Oldest method of heating hothouses

2105. The oldest mode of heating hothouses is by fires and smoke-flues; and on a small scale, it is still used occasionally. Heat is the same material, however produced, and a given quantity of fuel will produce no more heat when burning under a boiler than when burning in a common furnace. Hence, with good air-tight flues formed of well burnt bricks and tiles accurately cemented with lime-putty, and arranged so as the smoke and hot air may circulate freely, every thing in culture, as far as respects heat, may be perfectly accomplished.