Page:Proceedings of the Royal Society of London Vol 1.djvu/399

Rh heated, and not decomposable by mere heat. It had no taste, n6 smell; it did not seem to be soluble in boiling water, nor even in muriatic, nitric, or sulphuric acid; neither did strong lixivium of caustic potash appear to produce the least effect; and the only processes by which it appeared to be affected were combustion. or the action of fused potash. In the latter case it emitted a smell of ammonia; it appeared to dissolve in the potash, which then gave indication of the acids that had entered into the composition of this singularly intractable substance.

Amongst the known combustibles, it is observed that charcoal is the only one which does not combine directly with oxymuriatic acid gas; but Mr. Davy is of opinion that it does in some cases unite by the medium of hydrogen, as in the state of oleﬁant gas, and in the formation of muriatic other. The author expresses a hope that new and more correct views of the composition of muriatic salts will faci- litate their decomposition, and explain, in a satisfactory manner, va- rious economical processes, long since practised, for obtaining the acid from common salt by means of aluminous or siliceous suh- stances, the success of which has in general depended on the acci- dental presence of moisture. in this Case the alkali forms a glass, and is rendered useless; hut by the substitution of iron ﬁlings, and passing steam over the mixture when heated, Mr. Davy has suc- ceeded in separating a portion of soda from common salt.

Although the property of emitting light, which is possessed by some animals, has appeared interesting to naturalists of all ages, and although many detached memoirs have been written upon the sub- ject. the author observes that the history of these animals is still ex- tremely imperfect; and he endeavours to supply the defect by enu- merating all the difemnt animals which, to his knowledge, possess that property, and to ascertain, by dissection or otherwise, the parts of their bodies from whence the light issues, and, by experiment, to discover the circumstances necessary or accessory to the emission of light.

The genera in which individuals certainly luminous are to be found are as many as twelve in number. There is one species of Pholas amongst the mollusca. Among insects are seven genera; Elater, Lampyris, F ulgora, Pansus, Scolopemdm, Cancer, and Mono- culus. Among the worms is one, Nereis. And in the class of zoo-phytes, the three genera of Medusa. Pyrosoma, and Pennatula.

The same property has also been ascribed to various kinds of ﬁsh; but, in the author's estimation, they have probably acquired that reputation by occasionally evolving light after death.

It has also been said, that the Lumbricus terrestris, or common earth-worm, has been found to be luminous for several days together;