THE TWO OLDEST TREES 



The term "petrifaction" implies the 

 changing of organic matter into stone; 

 the fact is that the organic matter is 

 replaced by silica in one or other of its 

 various forms. Silica is the oxydized 

 form of the non-metallic element silicon, 

 the chief constituent of the earth's solid 

 crust, and when not mixed with other 

 oxides of other minerals or other color- 

 ing matter, is pure white. 



Silica is found imbedded in limestones 

 anfd other rocks; it has been made for 

 the most part of Diatoms and Spicules 

 of sponges and without any unusual de- 

 gree of heat, and when under water may 

 be dissolved in part, if the water be cold, 

 and then consolidated without external 

 aid by the saline ingredients of the water. 

 By this means, also by parts of spiders, 

 centipedes, worms, fishscales, bones of 

 snakes, etc., etc., we are furnished with 

 a non-metallic element which has made 

 it possible for us of today to view an 



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