BASIS OF PRE-CAMBRIAN CORRELATION 123 
In Professor Van Hise’s presidential address he has referred to the succession 
of the pre-Cambrian rocks in Scotland, Finland, and China as determined by 
Geikie, Sederholm, and Bailey Willis, respectively, and notwithstanding the fact 
that in these successions from one to six unconformities exist, he has in each case 
selected one unconformity as of paramount importance, and correlating this with 
the break at the summit of the Keewatin in North America, has held that these 
various successions support a dual division of the pre-Cambrian rocks which 
he has maintained to be world-wide. He closes his address as follows: “I wish 
to express my firm belief that the dual division of the pre-Cambrian into two great 
groups of rocks [Archaean and Algonkian] seems now as firmly established as 
the division between any other two groups.” I feel, as stated in the paper, that 
in this conclusion an ‘‘unwarranted satisfaction”’ is expressed. 
To sum up, therefore, it seems that the division of the pre-Cambrian rocks 
of Laurentia into two great major divisions—Archaean and Algonkian—is not 
supported by the facts in our possession. The pre-Cambrian succession is 
apparently rather threefold, which three divisions may, for convenience, best be 
designated as Lower, Middle, and Upper (Eo- Meso- Neo-) Proterozoic, quite 
independent of any consideration of the presence or absence of life. 
