34 



shadows. The tests also show that large glass is superior to small, 

 — that single glazing is better than double, and that the shadows 

 cast by large purlins and heavy rafters affect the light. Tests 

 of this nature might be carried on indefinitely in various types of 

 houses, but this would not be necessary as the light may be quite 

 well detemiined by anyone familiar with the house. 



FIG. 6 — Showing cross section of an east and west house, about 36 x 200 

 f( , showing method of growing cucumbers. The light is much supenor in 

 a house of this sort. 



RELATIVE VALUE OF DIFFERENT TYPES OF HOUSES 

 FROM THE POINT OF VIEW OF LIGHT. 



From the results of our experiments with light in greenhouses it 

 is apparent that there are many imperfections in greenhouse con- 

 struction; but m.ost of them, it must be confessed, are difficult to 

 overcome. This not only holds true in regard to the m.atter of 

 greenhouse light, but of the ventilation, heat, etc. While great 

 general progress has been m.ade in greenhouse constrtiction during 

 the past twenty-five years, more will doubtless be made in the 

 future for an industry involving so m.uch capital cannot remain sta- 

 tionary. A more even circulation of air and heat, and better light 

 for special crops requiring a great deal, will be had, with other in- 

 novations rendering the plant less susceptible to disease. 



Since the sun's position in the heavens is continually changing, 

 it is practically impossible to secure the full benefits of the light 

 rays, although by modifications in the structure of the houses it is 

 possible to obtain m.ore light than at present. Som.e attem.pt has 

 been made to build high angle roofs for special crops such as roses, 

 but with the increased use of large houses this type of construction 

 has proved expensive and more risky. By far the largest num.ber 

 of houses run east and west, which allows a southern exposure to 

 the roof and side, and from the light point of view this type of 

 house we believe is superior to the north and south house. In the 

 latter type the east side gets the morning light and the west side 

 the afternoon light, while the ends, with the m.ore or less heavy, 

 light obstructing features, are exposed to the south. We are of 

 the opinion that more shad^ is cast in a house running north and 



