About seven in the morning we started on horseback, rode up across the sandy district, and entered upon the snow. After we left the pines, small bushes and tufts of coarse Alpine grass succeeded. Where rocks of basaltic lava stood out from the heaps of crumbling ashes, after the grass had ceased, lichens—the occupants of the highest zone—were still to be seen. Before we reached the snow, we were in the midst of utter desolation, where no sign of life was visible. From this point we sent back the horses, and started for the ascent of the cone. On our yesterday’s ride we had cut young pine-trees in the forest, for alpenstocks; and we tied silk handkerchiefs completely over our faces, to keep off the glare of the sun. Our guide did the same; but the Indian, who had been many times before up to the crater to get sulphur, had brought no protection for his face. We marched in a line, the guide first, sounding the depth of the snow with his pole, and keeping as nearly as he could along ridges just covered with snow, where we did not sink far. It was from the lower part of the snow that we began to understand the magnificent proportions of Iztaccihuatl—the “White Woman,” the twin mountain which is connected with Popocatepetl by an immense col, which stretches across below the snow-line. This mountain is not conical like Popocatepetl, but its shoulders are broader, and break into grand peaks, like some of the _Dents_ of Switzerland, and it has no crater.[23] Indeed, the two mountains, joined together like Siamese twins, look as though they had been set up, side by side, to illustrate the two contending theories of the formation of volcanos. Von Buch and Humboldt might have made Iztaccihuatl on the “upheaval theory,” by a force pushing up from below, without breaking through the crust to form a crater; while Poulett Scrope was building Popocatepetl on the “accumulation theory,” by throwing up lava and volcanic ashes out of an open vent, until he had formed a conical heap some five thousand feet high, with a great crater at the top. [23] I was surprised to find Iztaccihuatl classed among the active volcanos in Johnston’s Physical Atlas, and supposed at first that a crater had really been found. But it is likely to be only a mistake, caused by the name of “Volcan” being given to both mountains by the Mexicans, who used the word in a very loose way. As we toiled slowly up the snow, we took off our veils from time to time, to look more clearly about us. The glare of the sun upon the snow was dazzling, and its intense whiteness contrasted wonderfully with the cloudless dark indigo-blue of the sky. Between twelve and one we reached the edge of the crater, 17,884 feet above the sea. The ridge upon which we stood was only a few feet wide, and covered with snow; but it seemed that there was still heat enough to keep the crater itself clear, for none lay on the bottom, or in clefts on the steep sides.