102 EVOLUTION OF THE EARTH 



what they are at present. At such a time, as now, dis- 

 charges of lightning passing through the damp air produced 

 ammonia and oxides of nitrogen, which were carried down by 

 rain into the streams and pools. If this process went on un- 

 modified, the result would be a large accumulation of nitrogen 

 compounds in the terrestrial waters, which would also contain 

 carbon dioxide probably in larger amounts than the waters of 

 the present day, because since that time much carbon dioxide 

 has been withdrawn from the air and water and locked up in 

 organic matter. In the same waters the usual metallic ele- 

 ments, in the form of chlorides, sulphates, phosphates, etc., 

 would also be present. 



Thus there must have been brought together an abundance 

 of such raw materials as are required for the production of 

 living matter, and, provisionally, Allen imagines some such 

 reactions as the following to have occurred: solar energy, 

 acting on the water or damp earth containing the raw materials 

 just mentioned, caused dissociation and rearrangement of the 

 atoms, the nitrogen abstracting oxygen from its compounds 

 with carbon, hydrogen, sulphur, and other elements and de- 

 livering it to the atmosphere. Not much energy would be 

 absorbed by a transparent liquid; but such actions as the 

 above would occur particularly in water containing compounds 

 of iron in solution or suspension since these compounds would 

 absorb the solar energy. In this way compounds of nitrogen, 

 carbon, etc., accumulated in the water or damp earth; and 

 further reactions, anabolic and catabolic, occurred among them 

 by virtue of the lability of the nitrogen compounds. Life at 

 this stage was of the humblest kind since there were no definite 

 organisms, only diffuse substances trading in energy, and 

 between this stage and the evolution of cellular organisms an 

 immense period probably elapsed. 



Allen questions whether the earliest organisms were able to 

 utilize the energy of sunshine or whether their whole energy 



