GLASS STRUCTURE 



75 



□f a greenhouse hotbed is necessary, and the sashes should 

 be screwed down and ventilation secured in the same w^ay as 

 there explained. In the center of B, where the two roof sections 

 meet, the sashes rest on a plank 12 inches wide cut out % by 8 

 inches, to form a gutter to carry off water as shown in figure 32. 

 The center planks rest on two rows of 2x3 inch posts, two and a 

 half feet long and twelve inches above the beds; these posts 

 are four feet apart in each row. The total length of the houses 

 here described may vary according to circumstances. The house 

 from which this plan is taken was 100 feet long. It was heated 

 with a second hand tubular steam boiler which at an outside 

 temperature of zero, has 

 to carry about five 

 pounds pressure to main- 

 tain a temperature of 65 

 or 70 degrees. Two inch 

 pipes conduct the heat 

 from the boiler, one line 

 of pipe running up each 

 side of the house and 

 both returning through 

 the center at B, back to 

 the boiler. The furnace 

 room is an excavation 

 10x12 feet and six feet 

 deep at the northerly end of the house, built with a good wall 

 and roof. The length of pipe required is 450 feet. In the ex- 

 treme northern states more pipe radiating surface would per- 

 haps be required for best results. The entire cost of material 

 for a structure of these dimensions, boiler and pipes included, 

 amounts to about $450. The cost of steam fitting will have to be 

 added to this, but the rest of the work can be done by any man 

 of ordinary intelligence. Mr. Greiner, whose description has 

 been largely followed in the above, says that he likes the pipes 

 all above ground as here recommended for forcing vegetables, 

 but if wanted for starting seedlings and for general propagating 

 purposes the pipe had better be placed ten to twelve inches 

 under the surface, and encased in an ordinary three inch drain 



Fig-ure 32. — Valley in market gardeners' 

 greenhouse showing the way the 

 sashbars are attached to the plate. 



