Platina Lamp.-In a communication from George Merryweather, Esq. to Professor Jameson, dated Edinburgh March 5th, 1831, it is proposed to extend the aphlogistic platina lamp, by constructing the body of the lamp of tin, large enough to contain a quart or more of alcohol. This will be sufficient to keep the platina in a state of constant ignition for thirteen or fourteen days and nights. Such a lamp, while it is entirely devoid of glare, affords sufficient light to shew the face of a watch in the dark of night. It is best managed by inserting a little spongy platina into a small cage of platina wire. The top of the lamp wick should be spread out a little, in the form of a coronet, and the wire cage pricked into it, so as to be nearly, but not quite, in contact with it. The bottom of the lamp should be concave so that the wick may take up all the alcohol, and if it be connected with an unfailing reservoir of alcohol, the lamp may be kept ignited for years. The spongy platina does not appear to be in the least deteriorated by being kept in a state of constant ignition.

To prevent the access of dust, &c. the lamp is covered with a glass, shaped like an inverted funnel, resting upon a ring or cylinder of tin having holes around it to admit a current of air. If a light is required, the glass cover is to be elevated and the platina gently touched with a match of chlorate of potash, which will be instantly inflamed.

Should the lamp diffuse an unpleasant odour in the room, a condensing shade or cover may be applied to it, formed of tin. This cover is conveniently made of a conical shape. The base of the cone is to be convex inward, like the bottom of a common glass bottle. From the centre of this concave bottom (concave externally) a tube proceeds downwards, of sufficient length and diameter to admit the neck of the glass funnel which covers the lamp. The vapours that rise up through the funnel into the conical condenser, and fall to the bottom of it in a liquid state, may be drawn off through a stop cock soldered to the edge of the cone. This cone may be suspended by a ring to a nail in the wall, and brought over the glass funnel when required.

The author finds that equal parts of alcohol and whiskey answer quite as well as pure alcohol, or he says, one third of alcohol and two thirds of whiskey do very well. This lamp may prove very useful in mining districts, as a con

stant light that may be depended upon, if the reservoir is periodically replenished.-Edin. Phil Jour.

Thunder Storms in France.-The Count de Triston has made observations on the direction of the thunder storms which have devastated the department of the Lorich for the last sixteen years. The following general inferences have been made by him respecting the progress and intensity of thunder storms in plain countries, intersected by shallow valleys. Thunder storms are attracted by forests. When one arrives at a forest, if it be obliquely, it glides along it; if directly, or if the forest be narrow, it is turned from its direction; if the forest be broad, the tempest may be totally arrested. Whenever a forest, being in the path of a thunder storm, tends to turn it aside, the velocity of the storm seems retarded, and its intensity is augmented. A thunder cloud which is arrested by a forest, exhausts itself along it, or, if it pass over, is greatly weakened. When a large river or valley is nearly parallel to the course of a thunder storm, the latter follows its direction; but the approach of a wood, or the somewhat abrupt turn of the river or valley makes it pass of. A thunder cloud attracts another which is at no great distance, and causes it to deviate from its course. There is reason to believe that the action is reciprocal. A cloud attracted by a larger, accelerates its motion as it approaches the principal cloud. When there is an affluent cloud which was committing ravages, it sometimes suspends them on approaching the principal mass, which is perhaps a consequence of the acceleration of its course; but after the union, the evil generally increases. Twenty-one thunder storms, whose course has been distinctly traced, have extended from N. N. W. to S. S. W. No destructive thunder storms have come from any other points of the horizon. Lastly, the position and form of the forest of Orleans, Blois, &c. satisfactorily accounts for the frequency of hail storms in certain communes, and their rare occurrence in others.

Round Sterns to Ships of War.-The important question of round sterns has with much generality been discussed; and it is therefore with no ordinary pleasure that we find a splendid prize has been offered by the French Minister of Marine, for determining among all the forms that can be presented that particular one, which

shall unite in the highest degree all the requisite conditions that the seaman, the naval architect, and the geometrician may require.

Our readers are aware that a vigorous contest was for a long time kept up respecting the principle of the round sterns; but time, which softens differences, and moulds even prejudice itself into the form of truth, has in this case obtained another victory; and a figure which our gallant seamen had connected with the glorious recollections of Trafalgar and the Nile, is now-with wisdom which cannot be too highly praised-nearly if not altogether abandoned. The square stern, with all its massy and cumbrous forms, has indeed given way to another, more in unison with the great march of improvement now going on.

