The revolution in tactics alluded to above, rendered of course the ordinary system of rigging useless, and the inventor has consequently devised the system of Self-reefing traversing sails (also lately exhibited at the International Exhibition). The masts, which are T-shaped, are supported by revolving shears, and the sails are fixed on spars rigidly attached to the masts. The mast is thus inclined to the wind, or "rakes," to use the ordinary term, whether the vessel be by the wind or going free-an arrangement which, for the same vertical height of masts, gives a greater and far more efficient spread of canvas than can be produced by any of the systems now in use. On a smart breeze springing up, the sails reef themselves to the compass requisite for the vessel's progress; and, as the gale freshens, reef after reef is taken in, until, when it is at its height, her sails will be found close-reefed, without the employment of a single hand. If the ship be clear of the land, her sails can be furled, her helm left, and the ship will ride the gale out head to wind. Ships and boats on this principle can, of course, equally with any others, be propelled by steam or other power. In his Atmospheric Guide-Propeller (exhibited also in 1851 (Class VIII. 82) and 1862 (Class XII. 2746)), the inventor has endeavoured to introduce a great simplification into ship propulsion, by combining the processes of steering and propelling. The plan consists in pumping a current of air through tubes which are led outside the vessel into the water, this current being capable of the nicest regulation and change of direction by means of valves. Water may be used instead of air, and is recommended for boats, in which, it may be observed, oars are entirely dispensed with, and propulsion is effected by hauling on an endless rope. The last point is Ventilation, and for the appreciation of the advantages of the new system in this respect it is almost necessary to refer to models. In the Exhibition of 1862 a model was shown, made to a scale, and intended to test the relative merits of a ship on this system and the Great Eastern.' The dimensions of the vessel on the Vertical-Wave-Line system of equal tonnage were, length 432 feet (as against 700 in the case of the 'Great Eastern'), breadth 108 feet, depth 76 feet. Models and drawings illustrative of the construction and propulsion of VerticalWave-Line ships may be seen at the Naval Museum of the Royal United Service Institution, Middle Scotland Yard, and at the Museum of the Commissioners of Patents, South Kensington. A New Marine Boiler for generating Steam of High Pressure. The boiler was a cylindrical tubular boiler, with certain arrangements of radial tubes for taking up and conveying the steam, and made to rotate slowly in the furnace on its axis. The advantages claimed were freedom from priming, smallness of space occupied, superheating the steam, and economy of fuel." On the Prevention of Railway Accidents. By J. SEWELL. The author considered that the main cause of accidents was the want of punctuality in the trains; and that this arose mainly from the overloading of them, which rendered it impossible that they could keep time. Engines were made to perform certain work, and draw certain loads, and if these were exceeded it was impossible that time could be kept. This was a matter that the public could not ascertain for themselves, and he therefore advocated the importance of having engines licensed, like boats, omnibuses, &c., by Government, to draw certain loads; and a statement giving that information should be placed conspicuously on the engine. This would prevent the overloading, as it would be in the power of every passenger to see whether the power of the engine was duly apportioned to the carriages it had to draw. On the Failure of the Sluice in Fens, and on the Means of securing such Sluices against a similar Contingency. By W. THOROLD, M.I.Č.E. The author described the circumstances attending the failure of the sluice, and pointed out by a diagram that, in his opinion, the mode of preventing such an accident in future was the employment of double sluices, one behind the other, the water between the two being always kept locked in, at a mean height between the water in the drain and that on the sea-side, during the time the sea doors are closed by the tide; by this mode, the pressure of the highest tide, on each set of doors, will be only one-fourth of that on the single set of doors, on the fallen sluice, at the time of the disaster. Hence its undoubted safety. On the Merits of Wooden and Iron Ships, with regard to cost of repairs and security for life. By L. WILLIAMSON. The author called attention, in particular, to an iron ship, the 'Santiago,' which met with a collision, the consequences of which would have been absolute destruction of the vessel had she been of wood; whereas, being of iron and having watertight compartments, the vessel was able to pursue her voyage, and was repaired at the cost of a few hundred pounds, instead of several thousands which would have been necessary had she been made of wood and could have been preserved from foundering. Oblate Projectiles with Cycloidal Rotation, contrasted with Cylindro-ogival Projectiles having Helical or Rifle Rotation. By R. W. WOOLLCOMBE. The object of this paper was further to discuss the views of the author given in a paper read