form, until the proportions are ascertained in which the earths combine; and we are thus directed with certainty to the mode of double classification. An extract of the report of Messrs. Haüy, Vauquelin, and Brochant, on the memoir, is appended to it in the pamphlet. This report approves the deductions of the author in favour of the crystallographical character as a basis of arrangement. It also replies to an objection, which the facts contained in the memoir may be supposed to raise, against the adoption of this basis, by saying that all which crystallography attempts to decide is, that sulphate of iron is present whenever the crystal of sulphate of iron is produced, and that felspar is present whenever the crystal of felspar is formed. MY DEAR SIR, ARTICLE IV. A Plan for a Fire Ship. (To Dr. Thomson.) Bushey Heath, Feb. 1, 1818. THE following plan, which I proposed in the year 1804, for the destruction of the enemy's flotilla, being now to a certain degree known, I send it, with your permission, for publication in the Annals of Philosophy. It is but fair that we should derive advantage from the invention of our countrymen, and not be doubly annoyed, as in the case of the torpedoes used by the Americans against our men of war, by having our own weapons turned against ourselves, and arming our foes to our own destruction. I have no doubt but that a fire ship steered as described in the following page, might be sent down and fall on board a large vessel laying-to to leeward before she could brace about the sails and gain sufficient way to avoid it. I remain, my dear Sir, yours very sincerely, It is proposed that a vessel, loaded as a fire ship with combustible materials, should carry at its mast's head a large flag (after the manner of a vane), attached to a spindle passed abaft the mast, through one or more iron rings, and turning in a socket on the deck: near the lower part of the spindle must be affixed the segment of a large cog wheel running into another correspondent with it at the end of the tiller, which is to be constructed of a due length for the purpose. The vessel then under sail being put before the wind, with the helm amidship, will continue to proceed in that direction; because at the instant of its falling off it would be counteracted by the operation of the flag upon the tiller, and restored to its original course.* By this contrivance the vessel when under sail may be steered, after the helm has been put in a proper position, either before the wind, on a wind, or on any intermediate point, with as much accuracy as by a good helmsman. To preserve the vessel from being sunk by the shot or shells fired at it, the hold should be filled with empty casks tightly bunged; and for the prevention, in the event of a leak, of the deck being blown up by the buoyancy of the casks, place strong pieces of timber on the upper part of the deck, from the stem to the stern post, through which, and some of the beams, have eye bolts driven, the eye part under the deck, and as many iron chains, or straps, hooked into the eyes, and the other ends firmly secured to the kelson. The mast should not be very taunt, which would render it more liable to be struck by the shot, and the sail should be square if the vessel be designed to go before the wind. The utmost range of a shell is 4,400 yards; if, therefore, the vessel be submitted to the guidance of the flag, and run at the rate of eight miles per hour, it will sail that distance in about 18 minutes. The fusee must be cut accordingly. A flag with a fly ten or twelve feet long will have very sufficient power to steer a vessel of a moderate size. The experiment of steering a model by a flag has been tried, and found to answer with great accuracy. As soon as the fire vessel is sent down, if the men of war were to fire with powder, an advantage would be obtained in the smoke driving to leeward, and enveloping the object in obscurity. Two circular segments of wood may be used instead of cog wheels; one fixed to the flag spindle, the other to the extremity of the tiller, the tiller ropes crossing each other, and the ends fastened to the outer parts of the circular segments; the ropes being tangents to the circles, the power on the helm will always be the same. The vessel may be brought to an anchor, if requisite, amidst the enemy's ships, riding under batteries, by having the anchor suspended from the tafrail by means of a stopper fastened to the cable, and immersed equal to the depth of water in which the ships are riding; the moment the anchor touches the ground the stopper will break, and the requisite quantity of cable will run out, and the vessel be brought up by the bitts. A chain should be added to prevent the inner part of the cable from being burned. In case a current sets along the coast under which the enemy's vessels are riding, a proper allowance is easily made for the drift. If casks were filled with inflated bladders, it would prevent their becoming useless by a shot-hole: should the flotilla to be * A Dutch dogger, from its light draft of water, is as well adapted for the pur pose as any other. attacked be numerous and occupy a considerable line, several fire ships ought to be employed, divided into three divisions; one division being sent down with the wind on the