412 e. w. shaw the study of sedimentary deposits 



Objects of Eesearch 



The main reason for studying the physical or any other characters of 

 sedimentary deposits is to acquire knowledge^ useful for practical and 

 scientific purposes, on two general subjects, namely, paleogeography and 

 present geography. We are all striving to meet the definite need of a 

 better understanding of both the history of the earth and the present 

 activities of natural forces. The two subjects are complementary and to 

 a certain extent mutually dependent, but full knowledge of one will not 

 supply or relieve the need of knowledge of the other. Even the old dic- 

 tum of the present being the key to the past must be used with caution, 

 for the conditions of the present were not exactly duplicated during for- 

 mer epochs. 



The studies should obviously include many of direct economic bearing, 

 some of probable economic bearing, and a few of no evident practical use. 

 Studies of the physical properties of present-day sedimentary deposits 

 and of the physical processes involved in their formation and modification 

 are applicable in problems of river and harbor improvement; valuable 

 deposits of gravel, sand, clay, salts, greensand, guano, etcetera ; culture of 

 sea foods; water supplies and sanitary problems; military problems; the 

 silting up of reservoirs; swamp and desert reclamation; hydraulic engi- 

 neering projects ; and land title and political boundary questions, such as 

 often depend on the processes of accretion and avulsion. The economic 

 value of the study of ancient sediments lies in the determination of the 

 origin, mode of accumulation, and extent of various kinds of mineral de- 

 posits, including underground water supplies, and the relation of struc- 

 ture and texture to bearing value and durability. The results have other 

 economic applications that serve very properly as an added attraction to 

 the investigator. _ 



Concerted Efforts 



Perhaps rapid progress in sedimentary rock petrology is retarded not 

 because of lack of able investigators, or lack of interest, or lack of ma- 

 terial with significant features, but because of the difficulty of making 

 progress that can be coordinated. When a geologist goes to the field and 

 studies certain sedimentary formations, he notes the kinds of rocks, makes 

 a more or less accurate and expressive description of their physical char- 

 acter, their stratification, color, thickness, granularity, etcetera, but a 

 large number of more or less obvious features are undescribed because 

 the descriptions are of no apparent value. What a difference there would 

 be in procedure if the geologist knew that if he observed and noted, for 



