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          A Cattle Calculator

    You go to the county fair, spot a healthy heifer and want to buy it; but the seller demands too much, claiming the animal to weigh more than your trained eye estimates. What to do? You donít go around with a folding cattle scale, do you?
    Well, no, but you do carry in your pocket the Chesterman Cattle Gauge. You whip it out, pull out the tape measure, take the cowís length from shoulder to tail and her girth behind the forelegs, feed the data into the built-in calculator, and out comes the beastís estimated weight in country stones. You were right: the seller was trying to pull a fast one. He wasnít counting on his mark having the latest in modern, pocketable computing technologyÖ Chesterman's cattle gauge as a tape measure
Click a photo to enlarge
    Chestermanís Cattle Gauge is a combination tape measure and circular slide rule, dedicated to the estimation of cattle weight from two body measurements. The instructions on the inside of the screw-off lid are clear:
    First, take the length from the foremost upper corner of the shoulder blade bone, in a straight line to the hinder-most point of the rump by the tail, and next the girth close behind the fore-legs. The measures carefully taken will, with the assistance of the circular sliding plate, tell the dead weight of the four quarters either in the London stone of 8 lbs. the country stone of 14 lbs. or the score of 20 lbs.
Chesterman's cattle gauge with lid off
    Example: suppose the length of the beast to be 5 ft. 6 in. and girth 6 ft. 3 in., turn the slide till the figure 8 with the * is over 5 ft. 6 in. on the inner circle, then look at 6 ft. 3 in. on the slide, and over that on the outer circle will be found 90 stones. If the weight be required in stones of 14 lb., turn the slide in the same manner till the figure 14 with the * is over the length, when the weight 51 and a half stones will be found over the girth as before. Or if the score of 20 lbs. be required, turn the slide till the figure 20 with the * is over the length, when the weight will be found 36 score.

    The photo below shows the slide rule set for the first example given in these instructions.

Instructions of Chesterman's cattle gauge
Click a photo to enlarge
    This instrument is made of a heavy brass shell enclosing the spring-loaded 12 ft. tape measure, which is marked in inches and feet. My unit has a steel tape, but Iíve seen a cloth tape version as well. The slide rule, also in brass, has a rotating scale sliding between two fixed ones; these are calibrated directly in Feet and Stones. Chesterman's cattle gauge - calculation example  Chesterman's cattle gauge
    The formula embodied in this calculator is

 Weight  = 3.35 x Length x Girth squared

where the linear measurements are in feet and the weight is in pounds.
    The tool has a logo with the letters JC, and is stamped Chesterman, Sheffield, England. There is no date, but Peter Hopp's book lists a British patent for a cattle gauge that had been granted to a James Chesterman of Sheffield in 1842.

Chesterman's cattle gauge - maker's logo
Exhibit provenance:
    Got it at an auction at the annual meeting of the Oughtred Society.

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