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number of teeth. You will observe on the gauge, that to the right of the zero line, is a space containing two of the divisions, that there are to the left of the zero, and that quantity is the "addendum," or quantity that the outside of the wheel is bigger than the pitch diameter. So to find diameter of a wheel of 20 on the top scale of all, put one point of your compasses at 20, and measure towards the left as far as the zero, and that will be correct. Or for 25 teeth, measure from 20 past the zero to the number 5, including altogether 27 divisions, and that will be right. And the same for any other scale. It is to be remembered, in making the guage, that the 5 gauge is 5 parts to an inch, and the 10 gauge is 10 to an inch. A piece of the gauge 7in. wide and 6in. high, will be quite enough to show the principle. I must request care in using, as it is the original and only one I have.

SHORTHAND.

J. K. P.

practice of about one hour a-day for six months, and having kept the dictation for more than two years was able to read it with very little difficulty, although the subject ("Locke on the Ideas ") could not enableme to guess at any of it. Forty years of experience have been required to bring this system to its present state of perfection. No disadvantages can attend the knowledge of such a useful accomplishment as shorthand; the many advantages are obvious.

Mr. Pitman's office is at No. 20, Paternoster-row, E.C. Mr. Lewis's is at No. 113, Strand, W.C., where Mr. Lewis will give all information at almost any time. The former gentleman has published a small inexpensive book on his system, and the latter a halfguinea book on his system, which is used in both Houses of Parliament and in the Courts of Law. The Prayer Book and the New Testament may also be had in Lewis's system. I think you will agree with me that only those who can speak from experience ought to express an opinion on the relative values of various systems, no one profits by being told that some one has heard that one particular system is the best.

merits of

FKANK W. GRIERSON.

its

I think " Hermit" could write freely from dictation half that time, he could keep his diary and note-book, in six months, by an hour's practice a day; and that in to his great contentment.

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I would recommend "The Hermit " to write for the Paternoster-row; "Stenography," by Thompson, Phonographic Teacher," 6d., to Mr. Fredk. Pitman, 18., to Mr. Fredk. Warne and Co., Bedford-street, Covent Garden; Groomridge and Son, 5, Paternoster-row.-Compare "Taylor Improved," 8d., to them together, and make himself master of both alphabets and joining tables of these systems. When he comes to the end of that stage, I can tell him

SIR,-Having learnt three systems of shorthand, viz., Mackenzie's, Pittman's. and Lewis', at times sufficiently far apart not to mix one system with another, I have to state in answer to "Hermit" (who, by the, SIR,-Your "Hermit," on way, puts his question in the unusual form of a letter) for any information which I can give him, on the page 255, wishes on age 255, that, in my opinion, Mackenzie's is not worthy the name of shorthand, Pitman's one of the shorthand, and of "different" worst, and the Royal Lewisian system by far the best, systems. Five-and-forty years ago I took up Sam beating all others hollow; the first two, I am thankful Taylor's system, which was published A.D. 1786. I to say, have long departed from my memory. I have follow, for Wm. Harding's came out in 1832 with had also Wm. Mavor's, of 1789. This latter I did not often written 110 words a minute in Lewis's system, Taylor's Improved," which I followed, with some and a friend of mine has written more; the most rapid modifications, ever since, examining every novelty as reporters are said to be able to write 250 words a minute in it, but I much doubt any one's ability to do it came out, and comparing its merits with my old so in such a short time. A gentleman who has used adoption-improving it if I could. Pitman's system for many years acknowledged, after Pitman's system is the only one I can call a rival of trial with me, that the system I write (Lewis's) is the Taylor's, and that only because of its many admirers. I clearer and shorter of the two. As Mackenzie's system learned it, tried it for some time, but abandoned it as is now never heard of, there is no occasion to say any-complex and unsatisfacty. It has but ten characters thing about it. The great fault in Pitman's consists for twenty letters, to be distinguished from one another by their "thinness " in using the same characters when made thick and thin Taylor's are all unlike, except where you can write one or their "thickness." to represent different letters; I have heard many writers letter for another, as for instance, S for C soft; G of Pitman's system acknowledge, and have myself discovered that it is impossible to make any real dif- for J, or rice versa. ference in the thickness of the characters when attempting to write rapidly; the consequence is that unless the shorthand be transcribed while the subject is fresh in the memory it is practically illegible; but the most ridiculous feature in Pitman's is that there are (as nearly as I can remember) six different posi-20, tions for the vowels and dipthongs, so that when the writer finds it necessary to insert the vowels, as in a proper name, or foreign word, for instance, he has to consider while he is rapidly writing, first, what is the proper sign for his particular vowel, and then its proper position-whether it should be at the upper end on the left hand side of the character representing the nearest consonant to the vowel, or at the middle below the character, or at the upper end above the character, or at the lower end on the right hand side of the character, &c., &c., according to the position of the character on the paper; such consideration is almost impossible; rapid writers in Pitman's system are obliged to alter and improve it in this particular. remember I made out a kind of table to try to remember the different positions. Anything written in Lewis's system can be read, without any difficulty, 20 or 30 years hence, when the subject will have quite escaped the memory-the characters representing the vowels are very simple, and their position is not of the slightest consequence, so long as they are written in the same order, as in longhaud; the only awkward character to join to others in this system is that representing ch; but another character can easily be substituted. Should "Hermit" wish to constantly write the same sentences-as, for instance, "Your last letter duly received," he can add a character representing the whole of such sentence without causing any confusion; any word may be written as spelled, or as sounded-that is, phonetically; any number of figures also are expressed in this system without taking the pen off the paper; quite as much time is occupied in making a dot, even, as in writing three or four words in shorthand, because tnere is no necessity after a little practice to lift the pen from the paper at the end of each word. I was able to write 60 words a-minute after a

more.

MAC D.

SPECULUM TESTING-THE "PHANTOM."CALLAND'S BATTERY. SIR,-Thinking it would interest many of our astroInomical friends, and having a little forced leisure upon my hands through being invalided by a serious accident, I have endeavoured to epitomise, or, rather, to give in my own language, the substance of methods employed by Mon. Foucault and others for figuring and testing specula independently of stellar observations. These plans were described by Dr. Draper, though not with all the details given below, in a book published in 1864, entitled "On the Construction of a Silvered Glass Telescope, 154in. Diameter."

apartment, the apertures of which can be closed in For a testing room he chose a long underground order to be as free as possible from vibration and the disturbing effects due to variations of temperature. For a support a piece of wood somewhat thicker than the mirror, and curved out to fit its periphery, is nailed to the wall about 3ft. from the ground; this is then lined with several thicknesses of blankes, so as to form a pad for the bottom part of the speculum to rest upon, the latter being prevented from falling forward by means of two wooden buttons near the top, which secure it, but so as not to bind it in any way.

Exactly opposite the speculum, and in its centre of

curvature, is placed a lamp giving a very strong ligh the ordinary glass chimney is removed, and one of or tin substituted, having opposite the very bright part of the flame two holes drilled about the halfe an inch or more asunder, the one being about 1-50th and the other 1-300th of an inch, or less, in diameter. The smallest hole is the one used in testing, the other merely acting as a finder; these holes must be drilled in the same level, so that when the image of the larger one is obtained, by turning the chimney round a little, the smallest will come in view. Close beside the lamp is placed an eyepiece, magnifying about 39 times. through which the enlarged image of the hole is conveyed to the eye.

If now the speculum be of a perfectly spherical figure, the image of this hole will appear round and distinct, encompassed by diffraction rings. But if its surface be at all irregular the image will be found distorted, or having wings, or it will present some other equally anomalous appearance. The aperture of the speculum can now be stopped off in zones about an inch broad, when, should the form be regular, no alteration of the eye-piece will be necessary to preserve each separate zone in focus.

