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trees or their roots might be employed as filterers around wells suspected of impurity by the percolation of foul matters into the water within them.

I can inform our friend "Bernardin," that a few months ago I saw in a scientific and optician's shop nearly opposite Effingham Wilson's, Royal Exchange, London, some recent photos of Australian scenery, including an "Eucalyptus. Over Sixty" had better invest in a "Macclesfield" tricycle, which is much cheaper and more easily worked by an elderly man than the "Edinburgh," which occupies a great space, and is actuated by the legs solely. The steering, which cannot be clearly seen from a photo cr drawing, is managed by two broad crossed straps attached to the front axles and the short levers on either side of the graceful vehicle. 1 congratulate you on the varied improvements in our journal. P. FRANCE, Harrington-street, Liverpool.

MR. BEARDSLEY'S DYNAMICS. SIR,-It appears that Mr. Proctor and myself are at issue on a particular subject-namely, upon one branch of dynamics (or of the laws and properties of matter in motion), and he declares me to be "ignorant of the fundamental laws of dynamics." Cannot Mr. Proctor afford to be rather charitable than hostile? Cannot be find more pleasure in convincing me I am in error, than in fighting me in the dark at (according to his own showing) a disadvantage? Thousands of your readers can substantiate my assertion on page 90, but it must be borne in mind we must not tie ourselves hand and foot, as it were, to the so-called laws, brought into existence from necessity at the time other theories were advanced, and which I shall at a future time require to notice. I will not waste your valuable space further than to say I have done as Mr. Proctor beseeches me not to do. hundreds of times, and find that the moment the feet touch the ground it is necessary to put the body in a slanting attitude to resist as far as possible the principle I named, arising from the forward motion of the train, and even after this precaution had been taken, found it necessary to put the feet into very nimble action. I must, therefore, "beseech" him in turn, rather than adopt an uncharitable course in condemning me as ignorant, to prove me to be so, and I will at once lower my sword, and tender him my thanks. I shall also thank him to point out when, where, and by what arguments Galileo laughed away what he is pleased to call my " puerile" objections about the earth's atmosphere.

JOHN BEARDSLEY.

THE PHANTOM" WHEEL. SIR,-Having examined Mr. Tydeman's letter at p. 385 of Vol III, in which, according to his further letter which appeared in the MECHANIC, a fortnight since, he describes a wheel "of a precisely similar to that made and advertised by this company. kind I now beg to offer that gentleman a simple denial of the identity; and, I think I may add, of the similarity of the two manufactures. The only point in respect to which the two wheels may be spoken of in the same connection is that both are "suspended" wheels. There is no novelty, however, as to the suspension, and we have never claimed any. That is a comparatively old affair; Theodore Jones's patent for it was issued in 1826.

Your correspondent is emphatic upon the point that the failures and defects of the "Spider" wheel are inseparable from, and are part of the suspension principle; and, whether intentionally or no, he leaves the impression on the minds of some, at least, of your readers-the two wheels being already rather dogmatically declared to be of a "precisely similar kind "-that the " Phantom" wheel must be certainly as useless as the Spider turned out to be.

The object sought to be attained in a suspended wheel is to make it sustain a weight in motion in such a way as to lessen the degree of traction required on ordinary roads. This is effected by hanging the axle in the centre of what I will call a continuous arch, or a circular spring, which, altering its arc, and the portions of its abutments to a degree nicely adjusted to the weight of the load, the velocity of the motion, and the nature of the road, keeps the axle or load as nearly as may be at a level with the line of the road. To effect this, the material of the arch or circular spring must be of an elastic, and yet very strong, nature; something capable of receiving, distributing, and ab sorbing rather than of resisting concussion. The arch must be made so as to bend in as a whole, and yet be unyielding in its parts. Its dimensions and substance should be well adapted to its work, and the principle of its construction should be such as to ensure the strain being distributed as evenly as possible over its whole area or circumference. A suspended wheel might be formed of a mere hoop of bamboo or cane, with four strings attached to it at equal distances, and joined to a stock in the centre. Such a wheel, however, would not do for serious work, because it would fail to comply with any one of the conditions I have just mentoned. The bamboo or cane would not stand continued concussion, and the weight of the load could not be fairly distributed over the whole of the circumference from so few points of suspension; the strain would be unequal, and would tend to pull the hoop into a square shape by bending it outwards at the points midway between the attachments of the strings to the rim. If, instead of only four there were eight suspending strings, the strain would be better distributed, as it would tend to make the circle into an octagon, and so on according to the number of points from which the rim would be held in towards the centre of the wheel. The hoop could of course be made superior to any strain whatever, even with only four suspending strings; and, on the other hand, it might be made so light and springy, as to require to be held in at every inch of its circumference by suspending rods. In either case the wheel would not be elastic, and nothing would be gained by the suspension principle so applied. The happy mean required is the adaptation of the material and the proportioning of the diameter and strength of the rim, and the number and strength of the suspending rods to the work required of the wheel, so that each part of the structure shall have its fair share

of the load assigned to it, and no more. The wheel, as a whole, must be elastie enough to give to inequalities of the surface of the road, and yet strong enough to recover and retain a perfectly circular shape where the road is good and smooth.

It seems to me that Mr. Tydeman began badly by making his rim or arch in bad proportions, and that he then failed to properly retain or keep it in shape by a sufficient number of suspending rods. A lin. stee tube formed a circle 6ft. in diameter, held in by wire rods Him. apart from each other on the rim; thus what I will call the segments of his arch, the spaces between his suspending rods, were not far from flat at starting, The tubular shape of the rim did not improve its elasticity, and whatever it had of that quality, must have been soon destroyed by the "ammer, 'ammer, 'ammer, on the 'ard 'igh road which the cabman in Punch speaks of. The rim was too weak and slender as compared with its diameter, and it had far too little, or at any rate too widely separated, help from the very few suspending rods,

"

In a Phantom "wheel, of half the diameter of Mr. Tydeman's, we use a continuous rim of American elm, Iron eyes with stems, in. thick pass 16

lin. square.

3

through this rim, and are fastened on the outside of it, and through these eyes, which are only about 6in. apart, sixteen pairs of suspending rods are passed to be held in the stock in the way your readers may see by referring to our woodcut. The rim is, under any circumstance, such as that of being over-weighed, prevented from altering its shape to an injurious extent.

Mr. Tydeman says that the suspending wires of the "Spider" broke too readily on being struck laterally. No wonder. They were only -in. black steel, in

3

10

lengths of 34in. each. The suspending rods of the "Phantom" are in pairs, each - thick, and only 16in. long,; they are made, too, of a mild tempered steel, prepared purposely for the job.

16

Further, the passing of the steel rods through the steel rim ofthe "Spider." weakened it, and led to flattening at those points. This can hardly be the true cause of the flattening, I faucy. If the rim flattened in at the rods it must have bent outwards where there were no rods; it would therefore, apparently, have been stronger at the rods. The flattening, however, was in all probability due to the causes I have already referred to, and I can only emphatically deny that it is at all the case with our wheel.

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ball possessed of magnetic polarity, acted on, and being acted on by other magnetic bodies.

But it may be said that this only shows that the earth may be a long cylinder instead of a flat surface. Granted; but what sort of advantage would this idea be, having all the supposed evil consequences of the globular theory without one of its advantages. Nothing, however, is easier than to prove that the earth is not a cylinder. If sailing east or west we carry an accurate watch with us, it will continue to show us the time at the place we left; we soon find it does not show us the time at the place we have reached. If we are on the equator, we find that when we have thus sailed 900 geographical miles, there is a difference of one hour, and this being one twenty-fourth of a day, is also the same proportion of the earth's circumference; or treating it as an abstract circle, divided into 360 parts, it is 15 of these; that is, the difference of longitude is 15 degrees, the difference of time, 1 hour, the period during which this part of the circumference passes under the sun. But if we try this at another part, the case is quite different; the more distant we are from the equator, the less space we require to travel to make the difference of one hour; that is to say, the circles parallel to the equator diminish in actual length, and the cylinder on which they would be all equal passes into a globe.

