipe's neek. Did he ever hear of the man who made a corrugated piston bottom, so as to work the steam on a greater area P—Mutual Ihfkovbicknt.

[3793.]—COOKING BY GAS—If the gas is not under the meat inside the oven, the meat is quite as nice as that done before the fire. We find the beat way is to put & Buusen burner under an iron plate and cover this with a large tin cover, which is cased in flannel to prevent loss of heat. The meat must be supported on a stand in the centre of this, with the gravy flu under it. By this arrangement the meat is cooked as before the fire by hot air, and the most critical person cannot tell how it has been cooked. The same burners

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coal at 23s. per ton, for less than 2s. per week. At present we hare four cooking burners and cook for seven people never using the fire for any purpose, and I estimate the cost for cooking to he about 1b. per week . this, of course, includes boiling water for children's baths, washing floors, &c.—A Dentist.

[3793.]—COOKING BY GAS.—I beg to inform "J. M.D." that I cooked by gas for several years for a large school. The flavour of the meat, 8tc., were not only preserved, but the process was cleaner and cheaper than the usual mode. There should be a pipe on the top of the oven for the escape of the carbonic acid gas. 8tc, which should pass into a chimney or the open air,—J. Dyer.

[3794.1-POLISHING STEEL.—'* Cylinder " must be sure this clock is good metal, that his stuff is good, and that his steel was properly hardened before it was tempered, and not empered too much. He must have everything clean, and not dust flying about. The block must be refiled before each attempt, the least quantity of red stuffused, and the polishiag moved very little during the process. Anything more is difficult to describe, as it is by the feel he will k now when he has rubbed enough. It all depends on leaving off at the right moment—Nobody.

[37970-TELESCOPE STAND.—If Mr. Turton will call at Brunswick House, Tanner's-htll, New-cross, he shall see the stand and mounting of my 9in. reflector.—J. Dyer.

[3798.}—TUBE FOR 9in. REFLECTOR.—The thickness of the sheet iron of which the tube of my telescope is made, is rather over the 20th or an inch. The tube is 7ft. 5in. long and the focal length of the speculum is 6ft. 6m.—-J. Dibs.'

[3799]-BRASS COIN.—Is a Nnraberg counter. As many of those legends have no meaning, and some of the devices fanciful, it is next to impossible to give further information about them than what has been given. A friend of mine laughingly said to me the other day, ■ I think the Nurnbergs have been pretty well worker! or used up in the English Mechanic." I quite agreed with him, and I am pretty sure, Mr. Editor, that when you see one again you will be able to say in your" Answers to Correspondents " what it is without giving us a woodcut.—D. T. Batty, 9, Fennellstreet, Manchester.

[3801.]—LEVER ESCAPEMENT.- "Gracchus " asks for plain instructions to plant a lever escapement. This implies that all the pieces are read? made, and all he wants to know is how to plant or pitch them off into connection with one another. But as he adds, "proper dimensions." &c., he evidently wants to be shown how to make a suit of clothes to fit anybody, "proper dimensions," of course. I must remind him that a knowledge of the escapements is acquired studiously and with great application by all who wish to know anything of their business. The subject will bear no trifling with, and "Gracchus " must not think to get off less easily. I could do nothing to help him without an accurate plan of what he wants, or at least the half containing the escapement; and then if he knows nothing on the subject, all my explanations will be double Dutch to him.—Nobody.

[3803.1-CIUNGING COLOUR OF PRIMROSES.-I have about half a doien differing in colour from vellow to a very dark purple. This change was caused by being yearly transplanted into richer soil. They first come an orange colour, then alight red, and eventually purple. The following recipe will show "J, D. M." how to change other flowers:—The colours of flowers may be changed by certain additions to the soil in which thev grow. Powdered charcoal deepens and intensifies. The fluwes of the dahlia, rose, petunia, &c. Carbonate of sod* reddens hyacinths; and superphosphate of soda alters in various ways the hue and bloom of other plants.—W. F. Haigh.

[3810.]—CYLINDER PATTERV.-Let amateur make his cylinder model similar to sketch, the main feature of which is

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the valve box and thoroughfare cores. Iu the first place, put a good core print on valve teaj then make a core box to suit the print, and inside this and from bottom side screw on three pieces of wood exactly where the ports want to be, and let them come through the top, and by making the core box for ports long enough to come through the valve box core, it all goes in together and prevents the moulder having to put studs in to carry the cores of the port. By putting a thick print on valve box it gets a good bearing surface for the cores. —john W. Bedpobu.

[3813}-POROUS CASTINGS—This Bhort query would admit of a very long answer; hut I will try aud make it as plain as I can. 1st. The sand is a very important thing ; if it contains too much clay it is a great difficulty to make castings free from airholes. Clayey sand Is only fit for light castings, where good impressions are of value, likewise avoid everything that will generate gas, such as coaldust, charcoal, and like substances. Ram your mould, regular, and vent or

Sierce it with innumerable airholes; cast or pour it with as ot metal as you can get, not forgetting to run it in the mould as quick as it win go in. The sufiage must be kept back with a skimmer during the pouring of the metal in the mould, and the head or git must be made so as it will be kept up or kept full during the casting operation.—N. L.

