Every effort was made to prevent decay. Decrees were issued forbidding emigration or the recruiting of troops for expeditions of discovery, but they were evaded. Thus Louis Columbus, the grandson of the Discoverer and one of the most influential men of the colony, fitted out an expedition against Veragua. African slaves continued to be imported to take the place of the exterminated Indians, but as their importation was expensive the mines were abandoned and the number of sugar estates declined. For the greater part of the period from 1533 to 1556 the government was in the hands of an energetic man, Licentiate Alonso de Fuenmayor, Bishop of Santo Domingo and La Vega, and later first Archbishop of Santo Domingo. He pushed to a conclusion the work on the cathedral and other religious edifices then building, repaired the edifices belonging to the state and constructed the walls and bastions which still surround the city. He was able to ward off the attacks of corsairs, who multiplied in West Indian waters to such an extent that in 1561 the Spanish Government forbade vessels to travel to and from the new world except under convoy. In 1564 the cities of Santiago de los Caballeros and Concepcion de la Vega were completely destroyed by an earthquake and the few remaining inhabitants reestablished the towns at short distances from the original sites. The entire intercourse of the colony with Spain was reduced to two or three caravels a year and the revenues sank so low that the salaries of state officials were paid and continued to be paid for over two hundred years, from the treasury of Mexico.