GREENHOUSE STRUCTURES. 87 



given out on all sides. The inside measure of the brick 

 flue should not be less than eight by fourteen inches. If 

 tiles can be conveniently procured, they are best to cover 

 with ; but, if not, the top of the flue may be contracted 

 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 

 pipes, eight or nine inches in diameter, should be used, as 

 they are not only cheaper, but radiate the heat quicker 

 than the bricks ; they are also much easier constructed 

 and cleaned. Care should be taken that no woodwork is 

 in contact with the flue at any place. It should be taken 

 as a safe rule, that woodwork should in no case 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 matters, and 

 are not able to judge of the dangers resulting from wood- 

 work being in close contact with the heated bricks. 



On one occasion I had in use two houses heated with 

 flues each about 100 feet in length. The chimneys had 

 been made of wood, and they had been safely used for 

 three winters, but on the occasion of a severe storm in 

 winter, when our fires were going at full blast, both of 

 them took fire within an hour of each other, though fully 

 100 feet from the furnace. Fortunately the chimneys 

 had been attached to the outside of the house, and were 

 knocked off without material injury being done. On 

 another occasion, a house containing upwards of 10,000 

 plants took fire by a workman placing kindling wood on 

 the flue near the furnace. The result was great injury 

 to the greenhouse, and total destruction of its contents. 

 I mention these cases, to show the necessity of the utmost 

 caution. Every winter there are are hundreds of fires 

 originating in greenhouses by the woodwork taking fire 

 either from smoke flues, or when the heating is done by 



