Twentieth century hand-book for steam engineers and electricians with questions and answers; a practical non-technical treatise .. (1913)
Swingle, Calvin Franklin, 1846- [from old catalog] · 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…
