way. COMBINED PUNCHING, SHEARING, UPSETTING, AND STRETCHING MACHINE. keep the tire from slipping; there is also a movable an ordinary evil, but as, obviously, this cannot be done COTTON SPINNING. SIR,-As no one has taken the trouble to enlighten "Excelsior," p. 1927, March 4, I will, with your permission, endeavour to do so. He asks for an explanation of the sun and planet wheels, cone, and reversing motion of Higgins's roving frame. The object of the cone, or what is better, cones, is to give to the bobbins a constant circumferential speed, or velocity of periphery, so that they may "lap" up the roving yarn at the same rate as the rollers deliver it, as the diameter of the bobbins is constantly increasing from "empty" to "full." I suppose he will know that the yarn is "lapped" around the bobbins by the "flys;" if so, he will see that if the bobbins "lead" the flys, as they are now generally made to do, their speed of revolution must be retarded in proportion as their diameter is increased, but if they lap it up by "dragging" behind the flys, then their speed must be increased in the same ratio. Now as the cones have their extremes, in proportion to the bobbin, empty and full, I dare say "Excelsior" has wondered what the sun and planet wheels were for, as at first sight it appears that a properly adjusted notion might be given to the bobbins directly from the cones-i.e., by the cones being made to drive the bobbins. and their speed adjusted by a "strap rack." However, a little more consideration, or what will teach a man far more positively, a little experience, will soon show that if the speed of the bobbins be not very exactly and positively adjusted to that of the rollers, the quality of the roving will suffer, on one hand from attenuation, on the other from "lagging" around the fly-top. It was formerly a matter of great difficulty to regulate the speed of the bobbins of the roving frame, as it was done by what was called a "differential rack and friction-plate," the results of the adjustments being generally rather too differential. But this difficulty was at last overcome by the introduction of the "cone, and sun and LOOSE ON DRIVING SHAFT wheel when the bobbins "lap up" by "leading," but when they do so by "dragging," then the direction of the disc is the same as that of the sun wheel, and the result is a subtraction of velocity from the internal wheel, &c. Suppose the rollers "turn out" 3in. of yarn while the spindles make 9 revolutions. If the bobbins be 3in. in circumference it is evident they will require to make 10 revolutions in the same time as the spindles make 9, in order that they may lap up the 3in. of yarn delivered from the rollers. Suppose this to be the condition, then, that is required at the commencement of the "set," and that the "disc wheel gives this one extra turn to the bobbins, either by one revolution of its own, or whatever part of one the arrangement of gears may require. With the cone strap driving at the fastest end of the cone, it will be evident planet wheels," the work-to" Excelsior," if the extremes of the cones, as I said ing and object of which I will now try to before, correspond to those of the bobbin empty and make "Excelsior" understand. He will see that full, that the speed of the bobbin can be regulated with if motion could be given by positive gearing to greatest nicety by causing the strap to move forward a the spindles, bobbins, and rollers from one strap, the proper distance for each layer of yarn that adds to the irregularities of speed from "slipping" would be only diameter of the bobbin, as the real weight of driving the bobbin is given directly by the gears 1, 2, and from the driving shaft, so that the small amount of power required from the cone strap by this arrangement renders it as near a positive in its action as needs be. The reversing motion comes from the same source, it regulates the up and down motion of the "lifter," upon which the bobbins rest, in order that the yarn. may be coiled'upon them in a proper manner-i.e, the coils laid side by side. The changes of direction are given by the bevel wheels 7, the one being thrown out of gear as the other is thrown in, and is brought about: by means of a lever, one end of which is lifted up or pressed down by a slotted fixture attached to the lifter," which is also connected in a suitable manner to the strap rack, so that its fulcrum is brought nearer the end at every change, and by this means it causes the "lifter's" direction to be changed a little earlier for every layer of yarn that goes on the bobbins, and. so gives the required taper to the ends. I hope now that I have given Excelsior" such information as will enable him after a little further inspection of the frame itself, whilst working, to understand that very ingenious device, the sun and planet motion. I have tried to be as plain as I could, so that what I have said may be understood by the numerous young cotton. workers who are readers of our wonderful MECHANIC.. and if it meets with the approbation of our Editor, I will gladly add a "few bricks" to our "institution for the benefit of those who seek such information as I can give, so that factory lads may not have to com-plain of the paucity of matter in the MECHANIC in which they can take an especial interest. With respect to "Excelsior's" last question, I know no such work. I should just like to say in conclusion that I think the space taken up sometimes by "straw splitting," such as that a week or two ago about what a" devil" is or isn't, would be much better filled up by charity, as all the writers were to some extent both. right and wrong, and the mere local name of a machine does not effect its proper working, that I am! aware of. E. SLATER, Burnley. TO MILLERS. SIR,-I will endeavour to review this correspondence. as briefly as possible. Some few weeks ago I forwarded to you, Sir, a diagram of a modification of the universab joint, which is a decided improvement on the old plan, and left it at your option to insert it in the ENGLISH MECHANIC for the benefit of my brother readers, or otherwise consign it to the waste-paper basket. However, it made its appearance in due time, under the somewhat indefinite heading, "Something New for Millers." I have no fault to find with this, though they are not my words, and not what I intended it should be called. The name I gave it was "Universal" Balance Rynd," accompanying which was also