PROBABIUrrES AS TO LAURENT, AN LIFE, AND 

 CONDITIONS OF ITS PRESEKVATION 



W^ have seen that the mineral constitution of 

 the Upper Laurentian affords evi<ience that 



m th,s age there were already land and water, and 

 that the processes by which the land is beinj; ,v„rn 

 down, and its materials deposited on the sea-bottom 

 were in full operation ; while the absence of any 

 evidence of violent wave-action, and the presence of 

 thick deposits of limestone, coaly matter, iron ore 

 and fine-grained beds of sediment, indicates a time' 

 of rest and quiescence. All these conditions were 

 favourable to the presence of life, and we should 

 expect to find in such a period some sign of its 

 commencement. 



But here we are met by a formidable difficulty 

 If the beds of the Grenville series were originally 

 <lepos,ts in a quiet sea, they are, as now existing in 

 the old Laurentian hills and valleys, very much 

 changed from their original condition. They have, 



