TO MILLERS.

revolve, when the end A will be depressed and the end SIR,-In common with others of my profession, IB elevated to a considerable distance from the original have watched the discussion in your columns on the horizontal position, in obedience to the law of centrisubject of mill-stone balancing with much interest; fugal force, by which, of necessity, the heaviest pornevertheless, it is by no means clear to me that the tions of the outside extremes of a revolving object tend subject has been satisfactorily disposed of, either in to the furthest point from the centre of rotation. 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.

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.

PJ 56° 8, these form the sides of the three triangles; then the angle H PG 85° 49', G PJ 132° 45', and HP J 141° 27'. Thus we have two sides and the included angle, and the question is to find the third side. Perhaps some other of your cor

respondents 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 sea, 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.

P.S.-I make H G = 4,032 miles, GJ
and H J 5,828 miles.
[12]

=

T. S. H. 6,794 miles,

FLUTE FINGERING. SIR,-A correspondent complains of the bother of flute fingering in extreme keys, by which I suppose SIR, One of your correspondents, "M. L., "has com- him to mean the flat keys. But is it possible, in these puted by spherical trigonometry the distances between days of sliding heads, that anybody submits to the these three places, and is desirous of having his results bother of making the flat notes independently as they verified. He makes HG 4,135 miles, G J 6,824 come? Supposing your correspondent has to accommiles, HJ 5,831 miles [see page 332]. I was in-pany a piano, the music being in D flat, he should, by duced to try them at his request, and I make the results means of the slide, tune his D to the D flat of the somewhat near, but not exactly. This may possibly arise piano, and then play the notes as though they were from not taking the same latitudes and longitudes. written in the key of D, with two sharps, which is the The way I proceeded was this: I made the triangle natural scale of the flute, and causes no extra fingering

=

=

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
f 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 natu-
ral, 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 per-
plexed fingers.
T. S. G.
[13]

THE LUNAR CRATER-"ALPETRAGIUS D." SIR, Mr. Michell Whitley, of Penarth, Truro, a very careful observer of lunar objects, has addressed a letter to the editor of Scientific Opinion (see No. 85, June 15, 1870, p. 258), containing his observations on June 8, 1870, of the spot " Alpetragius d," (not the Greek Delta as printed, but the Roman d), in which he speaks of a minute blow hole in the centre of the white spot now occupying the place of Beer and Madler's crater. I am not aware of anything having been published on this spot since my article in the Student, referred to by Mr. Whitley; but at the close of 1868, and in the spring of

1869, I received communications on it from the wellknown observer Mr. Knott, of Cuckfield, and shall feel obliged if you will kindly give publicity to the follow

ing extract from his letters :

“December 24th, 1868," Mr. Knott says, "I hasten to report to you the result of an examination of Alpetragins 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 distinctly 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 Madler, 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.

SEWING MACHINES-REPLY TO "GROCER."

time heartily ashamed of the paper;" but unfortunately justice requires that I should take further notice of his indiscretion.

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 the reasoning, save only the Savilian Professor of As tronomy.

The gravamen of my charge rests, however, on his assertion that "Laplace, the elder and the younger Herschel, Humboldt, Admiral Smyth, Sir Willism Thomson, Mr. Tait, Dr. Balfour Stewart, Profess Tyndall, and other honoured names, all in their tam 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 opinies of such and such a person, be rightly described as "criticising that person with severity" then I am opa

to Professor Pritchard's charge; if not, then there is

truth in it.

