Note 18 — INTRODUCTION.

(18) “A pint of water may be evaporated by two ounces of coal. In its evaporation it swells into 216 gallons of steam, with a mechanical force sufficient to raise a weight of thirty-seven tons a foot high. The steam thus generated has a pressure equal to the common atmospheric air; and by allowing it to expand by virtue of its elasticity, a further mechanical force may be obtained at least equal in amount to the former. A pint of water, therefore, and two ounces of common coal, are thus rendered capable of doing as much work as is equivalent to seventy-four tons raised a foot high.”