A gentleman from Brooklyn writes to confirm our views in reference to the preceding question, particularly the answer to the second difficulty, which he also experienced and which our hint set him to investigate intelligently:

" The inclosed diagram, which I believe is a correct copy of the plumbing of a great part of the small brick residences which are being built in this city (Brooklyn), represents the principal features of the hot and cold water - supply of my house.

"You will notice that for cold water to enter the boiler it must flow past the cold-water faucet at the sink. If, now, some one opens the hot water faucet at the bathtub or one of the washbowls upstairs, and some one else goes to draw cold water at the sink, say to rinse his hands under the faucet, he is likely to take them away with a start, and for a moment think he is scalded, and that he has opened the wrong faucet, but upon further trials he will find it is the faucet intended to be the cold one, and upon trying it again he is treated to a similar experience.

Figure 56.

This I could not always repeat before I saw your answer, and when I brought persons to try my geyser I was generally disappointed, but now when I want to show any one how to draw hot water from the cold faucet I send one of my children to open a hot-water faucet upstairs.

"The reason of it is plain to me now. The 1/2-inch pipe from the street is not large enough to send water to the upper floor when cold water is being drawn down-stairs at water-closet or wash-tubs, and the accumulated head of water in the hot pipe running upstairs flows backward (the pressure being reduced) into the boiler and over through the cold pipe and faucet until the water finds its equilibrium somewhere between the top of the boiler and the second floor.

"This can be repeated continuously, and one hand may be placed where the word cold is and the faucet manipulated with the other, when hot and cold water will be found to pass back and forth with each increase and decrease of pressure."