is holding is an extra brake, by means of which the engine can be stopped at 10 yards' notice. Its greatest speed on the high road is 20 miles an hour, and in town 10. The coal and water are kept on either side of the boiler. The carriages in construction are just the same as any other railway carriage, with the exception of the wheels, which are as already described. It is the invention of a gentleman named Lormargot.

H. GARLAND.

READINGS FROM THE GLOBES.-III. SIR-Frequent allusions are made to the different constellations of the heavens both by ancient and modern poets, and this arose not only from the custom amongst all nations of making use of figurative language, but because the sowing and reaping of corn and agricultural productions depended upon a right observation of the rising and setting of particular stars. When, for instance, the sun had reached the Tropics, or turning points, it was necessary to reckon so many days before it was advisable to undertake particular work, but in these times of accurate computations and astronomical observations, the calendar is employed, which is much simpler. Thus, the poet Hesiod in his Works and Days makes mention of the Tropics, and the Roman poet has constant allusions to the signs of the Zodiac.

In order, therefore, to enter into the beauties of these writers we should have accurate notions of the course of the saw through the Zodiac, and it will be our business in this letter to show by the globes the longitude and declination of that bright luminary as he proceeds in his round. It is not our purpose now to enter into auy argument either for or against the Copernican system, as this has been amply discussed, but merely to illustrate certain phenomena which can be explained on either supposition-namely, that the earth moves round the sun, or that the sun moves round the earth, and to illustrate the better, we will make the latter supposition. The figure is a representation of the two outer circles on the wooden horizon of the globe,

nearer to the sun by 4 millions of miles in winter than we are in summer, and, consequently the warmth of o ur summer arises not from our proximity to the sun, but from the fact of his being longer above the horizon and his rays, owing to his altitude, darting less obliquely upon the inhabitants of the North Temperate Zone. These maps show the situation of the earth in his orbit for every ten days, as well as what sign of the Zodiac he is in, and should be possessed by those desirous of accurate notions upon this subject. Thus it appears that the sun's longitude is really the distance which the earth travels in her course round the sun, which, computed in miles, will be found to be more than 65,000 miles per hour.

T. S. H. P.S-Mr. Dyer states the following sentence in Letter 1. to need correction: "As the globe turns on is axis from west to east, those who live in west longitude. must have their time earlier than those living in east longitude, because they will not come in to the enlightened hemisphere so soon." He says the word "earlier " should be "later." I submit the sentence must stand without correction. Turn the globe on its axis from west to east, England will come into the enlightened hemisphere sooner than America, which is in west longitude; but the time in America is earlier than in England, for when it is 12 o'clock at London noon, it is 7 o'clock in the morning at New York; so that we come into the enlightened hemisphere sooner than the Americans, and yet their time is earlier than ours. They in the latter part of the sentence must be connected with the nominative of the sentence.

and the eclipse may represent the ecliptic on its surface. The sun's longitude, then, and indeed of any other celestial body, is its distance from the point Aries eastward. It is from this point that the reckoning begin, and it will be found from an inspection of the figure, that he is at this point on March 20, he then passes through the signs of the Zodiac as they are marked in the circle, and reaches them on the months immediately above them. Thus the sun enters Cancer, June 21, and generally speaking he enters a new sign on the 20th of each month; that is, apparently enters, for the stars being millions of miles distant from both the earth and the sun, his entrance into them is obvious to the eye only. Concerning the origin of the names assigned to the signs of the Zodiac, there seems to be some uncertainty, but it is generally supposed that they are intended to denote the peculiarities of the season at bese particular times. Thus he entered the signs of the Ram and the Bull, when farmers were busy in rearing domestic animals, and at his greatest height, he begins to recede, or, like a crab, to walk backwards. The Lion being a native of the Torrid Zone denotes the heat of the season, the Balances when the days and nights are again equal, the Archer, the hunting season, the Waterbearer, the watery aspect of the clouds, and the Fishes that the seas were open for mans supply when the ground was hard from frost, and uncultivated. The declination of the sun means his distance north or south of the equator, his greatest declination being 2340, when he has reached the meridian line on which the angle is measured, which the ecliptic makes with the equator, and he then shines over the North Pole, and 2340 beyond it. But to this subject we shall have afterwards to advert. It, then, we wish to know the sun's longitude by the globe, we have only to look on the wooden horizon for the month, and the corre sponding circle beneath will show the sign, and if we

TO MILLERS.

SIR,-I am glad to flad an improvement in the letters The remarks of respecting mills and millering. C. M.," on the balancing of stones with Clark and Dunham's patent, I consider good sound reasoning, and I hope we shall hear again from him. Also J. Botting's remarks on the swish in stones, are interesting and true. I having tried the same remedy for similar evil and corresponding results. R. R. Smith gives us some useful hints betimes. I hope all our dusty brethren, who have a little useful information, will please send it to our MECHANIC for the common benefit. I will just ask the above, or any other, if they can give me a good remedy for filling up broken joints in millstones; I have tried alum and borax, but cannot make a good job of it.

