with the results given in the sequel. From the Malatengo near the Cituñe River, the ground rises constantly toward the north, and after we crossed the Almoloya it descends steadily toward Chivela.
This hacienda is situated on the south-west course of the remarkably level table-land of the summit of the sunk Cordilleras, which join the Andes by the east and the Rocky Mountains by the west.
The Tarifa and Chivela plains are one and the same table-land of the summit, but the valley seems divided into two parts, the hills approaching each other a little to the south-west of Tarifa.
The remarkable Chivela plains can be said to be the flat, broad valley of the Otate Brook, and having an area of ten and one half square miles.
The soil is sandy to the depth of about twenty feet, as is shown by the wells of the locality, and the easily excavated and deep banks of the many brooks that traverse its surface in the rainy season.
North of the Chivela House, the eastern slope of all the gently rolling hillocks are covered with stones of different sizes, hinting by their direction and position that they have been deposited there contemporaneously with the drift of the Pacific plains, or by the action of floods of a more recent pericd.
There are eight dry-brook crossings before entering the contracted part of these plains, and they show that the sand deposit becomes thinner as we approach Tarifa, where many pools of stagnant water prove that the soil is impermeable.
The houses at Tarifa are on a slight elevation, and all the surrounding country becomes flooded during the heaviest rains; but soon after, the waters find their way to the Atlantic by the Almoloya and Chichihua rivers. These plains are covered with grass, and in the places not cleared, a thick underbrush shelters abundant game and a few beasts of prey.
Royal palms, the silk-tree, and three species of sensitive plant are very numerous.
We remained in Tarifa a week, waiting by appointment for Don Julian Macheo, the owner of extensive lands of the isthmus. We made many explorations with a levelling transit and two barometers, measuring distances with the micrometer on the speaking-rod.
Simultaneous barometric observations were taken hourly on the coast, at Chivela, and at whatever point explorations were under way.
We found the details of the country very imperfectly given in maps, and became convinced that we should be obliged to do the topographic work over again, especially in the neighborhood north of Tarifa. Señor Macheo informed me that the lake supposed to exist by some, near the headwaters of the Chicapa, was simply an invention; because his father visited the source of the Chicapa, and never found the lake. Later in our explorations, I saw the principal source of the Chicapa as it poured from among the crevices of the large rocks in the neighborhood of Mr Scarce's rancho.
The Tarifa River has its source in the Pasapartida Hills.
On December 18th, its breadth was 20 feet, its mean depth.08 foot, and its mean velocity.03 foot per second; consequently its delivery was at the time less than one half cubit foot per second.
From Tarifa to Chichihua River. — On December 19th we left early in
