river-course. This fact, together with the already large size of the Corte at Rio Chico, guarantees a convenient distribution of the locks.
On the Pacific side it is necessary to descend with sixty-three locks from the summit to La Venta de Chicapa, and this must be done in eight miles; the length of development required for one flight will be 20, 160 feet, while the amount furnished by the ground is 42,240 feet, or, as I have said before, no more than two locks need be grouped in flights. Beyond this point, eight locks will be used in a horizontal distance of forty-seven miles.
It will be seen, by comparing jointly the several profiles of the Pacific plains, that in some places embankments will be required to elevate the surface of the canal to its proper grade.
A profile shows the low range of hills at the Salina Cruz Point, but the prominent elevation seen near the ocean can be overcome by an insignificant cut, because the level-line was run upon a ridge, which is at least fifty feet higher than the small valley upon whose western ridge the road has bee built.
I have been unable to obtain a copy of the profile made by Orbegozo, between the Tarifa Pass to the upper lagoon, by way of La Venta de Chicapa; but from recollection, and notes entered in my journal when I exainined these profiles, I have no manner of doubt in stating that the ground descends very uniformly from La Venta to the lagoons, and also that the ascent, though rapid, is quite uniform from La Venta to Tarifa Pass. I have visited this pass three times from opposite directions. The last time I inspected it was from La Venta upward, in company with the chief of the Mexican commission, for the sole purpose of studying the development of the hill-curves and the location of the locks. We found no place where the locks could not be easily placed to advantage, with regard to economy of time and water, even if double locks were built, with a water-pit between them.
Lieutenant-commander Bartlett ran a transit and level-line down the Tarifa Pass, to the point where all difficulties disappear; but pressure from other quarters compelled me to suspend this work, for the more important one of determining the height of Cofradia Pass. This line was to be continued to the ocean after a return from the Corte region; but finding then that the Mexican con missioners were engaged in this work, in order to obtain the greatest possible number of profiles across the isthmus, the height of the summit was determined by way of La Chivela, San Gerónimo, Tehuantepec, and Salina Cruz.
I expect to receive a copy of the La Venta line from the Mexican commissioners, and if it should arrive in time, it will be appended to this report and credited to them.
An inspection of the general map would seem to indicate that high ground might exist on the plains, between the Chicapa and Verde rivers, on the line traversed by the canal; but this is not the case. Masahua Range starts abruptly from a dead level; the Lagartero Hill looks like a huge boat stranded on the beach. The Verde, which looks formidable in the maps, was crossed twice near Cofradia without knowing it, though looking sharply for its bed.
The Juchitan River is the only one that deserves special mention, because it will require to be spanned over by the canal; but its floods are powerless The south slope of
