X. L., from San Francisco, says:

" My swimming tank will be 80 feet long by 30 feet wide, and of an average depth of 5 feet. It will have an 8 inch inlet and the same size outlet. The temperature of the water will be about 74° Fahr., as it runs into the tank, and I would like to raise it to 84 degrees. I want also to supply hot water to 20 bathtubs. Now, how can I get the desired temperature with this large volume of water running through the tank? By answering the above information through the columns of your journal you will greatly oblige a subscriber."

[A tank of the size given will hold approximately 744,000 pounds of water when full, and if you desire to increase its temperature from 74 to 84 degrees in one hour of time, you will require a boiler that is capable of evaporating 744,000 pounds of water in an hour, or thereabouts, say, in round numbers, 250 horse-power. This, remember, is for one hour; in other words, if you want to warm that tank full of water 10 degrees in one hour, you will require boilers equal to 250 horse-power.

On the other hand, if you are satisfied to start your boiler, say the evening before, and spend 10 hours of the night in warming the water, instead of one hour, then a boiler of about one tenth the capacity, or a little over, will do, say a 30 horse-power boiler, the extra five horse-power being sufficient to cover the loss of heat from the tank during the 10 hours you are warming it up.

You have omitted a very important item in asking this question, by not mentioning the quantity of water that runs through the tank every hour. You say, " How can I get at the desired temperature with this large volume of water running through the tank? " You omit to say how great this volume is, and also the time taken for it to run through the tank. If you mean to run the full contents of the tank through every hour, then it will require boilers of 250 horsepower, as before stated. If you intend to run it through in 10 hours it will take a 30 horse-power boiler, as before. If, however, you are satisfied with running only 1,000 gallons of fresh water in every hour, a boiler of about three horse-power will be ample, and for every additional 1,000 gallons you will want another three horse - power added to the boiler. With this you will be able to find the boiler power.

Fifteen pounds of steam per hour (one-half horsepower) condensed to water, will warm a bathtub full of water once. If your 20 tubs are used continuously, once in an hour for 10 hours a day (or for any time) you will require five horse-power additional for baths. To apply the heat of the boiler, to the swimming bath you may simply circulate direct from a hot-water boiler, or use steam in a coil in the bottom of the swimming bath.]