CLIMATE AND TERRESTRIAL DEPOSITS l6l 



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 polar zones ? They may be studied most favorably 

 in ancient terrestrial deposits, since these are free from the con- 

 tributory record of the sea, and, as it is the problem of the average 

 climates which it is sought to investigate, it is especially in ancient 

 fluvial and pluvial deposits 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 abundant animal 

 and vegetable life, sealed and protected instead of destroyed, by the 

 making of the succeeding land record. In such deposits the evidence 

 most usually studied is that from the teeth and feet of animal fossils, 

 or the nature 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 structural characteristics of the 

 strata, should be available for the climatic interpretation. The 

 significances of such features have 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 oxi- 

 dized 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 statements have been made without a preliminary 

 investigation into all the possible modes of origin, and it will be found 

 that in the following pages other interpretations are pointed out. 

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

 of the climatic and topographic factors in the making of fluviatile 

 continental sediments. In seeking for data to draw the lines more 

 closely it is found that the relations of climate to the nature of the 

 land waste and river sediments have attracted the attention of rela- 

 tively few explorers and scientists. Such exceptions 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 following articles possible. 



The mode of treatment adopted is to divide the influence of climate 

 upon fluvial and pluvial deposits into three parts : first, the influence 

 on the kind and quantity of the material eroded, allowing for the 



