PLANTS, WITH GLASS ROOFS. 



157 



so as might be expected, because the sash-bar can be formed lighter, 

 and where crown-glass is used the panes may be much smaller. For 

 plant-houses the advantage of admitting the sun's rays perpendicu- 

 larly, early in the morning and late in the afternoon, will much more 

 than compensate for any additional expense. In an architectural 

 point of view the merits of this mode of roofing are perhaps as great 

 as they are with reference to culture : the roofs being lower, are less 

 conspicuous, and the common shed-like appearance is taken away by 

 the pediments which form the ends of the ridges, and appear in a 

 range as a crowning parapet to the front glass. Indeed, if it were 

 desirable, the tops of the ridges might be made perfectly horizontal, 

 and all the slope that is necessary for carrying the water from back 

 to front, or to both the sides, given in the gutters between the ridges, 

 as is done in roofing common buildings of great width. Fig. 130 is a 



Fig. 130. 



Perspective view of the original ridge and furrow house at Chateworth. 



perspective view of a house erected by Sir J. Paxton, at Chatsworth, 

 and fig. 131 a vertical profile of part of two ridges of the roof. It will be 

 observed that the sash-bar is not in a direction parallel to the pedi- 

 ments, but oblique to it. This is done to prevent the water from 

 running down on one side of the glass, which it would do in conse- 

 quence of the general slope of the ridge from the back to the front if 

 the bars were placed at right angles to the ridge. The angle at which 

 the bars are fixed will vary with that formed by the slope of the ridge, 

 and the mode of determining it is to place the bars so that the lap of 

 the glass, which is in square panes, may form, when the panes are 

 fitted in their places, lines truly horizontal. There are many persons, 

 however, who attach no great importance to causing the water to run 

 down the middle of the glass instead of one side ; and they will, of 



