236 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1915. 



discoveries that helped to show how very much earlier life was de- 

 veloped on our planet than we had previously supposed. These re- 

 searches have taken into consideration the records left on all the 

 continents and many of the great islands. The Cambrian rocks of 

 China and their included traces of life were compared and reviewed ; 

 the problem of the abrupt appearance of the Cambrian fauna on the 

 North American continent was considered; comparisons were insti- 

 tuted from measurements of sections in the Cordilleran and Appa- 

 lachian regions of the United States and Canada, including the Bow 

 River Valley of Alberta, and the Robson Peak and Mount Burgess 

 districts of British Columbia, where peculiarly rich fossil beds were 

 discovered; more recently certain horizons of the Cambrian forma- 

 tions of the Mississippi Valley were discussed with their faunas, 

 followed by the study now in hand of pre-Cambrian Algonkian 

 traces of life. 



In these inquiries I have had generous assistance in obtaining col- 

 lections and exchanging publications with students all over the world, 

 including geologists, paleontologists, zoologists, and paleobotanists 

 in America and Europe and in far-away outposts of China, Siberia, 

 India, Australia, and New Zealand. 



Field work, with compass, hammer, and chisel, has been the rule, 

 followed by laboratory and critical comparison of many thousands 

 of specimens of fossil genera and species of ancient marine life, and 

 often study of microscopic sections of rocks and fossils in the hope 

 of finding evidence of the presence of minute and active bacterial 

 and simple algal workers, such as exist in modern seas and lakes, 

 which by their united efforts form great masses of the recent sea and 

 lake deposits. 



PRE-CAMBRIAN ALGONKIAN NORTH AMERICA.* 



In North America, with its great epicontinental formations, the 

 Algonkian era, between the inchoate Archean and the well-defined 

 Cambrian, was a time of continental elevation and largely terrigenous 

 sedimentation in nonmarine bodies of water, and of deposition by aerial 

 and stream processes in favorable areas. Marine sediments undoubt- 

 edly accumulated in the waters along the outer ocean shores of the 

 continent, but they are unknown to us, and great quantities of erup- 

 tive matter were extruded into the central Lake Superior region 

 (Keweenawan). The agencies of diastrophism exerted their influ- 

 ence throughout this long period, though with decreasing energy, 

 until they became practically quiescent during the latter part of 

 Algonkian time. 



1 Problems of American Geology, Yale Univ. Press, 1915, pp. 166-167. Walcott : The 

 Cambrian and its problems. 



