Benches and beds.
In the narrow houses it has been customary to have raised benches three or four feet in width along the walls, with one or more others six or eight feet in width in the middle of the houses, the walks being eighteen to twenty-four inches in width between the benches, or the walks placed along the walls, and all of the benches have a width of seven or eight feet. In some cases, the gutters are supported by means of arches so as to permit the placing of walks under the gutters, where the space is less useful than in the center of the houses. The raised benches are often built entirely of wood, or with wooden bottoms and some in five feet in the width of the house. This some times hastens development 10 to 25 per cent.
Heating by means of flues.
Various methods are used for heating vegetable houses and all have their merits under certain con ditions. The old-fashioned flue answers very well for small houses in sections where wood can be ob tained cheaply for fuel, but it is not very reliable in the colder climates, except after severe cold weather is over. A brick furnace is constructed at one end of the house, with a length of three to five feet according to the length of the wood. An opening can be left at one end near the bottom to less destructible materials such as gas-pipe or cement for the supports. In some cases, cement has been used with good satisfaction for construct ing the bottoms of raised benches. The practice is becoming more common in the construction of houses designed entirely for vegetable forcing, to do away with raised benches. Sometimes the ground is handled exactly as in a garden, all of the ground being covered with the crop with the ex ception of a narrow space every fifteen or twenty feet for use when watering or ventilating. It is more common, however, to keep the surface soil a foot or more above the level of the walks. This certainly helps in the drainage of the soil. If the soil is inclined to be heavy, it is an excellent plan to sink the walks or to fill up the beds so as to make the surface at least eighteen inches above the walks. The soil can be held in place by cement walls that need not be more than two inches thick at the top. If drain tiles are run about a foot be low the surface, either across or lengthwise of the beds, it will aid both in the drainage and the aera tion of the soil. Even better results can be secured
by running one of the heating pipes in a tile once serve for a draft, and a tile or iron smoke-pipe should lead from near the top of the other end, with a slight ascent, to a smoke-stack at the far ther end of the house. There should be a door for putting in the fuel in the end or top of the furnace. In addition to the increased danger from fire when a flue is used, these furnaces give more or lees trouble with smoke and do not work well when the flue is more than fifty feet long. For use in fire hot beds, which are really low and narrow greenhouses used for starting lettuce and similar crops in the spring, a flue with a tile running through the soil at the depth of a foot answers very well.
Heating with hot water.
For greenhouses with less than 5,000 square feet of glass, a hot water heating system will be more satisfactory than either a flue or steam system, as, although it will cost nearly 50 per cent more to install, it will be more economical in fuel and will require less attention than a steam-heating plant, besides giving a more regular heat if run without a regular night fireman.
In a hot-water system the water is heated in a boiler and then carried through the houses in a series of pipes. The circulation is due to the fact that cold water is heavier than hot water, and as one end of the circuit of pipes is attached to the bottom, while the other is connected with the top of the boiler, the heavy cold water in the greenhouse flows back in the pipes and pushes the light hot water out at the top to flow off into the system to take its place. A great variety of hot-water boilers, of both cast- and wrought iron, are made for greenhouse heating. The cast iron boilers are to be preferred for small plants, but there are a number of tubular boilers .that are made for hot-water heating that answer very well. An ordinary tubular steam boiler will also be found very satisfactory for hot-water heating, although if a tubular boiler is to be constructed for the purpose it would be better to have tubes also in the top of the boiler.