E. O.

SIR,-I cannot say I am prepared to dispute Mr. Evans' theory that the cause of a stone's standing and running balances differing is "The balance weight does not coincide with its counteracting object in its radial distance from the centre," but in my blindness I cannot conceive why it should not. He asks me if I cannot alter a stone's standing balance by raising or lowering the weights when running. I have already said I have found when a stone's standing and running balance do not coincide, something was wrong, independent of the balance; but whether it would alter or not if both balances coincided, I am not prepared to say, but to my unenlightened intellect it seems improbable. But in spite of Mr. Evans' scientific reasons why, and my inability to dispute them, some very ugly facts (to the contrary) stare ine in the face. And as Mr. E. says "Facts are stubborn

to cool the meal before it enters the bolter; it will be seen by this that a miller cannot keep his ground mea! by him for two or three days to cool, unless indeed be has extra silks to dress it up with. 3rd. There is another matter that is against them, namely not being able to change any number of the silk and put another on in a few minutes, according to the stuff that wants dressing and the time of year, as of course for damp wheat meal the silk should be coarser than for dry foreign wheat meal. To obviate this I have, in conjunction with some parties in Manchester, brought out a silk machine that occupies a great deal less space than the present silks, and any sheet may be taken and another put in in a few minutes. 4th. In dressing with a silk bolter it is impossible to get the bran as clean and bright as by dressing it with a wire machine Consequently I generally put a small machine to take the bran out before it enters the silk or after it leaves it, as by that means everything is cleaned up as well as possible. 5th. By dressing with the present silk bolters there is not more than one-third of the silk that actually dresses, as the rails or ribs inside the reel as it revolves carries the head up and drops it on to the silk near the bottom at the opposite side of the reel. It is this that forces most of the flour through the silk, but it at the same time gives the silk a sudden twitch, which of course is injurious to it. E. DAVIES.

things," I ask both him and Mr. Smith how we managed to balance our stones so that they "hummed like a hive of bees," made bran like a bee's wing," and as good a per centage before we had the patent balauce as we do now with it, and why every serious fault that occurred then will now, in spite of balance. And as to despising the standing balance as virtually of no use, and practically non-effective," that idea has recently done serious damage. If it be of no use, it is mysterious how we managed to make our stones work as well without the patent balance as with it. repeat the fault of a stone's dragging lies either in not working parallel with the face, or unlevel bedempty cogs or their pitch circles not meeting, or irons stone, or faulty face. Of course the running balance will keep a stone from vibrating (?). I know of stones that have received a good running balance, but went empty, and on being freed by the spoutsman, comstopped knocked off 12 months' wear of skirt. menced kicking violently, and before the mill could be was the running balance that it did not keep them steady? What was the cause of it? And why did it not occur when being balanced? The more untrue the face, irons, &c., are, the greater difference there is in the two balances-so great as to drag off the skirts when starting and stopping if the running store has a running instead of a standing balance. Evans asserts, the cause of the difference in the two balances is owing to the unequal specific gravity of the burrs, or because the balance weight does not coincide with its counteracting object in its radial distance from the centre, how is it we often see parties try the running balance of their stones every three or four dressings, and find it differ each time? To me it looks very much like a different face to the running stone.

Where

If, as Mr.

A STONEMAN.

[Will some miller, or any one else who may know. millers of Great Britain and Ireland ?-ED. E. M.]

wish to know the declination we have only to bring tell us how we can get the names and addresses of the the sun's place to the brazen meridian, just as we find the latitude of a place, and immediately over it is the declination. We may remark that the orbit which the sun makes, or the earth, for it is immaterial for SIR,-Having in my letter in this week's issue of the our purpose, is not circular, but elliptical, and those ENGLISH MECHANIC endeavoured to show that a silk who wish t pursue the subject will do well to study bolter must make a better or finer sample of flour than Mr. Proctor Maps, published by Messrs. Longmans, a wire machine, so that, after showing the advantages where they will find not only the orbit of the earth, of said bolters, I will now describe some of their disbut the orbit of all the planets round the sun accu- advantages. In the first place, owing to the great rately described according to scale. By a study of length they have to be made to dress from, say, even these maps it will be seen that the sun is in perigee four pairs of stones is very much against their adopor nearest to the earth in winter, ten days after he tion in many mills because of their taking up so much has entered Capricorn. December 31, when, according room. 2nd. As they will not, generally speaking, to Mr. Proctor's scale of measurement, he is 91 dress more than from three to five sacks per hour on millions of miles from the earth, and that he is in an average, or about one-fourth the quantity a good apogee, or at his greatest distance from us, in Mid-wire machine will dress, causes them to be worked summer, July 2, when his distance by the same scale continuously as the mill grinds, and there is often fixed 48 95 millions of miles. Thus we find that we are over the head of the machine a hopper boy or cooler,

COMMERCE AND TRADE.

SIF.-As this subject has been opened, and is one which, directly or indirectly, is of vast importance to us all, it may be as well to say a little more about it, especially because its very vastness involves the consequence of very partial views being caught of it by most minds; hence it is, that so many, even intelligent people, are captivated by that delusion, "protection to native industry," which is now set forth under the disguised, but equally delusive, form of cheap what we want, because those from whom we "reciprocity," or in other words, refusing to buy buy have not sense enough to buy of us, what we offer them cheaper than they can otherwise obtain it. This is the very delusion by which "F. W. M.," page 257, is somewhat afflicted. He does not see the whole bearing of what he says. Let us accept at its worst the result he sets forth. "Our inen are compelled to emigrate in large numbers." What of that? A temporary suffering to them and others-a resulting unmixed good to them and all-they leave a country overstocked with labour, where, if they cannot produce, they are a burden on the producers; they go away, and at once become producers to their own great benefit, and large customers to those who remain behind.

