After a year and a half spent in South America, Humboldt sailed for Cuba, where he remained for several months, collecting material for his "Political Essay on the Island of Cuba." From there he went to Quito, in Ecuador, crossing one of the most difficult passes in the Andes, "the path so narrow that it rarely exceeds twelve or sixteen inches in width, and for the most part resembles an open gallery cut in the rock," and the Paramos of Pasto, "desert regions where, at a height of about twelve thousand feet above the sea, all vegetation ceases, and the cold is so intense as to penetrate to the very bones." In June, 1802, they reached Quito, where, five years previously, an earthquake had destroyed forty thousand people. This month they made the ascent of Chimborazo, at that time regarded as the highest mountain in the world. "At certain places," he says, "where it was very steep, we were obliged to use both hands and feet, and the edges of the rock were so sharp that we were painfully cut, especially on our hands." As they climbed on, "one after another, we all began to feel indisposed, and experienced a feeling of nausea accompanied by giddiness, which was far more distressing than the difficulty of breathing.... Blood exuded from the lips and gums, and the eyes became bloodshot.... A few rock-lichens were to be observed above the line of perpetual snow, at a height of sixteen thousand nine hundred and twenty feet; the last green moss we noticed was growing about twenty-six hundred feet lower. A butterfly was captured by M. Bonpland, at a height of fifteen thousand feet, and a fly was observed sixteen hundred feet higher.... When we were at a height of about seventeen thousand four hundred feet we encountered a violent hailstorm." The height of the mountain is over twenty-one thousand feet. The intrepid Humboldt four times crossed the Andes; he travelled over Peru; he called attention to the fertilizing properties of guano, and then he sailed for Mexico, where he remained for a year. Here he met a lady greatly esteemed in that country, called the "fair Rodriguez," the most beautiful woman he had seen in his journeys, but whom he admired more "for her graces of mind than her beauty of person." He regarded her as an American Madame de Staël. It is asserted that the grave man of science was deeply interested, but it was too late--she was already the wife of another, and had two children. Humboldt, like most other great men, all his life enjoyed the society of intellectual women, who were a constant inspiration. After two months passed at Havana, Humboldt came to the United States, spending three weeks with President Jefferson, at his home at Monticello. He never failed to speak in grateful terms of the courtesy he received from Americans. He studied carefully our institutions, and greatly admired the republic; slavery alone saddened him.