DEFORMATION OF ROCKS 353 
the same direction, 1s they so frequently were. But the discord- 
ance may be more easily discovered if the second movement was 
in a different direction from the first, so that the first folds of the 
lower formations become complexly folded at the second period 
of folding, the newer formations at the same time being simply 
folded. 
Third, in more complicated cases the lower formations were 
folded one or more times before the upper series was deposited, 
and after the deposition of the latter the two series were again 
folded in a complex fashion, either by a single orogenic move- 
ment or else by successive movements. In proportion as the 
folding of the later formations becomes complicated the criterion 
of folding for separating series is more and more difficult to 
apply, and where the folding of the upper formations is at all 
intricate it is usually of little value. The criterion of folding 
for separating uncomformable series is to be considered in all 
cases in connection with other criteria. 
GPRe VANE Ets 