Rightly considered, the necessity for emigration is a great proof our prosperity, for it means excess of population, but an excess not due to diminished work (for any intelligent man knows that the total work of the country is vastly increased every year), but to the rapid ratio of increase of population, and to temporary changes in the nature of work, which at times throw out whole classes of workmen, who are then unable readily to find fresh work, not from its deficiency so much, as from the competition that involves with those already engaged in it. Now nothing is much more certain in political economy than that a rapid increase of population is a consequence of prosperity. Stagnant nations never increase-they very commonly decrease in number, and this is only one form of Nature's universal law, that creatures only multiply where there

is food for them.

Even one year's bad trade, or disaster, is marked by diminished birth rates in the next, as well as increased death rates.

Of course it is hard to look beyond the immediate personal action of these laws, and hence it is that so intelligent a race as the Am-rieaus violate them. Instead of recognising the unlimited advantages Nature gives them, as producers of raw material, they wish to do everything themselves, and seek to be manufacturers, which those very advantages forbid, by their effect on the labour market. The consequence is, that while a few years ago they were dangerous competitors in every market, since they adopted their tariff system, we are beating them everywhere, and literally driving their flag off the seas. I quote the following from the "New York shipping and Commercial List":"No better commentary upon the decay of American navigation interests can be had, than is afforded in the fact that the Novelty Iron Works have sold off most of the machinery and tools; the Allaire works are now occupied as a stable; the Etra Iron Works have ceased to make marine engines; the Fulton Iron Works are for sale; W. H. Webb's shiovard is to let: Henry Steer's yard is empty; the Continental Iron Works are almost deserted; and grass is growing in nearly all of the shipyards which a few years ago were filled with workmen." It may be said, that something similar applies to London, but that is only because other English ports are taking the trade. English shipping is supersediag American, and there is no other reason than this --America tries to make her own iron, &c., which she cannot, except at high price, instead of buying ours cheap with the corn and other things she can really produce well, and thereby indirectly throws away the friendly union with us which would result from being mutually necessary to, and benefactors of, each other.

SIGMA.

SIR, F. W. M.," on page 257, eeems to have fallen into the trap that "Saul Rymea" laid. He believes that England is getting drained of her wealth, by an outflow of money sufficient to make our exports balance our imports-a very common error. It is necessary to remember that, with the most insignificant excep tions, trade is barter; the fluctuation in the amount of gold held by England from year to year, may be entirely disregarded in examining her trade with the whole world, and this one fact should be steadily kept in sight, that one year with another, the goods we send out to the foreigner, are considered by him equal in value to what he sends us in return. Take the case that I gave, and which "F. W. M." holds up to ridicule. I send out a cargo, which costs me here £18,000, but when it reaches the foreigner, it is worth

Ans. 77 071b. per. sq. in. Ex. 2. The diameter of a safety valve is 2.5in., pressure per square inch 201b., distance from the fulcrum to the centre of the valve 3in., weight on the end of the lever 401b., effective pressure of the lever and valve 81b. Required the length of the lever.

Let d represent the diameter of the valve, e, the decimal 7854, p the effective pressure of the lever and valve, w the weight, s the pressure per square inch, t the distance from A to B, and the unknown part A to C.

Ans. 6-762in.

Ex. 3. The diameter of a safety valve is 3in. distance from the fulcrum to the valve 3in., effective pressure of the lever and valve 6-25lb. Required the weight to be placed 24in. from the fulcrum to te equal to 80lb. per square inch.

Let & represent the diameter of the valve, e the decimal 7854, the ratio of AC to A B, p the effective pressure of the lever and valve, s the pressure per square inch, and r the weight required. Then

Then

= 1

dix exp - -f 2:52 × 7851 = 4908 area of valve. 20 pressure per sq. in. 98.160

6-762 length of lever.
40 weight on

90-160)270-480(3 270-480

Ans. 3in.

The divisor 90 160 is obtained by deducting the weight of the valve and lever from the direct pressure 98.16lb.

Ex. 5. The lever of a safety-valve is 24in. long, 3in. from the fulcrum to the centre of the valve, effective weight of the valve and lever 625lb., pressure per sq. in. 80lb., weight on the end of lever 69-90475lb. Required the diameter of the valve.

Let r represent the ratio of AC to A B, w the weight, P the effective pressure of the valve and lever, S the pressure per sq. in. e the decimal 7854, and the required diameter. Then

Ans. 3in. Ex. 6. What is the area of an annular valve whose greater and lesser diameters are 12 and 4in.? Let d represent the diameter of the greater, and the diameter of the lesser, e the decimal 7854, and z the required area. Then

sq. in. Area of whole circle 122 x 7854 = 113 0976 lesser 42 x 7854 = 12:5664 100:5312 Ans. 100-5312 sq. in.

Ex. 7. To what height must a safety valve 3in. in diameter be lifted to allow a free escape of steam equal to the area of the valve?

Rule. Divide the diameter by 4, the quotient will give the height. Let d represent the diameter of the valve, e the number 4, and z the required height. Then

d

80 pressure per sq. in.

565 4880

6-25

8)559 238

69-90475

Ans. 69 90475lb.

