70 GARDENING FOR PROFIT. 



At present prices, in this locality, these pits cost about 

 $7 per lineal foot, everything complete, put up in the way 

 indicated by the plan in a plain substantial manner. But 

 those whose circumstances do not admit of the expense 

 of heating by hot water (which is nearly half the cost of 

 the whole), may put up structures of exactly the same 

 character, and heat them by the common smoke flue at 

 an expense of from $4 to $5 per lineal foot, in the man- 

 ner shown by the plan, figure 8. It will be seen by this 

 sketch that two flues only are used for the three pits, 

 each passing first up under the bench on the outside 

 houses, is carried along the end and returned through 

 the middle houses ; this equalizes the temperature in all 

 three, for the outside houses get only one run of the flue, 

 but it being directly from the fire gives about the same 

 heat to the outside houses as two runs in the middle 

 house, which, being a greater distance from the fire, are 

 much colder. Three attached houses, heated thus, 

 should not be over fifty feet long in this latitude. South- 

 ward they may be sixty feet and northward forty feet. 

 Peculiarities of locality have much to do with the heat- 

 ing ; in positions particularly sheltered from the north- 

 west, the same amount of flue will heat sixty feet quite 

 as easily as in exposed places it will heat forty. The 

 proper way of constructing the furnace and flue is of im- 

 portance enough to require a description, which is given 

 at length on page 87. As far as possible, let the instruc- 

 tions there given be followed to the letter, as they are such 

 as long and very extensive experience in the use of flues 

 for greenhouse heating has shown to be -such as rarely fail 

 to give the very best results. Twenty-five years ago 

 nearly all the greenhouses used for commercial purposes 

 were heated by flues. In my own practice I used no 

 other mode of heating until 1860, and grew plants quite 

 as well there as we do to-day. One of the largest rose- 

 growing firms in this country still uses flues only, with 



