HENDERSON'S HANDBOOK OF PLANTS. 



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are limited, or where a temporary green- 

 house is erected. The objection to heat- 

 ing by flues is, that unless carefully con- 

 structed, there is danger from fire, or 

 escape of gas injurious to the plants; 

 still, many large green-house establish- 

 ments are yet heated by flues, in which 

 plants are grown quite as well as by hot- 

 water heating. In constructing the fur- 

 nace for flue heating, the size of the fur- 

 nace doors should be from ten to sixteen 

 inches square, according to the size of 

 space to be heated; the length of the fur- 

 nace bars from eighteen to forty inches; 

 the furnace should be arched over, the 

 top of the inside of the arch from sixteen 

 to twenty-four inches from the bars. 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 given out 

 on all sides. The inside measure of the 

 brick flue should not be less that 8X14 

 inches; if tiles can be conveniently pro- 

 cured, they are best to cover with; but, 

 if not, the top of the flue may be con- 

 tracted to six inches, and covered with 

 bricks. After the flue has been built of 

 brick to twenty-five or thirty feet from 

 the furnace, cement or vitrified drain- 

 pipe, seven, eight, or nine inches in diam- 

 eter, should be used, as they are not only 

 cheaper, but radiate the heat quicker 

 than the bricks; they are also much easi- 

 er constructed and cleaned. Care should 

 be taken that no wood-work is in con- 

 tact with the flue at any place. We i 

 have known cases where wood-work has 

 caught fire after the house had been in 

 operation for years; but an unusually 

 strong draft intensified the heat, and the i 

 charred timber ignited and totally de- I 



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stroyed the green-house and its contents. 

 It should be taken as a safe rule, that 

 wood-work should in no cases be nearer 

 the flue or furnace than eight inches. In 

 constructing do not be influenced by 

 what the mechanics will tell you, as few of 

 them have any experience in such mat- 

 ters, and are not able to judge of the 

 dangers resulting from wood-work being 

 in close contact with the heated bricks. 

 The position in which the flue is placed 

 in the green-house depends upon its 

 size. Presuming that the green-house to 

 be heated is an equal span of twenty 

 feet wide by fifty feet long, the best way 

 is to start the furnace at the north end, 

 so that the flues will run under the cen- 

 ter or middle bench, the top of the fur- 

 nace being inside the green-house, the 

 fire, of course, being applied in the shed 

 outside. A comparatively new plan of 

 constructing flues is to have the flue run 

 to the end of the green-house, and, re- 

 turning, connect with the chimney, which 

 is placed on the top of the arch of the 

 furnace. By this method, 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 ac- 

 tion 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. It 

 will be seen that by this plan we not 

 only get rid of the violent heat given out 

 by the furnace, but at the same time it 

 insures a complete draft, and the heated 

 air from the furnace is so rapidly carried 

 through the entire length of the flue, that 

 it is nearly as hot when it enters the 

 chimney as when it left the furnace. This 

 perfect draft also does away with all 