= 9

SIR,-The ring principle on all instruments of the flute genus, is the same, it gives the power of closing two or more holes by the action of one finger only. The invention of this system belongs to a Captain Gordon, who conceived the idea in Paris, about thirty years ago; the application of it, however, is Böehm's a professor of Munich. I think a little work" The Flute in its Transition State," by the Hon. and Rev. H. Skeffington, would interest "Another Flautist." Hatchard, or Skeffington Piccadilly, are the publishers. As a soloist I am acquainted with nearly every form of flute. For the Böebm fiute I cannot say much; it is an expensive instrument; the faults I find with are, the constantly-recurring difficulties in executing rapid and continuous passages, especially in the third octave, arising from the cross and back fingerings. To illustrate this, the B Hat, which is produced naturally and easily on the Nicholson flute, is fingered on the Böehm by placing the third finger of the left hand on the ring of the G hole, and F sharp is fingered by pressing down the ring of the E hole; these are very awkward and unnatural fingerings, added to which, the quality of tone in the third octave is thin, weak, and the notes bear very sharp (in the old flute they bear flat), and it is almost impossible for an amateur to blow them in tune. This arises from the fundamental holes being made too large, and without due attention to the part they are required to take as vent holes in the production of the notes in the third octave. But should "Another Flautist" desire still to hear more of the Böehm, I shall be happy to give him information. Tune, tone, and facility, are the things sought for by flute players of all classes, and with your permission I will now describe as briefly as I can, a flute in which these qualities are combined to the fullest possible extent As a professor of the flute, having no pecuniary interest in flute manufacture, I continaed to use the Böhm because its powers and capabilities were so great, notwithstanding the toil it imposed upon the performer,especially with the open G sharp key. Nearly eight years ago, the late Mr. John Clinton showed me his flute, called the "Equisonant," a vast improvement on the Böhm, which I have used ever since. I subjoin a sketch of it, with an explanation. In the Böebm the thumb key makes C natural, in this flute that key makes both B flat and C natural. There is a small open key at a (the C natural key), which is kept shut by the thumb key, and when the latter is opened for B flat in the usual manner of fingering this note, the C natural key is kept closed by the second finger of the left hand pressing down the ring surrounding the A hole. There is also an open F sharp key at 6, which is shut by the second finger of the right hand pressing on the F natural hole ring, the third finger of the same band closes it in making D and F natural, for which latter note the "fork fingering" is used in all rugged and difficult passages. The F natural key (short) remains. At e there is a lever for acting rapidly upon either the B flat or C natural keys. At d is a Your correspondent lever for the D shake key e. knows not what he asks; the mechanism of flutes has been a vexed and most intricate question.

SABLE.

POST-OFFICE TELEGRAPHS. SIR,-I shall be glad if you will allow me, through the medium of your pages, to ask some of your able correspondents, the following questions, which are important to many in the same circumstances as myself. It is well known that the Post-Office has lately acquired the telegraphs, and a great many postmasters have to waste hours daily in watching the instruments, and therefore I wish to know whether existing single needle instrument, ia such a manner, that we shall have warning without the watching now tedious to

3: 24: 1:8

Ex. 4. A safety valve has a lever 6762in. long, a weight equal to 40lb. on its extremity, the pressure per square inch 201b., effective pressure of the lever and valve 81b., and the diameter of the valve 2.5in. Required the distance from A to B. Let d represent the diameter of the valve, w the weight, the length of lever, p the pressure per square inch, e the decimal 7854, f the effective pressure of the valve and lever, and x the distance required.

diam., and in. thick outside, and holds 18 No. 24 cotton, and the Elliptic holds 14 yards, the diam. being in., and the outside thicknessin. Wheeler and Wilson's spool is represented at Fig. 1, a front view, and Fig. 2 a section. It is formed of a pair of thin steel discs, a b. fixed on a brass axis C, with a hole through it, which fits on the shaft of the machine to receive a rotary motion for winding on the thread, and in the space between the double convex spool. A very slight variation of tension may be given by winding on the thread more or less tightly, but it is too limited to be of much use. To provide a tension on a spool, the following plan has been adopted. A pair of flat discs, with the thread wound on the axis, which also has a hole through it, is placed within a case or shell, having an axis to retain the spool in place, and to allow it to unwind freely. In the rim of the case or shell, holes were made for the thread from the spool to pass through, to give tension in the same manner as in Thomas's shuttle. There are machines of different makers working this kind of spool, but they are not successful compared with other machines, although it may be wrong to trace the failure to the spool only. In some machines, the spool was applied horizontally, as illustrated in Fig. 3, a plan, and Fig. 4 a sectional elevation; a is the spool, composed of two flat discs on an axis, with a hole through it. The shell or case b, has a centre pin, on which the spool a revolves. The thread passes from it to the holes C, and is passed through one or more to obtain the tension required. The frame d d of the machine, is bored large enough to contain the spool, and a rotating hook e secured to the pinion f an axis, g, passes through the pinion. The top end of the axis forms the bed on which the spool and case rests, and the lower end is secured to the frame of the machine. The pinion is driven by a rack motion in some machines, in others the hook receives a direct circular movement. The action is as follows:-the ascent of the needle in the needle slot, throws off the loop, the hook takes it in its rotation, or its vibratory movement, and opens it, when on the back end of the hook, then carries it more than halfway around the spool case; here the needle pulls the thread off the hook, which returns ready for the next stroke or stitch. In machines which make a complete rotation of the hook, the needle thread is less liable to break, and more easily slips off the hook. When the needle thread has been passed around the spool case and released, it has to be pulled up through the needle plate at a great velocity-for every stitch from 2in. to 3in of thread must so pass. This is usually done by a spring above the needle, and the least accident to so delicate an instrument, puts the machine out of order. A thin fabric, stitched by a shuttle, compared with one stitched by a spool machine, shows in practice what may be expected from theory-viz., the less quantity of thread passed through the fabric, the better the stitch, and the longer the loop passed through the fabric, the more uneven it must appear, laying below the surface on the upper side, or drawn too deeply into it, and forming too thick a ridge on the lower side. The spool machines are not made or sold because of this quality, but because of certain other merits they possess. All the best qualities in the various machines have not been combined in any machine yet made, nor are they likely to be. This thought should humble some of the members of the sewing machine family, who are given to overmuch boasting. Little remains to be noticed about the various instruments employed in the formation of the lock stitch, until the machines are described and compared.

