effect and much of the power of the instrument were lost. The delightful swell by the touch was also considerably impaired. The violinist knows well the value of a tight bow to produce staccato effect, swell, and power. Secondly, I purpose placing, by means of pedals, eighteen of the bass notes under the power of the feet, as well as of the fingers, and thus, sounds will be produced from the thick double bass strings much louder than could possibly be drawn out by the strength of the poor little finger of the left hand; much louder, too, than the double bass instrument itself yields, because its tones are broken at every return of the bow, while the tones of the Claviole are continuous. From these two circumstances it may reasonably be expected that the instrument will have its power doubled, and will therefore be equal to thirty instruments in a band, it having been estimated at fifteen formerly. The fundamental and essential part of the Claviole is the ring-bow, consisting in fact of ninety-five little violin bows intersecting each other, forming a regular polygon of ninety-five sides, which is in effect a cylindrical surface of elastic horsehair, the passage of the angle over the string not being in the least degree perceptible. An engraved segment of the Claviole-bow is given in the preceding page; a is the ring; b the horsehair stretched in equal arcs of the circle, and intersecting each other. The ring-bow is supported on three wheels in a horizontal position, and the strings are stretched vertically between two of the wheels, as close as possible to the horse hair, without touching it. The finger-keys act, through the medium of levers and cranks, on the strings, to pull them against the revolving horsehair, and the tone produced is soft or loud in proportion to the depth to which the finger-keys are pressed down; thus a delightful swell is produced by the touch alone, the effect of which is much superior to any other mode of obtaining a swell, since each individual note is swelled independent of the rest. There are four such ring-bows in the Claviole, one for the double-bass, having sixteen strings belonging to it; a second ring-bow for the bass, having eighteen strings; a third for the tenor, having seventeen strings; and a fourth for the treble, having seventeen strings. The double-bass bow revolves slowly and has a great quantity of hair; the bass-bow turns quicker and has less hair, the tenor-bow still quicker, with still less hair, and the treble-bow moves very quickly and has but a small quantity of hair. And thus the respective speeds of the bows and quantities of hair approximate, in some degree, to the number of the vibrations of the strings, so as to produce power in the bass, and clearness and sweetness in the middle and upper notes. The effect of the atmosphere to put the instrument out of tune by relaxing, and contracting the gut-strings, is counteracted by a long spiral spring attached to each string, which spring moves through a considerable space without sensibly varying in strength; the strings are therefore kept at a uniform tension, practically speaking, and the instrument keeps in tune for years, and, when strung with the best Roman strings, the breakage of a string rarely occurs. It is a curious fact that numbers of pianoforte makers, organ-builders and others, have, since my patent expired in the year 1814, attempted to make sustaining stringed instruments with the view of producing the effects of the Claviole at a cheaper rate; but they have erred in endeavouring to find a substitute for the ring-bow, which is the essence of the invention, and which, with the machinery necessary to turn it and to bring the strings in contact with the horsehair, is necessarily very expensive, because requiring great excellence of workmanship to make the bows revolve in silence. I think the finding of such a substitute, however, as will give the perfect violin tones, a hopeless case, and therefore the Claviole never can be a low-priced instrument; probably 200 guineas is the least sum it can be sold at, to afford reasonable profits to the maker and vendor. Nevertheless I am decidedly of opinion that, when I shall have departed this life, the Claviole will become the sovereign of musical instruments, super seding even the organ itself; the swell by touch, affording a power of expression in the Claviole, to which the organ makes no approach. As I was £5000 out of pocket by the invention thirty-eight years ago, which MILLAR OF DALSWINTON'S EXPERIMENTS IN NAVAL ARCHITECTURE. 131 sum, at compound interest, would at the present time exceed £20,000, I may fairly consider the Claviole as now owing me this latter sum. But as I do not intend making any more of the instruments, yet wish to recover a small portion of my great expenditure, I contemplate travelling with the Claviole through Europe and America, exhibiting it to the public at concerts, and giving lessons on its construction to musical instrument makers and others who may wish to manufacture them, and are willing to pay me for the results of my long experience. Thus I may realize, in advance, some portion of the posthumous profits which will be made by multitudes of manufacturers of the next generation, and be the means of saving them immense sums, which would otherwise be spent in experiments, were they to go to work without my instructions. I am, Sir, yours truly, 26, Judd-place, New-road. EMPLOYMENT OF THE ELECTRIC LIGHT IN COAL MINES. Sir,-Permit me to suggest the propriety of employing the electric light in coal mines, as a substitute for the ineffective glimmer of the safety-lamp. This light requires no support from the atmosphere. It can be completely isolated by means of glass globes. And it can be let off or on, almost at a wish, without having recourse to any combustible