Twentieth century handbook for steam engineers and electricians, with questions and answers; a practical nontechnical treatise .. (1916)
Swingle, Calvin F. (Calvin Franklin), b. 1846 · Chicago, F.J. Drake & company · leaf 559
were reducedto a plain parallelogram instead of the irregular figure whichit is. The planimeter, Figs. 220-221, is an instrument whichwill accurately measure the area of any plane surface, nomatter how irregular the outline or boundary line is, andit is particularly adapted for measuring the areas… … Fig. 220 COFFIN AVERAGER OR PLANIMETER of late years become an almost indispensable adjunct of theindicator. It shows at once the area of the diagram insquare inches and decimal fractions of a square inch, and Diagram Analysis 547 when the area is thus known it is an easy matter to obtainthe…
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