Negro," a slave could buy his freedom, in the event that his master was willing to sell, by paying the price sought. Slaves were allowed to earn money during their spare time by working as shoemakers, cleaning clothes, or selling the produce they grew on their own plots of land. Slaves were able to pay for their freedom by installments. They pay in installments for the freedom of their newborn child, not yet baptized, at a cost of half the going price for a baptized child. Many of these freedmen started settlements in the areas which became known as Cangrejos (Santurce), Carolina, Canóvanas, Loíza, and Luquillo. Some became slave owners themselves. The native-born Puerto Ricans (criollos) who wanted to serve in the regular Spanish army petitioned the Spanish Crown for that right. In 1741, the Spanish government established the Regimiento Fijo de Puerto Rico. Many of the former slaves, now freedmen, joined either the Fijo or the local civil militia. Puerto Ricans of African ancestry played an instrumental role in the defeat of Sir Ralph Abercromby in the British invasion of Puerto Rico in 1797. Despite these paths to freedom, from 1790 onwards, the number of slaves more than doubled in Puerto Rico as a result of the dramatic expansion of the sugar industry in the island. Every aspect of sugar cultivation, harvesting and processing was arduous and harsh. Many slaves died on the sugar plantations. 19th century Royal Decree of Graces of 1815 The Royal Decree of Graces of 1815 was intended to encourage Spaniards and later other Europeans to settle and populate the colonies of Cuba and Puerto Rico. The decree encouraged the use of slave labor to revive agriculture and attract new settlers. The new agricultural class immigrating from other countries of Europe used slave labor in large numbers, and harsh treatment was frequent. The slaves resisted -from the early 1820s until 1868, a series of slave uprisings occurred on the island; the last was known as the Grito de Lares. In July 1821, for instance, the slave Marcos Xiorro planned and conspired to lead a slave revolt against the sugar plantation owners and the Spanish Colonial government. Although the conspiracy was suppressed, Xiorro achieved legendary status among the slaves, and is part of Puerto Rico's heroic folklore. The 1834 Royal Census of Puerto Rico established that 11% of the population were slaves, 35% were colored freemen