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DIAMOND ROCK-BORING MACHINE AT THE CROESOR SLATE QUARRIES (described on page 367).

TO MILLERS.

revolve, when the end A will be depressed and the end IB elevated to a considerable distance from the original horizontal position, in obedience to the law of centrifugal force, by which, of necessity, the heaviest portions of the outside extremes of a revolving object tend to the furthest point from the centre of rotation.

SIR,-In common with others of my profession, have watched the discussion in your columns on the subject of mill-stone balancing with much interest; nevertheless, it is by no means clear to me that the subject has been satisfactorily disposed of, either in favour of the supposed perfect unity at all times of the standing and running balance, or in favour of the other position-namely, that the standing and running balance are not necessarily identical, but may vary under certain circumstances.

It has always appeared clear to me that, with the present construction of mill-stones, it is theoretically impossible to secure perfect unity of both standing and running balance-that they should exactly coincidebecause the size of the "burrs" is never the same precisely; and, to satisfy myself more thoroughly, I resorted to the following simple experiment, which occupied only a few minutes, and if repeated by my brother millers, I feel convinced they will find in it an explanation of the difficulty:-Procure a rectangular piece of wood, of a shape similar to that indicated in the annexed sketch (say 5in. long by lin. square) A B.

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This is hollowed in the middle to receive an upright support say the top of a pencil-E, slightly impressed into the timber to make balancing the easier. On either end, one above and one below, as in the drawing, is fixed a piece of lead or other heavy substance (a quarter-ounce weight will do if well tied on), of equal weight, C D. When the whole is balanced nicely as in the illustration, the timber is supposed to be perfectly horizontal. Now begin gently to blow with the breath at one end, so as to cause the timber to

The application will be obvious. Suppose the timber to represent a section of a millstone, and the dotted lines surrounding A and B the burrs; now these are of much greater specific gravity than the plaster which covers them. The one (A) is much deeper than the other (B), and therefore nearer the top-the one B, is thinner, and nearer the bottom; therefore the centre of gravity of A is at a little distance above that of B, considered in relation to the horizontal. Burr A is, therefore, represented by the weight C, and burr B by the weight D in the experiment, the timber representing the plaster of the stone; the difference being that I have purposely exaggerated the proportional distance between the relative positions of the centres of gravitation of the heavy part of periphery, in order to make the principle clear; which principle is in no way affected by being presented in an exaggerated form, because, whether the vertical distance between the centres of gravity of the burrs at opposite sides (considered relatively to the horizontal) be 2in. or 2ft., the disturbing cause is the same per se namely, the influence of centrifugal force, as before mentioned.

If I have made myself understood, I think it will be apparent that a standing and running balance may not be identical under all circumstances. [11]

F. DAVIS.

CAPE HORN, GOOD HOPE, AND PORT JACKSON.

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with prepared chalk on the globe, and found that the complements of the latitudes, and the differences of longitude were as follows: PH = 34° 1, PG 55° 36',

H

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Thus we have two sides and the included angle, and the question is to find the third side. Perhaps some other of your correspondents might bring the figures nearer to M. L's." results. I am not mariner, nor have I, at least for some time, had an opportunity of meeting with any one who has computed the distance by sen, but I should imagine the course H J could not be accomplished, the route being too near to the south pole.

By the bye, sir, as you have invited letters on summer pastimes, would not one of your correspondents give us a few remarks on the art of swimming, so useful both to mariners and every one.

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FLUTE FINGERING. SIR,-A correspondent complains of the bother of flute fingering in extreme keys, by which I suppose him to mean the flat keys. But is it possible, in these days of sliding heads, that anybody submits to the bother of making the flat notes independently as they come? Supposing your correspondent has to accomin-pany a piano, the music being in D flat, he should, by means of the slide, tune his D to the D flat of the piano, and then play the notes as though they were written in the key of D, with two sharps, which is the natural scale of the flute, and causes no extra fingering

SIR,-One of your correspondents, "M. L., "has computed by spherical trigonometry the distances between these three places, and is desirous of having his results verified. He makes HG 4,135 miles, GJ = 6,824 miles, H J = 5,831 miles [see page 332]. I was duced to try them at his request, and I make the results somewhat near, but not exactly. This may possibly arise from not taking the same latitudes and longitudes. The way I proceeded was this: I made the triangle

whatever. Exactly the same sounds will be emitted as if he had elaborately flattened each note as it occurred. The reason is evident-by drawing out the slide he flattened all seven notes. But the staff directed him only to flatten five, B, E, A, D, and G; therefore he has to sharpen the other two, F and C. For the same cause, with the flute so adjusted, six flats is to be played in one sharp, four flats in three sharps, three flats in four sharps. It may appear to the uninitiated as if it would be easier to play in three flats than in four sharps, but it is not so, for in the first case C and have to be made natural, making, with the signature in the staff, five notes to alter; in the latter case there are only two to alter, the other two being in the scale; only in using this mode an accidental flat must be played as a natural, and an accidental natural as a sharp, because the natural note is flat to the sharp, and sharp to the flat. With a sliding head a flute requires but four keys, the D sharp, E sharp to make F natural, the G sharp, and the A sharp. All others are mere surplusage. If the music leave the flat key for a natural without there being an opportunity for fresh tuning, make before starting a nail mark on the tube at the length for the natural note: the composition with which it is made to go smoothly will take it. I hope these directions may bring some relief to perplexed fingers.

T. S. G.

SEWING MACHINES-REPLY TO "GROCER."

