Note 1 — Chapter I · PRELIMINARY MATTER.
Reading edition
(2.) The physical effects most intimately connected with the operations of steam engines are some of the mechanical properties of atmospheric air. The atmosphere is the thin transparent fluid in which we live and move, and which, by respiration, supports animal life. This fluid is apparently so light and attenuated, that it might be at first doubted whether it be really a body at all. It may therefore excite some surprise when we assert, not only that it is a body, but also that it is one of considerable weight. We shall be able to prove that it presses on every square inch[1] of surface with a weight of about 15lb. avoirdupois.