on the Pacific side in a radial direction; but the dispersion of the drift takes place in a south-westerly direction, whatever the shape or inclination of the ground on these plains. Erratic blocks are found in this direction from the Ostuta, which flows south-westerly to the Tehuantepec River. This latter stream runs from west to east, and even in the mountains, as on the Atravesado, there are blocks of granite at an elevation of five thousand feet above the ocean, and arranged in lines, sensibly parallel to those of the coarse drift on the plains thirty miles off. Some of the blocks have a volume of over 120,000 cubic feet. These blocks are also found arranged in the same direction north of the dividing ridge of the isthmus, in the town of Santa Maria.
Most of the Pacific rivers have considerable beds; but with the exception of the Ostuta, they all pass very little water at this season.
The Niltepec was nearly dry, and the brooks Chocolate, Huacamaya, Agua, Zarea, Petaca, Roble, and Juamol were entirely dry. The plains are arid, hot, and sandy. Besides a parched underbrush, hardly any other vegetation is seen, except a poor quality of grass and the jícara-tree (Crescentia cujete). This tree is variously called in different places jícara, totuma, higuera, dita, and chima; it is small, not unlike the apple-tree in appearance, and bearing a green sesile fruit or gourd, used by the natives extensively as cups, vessels, etc. When ripe it possesses in a most extraordinary degree the properties of ergotine; but fortunately the Indians are not aware of it, and use it for no medicinal purposes. The Ostuta River was gauged at Piedra Grande, and found to deliver only 203 cubic feet per second.
On the 9th of January we left Piedra Grande by the north-east, and camped by the Ostuta, nine and a quarter miles north of our starting-point.
In all, we made four camps, and ascended the river for seventeen miles from Piedra Grande, or where the highest peak of the sierra bore south 89° west from us. Two and a third miles after leaving Piedra Grande, we turn north to ascend the Cristalinas Hills, in order to see the valley of the Ostuta, and Moro's Gap on the Atravesado. We soon reached the top of a steep hill, at the point marked on the map No. 2, El Portillo.
This point is 122 feet below Chi vela; and looking to our left, we had a discouraging bird's-eye view of the Ostuta. Its tortuous course could easily be traced in the deep valley at our feet, until it turned sharply to the west, behind a mountain lower than the one we stood upon. Moro's Gap was square in front of this turn, and considerably higher than El Portillo.
We descended then to the river, and after fording it without difficulty, ascended up stream by the right bank, cutting our way through the dense foliage. Occasionally we ascended near hills, or climbed trees to study the topography. Our barometric observations were taken very carefully, though in our two first tents the atmospheric state was unpropitious.
Impracticability of Joining the Chicapa and Ostuta Rivers. — Señor Moro makes Último rancho and Chivela at the same height. A glance at the barometric data shows it to be 275 feet above Chivela; but although the heights for each set of observations agree within six feet, since only three observations were taken, I will pass to the rancho Scarce, where five sets of good observations were taken, giving a mean of 624 feet. The distance between these two points is less than eight miles; following the river
