THE DAWN OF LIFE IO5 



this, in the upper portion of the Laurentian, we have regularly 

 bedded rocks, quartzites, limestones, and quartzose, and gra- 

 phitic and ferruginous gneisses, evidently altered aqueous 

 sediments ; but intermixed with other rocks, as diorites and 

 hornblendic gneisses, which are plainly of different origin. 

 Lastly, on the bottom of all, we have nothing but coarse 

 crystalline gneiss, representing perhaps the earliest crust of a 

 cooling globe. Broadly, and without entering into details or 

 theoretical views as to the precise causes of formation and 

 alteration of these rocks, this is the structure of the Archaean 

 or Eozoic system in Canada ; and it corresponds with that of 

 the basement or foundation stones of our continents in every 

 country that I have been able to visit, or of which I have 

 trustworthy accounts. 



In the lower or fundamental gneiss, and in the igneous beds 

 which succeed it, we need not look for any indications of 

 living beings ; but so soon as the sea began to deposit sand, 

 mud, limestone, iron ore, carbon, there would be nothing to 

 exclude the presence of some forms of marine life ; while, as 

 land must have already existed, there would be a possibility of 

 life on it. This, therefore, we may begin to look for so soon 

 as we ascend to those beds of the Laurentian in which lime- 

 stone, iron ore, and quartzite appear ; and it is precisely at this 

 point in the Laurentian of Canada that indications of life are 

 supposed to have been found. Certain it is that if we cannot 

 find some sign of life in the Laurentian or Huronian, we shall 

 have to face as the beginnings of life the swarms of marine 

 creatures that appear all over the globe at once, in the early 

 Cambrian age. 



Is it likely, then, that such rocks should afford any traces of 

 living beings, even if any such existed when they were formed ? 

 Geologists who had traced organic remains back to the lowest 

 Cambrian might hope for such remains, even in the Lauren- 

 tian ; but they long looked in vain for their actual discovery. 



