pulley on the fan to do the work. These are the most popular sizes of exhaust wheels. The next application on the list, open tank elevator pumps, commands the highest price for current per H. P. in the motor of any elevator application. The methods of operating the open tank hydraulic elevators in question are undoubtedly familiar to you all. Instead of the usual steam pump, a power pump of some approved design is substituted, and connected to the motor by suitable countershafting to give the required revolutions at the pump. The regulation of the motor in this case should be controlled by the position of water in the lower tank, as in the case of the steam pump. And in this connection let me suggest the necessity of great care, both in installation and insulation. On all installations in basements and cellars or elsewhere where there is the slightest tendency to dampness, raise the motor off the floor on a suitable frame or stand and build around it on all sides of possible approach a low platform, using glass insulators as legs or standards to support it. So arrange this that the motor or its connections cannot be reached except when standing on this insulated platform, and the liability to a shock will be reduced to the difference of potential between the terminals of the machine. To return to the subject. Let us take for an illustration an elevator using 120 gallons of water per trip and consuming one minute in making its entire up trip or about two per round trip. The lower tank or water supply is on a level with the pump. The upper tank is 70 ft. above the pump, and in the piping to the upper tank are five elbows. For each elbow add 2 ft. to the elevation, or an approximate total elevation of 80 ft. × 120 gallons gives us 9,600 foot gallons. This amount would be required every two minutes if the elevator was in absolutely constant operation, or 4,800 foot gallons per minute × 8½ gives us 40,800 foot pounds. This we must at least double to allow for friction in pump shafting, etc., making 81,600 foot pounds, or about 2½ H. P., say 3 required in the motor. This class of elevator is confined almost entirely to passenger use. Therefore the service required of the motor is much more constant and the margin between the H. P. hours contracted for and the H. P. hours of actual service much smaller than in any other elevator use, excepting possibly the services in connection with pressure tank elevators in the more popular office buildings. In this case we have a maximum average use of 80, and instances such as the hotels, small office buildings, etc., where the service will not exceed 60 of the contract H. P. hours. In order, however, that the electric light company shall derive the greatest benefit from this inconstant service, the installation and wiring should be the best, and only the most approved and economical apparatus employed.