SIR,-That a Thomas's shuttle will work best with known. The instruction books teach it. I have not the thread unwinding from the under side of reel is well recommended the reverse, and although the drawing shows it reversed, it was done intentionally, believing it would be easier to comprehend so illustrated. Thus far I beg to thank "Grocer" for pointing out the error, but entirely disagree with him as to making the reel." Firstly, in practice the brass end of a shuttle "spring long enough to catch the brass end of shuttle reel is usually far from being a true circle. Secondly, the spring pressing upon an irregular form must give an irregular tension. Thirdly, if the brass end of a shuttle reel had a true circular form it would be inferior to the short spring to give a regular tension. Fourthly, because when the reel is full of cotton it pulls off easier between the diameters. than when it is nearly empty, owing to the difference When full, the diameter being largest, affords a greater leverage to turn the reel when the cotton is pulled off. A full reel of cotton or strongly the pulling off, but as the diameter of the thread presses strongly against the spring, and resists thread diminishes, diminishes, and thus 80 the resistance of the spring action caused by the using, and diminishing the diacompensates for the irregular meter of the reel of thread. It is, therefore, far superior to a constant uniform pressure of the spring on the THE LUNAR CRATER-" ALPETRAGIUS D." brass end of shuttle reel, which cannot compensate for SIR,-Mr. Michell Whitley, of Penarth, Truro, a very the varying strain on the shuttle reel when nearly full careful observer of lunar objects, has addressed a letter or empty. "Practical Man" recommends a short to the editor of Scientific Opinion (see No. 85, June 15, spring, as represented, to any one who would make a 1870, p. 258), containing his observations on June 8, shuttle for himself (but it is far more economical to buy 1870, of the spot " Alpetragius d," (not the Greek Delta one), and further recommends the kind of reels to their as printed, but the Roman d), in which he speaks of a respective shuttles, as illustrated at page 157. minute blow hole in the centre of the white spot now "Grocer" is in favour of a Singer reel, because if occupying the place of Beer and Madler's crater. I am the reel is not pressed firmly down (in the Thomas's not aware of anything having been published on this shuttle) the hinge goes behind the end of the shuttle spot since my article in the Student, referred to by Mr. reel and shuts it out, instead of in." If "Grocer" Whitley; but at the close of 1868, and in the spring of found this to be the case two or three times with per1869, I received communications on it from the well-sons he sold machines to, what would he expect to find known observer Mr. Knott, of Cuckfield, and shall feel if he applied the Singer reel to a long shuttle, or a obliged if you will kindly give publicity to the follow- No. 1 Thomas for shirt collar work, where the best stitch ing extract from his letters:is required at the highest speed? The latter part of description and illustration of machines about to appear "Grocer's" remarks will be best replied to by the in a systematic manner; and nothing could be more unfortunate to those who seek a thorough knowledge of the subject, than to introduce haphazard the whole or part of certain sewing machines of doubtful merit, or to use valuable space merely for advertising purposes without payment.

[18]

to report to you the result of an examination of Alpe“December 24th, 1868," Mr. Knott says, "I hasten tragius d' last evening, which adds one more to the points of resemblance between it and our old friend Linné. Observing with my 74 in. Alvan Clark refractor and a negative eyepiece magnifying 424 times, I detected on d (which appeared as a bright soft edged spot) a minute craterlet, with a diameter barely one-half that of B and M's little craterlet on the south. This is evidently the same object as is figured by Lohrmann on his unpublished plate (see Student, vol. ii., p. 48, plate) referred to by Sehmidt." On February, 20, 1869, Mr. Knott again examined this region, when he distinetly saw the craterlet as a crater, and estimated its diameter as equal to half that of B and his little craterlet on the south.

It is exceedingly gratifying to find three such observers as Schmidt, Knott, and Whitley agreeing so closely with regard to this spot, all three placing B and M's little craterlet on the south edge of the white spot, and the last two finding an exact resemblance to Linne in its three main characteristics, as observed since October, 1866. I hope many of your correspondents will often turn their telescopes upon it, that these features may be closely watched. It is situated to the east of the two undesignated craters eastward of No. 205, on Webb's map; the largest is Alpetragius d of B and M, the smallest B. The colour of the interior of B is darker than given by either Lohrmann, Beer and Mädler, or Schmidt.

Your correspondent Albert P. Holden will find recent estimations of the distance of Xi Ursa Majoris by Messrs. Whitley and Ingall, in the above quoted number of Scientific Opinion.

W. R. BIRT.

Cynthia Villa Observatory, Walthamstow. [14] BICYCLE RIDING. MEDICAL OPINION WANTED. SIR, I wish to ask a favour of some of your medical readers, and though it is like a sort of consultation gratis, yet, as it is a question of universal interest at the present time, it may not be considered asking too

much.

Several individuals who have never "risked their

[16]

A PRACTICAL MAN.

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I pass over his remark that he cannot follow my reasoning in a certain chapter, with the simple com ment that from Sir J. Herschel (who has done me the honour of indicating special approval of this very chapter) down to the least instructed reader, not one I venture to assert has found any difficulty in mastering roomy. the reasoning, save only the Savilian Professor of As assertion that "Laplace, the elder and the younger The gravamen of my charge rests, however, on his Herschel, Humboldt, Admiral Smyth, Sir William Thomson, Mr. Tait, Dr. Balfour Stewart, Profesem Tyndall, and other honoured names, all in their tor come under Mr. Proctor's adverse criticism, with greater or less severity." This assertion is inexact. If the remark that one does not agree with this or that opinius of such and such a person, be rightly described as "eriticising that person with severity" then I am ope to Professor Pritchard's charge; if not, then there is truth in it.

But a type of my severity was wanted, and Professor Pritchard, with as much dexterity as though his trade were hack-reviewing, conveniently makes one. There is one sentence, which, taken apart from the context, sounds severe. Whewell had spoken of Jupiter as a watery globe with a few cinders perhaps at its centre. nomer worthy the name" can regard Jupiter as it was I remark in "Other Worlds," that surely "no astromembered, was not an astronomer." But then I go on to thus regarded "by one who, be it thankfully reindicate in what sense I use the word astronomer. "He," I say, "who has not gazed hour after hour on the glories was not an astronomer in the sense in which I wrote. For of the giant planet," &c. Every one knows that Whevell the larger portion of his attention was directed to quite other matters than astronomy, and it is simply true, that he was not, properly speaking, an astronomer. as he himself admits in his "Plurality of Worlds" Fortunately I have spoken with far too obvious appreciation of Whewell's wonderful abilities for my meaning in this passage to admit of being misinterpreted Mr. Lockyer's views about the corona "simply because by others than Professor Pritchard. Professor Pritchard then goes on to say that I attack they do not square with mine." He knows perfectly well why I attack them; for I assign very definite reasons. insufficient, because, if he did, he would lose all title to He would not venture to assert that those reasons are be regarded as a mathematician.

