The increase of population, the extension of the occupied pasture-ground, and the greater demand from Europe for hides and wool, tended to multiply the volume and value of Argentine exportable commodities. Northern Europe made marvellous strides in purchasing power during the eighteenth century, and prices all over the world felt the impetus. The commercial policy of the Spanish government became more lax and the trade prohibition fell into contempt and disuse. The system of fleets of Spanish ships under convoy was abandoned, and single ships, mostly foreign owned, and trusting to their sailing qualities and equipment to escape capture, carried all the trade. The trade of Buenos Aires grew and the population of the city increased in proportion. The exhaustion of the surface deposits and richer lodes of precious metals in the mining provinces during the eighteenth century tended to increase the relative importance of Buenos Aires and her territory, even in the mind of the Spanish government, and to turn a current of immigration toward the pastoral and agricultural provinces. In 1750 the Spanish government made an effort to get rid of the Portuguese in Colonia by negotiation. Portugal agreed to exchange that port for the Jesuit Missions which covered the fine pastures in the western half of the present Brazilian state of Rio Grande. The helpless Indians were driven off or massacred in spite of their feeble resistance, but as soon as the treaty was made public, Spanish and Jesuit protests against the abandonment of the territory were so violent that the agreement was formally annulled by mutual consent. The Portuguese retained Colonia, and though they gave up their formal claims to the Missions the military operations they had so promptly undertaken against that region had pretty well rooted out Spanish influence on the east bank of the Upper Uruguay. It was never re-established, and the dividing line of 1750 is still substantially the boundary between Spanish and Portuguese South America.