THE FORCING GARDEN. 



551 



for their being removed, and placed down agam at pleasure. 

 These gratings are well adapted where the path passes along 

 above the flue, as they not only prevent the covers from being 

 broken, but also allow the free escape of the heat. Such 

 gratings have been adopted in the forcing-houses at Sion- 

 house, and have a very good effect. Their expense is not 

 more than that of neat well-made wooden footpaths, with this 

 advantage, that they look much neater, and will last ten times 

 as long. 



GLAZING AND PAINTING. 



It is necessary that all hot-houses should be glazed with the 

 best crown glass, as admitting a greater share of light to the 

 plants contained therein, and not with glass of an inferior qua- 

 lity, as was long the practice. Formerly less attention was 

 paid to this important point, and on the continent, to this day, 

 many extensive ranges of hot-houses are glazed with glass of 

 a very inferior quality. It appears, by the experiments of 

 Bouguer, that one-fortieth part of the light, which falls per- 

 pendicularly on the purest crystal, is reflected off', nor does it 

 pass through it ; it may be safely asserted, that green glass re- 

 flects off" moev than three-fourths. There is nothing gained by 

 using bad glass in the glazing of hot-houses, but evidently 

 much is lost. 



Various shapes have been recommended for the panes, or 

 pieces of glass, for which purpose the most reasonable is that 

 of the rectangular or curvilinear ; but for hot-bed frames, the 

 fragment form may be used as cutting less to waste. The 

 first of these is the original form, and is still the most fre- 

 quently met with ; the second looks neater, and has this ad- 

 vantage, that it aids in conducting the water which falls on the 

 roof to run down in the centre of the pane, by which means, 

 it is less likely to get into the house, between the glass and 

 the bars. 



In either case, it is of importance that the glass be cut 

 exactly to fit the space, which it is intended to cover, not 

 being put in too tightly, which renders it more apt to be broken 



