82 GREENHOUSE CONSTRUCTION AND HEATING. 
manner to that described above. The walls are of concrete, 
the ends of the bars being bent as shown in the 
accompanying sketch (Fig. 61), and bedded firinly in the 
concrete. The upper ends of the bars, or rafters, are kept 
at the proper distances by means of 
an ordinary ridge plank, into which the 
bars are let slightly, and the glass, 
which is 24 inches wide, is bedded in 
putty and secured by means of clips. 
Another method of glazing with iron 
bars is shown in Fig. 62. Here the 
. bars are formed of angle-iron (lin. 
TRE Es to 1in.), and run horizontally, as 
shown in the sketch, being supported by stout vertical 
rafters of 4in. by 3in. or 5in. by Sin. stuff, into which 
the lower flange is let, or to avoid weakening the rafters, 
the pieces may be cut out at the proper points. In either 
case the flat side is 
secured to the rafter by 
a stout screw. The 
glass, which must be in 
tolerably large squares, 
and be cut perfectly 
true at the edges (these 
being simply butted 
together), is fastened 
by means of > Fig. 62. 
shaped clips of stout zinc, as shown at B in the sketch. 
This makes a nice light house, suitable for pelargoniums 
and other plants that require free ventilation and abundant 
light, and as no putty is required, the glass is very quickly 