Other contrivances have been patented, or proposed, but not of sufficient practical value to describe them; and some of these here noticed, serve to show the many ways proposed to do the same thing, and to point out that the impracticable may become the stepping stone to the useful; or to show inventors what has been already done, or attempted, and to save them the trouble of re-inventing and re-patenting. This has been done to a large extent, and many years' experience in searching the patents, and making new machines, and experiments for inventors, leads me, as a matter of duty, to warn those who are fond of new ideas to be careful. One of the most unsuccessful attempts to form the lock stitch, and one often attempted, is to use a large reel of thread below in a spool, shuttle, or its equivalent, so that it will last as long as the needle thread, and require no re-winding. One of the most likely plans to do this, was to place the reel in a large spool case, having an external screw, which, by rotating, carried the needle thread from its front to its back end, the holder and driver being arranged to let the thread pass over it without obstruction. The arrangement was so far practical, but it involved long needle loops. More time is lost in pulling up long needle loops than in rewinding spools or shuttle reels. The spool, laying on its flat bed, and having a horizontal moving hook, is not so well adapted to work as one vertically placed. In the former the hook in taking the thread from the needle pulls it out of its slot horizontally, and thus bends or breaks it. The vertical pull of the hook is a far better arrangement, the needle being less liable to strain or breaking; and the thread pulled more in one direction only, or chiefly downward instead of across the needle: A vertically oscillating book has been applied to carry the thread around the spol, the hook being curved to nearly match the circumference of the spool or holder. All such contrivances are more complicated than direct circular motion, and the complicated in mechanism is nearly always leading to failure; the simple, giving less trouble to learn, or keep in order, leads to

It is not advisable to do more than allude to other inventions for making the lock stitch. Shuttle machines are made to work with waxed thread, kept heated by gas; in some the loop of the needle thread is kept open by a hook, so that the shuttle passes through without dragging on the thread. In one machine working leather the shuttle is made to work

The revival, and abandonment of inventions and imitations is abundantly illustrated in the history of the sewing machine. A museum containing one machine made to work from each invention, would be very interesting to the mechanic; it would be a very large collection, and show each link which connects together the extremes of difference. How unlike, at first sight, appears the Howe, and the Wheeler and Wilson machines! If they were taken to pieces, and then mixed together, we should only find a resemblance in their needles, all the other parts being dissimilar, yet adapted in a different manner to make the lock stitch. The instruments for making the lock stitch, already described in these pages, connect link by link, with slight shades of difference, the extremes of form and action. Some of these contrivances never came in, or soon went out of use, and only served to teach what could not be done, or to suggest ideas for better inventions. It is strange to find in "the development of species," and the development of invention, there is a resemblance. The sewing machine was not a perfect and complete invention at the commencement, but was developed by successive stages of improvement; the strong and useful predominate, the weak and useless die out. Selection of the right stitch is the first thing to do by those who desire to make a sewing machine, then to copy the best mechanical contrivance to produce the stitch, to study in detail the formation of the stitch, and working of the thread. The workmanship should be good, but it is of less importance than correct principle and proportion, There should be harmony of movement; needle and shuttle must be in time, and work smoothly. Further particulars will be given when the machines are completely illustrated, and at this stage many may be tempted to make sewing machines without having first paid sufficient attention to the formation of the stitch.

Let such be warned in time, "a stitch in time saves nine."

A PRACTICAL MAN. P.S." Jacquard," 3848, Notes and Queries, is advised not to be in a hurry to begin making a sewing machine. His questions show great discernment, but involve too many considerations to be answered in a brief reply to do him service. What he requires is partly explained at page 232, and the rest will be fully dealt with when the subject is sufficiently advanced. Machines of different classes will be fully illustrated and their qualities compared, so that "Jacquard" and others may know how to proceed. No. 1. Some machines drive the shuttle by a crank, others by a camwith a pause. The form of cam depends on the other parts of the machines. 2. Buy a shuttle the size you wish. The shell is stamped to shape, and the ends brazed in. 3. The stroke is longer than shuttle from

SIR,-The best system of shorthand is, I believe, Mr. Pitman's (of Bath); it is not hard to learn, and any one with an hour's daily practice, should be able to write at the end of twelvemonths, sixty woids per minute.

SIR,-In answer to "Hermit," p. 255, Pitman's system is decidedly the most popular, and I think the simplest and most comprehensive. At one time I learnt Odell's, but did not somehow think very much of it. It is of course very difficult to say which is preferable from actual experience, as to learn one system thoroughly is not an easy task, while to mix that with others would lead to a glorious confusion. The ease with which Pitman's system is attained speaks well for it. I received from Mr. Pitman two courses of lessons, which, of course, greatly facilitates the acquirement of the art, and can only say I was much pleased with the simplicity upon which the system is based. I would by all means recommend" Hermit" to join a class taken by the above gentleman, when he would see for himself how surprisingly easy it is to learn. It is perhaps scarcely necessary to add that all depends upon the time devoted, and the regularity when practising.

MEDICAL GALVANISM.

SIR, Much as has been written in this valuable journal on electricity, chiefly in relation to experiments, or to the science itself as a recreation, very little has been advanced on galvanism as a medical agent.