But while the principle of what is commonly called the round stern has with few exceptions been admitted in all its fulness, its best possible form has not been determined; and it would seem as if fancy, rather than the sound discretion which geometry imparts, had presided over the designs hitherto submitted to the world.

Among the infinite variety of forms which may be denominated" round," there must be one which shall unite in a higher degree than any other, all the best conditions of strength, convenience and defence ;—which shall secure to the brave sailor the greatest degree of comfort, add a new arm to his power in the day of battle, and secure to that portion of the frame-work of the vessel, the same admirable strength as distinguishes its other parts. It is this choice of forms, which the French minister of marine now invites the naval architect, the sailor, and the man of science to contemplate; and we hail the call as a revival of the days when the great men of the Academy of Sciences, clad in the armour of the transcendental geometry, descended from the lofty elevation of the system of the world, to contend for the conditions of the metacentre, the great principles of stowage, the problems of masting, of pitching and of rolling, and all the other complicated but interesting inquiries, which the general question of ship-building involves.

Our Journal, read alike by geometricians, the naval architects and the sailor, can hardly be better employed than in recording the conditions which the French minister has proposed for this great problem.

"To furnish the best plans for the circular sterns for line of battle ships and frigates, with all the exterior and interior fittings, the manner of disposing the timbering so as to combine the necessary conditions for defence, with strength, lightness, a dispersion of the weight in proper proportion to the displacement of each part, the efficiency of the rudder, the convenience of the water-closets, and the general suitableness of the accommodations.

"This manner of fitting the stern must possess facilities for enabling the commandant to be aware of whatever manoeuvres may be in progress, without being obliged to appear on deck.

The style of ornament which it would be proper to adopt, as well for the forward as for the after part of these new constructions, is also to be described. The competitors are to remember that nothing of importance is to be at all sacrificed to these decorations.

"The side of the ship at the stern must have the same thickness as at the corresponding places in other parts of the ship. The ports must be so disposed, that it may be easy, on each deck, to bring guns to bear right aft and on the angles of the quarters, to command those points which the other guns cannot be brought to bear upon.

"The rudder may be fitted either without board, or within with a circular head, but reasons must be given for whatever plan may be proposed. Reasons also are to be stated for the station which may be proposed for the water-closets, whether they are fitted interiorly, or in an exterior gallery.

"The officers of the different branches of the naval service are called upon to send their proposals to the minister before the 1st of July 1832. Other persons wishing to become competitors, are eligible to do so.

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*

The memoir in which each competitor explains his proposals, must be accompanied with all the calculations and drawings which may be necessary to render his plan perfectly complete and intelligible in all its details.

"Each proposal must have a motto affixed to it, of which a copy is to be enclosed in a sealed letter, containing also the name and place of residence of the proposer. "A medal of the value of 2000 francs will be given to the author of the best memoir presented to the minister of marine before the stated period."-Brewster's Jour.

*The field is therefore open to our countrymen.-ED.

On the scarcity of Books.-The scarcity of a book, which has nothing else to recommend it, is a fact which is hardly worth knowing; but when the work has any real value, either from intrinsic merit, or from forming a link in the history of science, its scarceness then becomes an object of importance. It is constantly found that errors are perpetuated by writers who satisfy themselves by copying what they find at second hand, and these errors can never be corrected without reference to original authorities. It is useful, therefore, to know not only what books are scarce, but also (when it is possible) where they are to be found. It must often occur to those who have access to large libraries, that they meet with works which they had never before heard of; and the books so discovered will sometimes contain matter which had been looked for in vain. Neither is it to be attributed to a mere selfish anxiety for accumulation, when any one employs himself in collecting with this view. Much is learned from what is in our own possession, and even in the search for it; and every one who has indulged himself in collecting books, must have often found advantage from what, at the time of the purchase, he did not foresee that he should derive any particular use. This of course supposes that he has collected with some discrimination; and if in that case he should sometimes be induced to give a higher price than he otherwise would for a book in consequence of its scarcity, he is not on that account alone to be blamed. Brewster's Journ.

Account of the Aurora Borealis seen in Roxburghshire on the 5th of October 1830. By Mr. W. Laidlaw.-On Friday evening, the 17th September, an uncommon form of the aurora borealis was observed all over the country. It was in the shape of a luminous white arch, and stretched from W. by S. to E. by N. nearly ending on the E. in a pencil-formed point, and was accompanied by pale streamers in the north horizon, and continued visible from twenty to thirty minutes.

This evening, (October 5,) I was called to observe an appearance that seemed at first to be nearly similar, though it was more bright and better defined. When first seen it passed exactly over head, and in a direction perhaps nearly the same as the former; it was very bright, and