Is a Ship Canal Practicable? / Notes, Historical and Statistical, Upon the Projected Routes for an Interoceanic Ship Canal Between the Atlantic and Pacific Oceans, in Which is Included a Short Account of the Character and Influence of the Canal of Suez, and the Probable Effects Upon the Commerce of the World of the Two Canals, Regarded Either as Rivals, or as Parts of One System of Interoceanic Navigation

by S. T. Abert

2. Chiriqui—No information extant.

3. Panama route, and improvement of the harbors.

4. San Blas and Chepo—A better line may be practicable.

5. Caledonia Bay, or the Gulf of Urabà to the Gulf of San Miguel, by way of the Savana or Lara Rivers.

6. Examination of the depression noticed by Gen. Michler.

7. The line proposed by Sr. Gorgoza.

The elevation of the passes upon these routes should be definitely fixed. The instrument which must determine the question of practicability is the Wye spirit-level. If the capacity of the harbors are insufficient for the largest class of ships, or can not be made available at a reasonable cost, further examination is unnecessary.

BAROMETER.

Notwithstanding the improved formulæ, and more careful method of observation recommended by Lieut.-Col. Williamson, Corps Engineers, the barometer is subject to peculiar and anomalous variations, along the slopes of the Cordillera of the Isthmus and the Andes. Lieuts. Gibbon and Herndon refer to this phenomenon. Lieut. Maury attributed the effect to the damming or piling up of the trade-winds against the mountains. A recent traveler in the valley of the Amazon, I. Orton, observed the same phenomenon, but objects to Maury’s theory.

Sr. Moro makes the following observations: “If, under these circumstances (prevalent winds), barometrical observations are made simultaneously on both sides of the Sierra, on the side of the Gulf, they will exhibit a lower elevation than the true one, the error being greater as that station may happen to be lower down or more towards the north; but if time should admit of waiting until the weather be equally fine on both sides (which seldom happens), then the difference between the levels of the barometrical columns is insensible.”