Hence, strange as it may seem, the nearest way to a place due north or south, is to follow that line; but it is not so with a place due east or west, except at the equator. In the north we must follow a curve tending first north for half the distance, and then south; south of the equator, the reverse. This is what is called Great Circle sailing, and depends upon the fact that the shortest line between two points on a sphere is one which, if carried through, would cut the sphere into two equal parts. This is called a great circle. On the earth, a the north and south lines, or parallels of longitude, as they are called, though converging, are such; but of east and west lines, only the equator.

Time and space, the only realities or infinities, bythe-bye, require me to conclude for the present.

STRENGTH OF CHAINS.

SIGMA.

SIR, I wish to call Mr. A. Tollausen's attention to his rules on the tenacity of chaius, which I will endeavour to prove wrong both in working and applica

tion. If a rule be correct the strain will be the same for same size of chain whether you work from a rule giving 8ths or 16ths.

In example a (by rule 1) the working out is incorrect. Here Mr. A. T. has it d = 814 = 112

J. A. MAYS, Secretary and Manager, the "Phantom
Veloce and Carriage Wheel Company, Limited, 10,
King-street, Tower-hill, London, E.C., 21st April, whereas
1870.

THE EARTH'S FORM.

Mr.

SIR,-It is no tempting task to take up and reply to the wretched stuff which Mr. Beardsley is inflicting on your readers. In common with "Parallax," Hampden, and all the others of his tribe, he sets forth as facts things which have no existence as facts; he of course puts into the mouths of the orthodox, opinions which they do not hold, and, as a necessary consequence, his deductions from the one, and his ridicule of the other, are both erroneous and delusive. The arguments" we have been favoured with, being within the compass of any half-trained schoolboy, will probably find plenty to answer them. My purpose is to give one or two on the other side-to set forth a real fact or two, which must first find an explanation before the globular form of the earth can even be doubted. First, if the earth be not round, how is it we manage to go round the earth; that is to say, if the earth be one continuous plane, by what conceivable process is it that by going steadily on in a straight line we come back to the point from which we started? Secondly, if the earth be a continuous plane, where does it end, and in what, 'and what is it built on and supported by, as we are invited to abandon the theory of central gravitation, linked up with that of the spherical form of the earth?

To show that I do not speak without authority, I may say that I hold a certificate from examiners that "I was a correct and able navigator" and that I have myself been "round the world," as well as up and down and round about in many ways. I once, after being two months out of sight of land, sent a man aloft to look in a particular direction for an island, and in half an hour he called out "Land Ho." Now will any one in; his senses suppose that this would be possible if the doctrine on which we work were so fundamentally wrong that the world on which we travel is utterly different in form to what we suppose? We do not chatter nonsense, we know that starting from England, we may sail west to America, cross that continent, go still west to Japan, China, India, and home, always westing, by the overland route. We know that we sail eastward to the Cape, to Australia, eastward still round the Horu, home again, coming north on our return as much as we went south on our outward voyage. We know also that if two people started a: the same time on such journeys, and returned on the same day, on comparing time, one would have lived two days longer than the other in the same time; for one, prolonging each day by accompanying the sun, would in the complete journey have thus dissipated one day; while the other, going always to meet the rising sun, would have seen it rise and set once oftener than if he had remained in one spot.

It is true that in travelling over a wide plain, it is quite possible to keep going round and find oneself where qne started. I have done it myself on a cloudy day, but it would be impossible if one kept a straight line, or went by compass; for even if we imagine that the sun, instead of following an apparent straight path, due actually to the world's own rotation, winds round the circumference of a great plane, a motion somewhat hard to reconcile with facts, and that we thus follow it and return to our starting poing, we have still to get over the magnet, and explain how it guides us in this extraordinary circular course, a thing perfectly easy to understand by those who know the earth to be a

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32 32

16 4 32

5

41 tons 4 correct answer as by rule 1, and not 4 tons, as Mr. A. T. shows it; for according to rule applicable to weight, hence a multiplier or divisor for 8ths being 8, areas of circles, a chain twice the size is four times the of rule as applied in foregoing examples. must for 16ths be 8 x 4 = 32, proving the correctness

ropes, which are also incorrect. I am sorry to see Mr. A. T.'s remarks respecting I think he might with advantage have given us the modern experience of Huddart or Chapman in preference to Du Haunts 130 years ago. As, however, his remarks on this part of the subject seem unfinished, I forbear saying anything further at present, as my desire is only to put matters and trust this will be received as given, correctly for the benefit of your numerous patrons,

W. H. LAIDLER, Edward-street, Bow Common, E.

SILVERING SPECULA. SIR. About three months ago I commenced the grinding of a speculum for a telescope of the Newtonian form, and following the admirable directions given in your columns by your able correspondent Mr. Purkiss, I believe I have succeeded, only I have not been able to get it tried as yet. I have likewise made a diagonal plane of a piece cfine plate glass, as recommended by the same writer, This I have attempted to silver by the Rochelle salt method, described in the MECHANIC some time ago, but have not been successful as yet. I have attempted this method in preference to that one described by Browning, as I see some of your correspondents have succeeded well with it. Mr. Thomas Woodruffe, p. 17, Vol. IX., says it is "quite equal to Browning's at one-tenth of the cost." I got the crystallised nitrate of silver used for photographic purposes, and dissolved it in distilled water, adding ammonia as directed, and stirring with a glass rod until the precipitate formed, when the ammonia was first added was dissolved. The solution thus obtained

was clear after settling, but there was a dark sediment in the bottom of the bottle. I could not get crystallised Rochelle salt, but I procured the powder, and made a saturated solution of it, and put it in a dish to evaporate, when, in a few days, I got beautiful crystals. These I dissolved in distilled water for the reducing fluid. I used for the plane 30 drops of the silvering solution, and 15 drops of the Rochelle salts, and cleaned it with rouge and wash-leather. I obtained a film, but so thin in the centre that the gentlest rubbing removed it from the glass, while all round the edges it adhered firmly and took a brilliant polish. As the film in the centre of the glass only appeared nearly transparent, and cloudy when held between the eye and the light, it occurred to me that the cause might be the glass not being sufficiently clean. I procured nitric acid, with which I rubbed it, and afterwards washed it to remove the acid, but with no better result. I tried both the silver and salt solutions double the strength-viz., 20 grains to the ounce of water, but still the same result. I have sometimes kept on the solution for some hours, adding more when nearly dry, by this means getting a thicker film in the centre; but then there was always whitish, rough patches, chiefly about the edges, which no amount of polishing would remove. I should feel very grateful if any of your numerous readers would help me out of my difficulty, and point out where Lam in error, and advise me what to do.

Would Mr. Purkiss, "F.R.A.S.", or any reader, kindly inform me what should be the size of the diagonal plane for a speculum of 6in. diameter, and 66in. focal length; or rather, I should like to know by what means it is known, so that I might be able to find for myself the size of plane for any size of specula I very much admire the telescope stand of Mr. Blacklock, late of Manchester, now of Aberdeen. I am making mine of the same form; would he kindly describe his method of mounting the speculum. I should feel obliged it he would ascertain if glass suitable for specula is to be got in Aberdeen, as the carriage from the south comes so high.

I may mention that in grinding and polishing my speculum, although I have followed the directions of Mr. Purkiss, I have not used a machine, but worked it entirely by the hand. I have, however, devised a means which I believe to be original, as I have seen no notice of it, by which a regularity of stroke with careful manipulation is insured. If my speculum turns out well when tried, I shall be happy, with your permission, to describe it for the benefit of such of your -readers who, like myself, are unable to spare niuch money for such a purpose. JAMES GRAY, Beauly, N.B.

EXTRACTS FROM CORRESPONDENCE.
THE BICYCLE.-" Veloce says:-"Pending Mr.

THE VELOCIFERE."-Having read a letter from Mr. W. H. Reveley in your last issue, I am much surprised that the velocifere" therein alluded to (a description of which was given in a former number of the ENGLISH MECHANIC) has not yet appeared before the public, as if it went only half as fast as described. namely, 15 miles an hour, with as little exertion as walking two or three, velocipede inventors need no longer rack their brains, as it ought to meet the requirements of the most exacting, and be invaluable to persons using such means of locomotion.-TRICYCLE.

REPLIES TO QUERIES.

