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longer enumerated as a British genus of plants. The Brassica muralis and Monensis of Hudson, are returned to the genus Sifymbrium ; as Cardamine petråa is to Arabis. In the same manner, the Hedypnois hieracoides, teftorum, and biennis of Hudson, are returned to the Linnean genera from which that botanist had removed mhem, namely, Picris and Crepis. In the class Cryptogamin, the removals are still more numerous.

We have thus related the principal improvements which Dr Smith has introduced into the British Flora. A comparison of this work with similar ones, will few the most careless observer, the great superiority it poflefles over them. The species are more accurately determined, and, in many cafés, referred to more proper genera. The synonyms appear to have been examined with great care; and Dr Smith professes to have quoted none, except such as he had himself ascertained to be right. * If to these we add the complete description given of every species, the botanist will easily conceive the highly finithed state in which the work is given to the public. We have, therefore, no doubt but that Dr Smith will receive from all quarters, the praise to which he is so justly entitled.

Art, VIII. Memoires de l'Academie des Sciences de Turin. An

née 1792 à 1800. Tom. VI. 2 Parties. pp. 600. 4to. Turin, 1801-2. De l'Imprimerie Nationale. THI "His volume contains many interesting and original productions

of the various learned Italians who belong to the Turin Academy. The papers which struck us as peculiarly worthy of attention, belong to the chemical, mathematical, and electrical departments of science. In each of these claffes, we find much to admire; and after shortly noticing the subjects of these tracts, we Thall proceed to lay before our readers a more detailed account of their contents, beginning with the chemical papers.

1. The chemical papers, which principally deferve attention, are three-' On the phosphoric light of certain stones rubbed with a feather or a brass pin'- Examination of hydrogenous gas after it had been kept many years,' both by Count Morozzo; and a tract

upon

* In one instance, however, we have found an erroneous reference, viz. in p. 280, Kali spinofum cochleatum, Raii Syn. 107 ; this ought to be 159. In Prunus infititia, the synonyms of Hudson are omitted ; in the first edition, it bure the same name ; but in the second, it was joined with P. domeftica, under the name of communis,

!

upon the combustion of fulphur and the metals, by the Chevaliers So Real and Maistre.

II. The mathematical papers are of great ingenuity, and their subjects very important – On the refolution of numerical equations of all degrees' - On a problem of difficult analyfis,' (vit. to describe the greatest possible ellipsoid in a papezioid or irregue lar solid), both by the Abbé Caluso_ On the resolution of equations of all orders,' by the Abbé Franchini-' On the division of circular arcs, ' by M. Michelotti-and' An essay on the problem, An integral number being given for a fide of a right-angled triangle, to find all the pairs of integral numbers which form the other two fides,' by the Pere Saorgio.

III. The electrical papers are likewise valuable. On the law f of Volta,' by Dr Canali-Solution of fome questions in elec

tricity,' by the Abbé Eandi-aOn the utility of conductors,' by Abbé Vafalli- On the muscular attractions produced by animal electricity,' by Meftrs Julii and Roffi.

1. We begin with the first of these divisions, reserving the on ther two for a future opportunity. Of the Phosphoric Light which fome Stones give when rubbed with

o Feather or a Brafs Pin, and particularly of the Phosphoresrence of the Tremolite and the Cyanite, with some Obfervations on the Positive and Negative Electricity of different Stones.

By the Count de Morozzo. After reciting the facts formerly observed on this subject, with which our readers are sufficiently acquainted, Count Morozzo proceeds to detail fome circumstances which presented themselves in the course of his experiments upon these curious appearances. These experiments were chiefly made with a very delicate electrometer, invented and constructed by the Abbé Vafalli, described in the last volume of the Turin Memoires, and preferred by Count Morozzo to every other.

With this initrument, good tremolite crystals gave, when rubbed, figns of confiderable positive electricity, as did also the Dolomie ; but Cyanite Blende and Cadmie, though very Juminous, gave no marks whatever of electrisation. In this manner, our author was driven from his first opinion, that the phofphorescence of stones is caused by electricity; and he continued his trials, in order to discover the true cause. He found that marbles, and all calcareous fpars, when rendered luminous, gave proofs of negative electricity; that the barytic and gypseous and selenitic spars gave marks of positive electricity, as also the Bologna stone; and that the fluoric spars gave marks of neither the

one

one nor the other kind. He infers that the spars containing carbonic acid contain negative electricity; while those which consist in part of fulphuric acid contain positive ele&ricity. He confirmed this idea, by examining metallic ores, and finding positive electricity in proportion as the acid which neutralized the bases was sulphuric; and negative electricity in proportion as that acid was carbonic. As a farther test of his doctrine, he calcined barytic spar and gypsum: the former, being deprived of its acid, gave negative inttcad of positive electricity; the latter, when deprived of its acid, gave neither. · Our author adds, that these experiments are extremely delicate, and often fail, or give equivocal or contradictory results. This he ascribes partly to the difficulty of finding substances perfectly homogeneous, partly to variations in the atmosphere, temperature, and manner of manipulating. But, in general, he thinks his experiments sufficiently consistent to authorise the inference, that there fubfifts fome connexion between carbonic acid and negative electricity ; between sulphuric acid and positive electricity. He concludes by noticing the experiments of

le celebre Anglois M. John-read, ' (meaning Mr John Read), with his doubler of electricity, and pointing out their coincidence with his own. This is remarkable in three points: first, that gentleman found, that atmospherical air, in a Itate of purity, is always positive ; fecondly, that when corrupted by vegetable or animal putrefaction, it is negative ; and, lastly, that respiration in a clofe chamber renders the electricity of its atmosphere negative, when before it was positive. We extract the concluding sentence of this neat and interesting little tract, as a specimen of modesty not too common among philosophers, even among those of France and Italy.

