552 



DETAILS OF CONSTRUCTION. 



external coverings, if properly applied, 

 effect a saving of nearly nine-tenths of the 

 fuel, and that a better and more certain 

 temperature is maintained even when the 

 thermometer sinks to from 15° to 24° of 

 frost, Reaumer — that is, below zero by 

 Fahrenheit's scale. All coverings, to be 

 most effective, should be impervious to 

 water, and of non-conducting materials. 



The following description and illustra- 

 tion, fig. 788, will explain a method of 



Fig. 788. 



covering span-roofed hothouses much 

 used throughout the north of Europe ; 

 nor is it span-roofed houses alone that are 

 thus covered, but lean-to houses also, as 

 well as pits of every description. The cov- 

 erings formerly used were wooden shutters 

 and straw mats set in frames ; but felt is 

 now common, making not only a much 

 more economical, but, at the same time, 

 more convenient kind of covering, a is 

 a section of a rafter constructed for this 

 purpose, in which b b are the glass sashes ; 

 c c the felt or other covering made into 

 frames the exact size of the sashes, and 

 put on every evening during winter, and 

 removed again in the morning, unless the 

 weather is exceedingly cold, and much 

 snow has fallen ; d another section of a 

 rafter for the same purpose, the fastenings 

 of the shutters being rather different ; e e 

 the sashes as before, and // the covering, 

 which in this case is not kept down by the 

 coping as in a, but the top ends of the 

 shutters run under the coping of the 

 ridge at g, and the bottom part is secured 

 by a button on top of the rafter in a 

 variety of ways, which will suggest them- 

 selves to the intelligent gardener. A pro- 

 vision is made for closing in the space 



between the bottom rail of the shutter and 

 the top of the bottom rail of the sash, by 

 a piece of wood suited to the purpose. 

 This is intended to prevent too much cold 

 air entering between the shutters and the 

 lights, or rather to keep such air in a quies- 

 cent state — a precaution very necessary in 

 cold climates, and not to be disregarded 

 in our own. The side sashes are also 

 covered, as shown by the dotted lines, and 

 are secured to the mullions by means of 

 wooden or iron buttons, or screw, as shown 

 at h. These side shutters are let into a 

 groove in the top wall-plate, and into a re- 

 bate in the lower one. In the extensive nur- 

 series of the Messrs Booths of Hamburg, 

 both top and side shutters are so arranged, 

 but a circulation of air is allowed to flow 

 between the shutters and sashes from the 

 parapet wall to the ridge — which should 

 not, however, be the case. Such contriv- 

 ances have been occasionally used in this 

 country for years, and may be employed 

 to great advantage in excluding frost from 

 heath-houses, greenhouses, &c, so as to 

 dispense with fire heat entirely ; and in 

 forcing-houses their use will lessen the 

 consumption of fuel, as well as the peril- 

 ous effects of too much artificial heat 

 during the night. 



Patent felt shutters are used extensively 

 in the gardens at Dalkeith ; and we be- 

 lieve that heaths, camellias, azaleas, and 

 many Japan, Chinese, and New Holland 

 plants, would succeed much better if the 

 glass roofs were so covered, than by the 

 application of fire heat. Should the frost 

 at any time get in, the covering should be 

 left on until it has thawed, and the plants 

 will be found to have sustained little or 

 no injury. The most expeditious method 

 of covering and uncovering the roofs of 

 houses and pits would be, to have thick 

 canvass rendered waterproof, and mount- 

 ed on rollers, so that it could be run up 

 or down when required. 



We have stated at the commencement 

 of this article that coverings were used 

 many years ago : we may instance those 

 in the garden at Abercairney so early as 

 1800. Amongst the hothouses was a 

 pine-stove, with rafters constructed exactly 

 like those shown at fig. 788, a. The shut- 

 ters used were wooden frames of the exact 

 size of the sashes, and these were covered 

 with strong canvass or sailcloth, and 

 painted with oil-colour, notwithstanding 



