Quarterly Papers on Engineering Volume 3 (Paperback)

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. 1845 Excerpt: ...regarding heat as an agent, which, whilst it exerts mechanical force, undergoes no change. This extraordinary fact Ericsson exemplifies by a simple but conclusive illustration; for the readier reception of which, by the audience, it will be well to introduce particular dimensions. Suppose the piston of an ordinary steam engine cylinder to be at the bottom, and suppose the force of the steam intended to be admitted into this cylinder under the piston to act with the force of 100,000 pounds, which is the force on a piston of fifty inches diameter, acted upon by steam of fifty pounds' pressure to the square inch. Suppose the cylinder to be ten feet long, and the piston to be loaded with a weight equal to these 100,000 pounds. If, now, a sufficient quantity of steam of the stated pressure be admitted from below the piston, this load will be elevated through the whole length of the cylinder; and hence we shall have raised a weight of 100,000 pounds through a space of ten feet. But who will contend that this immense amount of mechanical force has required any expenditure of heat? Does not the steam, after having lifted this weight, contain just as much heat as it did before leaving the steam boiler--less only the losses by radiation? And does not that heat retain all the properties after the operation which it possessed before? Am I, then, incorrect in stating that we have obtained this power without changing the nature, or diminishing the energy of the heat employed? But although nature has furnished us with an agent of such extraordinary properties for the production of mechanical force, how imperfectly do we employ it In the low-pressure engine, we turn the steam, after having performed its good office, into a condensing apparatus, where the heat is in a mann...