Serfs, under the feudal system a class of labourers whose position differed only from that of slaves in being attached to the soil and so protected from being sold from hand to hand like a chattel, although they could be transferred along with the land; liberty could be won by purchase, military service, or by residing a year and a day in a borough; these and economic changes brought about their gradual emancipation in the 15th and 16th centuries; mining serfs, however, existed in Scotland as recently as the 18th century, and in Russia their emancipation only took place in 1861.