Theory of Formation of Sedimentary Deposits. 113 



ations which he has found within the district under 

 discussion — to read the history told by its fauna or flora, 

 whether of land or sea — and upon this foundation to con- 

 struct a more or less elaborate account of the history of 

 the region and to outline the various changes that it has 

 undergone. There are many well recognized and generally 

 accepted criteria, for the most part based on the study of 

 present geologic process, by which the history of any 

 region may be inferred from the nature of the deposits 

 found within or adjacent to its boundaries, and from the 

 character of the fossil remains which they contain. A 

 primary pre-requisite to the interpretation of any sedi- 

 mentary series must necessarily be a knowledge of the 

 conditions under which the given series may be produced. 

 The formation of sedimentary deposits under what may 

 be termed normal conditions is a function of many varying 

 factors and it not infrequently happens that similar 

 formations may be produced in two localities at the same 

 time, or in the same locality at different times, by a totality 

 of conditions in each locality, although the factors con- 

 tributory to their production were not precisely alike in 

 the two places, or at the two different times. 



The general conception of the origin of sedimentary 

 deposits, and of the relations of the various types of 

 deposits to each other, which is set forth in this paper, is 

 one which has been long and widely entertained. In re- 

 stating what has so long been generally held, the writer 

 has but repeated the work of others. The method of 

 presentation varies somewhat from that usually adopted 

 in that it is deductive rather than inductive. The paper 

 is offered rather as an illustration of the application of the 

 deductive method to geologic problems than as a direct 

 contribution to our knowledge. In the latter part of the 

 paper direct application of the inferences from the study 

 is made to two minor problems of local interest. In the 

 present paper the writer attempts to present the subject 

 in a systematic manner, and in so doing to lay special 