This subject appears to me of such vital importance, compared with mauy subjects discussed in your paper, such as electrical bells, magnetic engines, &c., &c., that I think it is high time that the subject of medical galvanism should be better understood, and more frequently discussed than it has yet been.

I have been induced to address you because I believe there is no other journal in this conntry which is better fitted to deal with this branch of electricity than the ENGLISH MECHANIC, both in its practical and theoretical bearings. Some of your correspondents have, I believe, objected to medical subjects being discussed, and so far as physic itself is concerned, I should say that the inquirers themselves are not likely to suffer much in constitution by remaining in ignorance of some of the irrational prescriptions which are often suggested to them. But when a subject like the present falls within the domain of physical science, and when it is remembered that electricity is both an external and an internal remedy, which can alleviate pain and arrest disease, and this, too, in the most rational inexpensive, and simple manner, and when the patient himself may administer the remedy without fear of adulteration or empiricsm, its importance becomes secondary to no other branch of electrical or experimental science, and its generation and application demands the attention of any journal which is competent to deal with the subject, and professing the advancement and well-being of its readers. It is true that electricity as a remedial agent has worked its way but very slowly, but it would not be difficult to show, did space permit, how this has happened. I believe there are still mauy intelligent physicians who regard galvanism in disease as empirical simply, as I take it, because they do not see or understand why or wherefore it, being a thing intangible, and as immaterial as a shadow, should have any effect upon the nervous economy. On the other hand, others have gone so far as to believe this mysterious fluid to be the nervous influence itself. But whatever doctrine is right, it is sufficient for our purpose to know that electricity is a surprising stimulant to the nervous system; and, moreover, that it would appear to have the power of preparing, repairing, and replenishing the shattered telegraph wires of the body wit hpermanent additional energy.

Before I close allow me to state more particularly my object. It is to ask your correspondents to take this subject up. Amongst the many thousands of subscribers to the ENGLISH MECHANIC there will ever be a vast percentage who receive these pages every week, sufferers from some bodily derangement or disease, and who might receive incalculable benefit from a proper application of galvanism. Many, doubtless, are poor and unable to purchase the costly and often worthless apparatus, as sold at the instrument makers. Many do not understand the modus operandi of the same. It would not be necessary to plunge into the theory of the nervous effects of electricity, but to point out the most desirable, easy, cheap, and efficient way of constructing apparatus suitable for medical use. What is wanted, then, are plain drawings and directions with advice as to the proper administration of the current. An ordinary coil, I believe, is not suitable, the objections being

that where there is more than one continued wire the

O. G.

terbalanced? If the experiment suggested be made, current is completed in one, while in the secondary it will be observed that under the blue correction, wire another current is induced which completely de- black letters will appear absolutely blue, whereas in stroys the power as a remedial agent. the other case, the black will remain unimpaired. I Since writing the above I have received so many should also be glad to know what effect over and answers respecting Medical Coil ("Wanted") as per under correction have upon the definition, and whether advertisement in No. 270, that I am more strongly object glasses, in which the extreme red and violet convinced than ever that the apparatus and applica-rays are united, can now be procured, and of whom? tion generally are totally unsuited to the purpose. The chief error seems to be in using intense battery power as though the living economy were to be relieved of pain by additional torture. Most of the coils are primary and secondary wires, and most likely have no guide to the uninitiated as to which is the negatiue and which the positive pole. It is manifest that this latter is of the greatest importance, since in many diseases the current from the positive element should flow with the natural stream through the system, whilst in others the current is reversed.

W. A.

GEOLOGY OF IRELAND.-WHEEL-STONES. SIR,-The deposits of limestone passed over by your correspondent F. Harwood," p. 257, is that known to geologists as the Mountain Limestone, and occurs as the middle group in the Carboniferous system immediately underlying the true coal measures. This formation and the carboniferous slates are widely developed in Ireland, and give to the scenery of that country some of its peculiar and special features. The characteristic fossils of the mountain limestone are corals, and enermites, especially the latter, which very often make up the entire mass of the stone; from this circumstance it is aptly termed "euermital limestone." The enermite, or stone lily," so called from its elegant shape, is an animal, and belongs to the class Radiata; it is, in fact, a star-fish set upon a flexible and It is of marine habitat, and wherever found as fossils indicates the strata to be of marine origin. Until recently the race of Orinoidea were thought to be extinct, and only a dozen kinds are now known to exist, one of the dozen being dredged up by Professor Forbes in Dublin Bay. The separated dises of which the stems of these creatures were composed being naturally perforated, were thus easily strung upon strings and used as rosaries; they were likewise called wheel-stones, and St. Cuthbert's beads, by the English peasantry, St. Cuthbert being credited with their production. Sir Walter Scott refers to this circumstance in Marmion :

LIGHT OF HEAVENLY BODIES. SIR-In a letter addressed to the astronomical readers of the journal in general, H. W. Bishop states that I said "that the light of D'Arrest's comet was to be 0 126." 1 think I may venture to say that I never said anything of the kind. What I said was, pro-jointed stalk. bably, that the intensity of the light of the comet would be represented by that fraction.

The intensity of light of a heavenly body not self1 luminous is proportioned to R and D representing respectively the radius vector and the distance from the earth. At the time mentioned this fraction 1

R2 D2

R2 D2

was equal to 0-126. At the time that the comet became invisible to Maclear, at the Cape of Good Hope, at the last apparition, the intensity was equal to 0190, the probability was therefore that at the date I mentioned, the coinet would be slightly fainter than when lost sight of by Maclear. So far as I know at present, the comet has not been discovered.