[1669.]-SMALL FURNACE.-"C. R." can convert
Napper No. 2 fire to answer his purpose if he has a
fan, or by using Dorset liquid fuel. If C. R." has
not seen any of this fuel at work, I will send him a
sketch of it.-GEO. STUART.

[2276.]-GRANITE POLISHING.-The granite
must be first dressed as level as you possibly can, as
that saves a deal of polishing, it being naturally a
hard substance; then well rubbed with fine sand and
water by an iron plane, until the tool marks are com-
pletely rubbed out, when it must be all clean washed
off.
Next apply No. 0 emery with water, the same as
the sand, with this difference, the emery must be
rubbed until it is reduced to a "sludge." It is beater
to have a frame about 6in. round the stone, and the
joints closed with stucco, as that prevents it from
Wash
losing the quantity is lb. to the square foot.
clean down again, and finish with putty powder (oxide
of tin), applied on a felt attached to the bottom of the
plane, taking care the felt do not glaze, else it won't
better than No. 0.-W. R. M.
bite. If the granite be very soft, flour emery will be

[2408.3-METRONOME.-For reply, see letter, page

161.

[2461.]-INHALATION OF IRON DUST. - Might not" Turner" contrive a kind of bellows with double tuyere to blow all dust away from his lathe, similar to the bellows used by the pointers in many needle mills?-JOHN D.

2502.-CIRCULAR DISC.-This can only be done ap-
proximately, and in doing so, suppose a line representing
the radius of the orifice, the ends of which are the
centres of the two circles representing the orifice and
disc. Raise a perpendicular at the distance of of
the radius from the centre of the orifice, which will
cut the circumference of the orifice in a point where the
two radii meet. Let p be that perpendicular, which is
also the half chord of two arcs, standing on the opposite
sides of the same base. It also represents the sine of

half the central angles. From which we can find the
areas of the two segments, whose sum is equal to the
half area of the orifice.
From the properties of the circle

p2 = r2

8

9

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2 8

3

= 9

8 2

-r-r√2 = 3657
3 3

r being equal to 6in. or half a foot.
Also,

Newton's decision at Worship-street Police-court, as
to a case of a bicycle circling, I think it only fair to
say that to circle about is a very dangerous practice
to pedestrians. If a rider wishes to practise feats, he
should do it in a lane, or some other place where there
is no traffic. But it is not to that part of the In-
spector's evidence I wish to call attention; he says,
he confined himself strictly to roadway, but circled
about and rode round at a great pace (eight or nine
miles an hour).' Now, Sir, I wonder whether it is the
eight or nine miles an hour that is dangerous, or
whether it is the circling about. I hope, Sir, that the
magistrate's decision will not be unfavourable to the
bicycle cause, for I think that as a means of locomo-
tion, and a way to vigorous health and muscular power
If Mr.
combined, no other machine can surpass it.
Newton's verdict will be a conviction, then I and
others in the country will be open to conviction too,
for it is only a nice comfortable pace this fine weather R being equal to the radius of the disc again for half
to ride nine miles an hour. Sir, I see that in France the central angles.
a new paper is begun, expressly devoted to the veloci-
pede; why not in England? or devote a column every
week in your worthy journal."

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MR. BEARDSLEY'S LETTERS.-Mr. J. Dyer And says:-"I have seen Mr. Beardsley's letters, but see but little in them calling for serious consideration. He appears to me to be objecting for the sake of it, and seizing upon any circumstance wherewith to attack the truths of astronomy. Some of his statements are retailed from "Parallax." I will, however, attend to the gentleman, and if he advances anything worthy a reply, and no more able person should Answer him, I will make some observations when he has finished his letters; at present it is difficult to get at what he believes, or what he is aiming at. He is an ardent advocate of the views of "Parallax," and has

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heat.
I use an old jug and the oven of the kitchen
This gives a powerful light, but would,
fire after tea.
I fear, be too expensive for general use.-C. WARD.
[2521.]-CURIOUS AFFECTION OF THE TEETH.
-The deposit is called tartar, and consists of salts of
To prevent
lime and organic matter from the saliva.
its formation the teeth should be cleaned twice a day
at least with soft tooth powder sprecipitated chalk is
When tartar has accumu-
the best) and a little soap.
lated, it must be removed by the scaling instruments
of the dentist.-J. M. K. E.

[2528.]-MUSICAL BOX.-The construction is very
simple. A side-toothed wheel, on the axle of which is
fastened one end of the winding-up spring (which is
enclosed in a small circular box on the left), is put in
gear with one end of the roller, on which are fastened
the fingers or pins which lift the teeth of the comb,
The motion is regu-
from whence the sound comes.
lated by means of a small fly-wheel playing before
the spring-box (which, by-the-bye, goes out of sight

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during business). This fly, standing upright and hav ing a thread round the stem, is acted on by fier wheels, which are in gear with the end of the roller. "Omar" will find on the top of the spring-box what is called a "Geneva stop," illustrated on page 53 (No. 12 being marked in the corner) of the present volume. The right end of the roller comes slightly over the edge cf the same, and is caught in a slit in a small lever (worked by a pearl button outside), which moves the roller up and down its axle, thus altering the tune or position of the pins. The left button stops the revolution of the roller by the end of a lever turned like the letter L popping into a hole in the roller-wheel at the end of each tune. And now I must beg our Edi. tor's pardon for taking up so much space in trying to explain the "guts" of a musical box.-HARRY BERTRAM.

[2534]-ERRATUM.-The diagram given with the 3rd solution of this query belongs to the reply of Gregory," page 139, Q. 1935.-X. X.

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[2548.]-GILDING BATTERY." One in a Fog" has charged his battery would be better than 1 in 2. to commence with. 1 part acid in 12 of water

The sulphate of copper should be suspended in the
upper part of the solution instead of the bottom; but
the main cause of failure is that he is using cyanide of
potassium instead of aurocyanide. The cyanide must
be charged with gold before he will get a deposit.
he persevered, this would be effected by the action of
the battery; but his globe surface ought to be large-
SIGMA.

If

[2550.]-ETHERIAL GOLD SOLUTION.-This is applied simply by brushing over the steel surface, or by writing with a quill pen. The steel requires no preparation beyond its surface being clean and bright. The deposit is a mere film, which will bear little friction, aud cannot be thickened by this solution.-SIGMA. [2558.)-SUN-DIAL.-The following is good method of setting a dial:-Set the dial by the sun at mid-day as correctly as possible. At nine o'clock on a At three bright morning set your watch by the dial.

in the afternoon observe the difference between the dial and the watch, and correct the dial for half the difference. Proceed in this manner day by day till they agree perfectly. Observe, however, that the equation of time must be taken into account, and set your watch fast or slow, as may be necessary.— 2 J. M. K. E.

THE PATENT LAWS.-" Beaten," states: "For wart of means to patent, I have for about two years nursed a loco-manumotive power. My ambition is to Half area of orifice = Half patent this power in England, France, and the States, and here comes the rub the wealth of England has had the making of England's laws, of course they are made for the benefit of the wealthy class; the Patent Laws among the rest, the A B C of which is, that if a man can muster £40 within 6 months, he may have a patent, and this is exceedingly nteresting to an inventor, who deems himself a lucky fellow if he can [2505.]-WEIGHT OF WATER.-A cubic foot of muster the price of 40lb. of potatoes when wanted, rain water at 600 Fah. weighs 997 137oz. avoirdupois. and with glowing admiration he contemplates the The average weight of sea water at the same tempepaternal, patriotic laws under which he lives, when rature is 1025ozs.; that of the Dead Sea 1240oz. The he compares them to those of despotic France, or He-temperature of greatest density of rain water is 38° 8, publican and Democratic America, in either of which and between that and 620 it varies but one part in he may patent his invention for comparatively an It is generally assumed (for conve'old song,' be well protected in his rights, when ob-nience of calcuiation) that a cubic foot of rain water tained, and their defence and redress easy, if infringed. at 388 Fah. weighs 10000z,-BROTHER TED With respect to the English patent, my difficulty is, how to satisfy a capitalist without imparting the secret? Will any brother reader sugge et a method, I confess that in this I am fairly beaten.

one thousand.

