MARCH. 73 
north and south, which should always be the case, unless special reasons 
exist for placing them towards different points of the compass. 
Oiie great advantage of this form of roof for forcing houses is, that, 
directly the sun rises above the horizon its rays pass into the house 
through the eastern slope of the ridges, presenting a plane at a favour¬ 
able angle for its direct transmission, by which the houses get both 
warmth and light early in the morning; whereas, houses whose angle 
faces the south can only admit the sun’s rays direct for a few degrees 
east and west of that point, and two or three hours of sunlight are 
therefore lost each morning, owing to the oblique angle with which its 
rays strike the roof. Those who, like ourselves, have the management 
of forcing houses, will know that fires must be lighted each morning in 
March and April, to warm the house until the sun gets power enough 
to do so; and by the time we have the apparatus fairly at work the 
sun gets round, and though the fires are checked yet a certain amount 
of fuel is burnt to waste; but with the ridge roof it is all but probable 
that, in consequence of the early hour at which the heat of the sun can 
warm the house, fire-heat, if not altogether dispensed with, w r ould be 
only required for a less time, and much less in amount, than would be 
the case with lean-to houses ; and so with the afternoon sun, whose 
rays will pass nearly direct through the western face of the ridge up to 
sunset, till the vernal equinox, and after that period will continue to 
impart a warmth to the building long after its rays would almost be 
lost to a house with a southern angle only. This afternoon sun will 
very materially assist in keeping up the night temperature, rendering 
less fires necessary, and of course reducing the cost of working. These 
are important advantages bearing on the economical management of 
forcing houses, which should not be lost sight of by parti s interested in 
the efficiency and cheapness of fruit growing. 
We must next consider how the ridge and furrow roof will stand a 
comparison with the ordinary lean-to house, as regards the loss of heat 
by radiation. The loss of heat by radiation from all descriptions of 
glass erections will be in proportion to the surface exposed to the atmo¬ 
sphere, other conditions being the same; let us therefore take a block 
100 feet square, covered with a ridge and furrow roof, the ridges 
having a 10 feet span, and three sides of the building having upright 
glass six feet high resting on a four feet parapet wall; we shall find 
the surface area of the roof and sides, in round numbers, about 14,000 
square feet. To cover the same surface with glass, in the shape of 
lean-to houses, would require a range 600 feet in length by 16 feet 
wide, or rather (as one entire range of this length would be incon¬ 
venient to manage) let us say six ranges of 100 feet each, and, 
allowing for the width of roof, 19 or 20 feet, and adding thereto the 
upright front glass and ends, the surface of glass exposed will be greater 
in the lean-to houses than in the block, and the loss by radiation will 
therefore be increased in proportion to the larger surface exposed. The 
question of the air in forcing houses cooling through the medium of the 
glass roof is not owing, however, altogether to radiation, but to con¬ 
densation as well. The heated air of the house as it comes in contact 
with a cold body, i. e., the roof, is condensed and converted either into 
