October, 1914-] 



thp: orchid world. 



21 



of spraying" plants, the yield of the crop, and 

 to a certain extent on fungous infection. 



" To obtain the best results in a house 

 running- east and west, the house should be 

 from 15 to 30 degrees north of east. This 

 enables the plant to take advantage of the 

 more intense mornmg light, and the crop can 

 be syringed with less danger from infection. 



" The difference in morning and afternoon 

 light may be shown by various chemical 

 methods, as well as by the growth of trees, 

 and of crops of cucumbers in north and 

 south houses. Other things being equal, a 

 crop will show greater development on an 

 east than a west expo.sure. 



" 1 here is considerable difference in the 

 light transmitting properties of glass. 

 Second quality, double thick greenhouse 

 glass transmits 18 per cent, less than No. i, 

 double thick, and the third quality double 

 thick transmits 33 per cent, less than first 

 quality anfl 15 per cent. le?s than second 

 quahty. 



" An irregular surface, bubbles, etc., in glass 

 act as lenses and affect the even diffusion 

 of light. 



" New glass is slightly superior to used 

 glass. The fleterioration frf)m dirt and other 

 factors is nnirh less than i })er cent, per 

 annum. 



" The more ncarl\' the angle of the roof 

 coincides with the right angle of the sun's 

 rays the more light is transmitted. 



" Relatively steep roofs are superior to flat 

 roofs for transmitting light. Records made 

 in February show that a house with a roof 

 angle of 46 degrees gave 18 per cent, more 

 light than one with a 32 degrees angle roof. 



" The reflection of light from surfaces varies 

 greatl}'. In our experiments we found 

 aluminium bron/c to constitute the best 

 reflector of light. 



"The practice of lapping glass causes some 

 loss of light, an average of i i per cent, in 

 our tests. 



"There appear to be no important dif- 

 ferences in the light of a greenhouse at 

 different distances from the glass, practically 

 the same light being obtained at 5 feet as at 

 30 feet. The light to be had directly under 



the glass, however, varies in intensity owing 

 to the irregularity of the surface. 



" The loss of light from glass may vary 

 from 1 3 to 36 per cent, or more, depending 

 on ihc c|uality and condition of the glass, 

 and many other factors. 



" Double glazed houses are much inferior 

 to those glazed with a single layer of glass." 



Masdevalliq Veitchiana, 