[2506.]-CAMPHORATED COLZA OIL is prepared by dissolving 14oz. of camphor, broken up into small pieces, in one pint of colza oil, by aid of a gentle

of

[2558.)-SUN-DIAL.The simplest method obtaining a true meridian line for a sun-dial is from the Ordnance maps, on which the lines of longitude are accurately marked, and the Grecuwich mean time, which is telegraphed daily to most towns and railway stations. If you set your watch by the Greenwich time, and then take your longitude from the map, adding or deducting 4 minutes in time for every degree, and 4 seconds in time for every second of longitude, as your place is east or west of Greenwick, if the sun and clock are together (which is only the case on a few days in the year), you will readily obtain your meridian. Thus, the place I reside at is 0' 48" This is equal to 3 minutes and 8 west of Greenwich. seconds in time; therefore, on a day when the sun and clock agree, when my watch shows 12h. 3m. 8sec., the sun will be on the meridian. Of course the equation table is necessary at all other times.-ANON.

will

[2559]-ANTIQUE.-If "Vivus Sperandum" send W. Nelson Last, Bury St. Edmunds, au impression of his cornelian ring per post, he will (through the ENGLISH MECHANIC) give him the information be requires. The art of polishing the engraving is not lost; but it is only the best engravers that attempt it. [2565.]-HERBAL OF THE BIBLE.-" Ixion may obtain Plants and Trees of Scripture" of the Religious Tract Society, Paternoster-row.-W. G. RAYBOULD.

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[2565.] HERBAL OF THE BIBLE.-"Bible Natural History, containing a Description of Quadrupeds, Birds, Trees, Plants, &c., mentioned in the Holy Scriptures." By the Rev. F. O. Morris. Published by Groombridge & Sons.-WORKING WOMAN. [2566.]-TOOTH POWDER.-Armerian bole is the best and cheapest tooth-powder to be had for keeping the teeth fresh and white. Twopennyworth will last It is of a reddish colour, and sold at for six months. any respectable doctor's shop. Use the least quantity

on tooth-brush every morning with fresh cold water, and in a few days it will make the teeth beautifulFFOREST MILLAR, Glasgow.

[2567.)-CHIMING CLOCK-If "Toodles" will take out the old cords of his clock, and put in stronger ones, or catgut, he will find this much better than putting a haybag in the bottom of his clock-case. D. H. S.

I can.

2573-EOLIAN HARP.-In answer to "R. B.," I have much pleasure in giving him all the information It is constructed of very thin yellow pine. The length equals the breadth of the window, the depth about 4in., and the breadth about 6in. There is a bridge at each end of the box like the bridge of a vioJin, with screw pins in it, for relaxing or tightening the strings. The strings are of the finest catgut, seven, ten, or more, all tuned in unison to the same note. There is a circle 14in. in diameter drawn on the top of the box, exactly in the middle, underneath the strings, which is pierced with small holes, to act as a sound bole. Place the instrument in a window and

draw down the sash, which will force the wind over the strings and cause it to sound.-VALVE. P.S.Many thanks for the insertion of my query, 2562, No. 265, but there are one or two typographical errors in it which will make it rather hard to be understood. Perhaps you will be so kind as to insert the following correction:-"Reed hibs" should be "reed holes," and "accident" should be "accidentals "-that is, sharps or flats that occur in the course of a piece of music.

[2579 J-MALLET.-If "Anon" wants to make a pattern for his mallet, the following will give him all the information he requires:-Let him make a block of wood the size of the shell (outside size), and nail a piece of wood on each end the inside size of shell, about 1 in. thick, and nail two pieces, one on top and the other on under side, the size of hole required for shank, and about lin. thick, the top one being larger than the other, to form a taper. Those are called prints; they leave an impression in the sand to bear the cores. He will have to make a core-box the size of inside size of shell, composed of two sides and two ends, it being a frame the size of the core (inside size), with a hole cut through each side the size of small prints, one larger than the other, with a piece of tapered wood fit through them, to project about 14in. through each side; must be left loose to pull out. Make the core-box the same length as the block and the two large priuts. A diagram will greatly assist

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1,37

34: 13,28

4,44

and r = h: H: 0,37 0,63, gives h = The proof gives a slight difference proceeding from the neglected decimals, &c.-BERNARDIN. [2593]-DEFECTIVE BATTERY.-If the silver plate has been in contact with the zinc, it has probably absorbed some mercury, which would spoil it. It would require to be heated to reduess to drive off mercury, cleaning, and replatinising, for which see paper on Batteries sent with this reply. The contact screw is most likely too loose, and the vibrations shake it away from the spring. If so, a piece of thread inserted in the screw-hole will tighten it up.-SIGMA.

[2594.]-BORING WOODEN HANDLES.-I suppose, from "A. B's" question, that he has many handles to bore, and in that case a half-round bit, or a short piece broken off a carpenter's nose-bit, and soldered into a small brass chuck to fit into the centre hole of the poppet head, would be a good way of The handles should be held either starting the holes. in a clam-chuck, or be supported by a collar plate. 1 always use a common gimlet, taking care, however, not to work it as you work a cork-screw-viz., holding the bottle still and turning the screw round, but ting the tool handle shift at each half turn in the left holding the gimlet firmly in the right hand, and let

hand, as by this means you can feel whether it is running straight down the middle or not, and with a common gimlet you can apply force sideways to scoop the hole when you find any tendency to running out. The usual way is to burn the tools into their handles, and I see no objection to the practice, provided, first, the hole has been bored deeper than the point of the tang of the tool will ge; and, secondly, that all the charred portion of the wood is filed or scraped out of the hole before driving the tool finally in. If the tool is thin, with a broad tang, like a Lancashire file, it will burn its own hole too wide in the narrow direction, so a thinner tool should be used to do the burning. A much better plan is to have two or three floats, or small taper files, cut on one side, and one edge only, with a few coarse teeth, and one or all made to cut backwards, for getting out the holes to suit different dimensions of taugs. Almost any old tool that is small enough will do to make them of, and the notches may be, and are better for being, as uneven as you please; and the tool need not be hardened, or if hardened, should be lowered to sawtemper, so that you can easily sharpen it with a file. The best wood for handles is ash, as it does not blister the hands. It must be well seasoned, or the ferrules will drop off, and a dressing of linseed oil and yellow ochre, with alkanet-root to give a red tinge, should be smeared on, and allowed to dry on for a day or two, before giving the finishing rub-off.-J. K. P. [2598.]-LEYDEN JAR-A charge might be given by means of a glass rod, but it would be a tedious business, and not much satisfaction to be got out of it when accomplished, by means of frequent rubbing and application.-SIGMA.

[2604.)-PROBLEM.-To draw a circle passing through two given points and tangent to a given circle. Let O be the given circle, and A B the points. Through A B draw a circle cutting the first, hence C. D, and E. From E draw a taugent, to circle O. and the circle passing by A, B, and F will answer the problem:

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cumference in G, the point of contact for the required circle. Join E G and G F, each of which bisected and produced will cut in H. HG will then be the radius of the circle required.-HARRY G. NEWTON. [2606]-DAWN, &c.-The periods of day and night are caused by the earth's rotation on its axis. The change from day to night and from night to day takes place in the following manner:-The sun enlightens only that half of the earth's surface which is turned towards him; and as the earth successively presents different parts of its furface to and from the sun, these parts must have alternately light and darkness. the Equator the day and night are of equal length during the year-i. e., 13 hours each. At the Poles the day and night are of equal length during the whole of the year; but there is only one day and one night, each being six months in duration. The dreary wirter

At

of the Polar regions is relieved by reflected light or Other twilight by auroras, and by the full moon. reasons for these changes are, the earth's annual motion round the sun, and the earth's axis being inclined to the plane of its orbit. Hence, Hudson's Bay Territory, Greenland, Lapland, Siberia, will have the longest starlight.-R. WILSON.

[2604.]-PROBLEM.-(By the kindness of a Professor of King's College, London). A is the centre of the given circle; B and C the two given points; bisect BC and draw H G perpendicular to BC; then the line H G (produced if necessary). centre of the required circle lies somewhere on the From an arbitrary centre H, draw a circle through B and C, cutting the

H

given circle in D and E produce CB to F, and draw ED produced to F: draw FK tangent to given circle, and from A draw A G perpendicular to FK; then G, the point of intersection of H G and A G, is the centre of the required circle. P.S.-Supplementary. given circle, and the diameter drawn at the point of -If the tangent F K is drawn to the lower side of the contact, and produced till it cuts G H produced, then the required circle falls outside and embraces the given one.-J. K. P.

