2099. Where small panes of glass are used, common sash glazing is generally performed with a lap of from one fourth to three fourths of an inch, and the space between the panes of glass is generally filled up with either putty or lead. A mode, however, was suggested in the Gardeners' Chronicle for 1844, of having the glass of each pane cut with a perfectly straight edge, and placing them so that they shall all fit exactly. 'When the light is completed, the surface of the glass is perfectly level, and there are no interstices in which the dust, &c., can accumulate, or for the deposit of moisture. By this means, one cause of considerable breakage in frosty weather is entirely avoided; and if a pane of glass be accidentally broken, the fracture does not necessarily extend beyond that pane, as each pane is independent of the others. The whole is a very firm and compact, and the glass is not liable to shake out.' (J. L. Snow in the Gard. Chron. for 1844, p. 277.) According to the old mode of glazing, the panes in hothouse roofs had frequently laps a full inch broad. Nothing could be worse than this plan; as the broader the lap, the greater was the quantity of water retained in it by capillary attraction; and when such water, from a deficiency of heat in the house, became frozen, the glass was certain to be broken. In other cases the broad lap soon filled up with earthy matter, which was not only unpleasant to the eye, but injurious, by obstructing the light from the plants.
