It contains numerous illustrations; maps of the routes of the ancient aqueducts and the city of Rome in the time of Frontinus; a photographic reproduction of the only MS. (the Monte Cassino); several explanatory chapters, and a concise bibliography, in which special reference is made to P. d Tissot, E tude sur la condition des agrimensores (1879).

If we mark off a segment AB along the line of action so as to represent the force completely, the A moment is represented as to magni FIG 15 tude by twice the area of the triangle OAB, and the usual convention as, .o sign is that the area is to be reckoned positive or negative iccording as the letters 0, A, B, occur in counter-clockwise or clockwise order.

Le Cadet, E tude du champ electrique de l'atmosphere (Paris, 1898); (2) Svante A.