From the first the indenture system was in vogue. Circumstances made this necessary, for had no obligations been put upon the immigrants to work for a certain number of years in servitude, they would have secured tracts of ground for themselves and set themselves up as independent planters, as soon as they arrived in the country. It was found to be impossible to establish a class of free laborers. Also the system had its advantages for the immigrant. The voyage to the colony, so long and so expensive, was the chief drawback to immigration. Thousands of poor Englishmen, who could hardly earn enough money at home to keep life in their bodies, would eagerly have gone to the New World, had they been able to pay for their passage. Under the indenture system this difficulty was removed, for anyone could secure free transportation provided he were willing to sacrifice, for a few years, his personal freedom. And, despite the English love of liberty, great numbers availed themselves of this opportunity. There came to Virginia, during the period from 1635 to 1680, annually from 1000 to 1600 servants. The immigration in the earlier years seems to have been nearly if not fully as great as later in the century. During the year ending March 1636 sixteen hundred people came over, most of whom were undoubtedly servants.[161] In 1670 Governor Berkeley estimated the annual immigration of servants at 1500.[162] But we need no better evidence that the stream at no time slackened during this period than the fact that the demand for them remained constant. So long as the planter could obtain no other labor for his tobacco fields, the great need of the colony was for more servants, and able-bodied laborers always brought a handsome price in the Virginia market. Col. William Byrd I testified that servants were the most profitable import to the colony.[163] The fact that the term of service was in most cases comparatively short made it necessary for the planter to repeople his estate at frequent intervals. The period of indenture was from four to seven years, except in the case of criminals who sometimes served for life, and without this constant immigration the plantations would have been deserted. Thus in 1671, when the population of the colony was 40,000, the number of servants was but 6,000.[164] Nor was there any sign of slackening in the stream until the last years of the century, when there came a great increase in the importation of negro slaves. As soon as it became practicable to secure enough Africans to do the work of the servants, the need for the latter became less pressing. For many reasons the slave was more desirable. He could withstand better the heat of the summer sun in the fields, he was more tractable, he served for life and could not desert his master after a few years of service as could the servant. We find, then, that after 1680, the importation of servants decreased more and more, until, in