Mr. Thompson had a patent in 1796 for a furnace on the same principle as Watt's, but it was a less deviation from the ordinary construction. The fire-bars were made about one third longer than usual, and at two-thirds of their length from the front a low arch was thrown across the fire-place, under which the smoke rushed from the fore part of the fire, and was thus impelled through some intensely heated coked fuel, lying under and beyond the arch upon the bars, and was thereby consumed. By the management of a good stoker, this fire-place appears to us calculated to answer well.