[2609.]-OLD COIN.-Roman. Read VESPASIANUS and JUDEA CAPTA.-COLLECTOR.

[2609.]-OLD COIN.-The piece found by "X. I. D." is a coin of Vespasian, Emperor of Rome from A.D. 69 to A.D. 79. On the obverse there is the bust of the emperor, with his name and titles. Reverse, a female figure, seated, weeping, under a palm tree; a Roman CAPTA (Judæa taken). The letters S. C. appear upon soldier, standing, behind. Inscription: IVDAEA nearly all the Roman brass coins. They stand for Senatus Consulto (by decree of the Senate), because all the brass coinage was under the control of the Senate. This coin was struck in commemoration of the subjugation of Judæa by Vespasian and Titus, and of the total destruction of Jerusalem, A.D. 70. It is rare, and the market value would be between 10s. and 158. It is a very famous and interesting piece. -HENRY W. HENFREY, M.N.S., &c., &c.

[2621.]-CUTTER BAR.-In reply to "Foreigner," I made one of these to the design of "D. H. G.," and had to make the same complaint of it that he has. "D. H. G." very kindly told me that the cutter is shown in the drawing projecting far more than it would be in use, for that it was meant for a lathe whose centre line is 9-16th inch above top of slide-rest. I think the crank might be a little longer without doing harm.-J. K. P.

[2624.1-PROPORTIONS OF SPACE.-The volume of a sphere volume of the cube constructed on its diameter x 0.5236. The weight of lead shot that can be packed in a given case must necessarily vary according to the diameter of that shot.-B.

[2624.]-PROPORTIONS OF SPACE.-TO "MECHANICUS."-One single sphere is 5236 of the surrounding cube; but if you have a number of spheres,' and put three of them together in a triangle, or four in a rhombus (not a square), and go on packing others round them, each ball will stand in the middle of twelve others equidistant from it and from each other. It may be proved that each ball occupies on an average 707 of the cube of its own diameter, while the ball itself is only the 5236 of that cube, or what is the same thing, the ball would occupy only 5236 of the whole space if we started packing with a square in the middle instead of a rhombus.-See Denison's "Astronomy without Mathematics," 4th edition, p. 266.-J. K. P.

[2629.]-THE QUEKETT CLUB.-Allow me to inform Ed. H. Jones that the "Journal of the Quekett Microscopical Club" is published quarterly, price one shilling, by Mr. Robert Hardwicke, 192, Piccadilly, London, W., from whom your correspondent can obtain information as to the means of obtaining the journal in Bristol.-W. H. G.

[2631.-SPHERICAL FORM OF THE EARTH. -The reply to "Ajax's" question depends upon the form of the bottom of his cistern. If it was a true flat, such as an instrument would make, or a level would show, it would appareatly be hollow in the middle, and water would remain there long after it had run off the ends. In that case the water would be deepest in the middle; but if the bottom was a level like a billiard table, on all parts of which water would alike rest, it would be a curve, and the depth of water alike in all parts. The extreme idiocy of the arguments, as their utterers call them, set forth on this subject is really too much for people who know anything of the matter. No intelligent human being who really has examined the subject could entertain a doubt about the spherical form of the earth. It can be measured even in a long building. If the two ends are truly vertical, a measure taken along the top is longer than one along the ground line.-SIGMA.

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[2638.]-MAKING BUTTER-I have heard there is an easier way of making butter than churning; can any reader tell me how it is done?-CAMBRIDGESHIRE. [2639.]-OPINIONS WANTED. Perhaps some of your numerous readers will be so kind as to give me their opinions about the cause of the following:-A short distance from here are four horizontal engines, which are used for drawing coal; one steam valve is common to them all four, likewise one lever for reversing them. In lowering down the pit they have full steam, about one-third of the distance, then it is shut off, and the lever brought into the centre notch, which ought to close the ports, but the pair of engines to the right band still continue to exhaust, and those to the left do not. If some of our intelligent men will give their opinions as to the cause and its remedy, it will perhaps benefit others as well as myself, for I know that when the engines were made, it was intended that they should not exhaust at all in lowering after one-third of the distance, as it is a shaft where they have only one rope going.-JOHN W. BEdford.

[2640.]-GIRDER PATTERNS, &c.-In making patterns for girders, gutters, &c., that are stronger at the bottom than the sides, the pattern has to be made round, so that when the casting cools, the contraction draws it straight. Will some practical man be so good as to give a rule for calculating how round to make any girder, gutter, backstay, or anything else of a similar character ?-JOHN W. BEDFORD. [2641.] MEDICAL COIL. (Page 513.) "Sigma" kindly explain what he means by saying, -Will "solder 2 to N battery pole," and further on he says, "lead 2 and 3, and any other ends, to screws at the other end of board." Is this correct, and if so, please say how it is to be done, that is 2 at both ends of the board and different screws, and also the best kind of battery to use. UNLEARNED MAN.

[2642.] FISHING RODS."The Harmonious Blacksmith" says he has had considerabla experience in making fishing rods; I shall be very pleased if he (or any other practical gentleman) will give me a few hints how to make a useful rod, about 14 or 15ft. long. the best kind of wood for each piece, how to put the ferrules on, and any other information that he thinks would be useful.-A YOUNG TYKE.

[2643.]-IRON PRISM.-A square prism of malleable iron, whose length is equal to four times that of one of its sides, is to be rolled (or flattened) into a square plate of uniform thickness, such that its whole superfices shall just be equal to its solidity. Required, the sise and thickness of the plate, the solidity of the said prism being 2916 cubic inches, allowing no waste in the metal. A MIDDLETONIAN.

[2644.]-ADULTERATION OF TURPENTINE.Would some one inform me how I can best, or at all events easily, ascertain whether turpentine is adulterated?-BASIS.

[2645.]-IMPERFECT TWO MANUAL ORGANS. -I should be obliged if any of your readers would enlighten me upon the following:-I have a two manual organ, and am sorely troubled with the reed stops being so often out of tune in the swell organ. The reed stops are cornopean, clarion, and oboe, but the clarion is the one that gives me most trouble. The oboe keeps pretty well in tune, but is very slow in speaking. The reason of the reeds not keeping in tune is, I am informed, that the pipes and tongues are not made in proportion to each other, and that to remedy this would be almost as expensive as having new pipes. I wish to know if I am correctly informed as to the cost, also what would be the cost of a set of flute pipes to replace the clarion, and the cost of applying them ?-ANTI-DISCORD.

[2652.]-SULPHATE OF ZINC.-Will any correspondent inform me how the sulphate of zinc of commerce is manufactured ?-TELOS.

[2653.]-CHEMICAL SOLUTION.-I have a solu. tion composed of sulphuric acid, sea salt and water, in which a quantity of zinc has been dissolved. Will any correspondent tell me what the precipitate, which has been formed, is ?-TELOS.

R

[2672.]-DRAFT WANTED.-We are short of draft at our works to keep our steam up, and there is a large chimney, distant from boiler 80 yards. Will some one of your numerous readers inform me of the best means of carrying the flue underneath the ground that distance, and if it would be an effectual means of attaining the desired end?-H. GREGORIEFF. [2673.]-CASTING SILVER BALLS-Could any [2654.]-METRICAL ACT.-Of what date is it? of my brother readers inform me of a better method Does it not give the exact reduction of English weights for casting silver into small ornamental balls; casting to employ only the letters A. K. W. for and measures into metrical? I propose to querists them in sand as I do) they come out so rough, which I "A kind want to avoid. I have tried plaster of Paris, but only always (which is the case) suppose this phrase unanswer will oblige," or rather to add nothing and part ones come; is it for want of ventilation, or what, derstood?-JOHN D. and how is it to be done?-CASTOR. [2674.]-CLEANING WHITE CORAL.-Can any [2655.-ARCHERY.-I am about to purchase a self-reader inform me how to clean white coral, and restore his advice as to how to choose a suitable one, as to dust, which has made it almost black?-INQUIRER. Would some brother archer kindly give me it to its original beauty, after being exposed to the strength, &c.? I have shot for two seasons with a [2675.]-POLISHING WATCH PIVOTS.-In polishhickory backed lancewood bow, of 461b. tension, which ing a pivot with a square shoulder, what is it that prohas an unpleasantly sharp pull, but is not too strong duces those cuts or ridges in the shoulder? I have heard how much? Is there a good modern book on archery? the exact cause or motion which produces them; perfor me. Ought a self-yew bow to be stronger, if so, it attributed to several causes, but never could learn -YOUNG TOXOPHILITE. haps some practical watch pivoter will give the best plan for preventing ridgy shoulders, and so help a young beginner?-C. R.

yew bow.