[3819.]—CHEAP GAS.—A great saving in the consumption of gas can be effected by regulating the pressure of gas on the burners. When more gas Aowb to the burners then they can properly combust, the illuminating power of the gas is deteriorated, and, of course, the gas bill is increased. One of the best ways to prevent this waste of gas. is to have a good regulator fixed near to the meter, whiclt would regulate the flow of gas to all the burners. Another plan I have also adooted, that of placing a disc, with a small hole in the centre for the gas to pass through, in the elbow or brass socket in which the burner is screwed. The whole in the disc must be made according to the size of flame required at the burner. I have been able to save 25 to 30 per cent, in the consumption of gas by adopting the above. With regard to

the carburisation of gas by causing it to pass through a vessel filled with some hydrocarbon, this plan has been tried under two or three patents for the last 30 rears, but nearly in all cases where it has been adopted, after a long trial it has been abandoned on account of the difficulties, and the absence of the economy anticipated- A word respecting gas regulators, and regulating burners:—The best regulators far fixing near the meter that I know of (and I have tested several) are those made bv W. Tices, 65, Bartholomew-close, E.C., and by W. Sugg, Vincent-street. Westminster; Sugg^ has also a sjood regulating burner. Nearly all the regulating burners offered to the public are worthless after they have been in use for a short time,—L. M.

T3820.]-AQUATIC BOTANY.—Straftodcs AUitdn. or Soldier plant. There is no plant so beautiful and interesting as this for the above purpose. Tie it to a stone and sink to the bottom; it will soon send up young plants on long stems reaching to the top of the water like so many juvenile palm trees. After a time the stems decay and the young plant floats free, of a lovely transparent green. They will soon require thinning out; for this purpose a tank should be kept out of doors, in full sunshine, where those not wanted should be placed, when they will get strong and change to a mahogany browu. Returned to the aquarium they will gradually go through all the intermediate shades till they regain their green hue, A constant interchange of tint may thus be kept up. The plant may be grown of any site, according to that of the vessel, and increase abundantly.—Amatkuu.

[382-1.]—GOVERNORS.—I can recommend Porter's patent governors as being very sensitive and powerful. They revolve very quickly—usually from 300 to 400 revolutions per minute—and when properly proportioned will not allow a variation of more than perhaps 3 percent; so that a shaft running at 60 revolutions per minute would not vary more than 2 revolutions per minute. These governors are made by the Whitworth Company, in Manchester.—Q. Q. R.

[3827.]— NITRATE OF SILVER STAINS.—To remove the nitrate of silver stains, pour on solution of potassie iodide, then nitric acid twice diluted, and then wash with hyposulphite of soda. I have found this succeed in removing stains from the hands, but care is required.—Ohio.

[3829.]—SOLDERING.—Perhaps the following may be of use:—A lute for the joints uf iron vessels may he composed of 60 parts of finely silted iron filings and 2 or sal ammoniac in fine powder, well mixed with 1 part of flowers of sulphur. This powder is made into a paste with water, and immediately applied; in a few seconds it becomes hot, swells, disengages ammonia and hydric sulphide, and soon sets as hard as the iron itself.—Omo.

[3834.]—DUMB BELLS.—See "Physical Education." by A. Maclaren of the Gymnasium, Oxford. Clarendon i'resa Series, 5s.— Ofetto.

[3836.]—PITCH OF PROPELLER — The first thing *'T, J, O'C* must do is to bore out the eye of the propeller in. the lathe, and fence np the outside end of the eye for the nut to bear properly that secures the propeller on thi shift; then take it out and lay It down on the ground with that side up that ts faced for the nut, and level it up all the four ways of that part that is faced j then put a centre into the eye of the propeller, and from the centre of the eye draw a circle withany radius ou that part of the eye that is faced for the nut, and divide that circle into 12 equal parts, and also divide the blade from the centre ot the eye to the point into feet, and draw the lines across the blade with a radias from the centre; then take a straight-edge that will reach from the point of the blade to over the centre, and Lay the edge of the straight-edge on the point where one of thedivibions cuts the circumference of the circle and makes it ran into the centre, and keeps it in that position by laying a block of iron on it; then plume down from the edge of the straight-edge with a centre plummet to the divisions on the blade, aud mark Chew with a centre punch; then measure the dist ince from the edge of the straight-edge to the plume point on the bladepresume that it is 6in.; then tarn the straight-edge to the next divisions, still keep it running into the centre, and likewise level, and plume down with the plummet again to the blade, and mark it, and then measure the distance down again from the edge of the straight-edge to the plume point— presume it is 20in. Now the difference between 20m. and Sin. is Mm.; then as every inch of the perpendicular distance gives 1-1 .'tit of the pitch in feet, therefore 11m. would be a 14ft. pitch to the blade of the propeller; and if the blade is not broad enough to take in a twelfth part, divide the circle into 24parts and the blade into Bin., and every $ia. in the perpendicular distance, in the same way, will give a twentyfourth part of the pitch, and so on. The most convenient way to divide the blade is to divide the straight-edge into feet or half-feet, as it is required, and square hnes across the edge; then make one of the lines coincide with the centre of the propeller, aud the edge with one of the points on the circle, and then plume down from these points to the blade and mark them ; then measure the distance down.—G. B. D.

