When abreast of the town of Santa Maria, the feeder, whose general direction has been from east to west, turns now to the south-west to escape the lowlands of the Chimalapa Potrero (or flat lands), searching for the lowest pass between the Chocolate Hill and the Sierra Madre. Since this pass is 160 feet above the summit-level, another tunnel will become necessary at this point. Its length will be 3,550 feet. The streams crossed by this division are a few very insignificant brooklets in the eastern end. The Coqui-pac (Black River), I believe, can be turned into the feeder without difficulty, by simply connecting a small dam and a waste-weir. Its floods are said to be inconsiderable, even when other rivers are much swollen; and this looks plausible on account of the small area it drains. After passing the Chocolate Hill, the feeder will encounter a sort of corrugated soil, forming the bed of many little streams, tributaries of the Coyolapa (Second River) and Escolapa (First River); but they do not complicate the difficulties of the feeder route. The Cuchara (Spoonbrook) is passed near its source. This division ends at the Pita, whose waters have the same height as the summit-level. The excavations of the eastern part of this division are in compact limestones and clays. Drift and shales are found in the Chimalapa Potrero, plastic clay on the Chocolate tunnel, and drift and clay in the western terminus of this division. The length of this division will be eleven and three eighths miles.
Fourth Division. — North of the town of San Miguel, the main chain of mountains sends northward a heavy spur, which, ending at Santa Maria, turned the Corte from its western descent and sent it northward. We have named this spur the Cofradía Range. It is solid, and uninterruptedly high throughout its length, with but two exceptions, at the mouth of the Escolapa and at the Pita Brook. Even beyond the Corte, this range lifts again the last of its many heads, as a huge cone, which Indian wit has named the 'Runt.' I will now explain how this range is traversed by the feeder.
The Corte at Santa Maria is 373 feet below the summit. The Pita, which crosses the Cofradía Range, is at the summit-height, and is, besides, a tributary to the Corte fifteen miles below Santa Maria; therefore, by following the Pita Valley, we can cross the Cofradía Range below the summit-grade, since the Pita runs below this grade. The Chichihua, west of Cofradia Range, was found 71 feet below the summit, and the Pericon is 60 feet above, at the point crossed by the transit-line; hence the feeder must be located about half-way between these last points. The whole route of this division is easily excavated, and consists of clay at the Pita Brook, sandstones in the valley formed across the Cofradia Range, and humus and loose earth in the potreros of Chichihua. The length of this division is eight and three eighths miles.
Fifth Division. — This division comprehends the tunnel from the Otate River to Tarifa Plains.
The only important features of this division is the length of the tunnel, but the excavations can be easily and cheaply made, the ground being very soft. The excavations need not exceed 205,000 cubic yards.
The following table contains a condensed statement of the important features of the feeder:
