EDITORIAL. 
A PHILIPPINE NATURAL BRIDGE. 
In July of 1910, while making a geological reconnaissance 
in the vicinity of Silang, Cavite Province, P. I., the writer dis- 
covered a natural bridge of unusual size, and owing to its remote- 
ness it is probable that the place had not previously been visited 
by white men. It is noteworthy that this is the first large natural 
bridge reported in the Philippines, although it is likely that 
future explorers will find others, especially in the great bedded 
tuff area lying between Manila and the Gulf of Tayabas where 
the rock is favorable for their formation. 
The bridge is on the Lucsuhim stream about 3 kilometers west 
of the barrio of Silang, and 50 kilometers south of Manila. It 
can be reached from Silang by following the Silang-Indang road 
for about 3 kilometers, to the barrio of Lucsuhim and then strik- 
ing northwest across the fields for about 2 kilometers until the 
canon of the Lucsuhim stream is reached. The opening under 
the bridge span is tunnel-like and has a diameter of about 10 
meters and a length of about 75 meters. It makes a double turn 
that roughly approximates the shape of the letter S. During 
low water the stream occupies a central channel consisting of 
a staggered series of small falls and potholes which are the 
result of the action of the water upon the horizontal bedding of 
the tuff rock. 
The floor of the bridge, which is about 40 meters above the 
stream, was examined and showed evidence of once having 
formed the bed of the stream. Erosion has nearly obliterated 
this old bed, but it has not been sufficient to destroy the sides of 
the valley. At one time the river must have flowed at this 
higher elevation to a place several kilometers down stream from 
the present tunnel and then passed over a cliff. This cliff grad- 
ually receded upstream forming the present box-cafion. As 
illustrated by the sketches (fig. 1), seepage began at a point 
several hundred meters above the falls and, owing to the hori- 
zontal bedding of the rock, it first took a path at right angles 
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