[3845-] —BOEHM FLUTE. — In answer to "Another Flautist's" inquiries respecting the Boehtn flute, I may state that the use of the rings is to stop holes which are beyond the reach of the fingers. On the old flute the holes are altered from their true position from the inability of the fiugerB to reach them: hence its notes are unequal in power, ana are u out of tune." The latter defect is partially lessened by altering the size of the holes, but at the expense of adding to the former. Boehm overcame these difficulties by placing the holes in their natural places, and by making them of equal proportions throughout (the holes being made gradually smaller and smaller through a regular progression upwards), by which means he obtained uniformity of force and tune, anil

Sreat increase of power in the whole scale of the instrument, nt these advantages were met by a great drawback, for he found it necessary to alter the fingering of many notes . and this involved to'those who already knew the old flute the unlearning of one system of fingering and the learning of ;i new. From this cause many, seeing the superiority of the Boehm flute, became dissatisfied with their old flutes; but finding the difficulties of the new fingering too much for their patience, gave up flute-playing entirely. Some few years ago Mr. Clinton, the celebrated flautist, invented a flute called the "equisonant flute," which not only had alt the advantages of the Boehm flute, but retained the old fingering, and with increased beauty and brillancy of tone to the instrument itself. The writer of this has had practical experience of all these fluteB, and much prefers his "equisonant to any other. What I have said about flutes will equally apply to B clarionets. It would take too much space to describe flute machinery thoroughly.—H. T. Lkftwich.

[If Mr Leftwich desires to treat the subject more fully, space ia at his disposal.—Eo. E. M.]

[3840.]—NICKEL.—The following extract may perhaps be of interest to "Another Flautist ,r:_- Nickel (Ni 2fr#7), a metal ol a greyish-whim colour, wuu rauusrauuHc nmgiieue properties, which it loses on being heated to fiuO°. It is ductile and malleable. A Bavarian coin has been struck in this metal, and the impression of the die is said to be very perfect. The sp. gr. of nickel varies from K 2? to S 40 when fused, and after being hammered, from 869 to 90, it has a high melting point, and is but little acted on by dilute acids. Satire nickel is found in the Erzgebirge in small quantities. Kupferaickel. or copper nickel is an arscniuret, and is also tolerably abundant. The nickel of commerce is obtained chiefly from kupfernickel, uickeliferous pyrites, and from the spicfrs obtained as a secondary product in the treatment of the aickeliferous ores of cobalt. As there has been a great demand for nickel in the manufacture of German silver, some improved methods or obtaining the metal have been introduced. They are, however, kept secret; but Mr. Phillips, in bis Mtnualof Mineralogy suggests the following as the process likely to be followed:—*' The roasted ore or spiess, after being disserved either in sulphuric or hydrochloric acid, to which either nitric acid or nitrate of aoda has been added to perotid«e the metals, is placed in large vessels, in which the insoluble matters are allowed to subside. The clear liquor, after it has cooled, and the copper and lead which have been precipitated by sulphuretted hydrogen, may be decanted off and treated by carbonate of lime in the form of common chalk, by which the iron and trace* of cohalt will be precipitated, whilst the greater portion of the cobalt and the whole of the nickel will remain in solution. After the oxide of iron thus precipitated has subsided, and the liquor hns been again syphoned off, the cobalt may be thrown down by saturating the solution with chlorine gas, by the addition of hypochlorite of lime, and then adding carbonate of lime. The liquor syphoned from this solution contains the whole of the nickel, which may now be precipitated by ebullition with hydrate of lime, and dried and reduced in the usual manner —Harry G. Newton.

[5850.3—THERMOMETER—"Thermo" had better place his thermometer against a piece of ice, which will have the effect of causing the mercury to recede towards the bulb; but if the bulb is not broken much, it will soon settle of itself. —Sksci'kr Pabatub.

JB851.]—HARNESS.—" Equestrian " will rind the best way to clean his harness is to well wash it in warm soap and water, (soapsuds would be better), dry it thoroughly, and then rub neafsfoot oil on it; let it stand till next day, and if it absorbs t!.e oil readily, give it another coat. This treatment is suitable for anv kind of harness or leather; but if the bridle ia a black one, "he will find a great preservative in Harris's harness composition—Skmvkr Pabatus.

[5S52.]—BRASS INSTRUMENTS.—They fill the tubes

with melted resin, and twist them about when cold with

apparently as much ease as they would use in bending a piece

ofcord. No doubt a sharp look out is kept for puckers, which

they hammer in directly they appear on the inside of a bend

of course with a small round-faced hammer. Copper tubes

may be filled with lead, but it is dangerous with brass ones,

as, to get the lead out. a ieoo'i heat must be used, which

makes brass brittle, and very likely to give way with the

weight of the lead. 1 saw Distin's factory once, and was

quite struck with the tube bending, which I had supposed

such a delicate operation. I believe it is very dilhcult to get

bruises out of tubes, and that they have a sort of jointed

tnetal mould to put inside a bell which has a bent tube to it,

and which has received any injury.—J. K. P.

;3959 ]—BRASS INSTRUMENTS.—The bends of brass instruments are made by first filling them with lead, and then bending them; after that the lead is melted out. The reason they require filling with lead ia to keep them from bulging oat at the sides. The lead would, however, be inadmissible ni the cose of zinc tubes, as they would melt when the lead was run out. I am told resin would do instead, but this I have not tried. I should advise "Clutha" to try it, and report progress.—Semper Paratus.

[3860-1—COPPER COIN.—Is of Catherine II., Empress of Russia; no value.—Bkrkardin.

(1863.1— PASTILLES. —Take Sdrm. of caacarilla bark, ii.inn. of gum benzoin, Sdrm. of sty rax. 2drm. of olibanum, ..',).'. of charcoal, Udriu. of nitric, and a sufficient quantity of mucilBge of tragacanth. Powder the Bubstances and form into a thick paste with the mucilage, and divide into small cones; dry them until quite hard in a slow oveu.—Minnehaha.