SIR,-That a Thomas's shuttle will work best with the thread unwinding from the under side of reel is well known. The instruction books teach it. I have not 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 than when it is nearly empty, owing to the difference between the diameters. 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 thread presses strongly against the spring, and resists strongly the pulling off, but as the diameter of the thread diminishes, 80 But a type of my severity was wanted, and Professor the resistance of the spring diminishes, and thus compensates for the irregular Pritchard, with as much dexterity as though his trade action caused by the using, and diminishing the diawere hack-reviewing, conveniently makes one. There is meter of the reel of thread. It is, therefore, far superior one sentence, which, taken apart from the context, to a constant uniform pressure of the spring on the sounds severe. Whewell had spoken of Jupiter as a brass end of shuttle reel, which cannot compensate for I remark in "Other Worlds," that surely "no astrowatery globe with a few einders perhaps at its centre. the varying strain on the shuttle reel when nearly full or empty. "Practical Man" recommends a short nomer worthy the name" ean regard Jupiter as it was spring, as represented, to any one who would make a thus regarded "by one who, be it thankfully reshuttle for himself (but it is far more economical to buy membered, was not an astronomer." But then I go on to one), and further recommends the kind of reels to their indicate in what sense I use the word astronomer. "He," I say, "who has not gazed hour after hour on the glories respective shuttles, as illustrated at page 157. Grocer" is in favour of a Singer reel, because if was not an astronomer in the sense in which I wrote. For of the giant planet," &c. Every one knows that Whewell the reel is not pressed firmly down (in the Thomas's shuttle) the hinge goes behind the end of the shuttle the larger portion of his attention was directed to quite other matters than astronomy, and it is simply true, reel and shuts it out, instead of in." If "Grocer" found this to be the case two or three times with per that he was not, properly speaking, an astronomer. as he himself admits in his "Plurality of Worlds" sons he sold machines to, what would he expect to find Fortunately I have spoken with far too obvious appreif he applied the Singer reel to a long shuttle, or a No. 1 Thomas for shirt collar work, where the best stitching in this passage to admit of being misinterpreted ciation of Whewell's worderful abilities for my mean is required at the highest speed? The latter part of "Grocer's" remarks will be best replied to by the description and illustration of machines about to appear 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. [16]

A PRACTICAL MAN.

by others than Professor Pritchard.

Mr. Lockyer's views about the corona "simply because Professor Pritchard then goes on to say that I attack they do not square with mine." He knows perfectly He would not venture to assert that those reasons are well why I attack them; for I assign very definite reasons. insufficient, because, if he did, he would lose all title to be regarded as a mathematician.

Equally clever is his quotation of a passage having reference to the theory of the meteoric origin of solar VELOCIPEDE CONSTRUCTION. heat. I write "I am quite certain that there is no flaw in the evidence I have adduced from the laws of probaSIR,-Each maker-amateur or otherwise-seems to me to judge of his and other machines by the rate he bility; and that," &c. But it suits Professor Pritchard's can go on it. Now I think that is an erroneous test, purpose to make it appear that I am only expressing for I saw a machine, horrible in appearance, construcover confidently a mere opinion-so he quietly drops all reference to the evidence, and makes me say, "I tion, and principle, propelled at as great a rate as thirteen miles an hour (which for tricycles I believe to am quite certain that at least an important part of the sun's heat, &c." He immediately adds, "we may be the maximum rate), only the driver was a strong swarthy fellow, and exerted his ntmost. It is there fairly ask whence has Mr. Proctor this certain know fore not to be wondered at that "A Pattern Maker" ledge," &c. Yes; but if he had quoted the sentence in should think "the whole stock of velocipedes up to no- full, it would have become unpleasantly obvious that thing when put really to practical work, and partien-out whence Mr. Proctor derived his conviction. one had only to turn to "Other Worlds" to find larly 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. I grant that these machines can be made to go at that rate, and uphill, but it is practically "no go." I have practised the bicycle for a year in a hilly district (compared 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 de-negative evidence can be opposed effectively to the sirable for summer riding. But in my opinion, to four orbs." Does not this somewhat alter the aspect positive information he has left us respecting these rattle over the ground at the rate of one mile in four minutes on any but a first-class machine with even roads is sheer folly, and undoubtedly more so with a 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.

"How then can Mr.

It is well known that Mr. Lassell, the eminent and skilful astronomer who is the present President of the has only four satellites; for he can see but four with his Royal Astronomical Society, considers that Uranus Proctor," asks Prof. Pritchard, "venture to set his splendid reflector at Malta. 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 Sir Wm. Herschel have not indeed been yet identified; but one cannot read the account of his method

of procedure without feeling that no amount of mere

of matters ?