forwarded a few words descriptive of its construction. This meets the eye of Mr. Sharpe, who writes to say that he has had the same working in his mill since 1856, and proceeds to give a "vague" description of what now proves to be something else, respecting which. cile those contradictory statements. I wrote for an explanation, and how we were to reconpearance, he is unable to do, but resorts to abuse and misrepresentation. I never said that I was the invertor of the universal joint as such, but of the same as per diagram; and any ordinary intellect would have so understood it. sufficiently clear to him, surely the diagram ought to If the description given was not be. He says that the only part that I can lay claim to is the outward ring. Let me tell him I never said I This, to all ap lid, because I knew perfectly well that it was in use THOS. EVANS. SIR,-In the ENGLISH MECHANIC (No. 264) there are two replies to my letter in No. 262, on Millstone Balancing." Mr. Sharpe supports my opinion; I thank him for his reply. I also thank Mr. Evans for his criticism of my notions." He is the first that has attempted to explain the matter to me. I have asked many millers for their opinion, but till now could get no direct reply. I honestly assure Mr. Evans if I do not see with his eyes, my blindness is the result not of obstinacy, but misfortune-or ignorance, if he think proper so to term it. I try, and have long tried, to take Mr. Evans' view of millstone balancing, but the more I study the subject, and the more experience I get, the more sceptical I become; for I too have ideas-probably very vague ones-of something called gravitation, centrifugal force, &c., and of the unequal distribution of the former over a millstone. I have had considerable experience as a millstone builder, and have new backed, put in fresh burrs, and broken up many a stone; so am slightly acquainted with a millstone's composition, &c. I have seen Mr. Smith's diagram (referred to), but confess I am too unenlightened to understand why, when a millstone's gravitation has been equalised when standing, it should be disturbed when running. It seems to me the faster a stone runs, the greater tendency it should have to equalise its gravitation. Mr. Evans objects to my "notion" that a level bedstone has anything to do with balancing. I acknowledge when giving a running balance it would not matter were the bedstone 45 degrees out of level, or vertical, or away altogether, providing the spindle was held steady and a rest furnished for the chip; but will he say it is not necessary for a standing balance? If it is not, then I am indeed under a delusion, and have been these last 23 years. As to millers looking to the face of the stone for the fault, could he tell, if a stone had a good standing balance, if it had a high side to it? I have had the opportunity in many mills to test my notion," and, as I remarked in my first letter, have invariably found when a stone's standing and running balance did not coincide, that either face, level, irons, or cogs were untrue. Either of the above faults would cause a dragging, or apparent dragging, causing a back-lash, and disturbing the neck. With respect to length of spindle disturbing the neck, as asserted by some of your correspondents, I will offer no opinion, but merely say I have one stone 16in. thick at eye, 14in. at skirt, on "centre irons,' with the pivot 8in. from the face of the stone, and another pair on faulty "universal irons," 13in. at eye. 114in. at skirt, with cups only 2in. from face. Each pair works well. There is but little difference in their speed of grinding and per centage. I suppose Mr. Evans does not pretend to lay claim to the invention of the "universal irons," but their oval form and set screws. His outside ring has been in use some years; so has that described by Mr. Sharpe. With respect to your correspondent "Charles's " balance, good as it might be, I believe it got the inventor of it into trouble, he having been prosecuted for infringing on the rights of Messrs. Clarke and Dunham. I think the above patentees will tell us the "sliding" or "running" balance is their property, and any one using a substitute for theirs is infringing their patent. But to return to my "notion." Until I get more light, I must still run the risk of being thought ignorant and unpractical by holding to the opinion that if the face of a stone be true, the bedstone level, the irons and pitch of cogs correct, a "standing" and "running" balance are the same; and if the above conditions are not observed, they are not the same. A STONEMAN. SIR,-Without doubting Thomas Evans' statement respecting the capabilities of the "patent flour machine" he refers to, perhaps it may not be uninteresting to some of your readers to endeavour to explain the probable cause of the difference of the quantity dressed by it and mine. His machine dressed through 5 sheets of wire, mine only had 3 (the half was seldom used). He took 15ft. of flour out of 20ft. of meal, I only took 124ft. His unchine had 6in. to the foot fall, and therefore had to be driven at 520 revolutions per minute, mine only went at 400, so that when the speed, the power, the length of wire devoted to fine flour, number of wire, and allowance for a little exaggeration taken into consideration, I don't think the modest amount of 6 sacks per hour will appear so insiguificant as at first sight. With reference to the relative advantages of silk v. wire, I should recommend the silk less on account of its superior work than for its saving of flour, wear and tear, and attendance. The power required for a wire machine such as Thos. Evans describes would exceed 4h.p., while the power the silk requires is hardly ob servable. I have improved French flour by dressing A THEORY OF THE CAUSE OF THE TIDES. SIR. According to Newton, it is of the principle of gravitation that two globes placed at a distance from each other, stationary, but free to move, must with an increasing speed move to their common centre of gravity; but if propelled in a direction not in line with their common centre of gravity, they will each revolve round that centre of gravity in a certain period of time. I propose that the earth being about fifty times greater in bulk and density than the moon. their common centre of gravity will be within the mass of the earth, and at a certain distance from its centre; that the earth revolves on this centre of