The silica and the lime, Mr. Gregor considers as essential to the
composition of this mineral, as he has always discovered them, even
in the purest specimens.
In order to examine the nature of the volatilized matter. the author submitted some of the crystals to distillation. A fluid passed over into the receiver, and a white crust was formed in the arch and neck of the retort. The fluid had an empyreumatic smell, very similar to that observed in the fluid distilled from the white crust that sur- rounds flint. It changed litmus paper to a faint reddish hue. A va- riety of experiments were made upon the white crust, from the re‘ sults of which it appeared, that it consisted in part, at least, of an acid, which did not seem to be either the phosphoric or fluoric; nor did its properties entirely agree with those of the oxalic acid, although many of them were similar to those of that acid. A part of the fore- mentioned crust. which firmly adhered to the neck of the retort. was found to contain a portion of lead; this, Mr, Gregor ascribes to the action of the acid on the retort.
Some of the Barnstaple mineral was also tried, and was found likewise to produce the above-mentioned white crust. Mr. Gregor now makes some remarks on the yellow and green crystals already mentioned as accompanying the mineral here treated of, which he says he at first considered as similar to the two species of Uran- glimmer examined by Klaproth. The specific gravity of the yellow crystals, at 45° Fahr., was 2'19. Exposed to the blowpipe, they decrepitated violently. They are taken up by phosphate of ammonia and soda without efl’ervescence, and communicate a light emerald green colour to the fused globule. By exposure to a red heat they be- come of a brassy colour, and lose nearly a third part of their weight.
Several other experiments upon them are related. but their scarcity has, Mr. Gregor says, precluded him from operating on a quantity sufficient for a regular analysis. But he has detected in them oxide of lead, lime, and silica, which have not hitherto been considered as ingredients of Uran-glimmer.
The substance also, which in his experiments was held in solution by ammonia, had some peculiar properties which appeared to distin- guish it from uranium.
The green crystals, the author says, do not dilfer from the yellow, except in containing a little of the oxide of copper.
The muscles of fishes, Mr. Carlisle says, are constructed very differently from those of the other natural classes of animals. The medium in which fishes reside, the form of their bodies, and the instruments employed for their progressive motion, give them a character peculiarly distinct from the rest of the animal creation. Their skeleton is simple, and their proportion of muscular flesh is remark-
