78 GREENHOUSE CONSTRUCTION AND HEATING. 
Of course, the putty must go in first. Use only the 
best, made of boiled linseed oil and whitening only, and 
work it till quite soft and smooth. By far the best 
method of glazing is to bed the glass in well, using 
plenty of putty, and pressing the edges of the glass 
down firmly, and when in and tacked, trim off the putty 
smoothly, both inside and out, filling up any cracks. 
Then when painting, let the side of the tool (brush) just 
catch the edge of the glass all along ; a roof thus glazed 
will not leak a drop, and require no care or attention, 
beyond an occasional coat of paint, for many years. Top 
putty is an endless nuisance and source of ‘‘drip”; 
under the heat of the summer sun it cracks and comes 
off wholesale, and then has, of course, to be replaced. The 
late Duke of Marlborough is said to have complained 
with reference to his numerous Orchid and other houses 
that he ‘had to spend six hundred a year in putty,” and 
though this may seem incredible, yet the annual renewal of 
‘‘top putty ” in an extensive range of houses, including the 
necessary labour and painting as well as material would soon 
run into three figures. By adopting the method recom- 
mended above, the noble Duke might easily have reduced the 
above amount by at least three-fourths. 
Always put the glass in with the concave side up— 
convex side down. Though apparently a small matter, 
this makes a great deal of difference in the ‘‘ tightness ” 
or otherwise of a roof, as the squares ‘‘sit down” very 
much closer and better in this way than any other, while 
the water is thus conducted to a great extent away from 
the bars. A truly flat square of glass, or one perfectly 
true at the edges, is very seldom met with. 
