Viii PREFATORY NOTE 



To the one, these residues are essential to the life and well- 

 being of man through* furnishing the soils from whence is 

 derived directly and indirectly the food for life's sustenance; 

 to the other they are but transitory phases in the earth's his- 

 tory, representing the materials from which, through a process 

 of fractional separation by running waters, have been made 

 up the thousands of feet of secondary rocks which to-day 

 occupy so large a portion of its surface. 



The very general scheme of classification adopted in the 

 treatment of the unconsolidated clastic materials may at first 

 seem disappointing. It was, however, the writer's aim to in- 

 troduce into the preliminary volume as few new terms as pos- 

 sible, to use only those which through years of service have 

 become a part of the language. It is of course possible that in 

 his desire to avoid any possible confusion such as might arise 

 through putting forward a purely tentative classification he was 

 overcautious. 



It is possible, further, that in numerous instances it may 

 appear that too much reliance was placed upon single analyses, 

 particularly in the discussions relating to the character of 

 decomposed material. Kegarding this it can only be said that 

 in those instances upon which most reliance was placed, the 

 materials were not merely collected by the author himself, but 

 that he made his own chemical analyses and microscopic deter- 

 minations as well. It is believed that the fresh and residual 

 materials examined were in each instance as truly representative 

 of the same rock mass, as would be samples of fresh rock col- 

 lected equal distances apart. In all cases special effort was 

 made to obtain material concerning the lithological identity 

 of which there could be no doubt, and in the majority of eases 

 the residuary matter was collected from positions immediately 

 overlying the still unaltered rock. Where such a procedure 

 was impossible, especial care was exercised to obtain only such 

 as was originally of the same lithological nature as the fresh 

 rock, and which had suffered no contamination from extrane- 

 ous sources. The fact that stratified rocks are likely to vary 



