14 Causes and Course of Organic Evolution 



as great as for all of the latter, or in rough numbers a period 

 of 50 millions of years. Even if a shorter time interval be 

 conceded, the period must have been a long-extended one. 



All evidence then points to the conclusion that during the 

 mid- and later archsean epoch extensive areas of land and fresh 

 water existed; that many and varied inorganic compounds — 

 in which could be traced all of the elements now entering into 

 organic bodies — were undergoing extensive and manifold pro- 

 cesses of synthesis and analysis; that stimulating conditions 

 for molecular union, due to frequent volcanic activity, to 

 favorable atmospheric surroundings, to abundant chemical 

 compounds, and to rich supplies of energy, were Tsddespread 

 and in active operation; and that the epoch represented a 

 distinct phase in evolutionary progress which formed a link — 

 alike physical and chemical — between a more primitive and 

 a more evolved state, in a continuous line of progressive change. 



It is important also to emphasize here that in the process 

 of transition from the nebulous through the astral to the solid 

 sta^te of the earth, while some elements like hydrogen, oxygen, 

 and nitrogen persisted largely during the archsean and on 

 even to the present day as gaseous elements, gradual coohng 

 and condensation of others, and of the earth's mass, had given 

 rise to compound gases, to the abundant liquid water, and 

 still further, as well as gradually, to numerous solids. These 

 were built up, stage by stage, of binary, ternary, and to a less 

 extent of quaternary unions of elements, that not infrequently 

 suggest a neat and orderly progressive evolution of them with 

 advancing age of the earth. 



We may now appropriately study the minute arrangement 

 of the atoms and molecules, which by gradual chemical com- 

 bination gave rise to the earth's constituent bodies, since they 

 will have most important relations to subsequent studies. 



Almost all of the substances that made up the foundational 

 or igneous, and the later or archsean, rocks showed that ar- 

 rangement of the atoms and molecules which has been termed 

 crystalline. This is evidently the most primitive, as well as 

 the most stable, condition of inorganic bodies, and crystalli- 



