Division of Horticulture. 



Samuel T. Maynakd. 



EXPERIMENTS IN GREENHOUSE HEATING. 



In Bulletins No. 4 and 8 were given the results of heating two 

 greenhouses of similar construction, one by steam and the other by 

 hot water. After two seasons of careful test with the same results 

 each time, it was decided that, for houses of small or medium size, 

 hot water gave the best results. For houses of large size, however, 

 no satisfactory conclusions can be drawn until parallel experiments 

 are made with more extensive houses and under similar conditions. 



The two houses used for the above experiments being as nearly 

 alike, in every way, as it is possible to construct them, it was deter- 

 mined to test the value of over-hench piping as compared with under- 

 bench piping. 



OVER-BENCH VS. UNUER-BENCH HEATING. 



For this purpose in the two above mentioned houses were placed 

 two hot water boilers of a standard make, and arranged so as to have 

 the apparatus as complete and equal as possible. 



In the ea.'it house the pipes were arranged under the benches while 

 in the ivest house they were arranged ovrr the benches. 



A partition divides each house into two sections, designated in the 

 tablfs " North Section" and *•' South Section," in the former (North 

 Section) of which vv;is grown coleus, roses and other plants requiring 

 a iiigh lemperature, while ip the latter (South Section) was grown 

 lettuce, caiuations and other plants requiring a lower temperature. 



Upon the '-flow" pipes were placed standard thermometers to 

 register the temperature of the water as it passed from the boiler to 

 the houses. 



Observations were taken four times each day ; at 7 a. m., 1 p. m., 

 6 p. M., and 9 p. m., beginning Dec. 1st and ending April 12th, the 

 results of which are given in the following tables. Table No. 1 gives 

 the results of the average daily observations for the month of Jan- 