Equally clever is his quotation of a passage having reference to the theory of the meteoric origin of solar heat. I write "I am quite certain that there is no flaw in the evidence I have adduced from the laws of probability; and that," &c. But it suits Professor Pritchard's purpose to make it appear that I am only expressing over confidently a mere opinion so he quietly drops all reference to the evidence, and makes me say, "I am quite certain that at least an important part of the sun's heat, &c." He immediately adds, "we may fairly ask whence has Mr. Proctor this certain know ledge," &c. Yes; but if he had quoted the sentence in full, it would have become unpleasantly obvious that one had only to turn to Other Worlds" to find out whence Mr. Proctor derived his conviction.

It is well known that Mr. Lassell, the eminent and

VELOCIPEDE CONSTRUCTION. SIR,-Each maker-amateur or otherwise-seems to me to judge of his and other machines by the rate he can go on it. Now I think that is an erroneous test, for I saw a machine, horrible in appearance, construction, and principle, propelled at as great a rate as thirteen miles an hour (which for tricycles I believe to be the maximum rate), only the driver was a strong swarthy fellow, and exerted his utmost. It is there fore not to be wondered at that "A Pattern Maker" should think "the whole stock of velocipedes up to nothing when put really to practical work, and particnlarly in a hilly district." After describing a veloce the usual finis is "that it can be made to go fifteen miles an hour with ease," which, by my criterion, is folly. skilful astronomer who is the present President of the I grant that these machines can be made to go at that Royal Astronomical Society, considers that Uranus rate, and uphill, but it is practically "no go." I have has only four satellites; for he can see but four with his practised the bicycle for a year in a hilly district (com-Proctor," asks Prof. Pritchard, "venture to set his splendid reflector at Malta. "How then can Mr. pared with many in England a very hilly one), and can keep my saddle over most of the hills without difficulty, but the labour is excessive. I would judge of a good machine by the "ease" required to propel it eight or at most ten miles an hour, to gain which lightness, combined with simplicity of construction, height of wheel, india-rubber tires, and yielding springs are the necessary things. Loose and light clothing is also very sirable for summer riding. But in my opinion, to rattle over the ground at the rate of one mile in four roads is sheer folly, and undoubtedly more so with a minutes on any but a first-class machine with even tricycle than a bicycle. One of the chief ingredients of pleasure is ease, I take it; and as veloces are at present used chiefly for pleasure, the further we exceed ten miles an hour so much do we lessen our pleasure. Another thing that I am sceptical about is the common dogma that the driving wheel ought not to be more than the MECHANIC, yet to my knowledge has never been dis86in. or 38in. It is being continually brought forward in two and three wheeler is very correct; but I don't see readers. The little S. James (page 309) says on the why the driving wheel should not be as large as the enough to "show cause why" I should believe the common dogma he will very much oblige. HUSBAND. [17]

opinion" (that there are eight at least) "in antagonism," &c, &c. How indeed? But suppose Mr. Proctor wrote thus-"Four of the satellites discovered by fied; but one cannot read the account of his method Sir Wm. Herschel have not indeed been yet identiof procedure without feeling that no amount of mere de-negative evidence can be opposed effectively to the positive information he has left us respecting these four orbs." Does not this somewhat alter the aspect

of matters ?

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Then what am I to think of his quoting a printer's blunder (obviously so from the context) as only probably an inadvertency? On page 41 of my book are these words "a glowing vapour gives a spectrum of white lines," where it should be bright lines"; but within a few inches, on the same open paging, are these words-"They tried the spectra of glowing vapours. and they found bright lines of various colour." He then goes on to speak of "an alleged breaking of a dark actually happened; and somewhat spitefully adds "these (two) misstatements are easily corrigible in a second edition, presuming that they are not typical of fairly conclude that Prof. Pritchard had not read the volume, and was therefore hardly in a position to criticise it.

necks on bicycles have occasionally grumbled at the many letters respecting such machines; but I am sure not one of them would object to space being given to determine whether their use is, or is not, injurious to cussed, but seems to be quietly swallowed by brother glass " where I have spoken of no such event as having

their numerous riders, and whether the strain on the abdominal rings is or is not so great as to cause ruptures, &c.

I am aware that a letter appeared about this some leg will admit of. If, however, any one will be kind much else in the volume itself," from which we may

six months ago, in your columns; but there was only
one reply, and surely on such an important question as
this we ought to have a more general opinion. I have
heard that in five years it is considered that a bicycle
rider would be completely ruptured with daily practice.
I of course cannot vouch for the truth of this myself;
but I had it from medical quarters. What a calamity
it would be if, in about that time from the commence-
ment of bicycle riding, all those who frequently used
the machines were served in this way. I therefore
request opinions on this important point, with the
editor's permission, and also, whether the use of a broad
band round the abdomen would be sufficient to prevent
such consequences. Perhaps, also, velocipedes which
drive by levers with a horizontal motion may be free
from this objection. It would be well to know this, and
if they are not, the only safe velocipede would be one
propelled by the hands.
[15]

S. JAMES.

UNFAIR CRITICISM.

SIR,-It may seem unwise to refer in the pages of the most widely circulating scientific journal in England, to adverse criticisms in a contemporary of minute circulation. But I look at the matter in this light. Professor Pritchard has chosen, in reviewing my "Other Worlds," to make certain charges against me in Nature. If these charges are true they ought to be more widely known than they can possibly be while confined to the columns of Nature; if they are not true my countercharges ought to be more widely circulated. I deliberately assert that Professor Pritchard has written a more discreditable review than any which the veriest hack-critic would have penned. I have no doubt, as I have written to him, that he is "by this.

