292 ANNUAL EEPOET SMITHSONIAN INSTITUTION, 19 3 



also widely varying according to the estimate of age being made 

 on the one principle or the other. If the age of the oceans is esti- 

 mated from their percentage of salts to be 50 to 200 millions of 

 years or from their accession of sediments 35 to 400 millions, we 

 Ftill have no satisfactory knowledge of the time of the water's 

 first appearance. From the disintegration of the radioactive ele- 

 ments the age of a great many different rocks has been estimated. 

 According to such an estimate the age of a rock belonging to the 

 Lower Archaean but younger than the oldest sediments would 

 be 1,300 millions of years. It seems probable to me that 1 or 2 

 milliards of years have passed since the first rains fell on the earth. 

 I shall, however, abstain from any further discussion of this prob- 

 lem, as I can not give any new contribution to its solution. I shall 

 instead draw attention to an attempt to compute the age of the 

 earth at the time of the crust's solidification. Herold Jeffreys at 

 Cambridge published a work in 1924 entitled " The Earth," in which 

 he asserts that the earth's transition from a gaseous mass to liquid 

 form must have taken place in less than 5,000 years. After a further 

 10,000 years or when the earth was less than 15,000 years old, it had, 

 according to the estimates of Jeffreys, a solid crust of such thick- 

 ness that the strong radiation of heat was prevented. It may of 

 course be supposed that a good deal of time had still to pass be- 

 fore the water began to condense, but the quoted figures are undeni- 

 ably amazingly small compared to the millions upon millions of years, 

 by which we compute the age of the following formations. 



Another problem of geological interest is the following: Did 

 the first condensation occur somewhat simultaneously all over the 

 globe, or did it start in certain places, for example at the poles ? In 

 the latter case an essential part of the enormous percentage of 

 water in the atmosphere would be discharged in certain regions. 

 This would no doubt also have left its marks on the sedimentation. 

 If the inclination of the earth's axis toward the plane of the ecliptic 

 was not too small, the condensation was no doubt begun at the poles 

 and in the winter half year. At any rate this ought to have been 

 the case, if the condensation was longest prevented by the radia- 

 tion of the sun and not by the heat of the earth. However, I shall 

 also desist from further discussion of this problem and the possible 

 significance of the distribution of the leptites for its interpretation. 



Then one more problem, the last one : Witli the condensation of the 

 water the development of the organic cells is made possible. We maj'^, 

 without running the risk of being refuted, say that no living organisms 

 existed on the earth before the first rains fell. Water accumulated 

 gradually in large and smaller depressions. It was hot or warm 

 water and, in several basins at least, rather strongly saline (or ac- 