quarter, another before the wind, and a third on a wind; the last will annoy those which cut and run to leeward. The decks should be loaded with stones, or some heavy materials, that on blowing up more mischief may be done to the foe. The most advantageous time to send the fire ship among vessels at anchor is at the commencement of the flood, that in case they cut and run on shore, they may continue striking during the rise of the tide; and the most disadvantageous is at the period of half ebb, at which period the tide falls the quickest, and is consequently the most proper time to lay a vessel on shore to save the crew. ARTICLE V. Account of a Meteor, apparently accompanied by Matter falling from the Atmosphere, as seen at Cambridge by Professor E. D. Clarke, of that University, and other Persons who were Eye Witnesses of the Phenomenon. In a Letter to the Editors. GENTLEMEN, ON Friday, Feb. 6, being in company with two other persons who were walking with me in the environs of this University, I had the satisfaction of seeing a large and very luminous meteor in the northern part of the hemisphere, descending vertically from the zenith towards the horizon. My attention was called towards it by an exclamation from one of our party who called out, "Look at that Light!" The atmosphere was perfectly clear and serene, excepting a haziness near the horizon towards the north; and the sun, in a cloudless sky, was shining in great splendour. It was about two o'clock, P.M. The first impression upon my mind in beholding it, was, that a lacerated balloon, owing to some accident, was coming down in ruins; but the intense light with which it shone opposed to the full rays of the sun, almost as instantaneously convinced me of its real nature Its descent was extremely rapid, and being so perfectly vertical, and the shape of the falling body seeming to indicate the precipitation of matter in combustion, I expected to see it strike the earth; but when it arrived within about fifteen degrees of the horizon, it disappeared; there being as before stated a haziness towards the north extending upwards from the earth about 12 degrees. Before the meteor in its apparent path reached this fog-bank, it disappeared, Probably some other account of this phenomenon will reach you;* in the mean time I send you my brief statement of the fact; having been an eye-witness of it. This is the third great meteor which I have seen, in this country; the two former happened many years ago, during the night, and were seen all over Europe; that of the year 1783 was one of them; it differed in the direction of its course, which was nearly horizontal; although inclined at a small angle towards the earth. The form of the present meteor as seen from Cambridge was somewhat like tha of a Florence flask; it left a train upwards, which was broken into knots of light; and the light beaming from the 'body of the meteor was so intense that although opposed to the sun's orb it shone almost equal in effulgence to that luminary; and I have no doubt but that if it had happened during the night it would have equalled in its effect either of the meteors before mentioned. That a fall of matter has taken place somewhere towards the north there can be little doubt; although it be uncertain of what nature it may be, or where it fell, whether in the sea, or upon the land. Your readers, in their own opinions respecting the cause of this meteor, will perhaps differ from mine; but the theory of the phenomenon seems to me to be very simple; namely, that its appearance is entirely due to the heat and light evolved during the transition of a body from the aeriform to the solid state; a theory at present most happily illustrated by a recent experiment of the ignition of platinum wire, coiled around the wick of a spirit-lamp, which exhibits heat and light for hours after the extinction of the flame of the lamp so long as any of the alcohol remain; an experiment of course well known to you because it has attracted such general notice in the metropolis. I am ignorant of its author; but the nature of it is, I understand, thus explained; that "the hydrogen of the alcohol combining with the oxygen of the atmosphere, forms water; consequently heat is evolved." I remain, Gentlemen, very faithfully yours, Cambridge, Feb. 6, 1818. E. D. CLARKE. * It was seen at Swaffham, exactly at the same hour, where it was visible several seconds. An account of it appears in the "Norwich Mercury," published Saturday, Feb. 14, in which it is described as “a well defined orb of white light, giving off flame backwards." + Accounts from Lincolnshire have appeared in the public papers, that the inhaBitants, at the time of this meteor, were alarmed as by the shock of an earthquake; and a hissing noise was heard; the usual sound accompanying the fall of meteoris stones. ARTICLE VI. d A Solution of the Equation A" ( x) = (edx 1)" x . n being a whole Number, ex a Function of x, and e a Number whose Naperian Logarithm is Unity. By James Adams, Esq. But by Taylor's theorem, and separating x from its symbol d, we get p. 488. I trust, Sir, that the importance of the theorem and the conciseness of the demonstration, will, in some degree, be an apology for my sending them to you. I am, your most obedient servant, JAMES ADAMS. |