Q. Will you please inform me how I can heat a bathing-pool, 84 feet long, containing about 72,000 gallons of water, the size of pipe that would be necessary, and how long you think it would take to heat? Also the size of boiler necessary.

A. If you wish to warm 72,000 gallons of water, say from 300 to 700 Fah., it will take the heat of about 2,160 pounds of steam to do it.

If you wish to do it in an hour from the time steam is turned on, it will be necessary that the boiler should have a heating-surface of not less than 8co square feet.

If noise is no object when warming the water, a 4-inch steam-pipe leading to a 4-inch header at the bottom of the tank, from which about 30 lengths of 1-inch pipe are run, open at the free ends, but reduced to the size of about a 1/4-inch pipe, may be used to good advantage.

A more expensive apparatus, which may be made noiseless, is a somewhat similar coil of 1 1/4-inch pipe, but closed, the condensed water being pumped back to the boiler instead of being allowed to mix with the water in the pool, as in the first method. The surface for this coil will have to be a matter of experiment.

At the New York Natatorium, Fifth Avenue and Forty-fifth Street, the water is warmed by being circulated directly through the boiler, as in a hot-water apparatus, and is the system we would recommend, a boiler of about 300 feet of surface being sufficient, on the assumption that the time for first heating the water is no object, say three to five hours, after which a slow fire can be made so as to maintain the temperature required.

Of course, where the water from the boiler is discharged into the pool, care must be taken that the hot current cannot scald any one, a crib or some arrangement being required.