In judging of a parabolic figure, the longitudinal ceeding from its centre of curvature must be calculated, aberration of such a figure when reflecting rays proand the form (or curvature) of the various zones altered by means of local polishers (small polishers varying from 1 to 8 deg. in diameter, made and worked the necessary aberration is obtained. A second test in the usual manner either by hand or machine), until used in conjunction with this one completes the operation of testing. In this test for the eyepiece is substituted an opaque screen, behind which the eye is placed, and the edge of the screen so moved as to shut off nearly all the rays proceeding from the mirror to form the focal image of the small lamp hole; and just when the last rays are departing, an intensely exaggerated view of the figure of the mirror, with all its imperfection in relief of light and shade, will be premirror will present to the eye the appearance of an sented to the eye. But if perfectly spherical the equally lighted plane.

So exceedingly severe is this test that the smallest ruffles or undulations due to the irregularities of hand testing or the most powerful microscope, are made polishing, but which cannot be detected even by star plainly visible.

If the speculum possesses a parabolic or hyperbolie the apparent plane will appear as a zone having its figure, an undulation or gradual rise in the surface of greatest elevation midway between the centre and

are carefully followed they will be found to affords valuable criterion to judge of the quality of a mirror. of known goodness to be able to figure with greas But it requires some amount of practice upon specula accuracy by it. In the last-named test it is very important to place the screen and the lamp both precisely in the focus of the mirror. This will easily be found by moving them a little to and fro until the shadow named below appears to advance all over the face of the mirror equally.

circumferenceof the mirror. If the above directions

mirror presents is that, when the eye is brought into "The appearance that a trely spherical concare such a position that it receives the whole pencil of reflected rays, and the opaque screen is gradually drawn across in front of the pupil, the brightness of the surface slowly diminishes, until just as the screen is cutting off the last relic of the cone of rays, the mirror presents a uniform greyish tint, followed by total darkness, and gives to the eye the sensation of a plane."

I will, if desired, describe Dr. Draper's and Mons. spoken very highly of, but will be found rather Foucault's system of grinding and parbolising. It is troublesome. It certainly gives good results on a large glass. It is superior to the method published by the Rev. H. C. Key, and lately so ably detailed by Mr. Purkiss. own plan much quicker, and capable of producing I do not practise it my self, as I consider my better figure, especially on a small glass. I shall probably recur to this interesting subject in future letters.

Next week I hope to have something to say in fa vour of the "Phantom" veloce, one of which I have just obtained, but owing to the accident named above

kave as yet been prevented from taking a "spin " upon it. A better or more thorough-going piece of workmanship throughout I never beheld. 1 like the appearance of the wheel and the way" the tires are affixed. It certainly looks capable of doing all that is reported of it. All my friends who have tried it speak highly in its praise.

EDMUND M. T. TYDEMAN, 10, High-st., Brighton, P.S.-Would "Sigma" oblige me with a description of "Calland's " battery, which I see is stated to involve only one-fourth the expense of a "Daniell's?"

FEED-WATER HEATER.

SIR,-I have read your correspondent's letter, signed "James Baskerville," and beg to thank him for the correction. I wrote my letter to you rather hurriedly. I should have said "within 10° of the heat of the steam issuing from the exhaust." This difference I ascertained by placing a thermometer in the exhaust pipe and in the heated feed water. Passing by the touch of sarcasm in one portion of his letter as a weapon unworthy of a place in a correspondent's armoury; I do not claim an extraordinary saving in the use of this arrangement, as your correspondent seems to suggest; but I do say that my experience warrants my expression when I say that this heater is a very effective appliance. Against your correspondent's figures I beg to place the fact that for two and a-half years before I erected the beater described, my consumption of rough slack was a boat-load every seven weeks on an average, and for over 20 months after the heater was in operation, the same boat-load served always over nine weeks. During both periods, the work performed by the engine and its general condition were the same. The arrangement sketched by your correspondent is no doubt equally effective as that described by myself; but I think the nuisance caused by the noise of condensation of the steam would be a disadvantage, as also the passing of hot water through the pumps.

LLAH.

COMMERCE AND TRADE-HIGH MARKETS
WAGES-STRIKES, &c., &c.

I

SIR,-Having read the very instructive letters of Sigma' and others on Commerce and Trade,' I would like to see the subject sifted from the very bottom. have been a subscriber from the first, and I think the above subject is as important as any. Not many weeks ago the Glasgow joiners were out on strike for the nine hours a day movement, and they have gained, Now, in all future contracts the prices will be higher then, of course, house proprietors must raise their rents. Now, all other trades, seeing the success of the joiners, will in time try to follow. Now. I would like to have the opinion of some of my fellow-subscribers if 8, or even 9 hours a day, would pay, were it to become the general law?

I have been thinking about the Land question (but not Irish land). My opinion is, if Government were to buy up the whole of the Three Kingdoms, and sublet it in portions to the highest bidders,' then the money would return to the national purse, it would reduce taxation, and strike at the root of all discon

tent.

WILLIAM JARDINE, Risk-street, Dumbarton.

READINGS FROM THE GLOBES.-No. IV. (Continued from page 278)

at

SIR,-It must have occurred to every one, when viewing the sun, what a different appearance he presents at different seasons of the year, sometimes reaching a considerable altitude in the heavens, and other times being low, and making but a small tour in his daily course. Even an uneducated person cannot but be struck with this property of the sun; but travellers who have visited the torrid and frigid zones must have beheld with still more curious feelings the appearanees which he presents in these parts-in the former becoming vertical, and in the latter never setting for days, and even months together. the heavens noticed that he did not rise daily in the Early observers of same point of the compass, but that half of the year he rose more and more northward, and became higher and higher until he had reached his maximum height, and then began to recede, and for another six months of the year to rise more and more southward, and become still lower and lower, and by logical deductions they have been able to form an intelligible theory of the sky, so that anyone can, without much effort, understand

"Quid tantum Oceano properent se tingere Soles Hiberni, vel quæ tardis mora noctibus obstet." "Why winter's suns to ocean haste away,

Or what obstructs the nights to make them stay." It will be our object to show how these different appearances may be readily explained by the globe, and we will begin from the point Aries, when the sun makes a fresh start to pursue his accustomed round. When at this point he is crossing the equinoctial line, and the days and nights are then equal, or 12 hours long, in all latitudes as far as the poles. To represent this by the globes we must place its two poles in the horizon, as It appears in Fig. 1. It will then appear by an inspection of the figure how it is that the days and nights are then equal all over the world; for, let S. E. represent the equator, N. P. the north pole, and S. P. the south pole, round which the world 'spins. The meridian lines are imaginary lines, contrived by geographers for the purpose of giving a better idea of the revolution of the earth on its axis. In this situation, then, if we count from 8 towards either pole, we shall find six spaces, each 16° in width, which is equal to half the length of the day in all latitudes. The days will therefore be 12 hours long, and the nights 12 hours long. As the sun is supposed to be in the point Aries, he will be vertical successively to all living at the equator, as they pass under S. At the north and

