Steam and Hot Water fok Greenhouse Heating. 179 



16 degrees, altihough. a distance of some twenty feet, or more is 

 passed over between them. Tlie average loss s'liown in the liser 

 in passing tlie length, of tike two houses is only a trifle over 4 

 degrees, while in the return to the heater it averages some 75 

 degrees. This loss is much greater in proportion to the number 

 of square feet of radiating surface ui the retums than in the 

 risers, yet it can hardly be said that the returns are more efficient 

 in radiating heat. The greater loss in the returns of C and D 

 than in those of A and B is approximately proportional to the 

 number of squaire feet of radiating surface in the returns of C 

 and D, as those of A and B condense intO' a single pipe, into which 

 the thermometer was placed. This may indicate that the heat 

 lost in the returns is radiated from the pipes in proportion to the 

 surface, although it is ihipossible tO' say that this is the fact. 



In the hot-water house, we find that the watOT leaves the heater 

 at an average temperaiture of 155 degrees and comes back at a 

 temperature of 122 degrees by thie upper return and 111 degrees 

 by the lower return. There is an average loss of 13 degrees in 

 passing the length of the house. If we assume that 5 degrees is a 

 fair average for the difference of outside and inside temperatures 

 at the west end and four degrees at the east end, it indicates 

 a loss of 13 degrees from^ heater to the first end of the house — 

 nearly twenty feet— 13 degrees in passing the length of the house, 

 sixty feet, six in the upper and seventeen in the lower return. 



It is seen that in the steaim plant the heat is nearly uniform 

 throughout the whole length of the riser, being carried to the 

 farther extremity of the houses with a loss of 4 tO' 10 degrees, 

 while the hot water riser loses about 25 degrees in passing to the 

 farther end, although on account of its location this point is 

 some twenty feet farther fi'om the heater than the end of the steam 

 house, C and D. In the hot-water plant the variation in temperar 

 ture between the point of leaving and the return to- the heater 

 is much less than with steam, but Table I shows far more irregu- 

 larity in the comparative temperatures at different points, while as 

 a rule more is lost in the riser than in the return. This shows 

 plainly the superioirity of steam for long distance heating and for 

 purposes of bottom heat. The heat can be forced the whole length 