before the Royal Society in March last (1862), entitled, "An Account of some Experiments with Excentric Oblate Bodies and Discs as Projectiles," and to show the result of further experiments. Rifled cannon, it appears, cannot project heavy elongated shot with high initial velocity; and, except with the Whitworth flat-headed shot, the penetration of iron plates can only be effected by means of a high velocity. The author considers that however well the helical or rifle method with cylindrical elongated shot may answer for small arms, yet that, when we wish to project great weights with great and sustained velocities, we shall succeed better if our mechanical arrangements are less antagonistic than the rifle principle to the great laws of nature, as exhibited in the form, method of rotation, and translation of the great natural projectiles, the planets. None of these are prolate bodies projected with helical rotation about their longest diameters and in the direction of such axis. The author states that he has found it practicable to project a body that, instead of being prolate, is more or less oblate, that, instead of having helical rotation at the expense of translation, has cycloidal rotation in aid of translation. A projectile, having a circular periphery in the line of motion in the gun, leaves the bore as a common round shot, and has the additional security for high initial velocity of windage less than for round shot of similar weight. The terminal velocity is also provided for by the oblateness, and by the axis of rotation being always transverse to, and not in the plane of, the trajectory. The gun has a similar transverse section to that of the projectile, the bore being straight and smooth. The projectile is a disk, and it should be slightly excentric to make it rotate-so slight as to be little more than the inevitable excentricity of every spherical projectile. The author then gave the results of some actual experiments with a gun and projectiles made on this principle. The gun was 20 inches long; the calibre, long diameter 17 inch, and short diameter inch. The shot weighed nearly 8 ounces, with a charge of 2 ounces, or three-fifths the weight of the shot; the penetration at 25 yards from an oak target was a mean of 11 inches, reckoning to the near side of the disk, and to the far side nearly 18 inches. The initial velocity, measured by Havez's electro-ballistic apparatus, was 1487 feet per second. A comparison was made with a small brass gun, length of bore 34-625 inches, or nearly double the length of the author's gun in calibres. The mean calibre of the brass gun was 16 inch, the mean diameter of the round shot was 1.43 inch; and this gun, fired with a proportionate charge of powder, showed that the disk gun gave more than double the penetration of the brass gun, and an initial velocity of 1487 to 1091 of the latter. He thought that these remarkable experiments showed that the subject was worthy of further consideration. APPENDIX. On the Solution of the Linear Equation of Finite Differences in its most General Form. By Prof. SYLVESTER, F.R.S. ... to The author exhibited (and illustrated with examples) a simple and readily applied method of obtaining the general term (and consequently the complete solution) of an equation of finite differences with any number of independent variables, a question which, although touched upon by Libri and laboriously investigated by Binet, had hitherto, to the best of his knowledge, remained unsolved even in the case of an equation with but one independent variable with non-constant coefficients; when the coefficients are supposed constant, the well-known solution flows as an immediate corollary from the author's general form. Essentially the method depends upon the adoption of a natural principle of notation for the given coefficients, according to which each coefficient is to be denoted by a twofold group of indices, the number of the double indices in a group being equal to the number of independent variables in the given equation. Thus, supposing um, n, p . . . be expressible by means of the given general equation, as a sum of u's with inferior indices, the coefficient of u, v, ... in that sum must be denoted by the double index group [m,, m, n, P...]. The process for obtaining the general term in uz, y, z . . . is then shown to be reducible virtually to the problem of effecting the simultaneous decomposition of the integer variables x, y, z... into parts in every possible manner and order of relative arrangement, the magnitudes of such parts being limited by the degree or degrees of the given equation in respect of these variables. The collective value of the terms thus obtained constituting the complete solution may be termed, in the author's nomenclature, a hyper-cumulant, whose properties and their applications remain to be studied out as those of the elementary kinds of common cumulants have been to a considerable extent in the ordinary theory of continued fractions. The first stage in the process of constructing the terms of a general cumulant or general hyper-cumulant is almost identical with that of finding the coefficients in the expansion of a power of a polynomial function of one or several variables, differing from it indeed only in the circumstance that permutations which lead to repetitions in the latter case, represent distinct values in the former. On