[2676.]-MODEL STEAM ENGINE.-Some time since I saw advertised a small model vertical engine, ing to the drawing there seemed to be a cylinder and with a spirit lamp underneath to raise steam; accordpiston, that turned a small fly wheel on the top; the price, I believe, was 4s. 6d. ; can any brother subscriber give a drawing of the model in question, showing how motion is produced by steam in so small an engine?C. R.

[2656]-BOOKS.-Can "Sigma," or any other of our numerous readers, recommend a good book on practical electric telegraphy? I have made inquiries at several booksellers without success ?-MUCH IN WANT. [2657.]-FORBES KNITTING MACHINE.-Might I ask, through the medium of your journal, Forbes, Bros., and Co., of Glasgow, to give a more detailed account of their knitting machine, illustrated in No. 251 of your last Vol., feeling sure that many of your readers would like to see the same?-VIGIE. [2658.] OBJECT GLASS. Would any of my brother readers kindly give me a little information Would any reader acquaint me how many cubic feet [2677.]-HYDROGEN GAS FOR BALLOON. telescope, which glass is lin., and if I could see dis-being of eleven stone weight, in our atmosphere; also, whether I could get a stronger object glass for my of carburetted hydrogen gas is required to float a human tinctly without altering the other glasses in the inside? what size balloon should it be to carry this volume of gas?-HENRY NUTT.

-IGNORAMUS 2.

[2659.] ASTRONOMICAL BOOKS.-Would some
best and most authentic elements of the planets' orbits,
reader kindly inform me where I could obtain the
including the asteroids, with price?-D. JENKINS.
[2660.]-LEO'S VELOCIPEDE.-Will" Leo," whose
velocipede appeared in the MECHANIC, No. 218, Vol.
IX, gives a description of the indiarubber springs
which bring the pulleys back to their first position;
how are they fixed, what size should they be, and
will he give a description of his ratchet work? Can
any other readers, who have had experience in ratchet
velocipedes, give me information as regards the
ratchet, pawl, pulley, spring, &c. ?- AN OLD SUB-
SCRIBER IN A FIX.

[2661.]-GALVANISING CAST IRON.-What is
the bath composed of for cleansing cast iron for gal-
vanis ng, and of what is the galvanising bath itself
composed? The kind I refer to, would be a bath
similar to that used for galvanising iron buckets?-
B. WEBB.

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how

[2679.]-UNANSWERED QUERY.-CURLING HORSEHAIR-Can any reader inform me horsehair is cured and curled; also, how feathers are steamed and purified ?-ONE IN A FIX.

2680.-LANDSCAPE PAINTING.-Can some artistic correspondent favour me with a recipe for making a good medium or "megilp" for water colour painting?-O-CE-O-LA.

[2681.]-COPPING MULE.-Is there any reader whe knows of a work treating on the self-acting mule, the part more particularly termed copping the mule; or can any subscriber give a good practical rule for copping a mule? A drawing of the rail would be of good service in pointing out parts of the rail likely to effect the shape of the cop; for instance, if I had a rail this

[2662]-WATER METER-Will any brother reader
be kind enough to give me a full description of a high
pressure water meter, its construction, and the action
of the water in passing through it, how it is measured,
&c.? The one the water company furnishes me with,
registers four and five times more one quarter than
another, and I can affirm that the quantity used is as CIRCLE
regular as possible?-FIDUS ACHATES.

[2663.]-QUICKSILVER. -
-Will a brother reader
furnish me with a solvent for quicksilver? I acci-
dentally spilt some over some watch wheels, and want
to clean them; and if what will do for the above will
it do for plated jewellery ?-FIDUS ACHATES.

[2664.]-ARM CHAIR.-I have an arm chair, the
leather covering very much faded, but in good con-
dition; can any one tell me how to stain it a maroon
colour?-EXCELSIOR.

L. LEWIS.

A

B

shape, A, and I altered it to this shape, B, what would be the result in the shape of the cop?-OLDHAM. [2665.]-INDICATOR.-I should feel exceedingly [2682.]-TO THE REV. T. W. WEBB.-In the constructing the indicator used with induction coils?-mentions, that he was successful in separating thankful if any one would kindly give instructions for ENGLISH MECHANIC of April 15, Mr. T. W. Webb Cancri, so recently as the 31st of March last. Will you permit me to ask him to give, in an early impression of your paper, the observed position, angle, and distance between this close double? I should also feel much obliged to him, if he could give me the result of during the last six months?-OM RON. any observations he may have made on Herculis

[2646.]-GILDING PLATE GLASS.-How do glass sign writers gild the back of plate-glass, after the letters are written, and vice versa ?-BLACKBURN. [2666.]-COPPER DEPOSIT ON CAST IRON.[2647.]-COLOURED PRINTS FOR DECORA-I want to get a deposit of copper on cast iron; will TION. Where can I buy those coloured prints which, some reader kindly inform me what chemicals to use? when steeped in water, may be laid on to any smooth-DI VES. work, and the paper on which they are printed slid away, leaving the print firmly attached to the article operated upon ?-BLACKBURN.

[2648.]-CARDING ENGINE.-Would "B. W. R., or some other brother reader, please inform me, through the medium of our highly-esteemed journal, which, in his opinion, is the best carding engine at present in operation, and that has the most modern improvements? If accompanied with a drawing, perhaps the matter would be rendered still plainer. I believe the carding engine in general use in the Manchester and Bolton district, is that to which the American patent automatic movement is applied. Would he also say what, in his opinion, is the best appliance for grinding the main cylinder and doffer, and what is the difference effected between using the ordinary grinding strickle and the patent grinding pulley, which is worked from end to end of the engine by means of a spiral groove in the shaft?-EXCELSIOR.

[2649.]-PIANOFORTE. -Will the "Harmonious Blacksmith" inform me of the following questions, viz.-1st. How are the holes that the lever wire works through, which lift the damper, bushed? 2 How are the same holes bushed in the hammer butts? -M. L. MOFFATT.

Can any of your readers recommend a paint or coating
[2667.]-PAINT TO COVER TARRED WOOD.-
to cover tarred posts? It would have to adhere to the
tarred surface, and to resist the tar oozing through it
in summer. Colour must be light, as it is to make
tarred posts pretty visible on a dark night, and save
people from driving against them?-ASSOCIATE.

[2668.] - - SKETCHING FROM NATURE.
"Sunshine," or some other kind reader, inform me
-Will
and muriate of cobalt ?-TYPOGRAPII.
where to obtain (wholesale), and the price, acetate

kindly inform me how long iron pallisadings, painted,
[2683.-IRON PALLISADINGS.-Will any reader
varnished, and bronzed, stand the weather?-W. A. J.
[2684.]-ENGINE CHIMNEY. - Perhaps some of
your kind readers will give us the proper size of an
meter, as the one we have is far too small; also, if we
engine chimney for a boiler, 25ft. in length, 5ft. in dia-
should consume any more fuel with a larger one, and
is there any rule for calculating the size of such chim-
-A SUBSCRIBER.
neys? The furnace is 5ft. by 4ft. 6in., with a flush flue?

brother have just heard with pleasure that there is an
[2685.]-AMATEUR TURNERS' CLUB.-I and my
amateur turners' club come into existence; will some
subscriber give us all the information respecting it they
can?-M. H. HUME.