Then what am I to think of his quoting a printer's

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 Several individuals who have never "risked their 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 their numerous riders, and whether the strain on the readers. The little S. James (page 309) says on the actually happened; and somewhat spitefully adds

much.

abdominal rings is or is not so great as to cause ruptures, &c.

I am aware that a letter appeared about this some 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 commencement 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.

|

Another thing that I am sceptical about is the common
dogma that the driving wheel ought not to be more than
36in. or 38in. It is being continually brought forward in
the MECHANIC, yet to my knowledge has never been dis-
cussed, but seems to be quietly swallowed by brother

two and three wheeler is very correct; but I don't see
why the driving wheel should not be as large as the
enough to show cause why"
leg will admit of. If, however, any one will be kind
I should believe the
common dogma he will very much oblige. HUSBAND.
[17]

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 cir-
culation. 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

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 words-"They tried the spectra of glowing vapours. a few inches, on the same open paging, are these then goes on to speak of an alleged breaking of a dark they found bright lines of various colour." He glass" where I have spoken of no such event as having

and....

"these (two) misstatements are easily corrigible in a much else in the volume itself," from which we may 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.

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 Astronomicul 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 hun 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.

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 correspondents, may afford me the information I desire.

a

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 their middle point 0, 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 currents, analogous to the parallelogram of forces or of

velocities.

FIG.

B

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 enuncia

tion 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,

and let AB be the shortest distance between them.

Bisect

0

A

A B

A B in O, and draw O X, O Y,
parallel to Ax, By, making,
OX: OY: quantity of elec-
tricity passing along Az: 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
20R
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.

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
ficient, even when constructed, as I presume his is
(for his description is not at all clear) on the vertical
by 4in., gives a good dense spark at 14in. surrounded
My coil, with one cell, the platina about 2in.
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.

method.

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]

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 have got "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 acknowledges 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
could not see the Spanish Fleet-her failing, which
called forth the rebuke, was that she professed to see it
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,
£18 for English goods, and £11 to the State for duty;
so that the Englishman gets but £18 back against his
£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" may well ask "What sort of prosperity does
this indicate?" "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?

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 alhonesty of intention, yet as every one sees things though we must credit them with every possible 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 conceal from their vision the blueness of tint which is slowly but surely overspreading the aspect of affairs.

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 Elias Howe, jun., the late president, who made many kinds of clothing on it at the rate of 300 stitches a 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 the inventor, who had many of his machines, in 1841, making army clothing.

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 "Saul 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?

Last week there was a discussion in the House of

AIR PUMP-INDUCTION COIL. SIR,-I beg to thank the two correspondents who have answered my inquiries about the Air Pump; though, as I Commons on the subject of "Unemployed Labour," feared, they have not given me any information beyond which was very interesting, although unsatisfactory in what I already knew. The first one has simply given its result. We may, according to our several prea description of Tate's pump, a form well known; the judices, believe, with Mr. Torrens, that the country is other describes nothing more than an ordinary exhausting syringe, which, I have ascertained, is sufficient Goschen, that it is prosperous and happy; but above all in a state of destitution and misery, or with Mr. for the vacua required for the experiments mentioned differences of opinion, beyond all contradiction, looms by me in my letter, but utterly useless for higher vacua. I thought, among your numerous correspondents, there port its people. out the damning fact that the nation is unable to supmight 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.

brought with it a corresponding increase of work, and
There was a time when increase of population
portion to the increase.
the nation was stronger and more prosperous in pro-
All this is changed now, and
it is a suspicious circumstance that the change should
date from the period when, through the influence of
Free Trade, our imports have commenced to be much
in excess of our exports. Some of your correspondents
regard the necessity for emigration as a proof of our
prosperity. It is an unfortunate time for a nation when
the symptoms of weakness and disease are looked upon
as proofs of healthiness and strength-when the hectic
flush of consumption is mistaken for the rosiness of
health, and the nation disports itself in a fool's para-
dise, unconscious of the disease which is destroying its

