little stones or pebbles anciently used in making computations, taking suffrages, playing at draughts, and the like. In after times, pieces of ivory, of silver, gold, and other materials, were used in lieu of the calculi, but still retained the ancient name. Computists, when they were slaves or newly freed men, were called calculones; those of a better condition were named calculatores or numerarii. There was ordinarily one of these in each family of distinction. The Roman judges anciently gave their opinions by calculi, which were white for absolution, and black for condemnation. Hence calculus altus denoted a favourable vote, either in the case of a person to be acquitted of a charge, or elected to some dignity or post; and calculus niger had a contrary signification. This usage is said to have been borrowed from the Thracians, who marked their happy or prosperous days by white, and their unhappy by black pebbles, which were put each night into an urn.

Besides the diversity of colour, there were some calculi also which had figures or characters engraven on them; as those used in taking the suffrages in the senate and in assemblies of the people. Their form is still seen in some medals of the Cassian family; and the manner of casting them into the urns is represented on the medals of the Licinian family. The letters marked upon these calculi were U. R. for uti rogas, and A. for antiquo; the first of which expressed an approbation of the law, the latter a rejection of it. Afterwards the judges who sat in capital causes used calculi marked with the letter A. for abolo; C. for condemn; and N. L. for non liquet, signifying that more full information was required.

Urinary. See Chemistry, and Surgery.