gravity or combined axis in the same period of time as the moon, about twenty-eight days; that the earth, revolving on this combined axis, has an eccentric motion, and that the part of the earth's surface farthest from the moon, and in line with the two centres, is subject to an increase of centrifugal force that the dense matter of the earth, in its revolution on its central axis, is not at liberty to accommodate itself to; that it is otherwise with the air and water; that the waters are raised by this centrifugal force in a ridge or wave on or near the equator, at that point most distant from the moon, which will also be the part of the earth's equator most distant from the combined axis; that this force in excess only extends to a few degrees on either side of the equator; that the open waters outside of these lines towards the poles merely obey the law of the displacement of fluids flowing towards the equator, to temporarily occupy the place of that raised in a ridge or wave on or near the equator by the excess of centrifugal force produced by the eccentric revolution of the earth on its combined axis; so that a lake outside of these lines, or a large bay with its inlet towards the nearest pole, would not be affected by the force that produces the ridge or wave on or near the equator, or the flow that the open waters are subject to, and so would have no tide; that the revolution of the earth on its central axis once in about twenty-four hours will cause every part of its equator to come under the influence of this excess of force produced by its eccentric revolution on its combined axis in that period of time. So that with the moon's attraction in the opposite direction, twenty-four hours, omitting secondary and local inG. H. OGILVY, Birmingham. we have the ebb and flow of the tide twice in about terferences. THE EARTH'S ROTATION. are, to say slow indeed, and quite incapable of any perceptible tendency to cast bodies off by centrifugal force; at least, this is my opinion, and I am open to correction, and shall be only too glad if anyone will kindly show me where my judgment is at fault. I cannot take up any more of your valuable space in discussing the other portions of Mr. Beardsley's letter, relative to the wind, &c., but it appears to me to be -well, never mind. C. R. Q., Hants. coloured.' THE BELTS OF JUPITER. into a long discussion on the above subject, I assure SIR, AS Mr. Grover expresses a wish not to enter him that, I also am quite willing that it should be cut string of misconception, I feel bound again to reply. short as quickly as possible; but as his letter is such a In the first place, Mr. Grover's quotation from my letter as to "delicate gradations," &c., is a mistake when applied to light and shade; I applied that term to colour only. The words I used were, broad masses of light and shade, which are quite different things, and which I believe are affected relatively and proportionally the same with every-sized aperture; but Mr. Grover implies that the reverse of this is abundantly proved by the amount of detail which a large aperreally cannot see how this affects the question of ture reveals when compared with a small aperture. I broad masses of light and shade. As to the professed impossibility of getting pigments suitable to express planetary markings, Mr. G. brings an instance to support his argument, of a lily, which, though really a white flower, had to be painted grey to express shadow. impossibility of getting pigments pure and bright In what way this supports his argument as to the enough I am at a loss to conceive. Such an instance evidently does not touch the point at issue. Again, Mr. Grover says: "Mr. Purkiss thinks I am in error in stating that Mr. Browning's drawing is overfirst, I should have perfectly agreed with him; but he Had Mr. G. said so at Certainly not. did not say so, but remarked that the drawing referred to was too vivid in colour. The term "overcoloured" implies that there is too much colour, or that it is too heavily coloured; whereas vividity implies brilliancy and light. Mr. Grover may perhaps think I am splitsary to prevent misunderstanding. My remarks with ting hairs, but such distinctions are absolutely necesreference to Mr. Denning's letter therefore do not, that I am aware of, offer any contradictions. next paragraph contains a singular misconception. Could Mr. Grover really suppose that I ventured for one moment to compare a painted sunset with a real which I hope I do not possess at present. Truly, Í Such would evidence a degree of insanity spoke of a sky, and I spoke of a landscape, but only as they might exist on canvas, and so could be compared with each other; and it still remains for Mr. Grover to justify his plea for the need of exaggeration by the simile I then used. In the concluding paragraph Mr. Grover descends to personalities, which certainly do not lend any dignity to his preceding remarks. Does he expect me to blow my own trumpet as a draughtsman, or to spout about the performance of my mirrors? However, for the general satisfaction of your readers, some of those gentlemen for whom I am now making specula (thanks to the pages of the MECHANIC) will perhaps shortly be prepared to let you know the merits or demerits of my work, which they have my free permission to do; and then Mr. Grover can judge for himself. W. PURKISS. sunset? The THE REPUTED FIGURE AND MOTIONS OF SIR, With your kind permission I will make one or above subject, signed by John Beardsley, two remarks on a letter appearing on p. 89, on the Now although I can lay claim to no scientific attainments, yet my own common sens seems to me to detect some very fallacious reasoning on the part of the writer of the letter referred to, if I am correct in presuming that Mr. Beardsley makes centrifugal force a basis for disputing the fact of the earth's revolution on its axis. In the first place, I beg to submit that Mr. Beardsley's ideas of "cen trifugal force" the least of it, very vague; he appears to think that objects on the earth's equator, because they have a surface speed of 17 miles or so, per minute, must, therefore, have a tremendous tendency to fly off. Now with all due deference to the "godfather," I think the very term "centrifugal" is calculated to mislead, for this reason-an object projected from a surface in rapid rotation, does not pursue a direction of flight directly in a line with the centre of the body from