Light in Greenhouse Culture 57 



than an inch. This system practically excluded fifty 

 per cent, of the light. The modern house uses glass 

 varying in dimensions from 16 inches by 24 inches, 

 20 inches by 30 inches to 24 inches by 24 inches. 

 With the use of the larger glass, the diminished 

 lapping results in a considerable saving of light. 

 To prevent breakage of the larger glass a house must, 

 of course, be solidly built and well purlined. 



The location of the house, too, influences the 

 amount of light taken in. Houses located north and 

 south are benefited by the morning light only, 

 whereas those running west receive only the after- 

 noon light. The ideal location from the light view- 

 point would be to set the house on a line running 

 20 to 25 degrees north of east. 



Houses with greater roof angles naturally receive 

 more light. It is also a well conceded fact that 

 light will pass through a transparent object more 

 easily if it is placed at right angles to the light 

 rays. This fact is not often taken advantage of 

 by greenhouse builders. However, it cannot be de- 

 nied that the sunlight strikes the house at differ- 

 ent angles during the day and likewise at differ- 

 ent seasons of the year, thus producing considerable 

 variation in the amount of light reflected. To obvi- 

 ate this, houses should be built with greater roof 

 angles, a plan which will insure less reflection and 

 thus allow a greater amount of light to penetrate. 

 During Januar}', for instance, when the normal sun- 

 light is naturally less, glass placed at an angle of 



