204 REPORTS ON INVESTIGATIONS AND PROJECTS. 



GEOLOGIC RESEARCH IN CONTINENTAL HISTORIES. 



Bv Bailey Willis. 



PLAN OF RESEARCH IN PALEOGEOGRAPHY OF NORTH AMERICA 

 AND EURASIA AND SUBSEQUENTLY OF SOUTH AMERICA, 

 AFRICA, AND AUSTRALIA. 



The problem. — To determine the geographic condition of each 

 continent at successive geologic epochs, from pre-Cambrian to 

 Quaternary, and thus to arrive at means of comparison of continental 

 histories. 



The argument. — A geographic condition (i. e., the distribution of 

 sea and land — the height of land and depth of sea, ocean currents, 

 climate, and allied phenomena, including organic life) is a transient 

 phase of the features of the world ; it may be considered as a fixed 

 geographic state for an)'- brief period only, but is and always has been 

 subject to change. The energy which initiates that change is the 

 earth's internal energy ; expressed in superficial warping, it modifies 

 the position of sea-level, causes migration of coasts, and changes 

 heights and depths. Two processes depend upon warping, namely, 

 erosion and sedimentation. Erosion, the destructive process, leaves 

 only a transient record on land ; but sedimentation, the constructive 

 process, records the geographic facts. These processes have inter- 

 acted continuously since an early geologic period, and the history 

 of their interaction is to be found in strata and associated rocks. 

 Part of the facts are original with the sediments — their distribution, 

 constitution, and contained fossils ; part of the facts are of later 

 development — effects of concentration, folding, and metamorphism ; 

 but given the facts, we can organize, correlate, and interpret them 

 in terms of their causes and conditions. Thus interpreted, they will 

 yield connected views of paleogeography. 



The method. — (a) By organizing the appropriate facts of geologic 

 science, according to lands and times ; (b) by interpreting them in 

 terms of successive geographic conditions ; (e) by delineating the 

 several states of each continent upon maps, which shall be accom- 

 panied by appropriate discussions. 



The meayis. — (a) Studies in geologic literature of all countries ; 

 (b) conferences with geologists, paleontologists, and specialists in 

 allied sciences ; (c) exploratory journeys. 



The result. — A contribution to the geology of the world, as dis- 

 tinguished from the geology of provinces ; an assemblage of facts 

 classified by continents and geologic epochs ; an assemblage which, 