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require these two amounts to make 90°. Thus, at
London his meridian altitude will then be 3810, at St.
Petersburg 30°, at New Orleans 60°, and at Quito 900
Again, owing to the pole of the earth always pointing
to the pole in the sky, it does, as it were, shift itself;
and moving gradually in three months after, or June
20, the earth presents the same appearance as in Fig.
2. Then it will be summer in the northern hemi-
sphere, and the days will continually increase in length
towards the north pole, and consequently the nights
diminish. If we count from S towards H, which is
supposed to represent the horizon, or boundary of
light and darkness, we shall find that at the equator.
as before, the day is 12 hours long; but in proportion
as any place is distant from that line, so its days
increase in length until we come to 2340 of the north
pole, or to the boundary of the Frigid Zone. Here we
shall find, by counting the meridians, that the half day
is 12 hours- that is, that the length of the entire day
is 24 hours, as, for instance, in the northern part of
Sweden. His meridian altitude will there be 47°,
because 231, the declination of the sun, added to 231
the complement of the latitude, will make that
amount. He will then have reached the point where
he begins to recede, and at noonday will be vertical to
those who dwell under the Tropic of Cancer, and will
continue to be so for several days; for it is here that
"Sol stat," or is apparently stationary for a short
time. By reversing the figure, it will present the
appearance of the earth at the winter solstice, when
the south pole is turned towards the sun, and the
north pole away from it; and the consequence is, that
the days continually increase in length in the
southern hemisphere, the sun becoming daily
higher and higher in the one, and lower and lower in
declination, when his altitude at London will be the
the other, until he has reached his greatest south
complement of the latitude minus the declination, or
= 15o. Thus we find that, having only a
384-234
small are to pass through in the enlightened hemi-
sphere, his long delay in rising is accounted for by his
having a longer tour to take; and when he makes his
appearance, it will be as much to the south of the east
as during the summer it was to the north of the east.
He will then be vertical at noonday to those living
under the Tropic of Capricorn, and the reason will be
apparent why our antæci have summer when we have
winter, and why their day is exactly equal to our
night. If, then, we wish to see the position of the
earth with regard to the sun at the summer solstice,
we must elevate the north pole 23 above the wooden
horizon. But to show its position at the winter sol-
stice, the south pole must be elevated the same number
of degrees, when, by turning the globe on its axis, it
will be seen that the north pole has entirely lost sight
of our golden luminary.

T. S. H.

J. F.

DARK LINES IN SOLAR SPECTRUM.
TWILIGHT.

sected angles would be a curve of the third order, and not a circle. Moreover the method would be rather troublesome in practice.

It led me to investigate the curve which has the property of trisecting all angles drawn from two given points in the manner of the method referred to, and which is, in fact, the place of the apex of all triangles standing on a given base, and having one of the angles at the base three times the other.

The equation to the curve when referred to rectangular co-ordinates is cubic, and has not an encouraging aspect.

Its polar equation is simpler

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SIR,-I have read, noticed, and examined, with much interest, the thousand-and-one proposals, suggestions, and drawings, made in your paper, respecting the best and easiest mode of self propulsion. Your correspondents' various machines, seem, accordTHE LATHE AND ITS USES. ing to their own acconnt, to go at all speeds, vary. ing from 6 to 30 miles an hour. All the proposed SIR,- quite agree with another subscriber of machines would no doubt fulfil the expectations of "ours," of this week, respecting patterns for lathe, their inventors, if a journey of 50 miles each way was and have no doubt that, notwithstanding all that has all down hill, both there and back, but, unfortunately, been published, good working drawings to scale, of in a journey both ways, there is just as much up hill the most recent pattern, and containing all the as down hill to go. I have never yet been on one improvements that an amateur would be likely to of these manumotive engines, but I have seen many want in a lathe, would be highly prized. It is not of them in the street and on the highways; they all parts shown in section, &c., and some guide as to rela-road, it appears to me to be fatiguing work, and I enough to see a finished engraving, without the various go first-rate down hill, but up hill, or even on a level tive sizes. There is no journal that can do this better have come to the conclusion that the whole stock of than "ours," even if so well. We don't want to lay velocipedes, pedespedes, tricycles, bicycles, and all out 100 guineas, nor is there any need of one costing a large sum. other pedes and cycles, are up to nothing, when put I would suggest it should have fret saw really to practical work, and particularly in a hilly and vertical drilling apparatus to fit, and work on it, district. It is useless, then, wasting so much of your as well as many other appliances that brother ama- valuable space every week in describing these articles. teurs could give "notions" of. The long and short of it is, we want, and must have, something really useful, practical, and powerful. A steam carriage is what we want, but at present steam carriages are practically useless in consequence of the very many vexatious restrictions placed upon their use by a house full of M.P.'s interested in railways. It is our duty as English mechanics, to agitate for the repeal of these restrictions, and for the abolition of all toll bars, and never rest satisfied until we have accomplished our object. When such eminent men as Sir Joseph Whitworth are in favour of road locomotion, I think the matter is at least worthy of discussion in your pages. My object in troubling you, is to induce some of your clever contributors to take up the matter in earnest. I think, as mechanics, we ought to take a deep interest in anything that will increase and benefit the iron trade. I am sure I would make every effort to own a steam carriage, were their free use permitted, and I look forward with pleasure to the time when I shall be able to take out my steam carriage, and give my wife and children a pleasant ride into the country, when my day's labour is o'er, or when I can reside a few miles from town, and go to my work in my own carriage. This proposal may seem ridiculous on paper, but we have it within our grasp if we will only go heart and soul into the matter. Then, again, look at the immense benefit it TO TRISECT AN ANGLE. would confer on tradesmen of all classes, builders for SIR,-In your impression of the week before last instance, who may have twenty men working at a job, there was an ingenious attempt at the solution of the three or four miles from their shop. These twenty men well-known problem to trisect an angle. The method, each lose one hour of their master's time every mornhowever, was only approximate as the locus of the tri-ing morning going to the job. Now with a steam

SIR, I wish "Steersman (3991) had not required my opinion upon the spectra of the fixed stars, as I would much prefer allowing the spectroscopist to correct his own errors.

There is no doubt the spectra of comets and nebulæ reveal the character of these objects; but as to remote suns, diminished by distance to a point, what can be expected from the spectroscope but evidence of the power their light still possesses of effecting chemical change in our atmosphere?

With reference to the presence of iron in the air, where does "Steersman," imagine the surface matter of the globe comes from? Space is not an empty void. T. A.

P.S.-I hope Mr. Proctor will pardon my obtuseness in nature as a crepuscular curre; for refraction is not but I cannot understand him. There is no such thing concerned in the phenomenon of twilight.

carriage, they would go in fifteen minutes, which would be a clear saving of fifteen hours per day to the master. Certainly the coal and the driver's time would cost something, but that would be amply compensated for by the men being fresh and ready for work, instead of being fatigued by a four miles journey. Then, again, very few small tradesmen can afford to keep horses, because they are always eating, whether they are working or not; now a steam carriage would only be consuming when it was working, the consequence would be, every one who could spare the money, would have his own private carriage; this would give a great impetus to the engine trade, and find employment for thousands of our intelligent mechanics, who are being driven out of their native land to seek that employment which is devied them at home. Any objections that our M.P.'s could make or raise, could easily be met, and the public safety secured by using proper precautions, such as limiting the speed of the engine to, say eight miles an hour in towns, and fifteen miles an hour in the country, and by compelling the owner of each carriage to place a speed indicator, and also a water and steam indicator to his boiler, in such positions. that they could be seen distinctly by both himself and the general public outside, who could complain if he violated the law, so as to endanger the public safety. Then again, each carriage should carry a pair of lamps. Coke should be the fuel to be used, so that no black smoke would be emitted; in fact, only let the want of a compact and useful article be felt, and the inventor will step in and supply the want. It would scarcely be advisable to allow lads under, say 18 years of age, to be in charge of them. In conclusion, let me urge your readers to consider the importance of this proposal, and never rest satisfied until we have gained our object. Mr. Allen and his 33,000 brethren of the Amalgamated Engineers, will, I am sure, come to the rescue. The question only wants agitating, and I know of no paper so suitable as the ENGLISH MECHANIC SO take the lead in the matter. What a boon it would confer upon commercial travellers with their tons of luggage, to be able to go through the country districts, where there are no railways! It would be to them an immense saving. May I ask you, Mr. Editor, to append the present Act of Parliament on the Use of Steam Carriages, for the benefit of your numerous readers?

A PATTERN MAKER.

