86 PRACTICAL tfLORICTTLTURE. 



on the top of the furnace, not in the furnace, as some 

 have supposed. As soon as a fire is lighted in the 

 furnace, the brick-work forming the arch gets heated, 

 and at once starts an upward draft, which puts the 

 smoke-flue into immediate action and maintains it ; 

 hence there is never any trouble about the draft, as in 

 ordinary flues having the chimney at the most distant 

 point from the furnace. By this plan we not only get rid 

 of the violent heat given out by the furnace, but at the 

 same time it ensures a complete draft, the heated air from 

 the furnace being rapidly carried through the entire 

 length of the flue, so that it is nearly as hot \vhen it enters 

 the chimney as when it leaves the furnace. This perfect 

 draft, also does away with all danger of the escape of gas 

 from the flues into the greenhouse, which often happens 

 when the draft is not active. Although no system of 

 heating by smoke-flues is so satisfactory as by hot water, 

 yet there are hundreds who have neither the means nor 

 the inclination to go to the greater expense of hot water 

 heating, and to such, this revived method is one that will, 

 to a great extent, simplify and cheapen the erection of 

 greenhouses. Many old-established florists, who have 

 had the old plan of flues in use, have changed them to 

 the one here described, and with great satisfaction. The 

 wonder is that such an important fact has been so long 

 overlooked, for at the time it was discovered, heating 

 greenhouses by flues was almost the only method in use, 

 In constructing the furnace for flue heating, the size 

 of the furnace doors should be, for a greenhouse twenty 

 by fifty, about fourteen inches square, and the length of 

 the furnace bars thirty inches ; the furnace should be 

 arched over, and the top of the inside of the arch should 

 be about twenty inches from the bar. The flue will 

 always draw better if slightly on the ascent throughout 

 its entire length. It should be elevated in all cases from 

 the ground, on flags or bricks, so that its heat may be 



