20,1 Schenck: Drainage Control by Jointing in Angat 61 
the influence which Hobbs considers predominant in Europe and 
Africa is practically the same as the jointing observed by the 
writer in this locality in the Philippines) and concludes that 
a recognition of such a fracture system “points inevitably to 
the conclusion that more or less uniform conditions of stress 
and strain have been common to probably the earth’s entire 
outer shell.” 
It might be argued that the three factors of drainage control 
discussed herein are perhaps subsidiary to a main control; 
namely, that the entire river is not controlled by jointing, fault- 
ing, and differential hardness of rock, but by other factors such 
as antecedency and superimposition, taking as evidence for this 
stand the general south course of the river and the turn it makes 
to the west later. Another criticism that can well be advanced 
is that not enough territory was covered to gain an idea of the 
entire area. The writer admits the truth of these points, but 
he desires to make it clear that he is convinced that in the small, 
limited district in question northwest-southeast and northeast— 
southwest jointing systems, aided by faulting and hardness of 
rock, control the drainage, and that here this peculiar feature 
is not the result of peneplanation and subsequent rejuvenation. 