information that will lead me to a correct solution of
[2669.]-MAGNETISM.-I should be glad of any
the following questions in magnetism:-1. How would
you figure the magnetic curves of the earth, and show
their relation to the line of dip? 2. What is meant by
3. What is meant by secular variation?-F. P.
horizontal intensity, vertical intensity, and total force?
the gold plate to a set of teeth; can any of my brother Can any of your numerous readers inform me how to
[2670]-ARTIFICIAL TEETH.-I want to repair
readers inform me how I can get the teeth off the balance Arnold's chimney ventilator? A sketch will
[2686.]—ARNOLD'S CHIMNEY VENTILATOR-
MONTIQUE.
pins, and the method of securing them again?-much oblige ?-IRONFOUNDER,

[2671.]- CANOE BUILDING.-Many thanks to [2650.]-TO "F.R.G.S."- MAP PROJECTIONS. "Boat Builder" for the kind manner in which he has -I shall feel much obliged if you will tell me the noticed my query on the above subject. Will he oblige method of projecting a map on the gnomonic projec-planks are worked first, and the timbers put in afterby explaining the following. He says, "the strakes or tion, having any given place, say London, in the centre, or if the description would be too lengthy, ! wards." How are the planks kept to the proper curve should be glad to know the name of any book where I and shape of canoe while building? How are the could find an account of the method?-J. M. K. E. edges of the strakes fastened to each other? I purpose making it of yellow [2651.] LECLANCHE BATTERY. deal, 3-16ths. of an Will any inch thick. brother subscriber tell me how to re-charge the porous What would be the price of 40ft., a foot wide? cell of a Leclanché battery. Those in my possession If he would give me a few plain practical directions as to how to go about it, I should feel are patent cells, made at Silvertown by the Gutta greatly obliged, as I am totally ignorant of the art?-Percha and Telegraph Works, Co., Limited.-TELOS. C. D. R.

best thing to dust brass moulds with, and why should [2687.) DUSTING BRASS MOULDS.-What is the not charcoal do ?-IRONFOUNDER,

[2688.)-RENDERING WOOD INCOMBUSTIBLEIs there anything that will prevent wood from taking fire, and if so what, liquid or otherwise?-IRONFOUNDER.

[2689.]-TURBINE.-Can some reader give a sketch and explanation of the best form of turbine to work horizontal shaft, which takes about 4 h.p. to drive, size of inlet and outlet, or makers of same ?-SIMPLETON. [2699.]-ALGEBRA.-Many thanks to kind and able Mr. Henfrey, for his response to my query about the planet Neptune. Whatever you do, don't weed your

MAY 6, 1870.7

Notes and Queries" too much; some, like mine, may
be unimportant, but none will be downright silly, and
Remember the educa-
all will be serious and earnest.
tionalism of the thing, and, like as the Times is
the recognised vehicle for advertisements, so let the
ENGLISH MECHANIC be the oracle for scientific
inquirers, young and old, little and big. My present
incubation is in the algebra nest. I see several of your
correspondents frown on algebra; so do I. Of course
we admit the convenience of algebraic notation, for
formulas, &c.; but still, take the science" itself, and

is there not a great deal of humbug" in it? Is not
this why Mr. Biggs and "Pneuma" cannot agree?
What good can there be in bringing you up always to
some such result as plus or minus the square root of
minus two, 2? It may sound grand, but how
can the like be ever serviceable? The farther you push
the science itself (and I have gone deep into it), the
more do you find it only a wilderness of paradoxes. Is
not the whole equation system a mistake, such as
Colenso's" quadr. equ. ex. 62, 19; or Todhunter, p.
196, where the horse costs £60 or £40," and we are to
Even take it, that all
be quite content with the or.
this is the present bad handling of algebra; well, is
there any, book that shows you how to escape the
I should be glad to hear
endless ors and paradoxes?
that the addled egg is not Algebra's, but mine own.
-GIMEL.
[2691.]-TO "ADEPT"-Will "Adept" kindly tell
me the use of the following:-No. 1. On the wind trunks
of an organ of two manuals, 33 stops, by Messrs. Hill
and Son. No. 2. On an instrument of smaller size, by

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When the Bryceson, Bros., under sound-board. bellows are blown in a jerking manner, or when the instrument is played, these move backwards and forwards very quickly.-W. J. RAYBOULD.

[2692.]-BOTANY.-Wanted a plain description of the hedge mustard and cuckoo flower?-NON ALUMNI, [2693.]-KEEPING COPPER PLATES FLAT. Will you, or any of your readers, inform me how to keep thin copper plates perfectly flat, in continually passing through callender rolls; they pass through about 15 together, and the average size is 24in. square.

-C. H.

[2691]-GREATER PTHAH.-Can any of your readers tell me what is meant by the " Greater Pthah? -MINNEHAHA.

[2695.1-GEOGRAPHICAL.-Will some one be so good as to tell me what is the meaning of key in the words, netherset-key, key-house, key-spink, in the neighbourhood of Madeley, Staffordshire?-MINNE

НАНА.

[2696.]-CLEANING FLAGS.-Can any of your readers suggest a way for removing tar off flags, placed there by street advertisers ?-MINNEHAHA. [2697.]-CANARY.-What is the best treatment for a canary suffering from "wheeziness "?-MINNEHAHA. (2698.)-MILL AND FORGE WORK-ROLLING. Would some of my brother readers inform me of a book treating on mill and forge work; also, if some kind friend, who understands rolling, would tell me what speed per minute the following rolls should runviz.: guide rolls, merchant ditto, and forge ditto?A SUBSCRIBER FROM THE FIRST.

[2009]-CROQUET RULES.-NAPKIN RINGS.Where can I obtain the latest rules for croquet; also, how can I mark boxwood rings so as easily to distinguish one from another?-W. F.

[3700.]-DEVELOPERS.-What are the best developers to use for photographing designs and paintings, also fer portraiture?-W. CRAWLEY.

straight. I have hung them in hot rooms, but they
buckle, and are dried very irregular; and I have also
tried them in a baker's oven, betwixt plates of galva-
nized iron, but that would not do, as it only dried the
edges. Or if you could inform me if there are any
books published on the manufacture of pasteboard? I
know it can be done, for I have seen pasteboard per-
fectly straight and hard, but I cannot discover in what
manner it is done. Any information on the above sub-
ject. will be thankfully received?-THOMAS GRIST.
[3704.]-TOBUSY BEE."-In your reply to my
inquiry for waterproofing paper, it states, lozi of gum
nitric. I have inquired at several houses for it, and
the answer is, that the article is not known, and they
think it must be a misprint. Can you inform me as to
the above?-A. SPEIGHT.

[3705.]-COLOURS FOR GLASS PAINTING..-I
shall be very grateful to any of your readers who
will tell me of a rich transparent permanent pigment,
in crimson, brown, ie, port wine hue; also, a pure
bright yellow. Crimson lake, with the admixture of
burnt sienna and umber, yields the colour in all depth
and brilliancy, but the crimson lake is such a vanishing
colour, that I doubt if the browns would render it per-
manent in continual exposure to daylight. The colours
are to be used with oil and varnish for glass painting
Amongst all the varied and valuable information con-
tained in your journal, I have never noticed any on the
old art of window painting, I do not mean the modern
staining and mosaic patchwork. I have been a painter
if you could assist me in the former matter?-SABLE.
of dissolving views for years, but I should be thankful

USEFUL AND SCIENTIFIC NOTES.

MULBERRY LEAVES.-The Science and Art
Department of the South Kensington Museum has
placed at the disposal of the Silk Supply Association
a room for the purpose of rearing silkworms during
the ensuing months of May and June. The Associa-
tion being possessed of some very rare and valuable
eggs, or "grain," imported by the Hon. Secretary
from Siberia, Mantchouria, Szechuen, Shang-tung,
enabled to demonstrate, for the information of serici-
and other places where there exists no disease, will be
culturists in this country and in the colonies, the
is one of national interest, and, it is hoped, will stimu-
late our Colonies to turn their attention to silk cul-
simple practicability of silk production: The subject
tivation. Persons interested a silk culture at home
or in the Colonies, may have the opportunity of study-
ing the entire process by application to the Hon. Secre-
ta ry, 65, Morgate-street, E. C.