I am sorry to have to comment severely on Prof. Pritchard's conduct in this matter. I cannot at all understand why he should be irritated against me; but it is clear to me that nothing but some irritation could have made him so forget himself. If I had attended the meetings of the Astronomical Society when he was president, I should imagine he gave me credit for some of the anonymous attacks which were so freely made on his school-masterly reading of the part of President. But I was not. A year ago I had occasion to remark at one of the meetings of the Royal Astronomical Society, that in commenting on a paper of mine, he had "begged the whole question" at issue; but surely so small a matter as that cannot have angered him for a whole year. Tant ne, &c. ? [18]

RICHARD A. PROCTOR.

INDIGO.

SIB,-The samples of indigo which I have had the pleasure of sending you were extracted at Accra, on the west coast of Africa, from a species of plant known as Indigofera. Tthis plant grows in great abundance on the west coast, more particularly on the Liberian or grain coast, where there is great quantities. Merchants who trade to the coast seem to have entirely overlooked the benefit to be derived by the cultivation of this valuable dye. Several important things have to be observed in collecting the plant fit for fermentation. The modus operandi is similar to that which I have carried out in the East Indies, excepting that the maceration is useless in this case, and that the fermentation takes about 26 hours. The indigo when precipitated has a greenish tint, which may be destroyed by being boiled with one part S Os to 30 parts of water, which entirely destroys the chlorophylle (which gives it that tint), and renders it similar to that which I have sent you. Market value of the dye at the present moment is quoted to me by one of the first firms in the trade at 7s. 6d. per lb.

I hope to have the pleasure of submitting to you
samples of cloth manufactured by the natives of
Benin, and dyed with the indigo.
R. F. GARTH.

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SIR,-I am anxious to obtain information on some matters connected with electricity; and I write to you in hope that “ Sigma," or some other of your corre spondents, may afford me the information I desire.

It is well known that magnetic currents in the same direction attract one another, while those in opposite directions repel one another; and also, that currents converging to or diverging from the same point attract one another, so that if A B, C D, Fig. 1, be two similar wires, along which currents of equal quantity are passing, and which can move freely about

a

FIG.

D

*

their middle point O, they will
swing round into the position
O X, where O X bisects the Bo D.
Now I wish to know if these facts have suggested to
any experimentalist the idea of a parallelogram of cur-
rents, analogous to the parallelogram of forces or of
velocities.

I have neither the time nor the skill to make such delicate experiments as would be required, myself; but I will state what I conceive would be the enunciation of such a theorem, and I should like to hear whether my statement represents an established fact. This then is my ideal statement.

If two rectilinear currents cross one another, and a magnet or solenoid be placed so as to bisect the shortest distance between the two, it will take up a position as though it were acted upon by a resultant current, whose quantity and direction may be estimated as follows:

Let Az, By, represent the directions of the currents,

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A

X FIG. 2.

and let AB be the shortest dis-
tance between them. Bisect
A B in O, and draw O X, OY,
parallel to A, By, making,
OX: OY: quantity of elec-
tricity passing along Ar: quantity along By.
Complete the parallelogram X Y; then O R will re-
present the resultant current in direction, and its
quantity will be represented by
20 R
A B
In the figure the magnet is supposed to be placed at O,
and if the theorem be stated correctly the magnet would
take up a position at right angles to OR. If this were
found to be correct by experiment, the theorem would be
proved as regards the direction of the resultant: to
prove it as regards the quantity of the resultant would
require a delicate galvanometer.
[20]

R. P. S.

AIR PUMP.-INDUCTION COIL. SIR,-I beg to thank the two correspondents who have answered my inquiries about the Air Pump; though, as I feared, they have not given me any information beyond what I already knew. The first one has simply given a description of Tate's pump, a form well known; the other describes nothing more than an ordinary exhausting syringe, which, I have ascertained, is sufficient for the vacua required for the experiments mentioned by me in my letter, but utterly useless for higher vacua. I thought, among your numerous correspondents, there might be some who have gone in for the subject in its higher branches, and who could and would give me the

result of their experience.

there is nothing original about it; it only remains for
me to describe the method of its construction, which is
peculiarly simple. I have about the same weight of
secondary wire as that mentioned by A. Farquhar; but
as my wire is No. 36, I have a much greater length.
No. 28 is too large to produce length of spark, though,
with proper insulation, it ought to give great density;
but, in my opinion, it is much too thick. Mr. Farquhar
may find his coil, with its imperfect insulation, answer
with small battery power; but I caution him not to try
four or five cells, or else he will find it come to grief;
for cotton covering and shellac varnish is quite insuf
icient, even when constructed, as I presume his is
(for his description is not at all clear) on the vertical
method. My coil, with one cell, the platina about 2in.
by 4in., gives a good dense spark at 14in. surrounded
by a thick aureole; and the spark I get at from 3in.
to 4in., is sharp, bright, and zig-zag, not straight and
thready. I have tried it with a mercurial break, but I
cannot get nearly the same length of spark as I can
with the vibrating spring; the cause of this I am unable
to comprehend, not having had any experience with
this form of break.

In conclusion let me advise those who are thinking
of constructing a large coil, not to think of the old
horizontal methods with gutta percha insulation: they
are a delusion. I do not say they cannot be made,
because they have been and are; but they are always
likely to break down, and then they are done for. While
on my plan they cannot break down, and much greater
results can be obtained with small battery power, which
I consider to be one of the great desiderata.
INDUCTORIUM.

[21]

have got

TRADE AND COMMERCE.
SIR,-AS "Herbert" has written you a third letter
before my answer to his second one appeared, I must
again trouble you with a few lines in self defence. I
"Herbert" into a little corner; and although
he fights fairly and manfully, I cannot make up my
mind to let him out until he proves his case, or ac-
knowledges his error. He assumes that trade is barter,
with the corollary that the balance of imports over
exports is profit. Upon this point he must stand or
fall. I have endeavoured to prove the contrary, and
cannot consent to accept as an axiom that which is
really the point in dispute. It is in vain that he builds
elaborate edifices upon this basis, until he prove that

it is a sound foundation.

