130 
HEATING HOT-HOUSES BY HOT-WATER. 
The most important of the properties of the hot-water method, 
consists in the power it has of keeping up the temperature of the 
house for a long period without attention from the attendant: and it 
is entirely owing to the excess of fluid that it has this advantage over 
steam heat. 
The ordinary method of making reservoirs and boilers so large as 
to answer the purpose of maintaining the heat during the night, has 
the objection of rendering it a considerable time before the appara¬ 
tus can be raised to a temperature capable of giving much heat; and 
it appears that it would be a material improvement to heat the water 
for a reserve of heat, by passing the pipes of the apparatus through- 
the water so that its temperature should be slowly raised, and the 
house receive heat during the time. 
A small proportion of surface of pipe will heat the water, because, 
water abstracts heat from a heating surface with about twenty times 
the rapidity that air does at the same temperatures; hence, by put¬ 
ting a twentieth part, in addition to the surface required for the 
house, through a proper reservoir of water, it will be slowly raised to 
nearly the same temperature as the water in the pipes, and return 
its heat to the house as soon as the fire ceases to keep up an excess 
of heat in the pipes. Fig. 20, shows such an arrangement where c 
is the cistern, with part of the pipe passing through it. 
20 
There is very little strain on the borders of hot-water apparatus, 
except in cases where there is much difference of level; and, as 
these rarely occur, consequently they may be constructed in the 
best mode for applying heat, which is most effectively done by hav¬ 
ing as much bottom surface as possible, with a boiler of a given ca¬ 
pacity. For burning a bushel of coals per hour, the area of the fire 
grate should not be less than eight, nor greater than sixteen square 
feet, and the bottom surface four times the area of the grate, with 
