is,3 Smith: Tropical Geology and Engineering 227 
permanence of the canal. It is not the writer’s intention to allude 
to any of the work of the Canal Commission geologist 4 further 
than to advise any engineer who is working, or expecting to 
work, in tropical regions to give this important work considerable 
study. 
In the Philippines we have the same sprt of structures found 
in many parts of the world with the difference that here some 
of the structures are not only of recent origin but are still in 
the making. Where dynamic forces are at work the engineer 
cannot afford to be off his’ guard or ignorant of how they are 
to be recognized. The builders of the Los Angeles (California) 
aqueduct have very wisely studied and provided against the pos- 
sible breaks which might interrupt that system, having been 
forewarned and forearmed by a geological study of the region, 
a region traversed by long parallel faults in the strata. 
Faults . — In the Philippines there are many faults, some large, 
some small, which every mining man knows about. Does the 
civil engineer know about them ? Can he recognize them ? Are 
they old ones where movement has long since ceased or are they 
fresh and is movement likely to recur, and how will that move- 
ment be manifested ? Which part will move up and which down ? 
Is the fault normal or thrust? It makes a great deal of dif- 
ference which. It can be readily seen that when it comes to rail- 
road tunnels and water mains this becomes a serious matter. 
Cebu Island, for example, is apparently broken by a number of 
faults of considerable size, and it is the belief of some geologists 
that the straits between Cebu and Negros Islands are due to a 
down-faulted block of rock strata. Therefore, the construction of 
engineering works of any size on that island should be preceded 
by careful geologic investigations. As yet the writer knows of 
no engineering projects in the Islands seriously affected by 
faults. 
During a recent geological examination of the area in the 
vicinity of the Montalban reservoir, Dr. R. E. Dickerson sug- 
gested to the writer the possibility of a large fault traversing it. 
If further detailed study of the region should reveal such a break, 
it would be of the utmost importance to the citizens of Manila to 
know it. Possibly, this could not be worked out in less than 
several weeks, but whatever the length of time necessary, it 
would be justifiable. 
4 MacDonald, Donald F., Bull. U. S. Bur. Mines 86 (1915). 
