332 Extract from the third Volume of 



here present, confirm or rectify those before made by the 

 most celebrated chemists. 



AnQhjsis of sonorous Porphjry, 



Sonorous porpliyry unites in it all the mineralogical cha- 

 racters of the other porphyries. Its substance, equally 

 hard, is composed of silex and alumine, interspersed with 

 some small leaves of feld-spalh, and small grains, not very 

 numerous, of aiuphibolite. But it difll-rs fronj it by its foli- 

 accous fracture. Besides, when broken, it has a sound 

 almost metallic. The name of sonorous porphyry appears, 

 then, to be perfectly suited to it. 



It is found in the mountains of Bohemia, in those of 

 Upper Lusatia, and in the country of Fulda. It never forms 

 these continued chains, but only insulated mountains, and 

 commonly situated in the neighbourhood of those of ba-r 

 saltes- It forms mountains of the hardest kind, and which 

 jiresent the greatest resistance to degradation- It effloresces 

 or»ly at the surface ; and the argillaceous crust which covers 

 it renders these stones very slippery, and of difficult ascent. 



The colour of the sonorous porphyry is gray, sometimes 

 inclining a little to green. It is always compact, rough, split 

 in its fracture. It breaks into thick leaves, very thin frag- 

 ments of which have pellucid edges. Its substance, the 

 grain of which is fine, is very hard and smooth. When rcr: 

 duc( d to powder it is of a gray colour. Its specillc gravity 

 is ■2'5'ib. 



Sonorous porphyry reduce^ into small fragments, an4 

 freed as much as pcss.ble from the leaves of feld-spar and 

 grains of amphibolite disseminated throughout its mass, los^ 

 3 per cent, of its weight by calcination. Its gray colour be-r 

 t;an>e lighter, but it exocriencqd no other alteration. 



When exposed to a porcelain furnace it fuses into a com-i 

 pact glass. 



A hundred grains of sonorous porphyry reduced to powder, 

 and treated m succession with potash, nuuuatic acid, barytes^ 

 and succinate of annnonia, gave 



Silcx --.___ 



Alumine _ _ _ _ _ 



Lime ----- 



Oxide of iron - _ _ _ 



Oxide of nuiugancse 



fcoda - - _ _ - - 



Water - , . - - 



98-10 



"^ Th«» 



