Author Description

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. 1832 Excerpt:...before it can act upon the piston. We know from experiment that steam rising from water, heated to the boiling point or the temperature of 212 of Fahrenheit, will balance the pressure of the atmosphere; or, which is the same thing, press against the piston with a force equal to nearly 15 lbs. on every square inch; 2 lbs. above this, 17 lbs. is the force employed in the condensing or low-pressure engines; but in those which have no condenser the water in the boiler is heated considerably beyond the boiling point, acquires a very great expansive force, and exerts a proportional pressure on the piston; it is sometimes carried so far as to work the piston with a pressure of 60 or 80 lbs. on every square inch. This highly elastic steam entering alternately at each end of the cylinder, will drive the piston backwards and forwards notwithstanding the pressure of the atmosphere; and no condenser being used, the steam escapes through a tube called a waste-pipe. It is easy to conceive that the greater the elasticity of the steam, the greater is the chance of the boiler bursting; but the cheapness of these engines, owing to the simplicity of their construction, and the convenience of occupying a comparatively small space, makes them still occasionally adopted. EMILY. The additional quantity of fuel required to bring the water to so high a temperature, and the total loss of the steam, would, I should have thought, more than have counterbalanced the advantage of cheapness in the original cost of the engine. MRs. B. In coal mines, in which such engines have been used, the quantity of fuel is scarcely a consideration. Within these few years, Mr. Wolfe has constructed an engine, consisting of the high-pressure, and the condensing engine united together. The steam of the fi...