THE TEMPERATE HOUSE 
151 
Green-tinted 
Glass. 
the erection of the south wing was sanctioned. It was completed 
in 1897. Soon afterwards the north wing was commenced; and in 
1899 the whole building stood completed, nearly forty years after 
the first “ footings ” had been laid. Each wing is 116 feet long, 
64 feet wide, and 38 feet high. A porch 12 feet by 8 feet is built at 
the entrance to each wing. The total length of the building is 628 
feet, and its greatest width 164 feet. The cost of the wings was about 
£14,000, bringing the total cost of the entire building up to £43,000. 
It covers about if acre. Each of the three great divisions is kept 
at a different temperature. The coolest is the northern one, or 
Himalayan House, which is not much warmer than the air out-of- 
doors. The warmest is the south wing, or Mexican House, which is 
semi-tropical. The big central block is intermediate. 
In a plant-house of the character of the Temperate House at Kew 
there are three essential factors on which, more than any other, 
the health of the plants depends : these are adequate 
light, ventilation, and drainage of the soil. When the 
Palm House was built, a suggestion — an unfortunate 
one, as it proved — was made by Mr. Robert Hunt, F.R.S., that the 
roof glass should be tinted green. The idea was that by intercepting 
the heat rays the scorching effect of the sun in bright weather might 
be tempered. Whilst doing this, however, it also reduced the quan- 
tity of light in winter and in dull weather, when every ray of light 
is precious. The suggestion was adopted and, in spite of the doubts 
of practical gardeners, the use of green glass in Kew continued for 
over forty years, not only in the Palm House, but in the Temperate 
House, Ferneries, and other houses as well. About 1887, however, 
the use of colourless glass was resumed, and the effect was soon 
apparent in the improved vigour of the plants. Experience has 
shown that in large airy houses like the Palm House and Temperate 
House, the fiercest sunshine ever obtained in Britain is powerless 
to injure the ordinary plants growing therein, even when the glass 
is pure. 
The second thing which, we have said, is essential to a plant-house 
of this description is ventilation. It has always to be remembered 
that many of the plants growing in the central and 
north divisions would thrive perfectly well — or even 
better — out-of-doors for at least four months of the year. The free 
admission of fresh air during warm weather is indispensable to success. 
Ventilation. 
