LAURENTIAN SYSTEM. 155 
formed. Because they seem to contain no fossils, they have also been called 
the Non-fossiliferous rocks ; but this assertion of the absence of organic 
remains is not to be taken as final, because in them fossils may yet be 
discovered, as they have been in the upper beds, which have lately been 
formed into an independent system. The existence also of plumbago in 
these rocks, the lead-like mineral used for pencils, which is a kind of coal, 
and may therefore have been formed of vegetable matter, seems to shew 
the likelihood of future organic discoveries. 
Scenery.—Regarding the scenery of this early epoch, we can form only 
the dimmest conception. After the intense heat of the primitive granite 
had subsided, and the once molten mass seems to have become hard and 
solid as we now see it, a system of things appears to have begun, bearing 
more likeness to that now existing. Granite mountains reared their 
heads, great seas rolled their billows, while rivers flowed across the plains, 
conveying to the ocean-floor the débris of the granite continents. Such 
organic life as then existed, if it did exist at all, has either been totally 
destroyed by the great heat of the granite surface, or remains yet to be 
discovered. 
Ii—Laurentian System. 
Description.—Immediately above the Non-fossiliferous Metamorphic 
rocks lie the lowest of those that contain fossils. These have received 
the name of the Laurentian System, from their great development on the 
shores of the St Lawrence, in Canada. It was only quite lately, in the year 
1863, that these rocks were grouped into a distinct system, from the dis- 
covery in them of certain fossil remains in Canada, having previously 
been reckoned Metamorphic. The Laurentian System consists of certain 
schists, quartzose rocks, and limestones, all very highly crystallised—only 
little less so than the Metamorphic rocks. They contain no sandstones or 
shales, that occur so frequently in higher formations, such of these as once 
existed having been changed by heat. Even the limestone is unlike the 
limestones that occur higher up, being very highly crystallised. The 
rocks, however, are all truly sedimentary, deposited under water, and 
have received their present aspect mainly through the agency of heat. 
They are found in Canada, the Hebrides, Ireland, and Norway and 
Sweden. 
Organic Remains.—The discovery of the fossil remains that caused these — 
rocks to be formed into a separate system, was made in Canada, and 
excited interest amongst geologists, because belonging to a period when 
organic existence was thought impossible. The organism discovered 
received the name of the Canadian Eozdon! or Dawn-animalcule, and 
1 From Greek 26s, dawn, zdon, an animal. 