[38631—PASTILLES.—"W. R, C." asks for some recipes for fumigating pastilles; I send the following, copied from a book which 1 believe can be relied ou, but not proven on account of the difficulty of o'itainingone or more of the components:— Pastiles i la rose Essence of roses 1 part, nitre 9 parts, gum 12, tears of u'il>anum 12, tears of sEorax 12, powder of roses 16, chare xtl 60; powder the solids very fine, and make a paste with gim tragacanth, 2 parts dissolved in i osewater 36.— Pastilles a lii-Vanille: Gum gaibanum 25 parts, tears of olibanum 25, teara of storax 25, uitre 25, cloves 25, vanilla 35, charcoal 115—make paste as above.—Orange Flower Pastilles: Nerolil part, nitre 9, galtbauura 13, tears ofohbanum 12, tears of storax 11, pare orange powder 12, charcoal 70, reduce to fine powder, and make paste with gum tragacaath 2, dissolved in orange-flower water 15, and rose water 17 parts.— Lastly, but hardly fit for a sick room, Explosive Pastilles: Make a hole at buse> of pastille and fill with gunpowder. I am afraid the queer names of these fragrant resins will almost frighten the querist; but 1 believe all except tears of storax and neroli can be bought in penny • worths at the druggist's; if one shop does not keep them, try another. They say that tears of storax have not been ia the English market for vears, but I believe the liquid storax will answer the purpose. By the word '"tears" is meant the drops of resin in that shape, but of course the lumps will do as well. Orange and rose powder I take to raeau powdered orange and rose flowers. Neroli is the essential oil of orange flowers. I will now give a simpler way for fumigating, but which has this objection, that everybody does not like the perfume. Dip brown paper till quite soaked in a sttpng solution of nitre; then, when perfectly dry, rub over tt a varnish made by dissolving either or both gum olibanum (frankincense), and gum benzoin this soon dries aud Ib ready for use; this last I have done myself, and aucCeeded in getting a strong fumigant. -H W. Bishop.

[3371]-THROTTLE VALVE.-l send for "Grocer's" benefit a full size drawing above of one 1 put to an engine of •f* cylinder. The same thing reduced to J gits barrel which measures say J inside and the casting bored to 1" would do tor a 1 h p. eugine. The lower sectiou of pipe is screwed and braied into wrought iron flinge and faced oif iu the lathe 'icing a siiort length altogether, tuc upper flange cas; iron '*ppcd for barrel, which ia screwed, m with white lead. The intermediate piece, is Jike a pulley with l^rge hole through, '.nd very deep gro av with a piece stuck m the pattern atuue

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side to be bored out to make aiuJiag box, and a small boss opposite side to prevent spindle hule coming through, all bolted together with 3 bolts. These are prevented from turning by threeflats died on edge of moulding on casting as shown on plan, Fig. 3. The valve is cast with two tails for centering m the lathe, and a finishing cut taken with the slide rest to exact diameter of valve case. See Fig. 4. To get it out in case of wanting repair, slack nuts \ turn, and let a little steam on, then takeout bolts, and all comes asunder. You need not cut off the tails from valve if they are not long enough to gain when valve is full open, which it would be bv moving 3U°.—J. K. P.

[3366 J—LATHE AND ITS USES.—For the information of G. Fluckburn, the universal cntter spindle of which he speaks works or rotates in two internal hardened steel cones, the two ends of the spindle being external. The square bar which fits into the receptacle of slido rest of a 5-in. centre lathe Holtzapffel'a standard is 9 l-6th square and v.; long. Perhaps I might add that I have arranged and now make a far superior instrument for mmplicit , effectiveness, and durability than the one represented in Vol. V., p. 202, Fig. 256, and do hope before long to give the Enqlish Mechanic a representation and description of it.—Edwin Baker.

[3867.1-LATHE DIVIDING PLATE.—If " R," requires a ready reckoner to assist in working the above, I sball be happy to make him a present of one for that purpose, if he will let me know hie address.— Ed WIS Baker, 13 aud 14, Mount-street, Grosvenor-square, \V.

[3867]-LATHE DIVIDING PLATE —If you look at p. 12 of present volume, you will see a counting index figured and described in connection with the wheel cutting engine. It is not very troublesome to tit up, and need not be self acting.—J. K. P.

[38fi8.]-WATERPROOFING CLOTH.—Make a solution ofindia rubber in naphtha, and apply it to tbe cloth; this is the article used for waterproof coats; add a little linseed oil to it. If tliis is not suitable to "A. S. A." I can send a (ew other recipes.—Skmpkr Paratus.

[3809J-WEIGHT OF WATER. -The reply to " Countryman's" query is very simple. By a rule in hydrostatics, any body immersed in water is pressed by the weight of a column of water tbe height of a perpendicular drawn from the centre of gravity of the body to the surface of the liquid, and in breadth equal to the cross section of the body. A rnle to calculate tbe pressure on the bucket may be stated thus: for every 7ft. of depth allow 31b. pressure per square inch.— A BouniiKV.

[3389.;)—WEIGHT OF WATER.—It is said that any heavy body 201b. iu weight, taken to the top ot a mountain 3 miles high, loses but fco2. in weight . therefore tbe difference in weight of a bucket of water at the top and bottom of a well 90ft. deep, must be indeed slight. The apparent difference is, 1 think, due to the weight of the rope when the bucket is at the bottom.—Harry G. Newton.

