Gas-heating.—The heating of houses by means of gas is a modification of the hot-water system above described, and should, as far as possible, be conducted on precisely the same principles, the fuel being gas instead of wood, coal, coke, or charcoal. There are several kinds of gas apparatus in use, and there is now no difficulty in heating a plant house in an efficient manner, provided only that the proprietor is prepared to employ experienced engineers and pay the extra cost of fuel, for gas is the most expensive of materials employed for the purpose of heating, though it is the cheapest for the purpose of lighting.
The principal advantage of gas-heating is that stoking is dispensed with, and, if the pressure in the pipes is pretty constant, the apparatus may be left for many hours without attention, as the heat given off will be constant, and to a great extent determinable beforehand. It must not be concealed, however, that to manage a gas-heating apparatus requires some amount of experience, and those who would succeed must habituate themselves to observation, not only of the action of the apparatus, but of its influence on the temperature of the house at different hours and in different states of the weather. A body of flame sufficing only to keep out frost on a frosty night with a clear sky might suffice to raise the temperature of the house to 70° or 80° on a mild night with a cloudy sky, and, as a matter of course, alternations so great and sudden would seriously injure the plants the apparatus was intended to preserve. Granting, then, that the adoption of a system of gas-heating will not absolve the amateur from responsibility to attend to its management, the nest question is, what form of apparatus is the most to be desired?
The simplest form of gas-heating apparatus consists of a ring of jets burning blue, through wire-gauze, under a small vessel tilled with water, over which is placed a vertical pipe, the mouth of which expands like a hood over the whole affair, to catch and carry into the air without all the products of combustion. This has the advantage of extreme simplicity, and the disadvantage that it is slightly injurious to nearly all kinds of plants, but especially so to camellias, oranges, and other winter-flowering subjects. But for preserving bedding plants and ferns, and other quick-growing subjects, it answers very well; for, being in use only when severe frost compels the temporary employment of heat, the injury done is trifling, and
