Such _barrancas_ and valleys do not, of themselves, indicate either great natural water power or navigable streams. There are wonderful water power possibilities in Mexico, to be sure, which come from two factors, the sheer drops which give ideal power sites with tremendous heads of water, and the heavy torrential rainy season. But the streams themselves do not carry sufficient water the year round to justify any plant, and tremendous reservoir development is vital to any power plant design. Such reservoirs have been built in various parts of Mexico, but at appalling expense, such as only great financial interests can swing--only foreign capital or the government has been able to handle them. There is an added and unexpected element of difficulty--the porousness of much of the soil of Mexico. The mountains, indeed, are of igneous rocks, but underneath the valleys is often soft limestone, and more often still, under those places where a great impounding of water might be made with a relatively low and inexpensive dam, is the soft, porous alluvial and volcanic-ash land with which the valleys have been filled up. This porous soil and limestone are factors bearing on the absence of navigable streams. Even in the lowlands the streams run underground in Mexico, and while they can be tapped by shallow wells, they deprive Mexico almost entirely of the advantages of river transportation. Even the Rio Grande, on the northern border, is useless for navigation most of the year. The Panuco, at whose mouth is located the great oil center of Tampico, is navigable only a short distance above that port. The broad, rich coastal plain along the Gulf of Mexico is watered by tiny streams, all of which, excepting the partially navigable Papaloapam, are useless for steamers and even for launches most of the year. Not until we reach the Isthmus of Tehuantepec do we find a river worth considering for transportation. The Coatzacoalcos, at whose mouth on the Gulf of Mexico is Puerto Mexico (the eastern terminus of the Tehuantepec National Railway), furnishes a highway which made possible the relatively great development of American tropical plantations during the years of peace under Diaz. Its mouth was then the port of loading for great ships, but only by continual dredging was it kept open, and to-day the port is abandoned except for light-draft coasting ships. Further south, emptying into the Gulf at Frontera, is the magnificent system of which the Grijalva and the Usumacinta are the chief streams. Here indeed have plied and in the future will ply great river steamers, for upon the banks of the Usumacinta, at least, are rich oil fields and the fairest farming land in all tropical Mexico. Both the Grijalva and the Usumacinta are magnificent streams, and the latter is comparable, in its majestic volume, to the Mississippi itself. Only the bar at Frontera keeps them from being navigable to ocean steamers. For a brief period under President Madero this bar