27 



in the greenhouse or in public buildings. Most ventilators are 

 located at the ridge, and cold draughts often descend and check 

 the growth of plants. Allowing the fresh air from the outside to 

 enter around the steam pipes would seem to be theoretically cor- 

 rect, but we have had no experience with this method. 



The management of a large house is always easier owing to the 

 less sudden changes in temperature, moisture, etc.; and as for 

 mildews and other troubles, they are always m.ore common in 

 small than large houses. 



Table X showing light records taken at different distances 

 from the glass. 



No. of Experiment. 



Readings. 



1 Light records at 5 feet from glass 



"20 " " ' " 



2 Light records at 6 feet from glass 



"IS " " " 



3 Light records at 6 feet from glass 



"18 " " " 



4 Light records at 5 feet from roof and 10 feet from side 



5 Light records at 5 feet from roof and 10 feet from side 



" 5 " " " " 30 " " " 



6 Light records at 5 feet from roof and 10 feet from side 



" 5 " " " " 30 " " " 



3tJ0 

 355 



335 

 334 



259 

 254 



300 

 305 



260 

 270 



500 

 503 



LOSS OF LIGHT FROM GLASS, ETC. 



As might be expected, there is a loss of light in greenhouses 

 from reflection and other causes. The light lost from reflection 

 depends on the angle of the glass to the sun's rays, and as the sun's 

 altitude varies continually during the day and year, the light in- 

 tensity also varies. Moisture condensation, snow, frost, dust 

 and the composition and quality of the glass have a great influence 

 on the light, and light in turn affects the growth of the crop so 

 materially as to cause m.any different troubles. For \'ears v.'e have 

 been making numerous greenhouse tests in different parts of the 

 state in houses of different ages and types of construction, and dur- 

 ing this time have been studying these different conditions and 

 their relation to disease. 



In all cases the light conditions out of doors were com.pared 

 with those in the greenhouse, and the loss based on the differences . 

 between the two. Some of the results follow. 



