The Scottish Naturalist. 



19 



have played in former ages of the world. The rocks at Quebec 

 are called Laurentian, from the immense extent to which they 

 have been developed on the northern shores of the St. Lawrence. 

 They are now more commonly called Archaean, from being the 

 earliest known sedimentary rocks in the world. Our outer Hebrides 

 are wholly composed of them. The whole of the island of Lewis, 

 the two Uists, Barra, Tiree, Coll, and Iona are composed of these 

 ancient rocks; and the dykes that I saw built close to Quebec were 

 exactly like the dykes in Tiree — the same minerals and similar stone 

 — but in Canada these rocks are developed to an enormous thick- 

 ness. No fossils are found in them, and the question naturally arises 

 was there any life whatever, either animal or vegetable, in the ages 

 during which those rocks were laid down. It is quite possible that 

 there may have been life, that the remains may have been for a long 

 time preserved in these rocks, and that the fossils have been de- 

 stroyed by crystallisation, a process of which we do not know all the 

 secrets, but which certainly was promoted by heat and pressure. 

 Some geologists believe that there was life at the time, and that 

 its remains, cnce abundantly preserved, have since been destroyed 

 by the combined effect of heat and pressure ; and one of the 

 great arguments urged by these geologists, at the head of whom 

 is Sir Wm. Dawson, is that these rocks show all the usual beds 

 found in other rocks that are full of fossils. For example, there 

 are great beds of graphite, and Sir Wm. Dawson argues that these 

 graphitic beds could not have been produced by anything but the 

 fixation of carbon by vegetable life, it being the great function of 

 vegetable life to fix carbon and produce the ligneous textures so 

 valuable to us in domestic use. That may be a sound argument. 

 I do not pronounce upon it ; but if these enormous beds of 

 vegetable organisms existed, what were they? Were they such as we 

 see now in our trees and forests, or were they something much 

 lower in the scale of vegetable life ? That is a question we 

 cannot help asking ourselves, and to which 1 think we have some 

 approach to a clue in the succeeding ages when coal was de- 

 posited. You know that the great mass of our coals is due to the 

 crushed and preserved remains of the cryptogamic flora of the 

 coal period. Very often the vegetable structure is beautifully 

 exhibited, if not in the coal, yet in the shale, and we find that 

 almost the whole of the vegetation, the enormous peat beds and 

 peat mosses which have been hardened into coal, were of the very 