THE GUINEA AND THE POUND.-It is among the things generally known that the guinea obtained its name from the gold from which it was made having been brought from the Guinea coast by the African on the 14th of April of that year the Parliament recompany of traders. The first notice of this gold was ferred to the Council of State a paper presented to the in 1619, during the Commonwealth of England, when House concerning the coinage of gold brought in a ship lately come from Guiny for the better ad vancing of trade. But it was in the reign of Charles II. that orriginally coined the intention was to make it current the name was first given to this coin. It is among as a twenty-shilling piece; but from an error, things not generally know that when the guinea was rather from a series of errors, in calculating the exact proportions of the value of gold and silver, it never circulated for that value. Sir Isaac Newton, in his time, fixed the true value of the guinea, in relation to silver, at 208. 8d, and by his advice the Crown proclaimed that for the future it should be current at 21s. A curious question arises out of the fact alluded to; how many millions of money has the English public lost by the payment of a guinea when a twenty-shilling piece would have sufficed had the costly error never have been fallen into?

or

THE PRUSSIAN NEEDLE-GUN.-A contributor

to the Allgemeine Militar-Zeitung writes:-"As you know, two improved models of the needle-gun are on trial, which both aim at increasing the rapidity of firing, with as little waste as possible. From fifteen to twenty shots may be fired by them in a minute, so that the apprehensions of those may be quieted who are alarmed as soon as they hear another army can inclined to shrug onr shoulders when we hear the nonsense so current on this subject. All who have any experience know that two, or perhaps three, wellaimed shots are the most we can obtain from infantry in the field."

WHAT IS WANTED IN MODERN ART.-If the
Arts are to flourish among us, says John Ruskin in one
of his Oxford lectures, we must recover for the mass
of the nation three requisites which they at present
want: 1. Wholesomeness of food. We must no longer
allow them to eat and drink poison instead of food;
everything provided for their daily sustenance must
be good and pure, as well as plentiful. 2. Wholesome-
ness and decency in dress. It must be such as becomes
their rank-serviceable and good, and, at the same
time, becoming and in good taste. 3. We must im-
prove the lodgings. All ecclesiastical architecture is
developed for civil and domestic building and its high-load more quickly than ours. I and many others are
est achievement may be said to be a "glorified roof."
Now, in this our modern architects are strangely at
fault; they seem hardly to know what to do with the
roof. Roofs ought never to be built of iron, but always
of wood or stone. And we must remember that the
We
little roofs must be built before the large ones,
must see that the poor have houses suited to them,
built as strongly as possible, and daintily decorated.
A NEW PLANISPHERE.-Mr. John Love, Royal
Bank, Greenock, read a paper on the 25th inst. before
the Royal Scottish Society of Arts on "A new planis-
phere for showing the altitude and azimuth of the sun
or star."
The object of the contrivance, it appeared,
was to facilitate the study of nautical astronomy by
illustrating mechanically the observer's relations to
the path of a celestial body, and more especially to
the sun's path; and the means employed for this pur-
pose consisted of two stereographic projections of the
sphere, one of which was to lie symmetrically upon
the surface of the other, and to revolve upon over it on
Both projections were
their common centre.
on the plane of the meridian-the one on an opaque disc,
being a representation of the sphere with reference
to the lines of its motion and the divisions of its time;
and the other on a transparent disc, being a representa-
tion of the sphere with reference to its lines of altitude
and bearing. The arrangement showed the systems
of circles which respectively belonged to those two
aspects of the celestial sphere; and it was the inter-
sections of the two systems, read through the trans-
parency, which were to give the intended information.

drawn

A PROCESS FOR RE-SHARPENING FILES.-
M. Werdermann has exhibited a very interesting and
Well-worn files are first
economical process for this purpose, before the Societé
d'Encouragement of Paris.
carefully cleaned with 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 sur-
rounding 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 have been in the bath ten minutes, they
are taken out, washed, and dried, when the whole of the
hollows will be found to have been attacked in a very
sensible manner, but should the effect not be sufficient
they are replaced in the bath for the same period as
before. Sometimes two operations are necessary, but
The files, thus treated, are to all ap-
seldom more.
pearance like new ones, and are said to be good for 60
hours' work. M. Werdermann employes twelve me-
dium Bunsen elements for his batteries.

3701.1-KOLA NUT.-Will "Bernardin," kindly inform me where the kola nut is to be procured in London, and the price? I am reading up for a stiffin height. Its conductivity for heat is to copper in the examination, and shall be glad to try its restorative powers, after his plan, described in the MECHANIC of March 12.-GADDHA.

[3702.]-INLAYING FANCY WOOD.-Will some brother reader describe fully the modus operandi of inlaying fancy wood, such as is done on desks, &c.A SUSCRIBER.

[3703.]-PASTEBOARD.-I shall feel greatly obliged of some contributor could give me some information in pasteboard making, I have tried several methods of drying, but I can't find out how to dry them

SILVER.-The tenacity of silver has been studied
by Matthiessen, and can be stated for comparison as
follows:-Alloy of tin and copper, 1: gold, 36 to 43;
copper, 43; silver, 72; platinum, 72 iron, 13; steel,
30. It is so ductile that a grain of it can be drawn out
400ft., and it can be hammered into leaves so thin that
it would require 100,000 of them to make a pile an inch
ratio of 100 to 73 6; and for electricity, as 1000 to 954.
Cast silver expands, according to Calvert, between o
and 100 per cent., 0-001991; and its specific heat is
0-05701. Although silver conducts heat remarkably
well, its power of radiation 18 very small, so that a
silver vessel retains the heat of a liquid contained in
Pure silver, if highly
it longer than any other metal.
heated in oxygen, will absorb 6-15 to 747 volumes of
that gas; and under the same circumstances, will take
up 0.97 to 0-938 volumes of hydrogen, 0-486 to 0.545
earbonic acid, and 012 carbonic oxide-in property
differing considerably from palladium.

EXPANDING DRILLS.-The Mining Journat reports that Mr. E. P. Gleason has invented a drill applicable to rock-boring purposes. He proposes a drill whose cutting parts are attached to a bar by a joint, and formed with a round back taking against an incline. so that as the drill is dropped or projected the cutter acts laterally, and finally forms, by continual working, a chamber with an inclined top and bottom surface surrounding the drill-hole. This chamber can be enla rged by successive cuts above or below the first chamber. The cutting ports are easily sharpened or replaced when worn; and by using two cutters, acting on opposite sides, one forms a means of re-action for the other, so that the drill-bar remains central, or nearly so, in the drill-hole.

MUDDY WATER CLEARED BY ALUM.-A comparatively small quantity of alum will clear muddy water. A piece as small as a hickory nut, or even less, according to the impurity of the water, It has simply to be dissolved, stirred, aud This method is frequently adopted wili precipitate the dirty colouring matter in a pailful of water. left to settle. along the Missouri and Mississippi rivers. In the manufacture of lakes used in painting, the dissolved rests upon the peculiar property of alum to combine, when in solution, with the most foreign particles in colouring matter is precipitated by alum. All this suspension or even solution.

PORTABLE MOTIVE POWER.-A correspondent of Nature draws attention to an important discovery made by an American, which bids fair to supply the want of a portable motive for machinery. At the last expedition of the American Institute, it seems, there was shown an ellipiic lockstitch sewing machine driven by an electric engine small enough to fit into a common hatbox. A series of eight magnets are set on the periphery of a circle, and around these revolves an armature of steel which is continuously propelled by the magnetic action, and thus operates the machinery that moves the needle. Connection with this motor is had by means of a small slide within reach of the operator, at whose will the current may be cut off entirely or the speed of the needle graduated, as may be desired.

DR. ANGUS SMITH ON THE CHEMICAL EXAMINATION OF AIR.-Dr. Angus Smith read a very important paper at a meeting of the Association of Medical Officers of Health held last week. The subject, says the Medical Times and Gazette, was the "Examination of Air," and the most striking feature was the announcement that he had detected and measured the nitrogenous organic matter in different kinds of air, and that between country air and the air of towns or of close rooms there was a most marked difference in this respeet. The process adopted by Dr. Smith was very novel and ingenious. It consists in shaking up a small quantity of perfectly pure water with a measured volume of the air to be examined, by which operation the organic impurity of the air is transferred to the water, which is afterwards The author of the paper analysed by the ammonia process invented by Wanklyn, Chapman, and Smith expressed great confidence in the results he had obtained, and said he would not scruple to ask for the demolition of all crowded courts in towns, the atmoscontaminated air. phere of which presented the characteristic signs of

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