The centre of this trade is Salta, or, rather, the little village of Rosario de Lerma, nine miles south of it, where most of the caravans are formed. The saltpetre works make yearly contracts in advance with the Rosario dealers, fixing the number and price of the beasts to be delivered at Calama. The cost of transport includes, besides the pay of the cattle-drivers--eighty to a hundred piastres a journey--the shoeing of the mules, the rent of pasture at San Pedro, and the value of the beasts which die on the way. In 1913 the number of animals exported by this route was put at 30,000. The saltpetre works buy also draught-mules for their waggons. Draught-mules must be heavy, and only animals over five feet in height are sent to Chile. Bolivia is now the only market for the smaller mules and for asses. The trade in mules in its traditional form and the industry of breaking-in still flourish at Santa Maria. The mule-dealer's business is very different from that of the cattle-dealer. The mules are so tough that it is possible to send them by roads which would be unsuitable for cattle.[28] The journeys are longer, and the contracts are less settled in advance. Moreover, breaking-in is a delicate operation that requires experience. The survival of the mule-trade at Santa Maria is an example of the maintenance of an industry owing to the presence of skilled handicraft. The men who break in the mules at Santa Maria have a remarkable caste-pride. Their first job is to go to Santiago or Cordoba to buy the mules. They bring them back to Santa Maria by way of Catamarca or the valley of Tafi. At Santa Maria the mules are broken in, then taken to the lucerne-farms at Poma to be put into good condition. There they remain in pasture for several months; and at length, when the season is suitable, the little band of Santa Marienos gathers together and, driving the now docile beasts in front of them, and putting no loads on them in order that they may keep fresh, make for the fair at Huari in Bolivia, or even as far as Sucre. There they sell at a hundred and fifty piastres each the animals which they had bought for half that price before being broken in. The number of mules hibernating at Poma is about 4,000. [28] For instance, herds of mules are taken from Abrapampa, on the line of the Quiaca, to the saltpetre mines of Antofagasta, whereas every effort to convey cattle by this route has failed.