["A Pattern Maker" makes some suggestions on steam carriages well worthy of attention, but why condemn the whole stock of velocipedes," if he has

"never been on one of them." He wants a steam carriage "to give his children a pleasant ride into the country," but every one has not a wife and children to take. Possibly at one time there was too much of our space occupied by notions and fads in connection with velocipedes; but for some time past we have only given insertion to practical suggestions and realised facts, and certainly "A Pattern Maker" cannot reasonably object to space being so occupied. -ED. E. M.]

A FOUR-WHEELED VELOCE. SIR, I see that you give in your publication considerable attention to velocipede construction. It is an interest subject, and deserving of the space you devote to it. The bicycle seems at present perfected in the Phantom "veloce, and for all who can ride on a two-wheeled machine there seems to be nothing more to be desired. But there is a large class of people, both young and advanced in years, especially the latter, desirous to make use of this kind of locomotion who cannot or will not adventure them.selves on two wheels. I have been thinking that for them there might be a safe and easy-going machine constructed which would be light and swift, too, if two bicycles could be mechanically connected so as to make one machine with four wheels, on which two persons could ride abreast. This would be a safe and social way of riding the veloce for the class of people referred to, if our mechanics should pronounce it practicable. The tricycle does not answer the purpose, and is therefore but little patronised. It is possible that you have received suggestions of this kind already, and that they have been satisfactorily disposed of; if so, you will please excuse this communication as in reference to your useful publication I am but

A NEW READER.

then, that the medium betwixt these two extremes is nisation of a superior character could be carried out the condition that will be most effective in rendering with very successful results. What is to prevent us at a time when this great question of emigration is good work." It may not be amiss, although the forcing itself upon every thoughtful mind, to set to thing is self-evident, to say that long twisted fibres work and form the nucleus of a new and prosperous offer the greatest resistance in drawing, and short colony, to be established in some favoured spot of our straight ones the least. Another very important conglorious dependencies, which may, in the course of sideration in this matter is the speed at which the fibres are drawn out; for it must be remembered that the years, become the happy home of thousands of our surplus population? I can see no reason why this rollers do not give to the fi'aments a gradually increas scheme could not be easily carried out by the aid of ing rate of motion from one speed of travelling to your liberal pages, and of the able and willing minds another, but draw them out by a sudden jerk, so that which so freely contribute to their contents. Not the strain upon the fibres caused by a long draught, only so. I believe that a colony formed with such may be considered as equal to that of a short draaght materials as would thus be collected, would be initiat a correspondingly quick speed. (Let me here refer ated with the advantages of a greater diversity of the lads to the Rev. E. Kernan's "Science for the means, talent, and a more general diffusion of useful Young," in this vol,, Inertia, page 105). Before I reintelligence than in almost any previous instance of sume the subject, let me remark that this latter comthe kind, thus making a start with all the valuable mon sense fact plainly demonstrates that no very quick elements of civilisation at the very outset. I believe speed of rollers can ever be attained with long draughts, now that the attention of Government has been though it is not the speed itself that is mischievous, but urgently drawn to the subject, terms of a most the abruptness with which the fibres are jerked from advantageous character could be made in the way of one degree of motion to another. There are but few a grant of land, and other important concessions. spinners of any experience who do not know that a If you think, Mr. Editor, that my views are correct very triding increase of speed often makes the "work" on these points, and you think proper to submit them unmanageable. Many things may contribute to this to your readers, with the view of carrying them into result, but the chief one is the too abrupt jerking of practice, I will be glad to correspond with any gentle- the films between the rollers; and a shorter draught man competent and willing to become members of a put in operation with the increased speed would be a provisional directorate in such a movement, with the remedy for the main evil. Now, the cylinder" of a view of an interchange of opinion on the subject, carding engine travels at a much quicker rate than the after which a permanent directory could be esta doffer" that "strips" it of the carded filaments; blished, in at least one principal seaport in England consequently, the filaments cannot be laid upon the and another in Scotland, and another in Ireland; surface of the "doffer" longitudinally and parallel, and after certain essential arrangements have been but in a confused mass. In this state they are combed from the "doffer" by the "doffing comb," and trade made, measures would be taken to make the movement public through the pages of the ENGLISH to pass in a continuous web through a funnel-shaped MECHANIC and other media, with the view of receiv nozzle; and by this means are contracted from the ing applications for membership, which I trust would broad web to the form of a flimsy rope. This flimsy reach 1000 at least in a short time. Such a number rope of fibres has to be drawn out by being passed of colonists, with its combined capital, could, by through various speeds of rollers until its tenuity chartering vessels on its own account, transport equals the intended "counts." (The "counts" are itself to the required destination at a very moderate the number of hanks there are in a pound weight of cost, and by the employment of its supposed superior the material-810 yards = 1 hauk). The "drawing intelligence in the selection of machinery and other box" rollers have, of necessity, the greatest speed appliances, agricultural or otherwise, of the most given to them, then, after taking into consideration approved description, it would no doubt succeed in the above facts, and remembering, moreover, that beestablishing itself with as small a share of discomfort tween the first pair of rollers there are often upwards as is possible under similar circumstances. of 40,000,000 of fibres passing through at once, is it at all surprising that the question asked by "Factory Lad" should receive so many different answers. However, "Factory Lad," page 231, says, "I find Mutual tically found to be the best arrangement working fair Improvement' comes the nearest to what I have pracDhollera -I have my draughts

ALEXANDRA.

[The above letter is written by a strong-handed and clear-headed; Seotchman. I may contain the germ of an historical movement; at all events, it has our hearty approval.-ED. E. M.]

COTTON SPINNING.

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SIR, I promised in my last letter to speak further on the subject of drawing boxes; with your permission I will now do so. But first let me say a word or two about the filaments that drawing rollers have to disentangle and draw out. Peradventure, there may be some lads, and even big 'uns" too, who are not fully aware of the fact that cotton fibres are long tubes, more or less tortuous, and individually of no appreciable strength. That they somewhat resemble the hair of animals, and grow upon the surface of the cotton seeds much in the same manner as hair grows upon the head. Different classes of cotton have different, and to the spiner, very important characteristics as the average dialeter of the fibres of upland" cotton = part of an inch, of Sea-Island

