84 New Publications. 



A\ thofe longifli lamella? are interwoven in one Angle direct 

 tion, and implicated in fuch a manner, that each junction 

 reSembles a vertebra, or hinge. With this idea, alfo, corre- 

 sponds the particular kind of the flexibility of the ftone, which 

 is not tough or coriaceous. For, if the lione be held upright 

 and fhaken, it vibrates with fome noife to and fro ; but as 

 foon as its agitation is discontinued, its parts conjoin again 

 firmly by a force like a Spring, 



I now proceed to its chemical analyfis. 



As, on triturating, I found the particles of the flone ex- 

 tremely hard, which was indeed previoufly afcertained by its 

 faculty of cutting glafs with eaSe, and of ftriking fire with Heel, 

 I endeavoured to facilitate its decompofition by previous me- 

 chanical comminution. 



To effect this, I Subjected one hundred grains to red heat, 

 and quenched them in cold water; but I obferved, that by 

 tiiis, neither their weight nor their hardnefs had decreafed. 

 They were then reduced to an impalpable powder in an agate 

 mortar, mixed with four parts of dried carbonated Soda, and 

 ignited under the muffle in a porcelain Saucer, during fix 

 hours, in a moderate degree of heat; by which the mixture 

 only conglutinated, without actual fulion. The ignited mafs 

 was pulverized with water, fuperfaturated with muriatic acid, 

 duelled and filtered. A quantity of very loofe filiceous earth, 

 to~the weight of 96^ grains, remained on the filter. 



The Separated muriatic fluid was treated with Pruffian 

 alkali; and the blue precipitate, thence arifing, ignited. It 

 weighed one grain ; of which, however, only \ grain can 

 be reckoned as oxide of iron, entering into the 100 grains of 

 the decomposed foffil. 



At laft, by faturating the folution with carbonated potafh, 

 a tender earth was thrown down ; which, after warning, dry- 

 ing, and ignition, weighed %\ grains; and, examined by 

 means -of Sulphuric acid, was Sound to be aluminous earth. 



Consequently, hundred parts of elaflic quarz from Brazil 

 have yielded, 



Silex - - 96*50 

 Alumine - 2,50 



Oxide of iron - 0*50 



99>5° 



There are Sometimes very Small blackifh grains, like points, 

 mingled with this ftone. As theSe probably are garnets, or 

 cryftals of horne-blende, it Seems that the portion oSiron and 

 alumine discovered in the foffil chiefly proceeds from them. 



XVI. Pro- 



