132 THE DAWN OF LIFE. 



shells, have contributed to the formation of the Lau- 

 rentian limestones. 



'^3. In the serpentine* filling the chambers of a 

 large specimen of Eozoon from Burgess, there are 

 numerous small pieces of foreign matter; and the 

 silicate itseK is laminated, indicating its sedimentary 

 nature. Some of the included fragments appear to be 

 carbonaceous, others calcareous; but no distinct or- 

 ganic structure can be detected in them. There are, 

 however, in the serpentine, manj minute silicious 

 grains of a bright green colour, resembling green- 

 sand concretions ; and the manner in which these are 

 occasionally arranged in lines and groups, suggests the 

 supposition that they may possibly be casts of the 

 interior of minute Foraminiferal shells. They may, 

 however, be concretionary in their origin. 



^^4. In some of the Laurentian limestones submitted 

 to me by Sir W. B. Logan, and in others which I col- 

 lected some years ago at Madoc, Canada West, there 

 are fibres and granules of carbonaceous matter, which 

 do not conform to the crystalline structure, and present 

 forms quite similar to those which in more modern 

 limestones result from the decomposition of algae. 

 Though retaining mere traces of organic structure, no 

 doubt would be entertained as to their vegetable origin 

 if they were found in fossiliferous limestones. 



^^5. A specimen of impure limestone from Madoc, 

 in the collection of the Canadian Geological Survey, 

 which seems from its structure to have been a finely 

 * This is the dark green mineral named loganite by Dr. Hunt . 



