ANCIENT LIFE ON THE EAKTH IS 



legitimately surmise, about the early history of the 

 earth will help to give us clearer notions on this 

 dictum of a palaeontological base. 



We know as a fact that the earth is a hot body 

 travelling through space which is intensely cold. It 

 must, therefore, be cooling. Consequently, in the 

 early days of its history, it must have been very 

 much hotter than it is now. There are, indeed, 

 reasons for thinking that at a very remote period the 

 earth was actually molten owing to the intense heat, 

 when, of course, the whole of the water of the ocean 

 must have been in a state of vapour, and formed part 

 of the atmosphere. As the temperature lowered, 

 this aqueous vapour would condense and fall on the 

 surface of the earth as hot rain. The first ocean 

 would, therefore, be almost at its boiling-point, and 

 would gradually cool down ; but no life could exist 

 in the ocean or on the land while the temperature 

 much exceeded 200 F., which, so far as we know, 

 is the highest temperature in which plants can live. 

 This period of the hot ocean was, therefore, the 

 Azoic era of the earth's history, which, as the cooling 

 progressed, passed into the Protozoic and then into 

 the Palaeozoic era, which includes the Cambrian 

 period. At first the ocean must have been nearly 

 uniform in temperature from the equator to the 

 poles ; but climatic zones appear to have been estab- 

 lished in the Silurian period, if not earlier. 



The pre-Cambrian rocks have received various 

 names in different parts of the world ; but , as they 

 are better developed and more easy to decipher in 

 North America than elsewhere, it is probable that, 



