900 



SCIENCE 



[N. S. Vol,. XXVIII. No. 730 



the initiation of the chemical synthesis to 

 which is assigned the task of bridging the 

 gap between the inorganic and the organic 

 compounds. 



So far as chemical reactions of the famil- 

 iar inorganic class are concerned, such a 

 stage of earth-growth must obviously have 

 presented conditions favorable to unusual 

 activity, since the contact surfaces between 

 the atmosphere and the hydrosphere, be- 

 tween the hydrosphere and the rock sur- 

 faces, and between the atmosphere and the 

 rock surfaces, were all relatively large and 

 varied, while the temperatures produced 

 by the radiation received from the nebu- 

 lous sun and by the heat of impact of the 

 planetesimal matter may be presumed to 

 have given a varied range of thermal con- 

 ditions. As a result, reactions of excep- 

 tional variety should have been developed. 

 In view of the vast number of bodies of 

 water and their varied contacts with all 

 sorts of rocks, together with the possibili- 

 ties thus presented for the isolation of 

 special combinations in their early stages 

 and the correlative possibilities of con- 

 junctions and minglings of these in their 

 subsequent stages, there may well have 

 resulted numerous diverse chains of 

 sequences. 



At that stage the atmosphere should 

 have held each of its present constituents 

 but probably not in the same proportions 

 as now. The elements of lower specific 

 gravity should have been smaller in 

 amount relatively than at present, while 

 those of higher specific gravity should 

 have been more abundant relatively, be- 

 cause the controlling power of the smaller 

 earth limited the range of molecular reten- 

 tion. Relative to the lighter constituents, 

 it need only be added that, instead of 

 escaping completely from the control of 

 the earth, as postulated in the earlier 

 phases of the doctrine of Stoney, the 

 lighter molecules should in the main have 



escaped merely into the supplementary 

 orbital atmosphere, where they might have 

 persisted for long periods during which 

 they were always subject to being driven 

 back to the earth by occasional encounters, 

 so that, although these constituents may 

 have been rare in the denser coUisional 

 atmosphere near the earth's surface, they 

 were doubtless present in sufficient 

 amounts to have participated in any ap- 

 propriate chemical synthesis. It is to be 

 added further in qualification of this that, 

 with the exception of hydrogen, which 

 might have been derived from its com- 

 pounds, the lighter atmospheric constitu- 

 ents, such as helium and neon, are chemi- 

 cally inert and there is no specific reason 

 for supposing that they entered into any 

 stage of the organic synthesis. The 

 heavier constituents of the early atmos- 

 phere would include the compound gases 

 of carbon, nitrogen, sulphur and phos- 

 phorus. 



During the critical stages of growth, the 

 infalling of planetesimals is supposed to 

 have continued to be active. The plane- 

 tesimals are assumed to have contained 

 carbon, sulphur, phosphorus and all other 

 elements found in organic matter; and as 

 they impinged more or less violently upon 

 the surface formed of previous accessions 

 of similar matter, there should have been 

 generated various compounds of these ele- 

 ments. A portion of these compounds 

 should have been gaseous or vaporous and 

 should have been variously disseminated 

 into the atmosphere, or else absorbed into 

 the waters or into the poroios earthy 

 mantle. The volcanic action of the period 

 should have contributed its characteristic 

 constituents in similar variety of combina- 

 tion. It may therefore be assumed with 

 plausibility that a larger percentage and 

 a greater variety of volatile compounds of 

 the critical class prevailed in the air, sub- 

 ject to absorption into the earth-mantle 



