A discussion of the nature of geographic and climatic control of sedimentation has been previously made by the writer in order that the origin of certain specific formations might be dealt with, and the present paper on the interpretation of the Mauch Chunk follows these previous articles in logical sequence,†
The first part of the present paper consists of a presentation of the significant facts of the Mauch Chunk shales, gathered both from the literature and from personal observation. The second part deals with the interpretation of these facts. Where a new view is to be proved the observational and inferential portions should be strictly separated, but at the same time the purpose for which the facts are presented should be evident when they are given. I t is therefore desirable to state in advance the conclusion finally reached, . . .