Irrigation entails the services of quite a staff of arbitrators and administrators. The head men, who have jurisdiction of a higher order and secure the accurate distribution of the water amongst a number of channels or communities, are now, as a rule, officials of the administration, appointed by the provincial authorities (_juez de Irrigacion_ at Catamarca, _juez de rio_ at Rosario de Lerma). But the _juez de agua_ of each community or each channel is a syndic elected by the interested parties. At Santa Maria the _juez de agua_ is elected by the owners and confirmed by the Government. He controls irrigation throughout the department, settling all differences, submitting plans of work to a meeting of the owners, and assigning their respective charges in labour and contributions according to their rights. * * * * * This land of customs and traditions is also a land of lively movement. The briskness of the traffic is primarily due to continuous exchange between the various zones of the mountainous district. This large trade, so scattered that the railways could not dream of satisfying its needs, is carried, in the old fashion, on the backs of mules. The lively aspect of the roads between the tableland and the lower valleys of the region, the brisk interchange of goods between zones with different climates, is one of the common features of life on the Andes. But the classic spectacle presents a different aspect in different latitudes. In Peru, and in southern Bolivia, the higher valleys--Jauja, Cuzco, the Pampas of Cochabamba and Sucre--have centres of dense population and agricultural wealth at a height of between 9,000 and 11,000 feet. They raise cereals, and receive from the tropical districts (_montanas and yungas_) sugar, cane-brandy, cocoa, and coca-leaf. The valleys of the Argentine Andes are usually at a less elevation than the _yungas_ and _montanas_ of Bolivia and Peru. But they are not hot districts, and have not tropical vegetation. Frost prevents the harvesting of sugar-cane at Salta, at a height of 4,000 feet. As to the coca-leaf, which is not as much used here as in the north, the Argentine _valles_ do not send it to the tableland, but receive it indirectly from there, through the southern _yungas_. In default of tropical crops, the Argentine _valles_ sow wheat and maize, which they sell to the Indians of the cold districts of the Puna for wool and salt.