[3373.]—BOOKBINDERS' GLUE.—Bookhinders use the same glue as carpenters and joiners, but break up the cakes into small pieces, aud soak them in water for 8 or 10 hours, then thoroughly melt them in au iron or earthenware pot before using iu tbe glue pot [ some add treacle when using it for cloth work; some. ;idd paste. There is a work called "Bibliopegia," I think ic is by Arnoft. 1 do not know tbe publisher, but if " Aristotle " wilt insert his queries in " our" Mkcuanic, they will receive prompt attention from—An Initio.

[:js74.]— CONSTELLATION.—The group ** Aristotle" sketched is the Pleiades, as he will at once perceive ou a

closer look at the group on page G3 of " F.R.A.S.'s" maps. He wants a sketch of the Pleiades t 1 refer him to his own on page 2JS of present vol.—H. W. Bishop.

[3876.]—TOOL FOR TURNING PIVOTS.—The latest tool for turning pivots is the French tnrnbench, with 8 centres and a small slide rest. They are from 10s. 6d. each and upwards.—S. Tanenbkro, Leeds.

[3878.]—DAILY TEN O'CLOCK TIME SIGNAL.—Yes; all wires from I mm. to 10 o'clock to 1 mm. after 10 are in connection with Greenwich clock, when all working is suspended for that time.—A Telegraph Clerk.

[8879.]—GINGER BEER,—White sugar lolb., lemon juice 9oz., honey lib., bruised ginger lloz., water 9gaL Boil the ginger in lfcgal. of water for half an hour, then add the sugar, juice, aud honey, with the remainder of the water, and strain through a cloth. When cold add the white of one egg and in.'., of essence of lemon j after standing 1 days bottle. —(Extracted.)—Minnehaha.

[3897.]-NAPOLEON,—I beg to inform " H. B.", p. 231, that his coin of the Freuch Republic, 1848, is not worth much more than its weight in gold. If it is, as I euppose, a 20 franc piece, its intrinsic value is 15s. lO^d. in our monev.— Henry W. Henerky, M.N.S., fee., &c.

[3900.] — ASPHALTS FOR ROOFING, &c. — I would advise " Dublin Printer " to try the following; he will find it useful in stopping many a crack besides those in his roof:— Take 2 parts by weight of common pitch with 1 part of gutla percha, melt together in an iron pot: it forms a homogeneous fluid much more manageable than gutta percha alone. Now to repair his gutters, carefully clean out of the cracks all earthy matters, slightly warm the edges with a plumber's soldering iron, then pour the cement iu a fluid state upon the cracks while hot, ftuishing np by going over the cement with a moderately hot iron, Bo as to make a good connection and a smoo'h joint. The above will repair zinc, lead, or iron putters, and is a good cement for aquariums.—Patience Am) Perseverance.

[;J907.]-UNIVERSITY EX.\MINAT10N3.-London, 1871Special subjects.—1st B.A., Latin, Tacitus, "Annals," Book I.; Virgil, ■' jfineid," Books VII. and VIII. English, History of English Literature during 17th Century; Bacon, "Eaaavs;" Shakespeare, "J ulius Cmsar;" Dryden, " Annus Mirabitis . " and " Ahsalon and Achitophcl, " French, English, pi'st and preseut. It "Xantbos" will write tome, I will give him any information he may require upon this subject. C. H. W. B.

[3908.]—OLD COPPER COIN.—In answer to Mr. Nash, p. 1239, ttie inscription on bis coin is FAVaTINA AVGVSTA (Faustina Empress). I cannot say wttnout seeing the coin whether it was struck by Uie elder Faustina, wife of Antoninus Pius, horn Ad. 105, died A.d. 141, or by the younger Faustina, wifeo' Marcus Aurelius.dieu A.d. 17a. The brouze c.iios of both arc common, and worth very little.— Henry W. Hen»rsi, M.N.S., &c.

CniNESE VACCINATION—It may be news to some that the Chinese commenced to practise vaccination for the amall-pjx at Canton forty years ago. There are now public vaccinators at rekia with regular days and hours lor scarifying infanta brought to them, just as in London. When their supply of Tacclne lymph falls short, it Is renewed troui the English missionary h ispitaL .^i,

NOTES AND QUERIES.

[3910.}—CONICAL WINDING DRUMS. - Will some brother reader kindly give some particular* respecting the construction and working of conical or spiral drums, us applied at collieries for drawing coals, and state wbat conditions are to be observed in order to ensure their safe working ?-W. M.,Junr.

[.»11.]-GALVAN1C CELL.—I have t galvanic cell, composed of a stick of what I suppose to be carbon (it is black, about 5in. long, and lin. square) in a porous cylinder tarrounded by a zinc cylinder about Sin. in diameter, alt in a class vessel. Will any of jour readers kindly inform me what liquid or solution 1 should use to excite it ■, also the name of tbc combination, and whether it is best adapted for strength or coniLancy ?—Hermit.

[3912]-RKVOLVING FRAME FOR SHOP WINDOWS. —1 wish to construct a revolving frame to show pictures in n shop window, and find the ordinary meat-jack clumsy; it revolves too rapidly at times, and requires winding up during the day; I should like also bit avoid the return motion. Can any of your correspondents help me?—Pitman.

[39130—TO A. STRINGER.—In He* M9 A. Stringer writes on velocipede construction ; will hs kindly, far my own and the information of others, insert a plan with the details of the three-wheeler he speaks of steered like a boat; will he also say where 1 can purchase an "English" velocipede '-—conStant Subscriber.