At page 306 Herbert" says that even I (F. W. M.)
can see that when a foreign-made article is purchased,
part of the money goes to the foreign workman, but
equivalent sum, which comes into the pocket of an
that I cannot see that some foreign gentleman pays an
English workman. My inability to see this does not
of The Critic Tilburina was not to blame because she
arise from shortsightedness. In the well-known play
called forth the rebuke, was that she professed to see it
could not see the Spanish Fleet-her failing, which
when it was "not yet in sight." The case would be
exactly as "Herbert" states, if trade were barter, and
trade were free, but the first condition is disputed-the
second unfortunately does not exist. The real state of
affairs is just this:-The foreigner, having received
£29 for his goods, is willing to spend that amount upon
English manufactures, but his government has laid a
restrictive duty upon these; and if he buys them in spite
of the duty, his £29 goes somewhat after this fashion,
so that the Englishman gets but £18 back against his
£18 for English goods, and £11 to the State for duty;
£29 expended and sells but £18 worth of goods against
so as to embrace the whole of the foreign trade of the
the £29 worth that he buys; or, to extend the example
country, England buys from the foreigner £294,693,608
worth of goods yearly, whilst he is unable to buy from
her more than £179,677,812 worth in return.
Rymea
this indicate?"
may well ask "What sort of prosperity does
"Herbert" is fond of similes. I will
give him one as a counterblast against his "cargo."
Suppose the nation to be a business firm which buys
and consumes every year £29,000 of goods and manu-
factures, and sells but £18,000 worth. Is this firm
doing a profitable business?

"Saul

Last week there was a discussion in the House of
Commons on the subject of "Unemployed Labour,"
which was very interesting, although unsatisfactory in
its result. We may, according to our several pre-
judices, believe, with Mr. Torrens, that the country is

in a state of destitution and misery, or with Mr.
Goschen, that it is prosperous and happy; but above all
differences of opinion, beyond all contradiction, looms
port its people.
out the damning fact that the nation is unable to sup-

brought with it a corresponding increase of work, and There was a time when increase of population What I want is a pump that will produce a vacuum portion to the increase. the nation was stronger and more prosperous in proAll this is changed now, and equal to about one-twentieth of an inch of mercury, it is a suspicious circumstance that the change should and I know that the expensive class of pumps sold for date from the period when, through the influence of this purpose and they are indeed expensive-are made Free Trade, our imports have commenced to be much with a single barrel. It was the construction of one of in excess of our exports. Some of your correspondents these that I wanted to elicit from some of our scientific regard the necessity for emigration as a proof of our friends. There is a plan of Grove's called a repulsion prosperity. It is an unfortunate time for a nation when pump, that I have read about, which I believe is very the symptoms of weakness and disease are looked upon good, but I do not know the particulars sufficient to as proofs of healthiness and strength-when the hectic work by.. I am now constructing one on my own plan, flush of consumption is mistaken for the rosiness of about which I am rather sanguine; still I shall be very health, and the nation disports itself in a fool's parathankful for any useful information on the subject. dise, unconscious of the disease which is destroying its With regard to the induction coil mentioned by me, I constitution. shall be very glad to give a full description of its construction if you, sir, think it of sufficient interest; or I will give it personally to any inquirer if they write to you for my address. I have had the opinion of a celebrated electrician on it, and he tells me it is a marvellous success. It is constructed on the vertical plan-so far

the working of Free Trade, and ought now to be in a
We have had five-and-twenty years' experience of
position to judge of its effects.
mission, appointed to investigate the subject, could not
A Government Com-
fail to bring to light many interesting and instructive
facts, but there is little chance of such an appoint-

ment. The great apostles of Free Trade-those who persuaded us to shut our eyes, throw open our ports, and see what fate would send us, have made an enor mous reputation thereby. By the majority of people they are worshipped with a devotion which does not fall short of bigotry. Any attempt to question the infallibility of their wisdom is at once drowned with cries of derision. Their followers are as certain of their case, and as intolerant of opposition, as were the opponents of Galileo in their belief that the sun revolved round the earth.

Were it once proved that their commercial policy was wrong, these great men would be in danger of losing the vast reputation they have acquired; and although we must credit them with every possible honesty of intention, yet as every one sees things through spectacles more or less coloured, it is possible that such a consideration as this might deepen the couleur de rose of their spectacles sufficiently to conslowly but surely overspreading the aspect of affairs.

ceal from their vision the blueness of tint which is

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SEWING MACHINES. (Continued from page 281.) primary, continuous, and essential motions for making SIR,-In a shuttle lock-stitch machine there are four the stitch, and three adjustable or moving parts to regulate the stitch. These may be classified as follows:

1. The Needle Motion.

2. The Shuttle Motion.
3. The Feed Motion.

4. The Main Shaft and Driving Wheel.

The first three motions are not uniform, either separately or combined. Attempts have been made to obtain uniform motion to prevent noise, or for some supposed advantage, but such changes from the correct motions entail certain disadvantages.

The machine must be fitted with
5. The Tension.

6. The Thread Take-up.

7. The Stitch-screw or Regulator.

Some machines require, in addition, other parts, as a Presser and a Lifter, when the under-feed is used. The usual terms will be used in the description of sewing machines, so far as practicable; but to prevent confusion when comparing them, certain changes are necessary. For example, it is usual to speak of the frame or bed on which the shuttle slides, as the shuttle race; this bed being immovable it is not appropriate to apply the term race to it. By using the term shuttle path, it will apply without confusion to a straight, curved, or oscillating shuttle movement, either sliding

or carried.

To the courtesy of the Howe Machine Company, of following illustration of the first machine invented by 64, Regent Street, London, we are indebted for the kinds of clothing on it at the rate of 800 stitches a Elias Howe, jun., the late president, who made many minute. The idea of this invention was worked out in a rough model of wood and wire, in October, 1844. In July, 1845, he sewed by his first machine the seams of two suits of woollen clothes. In 1867 the same machine was displayed at the Paris Exhibition. A model of it may be now seen at the Museum of Patents, Sonth Kensington.

