Page:Popular Science Monthly Volume 71.djvu/185

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WHILE the inhabitants of the United States were suffering from the heat of an unusual summer, the member-s of the International Geological Congress were making a study of the geology of the plateau region of Mexico and were enjoying the delightful climate of that country. Few regions of the world are more fascinating; the combination of vast volcanic peaks, broad arid plains, with their curious desert flora and a brilliant tropical sky, leaves an impression never to be forgotten.

It was in the midst of such interesting surroundings that during August, September and October, 1906, the International Congress of Geologists met, and, as a member, the writer had an opportunity to visit several of the Mexican volcanoes under especially favorable circumstances. In the first place, the guides to the various volcanoes were trained geologists of the Mexican Geological Survey, who had previously made a study of the regions to which they conducted the party. Moreover, the personnel of the visitors embraced geologists from Europe and America, who had investigated volcanoes in many parts of the world, and consequently, by way of comparison, were able to add a great deal of interesting information.

If you will look at a map of Mexico, you will notice that the names Volcano Colima, Nevado de Toluca and Valle de Santiago form the vertices of an obtuse triangle west of the City of Mexico. With these three points we will concern ourselves.


Volcano Colima

Volcano Colima, the most recently active volcano in Mexico, whose cloud-crowned summit can be seen for many miles along the Pacific coast, is situated almost due west of Mexico city and about fifty miles from the Pacific Ocean. It can be reached without much difficulty from the village of Zapotlan by a horseback journey of ten hours. On the ride one winds along the sharp divides which separate deep ravines, around the high Nevado, and finally reaches the foot of the cone from which the climb on foot must begin.

A more beautifully symmetrical volcanic cone than that of Colima, as viewed from the north, can hardly be imagined; the only feature breaking the symmetry being a secondary cone which arises from the northeast slope. The beauty of the cone is enhanced by the great clouds