100 THE PRINCIPLES OF FLORICULTURE 



boilers have sufficient capacity to heat additional houses 

 if needed. A six-inch main from the boilers furnishes 

 steam for the three houses which are farthest removed, 

 and a four-inch main furnishes steam for the other house. 

 This main is of sufficient size to heat another similar 

 house. Twenty-four coils of one and one-quarter inch 

 pipe are distributed through each house as follows: 

 seven on the north wall, five on the south wall, and one 

 on each side of the six beds. This piping furnishes suffi- 

 cient heat for the coldest days, and it is seldom necessary 

 to use more than seventeen coils. As these coils ap- 

 proach the farther end of the house, the one and one- 

 quarter inch coils are reduced to three-quarter inch. In 

 these are placed the valves which control the heat (Fig. 

 16). This economizes the expense, for the cost of one 

 and one-quarter inch valves is much higher than the 

 cost of the three-quarter inch valves. 



This reduction in size also equalizes the heat better. 

 It retards the passage of steam through the pipes so that 

 the steam is practically all condensed as it reaches the 

 end of the coils. At the northeast corner of the house 

 the pipes enter a Squires one and one-half inch trap and 

 as this trap operates, it lifts the water to the top of the 

 return pipe, which extends to an elevation of nine feet. 

 From here it returns by gravity, first through a two-inch 

 pipe to the head house, and then in a four-inch pipe to 

 the boiler. The owner states that this system has given 

 perfect satisfaction. 



79. Location of other pipes. Upon the arrangement 

 of the heating pipes in greenhouses depends very largely 

 the owner's success or failure in growing his crop. One 

 must know the native environment of the species with 

 which he is working, and then endeavor to imitate as- 