It is not a little perplexing to find the invention of the sewing machine claimed for France, and a tailor making army clothing. the inventor, who had many of his machines, in 1841,

The mob, it is stated, in the Revolution, ruined the and sent him to die at Amplepius in great poverty. establishment in which the inventive tailor had a share,

If there be a shadow of truth in this statement that

army clothing was made by a French sewing machine four years earlier than Elias Howe's successful working of his machine, surely we ought to have sufficient evidence of so important a fact. Are our neighbours in France so careless of the reputation of their countrymen when most deserving? Is it wise to bestow so much glory on war, and leave the hero who conquers in the arts of peace to die in poverty, unrecognized?

If the story of the inventive tailor will bear investigation, we appeal, as "English Mechanics," to "French

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Mechanics," to perform their duty, and let us have the particulars of the machine, that it may be illustrated in Our English Mechanic," and duly honoured. If the story be a myth, let it be dealt with so that it may not be further circulated by being copied in the public press as an established fact.

A close inspection of Elias Howe's first machine will An eye-pointed needle passed the thread from a reel show that he embodied all the essential movements. and the shuttle passed through it, the needle being through the fabric, then the needle loop was formed, pulled out of the fabric and the stitch tightened, when both needle and shuttle came to the end of stroke; the feed then advanced the fabric the length of stitch, the shuttle travelled back, and the needle again penetrated the fabric to make another stitch. In the illustration it will be seen the fabric is placed vertically on pins, the pins being connected to a rack plate which moved a given distance, stitch by stitch. When the rack had travelled its full stroke it had to be placed back to commence afresh, the fabric being at the same time readjusted on the pins. This feed motion appears now very awkward. It was used in other machines in the early attempts; and I have seen a rack, and the bed of the machine, a yard long, so that one yard could be stitched without stopping to readjust the feed.

All the essential motions were transmitted from the ing wheel, behind the fabric and above the machine. main shaft, on the end of which may be seen the drivOn the main shaft may also be observed the cam, having the same kind of action as that attached to the

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modern Howe machine, an illustration of which will follow, and prove to satisfaction that Elias Howe deserved all he received of wealth and honours.

ERRORS IN ILLUSTRATIONS.-At page 281, Fig. 4, the spool case is represented resting on the end of the upright shaft g. In such a form the needle thread would not pass between the spool case and its bed. The surface of the spool case and its bed should be as smooth as possible to allow the thread to pass in the manner described. At page 157, Fig. 9, the thread is represented passing over, instead of under the reel. It works much better under the reel, but may not be so clearly understood by the thread being hid below the reel. The shuttle should be made in all respects as represented in the illustration, Figs. 9 and 10. A PRACTICAL MAN. [23]

HOW TO TRISECT AN ANGLE. SIR,-I have read with interest the letters of your correspondents, F. C. Penrose, June 24th, and "O. H. S.," June 3rd, on the subject, "How to trisect an angle."

you gave a sketch of the of June 10th, wherein "Boehm " Flute. The flute represented is the "Equisonant," which your correspondent "Sable" describes in his letter.

From Carnarvon a walk of ten miles brings the tourist to Llanberis, and he then has an opportunity to ascend Snowdon. A capital way of doing this is to ascend the Pass of Llanberis, and climb I should like at the same time to remove the impres the mountain by what is called the Capel sion which, it occurs to me, "Orion" intends to con Curig Path, descending on the opposite vey by his letter in the ENGLISH MECHANIC of June 17 side to Beddgelert. Here the tourist has-i.e., that the Clinton flute is being abandoned in a choice of roads, and the way I chose consequence of its inferiority to the other instrument was on to Capel Curig, a distance of nine he specifies. miles. While at Beddgelert, visit the In his attempt to do this he makes an unfortuna pass and bridge of Aberglaslyn, and at admission, as two extracts from his letter will show. B Capel Curig the falls of the Ogwen. says, "I was induced to read Clinton's essay on his personally I know nothing of it." Itar From Capel Curig to Bettws-y-coed, flute. As to his other asaand thence to Llanrwst. Here the tourist his reading benefits him little. may complete his tour by walking to Con- tion, I think he would have some difficulty in producing way and Llandudno, thus completing the one instance of the Clinton flute having been "alar circle, or he can extend his tour in the doned" after it was once fairly adopted. same manner I did, by going on to Denbigh, St. Asaphs, Rhuddlan and Abergele, calling, on the way between the two latter towns, to inspect the beautiful church at Bodellwydan.

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This tour occupied me about nine days. It would be impossible to enumerate all the objects of interest along the route, but the tourist should provide himself with a guide book, in which he will find interesting notices of every object worth mention.

Several of your correspondents enquire the most economical way of doing a trip; should suggest to them to stay each night at a good hotel, breakfast there, and then, during the rest of the day, eat and drink when they require it, and where they can get it. Another plan is to take cheap private lodgings at some central town, and from thence make day excursions through the surrounding district. If they wish to do it very cheaply, they must cater for their own eatables, &c., &c., and take a good supply out on each excursion. In the course of a month, I intend taking a walking tour in the lake district of Cumberland and Westmoreland, when I expect I shall adopt the former of the two methods I recommend, with the addition of a good dinner at an hotel each day. Should any reader of the ENGLISH MECHANIC be disposed for such a tour I shall be glad to hear from him, with a view of going together. I have not yet met with a companion, and I think it decidedly pleasanter as well as more economical for two to travel together. My object is merely to enjoy the scenery, &c. I am no artist, botanist or geologist, but an ardent admirer of the works of nature. Should any one similarly disposed address me as below, I shall be glad to give further particulars. Donington, Spalding, Lincolnshire. [25]

B.

TOURISTS IN SCOTLAND. SIR,-The many readers of your scientific columns seem to be panting for a little recreation to their minds; and no doubt not a few of them meditating a tour, are desirous of knowing where to go. It is a well-known

That within the last four or five years, the "E sonant" has to some extent lost ground, I am not gether prepared to deny; but this is mainly attributab to the death of its talented inventor, who died just s he had perfected his instrument, and might fairly have expected to reap the benefit of the years of study, labour, and expense he had bestowed upon it.

