118 THE DAWN OP LIFE. 



serpentine ; and a serpentine from Burgess has already been 

 mentioned as containing only small broken fragments of the 

 fossil. In like manner large masses of white pyroxene, often 

 surrounded by serpentine, both of which are destitute of traces 

 of organic structure, are found in the limestone at the Calu- 

 met. In some cases, however, the crystallization of the py- 

 roxene has given rise to considerable cleavage-planes, and has 

 thus obliterated the organic structures from masses which, 

 judging from portions visible here and there, appear to have 

 been at one time penetrated by the calcareous plates of Eozoon. 

 Small irregular veins of crystalline calcite, and of serpentine, 

 are found to traverse such pyroxene masses in the Eozoon 

 limestone of Grenvilie. 



" It appears that great beds of the Laurentian limestones 

 are composed of the ruins of the Eozoon. These rocks, 

 which are white, crystalline, and mingled with pale green ser- 

 pentine, are similar in aspect to many of the so-called primary 

 limestones of other regions. In most cases the limestones 

 are non-magnesian, but one of them from Grenvilie was found 

 to be dolomitic. The accompanying strata often present finely 

 crystallized pyroxene, hornblende, phlogopite, apatite, and 

 other minerals. These observations bring the formation of 

 silicious minerals face to face with life, and show that their 

 generation was not incompatible with the contemporaneous 

 existence and the preservation of organic forms. They con- 

 firm, moreover, the view which I some years since put forward, 

 that these silicated minerals have been formed, not by subse- 

 quent metamorphism in deeply buried sediments, but by re- 

 actions going on at the earth's surface.* In support of this 

 view, I have elsewhere referred to the deposition of silicates 

 of lime, magnesia, and iron from natural waters, to the great 

 beds of sepiolite in the unaltered Tertiary strata of Europe; 

 to the contemporaneous formation of neolite (an alumino- 

 magnesian silicate related to loganite and chlorite in composi- 

 tion) ; and to glauconite, which occurs not 6nly in Secondary, 

 Tertiary, and Eecent deposits, but also, as I have shown, in 



* Silliman's Journal [2] , xxix. , p. 284 ; xxxii. , p. 286. Geology of 

 Canada, p. 577. 



