diameter. These sheaves are connected by transverse three-inch shafts and gearing to the central four and a half inch shaft, which runs the whole length of the through span and connects to the two one hundred horse-power electric motors in the machinery-house. Either motor alone is capable of operating the lift under the most unfavorable conditions. Each sheave supports the two halves of a wire rope about one hundred and sixty-five feet long, the ends being run into sockets. This rope passes around a twelve-inch equalizing-wheel attached to the counterweight suspender, so as to adjust any unequal stretch of the two halves of the rope.

The hydraulic buffers previously described, thirty in number, are used to bring the deck to rest at the lowest position of its travel, and thirty more are employed for the same purpose at its highest position.

In addition to the buffers there will be automatic, electric cut-offs to remove the power before the deck reaches either end of its travel, besides powerful brakes to bring the moving mass to rest quickly whenever the operator may so desire, and always automatically at the highest and lowest points of travel, in order to relieve the buffers.

The main sheaves are five feet in diameter and five inches wide, with eight radial arms. They are each cast in one piece and keyed to a seven-inch steel axle, that rests on two pillow-blocks each eight inches long, fitted with bronze bearings.

The pillow-blocks rest on short posts riveted into long transverse girders that rest on the top chords and cantilever out beyond them about -five feet at each end. These posts are to be well braced longitudinally. The supporting detail between the transverse girders and the top chords is such as to distribute the load properly over the latter.

There will be at each of the four corners of the moving deck two rollers for transverse motion and two for longitudinal motion, all acting on the faces of the columns that uphold the supporting span. The transverse rollers do not act unless there be sufficient wind-pressure on the deck to move  it  laterally;  but  the  longitudinal  rollers  act  whenever  the  deck