1 16 The American Geologist. Au*i»t, 1905 
ranges, not once, but repeatedly. Finally before the Cam- 
brian strata of the region were deposited the entire country, 
already profoundly folded, faulted and cut frequently by in- 
trusives was planed down to a prodigious extent. On this 
new peneplane only isolated patches of the clastic rocks of 
Proterozoic age survived — only those portions caught in the 
lowest parts of complex troughs, the bottom of synclinoria. 
These remnants of the Proterozoic sedimentaries now ap- 
pear so intensely metomorphosed that they have until quite 
recently entirely escaped notice. At best it is only with 
the greatest difficulty that the rocks of the two great ages 
can be differentiated. 
In many of the mountain ranges the crystalline base- 
ment is composed partially or entirely of gray or red gran- 
ites which show little or no evidences of shearing or sub- 
jection to great oroganic pressure. It has been customary to 
regard these masses as composed of Archaean granite. Now 
granites of this description, practically unaltered, are known 
to traverse or be intimately associated with the undoubted 
Proterozoic crystallines. On the principles involved in the 
separation of unfossiliferous geological formations accord- 
ing to the relative amount of deformation and comparative 
degree of metamorphism, these unaltered granitic masses 
are tentatively referred to the Proterozoic, though for con- 
venience in treatment some of them probably have to be 
considered for. the present in connection with the other 
rock-masses in which they occur. 
At some risk, perhaps, in the present state of our 
knowledge, of swinging too far in the direction opposite to 
that heretofore generally accepted, it seems most advan- 
tageous to proceed on this hypothesis. In support of this 
position there are many other reasons which should be fully 
discussed in connection with the detailed descriptions of the 
Proterozoic crystallines. For the present only those crys- 
talline rock-masses will be considered as belonging to the 
Archaean fundamental complex, that consist of much 
sheared granites, crumpled gneisses and schistose rocks not 
associated with undoubted elastics. 
Probably the main reason for the lack of definite and 
discriminating information regarding the pre-Cambrian 