« Ce n'est qu'un aperçu que je presente à l'Academie. Ces experie ences ont besoin d'etre beaucoup diversifiées, et recevront par des mains plus habiles le degré de perfection que l'on peut defirer.' Part I. P. 149.

The light given out by stones, &c. may thus be thought by many to be an electrical phenomenon; and it may be supposed that this paper belongs rather to the lait of the classes into which we have divided these memoirs. But, besides that the experiments of Count Morozzo do not by any means warrant such an inference, we have thought it proper to place his fpeculations in the present article, becaufe they refer directly, in our opinion, to a subject which presents important obstacles to the new che:nical system; and, in this particular, resemble both the other memoirs of which this class is composed.

Phosphorescence, in general, is by no means ranked among the procesies of combustion, by the French fyftem of chemistry. The light, unaccompanied by any sensible heat, which certain stones give out after exposure to the sun, or any very luminous body, and the inferior degree of radiation which is perceived in almost all bodies, whether inflammable or not, when placed in broad daylight, and suddenly transferred into a dark place, (see Beccaria's experiments); these phenomena are commonly referred to the class of optical appearances, and are not supposed to have any connexion with inflammation. It deserves, however, to be remarked, that though the application of heat in all these processes greatly affifts the developement of light, still they resemble each other, and differ from ordinary cases of irradiation in these two material particulars, that they are carried on without injury to the body, and fail if the body has not immediately before been exposed to the light.

But there is a class of phenomena which resemble more nearly the common appearances of combustion, and which nevertheless

not, according to the French theory, to be ranked among those processes. We allude to the permanent phosphorescence of certain substances in all circumitances, yet unaccompanied by any thing like oxygenation. Of this description, we shall at prelent give only one instance, but that a very remarkable one, and one which has not hitherto been examined with the attention it deferves. We allude to the infects commonly known by the name of fire-flies, and abounding in the south of Europe. They resemble, in their fize and external appearance, some flies known in the north: their shape is oblong; their wings are covered with an outward fhell, like infects of the beetle tribe ; the head is red, with a black spot in the centre. In the dark, when they perch or creer, nothing is observable ; but as often as they rise to fly, a bright light is perceived. This is not constant during their flight, but recurs every other instant, as if it were disclosed by the opening of their wings at each successive expansion. When laid upon their back, they give out this light constantly, and have much difficulty in turning themselves. The light, when thus examined, is a clear, phosphorescent or lambent flame, of a green or light blue, inclining to yellow. It is very considerable even in one fly; and the light of three or four is l'ufficient to render small objects around quite visible. It is apparent in twilight. When these infects are examined by daylight, their bellies are perceived to be distinctly divided about the middle, by a line palling across the body. The under part is of a bright yellow, resembling in colour, smoothness, and in every particular, a bit of fine clean straw: the rest of the belly is quite black; the yellow part alone is luminous. When the fly is dead, the luminous appearance ftill continues for two or three days. If the yellow part be cut off, it thines as brightly as before ; and if rubbed between the fingers, a luminous greasy matter, like the bowels, oozes out, tinging the fingers, wherever it touches, with the same kind of lambent fame. This friction speedily terminates the phenomenon, apparently by exhausting the supply of luminous matter.

Air is by no means necessary, or at all conducive to this process of phosphorescence: on the contrary, under water, or other liquids, the dies shine as much as in the air.

Here, then, we have an animal process, at first fight resembling the flow combustion of the blood in the lungs, rendered visible by the extrication of light. We find, however, that no oxygenation whatever attends it. In what manner, then, are we to draw the line between such phenomena ? This is not a cale which can be explained by saying that light is absorbed, and then given out; for if the animal is kept alive for inonths in a dark place, the luminous appearance continues; and if it dies, that appearance survives but a short time. Something is evidently secreted, which burns or radiates with a lambent Hame, and which does not owe this luminous quality to any previous contact with light. The flame is kept up without air exactly as well as with it. No oxygenation can therefore be suspected. But no perceptible heat is evolved. Neither is any perceptible heat, or any perceptible light evolved in the first stages of combustion and oxygenation ; yet the new theory never fails to suppose such an evolution of both; only adding, that it is so low as to escape the senses. Here, much light is given out; consequently, the procefs resembles combustion much more than many cales in which it is admitted to take place. In fact, it resembles combustion exactly as much as the first stages of common phosphoric inflammation. How such phenomena are to be severally arranged and denominated in the theory of oxygenation, we are at a loss to discover. We fhall return to the same train of speculation, after analysing the following papers.

Examination of Hydrogen Gas, which had been kept twelve
years in a Bottle.

By the same Author.
Count Morozzo having been among the first to verify the cele-
brated discovery of our countryman Mr Cavendish, happened to
leave a pint bottle of hydrogen gas well sealed, with three inches
of water under it, in his laboratory, from the month of February
1785, and to find it there in July 1797. He immediately tried
some simple experiments, to examine the changes which it had
undergone.

On opening the bottle under water, an absorption of two inches took place. It burnt exactly like common hydrogen gas. A Imall animal introduced into the bottle' was seized with convul.

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