GREENHOUSE STRUCTURES. 83 



taken out, the walls extended twenty-five or fifty feet 

 further, the flues thrown out, and the heating done by 

 hot water or steam. For, whenever it can be afforded, 

 the heating by hot water or steam will be found to be 

 much the best ; not that there is very much saving in fuel 

 over heating by flues, but it is more durable, more free 

 from danger from fire, or the escaping of gases, so trouble- 

 some with flues; besides it is an immense saving of labor, 

 more particularly if the greenhouses are extensive. Al- 

 though there is less danger from fire when greenhouses 

 are heated by steam or hot- water boilers, yet all care 

 should be used. One of the dangers is in covering 

 the boiler-pit with wooden beams, which, if placed too 

 near the chimney, often ignite. Every season there are 

 many greenhouse fires from this cause. In our own 

 establishment all our pits are covered with railroad iron, 

 over which are built brick arches ; even the ladders lead- 

 ing down to the boilers are of iron. 



CHEAP GREENHOUSES HOW TO HEAT THEM. 



In the American Agriculturist for November, 1874, I 

 described and gave a diagram of a method of heating a 

 greenhouse twenty feet wide by one hundred feet long, 

 by the ordinary smoke-flue and with only one fire. Here- 

 tofore it had been believed that it was impossible to heat 

 a structure of that size with but one furnace, and few 

 ever risked a house more than one-third of the size with 

 a single fire. The principle there described, although 

 not a new one (as I afterwards ascertained, as it had been 

 recorded in the Transactions of the London Horticultural 

 Society some fifty years before), had certainly never been 

 generally practised, and its publication in the American 

 Agriculturist created a great deal of interest, and also 

 involved me in an extensive correspondence. In that 

 article I showed only its application to that particular 



