CLIMATE AND TERRKSTRIAL DEPOSITS 617 



plete understanding of the history of the earth and its inhabitants. This 

 backwardness is doubtless due to the intangible nature of climate and the 

 lack of direct record of its geologic changes. When it is considered, however, 

 how fundamental are the i-elations of continental deposits to the climates in 

 which they are formed, it is seen that the recoi'd of geologic climates, while 

 indirect and to a considerable extent awaiting interpretation, is nevertheless 

 in existence. This is exclusive of the significance of salt and gypsum deposits 

 on the one hand or of glacial deposits on the other, which are of course 

 universally I'ecognized. but these are the marks of ^limatic extremes. 



The causes of climatic variations as distinct from the stratigraphic record 

 of climates have in recent years received a large amount of attention, with the 

 I'esult that a considerable body of knowledge has taken the place of previous 

 speculation. But what are the geologic records of that great variety of 

 climates which, excluding the desert belts of the world, reach at present from 

 the equator to the frigid zones? They may be most favorably studied in 

 ancient continental deposits, since these are free from the contributory record 

 of the sea ; and, as it is the average climates which it is sought to investigate, 

 it is especially in ancient fluviatile deposits of continental nature rather than 

 in deposits of desert or glacial origin that the record is to be found. In such 

 river deposits each stratum represents an old land surface, the seat of abun- 

 dant animal and vegetable life, sealed and protected by the laying down of the 

 succeeding strata instead of destroyed by erosion, the dominant process acting 

 on the land surface. In such deposits the evidence most usually studied is 

 that from the teeth and feet of animal fossils, or the natui'e of vegetable 

 remains. But many continental deposits are without fossils and many groups 

 of organisms show a wide climatic range; so that it is very desirable that 

 other features constantly present, such as the chemical, textural, and struc- 

 tural characteristics of the strata, should be available for the climatic inter- 

 pretation. The significance of such features has of course not entirely 

 escaped attention ; the presence of red in shales or sandstones is sometimes 

 cited as evidence of derivation from a deeply decayed and highly oxidized 

 regolith, or the existence of a conglomerate whose pebbles are of vein quartz 

 as evidence of the thorough decomposition of an ancient soil ; but such expres- 

 sions have been made without a preliminary investigation into all the possible 

 modes of origin, and it will be found that other interpretations are also 

 possible. 



The problem, then, in the present paper is to separate the influence of the 

 topographic from the climatic factors in the making of terrestrial sediments. 

 In seeking for data to draw the lines more closely, it is found that the rela- 

 tions of climate to the nature of the land waste and river sediments has 

 attracted the attention of relatively few explorers and scientists. Such excep- 

 tions must, however, be noted as Blanford and Oldham, Walther, Hilgard. 

 Merrill, Russell, Davis, and Huntington. These men, with a few others, have 

 largely supplied the data which make the discussion possible. 



The first part, dealing with the relations of climate to erosion, is necessarily 

 largely physiographic, and, in the case of material which is carried long dis- 

 tances by rivers, these relations are of less final influence than the conditions 

 under which the sediments are deposited and those of the preceding transporta- 

 tion. The purpose of the whole paper is, .however, not physiographic, but 



