104 
APPLICATION OF HOT WATER IN HEATING HOT-HOUSES. 
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 attendants ; 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 apparatus 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 temperature : hence, by putting 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. Figure 7 shows such an arrangement, where C is the cistern, with 
part of the pipe passing through it. 
Fig. 7- 
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, con- 
sequently they may be constructed in the best mode for applying heat, which is 
most effectively done by having as much bottom surface as possible, with a boiler 
of given capacity. 
For burning a bushel of coal 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 thirty-two feet of side flue ; and a considerable 
advantage results from adopting the larger proportion for the grate and bottom 
surface, on account of the fire requiring less attention. 
The forms of boilers may be varied in a considerable degree, provided the 
above quantity of surface receive the effect of the fire ; the first kind used by 
Mr. Atkinson was a parallelopiped, with the fire applied to the base only. I 
have employed the same form, but of greater length in respect to its width, hence 
