Mr. Pritchett reports that in the district around Cocheros, Casapi, and Carpis, the rocks are of crystalline formation, in many localities highly disintegrated, and composed of masses of hornblende, felspar, and mica. He remarks that felspar contains much potash, of which the chinchona-trees are said to require a large quantity for their full development; and, as felspar abounds in this region, he attributes the abundance and size of the chinchona-trees to this circumstance. He also reports that steatite, a silicate of magnesia and alumina, abounds in the vicinity of Huanuco. He describes the climate as moist and warm, and says that the difference in the degree of moisture and warmth between the lower slopes where the _C. micrantha_ flourishes, and the higher parts of the mountains inhabited by the _C. nitida_, is very striking, while on the lower slopes the soil is much deeper and richer.[372] He reports the elevation of Cocheros above the level of the sea to be about 4000 feet,[373] but he made no meteorological or other observations; and I think there can be no doubt that the elevation of that mountain is much greater than Mr. Pritchett supposes. I do not find any information on this point in Poeppig's travels; but the Huanuco region is quite a beaten track, and there are several accounts of it by modern travellers. Huanuco itself is 6300 feet above the sea;[374] the distance thence to the summit of the cuesta del Carpis, which is 8000 feet above the sea, is about twenty miles, and there is a descent on the other side into the valley of the Casapi of 2920 feet.[375] According to this account the village of Chinchao, in the Casapi valley, would have an elevation of about 5000 feet. From Chinchao to the foot of the Cocheros mountain is a distance of twenty-five miles down the Casapi valley,[376] a gentle descent, with numerous cottages and plantations on both sides of the road.[377] Thus the foot of the Cocheros mountain would be about 4500 feet above the sea, and its summit at least 6000 feet. We shall not, therefore, be very far from the truth if we place the region of _C. nitida_ on the Cocheros and Carpis mountains at from 6000 to 7000 feet above the sea, and of _C. micrantha_ at from 4000 to 5000 feet. Mr. Pritchett performed the portion of this important undertaking which I intrusted to him with promptitude and zeal. Time was a great object, and, by going direct from Lima to the best locality in the Huanuco chinchona region, he completed the necessary collection of plants and seeds, and returned to the coast in little more than three months.[378] This shows how essential a previous knowledge of the chinchona region, of the people, and of the language, was, without which the collector would probably lose much time, which is the same thing as spending much money, and eventually wander into a locality where only worthless species are found, as was the case with the Dutch agent.