Circumstances have since deprived the flute of that publicity, which in these times is so essential to snocess, and have given its opponents ample opportunity to d preciate its merits, which, nevertheless, are acknow ledged by all who have given it an impartial trial, and which have alone enabled it to maintain its ground as well as it has up to the present time. [27]

JUSTITIA.

SQUARING THE CIRCLE. SIR,-I quite agree with the remarks of Mr. H. W. Reveley, respecting the approximatively correct solution of the squaring the circle by mechanics! means; but it is open to him to supply a superior method of his own, on the principle of ocular demon station, as he has thrown no new light upon t subject. We live in a practical age and we are not up to ad infinitum. ARTHUR GEARING.

[28]

THE BICYCLE. SIR, J. Hare (p. 309) thinks I was rather hard on the bicycle by calling it dangerous, and informs me that he has performed journeys without a scratch. It was well for him that he had been so fortunate up till that time. That the bicycle with a few minor improvements will be the velocipede of the future, I by no means believe, but that it will have its day like longsleeved hats and chignons, and then become the bicycle of the past. If J. Hare, or some other practical bicycle rider, will give me information by answering a few questions, I in turn will give an account of experimental advantages and disadvantages of the three and four wheelers (the latter I believe to be the velocipede of the future). The questions are:Does it require much practice and care to ride without falling on a smooth road? On a bad road I have seen

May I suggest to them the following, which appears fact that Englishmen are more given to admire the them twist about right and left like a stream of water to me a solution of the problem? If I am wrong beauties of other countries than their own, or rather, running down a crooked brook; is that turning about

perhaps they will kindly set me right.

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TOURISTS' TRIPS.-NORTH WALES. SIR, I have read with great pleasure several letters in the ENGLISH MECHANIC on the subject of "Tourists' Trips," and I am very glad to see that there is evidently a growing taste in several, for thoroughly seeing the beautiful scenery which abounds in our own country, in preference to taking continental trips. It has occurred to me that an outline of a walking tour undertaken by me, through a part of North Wales, might be acceptable to the readers of the ENGLISH MECHANIC. From Llandudno to Conway, four miles, thence to Bangor, fifteen miles. From Bangor proceed to Beaumaris (only a short distance) by way of the ferry, and then on to Carnarvon (vid the Menai Suspension Bridge), passing on the way the Menai tubular railwaybridge. While at Bangor, the tourist should not fail to visit the Penrhyn slate-quarries, distant six miles.

neglect these to attend to others. I have met with men who have been round the world who have never seen the famed Scottish lake-scenery, though born within thirty miles of it. In Scotland our scenery is in many parts very fine, and those of your subscribers who have travelled in many lands without visiting it, will, I am certain, find it compare favourably with other countries in this respect. The Highlands of Perthshire, are, I can conscientiously say, a very charming retreat for the summer months, and to those who are from month to month shut up in smoky cities, will be found to be all that I have stated. I may mention a few towns where capital and suitable accommodation can be had either in hotels or lodgings-viz., Crieff, Dunblane, Blairgowrie, Pitlochrie, and Dunkeld. The drives around Crieff are very lovely; and those who are advocates or lovers of the water-cure, will find a fine hydropathic

establishment convenient and healthy.

At Dunkeld,

the wooded scenery is said to be the finest in Scotland; and the tourist in the summer months can get a four

horse coach running thence to Braemar, viá Blairgowrie and Spittal of Glenshee, passing through the

to keep them from falling? If so, and you are in a narrow road, meeting a carriage or wagon, is there a danger of running into the carriage? or falling when power turning a sharp corner (perhaps uphill)? is not over the machine lost, by the crank's being thrown out of proper position? and does the wheel rub the thigh? Is there a danger of thrusting the foot against or through the spokes? In treading the front wheel, sitting so far behind it, is it not like, and to be compared to, sitting in a low chair, placing the feet 18in. forward from the seat, then trying to rise up? Is there a danger, in jumping up when started, of pitching too far back on the saddle and doing yourself a personal injury? Are the accounts to be relied on that we so often see in the papers, of ruptures, &c., caused by riding the bicycle? How do you get it up a steep hill? would it make you dirty to lug it up if it was dirty weather? I took some luggage (10 years ago) on a four-wheeler 52 miles in 8 hours, I should like to know whether any one has done better with the bicycle.

[29]

N. G. LAMBORNE.

AN APPROXIMATE MODE OF RECTIFYING THE

E

CIRCLE.

F

beautiful scenery of Craighall, a few miles above Blair gowrie; but I would recommend those who wish to see Craighall in all its grandeur to put up in Blairgowrie SIR,-The following mode of approximately rectify. for a few days and go through the walks, which is kindly ing the circle may interest your subscribers. permitted by the proprietor on certain days of the week. I have seen Airlie Castle (the "bonnie house o' Airlie " famed in song), and Hawthornden, near Roslin, but Craighall is decidedly finer than either. At Braemar, the tourist will be within easy reach of the home of our beloved Queen, and can find her sitting in the parish church of Crathie, amongst the humblest of her subjects. I would also mention Drummond Castle, near Crieff, the property of Lord Willoughby D'Eresby, with its magnificent gardens and noble trees. This is the finest place in the county of Perth, and the estate extends to between 30,000 and 40,000 acres. There are also many other places in Perthshire where the tourist can spend an agreeable day; but I will not further intrude upon your space, but conclude by recommending to your readers the Highlands of Perthshire as an elysium for those desiring change of air and a "glorious quiet."

[26]

THE BOEHM FLUTE.

EPSILON.

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If the diameter of A B C D be 1ft., LG HEF falls SIR,-Will you permit me to correct an error which short of the circumference by about the fire hundredth appears to have been made in the ENGLISH MECHANIC part of an inch.

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CALLAN'S BATTERY.

