This is a pulley recently introduced by Messrs. J. and E. Hall, of Dartford Eng. With the exception of the boss, which is cast, it is composed entirely of steel or sheet iron. In place of the usual arms a continuous web of corrugated sheet metal connects the boss to the rim; this web is attached to the boss by means of Spence's metal. Inside the rim, which is flanged inward, a double hoop iron ring is fixed for strengthening purposes. The advantageous disposition of metal obtained by means of the corrugated web enables the pulley to be made of a given strength with less weight of material, and from this cause and also on account of being accurately balanced these pulleys are well adapted for high speeds.