Chimneys

Vertical flues to remove hot or foul gases and products of combustion. In steam boiler practice they have usually a cro -section of one eighth the grate area discharging into them. Draft is caused by the greater weight of the column of cold air outside the chimney and of the same height. Experience has shown that a chimney 50 ft. high will burn 13 lbs. of coal under a steam boiler per sq. foot of grate per hour, and that each 10 ft. of added height will IMG:content-0857.jpg:[graphic] burn from 1.1 to 1.4 lbs. additional per foot of grate, up to 120 ft. in height (see