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VEGETABLE GARDENING 



161. Heating frames by the use of flues. Many grow- 

 ers heat their frames by a system of flues leading from a 

 furnace burning wood or coal. The plan is regarded as 

 more economical than the hotbed method, and the results, 

 with proper management, are equally satisfactory. The 

 furnace or fire box at one end of the frame is cheaply 

 constructed, and should be 3 or 4 feet long, and about 18 

 inches square, with provision for an ash pit under the 

 grate bars. A main flue is built from the fire box, ex- 

 tending 8 or 10 feet under the soil of the frame, where it 



FIG. 21. STEAM-HEATED FRAME 



separates into two smaller flues that continue almost to 

 the other end of the frame, which may be at least 60 feet 

 long, before they join again and enter a chimney. Figure 

 20 shows this system of heating, but in a different form 

 of construction. The flues may be made of brick, stone 

 or tile, and may vary from 6 to 12 inches in size. Ten- 

 inch tile are very satisfactory. Near the furnace the flue 

 should be about 3 feet under the surface, rising gradually 

 to i foot at the chimney. The air in the flue-heated 



