Q. Is there not some arrangement by which two boilers can be heated from one water-back?

A. Figure 127 (page 184) illustrates a new method of warming two boilers from a single water-back, each boiler being under a different pressure.

The arrangement has been devised to overcome the objection to and necessity for two water-backs in the same range, where water from a tank or cistern at the top of a house must be warmed to supply the upper stories, while water for kitchen and laundry purposes and the lower stories is obtained directly from the street supply in the usual manner.

The contrivance consists essentially of the high-pressure or "tank" boiler A, the low-pressure or "Croton" boiler B, and, in the absence of any other name, what may be called the "heater" C; with, of course, a water-back of ample dimensions in the range.

There are three distinct circulations: (1) The warm water flowing from the back (which in this case is the low-pressure) passes through the pipe c to the heater C, returning through the pipe c'; (2) The warm water in the outside chamber (g) of the heater C, passing through the pipe d into the boiler B, and returning to the heater through the pipe d'; (3) The water from the inner chamber or tubes (/) of the heater C passing through the pipe e into the boiler A, and returning to the inner chamber again through the pipe e'.

It will be seen by this that the first and second circulations are low-pressure, and that the third is high or tank-pressure; but not so of necessity, as the tank-pressure may be used in the water-back, heater, and boiler B, transposing the order of the boilers; but the arrangement shown is, in the opinion of the inventor, the best, as by this order the tank may become empty, by neglect or otherwise, without danger to either boilers, or the tank-water may be shut off without drawing the fire.

The heater is seven inches in diameter by fourteen inches long, outside measurement, and is made of copper. The inner part (f) is a tubular heater, with connecting chambers at the ends. The water of the outer chamber is around and between the tubes, and imparts its heat to the water within the tubes. The tubes are three-quarters of an inch in diameter by ten inches long, and thirteen in number, and have been found by experiment to give equal temperatures to both boilers.

Figure 127.

How much less surface in the inner part of the heater would give good results the inventor does not know, but he points out the fact that an excess of surface can have no other effect than to maintain an equable temperature between the boilers. He also points out that should the fire go down, leaving both boilers full of pretty hot water, and should the warm water in any one boiler be drawn away, exchanges of heat by circulation still go on between the boilers and the heater, warming the cold boiler, and, of course, cooling the warm one, but, nevertheless, giving a greater quantity of warm water from the boiler drawn on than could be gotten if it connected directly with its own water-back.

This was devised by Mr. John Tucker, of New York.