This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1899 Excerpt: ...of driving, but only to displace the air in the cylinder, which, in condensing, produced a vacuum on one side of the piston and allowed the pressure of the atmosphere to act on the other side. Since the days of Newcomen the name most intimately connected with the steam-engine is that of James Watt, and in his hands it assumed a shape and embodied principles which later engineers have not altered but only added to and improved. To show, therefore, that the main features and principle of the engine as laid down by Watt and his contemporaries differ only in detail from those employed by successive experimenters and designers will be the main object of this Paper. Watt began his study of the principles of Newcomen"s engine by investigating the quantity of water necessary to condense a given amount of steam, with the object of determining the temperature corresponding to various steam pressures. These experiments soon showed him that the Newcomen engine required more water to effect condensation than the volume of steam in the cylinder warranted. This apparent anomaly gave Watt his clue. Why should the engine in practice demand more condensing water than was necessary to condense the same volume of steam experi th« Ihst. O.b. Vol. cxxxvin. 2 A mentally? The only answer that reasoning gave was, that in some way more steam than the content of the cylinder was being used at every stroke. Further consideration pointed to the fact that when the steam was admitted into the cylinder a considerable amount was condensed by the walls cooled by the condensation of the previous stroke. The separate condenser was thus suggested as a means of preventing this excessive cooling and reheating of the cylinder, and Watt was led to announce his leading principle, viz., that at...