Page:Vol 6 History of Mexico by H H Bancroft.djvu/691

Rh that the data required to estimate upon the nature of the Tehuantepec Canal trade for water supply purposes can only be approximated after long study and diligent research of uncollected trade statistics at home and abroad, requiring a length of time made impracticable by the nature of our expedition.

The following table will explain the necessity of knowing the amount of trade to estimate the water supply:

Although the estimates made are based upon a trade of about twenty thousand tons crossing the summit daily, they have been made under conditions so exaggerated, that. I believe under ordinary circumstances this canal can accommodate thirty thousand (30,000) tons daily.

I have also distributed the canal trade among small vessels, which will consume a large lockage in proportion to their tonnage, thus: 120 lockages, of 170 feet length, for vessels of 200 tons and under; 20 lockages, of 218 feet length, for vessels of 500 tons; 5 lockages, of 320 feet length, for vessels of 1,000 tons. These conditions will require special machinery to attend to the rapid demands upon the gates.

The following table establishes a comparison between the water dimensions and water supply estimates of the Caledonian Canal; the ship-canal proposed through the Isthmus of Panamá by the engineer-in-chief of the Royal Corps of Miners, Paris., 1841; the Albany and New Baltimore Ship canal, proposed by William I. McAlpine, A. M. S. of C. E., Albany, 1853, and the estimates made for the Tehuantepec Ship-canal: