108 THE DAWN OF LIFE. 



specimens now before me, nothing can be more plain 

 than this entire independence of the shining silky 

 veins of fibrous serpentine, and the fact of their 

 having been formed subsequently to the fossilization of 

 the Eozoon ; since they can be seen to run across the 

 lamination, and to branch off irregularly in lines alto- 

 gether distinct from the structure. This, while it 

 shows that these veins have no connection with the 

 fossil, shows also that the latter was an original 

 ingredient of the beds when deposited, and not a 

 product of subsequent concretionary action. 



Taking the specimens preserved by serpentine as 

 typical, we now turn to certain other and, in some 

 respects, less characteristic specimens, which are never- 

 theless very instructive. At the Calumet some of the 

 masses are partly filled with serpentine and partly with 

 white pyroxene, an anhydrous silicate of lime and 

 magnesia. The two minerals can readily be dis- 

 tinguished when viewed with polarized light ; and in 

 some slices I have seen part of a chamber or group of 

 canals filled with serpentine and part with pyroxene. 

 In this case the pyroxene or the materials which now 

 compose it, must have been introduced by infiltration, 

 as well as the serpentine. This is the more remarkable 

 as pyroxene is most usually found as an ingredient of 

 igneous rocks; but Dr. Hunt has shown that in the 

 Laurentian limestones and also in veins traversing 

 them, it occurs under conditions which imply its depo- 

 sition from water, either cold or warm. Giimbel 

 remarks on this : — '^ Hunt, in a very ingenious 



