302 OKIGIX OF CEYSTALLINE ROCKS. [XIII. 



aerolites, not to mention the hydrocarbonaceous matters which 

 they sometimes contain, tells us in unmistakable language that 

 these bodies come from a region where vegetable life has per- 

 formed a part not unlike that which still plays on our globe, 

 and even leads us to hope for the discovery in them of organic 

 forms which may give us some notion of life in other worlds 

 than our own." *] 



Bischof had already arrived at the conclusion, which in the 

 present state of our knowledge seems inevitable, that " all the 

 carbon yet known to occur in a free state can only be regarded 

 as a product of the decomposition of carbonic acid, and as 

 derived from the vegetable kingdom." He further adds, " liv- 

 ing plants decompose carbonic acid, dead organic matters 

 decompose sulphates, so that, like carbon, sulphur appears to 

 owe its existence in a free state to the organic kingdom." t As 

 a decomposition (deoxidation) of sulphates is necessary to the 

 production of metallic sulphides, the presence of the latter, not 

 less than that of free sulphur and free carbon, depends on 

 organic bodies; the part which these play in reducing and 

 rendering soluble the peroxide of iron, and in the production 

 of iron-ores, is, moreover, well known. It was, therefore, that, 

 after a careful study of these ancient rocks, I declared in May, 

 1858, that a great mass of evidence "points to the existence 

 of organic life, even during the Laurentian or so-called azoic 

 period." $ 



This prediction was soon verified in the discovery of the 

 Eozoon Canadense of Dawson, the organic character of which 

 is now admitted by most zoologists and geologists of authority. 

 But with this discovery appeared another fact, which afford* -d 

 a signal verification of my theory as to the origin and mode of 

 deposition of serpentine and pyroxene. The microscopic and 

 chemical researches of Dawson and myself showed that the 

 calcareous skeleton of this foraminiferal organism was filled 



* The Chemistry of the Earth, 19, in the Report of Smithsonian Insti- 

 tution for 1869. 



t Bischof, Lehrbuch, 1st ed., II. 95; English exL, I. 252, 344. 

 + American Journal of Science (2), XXV. 436. 



