Dry Stove

Formerly this was heated by flues only, a stage for plants occupying the place of the bark-pit in the moist stove. But modern science has suggested the far better mode of heating by either steam or hot water. Of these two the latter is by far the most preferable. The following is the plan adopted at Elcot, and has never been much improved: -

"Brick flues are subject, from their numerous joints and the mortar cracking, to give out at times a sulphureous gas, which is injurious to plants; and even with two fireplaces in a house forty or fifty feet long, it is impossible to keep up an equal temperature in the whole length. The houses get overheated in the neighbourhood of tho fireplace; and it is difficult to maintain a proper warmth at the extremities of the flues.

"Steam may do very well on a large scale, and where there is constant attention to the fire, both day and night; but the objections are, the great expense of a steam-boiler and the apparatus belonging to it, the frequent repairs that are required, and the necessary attention to the fire, which is as great upon a small scale as upon a large one. Besides this, there is a greater risk of explosion in a hot-house steam-boiler than in that of a steam-engine; for steam-engines generally have persons properly instructed to manage them; but gardeners, or their assistants, cannot be so competent.

Fig. 162.

"The heating with hot water has none of the objections I have mentioned as belonging to flues and steam. The apparatus is simple, and not liable to get out of order. The boiler has only a loose wooden cover, and no safety-valves are required. The fuel consumed is very moderate, and when once the water is heated, very little attention is wanted; for it retains its heat for many hours after the fire has gone out.

"The house is forty feet long and ten feet wide inside, heated by a boiler, a, placed in a recess in the centre of the back wall; the fireplace under the wall is got at from a back shed, b. The boiler is two feet six inches long, one foot six inches wide, and one foot eight inches deep. From the end of the boiler proceed horizontally four cast-iron pipes of three inches and a half diameter; two of them are joined to the boiler just above the bottom, and the other two directly above these, and just below the surface of the water. The house is divided by glazed partitions into three compartments, d, e,f, for the convenience of forcing one part without the other.

"The middle compartment is two lights in width, and the other two have four lights each.

"The pipes from the boiler go horizontally to the front of the house, where one upper and one lower pipe branch to the east compartment, and other two pipes to the west, and are carried to the ends of the house along the sides of the flues, where they unite to cast-iron reservoirs at each end of the house, g g, which reservoirs are each three feet six inches long, one foot six inches wide, and one foot eight inches deep, having iron covers. These reservoirs are filled with water that communicates, by means of the pipes, with the water in the boiler.

"When the boiler, pipes, and reservoirs are filled, and a fire lighted under the boiler, the heated water, ascending to the top of the boiler, forces its way along the upper pipes to the reservoir, the cold water finding its way back to the bottom of the boiler through the under pipes; and the circulation continues regular as long as there is any heat under the boiler, the hot water flowing through the upper pipes to the reservoir, and, as it cools, returning back to the boiler through the under pipes.

"I have repeatedly, after the water has been heated, immersed a thermometer in the reservoirs at the ends of the house, and have only found a difference of three or four degrees between that and the water in the boiler. It is not necessary to make the water boil; and, if the fire is judiciously managed, no steam will be raised and no water wasted. It is, however, necessary to examine the boiler occasionally, and to add water when any has evaporated.

"Valves might be fixed in the boiler, pipes, and reservoirs, for letting steam into the house if required; but that would induce the necessity of boiling the writer; and it has not been done here, as I find I can produce all the steam I require, with little trouble, by wetting the pipes with a watering-pot.

Fig. 163.

"I am persuaded that the advantages of this mode of heating, with its great simplicity, will give satisfaction to every practical gardener who has an opportunity of trying it. When once the water is heated and the fires well made, he may retire to rest, certain that the pipes will not get cold during the night, but retain a considerable heat in the morning." - Trans. Hort. Soc.