Silicious Deposit. 



145 



low, at the period when the rocky beds were thrown iBto their in- 



Musk 



ingum river 



We 



water, from the imbedded animal remains, found through its whole 

 length, and also that these are marine shells, and of course lived in 

 salt water. Mr. Bakewell, when speaking on the subject of sili- 

 cious deposits, says, "we know no instances in nature, of silicious 

 earth being held in aqueous solution, except in waters of hot or boil- 

 ing springs ; and hence it seems reasonable to infer that many silicious 

 rocks and veins have been deposited from subterranean waters at 

 high temperatures. In other instances, silicious earth, rendered fu- 

 sible by an intermixture with alkalies and earths, may have been 



ocean 



\ 



constlti;pnt parts may have separated and formed granite rocks, com- 

 posed of quartz, feldspar, mica and hornblende. Beds of limestone 

 may have been formed by similar calcareous eruptions, in which 

 the lime was sometimes in solution^ and sometimes mechanically 

 suspended. Nor is it necessary to suppose, that these aqueous 

 eruptions were always sudden, and attended with violent convul- 

 sions; for when a passage was once opened, they may have risen 

 slowly, and been diffused in a tranquil state, and by gradual conden- 

 sation, may have enveloped the most delicate animals and vegeta- 



bl 



es, without injuring their external form. 



The long intervals of 



repose, between these aqueous eruptions, saturated with mineral 

 matter, may have allowed time for the growth and decay of animals 

 whose remains are found in different strata, whilst the formation of 

 others may have taken place under circumstances incomnatible with 



and accordingrlv we find In the rocks 



or 



never occur. The same 



animals 



mmeral matter without injuring their external form, appears in some 

 instances to have immediately arrested vitality. Petrified fish have 



very 



been discovered 



tude of seizing and swallowirig their prey.* A sudden eruption of 



mo- 



nient, the animals previously existing, and form around them a sili- 



♦ Mr. Bakewell examined the celebrated specimen here alluded to, which is 

 in one of the museums of Paris, and concluded that the heads of the fishes were 



merely pressed against each other. — Ed. 



Vol. XXIX.— No. 1. 



19 