which it has taken its departure. flight, if produced backwards, as it were, would, I On the contrary, the line of imagine, be found to be a tangent touching the cirdirection merely in obedience to the law of nature, cumference of the rotating mass, and it takes this that bodies set in motion in any given direction endeavour to continue their motion in that same direction. Now my idea with regard to objects on the equator is this (and I'invite anyone to administer to me the objects-pursuing a surface speed of 17 miles a a good hearty whack if I am talking nonsense), that they If our author will take his seat outside a railway minute, have no more tendency to fly off from centri- carriage, on an express train proceeding at a speed of fugal force than would little iron filings on the surface 60 miles per hour, he will find he is more exposed than of a globe of magnetised iron, say 8ft. diameter, revolv-is desirable, and he will then be able to form some ing on its axis once in 24 hours. The magnetism is of idea of the sensation he would experience if whirled course to represent gravity; this globe would have a through space at a speed 17 times as fast. On the surface speed at its equator of about 1ft. per hour, other hand, if the air carried with us is meant the which may be taken to represent the 1000 miles air inside the carriage only, where is the comparison? In the one case we are exposed outside a rotating traversed by a point on our earth's equator; the are of sphere, in the other boxed up in a carriage. Now the 24th of a circle, when drawn on paper, looks like a very slight deviation from a straight line; it is just as slight a deviation in the case of the earth, and does Mr. Beardsley mean to say that a body would have any perceptible tendency to fly off from "centrifugal force" when, after an hour's flight, it had only departed from a straight line by so small a curve as this are represents? I will bring forward another case for Mr. Beardsley's consideration. Conceive a huge locomotive, with driving wheels 100ft. diameter, cylinders, boiler, and gauge of rails to match-fancy this monster tearing along due north and south (I mention this direction that it may not interfere with the earth's motion) on a line of rails laid, say 6ft, above sea level all the way from pole to pole, rushing along at a speed of 1000 miles an hour, does Mr. Beardsley for a moment think that such a speed would cause the engine to launch itself into space from centrifugal force? I can scarcely think he would form such an opinion; and yet this engine would be travelling over the same curve, pursuing a precisely similar line of flight, at precisely the same speed as objects at rest on our equator; in fact, the earth's revolution is only comparatively rapid because we (little insignificant atoms) are not accustomed to view in our everyday life movements on such a gigantic scale, but looking at the earth simply as a globe, its motion reality very the circle described would be identical in each case. Also if he will put water on to a flywheel, connected with any piece of machinery in motion, indoors, and under the same conditions as if inside a railway carriage, he will find the water thrown off in proportion to the size and speed of the wheel, which proves the assertion to be entirely unfounded in fact. Again, if there is any such thing as a truly vertical position for objects on the earth's surface, how is it that if the earth is globular that such a thing as a vertical line is to be found everywhere, as we approach the poles, and also at the equator? The answer, I am aware, is dependent upon the theory of gravity, as producing vertical lines as straight ones, pointing to the centre of the earth, and that force is required to divert the motion of anything from such line. But what proof have we that a really vertical line has no existence? I am not aware of a single argument in proof of this, except that of necessity (gravity), for if a plumb line be let fall at the equator, and the true vertical line points to the centre of the earth, would it not require a greater force to form a correct and straight line at one portion of the 24 hours (it takes to form this rotation) than at the other portion of the same 24 hours? Astronomers agree as to the existence of a zenith, "Astronomy without Mathematics," page 27. or place directly overhead; or, in other words, a true perpendicular. This zenith, or perpendicular, from the centre of the earth, they give, as at a point to the left of the North Pole, as it would be shown in a diagram. Now, from this we conclude, that by a universal law there must be a correct horizontal to all perpendiculars, and which are at exactly right angles the one to the other-and it is also an established fact, that all bodies, or everything that has weight, and is unobstructed, has a tendency to fall in a straight line downwards from its point of suspension, if not influenced by attraction or force. I am aware that weight has been, and is generally described as the "measure of force," but to this definition I object, as it depends solely for proof on the theory of gravitative attraction; a theory (so far as I know) which has not a single argument (confirmed by positive fact) for its support. The true vertical line is said to be from the point of suspension c, or in a straight line for the centre, as in the annexed diagram (or ) that the earth's rotation causes any body let fall at A to fall somewhat towards D, to the said centre, and the experiments of Dr. Hook, Gugliemini, and of Benzenberg, and with all the care which the last-named philosopher brought to bear, he found a deviation in his experiments on falling bodies, towards all four points of the compass, so that he had to be satisfied with a "balance of deviation," a term, and a fact, which plainly shows that some other principle than the earth's rotation had control over these balls through 235ft. of vertical space. upon invariably appears widest. A railway servant 20 1' 45 west (= 8m. 78. of S. T.) And his calcucan testify to the changeable appearance of each line lation, slightly condensed, is as follows: of rails. A town street assumes the same appearance, Although this principle will be more fully dealt with It has commonly been held that the earth is speeding round the sun with inconceivable velocity, and that the appearance of a rising and setting sun could not be accounted for in any other way than by the rotation of the earth about its axis. We will suppose A B to be a plain on the earth's surface, and M the moon, and sss the rising sun at Now we will put aside as much as possible the apparently different altitudes, and we will suppose, for mathematical terms which are puzzling to some the sake of easy illustration, that the observer stands readers, and show that this speed of 17 miles per at A, and that s and M are at equal angles to the right minute, which the surface of the earth performs and left, and supposing sss and M are at equal during its rotation, being close upon 1500ft. in one height, the question arises, would the sun s' appear as second of time, is simply incredible; because when we shown in the diagram, before the vanishing point is find that a body falling from a position of rest falls marked? 