76 GARDEN FARMING 



Direction of the ridge. There are many different ideas in regard 

 to the direction of the ridge of the greenhouse. Many growers 

 contend for the uneven-span house with the ridge running east 

 and west, while others have equally as strong preferences for even- 

 span houses with the ridge running north and south. An analysis 

 of the problem of securing the maximum amount of light in a 

 greenhouse indicates that the even-span house, with ridge running 

 north and south and the angle of the roof such as to give the sides 

 a slope of about 45, is preferable to any other style of structure. 

 This style of structure allows a maximum amount of light to enter 

 the house in the morning and afternoon, when the sun's rays fall 

 almost perpendicularly upon the roof, and give the greatest reflec- 

 tion at noonday, when the sun is directly overhead and the rays 

 strike the surface at an angle equal to that of the pitch of the roof. 

 This type of house will admit more light than one with the long 

 slope to the south, even though the slope of the roof is such as to 

 form a perpendicular to the rays of the sun when at its lowest 

 point in the southern horizon. This is explained by the diurnal 

 revolution of the earth, which permits the roof to occupy the ideal 

 position for but one moment at midday on the shortest day of the 

 year. At all hours before and after noon the sun's rays strike the 

 roof with greater or less obliquity, being greatest early in the morn- 

 ing and late in the evening, thus tending to shorten the shortest 

 days of the year. The even-span house with ridge north and south 

 counteracts this tendency somewhat. 



The construction of solid benches. The construction of beds in 

 forcing houses is, as a rule, very simple. Planks, 3x12 inches, 

 are usually placed about 1 8 inches apart along the line of the walks 

 to form the sides of the bed. The planks are placed end to end, 

 the lower edge being sunk into the ground 3 or 4 inches. If a 

 deeper bed is desired, a second plank is placed on top in such a 

 way as to break joints, and is firmly fastened to stakes, preferably 

 cedar, which have been set in the soil. This boxlike compartment 

 is then filled to within an inch or so of its top with a fine compost 

 made from thoroughly decomposed turf and manure, in the pro- 

 portion of i part of manure to 2 parts of soil, except in the top 

 layer, where it may be made somewhat richer. A deep bed of soil 

 prepared in this way need not be removed for a number of years. 