SIR,-I should have written on the above subject last week, but I considered the query a personal one, and knowing "Sigma" to be able to answer most of the questions addressed to him, did not wish to trouble you with two replies when one would be sufficient. Finding that he has not heard of Callan's battery under that name, I trust you will find space in your next publication for the annexed description of one which I possess.

Some five years ago I had occasion to vapourize thick metal wires for some experiments I then had in hand, and finding that I should require enormous power, I naturally looked about for the cheapest mode of producing it. Platinum I found out of the question, and I therefore tried the system of Dr. Callan, and had forty round cells made in cast iron, according to the sketch I send herewith, their dimensions being 7in. high

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SIR, I send you an illustration of the pretty optical recreative toy known as "The Photoscope," made in Paris, but which may be procured of Messrs. Cassell, the publishers of the "Popular Educator." It consists of a conical tube, of which the base corresponds with a screen or disc, and is represented by ground glass, and the truncated apex of the cone is formed by the microscopical lenses and focussing arrangement. Fig. 1 shows the whole apparatus in elevation. A B is the conical tube, having the ground glass at the letter B, and the microscope slide-stage at A. In order to illuminate the object, the end of the instrument may be furnished with a reflecting mirror like the Hollander's apparatus. A light tin conical tube, T, open at the bottom, is fitted over the eye-glass at E, when it is desired to project an image of the object in the slide on the ground glass at B. The instrument is either held in the sun's rays so that they impinge upon the attached mirror, or, if the photoscope is shown at night, a piece of magnesium band is ignited at M; and whilst this brilliant light is obtained at M, the figure becomes visible at B if the lenses are carefully brought to focus by the lever at L.

In Fig. 2 the instrument is turned round so as to show the figure (not a rara avis) on the ground-glass screen at B. Of course some practice is required in

right position. It would be better to use a fixed magnesium lamp, which would prevent the unsteadiness arising from the movement of the hand.

B

E

The lenses used in this contrivance are shown in Fig. 3. The lens nearest the eye, or that to which the burning magnesium band is held, is a double convex, and is shown at A. The next is BB, the stage to carry the object, shown by the dotted line. C is a very small double-convex lens, of a short focus, which is moved towards A, or away from it, by the lever D. The diaphragm to reduce aberration is shown at E E, and being a very small aperture, it shows what great care must be taken to get the light exactly in the centre of the first lens, or condenser, at A. This optical arrangement is screwed on to the conical body, FF, which, as already stated, has a circular piece of ground glass fitted into the end B (Fig. 1.)-R. T. K. [81]

and 4in. diameter. Inside this cell I placed an ordinary porous one of large diameter with a rod of thoroughly amalgamated zinc in the centre. The outer cell was then filled with a mixture of equal parts strongest nitric and sulphuric acid, and the inner one with sulphuric acid and water in the proportion of one of the former to seven of the latter.

In order to ensure perfect metallic contact throughout, there were no binding screws throughout, but the wires were amalgated at either end, one being cast into the zinc rod, and the other dipping into a hole filled with mercury, which had been previously drilled in the projecting "lug" shown in the sketch of iron cell.

The reason of my making the upper part of greater thickness than the lower, is this: I found in practice that a great amount of wear took place at the surface of the liquid, and therefore by thickening that part the cell lasted much longer.

Now for the results-the battery being arranged for intensity, I used a copper wire fin. diameter, which was melted instantly with the production of a green cloud of smoke or vapour. Platinum wire of nearly 1-16th in. diameter ran into drops, but was not vaporized, mercury gave off a perfect shower of sparks with a slight report, and also such a quantity of vapour that it partially salivated a friend.

In the end I think I may say that it is nearly as powerful as Grove's; but it has the following great defects. While the acid in the outer cell retains its full power all goes well; but as soon as it becomes weakened, the action on the iron is so enormous that owing the ebullition the cell is in a few minutes almost emptied, while the fumes given off are something to be seen and felt before they can be appreciated. I would therefore not advise your correspondent to use it unless he make the cells double the height he requires, and then only half fill the outer one. Even then he will not have half the convenience of either Grove's or Bunsen's.

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[32]

T. S. CONISBEE.

MANGANIC SESQUI-HYDRATE.-WATER

ANALYSIS.

SIR,-"Manganic Oxide's" query in your issue for the 1st inst. is not very definite, as the principal fact is omitted. On what quantities does he wish to act? A method that will suit perfectly for obtaining a couple of ounces, may be absurdly unsuitable for manufacturing a couple of tons, and vice versa.

Therefore I forward him four methods, each of which is meant for operating on a different amount, and to yield a resulting oxide of various purities.

16 pounds, and would succeed best with half a hundredThe first is only suitable for quantities not under weight. In an open, or a reverberatory furnace, the oxide is to be roasted at a bright red heat, with small coal and coke, or charcoal and water, in the proportion of for every 100 pounds of oxide, 8 of small coal, and 5 of coke, or else 10 to 12 of charcoal, and 25 of water. After the oxide is well reduced, a current of steam is to be driven over or through the mass until it is nearly cold, and the whole exposed to the air and kept well wet for some days. Treated in this way, the red manganic oxide yields about 70 per cent. of the manganic sesqui-hydrate.

The next two plans are only suitable for obtaining rough sesqui-hydrate, for laboratory use, and are not suitable for large quantities. The method is as follows:

Place a mixture of 10 parts of manganic oxide, 2 of small coal, of nitrate of soda, and 5 of water, in a crucible, and raise to a red heat as long as carbonic oxide is disengage. Let it cool, lixiviate with water, wash well, and boil with twice its weight of water, next add five times its weight of sulphuric acid of about specific gravity 1.5, and boil until nearly the whole is dissolved, let it cool, and precipitate with ammonia, wash well, and let it dry slowly. When only a couple or so of pounds is required, this is a very good method.

The next mode is only fit for obtaining a few ounces at a time, and is the following:-A mixture of 10 parts of red oxide, 3 parts of peroxide of manganese, 6 parts of charcoal, and 1 of sodic carbonate, is to be raised to

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