1 contend that it would, for the simple through 16ft. in one second of time, this "balance of reason that the visional illusion, called in all engideviation" of a few lines to the east, is more incredi-neering works "curvature" (but which is neither more ble still; for if we divide the height of the tower nor less than optical deception), accounts for it. (25ft.) by rule, we shall find that the ball would ocThere is in all sights a vanishing point, or a concupy nearly 4 seconds in falling, and, consequently, verging of the rays to a point at various distances, that the earth should have passed in that time for the space of 5000 to 6000ft. from the true vertical, past vanishing point of a person stationed at A. and we will suppose D in the above figure to be the towards the east. So that it is not a question of lines, point, then, will be the observer's horizon, because of but of thousands of feet It may be said that the the converging of the bottom and top rays to a point speed at which the earth rotates will cause the ball to at D, and fixes the object above the horizon, at an apbe carried with it to a great extent, reducing the parently less altitude than it is in reality, and if we difference of distance traversed during the 4 seconds. But if this rotation is a fact, and this forward force carry a straight line from D to s we shall witness a applicable to the falling ball, why does it not bound rising sun, and vice versa a setting sun. onwards in the same direction as the rotation, the same as any body will do let fall from a railway train? The question of the body's falling down a mine, for such a depth, under such circumstances, is simply absurd. I come now to consider the diurnal motion of the sun, as a proof of the spherical figure of the earth. I might easily set out by giving a few diagrams, proving that the earth is a vast plain. I do not advance this assertion as true. I do not argue that the earth is a vast irregular surface, behind which the sun rises and sets. What I have to say is, that the apparently convex surface of our world is not owing to any real convexity of the surface, but to optical illusion, or the principle of vision, combined with the refraction of the atmosphere; indeed, these two principles are the foundation of all our errors as to parallax, measure, and distance, the first and fundamental error upon which a host of others have been grafted. This I will take the table of curvature as it stands in h. m. 8. 1 33 46-06 0 0 133 1 33 47:39 Then, from the given local S. T. 6 14 50:39 .. G. M. T. required.. Now here "F.R.A.S." has adopted a method formerly practised by myself, but condemned as erroneous by authorities no less eminent than Mr. Baxendell, and the late Mr. Dawes. In No. 35 of the "Astronomier Register," Aug. 1855 (Vol. III., pp. 191, 208), are letters from those gentlemen in reply to one from mysel signed "Aicitinens ": and in that from Mr. Dawes an example in given which is transposed, as follows, into the case in question. Mean interval since G. M. N... 4 48 23-96 or, G. M. T. required It will be observed that the two answers to the question differ by 133., the connection applied by "F.R.A.S. " (in accordance with what certainly seen to be the directious of the "Nautical Almanac"), to the S. T. at G. M. N. If the 8m. 78. finally added by "F.R.AS." were allowed to stand for Sidereal time, the same result would be obtained as is found by Mr. Dawes' method; but of course sidereal and mean time cannot be added together. Is the Nautical AlG. M. T. at the time and place proposed. fl. 48m. 22 63s. manac "Explanation" right or wrong: and is the or 4h. 48m. 23-DGs. ? NOT A F.R.A.S. PARABOLISING SPECULA. SIR,-I did not anticipate that the difficulty expressed by "Novice" was of so simple a nature, or I would willingly have answered his question before: but now such answer is, I suppose, superfluous, if Mr. Blacklock's explanation met his difficulty. It is, of course, easy to see that if we have a spherical mirror whose central rays meet, say, in a focus of 6 inches, while its marginal rays meet in a focus of 597 inches, it is just as practicable to make the centre of the mirror more hollow, so as to give a focus gin. shorter, as it would be to flatten the margin, and so lengthen the outer rays to suit the central; it simply reverses the order of procedure, the only difference in result being that when the centre is depressed, the focus of the mirror would be a trifle shorter than if corrected by the other method. W. PURKISS. Baker's Land and Engineering Surveying," and by (To be continued.) [We admit we owe an apology to many of our nightly in lectures, as we said last week in our "Notices I have adopted Herschel's curves for glase of this description to the foci required by "Neptune," and I find the radii of the curves of his crown lens must be for the outer surface 137-50in., and for the inner 62:51in., both faces of the lens to be convex; of the flint, the inner surface 60-21in., concave, and the outer surface 280 87in,, convex. These curves will give a correct result only for glass whose refractive indices are 1:524, requires-viz., 6ft. 10in. for the crown, 10ft. lin. for the flint, and 18ft. 3in. for the focus of the telescope. Of course if the indices of "Neptune's" glass are not as above, he will not get a perfect correction for colour. If he finds this to be the case, when his object-glass is in a sufficiently forward state to be tested, he can produce the required correction by altering the curves slightly. I think he will find in practice that he needs Only to alter either the outer surface