13 



solid, still entirely surrounded by a gigantic dense atmosphere of 

 whirling vapours and gases. 



All the enormous amount of water now liquid on the earth was 

 then gas. There came a time when the whole mass had cooled so 

 far that the cold of outer space caused 'rain' to form in the dense 

 clouds that covered the whole earth. At first this rain never touched 

 the earth, it was too hot, but eventually it did reach the solid 

 crust, only to sizzle off at once again as gas. For a long time, 

 probably thousands of years, all over the whole earth it never 

 stopped 'raining', literally pouring, a process which caused quite 

 rapid cooling. One can well imagine that there must have been 

 continual 'storms' of violence undreamt of today. In passing, we 

 may note that at present the main part of our earth is still liquid 

 ^nd very hot under its solid crust. There is, of course, abundant 

 liquid water and the atmosphere of gas. The earth is cooling all 

 the time, and it is steadily losing water and air to outer space. If 

 the earth survives long enough there will come a time in the far- 

 distant future when any water or 'air' that may be left will 

 all be solid. One way and another, life as we know it now, 

 free life on the surface of the earth that needs water and air, 

 can only be a passing phenomenon in the infinite time span of the 

 universe. 



The sciences of Geology and Palaeontology go together and 

 scientists in those fields have divided the time of existence of the 

 earth into different eras, systems, and periods, which have for 

 convenience been given names. 



The table overleaf (p. 14) giving a Geological Time-scale is a 

 summary of what is more or less generally accepted. 



On the earth there is a sharp distinction between dead, or 

 'inorganic', matter and living things which nobody has yet been 

 able to bridge. The earliest forms of life on the earth were doubt- 

 less preceded by the formation in some fashion of 'organic' 

 matter; that is, non-living compounds containing carbon and 

 other elements essential to living organisms of the type we know 

 on the earth, that in some fashion came to be alive. Nobody has 

 as yet succeeded in pushing any types of non-living 'organic' 

 compounds over the borderline to 'life', but it is not impossible 

 that suitable compounds are constantly being produced in nature, 

 that the transition to living matter may still occur, so that even if 