What I want is a pump that will produce a vacuum end to about one-twentieth of an inch of mercury, and I know that the expensive class of pumps sold for this purpose and they are indeed expensive-are made with a single barrel. It was the construction of one of these that I wanted to elicit from some of our scientific friends. There is a plan of Grove's called a repulsion pump, that I have read about, which I believe is very good, but I do not know the particulars sufficient to work by.. I am now constructing one on my own plan, about which I am rather sanguine; still I shall be very thankful for any useful information on the subject. 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 the working of Free Trade, and ought now to be in a We have had five-and-twenty years' experience of 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 It is constructed on the vertical plan-so far

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

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
press as an established fact.
not be further circulated by being copied in the public

A close inspection of Elias Howe's first machine will show that he embodied all the essential movements. An eye-pointed needle passed the thread from a reel 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 main shaft, on the end of which may be seen the driving wheel, behind the fabric and above the machine. On the main shaft may also be observed the cam, having the same kind of action as that attached to the

SEWING MACHINE. 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.

[28]

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."

district.

"Boehm "

of June 10th, wherein you gave a sketch of the 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 Snow-
don. A capital way of doing this is to
I should like at the same time to remove the impres
ascend the Pass of Llanberis, and climb
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 hasi.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
pass and bridge of Aberglaslyn, and at
Capel Curig the falls of the Ogwen.
From Capel Curig to Bettws-y-coed,
and thence to Llanrwst. Here the tourist
may complete his tour by walking to Con-
way and Llandudno, thus completing the
circle, or he can extend his tour in the
same manner I did, by going on to Den-
bigh, St. Asaphs, Rhuddlan and Aber-
gele, calling, on the way between the two
latter towns, to inspect the beautiful
church at Bodellwydan.

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.

thence make

Several of your correspondents en-
quire the most economical way of doing
a trip; I 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
day excursions through the surrounding
If they wish to do it very cheaply, they
must cater for their own eatables, &c., &c., and
In the
take a good supply out on each excursion.
course of a month, I intend taking a walking tour
in the lake district of Cumberland and Westmore-
land, when I expect I shall adopt the former of the two
methods I recommend, with the addition of a good din-
ner 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

In his attempt to do this he makes an unfortun admission, as two extracts from his letter will show. B says, "I was induced to read Clinton's essay on his personally I know nothing of it." I tar flute. As to his other as his reading benefits him little. tion, I think he would have some difficulty in prodeung one instance of the Clinton flute having been "alasdoned" after it was once fairly adopted.

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 attributa 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 acknowledged 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.

JUSTITIA.

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 demor subject. stration, as he has thrown no new light upon th We live in a practical age and we are not up to ad infinitum.

[28]

ARTHUR GEARING.

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

Now PN QM.. PQ NM = LC

And LC BC-BL-arc PL = arc PK-arc AQ .. arc AQ LC3TC 3 nm = 3 p q = 3 arc Aq By which means any arc of a circle may be divided R. T. B. R. into any number of parts. 24]

our Own

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 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.

beauties of other countries than their own, or rather,
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, Blair-
The drives around
gowrie, Pitlochrie, and Dunkeld.
Crieff are very lovely; and those who are advocates or
lovers of the water-cure, will find a fine hydropathic
At Dunkeld,
establishment convenient and healthy.
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, via Blair-
gowrie and Spittal of Glenshee, passing through the

running down a crooked brook; is that turning about
to keep them from falling? If so, and you are in a nar-
row road, meeting a carriage or wagon, is there a
danger of running into the carriage? or falling when
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. for-
ward 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 rid-
ing 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.

beautiful scenery of Craighall, a few miles above Blair
gowrie; but I would recommend those who wish to see
SIR,-The following mode of approximately rectify
Craighall in all its grandeur to put up in Blairgowrie
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
At Braemar,
Craighall is decidedly finer than either.
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.
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."