of the crown or the inner surface of the flint. He may by this means arrive at a perfect correction. Now, as to the proof that the earth really moves, the simple fact that a small rotating semicircle may be made to keep pace with the sun, and to cast a uniform shadow, is no proof at all. It of course is altered and moved, until the different parts are adjusted, so as to show their exact relation and position one to another, and then the principle is said to be complete by way of illustration, whereas the construction, and the position intended to be illustrated, may be as foreign to each other as possible. In proof of if similar arguments and illustrations were not used and 1:585, and will then produce foci such as "Neptune " this I may say that Mr. Proctor admits (ENGLISH MECHANIC, Vol x, p. 598) the system of Tycho Brahe may be illustrated just as easily. This being so, surely shall not be called upon to enlarge much upon this part of the subject. We will then at once proceed to inquire into the principles which actually exists, and which may throw some light upon the cause of light and darkness, and illustrate the subject in hand. Mr. Hampden' has offered to stake £500 on the proof of the convexity of a river, a canal, &c., and which you notice in your preBent volume, pages 70 and 95. I can regard this matter in no other light than as truly extraordinary that man should be so wedded to system, as to be blind ts proof they witness nearly every day of their lives. I hope I shall be able to prove that the apparent greater height of an object, in the centre of 6 miles of water, than objects at either end of this distance, is not owing at all to convexity, but to an entirely different principle in nature, but which principle does not appear to be universal. It seems almost incredible that philosophers will not call things by their right names. If they had said visual illusion so much, whether it be by refraction or otherwise, I could have understood them. Any ploughboy can testify to the changeable appearance in width of the land he has marked out, and not quite finished (if the same is of equal width throughout. When he is at the end A, Fig. 2, the part unfinished, apFears as in the figure at B, and when he is at B the end A appears narrowest, and so on; the end he stands * Mr. Proctor, in ENGLISH MECHANIC, Vol. X page 144. TIME. acknowledgment of the reply which Where longitude is expressed in time, I have The example which "F.R.A.S." has been good enough to give, should therefore be read thus :-Required the G. M. T. corresponding to 6h. 14m. 50-39s. local S. T., on 15 April at a place whose longitude is POWERS OF SUBSTANCES TO RESIST THE SIR, I thank Mr. Russell for his letter relating to this question. What I wanted more particularly to direct attention to was the powers of substances to resist the passage of the spark. For instance, if the interior tube of an induction coil be formed of gutta percha, shellac, glass, or ebonite, what would be the relative thickness required in each case depending on the power to resist perforation. It is evident that in this case an air space would not offer so much resistance as the above-named substances. Perhaps shows this to be apparently useless, as the extreme rays of the pencil evidently do not enter the eye at all. I should be glad to see this matter criticised, as many matters of this kind are ventilated through your journal. A B object glass, a b pupil, cdab2:1, available aperture = ed. S. T. PRESTON. PS.-Taking 'the extreme diameter of the pupil at Jin., the above considerations show that for a power of two diameters any aperture of object glass above in. is of no advantage. Hence the uselessness of object glasses of large diameter for opera glasses. COTTON SPINNING. SIR, I am glad that my letter on p. 59 has succeeded in opening the subject of cotton spinning, and if we can only enlist a few more correspondents, I have no doubt much information may be obtained by an exchange of views through the MECHANIC. I shall be glad if" B. W. R., r any one else will give their opinion on the following point-viz., 'Suppose a drawing frame to have 4 lines of rollers, with a total draught of 7, what draught ought there to be between the 1st and 2nd, 2nd and 3rd, and 3rd and 4th rollers? "Mutual Improvement's" rule for ascertaining the draught of a carding engine is correct, though it appears as if his callenders" took up" took quickly FACTORY LAD. Referring to the letter of "F.R.A.S." on "personal" matters, on page 86 of the ENGLISH MECHANIC, 15th April, 1870, he says "Veritas" has been "preaching" from that text "Venus on the Sun's Face," as given in Vol. X., No. 247. Well, I admit the soft impeachment, without, apparently, obtaining many converts, but to change the metaphor, I considered the production of a "F.R.A.S." a fair subject of criticism, especially as the data ere so circumstantially given, as 277: 723 7000: 18271 miles," &c. But he adds, "None of these figures are precisely correct, because we have never gone beyond one place of decimals." I do not, nor never did, hold" F.R.A.S." to a "rigid accuracy in figures;" but I do hold that the eccen tricity of the orbit of the earth, as given by Sir J. Herschel at 0.01679, as measured by unity, the mean distance ought to be a guide, to which, when unity is added, equals 101679, this is the ratio between the mean and aphelion distance, and also the mean distance divided by the perihelion distance. "To have gone into all the details and refinements of calculation," and thereby deduced or obtained the correct mean diameter and distance of the Sun, would have been considered ample satisfaction by VERITAS. FUSES FOR CONCUSSION SHELLS. SIR,-I beg to send sketches of fuses for concussion shells, which I have invented. The sketches above show the fuses as fixed in shells. The number of holes for the escape of flame may be increased either vertically or laterally. J Common fuze composition. M = quick match. AB Sections of plugs of lead or other metal. In Fig. 1 the plugs are retained in their places by a thin wire A B of fusible metal, which is destroyed when the gun is fired, and the plugs are set free to tumble outwards when the shell strikes the ground. In Fig. 2 the plugs tumble inwards as soon as the plug of cardboard or papier mache D is removed. In order to effect the displacement of D, it is filled with rifle powder P, and becomes blown out when the gun is