MODES OF HEATING. 71 



the construction of the frame. The roof is formed by the 

 ordinary sashes, six feet in length by three feet in width, 

 which can be bought ready made, or easily be made by a 

 carpenter or any one handy with tools. 



Such a house, if cheapness is an object, should be heated 

 with a flue. It should not be more than 60 and not less 

 than 30 feet in length ; if more, the flue would not heat 

 it enough, and if less it would be likely to get too much 

 heat. About 50 feet by 11 is we think the best size of a 

 green-house to heat with a flue. The flue should run all 

 around the house that is, it should start along under one 

 bench, cross the end, and return under the other bench to 

 the end where it begins, making the length of flue in a 

 green-house of 50 feet about 110 feet long. It should have 

 a "rise " in this length from the furnace to the chimney of 

 at least 18 inches, to secure a free draft. For the first 25 

 feet of flue nearest the furnace it should be of brick, with 

 an air-space inside of about 7 by 7 inches. From this 

 point cement drain-pipe, 7 or 8 inches diameter, may be 

 used. The drain-pipe is now almost exclusively employed 

 here wherever flues are used; it is both cheaper and 

 radiates more rapidly than brick. The cost of such a 

 green-house, complete, in this section, is about $6 per run- 

 ning foot that is, one 50 feet long by 11 feet wide costs 

 about $300 complete. 



CHAPTER XH. 



MODES OF HEATING. 



Although I have alluded to the different modes of heat- 

 ing elsewhere, the matter is one of so much importance, 

 that I will again refer to it more directly. 



Where but one building is erected, with not more than 

 1,000 square feet of glass surface, or where the beginner is 

 limited in means and must practice economy, a smoke-flue 