THE LATHE.

OMICRON.

in the ENGLISH

SIR, Since the appearance MECHANIC of the description of the Saltaire Lathe, have been troubled with a wish which I have had many a time during the last two or three years; and that is to improve the lathe in my possession, or make a new one; I have been a subscriber from the first number, and have carefully read all the articles on the lathe, but I am undecided on many of the different points of a perfect amateur's lathe. Could Mr. Smith be induced to give us working drawings of an amateurs lathe, drawings to scale, say the gantry, so as to give height from floor, and a section of do., length he would recommend gantry to be, drawings of the two heads, and height of centres, together with the form and diameter of spindle of fast head-in fact, all drawings and dimensions to enable an intelligent workman to construct one, always bearing in mind all to be made so that the other tools, chucks, slides, and the different cutting apparatus belonging to a complete lathe could be added to at the inclination or convenience of the workman; I think it would be a very interesting subject, and one very popular. If the

height of the centres given did not suit every one, they could enlarge or reduce the dimensions to their own. That the subject is of interest I see by the inquiries of No. 3866 and 3867 in this week's number. Some time since we had two or three promises from different parties to give us specimens, &c., which I am would give pleasure to more than myself, and also Mr. Plant promised drawings of his chucks. I am sure they will excuse me reminding them-the reason is, I am anxiously expecting them.

sure

"On a rock by Lindisfarn St. Cuthbert sits and toils to frame The sea-born beads that bear his name."

Н. Н.

THE SOLAR SPECTRUM. SIR,-I am pleased to find so good an authority as J. Norman Lockyer endeavouring to remove my difficulties regarding the origin of the dark lines in the solar spectruma. In returning thanks, may I assure him the evidence afforded by the phenomenon referred to had been duly considered before I ventured to write the letter on p. 114; but I arrived at the conclusion that the want of chemical power in the light of the solar prominences was the cause of some of the lines changing from dark to bright.

I cannot agree with Mr. Proctor in considering Kirchhoff right in ignoring crepuscular evidence. Neither, in my opinion, are the conditions wanting in the upper atmosphere for the chemical combination with oxygen of iron, magnesium, &c. He is, however, undoubtedly correct in considering that employing one'sself about photographic manipulations does not necessarily teach anything concerning the nature of light. That depends upon the character of the operator. He may be an excellent photographer, although a poor philosopher. In dismissing this subject, I wish to add a few words respecting the motive for its introduction. In the hands of the astronomer the spectroscope has fologist at would be equally as useful. I hope this hint In the hands of the ineteoproved of great service. will not be disregarded.

TESTING BOILERS.

T. A.

Query 3850.-" Thermo" may perhaps unite the usercury in his thermometer by giving it a series of sharp jerks. See also other correspondents' answers is "Gitche Manito," some time since.

Query 3875 ("Gratus ").-Bleaching powder is rande by placing lime (moist) in a chamber, upon perforater, shelves, and submitting it to the action of chiance, evolved by the action of hydrochloric acid spoo de black oxide of manganese. Refer to corresponders" answers on the subject in a recent volume.

MANUFACTURE OF OXYGEN (3883.-M. P. C. 87Oxygen may be prepared from manganate of sods heating it to a certain temperature in a retort whits connected with a steam boiler, and a pump whies plies air. The retort containing the manga first heated, and the tap from the steam boiler on, when the following change takes place :(Na, MnO4),+ (H2O) = (NaHO + Mn 0, +", When this part of the operation is over, the steam a The oxygen being liberated, is passed on to the bo ture in the retort for about a quarter of an hour, whe shut off, and superheated air pumped over the it is again ready to undergo the first operation. air must be freed from carbonic acid by passing t through caustic soda solution before being pumped over the spent manganate. The manganate may be made in large quantities by heating to redness a mixture of black oxide of manganese, carbonate nitrate of soda, the heat being continued for som time, in order to decompose the sodium nitrate, what is at first formed.

Query 3887.-THE UTILISATION OF SEWAGE.— tration," by C. E. Austin, Mem. Inst. C.E.; Bela "On the Utilisation of Sewage by Irrigation and Latham's "Inaugural Address," published by p and Baron Liebig's letter on the utilisation of the metropolitan sewage, published by Allnutt There plenty of information on the subject to be found scattered through the Engineer, Building News, and Gardener's Chronicle.

WATER ANALYSIS.-(" Aqua" 3886).—If "A qua " is not accustomed to make analyses of different articles, and water more particularly, he should use Nicholson's process, which is admirably described in the Quarterly Journal of the Chemical Society for Decem ber, 1862. The apparatus required would be 2 burettes, 50 cbc., divided into 500 parts, with an Erdmann's float. The burettes must be provided with a glass stopcock in lieu of the indiarubber tube, and Mohr's clip; several small stoppered flasks, to hold about 100 cbc.; porcelain and glass evaporating basins, a required are:-Standard lime solution: Dissolve 0·172 few beakers, and a litre measuring flask. Solutions grm, of selenite in a litre of water. Soap solution: The sapo mollis of the Pharmacopeia is to be dissolved in a mixture of equal volumes of distilled water and methylated spirit, to be of such a strength that 28 divisions of the burette are required to produce a permanent lather with 50 cbc. of the standard me solution. Barium nitrate solution: 026 grm. in a litre Silver nitrate solution: 85 grms. of distilled water. in a litre of water. Ammoniam oxalate, 0355 grin. in a litre of distilled water. Chameleon solution: Dissolve 0·159 g:m. of potassium permanganate in a litre but for the analytical process I must refer Aqua" to of water. These are the standard solutions required; Nicholson's paper, the December part of the Journal of the Chemical Society for 1862, as it would occupy too much time and space to give it in detail.

