On the 19th they proceeded to the hacienda, where they were soon joined by Señor Olivares, who was prevented by some business from accompanying them any farther. He furnished them a guide who conducted them through a thick forest, to the highest limit of the pines, which they found to be 12,544 feet above the ocean. Here they passed the night. At midnight it rained, which was soon afterwards followed by a severe hoar frost. On the 20th of April, contemplating to reach the summit this day, they distributed the instruments among the carriers, and mounted on the mules, began the ascent at half after three in the morning by the light of the moon. After travelling a short distance they left all vegetation, and entered a district of loose stones and sand, which although hardened considerably by the rain, greatly fatigued the mules. In this manner they ascended on the south-west side of the mountain, until half past six when they could proceed no further with the mules, as much because they were too fatigued, as on account of the steepness of the volcano's side. They therefore dismounted, and abandoning the mules, gave the barometer in charge to Quintana. They resumed their ascent through a soil composed of loose sand and stones, with many fragments of pumice stone, being desirous of reaching some rocks which appeared to be connected with the summit. Here, however, the difficulties commenced; the acclivity was very steep, the footing so loose that every step they made forward they slipped back nearly the same distance; and the thinness of the air fatigued them so much that they could not advance more than fifteen or twenty steps without resting. In this manner they proceeded about half a mile, until they reached the rocks, where they waited for the Indians who followed more slowly. During this time the thermometer stood at 28° of Fahrenheit. The sky was perfectly clear, but a dense stratum of vapor rested on the horizon, which prevented them from perceiving any object, and made it appear as if they were in the midst of an ocean. At 8 o'clock A. M. they first saw the sun. As soon as the Indians arrived, they took a light breakfast, and continued ascending among large loose stones, which have rolled from the summit, and, arrested by each other in their course, have formed a kind of zone, so lightly supported however, that the slightest touch sets them in motion. This naturally alarmed the Indians, who declined going any farther; but by persuasions and promises they succeeded in getting them to advance. Seeing, however, that the road was becoming rather worse, all further means of persuasion to induce them to proceed began to fail. They endeavored to ascend through a gulley which they had perceived on their left; but the way thither was very difficult, and was rendered more perilous by clouds which prevented their distinguishing any thing. Here the Indians entirely refused to stir any further, and having given