There are so few gaps in the lower slopes of the Cordillera that the available water is gathered at a small number of points. The Rio San Juan alone drains a belt of the Cordillera at least 140 miles broad. Each of the two oases, Mendoza and San Rafael, has two streams of water to feed it. The Mendoza and the Tunuyan at Mendoza, and the Diamante and the Atuel at San Rafael, approach each other, when they leave the mountains, so closely that the estates they water blend into a continuous area. Then, however, instead of uniting, they diverge and are lost, separately, in the plain. These streams have less fall than the thinner torrents of the oases of the north-west, and the average inclination of the dejection-cones which bear the vineyards is slight. The upper slopes of the cone, where thin beds of clay lie upon shingle, give clear wines of excellent aroma. Hence, in the Mendoza district, the vineyards of Lujan and, further down, of Godoy Cruz, Guaymallen, and Maipu produce choice brands. On the plain, to the east of Mendoza, at San Martin and Junin, the harvest is larger, but the wine is rough, and one can often taste the saltpetre of the clayey soil. There is the same difference between the upper and lower district at San Juan and San Rafael. The oases of San Juan and San Rafael spread evenly over the most suitable parts of the alluvial talus, but the oasis of Mendoza has a peculiar shape which can only be explained by historical causes. The cultivated belt is a narrow strip along the Tunuyan, for more than sixty miles, as far as the heart of the plain, out of sight of the Cordillera. It is one instance, out of a thousand, of the influence of traffic on colonization. As a matter of fact, the road from Mendoza to the coast, by which the cattle convoys of San Luis went to the _invernadas_, passes along the Tunuyan. The estates grew up by the side of it. The villages of Santa Rosa, Las Catitas, and La Paz, which mark the various stages of it, are all of ancient origin. Strangers are rarely found there. One still sees in them very old houses, built before the railway was made, dating from the days of the _carril_ or waggon-road. The importance of this line of water across the desert is clearly seen on the Woodbine Parish map.