On the Glazing of Hot-houses and Conservatories. 245 



that I have seen half the panes of a green-house destroyed 

 in this manner in the course of one winter. This evil is 

 sometimes attempted to be remedied by making the lappings 

 very narrow, but in this case, when rain is accompanied by 

 high wind, a considerable quantity of water is found to pe- 

 netrate into the house. The circular glazing is free from all 

 these defects, which it possesses the merit of obviating in a 

 manner equally simple and efficacious. Who was its con- 

 triver, I have not been able to ascertain, but I believe it to 

 be an old invention recently revived ; and the principle has 

 been used for ages in weather-tiling the fronts of houses, as 

 may be seen in many old buildings in country towns. The 

 whole contrivance consists in cutting the upper and lower 

 edges of each pane into the shape of the segment of a cir- 

 cle, the lower convex, the upper concave. (See figure 1.) 

 To effect this with the greater truth and facility, a trammel 

 should be made of the length of the radius of the intended 

 segment of a circle, and perforated at its extremity by a small 

 hole of the proper size, for the insertion of the glazier's 

 diamond. It being then made to traverse upon the sur- 

 face of a smooth board, the glass is easily cut to an accurate 

 curvature. But as both the upper and lower edges of the 

 pane must be of the same degree of curvature, and it should 

 remain, during the operation, unmoved, with the glazier's 

 hand kept steadily upon it, the trammel must admit of a 

 rectilinear as well as a circular motion, which is effected by 

 a very simple contrivance, for which I am indebted to Mr. 

 Wenman, Nurseryman of South Lambeth. A deep groove 

 being accurately cut down the middle of the board, rather 

 longer than the panes intended to be operated upon, a small 



