CHIMNEY DRAFT.
Cornish boilers, slow rate 4-6 lbs. per sq. ft. per hour.
Cornish boilers, ordinary rate 10-15 lbs. per sq. ft. per hour.
Factory boilers, ordinary rate 12-18 lbs. per sq. ft. per hour.
Anthracite coal, quick rate 15-20 lbs. per sq. ft. per hour.
Bituminous coal, quick rate 20-30 lbs. per sq. ft. per hour.
Marine boilers, ordinary rate, 15-25 lbs. per sq. ft. per hour.
Water tube boilers 10-25 lbs. per sq. ft. per hour.