Aerolites. By Professor N. S. MASKELYNE. Professor Maskelyne prefaced a series of notices of meteorites lately added to the collection in the British Museum by some observations on the phenomena that accompany the fall of such bodies to the earth. Loud reports and the development of brilliant light in the sky are among the most generally observed of these phenomena. The fallen mass or its fragments, besides the marked characters they constantly present, as well in composition as in the mode of aggregation of their component minerals, exhibit also invariably a superficial enamelling or incrustation. The meteorite which fell at Butsura, in India, on May 12, 1861, accompanied by successive reports and a luminosity in the sky visible in the daytime, presented some new and very interesting facts bearing on the cause of this incrustation. The whole of the fragments found, though they fell in four places, at distances of three or four miles apart, formed the parts of a large piece of an aerolite, fitting to one another with great exactness, with the exception of two of them, between which an intermediate fragment had been lost. Some of the fragments were found to be entirely coated with crust, yet capable of being adjusted to each other with unmistakeable accuracy; others again exhibited no such incrustation at the parts where they fitted to each other, and were yet, like the former, found several miles asunder. It was obvious from this that some of these fragments had become coated with crust after they had been severed, while others had been so severed without becoming subsequently incrusted. That the incrustation was the result of superficial fusion seems the best explanation of its presence on the meteorite, as well as of the partiality with which it was distributed. Such a superficial fusion, however, could only result from the development of heat of enormous temperature very instantaneously; and the best if not the only satisfactory solution seems to be that recognized by most physicists, namely, that it is the result of the heat generated by the aerolite entering the earth's atmosphere with the velocity of a cosmical body, and of that velocity being reduced with a suddenness that brings down the motion of the aërolite to that of a falling body in a few seconds of time. The light associated with the fall of such a body is probably due in part, as Haidinger has suggested, to the actual incandescence of the air, partly to the combustion of the iron and the ignition of the stony material as the surface of the aerolite fuses and streams away in a state of ignition and is thus left behind it in its path. The reports heard may be due to the actual bursting of the mass into fragments, from the gradual penetration towards the interior of the high temperature constantly being developed on its surface. That interior, bringing with it the intense cold of space, and the contracted volume due to that coldness (probably also brittle in consequence of it), remains in its more shrunk state, while the outer parts are expanding. Wherever there are lines of weaker aggregation therefore in the mass, or where the heat is able, from differences of conducting power in the material, to penetrate the mass unequally, a tendency in parts of the mass to break away from an inner core will ensue, and the explosion is the result. The causes that have combined to sever the mass into fragments may recur to cause explosions in the fragments, especially if their coherence has been shaken and cracks have been formed in them. If the aerolite has not lost too much of its velocity at the time of the explosions, the incrustation will recommence on the fresh surfaces. Where the velocity has been too far reduced, this process will not be repeated, and the stones will fall without a crust on the faces of fracture. Intermediate stages of slight incrustation and even of a mere thin glazing are by no means rare, and several of these are illustrated by specimens in the British Museum. Mr. Maskelyne next pointed out the conditions which must have been present in the earlier stages of the history of an aerolite. The presence of an excess of iron and a deficiency of oxygen is attested by the existence of metallic iron in almost every known aërolite. One has to imagine a mixture of molten metals gradually oxidizing in a rare atmosphere, and to suppose that the more oxidizable of them take precedence in their claim to the oxygen. These have, probably, during the process displaced some of the iron and nickel where these metals had become already combined, as in the cases where we find the iron isolated in the form of a microscopic, often crystallized dust in the interior of aerolitic minerals (like the suboxide of copper in avanturine glass). We have also evidence of stages in the history of the formation of an aerolite. The orbicular structure of so many of these bodies is an indication of one stage of this kind. The spherules which characterize this structure are often composed of a single crystalline and homogeneous mineral, with a radiating structure; often they are breccias made up of several crystals of the same or of different minerals united by a granular network of mineral. These spherules are often surrounded by a shell of meteoric pyrites or iron, and are set in a mixed mass, often highly porphyritic, composed of similar ingredients with the spherules. The