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Chapter 8 In Pursuit of Coat-Hangers > 8.7 The Return of the Bent Coat-Hanger - Pg. 165

IN PURSUIT OF COAT-HANGERS 165 I have very good reasons for using the `bad form' of the trac- ing points I do, and I think I know what I am about. I happen to have one of Captain Prytz's planimeters, which I can quite believe may have been made by a country blacksmith; for my own part though, I prefer having mine made by a mathemat- ical instrument maker, for curiously enough, I find the latter usually works more accurately that the former. Possibly in Denmark things are different. Practical men have no time to waste in calculating the mean square of the radii of all the figures they require the area of. They want an instrument which gives a close approx- imation to the truth, without any calculation whatever. Such is mine. Let those who doubt get one and try for themselves. So perhaps we should now explain why with the aid of the hatchet planimeter you are able to calculate a good approxima- tion to the area of a plane shape. This will take a similar informal geometrical approach, using much that has been developed for