August 
THE COTTAGE GARDENER 
257 
light and heat, upon any surface, will be in propor¬ 
tion to the perpendicularity of those rays to that 
surface. If a thousand rays strike perpendicularly 
upon a surface of the best crown glass, it is calcu¬ 
lated that all will pass through it with the exception 
of a fortieth part; but if the same rays fall obliquely 
the number altogether reflected will be in proportion 
to the size of the angle formed by each falling ray, 
and a perpendicular lino from the surface on which 
it falls. Thus, according to Bonguer, if the angle of 
incidence so formed is 50°, the rays altogether re¬ 
flected will be 57; but if the augle is 85°, the 
number reflected will be 543 in the thousand. Hence 
the importance of having steep and narrow houses 
for early and late work. A roof sloping at an angle 
of 45° has been a favourite with gardeners for gene¬ 
ral purposes, not as a mere matter of imitation, but 
embodying the wisdom of avoiding extremes, and 
taking a middle course. The sun will strike upon 
such an inclination perpendicularly in the beginning 
of April and September, and will not be very oblique 
for a considerable time either before or after these 
periods. Mr. Knight, to whom we are all so much 
indebted, in order to have the greatest amount of 
sun in early houses l'or ripening their crops in June 
and July, constructed separate houses with an angle 
of 28° and 34°. For very early forcing nothing 
beats the old Dutch narrow houses, where the roofs 
formed an angle with the perpendicular line of from 
15° to 25°. For those not conversant with the mat¬ 
ter, it will bs useful to remember that a perpendicu¬ 
lar height, above where the sloping sash rests in 
front, equal to the width of the house will always 
give an angle of 45° between the sloping glass and 
the perpendicular line. Thus, in the annexed figure, 
if a b and b c be twelve feet, the angle as at d will 
be 45°. If it were desirable to give a house of simi¬ 
lar width an angle of 30°, e, the perpendicular line, 
must be elevated to /, as shown in the dotted lines 
beg and fa. To prevent the necessity of having 
such staring exposed objects in our gardens, it is 
customary to lessen the width of the house, which of 
course decreases the necessary height, and also to 
join the sloping roof to a short-hipped one, either 
opaque or, better still, of glass, as shewn at g. For 
a house or pit of the same width, with an angle of 
inclination of 70°, h, the perpendicular, will only 
require to be feet higher than at the front, as shewn 
in the dotted line k a: decrease the width and the 
necessary height will be lessened in proportion. 
“ Why,” says Mr. A., “ there is in Mr. B.’s 
vinery a fine crop just now changing colour, and 
the roof is as flat as Mr. Fish represents as an angle 
of 70°.” True ; at this season, provided your plants 
are near the glass, any inclination of roof will do. 
But \voukl you succeed so well with the same amount 
of trouble and expense as with a steep roof, if you 
wished to cut fruit in May and June? Will Mr. B. 
preserve his grapes hanging through the autumn 
and winter as easily as he would have done if his 
glass roof had been so steep that neither outside nor 
inside would retain moisture except in wet weather? 
Cucumbers have been cut in the winter from frames 
and pits witli the glass at an angle of 80°, and 
strawberries have been gathered in similar places in 
March and April; but I submit that neither results 
could be depended upon so surely as if the angle 
had been from 25° to 40°. I am more than blessed 
with flat-roofed houses—the steepest having the angle 
of inclination about 47°; and that is the only place 
I can fully depend upon for setting early strawberries 
in February and March. I should like an angle for 
this purpose 10° less. The folly of flat structures 
for early work is constantly obtruding itself. In a 
pit with an angle of 80°, in winter and early spring 
half of the light and heat from the sun never pene¬ 
trates the glass. As the sun rises in altitude they 
answer admirably during summer. I do not advise 
you to pull your houses about, but, if erecting new 
ones, you will be none the worse for pondering these 
matters. Robert Fish. 
Fruit-tree Borders. —Mr Bailey, gardener to 
the Archbishop of York, after giving honourable tes¬ 
timony of our coadjutor, Mr. Errington, being “ one 
of our most skilful gardeners,” gives an epitome of 
his own experience in the formation of fruit borders, 
and we quote this chiefly to show our readers how 
entirely two first-rate authorities agree upon this im¬ 
portant point. The following, it will be seen, is 
quite coincident with what Mr. Errington enforces 
in these pages. “ I have paid much attention to the 
management of fruit-tree borders, and feel convinced 
that the great object we should have in view is, to 
secure a shallow stratum of sound pure loam on a 
dry and impervious bottom; to avoid mutilating the 
surface roots by cropping the border with vegetables; 
not to apply rank and stimulating manures; and to 
keep the mass of soil always open, healthy, and per¬ 
meable to the sun, air, and rain, using especial pre¬ 
caution that excess of the latter is not permitted to 
saturate the soil. Nothing, in my opinion, is more 
injurious to wall-trees than the heavy cropping of 
the borders in which tlroy are planted.”— Journ. of 
Hort. Society, iv. 208. 