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6000

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500

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2000

of Surat, from to- The process through which the cotton goes after it is "picked " from the seed pods, and previous to its being compressed and packed up for exportation, is a mechanical scutching, for the purpose of tearing off the fibres from the surface of the seed-coat to which they obstinately adhere; and for the further purpose of expelling other extraneous matter from the cotton. How far this process has hitherto been successful, those can tell, to their cost, who have paid from two shillings to two shillings and sixpence per pound for sand, seeds, dust, stones, bricks, &c. However, anyone at all acquainted with cotton spinning knows how utterly impossible it is to tear off the fibres from some portions of the seeds by any amount of scutching, short of one that will be disastrous to their spinning qualities after the cotton has been compressed and felted together, and, AN ENGLISH MECHANIC COLONY. especially, is this so with the chief classes from India ? When portions of the most common descriptions of SIR, I beg to add my testimony to the very able cotton come to be examined after being "willowed," manner in which our MECHANIC is conducted, and the "scutched," and "carded," they will be found to congreat success it has attained. This is the result of sist, not of a mass of single fibres commingled your wise policy of encouraging all your readers to together, but in the mass will be found numberless become also contributors. "In the multitude of minute "motes," with a small cluster of fibres councillors there is wisdom." Curiously enough, I adhering to them. The object of the carding process have known instances, long before the advent of is to climinate the filaments individually by a comyour journal, of similar periodicals starting off with bining action, but so tenaciously do these minute great eclat and success, mainly owing to the primary clusters adhere together that even the "teeth" of the encourageinent of this same feature, but somehow, cards will not separate them without such an arrangeas soon as the precocious gentleman thought himself ment of them as would break the rest of the fibres to safely out of his leading strings, the communications pieces. Here let me observe that these minute motes and queries of the life-giving amateurs were pushed affect the drawing qualities of the cotton very from corner to corner, and ultimately to the cover of materially; no cotton in which they exist will draw his precious pages, the effect of which, upon their out equally or evenly, but in small patches or clusters intrinsic value and on the subscription list, it is which ultimately produce a knotty, uneven thread; beneedless to describe. It is clear, a journal like yours cause, behind each knot or cluster of fibres there must may be made useful in a thousand ways to its sub obviously be a corresponding "thin place," which scribers, which must soon become legion, whatever gives to the yarn the appearance of having been may be their individual position in society. We can partially cut through. The strength of these thin easily gather from its pages, that it represents to a points, be it observed, is the strength of the yarn. I large extent, every grade of education and intelli- must further remark that the length of the fibres and gence, from the inspired philosopher to the humblest the degree of their natural torsion also affect their mechanic or agriculturist, all ready to yield up the drawing qualities, inasmuch as they affect, to a great benefit of their special experience to their fellow sub-extent, the amount of force with which they resist the scribers. Under these circumstances, it is difficult to quickened motion of the front pair of rollers, or, in conceive almost any object, however important, or other words, inasmuch as they affect the amount of however comprehensive in its character, in connection force with which the latter or hind portion of the with which your journal could not be of most vital fibres resist the quickened speed of the frout portion. service. Now it is obvious enough that the amount of this resisHaving noticed some anxious inquiries, from time tauce or holding-back force must also depend upon the to time, on the part or individuals desirous of emi-distance there is betwixt the rollers. If this resistance grating, it has struck me forcibly, that through the be too great, the fibres will be broken; If too little, they agency of your trustworthy journal, a scheme of colo- will draw out in clouds, or irregularly. It follows

341 × 175 x 1·17 = 7·06." Now, if" Factory Lad" is not "running" at a great speed, nis arrangement may do.

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(But 3:41 x 175 x 1·17 = 6·981975, not 7:06.) However, it is incomprehensible to me how "Factory Lad's" Surat fibres after being "coaxed" (vide "H, C. S.," page 183) from 1 to 2, should be thereby prepared for being jerked from 2 to 7. "Mutual Improvement," page 230, says he must give me "credit for knowing better than equalising the three draughts." I am afraid I do not deserve the credit; for, seriously, I do believe the arrangement he advises, in these days of "keen" competition, with its concomitant, quick speed of productions, would be all the better for some amount of equalisation. If, however, he thinks differently, I shall not quarrel with him. In a former letter, I said it is a "pennywise and pound foolish" thing to have a draw-box attached to the carding engine for the purpose of adding a considerable amount to the draught of he engine. "Mutual Improvement says heet understand why such is the fact. He further it is stated that some of our most successful spinaers work them, and asks if I will give my reasons for condemning them. To be sure I will, M. I.," lad; at the same time, let me say, I do not want any deference to be given to my opinions, but I would rather that we should all bear in mind the fact, that we may all look at any subject from a different point of view; so that there is not the least necessity for us to "pitch into each other." However. simultaneous with the process of drawing, it is found to be necessary and profitable to put in operation the "doubling process, in order that the inequalities of the "work" may counteract each other. And, furthermore, in order that as the filaments are drawn out longitudinally and laid parallel to each other, their ends may be properly arranged, one a little advance of the other; in the same order as a builder lays the courses of his bricks, that the joints may be well overlapped. Without this condition, it is impossible to make a good thread; and so fully is this fact recog nised that the doubling process is carried out by some manufacturers to the extent of from 80 to 100,000 times. It is a self-evident fact, that as the draught multiplies the length of the yarn or sliver, it also multiplies its defects, unless it is prevented from so doing by doubling. Short draughts and plenty of doubling will produce good, even yarn, that will bear the strain of quick speed-sour bulwark against competition. "M. I." may now see why I con demn drawboxes attached to carding engines for the purpose of adding a considerable amount to their draught I am somewhat puzzled in my attempts to find out by what

preparation "Harmonious Cotton Spinner" has resolved the major chord of his 1st letter into the minor chord of his 3rd. How does he make his 3rd harmonise with the tenor of the ENGLISH MECHANIC? To give advice is an easy matter, generally speaking, and most people have lots of it to spare-but to give information is a different thing!

E. SLATER, Burnley.

ORGAN PIPES-CLOCK BELL. SIR,-Having been benefited by the communications of others, I feel bound to give any useful result which I seem myself to have attained. I have taken "Adept's" plan of open wood pipe with the bevelled mouth-piece turned to the inside. But instead of the short sharp bevel I have made a lengthened easy slope, extending about two-thirds up the pipe. have also bevelled the back to correspond, reducing

the wood where it meets the block to the thinness of pasteboard. The space thus gained in the interior I have economised on the outside, making the pipes of less depth, the smaller pipes by one-eighth to threesixteenths of an inch, and in the middle of the organ by as much as a quarter inch. I find the pipes so treated speak readily, with a clear and pure tone. think the plan will be appreciated by all who know the value of space on an organ board both for placing pipes and giving them room to speak.

I

I

Now will any one help me in another matter? have a clock with a striking bell like an inverted saucer, abont three inches diameter. It strikes a shriller note than I like-flute F on the fifth line. How can I get a deeper tone in the same space? There is room for a bell of more cup-like figure. The bell is nutted on to a central spindle.

T. S. G.

THE PATENT LAWS AND WORKING MEN. SIR,-I would be glad if you can inform me how I may communicate with the Admiralty. I wish to offer for public trial and use an invention connected with steam marine navigation, which, if successful, will increase the efficiency and economy from 15 to 20 per

cent.

You or others may think or say, Why not get a patent? I can only reply, on behalf of myself and hundreds of other fellow working men inventors, that the social and political barriers with which our stupid and selfish lawmakers, and I may add lawbreakers, have been pleased to surround us, render the patent laws a dead letter or a delusion to working men. These laws, no doubt, work well enough for those who are already well to do, but how many workmen, particularly those who happen to be husbands and fathers, are there who are able to save up the required fees, excepting at a sacrifice of all other interests that are near and dear to them? Bitter experience has taught many of us there is very little security or encouragement to the class of patentees who happen to be poor, no matter how valuable their plans may happen to be, whereas the well-to-do patentee can sometimes reap a glorious reward from trifling improvements. I am thankful and grateful for the publication of the ENGLISH MECHANIC, and hope it will spread, until the bond of union, fellowship, and interchange of thought and opinion shall bind together our present isolated brethren into unity sufficiently compact to influence the actions of lawinakers, and wipe out the mockery of justice now existing in the patent laws, as far as the British workman is concerned.

CYCLOPS.

["Cyclops" may write the Secretary of the Admiralty, Whitehall, London. Let him not be disappointed if he merely receives a stereotyped letter stating bis communication has been received. And let him not cast all the blame on the authorities, for they, it is said, are so inundated with suggested improvements and solicitations for experiments that it would be impossible for them to do all that is requested.-ED. E.M.]

VEGETABLE OILS AND FATS. SIR,-Complying with your wishes expressed in last number, I give a list of the different oil and fat yielding plants, classifled according to the botanical order, with a few particulars. I venture to hope this may prove useful to several readers, and even induce some to send you more elaborate articles on some one of of those products. lu many tropical countries the oil seeds are quite lost, and as well as we have yet ground nuts, palin kernels, jesamum, &c., many seeds more could be imported, and afford a new stock to the European market. I give approximately the produce in oil, but this is only an "average," for some writers count the percentage the number of pounds of oil coming from 100lb. of seeds, others the number of litres of oil coming from an hectolitre of seed. Oils are extracted by three different processes-ordinary presses, hydraulic presses, and by means of the sulphuret of carbon. The seeds are sometimes decorticated before the pressing. Oils are then refined by different operations.

