The Steam Engine Explained and Illustrated (Seventh Edition) / With an Account of Its Invention and Progressive Improvement, and Its Application to Navigation and Railways; Including Also a Memoir of Watt

by Dionysius Lardner

FOOTNOTES:

[9] This pipe is represented as proceeding from the force-pipe above the cistern C, in the perspective view of Savery's engine at the head of this chapter.

[10] Hot water being lighter than cold, floats on the surface.

[11] "Captain" is a title given in Cornwall to the superintendent of the works connected with a mine.

[12] As the calculation of the power of an engine depends on the number of square inches in the section of the piston, it may be useful to give a rule for computing the number of square inches in a circle. The following rule will always give the dimensions with sufficient accuracy:—Multiply the number of inches in the diameter by itself; divide the product by 14, and multiply the quotient thus obtained by 11, and the result will be the number of square inches in the circle. Thus, if there be 12 inches in the diameter, this multiplied by itself gives 144, which divided by 14 gives 10⁴⁄₄₄, which multiplied by 11 gives 115, neglecting fractions. There are, therefore, 115 square inches in a circle whose diameter is 12 inches.

[13] The external cylinder is not represented in the diagram.

[14] Also called the snifting valve, from the peculiar noise made by the air and steam escaping from it.

[15] Also called the injection valve.

GREENOCK, IN 1824.

[CHAP. III.]

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[TOC] [INX]

PROGRESS OF THE ATMOSPHERIC ENGINE.—SMEATON'S IMPROVEMENTS.—BRINDLEY, ENGINEER OF THE BRIDGEWATER CANAL.—INVENTS THE SELF-REGULATING FEEDER.—JAMES WATT.—HIS DESCENT AND PARENTAGE.—ANECDOTES OF HIS BOYHOOD.—HIS EARLY ACQUIREMENTS.—GOES TO LONDON.—RETURNS TO GLASGOW.—IS APPOINTED INSTRUMENT-MAKER TO THE UNIVERSITY.—OPENS A SHOP IN GLASGOW.—HIS FRIENDS AND PATRONS.—ADAM SMITH.—DR. BLACK.—ROBERT SIMSON.—PROFESSOR ROBISON.—WATT'S PERSONAL CHARACTER.—INDUSTRIOUS AND STUDIOUS HABITS.—HIS ATTENTION FIRST DIRECTED TO STEAM.—EXPERIMENTS ON HIGH-PRESSURE STEAM.—REPAIRS AN ATMOSPHERIC MODEL.—EXPERIMENTAL INQUIRY CONSEQUENT ON THIS.—ITS RESULTS.—DISCOVERS THE GREAT DEFECTS OF THE ATMOSPHERIC ENGINE.—DISCOVERY BY EXPERIMENT OF THE EXPANSION WHICH WATER UNDERGOES IN EVAPORATION.—DISCOVERS THE LATENT HEAT OF STEAM.—IS INFORMED BY DR. BLACK OF THE THEORY OF LATENT HEAT.