NO. 5 STUDY OF CITEMICAL DENUDATION — CLARKE 19 



exist in it, and was possibly, in early geologic periods, leached into the 

 ocean in large amounts. Its iron would be precipitated by the alkaline 

 carbonates of river waters, while chlorides of the alkaline metals were 

 produced. Dr. Becker, however, inclines to regard deeply buried lawrencite 

 as the origin of volcanic chlorine, and it is possible that the great mass of 

 this ferrous chloride underlay the specifically lighter primeval rocks. It 

 is also conceivable that the earliest crystalline rocks were richer in easily 

 decomposable minerals like sodalite than the surface rocks of to-day, and, 

 therefore, added more chlorine to the ocean than is leached into it now. 

 Such rocks, if they existed, would be more rapidly eroded than the less 

 soluble species, and, consequently, less abundant at the present time. A 

 primitive atmosphere, rich, in chlorine, and an ocean of weak hydro- 

 chloric acid may have once existed, but their assumption is by no means 

 necessary in order to account for the known facts. 



This memoir is entitled " A Preliminary Study of Chemical Denuda- 

 tion." It has been written in order to make existing data more available 

 for discussion, and to point out the deficiencies in our knowledge. If it 

 stimulates investigation; if it leads others to the examination of the 

 greater Asiatic, African, South American and Australian rivers, or to 

 more extended studies of the chemistry of rainfall, its main purpose will 

 be fulfilled. The assumptions which it is now necessary to make ought to 

 be replaced by definite evidence of a sort which is easily obtainable.^ 



1 Publislicd by permission of llie Director of Iho United States Geological Survey. Becker's 

 memoir, to wliich references have been made, appi'ars simuUaneously with this paper. 