body for the purpose. The electric light is simple, cheap, effective, and may be placed wholly beyond the control of the ignorant careless miner. The means of realizing this light are well known, and need no enunciation here. They are as practicable in coal mines as elsewhere. Lights could be multiplied at pleasure in the galleries of the mines, and the light reflected where desired, by means of metal or glass specula, on any given distant point of working. It strikes me that the introduction of the electric light into coal mines, is abundantly practicable; and if practicable, infinitely desirable, as tending to prevent those disastrous explosions and consequent loss of life, which science hitherto has been unable to avert. I am Sir, your obedient servant, Belfast, July 16th, 1845. MR. MILLAR OF DALSWINTON'S EXPE RIMENTS IN NAVAL ARCHITECTURE. Sir,-The perusal of the very just re-, marks in a recent Number of your Journal on the subject of the claims of William Symington, to be the first practical introducer of steam navigation into this country, and of the attempt made by some of the descendants of the late Mr. Millar of Dalswinton, to transfer the honour to that gentleman, (he does not appear to have ever himself advanced any pretensions of the sort,) has recalled to my recollection a passage in "Macpherson's Annals of Commerce," touching Mr. Millar's experiments in naval architecture, which you may, perhaps, think it worth while to re-publish. It may serve to show, that, however public-spirited and enterprizing Mr. Millar may have been, he was but a poor mechanician, and by no means the sort of man likely to have solved so difficult a practical problem as that of applying steam power to navigation. I send you also the article in the Gentleman's Magazine referred to by Macpherson, with a tracing of the engraving. I am, Sir, your constant reader, Birmingham, May 2, 1845. P. Extract from Macpherson's Annals of Commerce, vol. iv. p. 178. "About this time a number of new experiments were made upon the materials and the construction of vessels, both for inland and ocean navigation. In the preceding year Mr. Wilkinson, the proprietor of a very extensive iron work, constructed a barge, for the Birmingham canal navigation, of 70 feet long and 6 feet 8 inches wide, of iron plates, which could swim in 8 or 9 inches of water, and carry thirty-two tons of goods, and this year a similar barge was constructed at Shrewsbury. A vessel with a bottom entirely of copper, without any plank, was built last year, and another of the same metal in the year 1789. At Leith a vessel was built with two bottoms, or rather two very narrow vessels were joined together by the beams of the lower and upper decks. She had five masts and was furnished with five wheels, under the lower deck and between the two bottoms, which were intended to make way in a calm, or against the wind; and it was expected, that the double hold she had of the water would enable her to carry an extraordinary quantity of canvass with very little heeling. But in a passage which she made to Petersburg, the two bottoms were found to act as levers against each other, not merely in keeping her stiff (or upright) but also in straining the whole frame, whereby, she was so much injured, that nobody cared to venture home in her, and she was left in Russia. A slight sketch of this double ship may be seen in the Gentleman's Magazine, 1788, p. 1069." Extract from the "Gentleman's Magazine," for December, 1788. ** "This is a sketch of a vessel of a new construction invented by Patrick Millar, of Dalswinton, Esq. This vessel is a kind of double ship strongly connected by her upper works; she is 90 feet long, with her other dimensions in proportion, has five masts and is provided with wheels, which work a number of oars, to be used when there is no wind. She is said to have cost upwards of 3,0007. Whatever may be the success, Mr. Millar is entitled to the thanks of the public for risking so considerable a sum in the improvement of the naval architecture of this kingdom. This sketch was taken when she was lying on the mud in Leith harbour."Gent. Mag. December, 1788. But the solidity of the globe whose radius is K CR, is 3; and in like manner, the solidity of that whose radius is KA=r, is πr; therefore by subtraction, we have (R3-13), for the solidity of the spherical shell. This is the expression for the solidity of a spherical shell as it would be deduced by the common rules of mensuration, and we have now to show how the same expression is deduced from the properties of Gualdinus, or according to our principle of Centrobaric Mensuration. Let the semi-annulus E CFIAH revolve about the straight line E F, which remains fixed in its plane; and by our general principle, it will generate a solid, the contents of which are equal to a prism, whose base is equal to the revolving area, and altitude the circumference of the circle described by its centre of gravity. Now, the area of the revolving semi-annulus is expressed byπ (R2—r3) and by mechanics, the distance K G is 4 (R3-13) expressed by the term 3T (R2) where G is the centre of gravity of the revolving area, and consequently K G is the radius of the circle described by that point during the revolution, the circumference being GMN= CENTROBARIC MENSURATION. 8.(R3-73) which is equal 3 (R2-) to the altitude or height of the prism, whose solidity is the same as that of the spherical shell; but the base of this prism, which is equal to the generating area, is (R2-2); consequently by multiplication, we get 8 (R3-3) (R2-72) 2 = (R3-3), 3 (R2-72) being precisely the same expression as we obtained by taking the difference between the solidities of two spheres whose radii are R and r. But = =3.1416; therefore by substitution, we get the following numerical value, viz.