ENGINEERING REPORTS. 81 
Mountain Passes. 
There are, properly speaking, no less than six mountain passes 
on the Isthmus of Tehuantepec, whose summits divide the 
waters of the Atlantic from those of the Pacific ocean. Com- 
mencing at La Chivela, the one farthest to the west, they occur 
in the following order : 
Elevation above Pacific. Authorities. 
La Chivela 780 feet Barnard. 
Masahua 843 " 
West Piedra Parada 800 " Estimated. 
East Piedra Parada 825 " « 
Tarifa (Portillo) 684 " Moro. 
Convento 750 " Estimated. 
It is possible that another passage may be found through 
the mountains, near the head-waters of the Eio Almoloya, fol- 
lowing down the south side of Cerro Huacamaya to the foot of 
Chivela Pass. 
From the summit of Masahua, at grade, there is a total fall to 
the plains at the foot of the mountains of 553 feet ; consequent- 
ly, as the summit of the Pass is 793 feet at grade above the 
Pacific, the plains are at this point on grade 240 feet above : 
to reach which we ran down on a distance of ten miles, and on 
an average of 55 feet to the mile. 
The Pass of Chivela presents less space for the development 
of the line than the Pass of Masahua, but it has the advantage 
of a summit 63 feet lower. 
Coming up from towards Juchitan, or when on the elevated 
part of the plains immediately south of Portillo de la Martar, 
an apparently low depression in the mountains is seen just 
east of Cerro Prieto, through a gap in the Masahua range. 
This gap (a little north of Paneho de la Cueva), on closer ex- 
amination does not present the favorable appearance seen 
from the plains, and I think is quite impracticable for a rail- 
road. If, however, the appearance from the plains were as 
favorable in reality, and a good line could be laid through the 
gap, it would then be of very little, if any importance; for, 
after gaining the north side of the mountain through this gap, 
6 
