CHAPTER V.

Admiral Davis’s Report—Table of the Tunnels of the different Isthmean Routes—Altitude of Ridge at Darien—Comparative Cost of Canals with and without Tunnels—Lift Locks and Thorough Cut—Tide in the Atlantic and Pacific—Moderate Lockage can not Obstruct the Navigation—Gisborne on Thorough Cut—His Error as to Velocity of Water—Objections to Strait—Tabular Statement of the Cost of Tunnels, English, French, German, and American—Tunnel of Mont Cenis—Hoosac Tunnel—Profiles of Mont Cenis and Hoosac Tunnels—Dimensions of Ship Tunnel—Cost of Open Canal—General Michler’s Report—Guard Locks Necessary—Cost of System of Lift Locks—Conclusions Supported by Garella and Michel Chevalier.

In compliance with a resolution of the Senate, dated March 19, 1866, we have an admirable report from Admiral Davis. In this report the relative merit of different lines is exhibited; carefully prepared tables, showing the amount of freight which would pass the Isthmus; a list of ninety publications and fourteen maps, are appended. Ten of these maps, based on recent surveys, supply much valuable information.

“It is to the Isthmus of Darien,” says Admiral Davis, “that we must look for a solution of the question of an interoceanic ship canal.” And he quotes from Airian, “who has made a careful study of this subject,” the assertion that, “with regard to the Cordillera, in proportion as it advances, proceeding from the base of the Isthmus, it descends a good deal, and is only, so to speak, a range of hills or isolated peaks, the bases of which are intersected by ravines, which point out to engineers the true route of the canal. The Indians in the neighborhood of Caledonia Bay make use of these passages. One of them is elevated fifty metres (164 feet), and is covered with a luxuriant growth of mahogany, palm, ebony, and other trees.” “This description,” Admiral Davis remarks, “is not based on actual measurement, but from probabilities deduced from M. Garella’s survey of another part of the Isthmus, and from data, equally conjectural, drawn from the published statements of Messrs. Cullen and Gisborne.”

A thorough exploration may justify this conjecture, but no data exists for fixing the absolute altitude at 164 feet. The value of the statements of Messrs. Cullen and Gisborne may be contested.

It will be seen from the altitude given in the table below, that however correct in point of fact these opinions may be, they are not sustained by the figures taken from the maps accompanying the Admiral’s report:

Table showing the length of Railroads and Canals, length of Tunnels, altitudes of Summits, estimated cost of some of the lines proposed for uniting the two Oceans, from actual surveys:

ROUTES.LENGTH.LENGTH
TO BE
CONSTRUCTED.		LENGTH
OF
TUNNELS.		ALTITUDES
OF
SUMMIT.		ESTIMATED
COST.		CANAL
OR
RAILROAD.		AUTHORITIES
AND
REMARKS.
MILESMILESMILESFEET
Tehuantepec190 855$ 16,900,000Canal.M. Moro.
“ 8437,847,896Railroad.J. J. Williams.
Honduras234234 2956 Canal.Trautwine.
Nicaragua to Realijo298160 17420,000,000“Napoleon III.
““ Brito194 60032,000,000“O. W. Childs.
Panama  53⅔ 3.745927,000,000“M. N. Garella.
  “ 48 48 28050,000,000“Col. G. W. Hughes.
San Blas 30 71500 “McDougal.
Darien to San Miguel 42 7 to 898065,000,000“Gisborne.
““ 1020 “Prevost & Strain.
“  Lara to Sucubti 610? “Bourdial.
Atrato to Humboldt Bay126 3½ 145,000,000“Kennish.
“““ 149⅔ 52⅔2½970134,450,154“Lt. Michler, U.S.A.
“  to Cupica 325,000,000“Trautwine.

From the above table it would appear that the altitude of the dividing ridge falls off toward the two extremities of the Isthmus, viz.: near the Tehuantepec and the Atrato routes, but the greatest depressions have been found between Aspinwall and Panama, and on the line by the way of Lake Nicaragua and Lake Managua.