As often oils can be mixed with other sorts, several methods have been proposed for detecting the adulteration. I think the simplest is the one proposed by a French chemist-letting fifteen drops of the oil fall upon a piece of glass underlaid with white paper, and a drop sulphuric acid being put on it, tinctive coloured circle results. The best way of securing the identity is to operate at the same time with an oil of which we are sure and an oil of which we are doubtful, and to compare the reactions.

1.-PALM ORDER, OR PALMACE.E.

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Comou (Enocarpus Bacaba), oil employed for lighting and culinary purposes in the province of Para, well suited also for soapmaking.

Patawa (Enocarpus Patawa).

Mocaya or Mucaja (Aerocomiu schlerocarpa).

Aouara, Kirin nut (Astrocaryum vulgare).

Conana (Astrocaryum acaule).

Cohune palm (Attalea Cohune).

Maripa (Schcelia maripa).

Assay, Oleo or Manteiga de, (Euterpe olaracea) for lighting; Para.

Rondier (Liristonia sinensis), &c., all from the northern part of south America, the West Indies, &c. Palm nut oil (Elais guineensis), called dende in Brazils, and Caiaué in the province of Amazonas, gathered there, but principally on the west coast of Africa; also existing on eastern Africa, near Lake Tangany Ka Two sorts of oil are extracted from that nut, a white from the kernel and a yellow from the fruit or sarcocarp. This latter is the well-known palm oil, used for making soap, candles, lubricating machinery, &c. More than 50,000 tons are exported yearly from the coast of Africa. Centre of the palm oil trade is the dangerous and insalubrious " Bouny," or Bonny

river."

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Hoerve gadung, Java (Tetranthera laurifolia). Hoerve is the Malay name for many laurels.

Japan vegetable tallow (Litsea sebifera, s. Cylicodaphne
sehifera). The fruits of one tree yield enough tallow to
make 500 candles. The laurel oil of British Guiana,
called also sassafras oil, attributed by some authors to
Oreodaphne oleifera, by others to Nyctanbra cymbarum, is
said to be extracted from the tree nearly in the same
manner as maple sugar; it is used in cases of rheu-
matism. I think it is rather a volatile oil.

6.-COMPOSITE Order, or COMPOSITE.
Ram-till, or Niger seed (Guizotea oleifera, Dec., Ver-
besina satira Rorb. 20 per cent. India.
Safflower, Koosum (Carmuthus tinctorious), from India
and Egypt; used for burning.
Sunflower (Helianthus animius). Germany, Italy, and
for culinary purposes.

Madi oil (Madia sativa), originally from Chili. Its cul-
Wurtemburg, France, &c.; yield 1,726 kilogrammes of
ture has been attempted, but seems to have failed, in
seed per hectare, and 32 kilogrammes of oil per 100 kilo-
rammes seed. I think it has the great defect that
in Europe the seeds of the same plant do not attain
their ripeness all at the same epoch, and hence the
quality is altered.

7.-OLIVE ORDER, OR OLIVACEÆ.

Olive Oil, Provence oil, Florence oil, &c. Olea
Europea), cultivated on the whole basin of the Meddit-
terranean Sen; used for domestic purposes, medicine,
preparing cotton for Turkey red dye, oiling wool in
cloth manufactures, &c.

8.-NIGHTSHADE Order, or SOLONACEÆ.
Tobacco oil (Nicotiana tabacum).
9.-TRUMPET FLOWER ORDER, OR BIGNONIACEÆ.
Sesamoil (Sesamusomleiferum, &c.) Seeds called gin-
gelly, jonjoli, jugoline, fergoline, in different colonies.
Benue, in Africa. Oil called Dulin-es-Simsim by the
Arabs, nool esuai, Tamoul; mundie noonay, Teloogoo,
45 to 50 per cent. Cultivated in the Levant, Egypt, in
the East Indies, in Africa, &c. Used for lighting and
culinary purposes.

cent.

10.-SAPODILLA ORDER, OR SAPOTACEE.
Sapote (Lucuma manimosa), tropical countries.
Shea or Cê butter, Galam butter, Bambuk butter
Bassia parkii). Tree 40ft. high. Niger region. 49 per
Illipé oil or butter, India; Illipî Yennai, Tamoul
Bassia longifolia). Used for soap making, burning, and
eaten by the poor; wood very good.
Mohwa oil, Yallah oil. Bengal; maurá, Goa (Bassia
latifolia). For lighting.

Fulwa, Fulwara, India (Bassia butyracea).
Djave, Gaboon (Bussia sp.) Eaten.

Noungou, Gaboon (Bassia noungou). 56 per cent.
Argan nut, Morocco (Argania sideroxylon).
Minusops elengi, &c.

11.-VINE ORDER, OR AMPELIDEE.

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18.

GOURD ORDER, OR CUCURBITACEÆ. Bérall, Senegal: Kurbooz, East Indies (Cucumis citrullas), exported from Senegal to France; for culinary purposes and soap making; 30 per cent. Egusi oil, Abeokuta (cucumis sp.) Abobora, Brazils cucumis sp.) Momordica, Lutla (cucumis dir.)

19.-MALLOW ORDER, OR MALVACEÆ. Cotton seed oil (Gossypium dir.). Seeds imported in Europe from Egypt, the United States, &c.; 18 per cent. For burning in lamps and soap making.

Ambarree (Hibiscus cannatinus), Sunn-okra, East Indies; Gombochauvre of the French Antilles; Canamo de Senegal of Cuba; Bun Kupasi, of Bengal, &c Gang-sooreya, Ceylon; tulip tree; Paris-peepul East Indies; Miro, Tahiti; Poo-arasoo, Canarǝse, (Thespesia populnea), medicinal.

(To be continued.)

BENARDIN.

A WORKMAN'S APPEAL.
SIR, I have been a subscriber to our journal for the
past eighteen months, so I think I am entitled to say
a word or two about it. Above all the letters that
have taken my faney, there is none like the one
on page 187, signed "W. H. J., Plymouth." He says,
the ENGLISH MECHANIC is not so much read by in-
telligent mechanics as by amateurs and scientifically-
inclined middle class people. He may find his answer
to that by the next few words he writes, where he
says, he wishes it had been called "the Scientific
Journal"; for true it is that there is seldom anything
suited to the wants of the working man, and very
little suited for those who have so much time at their
would really suit the practical mechanic, it is 80
disposal, and when it happens to be anything that
encumbered by formula and signs that not one in a
dozen knows anything about. It is useless to say the
English mechanic is a very good scholar, and
knows all these things; I say he does not. The exer-
cise of a little common sense will let us see the falsity
of such a statement. Having to go to work at the
age of fourteen, and work from six in the morning
until six at night, he does not find himself in a
humour for studying algebra, astronomy, electricity,
and such like things. Just take for instance one of
our greatest correspondents, "The Harmonious Black-
smith," Who does he write for? Truly not for the
class from which he derives his name, as might have
been expected, for to my knowledge, he has never
wrote one single line for their especial benefit, but
he writes for those whom "W. H. J." speaks about,.
single correspondent were to write for the benefit of
amateurs and harmonium builders, &c. Now if this
his brother blacks, I think I will not exceed bounds
if I say he would have fifty readers where he now has
one. But now, after I have my say in the way of
grumbling, I may say that I would not miss my
MECHANIC for all the other journals in print, for
although I missed taking it in occasionally at first, I
could no more miss taking it in now than I could-
think of missing my dinner, for I have become quite
interested in some of the subjects going on in its
pages, "Science for the Young" forming one of its
treats; and I am very thankful to see the working
drawings of a slide rest in last week's issue which
is something after the workshop fashion. I should
like to endorse the sentiments of "T. J. O'C.," page
212, and if any of our learned friends would take the
matter up, I would try to learn it, and then our
journal would become doubly interesting to me. I
have tried it from books, but can make nothing of it.
In conclusion, I appeal to the "Harmonious Black-
smith" to let his harmonious friends wait a little,
and give the blacksmith a turn for once. I have
no occasion to inform him that a very great deal of
the drawings come out with the French measures on
them. If he would give us a short discourse on

for burning and soapmaking.
Grape seed oil (Vitis vinefera). Lombardy, &c. ; 18 deg.; English and French measures, so that when they get

12.-CORNEL ORDER, OR CORNE.E.
Cornel oil (Cornus mus). Europe.

13.-NUTMEG (RDER, OR MYRISTICACEÆ.
Yayamadou ouarichi (Firzola sibefera). Abundant in
Guiana; deserves attention for candle making.
Combo, Gaboon (Myristica angloensis), 72 per cent.
medicinally, and for fabrication of candles.
Bicuiba, ucu-uba, Brazil (Myristica bncuhiba), used
Karab, Mayotte (Myristica sp.)

Nutmeg butter (Myristica moschata), Moluccas.
Poondy seed (Myristica malabarica).
4.-CUSTARD APPLE ORDER, OR ANONACE.E.
Monodra Grandiflora, Gaboon.

15.-POPPY ORDER, OR PAPAVERACE.E.
Poppy oil, (Eilette oil of the French (Papaver somni-
ferum). Cultivated in France; seeds also exported
from India; 48 per cent. Two sorts of oils, white and
fabric, used for eating, burning, and painting; second
sort for soap making,

(Argemone mexicana), East Indies and America.
Prickly poppy, yellow thistle; Sheâl Katta, Bengal

16.-CRUCIFER ORDER, OR CRUCIFEREÆ.
Colza oil, rape oil, from Summer Colza (Brassica
campestris), 23 per cent., and winter do. (B. napus 3 per
cent. Plant cultivated in Europe, principally in Bel-
gium; seeds also imported from the Black Sea, the
Baltic, East India, &c. The oil is used for lubricating
machinery, and, after being refined, for burning in
lamps. Trade somewhat impaired since the introduc-
tion of petroleum.

Ravison seed, from the Black Sea, is a wild sort of
celza, often mixed and dusty, yet yielding a good per-
centage of oil.

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SIR,-The favourable notice that appeared a few weeks ago in the ENGLISH MECHANIC of Mr. Dyer's book of replies to Parallax" led me to read that book, and to make a number of computations, with a view to give some definite numerical expression to instance, referred to by him in his introduction) find those errors which many people (Mr. Dyer's friend for it difficult either to admit as true, or to prove false Perhaps a few of the results may prove interesting to

of controversy. I submit the following by way of mauy readers, without exciting or fostering a spirit

example:

1. Given A B 69-091 miles x degrees in S. Let SAB be a right angle, and the triangle be a plane

one.

We shall have

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If in this we substitute different values of the angle B, and compute the corresponding numerical values of A S, we find every possible value of AS from O when B = 0 to 3958 6, when B = 89° 59' 59". A higher value than this is not possible of the first 5 figures, and this is the value that" Parallax " has assigned to the sun's distance; and this is the sort of computation he made to obtain the distance of the sun S from the earth's surface, A B, supposed to be a plane. The most notable oversight in this matter is that the computation, instead of giving the sun's distance, in reality gives merely the earth's radius, which was assumed to give the 69-091 miles for the length of one degree on its surface.

Let now A be a point in latitude 200 north (near Vera Cruz) on 20th May, the sun's declination being also 20° north, S will be vertical to A at noon. At a point 400 south latitude (near Valdivia, on the west coast of America) S on the same day at noon, will be elevated 30 only, that is B = 30°. Now the sun's diameter to the observers at both A and B, Vera Cruz and Valdivia, subtends an angle of 31 40 on the assumed day. These are matters of every day observation for the last 100 years or more, and therefore may be relied on. Now, continuing the assumption that the triangle is a plane one, compute the value of SB by the formula

SB 3958-6 cosec 30°.

It is found = 2 AS = 7917-2 miles earth's diameter.
Hence the sun, to the observer at Valdivia, must sub-
tend an angle = (31' 40") by the first law of perspec-
tive, see Malton, Book I., which being contrary to
observed fact, shows that the assumption of the
triangle being a plane one, is erroneous, because every
other step in this reasoning is rigorously correct.
2. The triangle formed by great circles through
Cape Horn (H), Cape of Good Hope (G), and Port
Jackson (J), seems to be less perfectly known than I
believed possible in our present state of geographical
science. Mr. Dyer, on the authority of respectable
chart publishers, gives H G = 3601, G J 5813,
HJ 5470 miles. Parallax " (who by the way is no
authority at all, as he merely gives the even thousands
estimated by some unnamed navigator, as having
been sailed over), states these distances as follows.
HG = 6000, GJ 8000, H J = 8000. But even so I
was led, by noticing the differences to be unaccountably
great, to compu te them from the latitudes and 'longi-
tudes as given in well known works. I find H G = 4135,
GJ 6824, H J 5831. Will our author of "Read-
ings from the Globes," or some of your mathematical
correspondents, be good enough to verify my results?
Can it be possible that we are uncertain to the extent
of a 1000 miles, of the distances between our three
great southern nautical points, and to the extent of
1906 miles in the usual route of circumnavigation?

TO MILLERS.

M. L.

SIR,-Your correspondent, "E. O." (in No. 272 of the ENGLISH MECHANIC), asks for a recipe for filling up the broken joints in his millstones. Four years ago I filled holes in a stone with a composition of alum and red lead. It is in yet, although the wheats that pair of stones have been grinding have been principally hard foreign. The red lead binds the alum, and makes it tough. I always put grease in the ladle with the composition, and melt gently. I try to keep it from boiling. When melted I skim off the grease, and with it the scum of the alum, and then mix in the red lead. But if the joints are well cleaned and wet with water, good plaster of Paris will stand a long time; it does in stones for grinding rice, which is harder than most kinds of wheat.

I beg to suggest to Mr. Smith that he cut holes in the head leather of his bolting cloth, halfway between the existing ones, or remove the loops at the bottom. It would ease the working of the cloth by giving it a lead the same as the brushes of a wire machine usually have. I have tried it, and found it answer. It is no "notion" of mine, but Sir Wm. Fairbairn's, or at least some of his millwrights.

A STONEMAN.

Sin. Mr. Evans has failed to bring "A Stoneman"

PERSPECTIVE.

SIR,-Linear perspective is that branch of matheobjects not as they really are, but as they appear to matical science by which we are enabled to represent the eye. Let the spectator look down a street of regularly-built houses, of the same size, and he finds as they recede from the eye they appear to become smaller, although they are really all of the same size. If he now changes his position by going to the other end of the street, he will find that by looking towards his previous position the houses that before appeared large are now the smallest, and vice versa. Perspective may therefore be said to treat of appearances, while readily find instances to illustrate the above, which geometry treats of realities. A quick student will are by far too numerous to insert here. As it is not my intention to use any unnecessary theory, the most careful and thoughtful attention is requested, on that Eccount, to that part which is introduced.

Perspective will be more readily understood if thought of as governed by certain planes. All perspective representations are supposed to be gained on a vertical transparent plane which is between the spectator and the object at which he is looking. This is always at right angles to the direction in which he is looking. This transparent plane is always supposed to be present; in fact, it is inseparable from a perspective drawing, as it is the picture plane. It is represented by the paper on which the drawing is made. The best way to illustrate this is to suppose the transparent vertical plane to be a sheet of glass, standing upright on the ground, the spectator being some twelve or twenty feet from it, and looking at some object or objects on the other side; and could he, with a steady hand, and without moving his eye, trace the objects on the glass, he would have the most perfect perspective representation that could be obtained. Referring to the diagram, BGG GII is the picture plane, A the station point, N the eye of the spectator, C the object behind the plane, D its representation on it as seen by the spectator.

