2 



University of California Publications in Geology [Vol. 10 



but they contain data and hypotheses of prime importance for the 

 solution of those problems. 



A review of the results of this new work, together with the more 

 reliable and generally accepted conclusions of earlier investigations, 

 show a very remarkable unanimity among the students of separate 

 districts distributed over the entire region. There still remain, of 

 course, certain outstanding differences of opinion over questions of 

 correlation, and particularly as to the use of terms; but if, for the 

 moment, we disregard names and the correlations which they imply, 

 and focus our attention on the great and fundamental fact of sequence 

 of formations and events, an astonishing sameness of result appears in 

 a score of districts where more or less detailed work has been done. It 

 is the purpose of this paper to make use of this similarity of sequence, 

 together with a new hypothesis to be formulated in the sequel, in an 

 effort to correlate in a comprehensive way the geological history of 

 these districts with one another. The result of this effort is sum- 

 marized in the tabulation which accompanies the paper. 



UTILITY OF TENTATIVE CORRELATIONS 



Some writers, notably Collins 1 of the Geological Survey of Canada, 

 incline to the view that we can make real progress only by abandoning 

 for the present all effort at a general classification of the pre-Cambrian 

 formations and concentrating our attention on particular sections 

 which are favorable for study, and which are near enough to permit 

 of sure correlations from one to the other ; and so gradually widen an 

 area within which a classification may be established unvitiated by 

 the errors of distant correlation. 



This policy as voiced by Collins is a safe one for the survey to lay 

 down, and if pursued consistently will undoubtedly lead to positive 

 results. It is a matter for congratulation that we have this prospect of 

 close and detailed work on the part of the Canadian geologists, and it 

 is to be hoped that more men will engage in it. In the vastness of the 

 pre-Cambrian terranes of Canada and the multiplicity of problems 

 which they present, there is every justification for the survey devoting 

 more of its energies to this field. 



But the method advocated by Collins, while most commendable, is 

 not the only one which will contribute to the solution of the general 



i A classification of the pre-Cambrian formations in the region east of Lake 

 Superior, Congres geologique international, 1913. 



