Since leaving Cochabamba we had made very good time; although there had been several halts en route, the distance covered each day was comparatively great, ranging sometimes up to forty miles, considering that we always travelled with our pack-train. Such long rides were made possible by the fact that all _arrieros_ were mounted; if they travelled on foot, as in Colombia, the distance traversed each day would be about half. Fast travelling, however, was hard on the mules. When we reached Samaipata our animals were in poor condition, so we left them in charge of an attendant and engaged a complete new outfit for a short side-trip toward Santa Cruz. One of our main objects in undertaking this entire long, arduous journey was to attempt to determine the southern limit of the subtropical forest zone. This type of forest grows on the eastern slopes only of the Bolivian Andes; a section directly eastward would, therefore, take us through this zone and possibly enable us to find the solution to the problem. It was not intended to cover the entire one hundred and ten miles from Samaipata to Santa Cruz, but only to go far enough to secure the desired information. The mountain range breaks down rapidly east of Samaipata, but the road to Santa Cruz is, nevertheless, neither an easy nor a level one. There are still four steep ridges to cross, called Cuevas, Negra, Herradura, and Guitara; between them lie small, well-watered valleys, planted in cane and fruits, and settled by Bolivians of Spanish extraction. There are no more Quechuas, nor is their language spoken; after many months we were once again in a Spanish-speaking world. The trail, at least during the second day’s travel, lies near the course of the Rio Piray, and the scenery flanking this watercourse is among the most picturesque found in the Bolivian Andes. There is a bewildering succession of dome-shaped peaks, unscalable cliffs and overhanging precipices, all of red sandstone. Many of the formations are spotlessly clean and smooth, as if scoured, or cut with a knife. The river laves the base of the rugged chain, and dark caverns worn into the frowning battlement open alluringly to tempt the adventurous spirit to explore their unknown depths. Vermejo is the name given to a fertile region that may be called _yungas_, between the Negra and Herradura ridges. Several houses are scattered along the trail; the inhabitants grow maize, potatoes, and large quantities of cane that is used in making _chancaca_ (brown sugar) and molasses. The people also make bread and a peculiar “food-drink” called _somo_ to sell to passers-by. _Somo_ is made of boiled maize that has been left standing until fermentation sets in, and is taken with molasses. To us, the taste was very disagreeable, but the natives were fond of it and purchased a bowlful at frequent intervals. _Chicha_, made from peanuts, was also to be had at some of the dwellings.