210 



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 he 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 effervescence, 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 differ from the yellow, 

 except in containing a little of the oxide of copper. 



The Croonian Lecture on the Arrangement and mechanical Action of 

 the Muscles of Fishes. By Anthony Carlisle, Esq. F.R.S. F.L.S. 

 Read November 7, 1805. [Phil. Trans. 1806, p. 1.] 



The muscles of fishes, Mr. Carlisle says, are constructed very dif- 

 ferently from those of the other natural classes of animals. The 

 medium in which fishes reside, the form of their bodies, and the in- 

 struments employed for their progressive motion, give them a cha- 

 racter peculiarly distinct from the rest of the animal creation. Their 

 skeleton is simple, and their proportion of muscular flesh is remark- 



