144 . III. DIST. CHAR. Substance, 



* * Aggregate Stones. 



Agate. James, p. 181. F. Veg. of woodf. 

 Siliceous Sandstone. Kirw. p. 364, F. An. and 

 Veg. 



MAGNESIAN ORDER. 



Bole. James, p. 399. F. An.- We have seen tes- 

 taceous remains with nuclei of a substance that 

 had all the characters of this earth The earths 

 and stones of the magnesian order are almost 

 wholly confined to primary rocks : hence their 

 rare occurrence under extraneous forms, 

 b. 103. THE INFLAMMABLE MINERAL SUBST. 

 (substantia miner, mflammabilis) of an extraneous 

 fossil is either carbonaceous or bituminous. 



Obs. The minerals which belong to the class of 

 fossils generally denominated inflammable, are not 



Ferber's authority in opposition to his own opinion on the subject. 

 Ferber, indeed, appears to have repeatedly examined shells petri- 

 fied in jasper, during his travels through Italy (v. Eng. Trans, by 

 Raspe. p. 14. 27. 84. &c.) Mr. Kirwan, however, suspects that 

 real jasper is not found as a secondary stone consequently, that 

 it has not occurred as the substance or matrix of petrifactions. 



f A combination or aggregate of calcedony, jasper, hornstone, 

 quartz, c. when the mass is capable of receiving a polish, and is 

 decorated with more than one colour, is called an agate. This 

 sometimes occurs in petrified wood : the original matter having 

 been displaced by two, three, or more of the siliceous substances 

 just enumerated the fossil compound thus formed is generally 

 denominated a petrifaction agate the petrified wood described 

 by Linne under the title of Lythoxylon Achatinum (Mus. Tessi- 

 nianum. p. 102.) appears to have been a most splendid specimen of 

 this kind. 