fired. These fuses are not similar to Freeburn's, or any fuse that has been invented prior to 1852. OLIVER HALDANE STOKES. BACK-WHEEL BICYCLE. SIR,-It may be only practice. Mr. Preston (2463) wants to ride the " back-wheel" bicycle he has made. The pressure on the treadles being of a different nature to that of the ordinary machine, requires to be learnt afresh, even though he may ride them. He ought to have 6 cranks, though, for a 38" wheel (ordinary bicycles require 64" for a 36" wheel); the wheels are only 6 apart, not a foot, and if he has got a roller! advise him to take it off. The swinging bars are of such a length as to make the treadles about 1ft. Gin. below the level of the spring, when they are at their lowest point, this suits most persons, but as they can easily be lengthened or shortened, it is best to adjust them till you get the size you find it comfortable. The swing bars are made of the shape shown in the sketch. Leg rests can be put on to the projection in front, these do not interfere with the working. Persevere with it, and you will soon "make it go" fast enough. On the 2nd of April, I travelled on mine from Hampstead to Hendon, 3 miles in 15 minutes, with great ease. I have reason to believe it to be the easiest working velocipede I have yet heard of. Certainly the "lever" principle is the best driving action. S. JAMES, Kentish Town-road. MOISTENING LABELS. SIR, Some time ago observed a query in our MECHANIC in reference to moistening labels and postage stamps, without being subjected to the-not always either pleasant or safe operation of passing them through the mouth. The best reply I can make, is to forward for your kind acceptance a neat litte apparatus, that most efficiently (I think) accomplishes the object in view, without the drawback of clumsiness that attaches to so many of the contrivextant lately brought out by Messrs. Savage and Son, Brighton. If you think genious and natty device worth an illustration in ances this in your columns-so devoted to original ideas-it is at your service. They are made in several sizes, to suit the various forms of label in use. The one I send is, you will observe, nearly square, and intended chiefly for wetting postage stamps; the modus operandi is as follows. Pour a little water upou the pad, so as thoroughly to saturate it; place the label with the adhesive side upon the pad, then press down the lid with the fingers; the brass spiral spring inside the box-which constitutes the chief merit of the invention-will raise the cover again when relieved from pressure, when the label or stamp may be removed and applied in the ordinary way. EDMUND M. T. TYDEMAN, Brighton. A B DRAUGHT IN A CARDING ENGINE. SIR,-"Mutual Improvement" asks if the rule be gives, p. 111, for the draught in a carding engine "is strictly correct." If he means for the whole of the draught in the engine, I answer, No! The rule is correct so far as it goes, but it only gives the draught between the doffer and the feed roliers; to get at the whole draught we must take into account also, the draught between feed rollers and lap roller, and also between doffer and call enders. The draught of a carding engine, or any other machine, is simply the ratio between the surface speeds of the first, or taking-in roller, and the last, or delivering-roHer. If the surface speed of first roller be always taken as equal to 1, then the surface speed of last roller will be always the ratio of their speeds, which ratio is the whole draught in the machine. B. W., Rochdale. COMBINED FUNNEL AND MEASURE. SIR,-Enclosed I send you a sketch of a funnel and measure combined, which I made some time ago, and which answers the purpose first-rate for all kinds of liquors, and which I think will be useful to many of your readers. I made them in different sizes, and got them stamped. SEACOMBE. CHEMICAL. SIR, Whilst reading an old book several years age, I met with the following, which I wish to lay before your chemical readers:-"Sow some cress-seed in Hour of sulphur, watering it with distilled water, in order to prevent the introduction of any foreign element. The seeds germinate, and push forth into a centre, nourished alone by principles known by analysis, Cut the stem into several pieces, so that you may have sufficient quantity to operate upon, and by burning it you may obtain some heaps of ashes. In analysing these ashes you will find acid of silica and of alumine, of phosphate and carbonate of lime, of potassium and oxide of iron-as if the cress had wandered or come from the sea-shore. Now, these substances exist neither in the sulphur which served as soil for the plant, nor in the water that was used; we can only explain their presence by supposing some element common to the bodies contained in the cress, and in those which surrounded it. Thus, the air, the distilled water, the flour of sulphur, and the substances contained in the cress-that is, potassa, magnesis, and alumine-have one common principle. From this irrefrigable experiment we deduce the existence of the absolute-a substance common to all natures, modified by a simple force." The idea contained in the above, which is, as I understand it, that all bodies are formed of precisely the same substance, only modified variously by some force or agent, is certainly a grand one. But I wish to ask our chemical friends if the result of the experiment is actually as above stated, and if so, what is the modern explanation? A. J. SMART. THE SUPPOSED PLANET VULCAN. SIR,-The observations of the sun, made with the view to rediscover the above planet in transit, concluded on April 10, and the observers agree in stating that during the time they have watched the solar disc no planetary body has been visible. The spots (macule) have continued to be exceedingly large and numerous, and have presented some very interesting appearances. The larger group, which appeared on the E.N.E. edge, on the 4th st., and to which I called the attention of your readers in my last letter, continued to be visible until the 16th. It was seen by many observers without telescopic aid, and I have numerous sketches of its appearance when examined with a high magnifying power. I enclose two, made by Mr. J. W. Backhouse, of Sunderland, with a 4in. refracting telescope. Mr. Backhouse also obtained some measures of the size of the penumbra, and found that on the 6th April, at 4h. 20m., it was 83,000 miles long, and 64,000 miles wide. Its