solidification of this ground-mass marks, probably, a second stage in the history, the former indicating the very gradual separation by cooling of some of the ingredients of the aerolite, and the latter the result of the further gradual cooling of the residuary mass. There is no glass or uncrystallized matter apparent in any aerolite yet examined. Hence the meteorite, while presenting analogies with a slag in so far as that it is produced in the presence of an excess of metal, is in other respects analogous to a lava from the gradual manner in which its cooling has taken place and the different minerals have become separated out. A third stage in the history of the aerolite is exhibited in the veins of metallic iron and of other substances which are so often found not only cementing the sides of narrow fissures in meteorites, but frequently in the more compact varieties traversing with those fissures the substance of the spherules, and producing in them and the surrounding mass the phenomenon of "a heave," such as one sees in a lode when the two sides of the fissures have shifted their relative positions. The next subject introduced was that of the minerals contained in aerolites; and Mr. Maskelyne pointed out that, from the optical characters exhibited by these minerals when under microscopic examination, he was led to believe that augite and felspar can rarely be detected in the high proportions in which they are asserted by the chemist to be present in the chondritic variety of meteorite, though constituting the mass of other kinds. In the former kind, on the other hand, the crystals seem, in the majority of cases, to exhibit the planes of polarization in directions which belong to minerals crystallizing in the prismatic system. The following meteorites, many of which had been recently acquired by the British Museum, were next described in detail. Chondritic Aërolites. 1. From Akbarpúr, Shahjehanpur, India, lat. 27° 48', long. 79° 43'. An entire stone, for a long while in the British Museum, which fell at this place, April 18, 1838. It weighs 3 lbs. Its sp. gr.=373. It presents a beautifully marbled surface when polished, richly veined with a dark mineral (chromite, probably). 2. The stones, some incrusted and some only partially so, the fall of which has been above alluded to, and which fell on the banks of the Gunduk, near Butsura, on May 12, 1861, lat. 27° 7', long. 84° 9', at four places. Sp. gr.=3.60. 3. Nellore, in Madras. A stone weighing 30 lbs., which fell at Yatoor, near this place, on January 23, 1852. Its sp. gr.=3.63. 4. Mhow, Ghazeepúr, lat. 25° 54', long. 83° 37'. A stone that fell on the 16th February, 1827; sp. gr. =3.521. 5. Dhurmsala, in the Punjaub; fell July 14, 1860; sp. gr.=3·42. 6. Kheragur (perhaps Dhenagur), near Agra; fell March 28, 1860; sp. gr. =3.391. 7. Parnallee. The largest of the two stones which fell at that village, in the Presidency of Madras, on February 28, 1857. Its weight is 130 lbs., and its sp. gr. 3.41. 8. Durala. Fell February 18, 1815, at Durala, in the territory of the Putteala Rajah, lat. 30° 2′, long. 76° 52'. For a long time at the East India House. It weighs 20 lbs. 9. Agra. A stone the property of William Nevill, Esq., part of the stone recorded to have fallen on August 7, 1822, at a village in the neighbourhood of Agra, 300 miles N.W. of Allahabad. Its sp. gr.=3-666. 10, 11. Two stones that fell, the one at Umballah, at an uncertain date, in one of the years 1822 or 1823, and the other at Bitoura, 75 miles N.W. of Allahabad, on November 30, 1822; sp. gr. of Umballah stone=3·448; of Bitoura stone =3.57. 12. A part of one of the several stones that fell at Allahabad and Futtehpur on the last date. These last four stones may all belong to one and the same fall; but if the date of Mr. Nevill's Agra stone be correct, it is certainly a distinct one from the other three. Its high specific gravity, its large amount of iron, and general aspect would render it probable that it is so, which would confirm the correctness of its date. The Umballah stone is very unlike either of the others, and is probably a separate fall. That from Bitoura certainly belongs to the fall of Allahabad and Futtehpur. The sp. gr. of the Allahabad stones range from 3.54 to 3:57. 13. A small stone fell in the field called the North Inch, close to Perth, in Scotland, on May 17, 1830. A small portion of it was reserved by Dr. Thomson of Glasgow, and has since passed into the possession of Mr. Nevill. The British Museum is indebted to that gentleman for the half of it. It is a remarkable little meteorite, very rich in a peculiar mineral with a radiated structure; sp. gr. =3.494. To the class of aerolites devoid of marked spherular structure belong 14. The Shalka stone that fell, on November 30, 1850, at Shalka in Bancoorah, Bengal. 15. That of Bustee, in Goruckpúr; lat. 26° 49', long. 82° 44'. Perhaps the most singular of all known aerolites. It fell near that place on December 2, 1852. In it Mr. Maskelyne has detected a mineral to which he gives the name of Oldhamite a yellow transparent body of cubic crystallization, consisting of a sulphide of calcium containing more than one equivalent of sulphur. Four other minerals in this aerolite were also crystallographically described, one of a golden-yellow colour, and cubic in its crystalline system. 16. Moradabad; sp. gr.=3·143; fell at that place in 1808. |