228 The Philippine Journal of Science 1921 
All faults in the Philippines which the writer has seen are, 
with a few minor exceptions, of the normal type. Thrust fault- 
ing may be present. 
Joints. — One of the commonest features of rock formations 
is jointing. The cleats in coal may be considered as jointing 
on a small scale. Any quarry man is of course familiar with 
the great, regular, smooth-walled cracks which traverse various 
formations for long distances and more or less in definite systems. 
These are both an advantage and a source of trouble. Farther 
on the writer calls attention to the part these play in the building 
of the Benguet road. 
Folds. — The importance of folds in the strata, such as the 
syncline (basin) or monocline in the case of artesian water and 
the anticline (arch) in the accumulation of oil, is well known to 
most people nowadays ; but has it occurred to many people that 
the ease of excavation, or the control of water, causing flooding, 
etc., are dependent upon the attitude of the formations? In the 
Philippines we have the rock strata in all conceivable attitudes, 
each locality presenting different conditions which must be 
studied locally. Of course, in this respect the Philippines and 
the Tropics in general do not differ from many other parts of the 
world. However, owing to excessive vegetation and weather- 
ing these important structural facts are often concealed even 
from the trained eye of the geologist. 
SPECIAL PROBLEMS 
Road building and maintenance. — In parts of the Tropics, and 
particularly in the monsoon region of southeast Asia, the seasons 
are sharply defined, one of practically no rain and one during 
which it rains in torrents. If we recall the rule that the carry- 
ing power of a stream varies as the sixth power of its velocity, 
we know at once we cannot take any chances with a tropical 
torrent. In regions of high relief we have four things to con- 
sider, and we cannot neglect any one of them. They are: 
Declivity or head, sudden increase of volume due to configuration 
of the valleys, the angle of slope of valley walls, and material 
and structure of the valley walls. 
The writer has seen instances where the highway was placed 
in a valley at such a point that the road was continually menaced 
by the stream just below it and by the sliding of material from 
the slopes above. The stream is dangerous because of two 
things: First, because of the sapping of the water itself; and 