umbra were, however, small in proportion, the largest being but 13,000 miles long. On the 8th, the penumbra was reduced to 67,000 miles in length, and 48,000 miles in width. On the 14th, at 3h. 20m., its greatest length was 58,000 miles, and its greatest width 36,000 miles. On the 15th, at 21h. 15m, the length of the penumbra was 60,000 miles. In addition to the immense cluster referred to above, numerous others were visible on various parts of the disc, and the following are the numbers noticed by Mr. J. G. E. Elger, on several days:No. of Groups. March 20 No, of 10 April 9 11 of a wheel of similar construction, in use (as a gig I must also in all fairness add that I have never In reply to "Over Sixty," page 115. I very much Mr. Elger, in referring to the large spot visible on the 7th, says, "The most rapid changes were remarked in the long straggling umbræ of this spot. There were evident traces of cyclonic action going on, shown by the spiral streaks, and markings within the penumbra. I have been in the habit, during the last ten NINETY MILES A DAY ON A BICYCLE. years, of constantly observing large solar spots, but I SIR, I have rested contented with reading only never witnessed such a changeable group before." the opinions, suggestions, and experiences of your Mr. W. R. Birt, F.R.A.S., in speaking of a small numerous correspondents on the construction, use, group visible on the 6th, says:-" April 7. This and progress of the velocipede, and have been very group has become enlarged still more, assuming the much interested with the ingenuity exhibited by some, character of two other conspicuous clusters, one in the surprised at the wonders told by others, and amused S. the other in the N. hemisphere, consisting of two at the ridiculous nonsense of that class of your corspots, one preceding and the other following the cen- respondents who are endeavouring to show how to tral portion, or apparent focus of disturbance; a fea- gain power and speed by the various magic contriture which I constantly noticed in my sun spot observa-vances of long levers, cranks, &c. It is, however, usetions, nine or ten years ago. The group in question, less dilating further on these absurdities. I saw an of which I noticed the earliest formation, has now account in your valuable paper of April 9, 1869, of become extended by appendages of spots, N. of the some gentlemen going from Liverpool to London in two terminal ones." four days. This then appeared to me a great feat, and I considered the riders had done four days' hard work, as my notion of the velocipede has differed very much from many of my friends, for I have always held that it is the rider who takes the machine with him, and Mr. Birt also says:-" Between March 29 and April 7, the spots, which have been very numerous, may be divided into two classes, large isolated spots, or pairs of such spots, attended with comparatively small penumbra, and preserving from day to day their distinguishing characteristics; also large groups of insignificant proportions, containing numerous umbræ, and a large extent of penumbra, the disposition of which has altered from day to day." Throughout nearly the entire period selected for the observations, the weather was very fine, but definition was not good, and it was frequently found impossible to obtain good views of the spots, when employing high magnifying powers. In a future series of obser vations, it is proposed to obtain the co-operation of observers at more distant stations. THE "PHANTOM."-" OVER SIXTY." SIR-In further reference to the "Phantom" wheel, I have just had my attention called to an article under the heading "Wheel," in the "Penny Encyclopedia,' whereby it appears that so early as 1838, wheels for railway trucks were constructed upon the "suspensory" principle, and though immensely strong, were not found sufficiently elastic to answer the purposes of good carriage wheels. I also remember, within the last twelvemonth, to have seen, either in the ENGLISH MECHANIC, or some other scientific journal, a notice not the machine the rider. This opinion was very nicely explained by your Extract from Birmingham Gazette, April 16, 1870 :- day among dyers, &c. Naturalists ascertained it to be the female of a hemipterous insect. It was found by the Spaniards in 1518, on their first entry into Mexico, where it was being used by the natives to colour ornaments, &c., &c., and is now extensively cultivated there, in Teneriffe, and Algiers. A Spanish priest introduced it into Teneriffe in 1826. In 1840 M. Simounet, a Frenchman (evading the Spanish law, which threatened any one found exporting the insect from their dominions with death), introduced it into Algiers, thereby rendering a great service to his country; for France was paying 9 or 10 millions of francs annually for the cochineals she used. Fig. 1 represents the nopal plant, one of those peculiar succulent shrubs belonging to the natural order Cacte, called by botanists Opuntia Coccinillifera. "On this the impregnated females are placed. Young ones are shortly developed, and about three or four months afterwards, when the females have become fecundated and enlarged, the harvest commences The insects are removed and killed, either by immersing in hot water or by the heat of a stove." They are served for breeding the following year. collected three times in the year, a few being pre The male only is supplied with wings; the female has none (Figs. 2 and 3, and remains always attached to the leaf of the nopal. They are small, irregular, water and the addition of a precipitant, such as H. E. GODFREY. THE DETERMINATION OF THE PERCENTAGE OF SULPHUR IN IRONS. SIR,-As this subject is of great importance to those connected with the metallurgy of iron, I shall feel obliged if you will allow me space for a few words on the process described under this heading by Mr. Hamilton in your paper of the 8th inst. The method of separating the sulphur from the iron as sulphuretted hydrogen gas, which is absorbed by the solution of potash, and the oxidation of the sulphide of potassium thus produced, by passing chlorine gas into the alkaline iiquid, as suggested by Mr. Hamilton, is ingenious; but the process is objectionable for several reasons, which I think will prevent its coming into general use. 1st. It requires great care in the preparation of the apparatus, and strict attention during the evolution of the gas. 2nd. The unpleasant odours, |
