Leaving the inter-Andean region for the Montaña, it is interesting to observe the contrast in scenery and natural conditions. In the Andean valleys, the traveller who departs from the line of the railway must journey in a coach or on muleback; in the Montaña, the small steamer or the canoe is the accustomed means of travel through the forest, the waterways of this region affording transportation throughout their entire length. Among the most important rivers having their source in the Montaña—generally in a ledge branching off from the foothills of the Andes, are the Yavary, Yuruá, Purús, and some tributaries of the Madeira River. The great waterways, with their affluents, form a network of communication in the Amazon country, and contribute greatly to the development of the rich resources of this vast zone, which is essentially tropical, yielding the valuable products of the rubber tree, the dyewoods, medicinal herbs and hardwoods of commerce, and other precious gifts of nature. With such a great variety of physical conditions as those which govern Peru, it is not surprising that its climate should present many contrasts, and some unique features. In the coast region, owing to the proximity of the snow-clad Andes and the cold Humboldt current, the average temperature is lower than that of any other country extending over the same degrees of latitude; in winter, the thermometer registers an average temperature of fifteen degrees centigrade, and in summer the average is twenty-six degrees centigrade, the hottest days marking no higher than thirty degrees in the shade. The mildness of the climate makes this region of Peru an agreeable place of residence even to those accustomed to the bracing air of the temperate zone; it is not so liable to the epidemics of a tropical climate as are less favored countries in the same latitude; and, with proper sanitation and the adoption of modern hygienic measures, there is no reason why the Peruvian coast should not be a paradise of health and longevity. The climate of the sierra varies with the location and altitude of the inter-Andean valleys and the plateaus that separate them. In the lower slopes of the Cordilleras, the heat is greater than on the tablelands, which have a temperate climate; while on the lofty, snow-clad summits of the range, the cold is as intense as in the arctic regions. The seasons of the sierra are divided differently from those of the coast; the rainy season, from November to May, being called winter, and the dry season, though colder, being known as summer. The average temperature, within the populated region of the sierra, is ten degrees centigrade during the day and five degrees at night, the absence of the sun making a great difference in the atmosphere. The pure air of the plateaus is very beneficial to consumptives, and Jauja, Tarma, Huancayo, and other towns of the sierra have become famous as health resorts.