of the top is hollow, so that the flame of the burner is in the centre of the water, thus economising the heat. The foul air passes away by a pipe through the water, and afterwards can be carried about the house as convenient, but must not be carried horizontally, or there will be a likelihood of a back draught. The pipe produces a considerable amount of heat, and is no more objectionable than a common flue, hence it may be used to heat the back wall, or run under a stage. The heat from the stove itself is the same as any other hot-water apparatus. The lid is perforated, and the moisture thus obtained will counteract the dry heat from the pipe. There is no escape of foul air whatever if properly set. Its simplicity is one great recommendation wherever gas is available, as it is the cleanest and least troublesome of any method of heating 
small greenhouses.
The subjoined sketch may be accepted as a plan which any skilled workman may carry into effect without infringing any one’s patent, or treading on anybody’s toes.
The apparatus consists of an iron or copper boiler ( a ), through which passes a hot-air funnel (g). The boiler is supplied by a small pipe from an open cistern in the house (b), entering the boiler at the bent arrow. The heat is derived from a small furnace formed of a circular hoop of iron with a bottom of wire gauze (f). The furnace is filled with lumps of pumice stone, and is supplied with a gas burner placed below the
