GENERAL MANAGEMENT OF GREENHOUSES. 
131 
as to turn over each joint about a quarter of an inch. The glass is bedded in putty on 
the top of the sash -bars, and a little white lead is put under d, e, and when turned 
down, it is rendered completely waterproof. C is intended to show 'the plan of 
the slides on the roof for giving air. f is the top of the slide ; g, the top of the 
roof. By this plan the slide can never be blown off, and the appearance of the 
whole is light, because there is no projection of wood above the glass. 
The system of Messrs. Harrison and Curtis which we noticed in the Horti- 
cultural Register, Vol. I., p. 10, is intended to answer the same purpose as 
Mr. Saul’s. In making lights on this principle, the outer frame of the sash is 
made in the usual way, and rabbeted at the inside of the head and side-tiles of 
the frame or sash, to receive the outside edge of the glass; the inside of the 
frame is furnished with bars, the upper surfaces of which are flat, and made even 
with the rabbet, a, a, at the sides and head of 
the frame. The glass is cut in squares so that 
when placed on the bars it meets quite close 
at the edges up the middle of the bars, b, b, 
and close to the sides of the rabbet, a. In this 
process of glazing, a very thin coat of putty is 
laid on the surface of the bars, upon which the 
glass is placed, and then pressed down, so as 
to leave the least quantity possible remaining 
at the under side of the glass. The squares 
are secured by means of a metallic screw. A, 
and lead- collar, B, screwed on at each angle 
c, c, the lower edge of the collar being bent 
down to hold the glass in its place. On this 
method there is no midrib above the glass: 
there is much less shade than in the old plan. 
The evils naturally attendant on the cracking of the putty, its separating from the 
wood, and admitting water to enter and drop into the house, are all entirely pre- 
vented ; it also dispenses with the renewal of putty, or having to paint the outside 
of the frame, which is an annual saving in expense, and keeps all the materials 
under the glass quite dry. 
But there are important objections to this system : 
1st. The screws at the angles of the squares of glass become in a little time so 
fast by being rusted in, that they cannot be got out but by violent means, at least 
this is the case with those lights in our possession glazed on this principle. So that 
when there is occasion to repair, much trouble and inconvenience is experienced. 
2ndly. There requires much minuteness in cutting the squares of glass, so as to 
make them exactly meet upon the midrib, for if any crack remains, the water will 
find its way betwixt the putty and glass. 
It is necessary that every facility should be afforded for increasing the tempe- 
rature of the house in severe weather. For although artificial heat should never be 
had recourse to for green-house plants if it can be avoided, because they thrive far 
better without it, yet in times of sharp frost, excessive dampness, or the like. 