-solidity of the shell-4-1888 (R3 —r3). If the exterior and interior diameters of the shell be substituted instead of the radii, the expression becomes, 4.1888 (R3-3)=0·5236 (D3 — d3); where D and d are the respective diameters of the shell, and the rule derived from the expression in its present form, is as follows: RULE. Multiply the difference of the cubes or third powers of the exterior and interior diameters of the shell, by the constant coefficient 0-5236, and the product will be the solidity sought. Let CE B, fig. 20, be the segment of a circle, of which the diameter is AD, the chord of the segment being C B, and its height or versed sine K E; then, if Fig. 20. whose base is equal to the revolving plane, and of which the altitude is equal to the circumference of the circle described by the centre of gravity. Since the semi-segments KEC and KEB, are equal and symmetrically placed with respect to the height or versed sine KE, or diameter EF, it follows, that the centre of gravity of the whole segment CE B, must be equally distant from CB, the chord or diameter of the segment's base, as are the individual centres of the constituent semi-segments, K E C and K E B. Now, by the principles of mehanics, the centre of gravity of the circular segment CE B, is distant from the centre at P, by a quantity of which c3 the value is 12 a' where c is the chord of the segment and a its area. Therefore, to find the centre of the circle described by the centre of gravity of the revolving plane K E C, we must set off from the centre P, on the diameter F E, the disC3 tance P Q equal to the expression 12 a obtained by calculation according to the dimensions of the segment; then will Q be the centre of the circle sought. Through the point Q, and parallel to the chord K C, draw the straight line QR; the centre of gravity of the revolving plane, K E C, is situated in QR, and distant from Q by a quantity whose value is v (3 c2+4v2) where a and c denote as 24 a in terms of the semi-chord or radius KC; for this purpose put c=2r, and then by substitution and restoring the value of π, we shall obtain the following expression for the solidity of the spheric segment, viz. solidity=0 5236 v (3 r2 + v2) ; which is the identical expression given for the purpose in the books on mensuration. The practical rule is as follows:To three times the square of the radius of the base, add the square of the versed sine or height; multiply this sum by the height, and the product again by the constant fraction 0·5236 for the solidity of the segment. ON CERTAIN MECHANICAL FALLACIES. Sir, I am rather surprised that the communication of Mr. Dixon, at p. 325 of your last volume, has so long escaped the animadversions of your correspondents; but I confess I should be still more so to learn that Mr. Dixon's invitation to "persons of science" to communicate with him on the subject of his paper had been responded to. Small indeed is the portion of science requisite to enable any one to see that such a proceeding would be quite supererogatory! 66 the wise man's meaning, or that his own wits have gone a wool-gathering. At length, recollecting himself somewhat, he puts the simple question. "But what is to turn the spindle ?" I am not at present in a condition to give you Solon's answer to this question. I shall do so, however, when Mr. Dixon gives me an answer to this other question. Supposing we adopt his suggestion, and dispense with the steam-engine, how are we to condense the air? The case I have supposed is precisely analogous to Mr. Dixon's. In both we are told to do away with the prime mover, a generator of power-and to replace it by a transmitter of power! Mr. Dixon belongs to a class, of which the late Mr. John Galt was, and the present Dr. Sleigh, is a type. The class is a very numerous one. That it is so is, I have no doubt, in a great measure owing to the unfortunate name which has been applied to the first elements of machinery Those -I mean, mechanical powers. elements, however combined, do in no case give out more power than has been previously supplied to them. The appellation of powers, therefore, is peculiarly inappropriate, and seems only to mislead the inexperienced. Mr. Dixon's proposition is briefly this, to dispense with steam for the propulsion of vessels, and to substitute in its placewhat? Why, condensed air! Suppose a person looking over the complicated, but withal symmetrical details, of an extensive manufactory. At length he arrives at the cumbrous, but powerful, water-wheel which actuates the whole. After contemplating for a time its movements, he turns to the proprietor, and with a benignant air thus accosts him. the vessel B into the boiler." My dear sir, why will you be so needlessly extravagant, and persist in the employment of such expensive means for the working of your machinery ?" In reply, the proprietor admits that his water-wheel is expensive, but adds that no other means of performing the work, with which he is acquainted, would be less so; if he knew of such, he has too much at stake to hesitate an instant as to adopting it. 66 Well, sir," says the sage, “take my advice. Remove your waterwheel with all its appurtenances to-morrow, and substitute for it a revolving spindle!" The proprietor looks at Solon for a little with puzzled air, as if uncertain whether it be that he has missed While on the subject of fallacies I may briefly point attention to another, an account of which is given in the last No. of your Magazine, p. 105; it is Allen's Patent Priming Preventer. The vessel B is filled with grease (of course in a fluid state), and the inventor says, that when the cocks C and D, both communicating with the boiler, and with the vessel B, are opened, "the pressure of the steam from above will force the contents of Who does not see that no such effect can pos- G. |