One of the most important causes for the passing of Indian slavery is found in the introduction of indentured white servants. Almost from the time of the earliest settlements these servants were an institution in the English colonies. Some of them were persons who entered voluntarily into temporary bond service to pay for passage to the new world.[1174] Some were prisoners of war.[1175] Others were convicts sent into exile for punishment.[1176] These white servants were so much desired by the colonists that requests were not infrequently sent to England for them.[1177] To encourage their voluntary coming, the colonial authorities sometimes offered them special inducements.[1178] The number of such servants in the different colonies varied according to conditions in America and England. Naturally their number was greatest where their work was most needed.[1179] Whatever their condition before coming to America and whatever the reason for their coming,[1180] their productivity of labor, native intelligence and acquaintance with the customs and observances of civilization made them more desirable than Indian servants. There were forces, also, urging them to go to America, and forces in America drawing them there. So, until the development of the traffic in negroes, and their consequent greater use, the indentured white servants were for a while perhaps the leading factor in the decline of Indian slavery. Another element that contributed greatly to the decline of Indian slavery was that furnished by negro slaves. The rapidly increasing number of negroes in each individual colony attested both the energy of trading companies and the desire of the colonies for the negro type of slave labor. Both indentured white servants and negro slaves, in fact, far outnumbered the Indian slaves. The sources from which the white servants and the negro slaves were drawn were well nigh inexhaustible, whereas the sources of Indian slavery were limited. From these limited sources, also, the colonists drew but in a small degree. White servants and negro slaves were obtained by peaceful means, but the acquisition of Indian slaves not infrequently meant danger to the colony. Behind the indentured white servants and the negroes there were powerful forces supplying them to the colonists in some cases even faster than they needed them. Both indentured white servants and negroes proved more easily fitted to the life and work required of them by their masters, their labor was more productive and they were more easily controlled.