134 



HOTHOUSE-BUILDING. 



them, on account of the perpendicular 

 sides being at a most unfavourable angle 

 to the sun's rays. We see no reason why 

 a whole garden, however large, may not 

 be enclosed within a glass covering 8 feet 

 from the ground. Yet even with this 

 height it would be found advantageous to 

 paint the interior white, and to introduce 

 reflectors of light to the fullest extent 

 possible. Loftier structures, no doubt, may 

 be indulged in by those who wish to grow 

 timber trees within them. In botanic 

 gardens there may be a plea for growing 

 such specimens ; in gardens for the pro- 

 duction of fruit and flowers there is none. 

 One of the reasons why plants thrive so 

 much better in pits than in large and lofty 

 houses, is their nearness to the glass ; and 

 this is also the reason why peaches and 

 grapes are grown by being trained close 

 under its inner surface. All good culti- 

 vators place their most choice and delicate 

 plants as near to the glass as possible ; and 

 one of the most successful of all our pine- 

 growers keeps his plants so near the roof 

 as to be compelled to take out a square 

 of glass occasionally, to allow the crown 

 of the fruit to shoot up through into the 

 open air. While all kinds of theories 

 have been started, and experiments made, 

 on hothouse building, few have bestowed 

 a passing thought on the distance that the 

 light rays will penetrate into a glass house. 

 The angle of elevation has been carefully 

 calculated; the extent of radiating sur- 

 face, and the length of pipes for securing 

 the necessary amount of heat, have been 

 determined ; yet, so far as we know, no 

 one has yet calculated one of the primary 

 necessities of vegetable existence, when 

 subjected to artificial treatment. "The 

 heat of the sun is the cause of growth, and 

 its light the cause of maturity, in the vege- 

 table kingdom;" yet no one can say 

 whether the beneficial effects of light ex- 

 tend to the distance of 6 inches or 60 feet 

 beyond the inner surface of the glass. 



Hothouse trellises. — Trellises for training 

 trees to in hothouses were long made of 

 timber, which was both expensive and 

 heavy in appearance, while it also re- 

 quired frequent repairs. This material is 

 seldom now used, having given place to 

 copper or galvanised iron wire run 

 through wrought-iron studs, brackets, or 

 upright supports. The advantage of the 

 former is, that it is not liable to rust, on 



which account it has been much used for 

 trellising garden walls as well as hot- 

 houses. The recent improvements by 

 which iron is coated with glass, copper, 

 brass, lead, zinc, &c, may not inappropri- 

 ately be applied to trellises for such pur- 

 poses. Iron wire of the common sort is 

 now pretty well supplanted by what is 

 called " prepared charcoal wire," which is 

 so prepared that its elasticity is pre- 

 served, upon which so much depends. 

 Galvanised wire is also now used, as the 

 process to which it is subjected greatly 

 prevents oxidation. All iron trellises, if 

 not prepared as above, should be regu- 

 larly painted with anti-corrosive paint, 

 which may be made of any colour. 



The direction of the wires should 

 always be vertical or horizontal, and all 

 whimsical forms should be disregarded, 

 as only increasing expense without one 

 rational advantage. 



For various modes of constructing 

 trellises, vide art. Espalier Rails. 



§ 2. — THE ANGLE OF ELEVATION. 



Regarding the angle of elevation— that 

 is, the proper slope of glass roofs — much 

 has been said and written, and little has 

 been done to carry the correct theory 

 into general practice. Hothouse builders, 

 in general, content themselves by deter- 

 mining the length, breadth, and height 

 supposed to be most convenient to exist- 

 ing circumstances, without troubling 

 themselves further, or without going into 

 those mathematical calculations necessary 

 to arrange the slope of the roof to the 

 latitude of the place, or the purpose for 

 which that roof is intended. Hence the 

 same angle of elevation is found in Corn- 

 wall and in Ross-shire, the difference in 

 latitude and the suns inclination being 

 seldom thought of. 



This subject appears to have attracted 

 the attention of Boerhaave about the 

 beginning of the last century, and was 

 taken up by Linnseus, and still further 

 pursued by Faccio, Adanson, Miller, 

 Speechly, and Williams of New York. 

 The late T. A. Knight published hints on 

 this subject in the first volume of " The 

 Horticultural Society's Transactions ; " 

 and Sir George Mackenzie, in 1815, deter- 

 mined " that the form of glass roofs best 