VOLUME OF GAS (Query 3937).-" Zeta" can calenlate the volume of gas thus:-11 16 litres of hydrogen weigh 1 gramme; and as the density of nitrous oxide that gas measured at 0°C. and 760mm. would weigh 22 is 22, that is half the molecular weight, 11:16 litres of grammes. Now, as we know that 22 grammes occupy II 16 litres, we can easily find the volume occupied by 200 grammes:11:16 x 200

22

ments be reconciled?

I can

How can the two state

T. S. CONISBEE.

ACHROMATIC OBJECT GLASSES. SIR,-If any of your contributors would kindly afford information upon the following points in connection with achromatic telescope object glasses, it would be highly esteemed. In Brewster's and other works upon optics, the secondary spectrum is described as being of a wine, claret, purple, or lilac colour, on one side, and of a green colour on the other side of the focus. Now, I have had opportunities of examining object glasses by some of our best makers, and the outstanding colours in all of them, were (to my eyes) blue and yellow. Am I to infer from this difference, that the tint of such oustanding colours is chiefly influenced by the colours of the two rays selected for correction, and that the extreme red and violet ones (as mentioned in the works alluded to), are no longer (as a rule) adopted for that purpose; or is such difference attributable to the irrationality of the glass now employed? It has struck me, upon comparing one or two glasses which have come under my notice, giving a dark outstanding colour, resembling the claret, or other colour referred to, with one in the blue state of correction, that the former was incomparably superior in defining fine black lines, which I attributed to the contrast between black and white being much better preserved under the influence of a dark colour, than a pale bright one. The dark colour also appeared to be much less in quantity than the blue, which latter seemed to form a cloud before the object, and a wide fringe around it, while no such obstruction was perceptible or appreciable in the case of the claret or deeper-toned colour. I should like some of your readers to make the experiment upon a white enamelled watch face, at a distance not exceeding thirty or forty yards, in full sunshine, under a high power. Other states of achromatism may, by ANSWERS FROM GEORGE E. DAVIS. uniting more luminous rays, appear, theoretically, to offer an advantage in the shape of increased intensity, SIR, A correspondent, " Another Flautist," requires but is it not probable that a paramount disadvantage the composition of German silver. I offer the followmay accrue from the uncorrected colour being bothing:-ist, copper, 40pts. ; zine, 26, and nickel, 31pts. paler and thicker, or of greater breadth, whereby 2nd, copper, 10pts. ; zinc, 6, and nickel, 4pts. The first the advantage which would otherwise necessarily is a good metal, which takes a high polish, and the follow the increased amount of light, would be coun-second is the white copper of the Chinese.

EXAM.-QUESTION. SIR,-" Zeta's" query (No. 3937) is very simple. The weight of one litre of nitrous oxide at 0C. and 760 metre of mercury is 1-9712 grammes. 200 grammes, then, must measure 101 461 litres, and as one litre equals 61-028 cubic inches, that is equivalent to a volume of 6191 965 cubic inches. He can readily obtain the weight in grammes of one litre of any gas at oC. and 76 metres of mercury, by multiplying '0896 by the atomic weight of the gas, and divide by its volume: as 0896 × 44

CH,

= 101 454 litres at 0°C. and 760mm. WEIGHT OF GAS (3956).-R. Terset can, by following the method here detailed, find the weight of any First, methyl gas is known by the formula (CH3 therefore, the density would be 15. Now, a litre of hydrogen at 0°C. and 760mm. weighs 0-0896 grm.; consequently, a litre of methyl would weigh 1344 grms. at the same temperature and pressure. But the temperature is 20°C., whilst the pressure remains unaltered. A litre at 0°C. would become 10733 at 20°C. by the equation 1+ at or1 + (0003665 × 20). We can now easily get the weight of 1 litre, for we have found that 1.0733 litres of methyl at 20°C. weigh 1344 grammes; what will a litre weigh? By the 1.344 =1252 grms., or the weight of a equation:1.0733 litre of methyl gas 26°C. and 760mm. As regards the second part of the question, how to prepare acetic acid from the substances mentioned, he may prepare it thus:- First slack the lime with water, and boil it with sodium carbonate to form sodium hydrate. This must be obtained in the solid state by evaporation.

NaCO3 + Ca(HO), = (NaHO), + CaCO3. The ethyl iodide is then acted upon by the caustic soda, and the resulting alcohol distilled offC2HI+NaHO C2HO + NaI The alcohol is then heated with sulphuric acid and potassium chromate, when aldehyde is formed:C2HO+ 0 = €2H4 O + H2O and this aldehyde, when fused with caustic soda, forms the sodium salt of the acid, from which salt the acid is liberated by sulphuric acid:

CHO+NaHO = C2H2 NaO2 + H2

and (C,H,NaO2)2 + H2SO4 = (C2H4O4)2 + Ña,SO4 I hope I have made the process plain enough for R. Terset, and shall be most happy to help him on the road to knowledge whenever he chooses to ask. GEORGE E. DAVIS.

FLIGHT.-FIGURE OF 8 WAVE THEORY OF WING MOVEMENTS. SIR, Would you kindly insert the enclosed in your valuable journal; it will, I think, interest a large. number of your readers.

AVIATOR. In the proceedings of the Royal Institution of