GLASS .STRUCTURES AND APPLIANCES. 



47 



The stages, vmtil a comparatively recent date, 

 were mostly made of wood. This answered well 

 wMle it lasted, which, however, was not long, owing 

 to its being so constantly subjected to being wetted 

 and dried. It is this alteration of condition that 



bearers, with slate, stone, or concrete shelving and 

 staging, in lieu of wood. Beautiful castings of chastely 

 designed patterns, from six inches to two feet or even 

 a yard wide, may now be had for the purpose of 

 plant-staging. The frames of the stages are also 



Fig. 25. — A House-top Cokseevatort near the Straiid. 



proves so fatal to the durability of timber. Kept 

 either dry or wet, good red deal, which was mostly 

 used for plant-stages in green-houses, lasts a long 

 time in good condition. But no care in nse nor 

 in painting could keep plant-stages from the trials of 

 a daily, almost an hourly change in their conditions. 

 Hence their rapid decay, and consequent expense 

 and risk of accidents. 



These have led to the general selection of iron 



formed of cast or wrought iron resting upon stone. 

 Such shelving may be said to be practically in- 

 destructible, and is as porous as it is dvirable. 



Slate, stone, and concrete slabs have also been 

 used on the iron framework or bearings of stages. 

 These, however, are said by cultivators to be cold, 

 and they are certainly not popular. 



Plants do not thrive so weU on slate, stone, or 

 concrete stages as on those of iron or wood. Nor is 



