Hot-Water as a source of heat for gardening purposes is preferable to any other. It is less expensive, more manageable, and less troublesome than any other. See Tank System and Stove. The following are some of the best modes of its application to various structures.

Pine-Pit

The best that has been constructed is thus described by Mr. G. Fleming:

In "a pine-pit recently erected at Trcntham, the tank system of bottom-heating and that of hot water pipes for top-heat are combined; and for keeping a sufficient and steady heat with a small consumption of fuel, nothing can be more satisfactory. The pit is seventy-seven feet long, and twelve feet wide inside, and is heated by what is called a saddle boiler. Under the bed are four tanks, into which the water is delivered from the boiler by a four inch pipe, and after pursuing its course, is again received by another pipe. The advantage of two deliveries is, that the water not having so far to go does not get so cold before it is returned to the boiler, and the heat is more regular in all parts of the house. The depth of water in the tanks is about three inches. The tanks are made of brickwork coated with Roman cement. They are arched over with brickwork also, which we find cheaper than covering them with slates, and by leaving interstices between the bricks of which the arch is composed the steam is allowed to escape, and penetrating the stratum of rubble above, to keep the tan in a proper state of moisture. The same boiler also supplies a range of four inch pipe, which goes round the pit. There are cavities in the wall to permit the steam from below to pass to the top of the pit.

The aperture to these can be closed at pleasure, thus insuring a perfect command over the moisture of the atmosphere. There is a chamber which formerly contained a flue belonging to the house that occupied the place of the one I am now describing. This chamber has been left with the view of its being useful for filling with hot dung either for the purpose of assisting to maintain the heat of the house, or for destroying insects. The tanks and pipes cannot both be worked at the same time, but they are fitted with stop-cocks, so that either can be worked at pleasure, and a few hours in the middle of the day, when the pipes are not wanted, is found amply sufficient to keep up the bottom-heat, as the mass of material when once heated retains its heat for a considerable time." - Gard. Chron.

Melon And Cucumber Pit

For this, Mr. Glendinning, the scientific nurseryman, of Turnham Green, has given the following plans and description.

Fig. 87.

Explanation Of The Plan

a, Bur-bidge and Healy's boiler; b b, iron troughs; c c, pipes; d d, iron troughs as at b b in plan; e e, pipes as at c c in plan; //, copper tubes fastened to the troughs to admit steam when required; g, wire trellis; hhh, convenient places for the growth of sea kale, rhubarb or asparagus, or keeping tubers of any kind during the winter.

Fig. 88.

"This pit is intended for melons in summer, and to preserve pelargoniums or other plants in winter. As the object in constructing it is more for the purpose of experiment than the permanent culture of melons, I have designed it so that pines may be substituted without any alteration whatever; indeed any kind of plant which such a structure is capable of receiving, and at the same time requiring protection, and in a warm temperature, may be very advantageously introduced, the hot-water apparatus being so contrived as to command both bottom and surface-heat either separately or conjointly. For the purpose of supplying soft water for the plants, I have placed a slate cistern at one end of the pit, in order to collect the rain water from the roof. The soil, if permitted to come in contact with the iron troughs, would, of necessity, become dried and totally unfit for the roots of any plant: with a view to obviate this, I have placed rough flint or other stones over the bottom of the bed and round the troughs to prevent immediate contact, and at the same time to admit of a more uniform diffusion of heat over the bottom of the pit, so that the soil which rests upon it may be more regularly heated.

The other advantage and conveniences of this pit will be apparent from the above plan and section without further remark." - Gard. Chron.