itive engineering. It, with its
canal, has been in mind for at least two years; but it was completed
only in 1903. The dam is small, extending only half way across the
river, and beginning on an island. This dam turns water into a canal
averaging 3 feet wide and carrying about 5 inches of water. The
canal, called "a'-lak," is about 3,000 feet long from the dam at A
in Pl. LVII to the place of discharge into the level area at B. For
about 530 feet of this distance it was impossible for the primitive
engineer to construct a canal in the earth, as the solid rock of
the mountain dips vertically into the river. About fifty sections
of large pine trees were brought and hollowed into troughs, called
"ta-la'-kan," which have been secured above the water by means of
buttresses, by wooden scaffolding, called "to-kod'," and by attachment
to the overhanging rocks, until there is now a continuous artificial
waterway from the dam to the tract of irrigated land.

Considerable engineering sense has been shown and no small amount of
labor expended in the construction of this last irrigating scheme. The
pine logs are a foot or more in diameter, and have a waterway dug
in them about 10 or 12 inches deep and wide. These trees were felled
and the troughs dug with the wasay, a short-handled tool with an iron
blade only an inch or an inch and a half wide, and convertible alike
into ax and adz.

There seems to be a fall of about 22 feet between A at the upper
dam and B at the discharge from the troughs.[24] This fall in a
distance of about 3,000 feet seems needlessly great; however, the
primitive engineer has shown excellent judgment in the matter. First,
by putting the dam (upper dam) where it is, only half the stream had
to be built across. Second, there is a rapids immediately below the
dam, and, had the Igorot built his dam below the rapids, a dam of the
same height would have raised the water to a much lower level; this
would have necessitated a canal probably 10 or 12 feet deep instead
of three. Third, the height of the water at the upper dam has enabled
him to lay the log section of the waterway above the high-water mark
of the river, thus, probably, insuring more or less permanence. Had
the dam been built much lower down the stream the troughs would have
been near the surface of the river and been torn away annually by
the freshets, or the people would be obliged each year to tear down
and reconstruct that part of the canal. As it no