In figuring the weight of windows, the weight of the glass may be taken at 3 pounds per square foot for plate glass, 1 1/3 pounds for double strength glass and 1 pound for single strength glass.

For the weight of the wooden sash, add together the height and width of each sash (in feet) and multiply by 2.1 for 2-inch sash; 1 2/3 for 1 -inch sash, and 1 /3 for 1 3/8 -inch sash.

The above data is sufficiently accurate for determining the size of sash cords and pulleys, but the weights should be determined by weighing each sash after it is glazed as the weight of the glass will vary considerably.

Sash Weights. - The weights ordinarily used for balancing windows are made of cast iron, in the form of a solid cylinder, 1 or 1 -inches in diameter, with an eye cast in the upper end. The length varies with the weight.

Ordinary weights have very rough eyes for the sash cords. There are a few manufacturers in the East that make weights with a patent eye that will not cut the cord.

Lead Weights. - It often happens that for wide and low windows the weights if of iron would be so long that they would touch the bottom of the pocket before the bottom sash was fully raised. In such cases lead weights are usually resorted to, lead being 80 per cent. heavier than cast iron. By casting the weights square, whether of iron or lead, considerable saving can be made in the lengths.

The Raymond Lead Co., of Chicago, makes a specialty of compressed lead sash weights, with wrought and malleable iron fastenings centred so that the weight will hang perfectly plumb, and when lead weights are necessary the architect will do well to specify their weights.

In hanging the sashes the weights for the upper sash should be about pound heavier than the sash, and for the lower sash J pound lighter.