Page:Vol 6 History of Mexico by H H Bancroft.djvu/694

674 when they reach Juchitan. Small culverts along the canal-line in the area covered by the river-floods will overcome this obstacle. These same circumstances obtain in the Tehuantepec River, but in a lesser degree, since this river now runs through a permanent channel, which it was said the river excavated for itself; but while studying the regimen of this river, I ascertained that the witchcraft attributed to this peaceful stream arose from ignorant tinkering with its waters, for irrigation purposes. A trench had been dug unprotected below the flood-line, and the river found an outlet over soft ground to the old sunk turnpike, which was washed away, and ever since kept by the river for its bed.

The highest floods of the Tehuantepec River never reach fifteen feet above its bed. An inspection of profile will show that there is no difficulty in crossing over the stream.

. — On the Atlantic side of the isthmus there is a natural, well-protected harbor, made by the banks of the Coatzacoalcos. The harbor varies its depth, but from its entrance to the island of Tacamichapa it can easily be deepened to twenty-two feet.

Between the harbor bar and Minatitlan, the river is very deep, with but five exceptions; viz., at the harbor entrance; near the southern ends of the islands of Guerrero and Diablo; and at the points of confluence of the streams Tierra-Nueva and Camarones. This last point is deep enough, but quite narrow. All these bars but two can be removed without much expense, owing to the nature and extent of the deposits, which are sand and gravel, under twenty feet of water. The narrow Uspanapa Bar is covered by eighteen feet of water at low tide. It is made by deposits from the latter river. The Coatzacoalcos is very deep above and below the point of confluence.

Piles driven on the Uspanapa, or a partial damming of the river, will cause the sands to deposit farther up stream, on its own bed.

With the exception mentioned above, the river varies from twenty-two to eighteen feet in depth in the old as well as in the Kansas channel. The latter channel was discovered in 1871, by the hydrographic party.

The length of the whole trunk is twenty-one miles, counted from the centre of the harbor bar to the Minatitlan custom-house.

The Coatzacoalcos Bar. — This bar has been often surveyed, and its depth, condition, and geographical position have been variously stated by different observers.

A period of twenty-three years has elapsed between the surveys, and in that time the following changes have taken place:

1. The channel at the mouth of the river retains its depth of forty feet, but it is now twice as long as it was in 1848.

2. The horizontal distance between the 40 and 18 foot curves has been elongated one and a half times; but now the channel is narrower.

3. The first contour curve, returning upon itself, and limiting the southern edge of the bar, has receded toward the sea one tenth of its original distance, as counted from the deepest part of the river abreast of the old fort; but vertically over the place of this curve there are now four feet more of water.

4. The width of the bar has not altered sensibly, and is now generally four or five feet deeper.