6 V. G, FESENKOV 



reached 300° from absolute zero. According to Goldschmidt [16], the atoms 

 of uranium and thoriimi cannot (due to their excessive volume) enter into any 

 silicate lattice in the process of crystallization. Therefore, M^hen the deeper 

 parts of the Earth began to solidify, these atoms must have gradually been pushed 

 to the outside and enriched the external layers. In the same way, Holmes [17] 

 assumed that volatile material, extruded from the Earth's interior during cooling, 

 also takes with it radioactive matter. Hence it follows that the radioactive layer 

 during the very first stages of the solidified Earth was extremely thin, and the 

 degree of radioactivity fell sharply with the depth. Thus, radioactivity could 

 never have played a marked role in the thermal history of the Earth. 



The formation of the Earth as a heated cosmic body leads inevitably to the 

 loss of enormous quantities of the original gaseous elements, and all the more so 

 of the entire primordial atmosphere. 



The water of the oceans of to-day must have escaped from the Earth's interior 

 during its cooling stage. The same must be said of the atmosphere which was 

 also formed of gases that accompanied tectonic and volcanic processes. To a 

 great extent, this was water vapour, carbon dioxide, methane, sulphides and 

 also nitrogen, which even to-day is found escaping in certain localities. 



It is known that oxygen in the free state cannot escape from the interior of 

 the Earth. However, a certain quantity of this gas can form gradually by decom- 

 position of water vapour under the action of electric discharges and in the upper 

 layers of the atmosphere due to hard wavelengths of solar radiation. In the 

 lower layers, this gas can exist only in negligible quantities. 



The juvenile water that made up the primaeval waters of the oceans was 

 poorly provided with various mineral salts. Its enrichment with the most diverse 

 elements took place gradually as a result of an irreversible process, an example 

 of which is the water cycle in nature, the constant erosion of the continents by 

 rivers which carry their sediment back to the sea. To a certain extent, a similar 

 process of erosion might take place also at the bottom of the ocean due to the 

 peculiar interaction with the continents, all this leading to the formation of 

 deep, submarine canyons in places that never reached sea level. 



Resulting from the processes of this so-called geological preparation there 

 was gradually formed a water medium enriched with all possible elements that 

 were in a state of easy migration with respect to each other. A mediimi of this 

 kind can promote the generation of life. Without such a medium organic life 

 could not have arisen. 



Thus, in order that life should appear there must be not only a sufficient 

 amount of solar radiation, a water medium, but also an abundance of all possible 

 elements capable of forming all possible compounds. An essential condition for 

 this is that the surface of the planet must be only partially covered by continents 

 and partially by oceans and that here the waters of the oceans might in the 

 course of thousands of millions of years enrich themselves with the products 

 of erosion of the continents. The medium required for the begiiming of organic 

 life could not have formed on a planet like Mars which has never had any open 

 basins of water. 