[SVU.V-WOOD ENGRAVING. — I should feel greatly obliged if any brother subscriber can tell me where to obtain the best book of instruction in the above art, and the price? —K. T. Z.

[3915.]—NAIL BAGS.—I have a large quantity of nail bag* which are worn out, for what purpose will they serve; will they do for making paper, or must I consign ihem to the nibbish'heap?— W. Cattzll.

[3916.1 -PAINTING BOILER.—How can I mix a good green paint to paint the boiler of an engine so as the neat may not effect It ?—A. W.

[39170—ICE CHEST. — ICES.—Perhaps some of my fellow subscribers will tell me the best plan for making au ice chest (a few sketches would be a great assistance); also a few instructions for masnog ices?—Brighton Sub.

[8918.—ENAMEL.—Can any of my numerous brother readers inform me how to make white English glass, or the tin enamel, as made in Prance, that given a few weeks back was not white or good; also where I could obtain a brush for painting figures and letters on clock and timpiece dials ?— Anxious Inquirer.

FWl9.]-GALVANIC BAND.—TO "SUFFOLK AMATEUR."-1 have very carefully made a galvanic band after the plan of " Suffolk Amateur," p. 11, last vol., I have tested it with a small galvanometer, but cannot get the slightest current from it. I have made it as follows :—A strip of copper and one of zinc, 18in. long, lin. broad, and 1-3-th in. thick, are united at the ends by small copper rivets, I have lapped over these rivets with thread, and varnished over the thread with shellac in alchohol, the ends are left bare ljin., the copper and sine are tapped" spirally round with a piece of cotton list lin. broad, and covered in a bag of oil skin; I tried all strengths of vinegar, but to no purpose. Would "Suffolk Amateur" kindly say where I have failed?—W. A.

[392 :■ "/-MEASURING LIVE STOCK—Will some of your learned correspondents inform me If their is a book, published on measuring live stock, say an ox; or give a rule, through the medium of our Mechanic, to measure a living fourfooted animal so as to find its weight?—A Countrtmah.

[3921.]—BRASS COIN.—I haves brass coin the sire of s penny, on the obverse the bust of a man, on the reverse a female in chariot drawn by four elephants with LIE over them, there is an inscription round the bust, but the only letters I can make out arc ALT—PAIANC. I should like to know of what coin it is, and of what value ?—Tom C. HolloWat.

[3922.}-REMOVING PAINT.-Although some answers h ave appeared in reply to inquiries for a good alkali or such method for removing paint, still not one effectual mode has been suggested. If any brother reader could advice a ready and effectual method of softening the old paint on dorrs. See . when ii becomes thick and hard, so as to remove it speedily (without the use of charcoal fire), and enable the operator to clean off mouldings with credit, it would be a very useful enlightenment?— House Painter.

[39230 — GEOMETRICAL DRAWING. — A method of drawing the ellipses that represent circles—N.B.— When the dimensions are not reduced to geometrical proportion ; if one can also recommend a good cheap work on the above ?—Carl J. H. Cotthesson.

[3924]—SILENT PANS,—Can any of our readers tell me the diameter of tbc blade of one of Messrs. C Schiele and Co's 50in. Excelsior silent fans, patented 1863 P—One Who Wants To Ouw,

[3925] - POSITION OF MAGNETIC POLK — Can any of our readers inform me whether, as the declination of a needle is the angle made by the magnetic and geographical meridians of any place, and the magnetic meridian passes through the magnetic poles, when the declination alters does the position of the magnet pole change with it ?— Vibrator.

[3926.}—FORCING WATER.—An engine forces wster through a 9in. pipe, perpendicular, to s height of 30ft., will it require the same power to force it to the same height through a Sin. pipe, but such height being 180ft. away, with a gradual ascent of 10. in 6ft. ?—B. S. M. G. II.

[3v37-]—WINDOW PAINTING.—I shall be very grateful to any at your readers who will tell me of a rich transparent

I permanent crimson; also a pure bright yellow? Crimson ake is such a varnishing colour it will not bear continued exposure to daylight, the colours are to be nsed with oil and varnish for glass painting. Amongst all the varied and valuable information contained in vour journal, I have never noticed any on the old net of window painting, I do not rican the modern process of staining, I nave been a painter of dissolving views for years, but I should be most thankful if you could assist roe in the former matter.—Sab Lb,

[3928 ]-RE-MANUFACTURING INDIA RUBBER. —Will some reader kindly tell me if india rubber of first-class quality, in sheets of {in. thick and under, could be re-manuI artured, and what it would be worth per pound?—J. T

iiHU9 ]-EHIGRATION.—I should be pleased to get all the information 1 could respecting New Zealand and Tasma

nia, as places suitable to make a home in, particularly as to peculiarities of climate, soil, productions, reptiles, insects, kc., if any insects to give much annoyance like the mosquitoes or gallmippers of the Southern States, U.S., whicli I have suffered considerably from, I reckon. I do not wish to go where it is very hot, but a little milder winter than our own, with its cold dull weather and piercing easterly winds. Perhaps our kind friend "F.R.G.S." would oblige.—TasMania.

[3930.KWINES, JA1I8, PICKLES AND PRESERVES.— Can any of your readers inform me if there is any practical work on making wiues, and also a book on manufacturing jams and pickles. 1 have one, but it is of little use for a new beginner.—Fran ens Brown.

