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. 1848 Excerpt: ...expenditure of steam under different circumstances must lead to considerable errors. If a boiler, as in the Cornish engines, is adapted to raise the bob 7 times per minute, and owing to some cause, as the water not being able to get away, the bob is raised only 5 times per minute, there is two-sevenths in favour of the boiler; or if an engine adapted for 30 strokes per minute makes only 25 occasionally, there is great difficulty in comparing it with other engines. Mr. Donkin urged the necessity of keeping the quality of the engine and its commercial effect perfectly distinct; if a given weight be raised to a given height, it must produce a given effect minus the friction; in water-works engines the resistance opposed by the friction is very considerable, and being very variable,...