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The ground line, or base line, is formed by the intersection of the picture plane with the ground B G G G. The horizontal line, or horizon, is drawn across the picture plane at the height of the spectator's eye; therefore, if the spectator move up or down, the height of the horizon changes also. But as five feet is the height of an ordinary spectator, it is generally chosen for perspective diagrams. The line of direction F FF is an imaginary line, supposed to be drawn from the spectator's eye to the horizon, so that one end is the spectator's eye N, the other is the point of sight E, or the centre of vision.

As the student

The ground plane is the floor of the diagram, always supposed to be horizontal, and extends from the picture line, which is its nearest edge, backwards till lost in the horizon. These two important planes must never be lost sight of in perspective. begins to get familiar with them they had best be known to him as the picture plane PP, and ground plane G P, as it is useless to go further without a pretty good knowledge of these planes and some lines in conLet the student propose and pection with them, answer in writing the following questions on the subject:-1. What is the picture plane? 2. What is the ground plane? 3. What is their relative position? to his views on the balance question. However, I 4. What is the nearest edge of the ground plane? 5. think "C. M.'s" letter and John Botting's, pages 226 How far does that plane extend? 6. What is the line and 227, leave little more to say on the subject. of direction? 7. What governs and determines its If "A Stoneman " balances his stones stand-length? 8. Say what we find at the ends of it? ing, and then starts them up to speed, I think he will perceive that not only will the running disagree with the standing balance, but the difference will be very decided-at least I have proved this by experience, and have yet to learn how the running and standing balance can possibly be the same. Of what H use is the standing balance? If a stone be balanced as it works, surely this must be the proper way. Many thanks to "One Eye" for his answer to my query touching grinding. I note that he thinks 200 revolutions per minute too fast for a 3ft. 4in. stone; but from experience I find that if small stones are not driven fast, they will not do much work. But I should like the opinion of some of our practical brethren on the subject.

SERGIUS.

B

F.L.

D.1.

C. V.

INT OF DIRECTNS

VISUAL RAY

BASE DE CONE OF

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SIR,-After so many remarks from master millers, All horizontal lines that retire from the spectator
a few words from a journeyman may not be uninte- vanish to some point on the horizon. Thus, all lines
resting to your readers on the subject of balancing. at right angles with the PP vanish to the centre of
The great trouble which has often been experienced vision. The points of distance are points on the hori-
in balancing causing the necessity, or supposed neces-zon found by taking the length of the line of direction
sity for a patent balance, I have always found to arise right and left of the centre of vision. These points
from something else besides the mere difference in are vanishing points for all lines at an angle of 45
weight of portions of the stone. I once had a stone with the PP. All other vanishing points must be
under my care which had a true running balance, and found; but the two mentioned are always ready.
yet always wore down on one side. After trying all
the means I could think of to rectify it, I at last tried
the crossbar, and found that its centre was slightly
out of the centre of the stone, but the short side of the
stone was the one which wore the most. After think-
ing it over, I concluded that the extra leverage which
was gained by the wheat under the long side forced it
up, and so pressed the other hard on to the bed-stone;
but 1 should like the opinion of some of my dusty
brothers upon it.

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12. How are the P D's found? 13. What must be done with all other lines (horizontal) at angles other than 90 and 45? 14. What accompanies every vanishing point? 15. What are the measuring points for lines at 90° to the P P, and how are measuring points found?

The following is a list of abbreviations common în perspective:-V, centre of vision; D P, distance points; SP, station point; V P, vanishing point: M P, measuring point; H L, horizon line; GL, ground line; P P, picture plane; G P, ground plane: 0 P. original plane; Vg P, vanishing plane; PL, picture

line.

It will be well for the student to get master of the theory, and begin with a little practice. few foregoing hints, and next time we will leave the J. W. BEDFORD.

MUSIC.

SIR,-I was much pleased to see "Gimel's" remarks in last week's MECHANIC on the subject of old musir, and hope, as this subject has been started, we shad have some interesting information concerning the music of the ancients.

Even granting the somewhat doubtful antiquity which Gimel "assigns to the tune Nas Galan, we have, I think, in the Gregorian tones which are still sung in our churches examples of a much earlier style of music. The first four of these tones were introduced into the service of the Latin Church by Ambrose, who was Bishop of Milan from A.D. 374 to 397: and the means by which they were distinguished seem to indicate a still more remote Hellenic origin: the others were afterwards added by Gregory, who flourished during the 6th century. There are a few tunes in use in modern Jewish synagogues which are said to have formed a part of the old Temple service. Though this cannot be proved, and indeed is scarcely probable, there is no doubt that they date back to very early period.

While on the subject of music, I may perhaps be allowed to say a few words in favour of the tonic sol-fa method of singing, which has lately been referred to in your pages with a contempt which I think is quite unmerited. After some little experience with this and other systems, I am of opinion that it is the best known method of teaching to sing at sight. 1. Because, instead of perplexing the learner with signatures of, perhaps, 3 or 4 flats or sharps, it teaches at once the great principle of key-relationship, or the relation of all the notes of a scale to its tonic, so that a sol-faist can sing a line in A flat just as easily as if it were set in the natural key. 2. Whilst the learner, by the old notation, is going through the hard mechanical drudgery of practising all the intervals of the scale-a task so difficult that many give it up in despair-the sol-faist, by observing the mental effects of the different notes (a knowledge of which is indispensable in the higher branches of the science), is able in a short time to reproduce them at pleasure, and thus to sing at sight. 3. By first teaching the strong notes of the scale-the tonic 3rd and 5th-on which all the others lean, it thoroughly tunes the voice, and prevents that flattening which is so common amongst learners by other systems. 4. By means of the modulator it represents to the eye the exact intervals through which the voice moves in passing from one note to another, and teaches transition in a 5. It gives a perfect very clear and simple way. distances pictorial idea of time, by mapping out each page into proportionate to the actual length of the notes, and distinctly marks the accents, including the secondary or medium accent, for which the old notation has no sign at all! 6. Music can be printed very cheaply in this notation, and thus it is placed within

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CHEMICAL FLORICULTURE AND POMOLOGY. SIR, May I ask your numerous readers, and especially Mr. S. Rogers, whether they know of any plants the flowers of which have had their colours changed by the application of chemicals? If they do, will they please state the name of plant, the colour changed, and what it was turned to; also the method of applying the chemicals, and what they were? I think if there is any truth in this theory it would have been turned to account before now. I have not the slightest doubt that I could name several nurserymen and florists who would gladly give £50 for a bise dahlia, for instance; and I dare say a blue chrysanthemum would find a buyer at a similar price Instances could be enumerated by the score where some particuiar colour is absent from a genus of plants for which florists would give a good sum, if they could depend on a specimen of that particular colour blooming true.

Again, if it is possible to change the colour of the blooms on a plant by the application of chemicals, might it not also be much easier to change the flavour of, or impart a different aroma to, any particular vegetable or fruit thought worth improving? For instance, if we could impart to the vegetable marrow and the pumpkin the flavour of the peach and the pineapple; or to the turnip and the mangold the taste of the apple and the pear-not to mention bestowing on the potato the aroma of the truffle-what an advance in science would not that be! and what a hero would not the discoverer of the modus operandi be considered amongst epicures and gastronomists!

SAUL RYMEA.

PECULIARITY IN EYESIGHT. SIR, I think "Blackburn Amateur" is wrong with regard to the peculiarity he mentions. His eyes have adjusted themselves to the focal distance he is accustomed to work at, and the crystalline lens has lost the power of accommodating itself to different foci. It is a parallel case to my own, only in my case objects appear double and misty beyond a certain distance, instead of treble. Short sight is generally supposed

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