[3931.)—INDIA RUBBER SOLUTION. — Will any of your obliging correspondents, "Sigma."for instance, tell me of what the india rubber solution for mending waterproof clothing is composed, and the proportions of each material. Also whether there is any solvent for silk, which on evaporation leaves the tliread without decomposition'— Alei Ia Browning.

[3932.}— BICYCLE RUBBER TIERS.—I intend fitting an india rubber tier to the driving; wheel of my bicycle, could any brother subscriber kindly assist me in the fixing? I do not want to remove the iron tier; should also like a practical opinion of the merits of the rubber tiers, best shape, depth, kc.?—C. Mortimer.

[3933.]—HYPOPHOSPHITE OF IRON AND QUININE.— Will any brother reader kindly inform me of the medicinal properties, doses, and cost of the above preparation of iron and quinine?—May.

r3934.]-ORGAN ACCORDION STAND.—Will any fellow subscriber furnish mo with a diagram for the construction of the above, so that it may be played with both hands—the feet, by means of a pedal, giving necessary action to the

belloWB P—SlGMATAU.

[39360-DISSOLV1NG SHEEP'S HORNS.—Could any of your numerous readers inform me how, or in whnt way, I conld dissolve sheep's horns to make them into glue, size, kc., or for any manufacturing purposes ?—Vert Old SubScriber.

[303c.}—FAST COLOUR FOR SHEEPSKINS.—Will one of your readers kindly inform me how to dye the wool of sheepskins (fast colour) without iujury to the pelts?— W. C. 8.

[39370 — CHEMICAL QUERY. — SOOgrms of liquid niLrous oxide are gradually warmed to a temperature of 0°C, the barometer standing at 760mm. Wh»t volume will the gas occupy? Will E. G. Davis, " Urban," or some other frieud kindly answer the above, and also show the way in which the answer is got?— Zeta.

[3938]—AMERICAN CLOTH BAG.—Having to use in the course of my business a large light tight bag, made of American cloth (being light and cheap) I find it answer when the weather is warm, but when cold the enamel chips or peels off, and is soon useless, will any reader tell me how I can prevent this?— Peterboro.

[39390—ELECTROTYPING.—Will any one please inform me how to take electrotype impressions in brass or in any other inexpensive metal harder than copper?—Herbert.

[3910]—THREE-WHEELED VELOCE.—I am making a three-wheeled veloce for two to ride, and to drive off the front wheel as in bicycles, and of hind axle with levers. 1 am ata loss to know how to make the hind wheels loose on the axle in turning a corner, as I am afraid if both fast on one axle it would be very bad to turn. Will any reader give an opinion on the following method, or suggest a better one? a if the back end of the nave, b is the axle, a section of, c is

[graphic]

a projection on that axle, d is a projection on the end of the nave, so that the projection on the axle will drive the wheel by it on going round a corner. I think d on the outside wheel would leave c on the axle going at the speed of the inside wheel. It is on the principle of a lathe driver.— T. T. M.

[S9tl.J-MARKING INK.-Can any one tell me how best to use printers' type and press with marking ink, for marking linen, clothes, ke. My difficulty is how to get the marking ink on the type neither too much nor too little.—Daisy.

[3942.]—MAKING BUTf£R.-Will "Scorpio," or some other reader be good enough to explain more fully the method on p. 213, Does it not involve the digging of a pit, then filliog and then re-diggiug? Has any condition of ground to be attended to. What materials are the sacks made of?— Ohio.

[3943.]—BEKS.—I have a hive of comb in which a swarm died last winter. Can any of your readers tell me is I may safely hive a coming swarm into it this summer, I may mention the hive is a common straw one with a wooden box under it quite full of comb, and is 3 years old. I feel doubtful in consequence of the comb being apparently dirty; it appears on the outside quite black, though 1 see no SDpearauce of mould. Would it do to remove any of the comb to make room for the new swarm, as it is quite full. Some hints on the general management of bees by a practical bee keeper might prove interesting to many of your readers, as they would to roe.—8. W.

[39H.]-ARITHMETICAL QUESTION.—Will Mr. J. Sharp, who answered query No. 371u, p. 213, kindly sliow how it can be proved that a circle is equal to s parallelogram whose length is equal to half the circumference, and breadth eqnal to half the diameter. If he cau prove it by geometry, will he kindlyda sor-T. J. O. C

[3945.}-PAlNT FOR BOATS.-Would any reader inform me how to mix a hronte or copper-coloured paint for the bottom of a small model bout?—A Model Boat Maeer.

[3W6.1-SYRUPOF HYPOPHOSPU1TE.— If any medical correspondent wilt inform me of the mcdicil uses and cost of syrup of hypophospblte of iron and quinine, together with the dose for ailments in which it is beneficial, I shall feel greatly obliged ?—G. Thick.

[3917.]—REMKLTING HARD WHITE PAINT.— How shall I remelt hard white paint, shelled off. coin posed probably of white lead boiled oil, and litharge—

[3948]-rNDlA-RUBBER TYRES.-If some correspondent, who has had experience with india-rubber tires, on velocipede wheels, would answer a few questions respecting- them, they would oblige a number of readers who are Interested in velocipedes Where they can be obtained, and price f" The beet way of fastening them on, and should they be need with iron tires? How long they last? How are they astened on the " Phantom*1 wheels ?—G. K.

[89*9.}—GUYANA.—Where is situated the Republic of Guyana? A few particulars will oblige.—Jouk D

[3950.]-OOMUTUB FIBRE.-I find in a Dublin paper

that the bristles imported for tbc purpose of making brooms for sweeping the'streets, come from the Arenga or Gotnuto palm. Is this not an errsr V— Gomoto.

[3951.]-ltAaIBOO NUTS.—I wish to know what kind of nuts are the " Bum boo uuts," I find mentioned in the circular of Messrs. Mandy, Hurley :md Co., last number of our Mecuamc, and what is the use of those nuts*—•Gaoaatti.

[3952.]—LOAM PANS— Having some of these to make occasionally, and much annoyed with them veining inside, I shall feel obliged if any of our brother readers, having practical experience in moulding the same, will inform me the cause and remedy.—Inquirer.

[3953.]—COIL—As I am afraid I have annoyed Mr. A- K. Tucker more than I ought, perhaps M Sigma" would kindly answer me one or two queries. I quite forgot to state formerly that I intended making my coil in four sections What Wmiu be the best way to connect them at the discs. I can almost fancy from " Sigma's"notein[the last number|of the Mechanic that there is a possibility of doing without so much gutta percha paper, as I see recommended by everyone. 1 oaly hope tie may show me how to begin, I'll be a willing pupiL I have taken Mr. Tucker's advice, and intend putting bib. No. &> wire instead of 41b ; will " Sigma" also say if I should got the new double mercury break instead of Mr. Lid da spring break. I may state here that my old coil had s core \ instead of tin., as put in my note. (Tins is in reference to Mr. E. Tucker's reply to my last query, which I have to thank him for.)—1). Fobbks.

[S954.J — SCREW AND WHEEL CUTTING LATHE.—Would "J. K. P." or any of your numerous correspondents kindly give me their opinion on the following .— I am going to have a 4iin. back-geared self-acting screw and wheel-cutting lathe made express!? for me, and I want it to be as near to perfection as possible without being too complicated. 1. Would a3ft. din. bedim, across be the aize (please give all the other dimensions) ? I should like it that length. 2. What size and rate should the screw be which goes inside the bed? it must be inside, S. What size should the mandrel be, and wbat length ; it a \ thread the right size to be as strong as necessary? 4. What sue and uuuvier of teeth should the back gear wheels and pinions be'- 0. The slide rest must .have self-acting surfacing motion, what length should the bottom slide be. what length the top one, ana what is the best form of tool holder for the slide rest'; G. What is the best wbeel-cuUine; apparatus to fitin theshde rest to cut wheels up to SJin. in d'S^ifte*- r The moat approred plan, I believe, for dividing the head is s tangent wheel fixed to the mandrel, and the screw which turns it to have a hand and dial; or is the rows of holes the best after alL-P. >". Has Luck.

[3955]-SCALK PARAFFIN.—Canany of your readers inform me how many tons ot scale paraflin are produced in Scotland in one year ?— S. P.

[3956.]-CHEMICAL.—Will Mr. G. E. Davis bsso kind as to show how 1 could calculate the weight in grammes of I litre of methyl gas at 20°C. and 760mm. pressure; sad also how to prepitre acetic acid from the following i CibUI, ttjO, CaO, 11,304, K,Cr04, Na,COa?-IL TsasnT.

[8957]—POWKHS OF NUMBERS.—Will Mr. Biggs, or some otber contributor to our valuable paper, be kind enough to inform me bow numbers are raised to their 3*6tb and to their l'7tb powers. Take No. 10 for instance, to tbc 36th power 8982. how is it done?— Ecokomt.

[3958.]—NAMES OF PARTS OF BKLLOWS.—Would any maker of Revertc's bellows and hearths, be kind enough to give me the names, separately, of all parts of bellows, such as is used in a ship buildiug yard ?—K. Fowler

[3959]—THE "EDINBURGH" VELOCIPEDE.—Will any brother subscriber give the address of the maker of the "Edinburgh" velocipede?—C. T. •

[3960.]—THE BLOOD.-I beg to ask through your valuable journal, if some kind reader would give me a recipe (cheap) for purifying the blood?—J. G. Jackson.

[3961.}— BISULPHIDE OF CARBON PRISM.— Will any brother reader state what cement will resist the action of bisulphide of carbon? I have mads a prism, bnt the bisulphide dissolves all the cements 1 have tried ?—E. C. MlIBBAl.

[3962]-WlTITE LEAD.—I bought some stuff for "white lend genuine," but find it has all dried up. like old putty, although at first it looked like ordinary white lead* and has been kept covered up in water; how is this r II

[3963]-OAK, WALNUT, AND MAHOGANY STAINS. —Would some reader supply me with recipes for making oak, walnut, and mahogany stains?—Zkkila.

[3964]—CAST IRON FOR TURNING.—I should be much obliged to '* J. K. P." If he would give mc a few bints about preparing- cast iron for turning and filing, whether by chipping or pickling it. If the former, 1 should like to know the shape of chisel, and mode of using. If pickling be the better way, I wish to know the Htrength of acid, and time of dnratlon of using it. 1 should also be much obliged by advice as to rebroaziug a snedai. It is one of a case of Napoleon medals, and tbc colour has been taken off by my attempting'a cant In wax for eleetretyping, leaving It a dull leaden oolour. I should like to know ho w to get a cast from It for electro typing, as wax stioks to the metal and breaks. Plaster of Paris makes a protty good one, but 1 do not know how to make It conduct ing, as the plumbago wlU not adhere.—Fabek.

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