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Page:Popular Science Monthly Volume 49.djvu/751

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THE METRIC SYSTEM.

division of single units, even among users of our own clumsy system of weights and measures.

In weight, for instance, we in the United States have long ago decided that a hundredweight shall be a hundred pounds, as its name implies, and not a hundred and twelve as in England, and our ton is almost universally two thousand pounds, although we still retain the traditional ton of twenty-two hundred and forty pounds in certain transactions; and as if to emphasize the utter absurdity of the thing, in some parts of New England a "long" or "gross" ton of coal weighs twenty-two hundred pounds. In many extensive calculations the avoirdupois pound is adopted as the only unit of weight, and fractional parts are expressed in tenths, hundredths, etc.; and this is found to reduce the labor of such calculations enormously. In length measure the tendency toward decimalization is still more marked. In land surveying and in engineering operations it is now the all but universal practice to use the foot as the unit and multiply and divide decimally. Even in the traditional "surveyor's chain," with its one hundred links, each being 7·92 inches in length, there was a serious attempt to secure some of the advantages of decimalization, but it is quite superseded now by the one-hundred-foot tape, with its divisions of ten feet each, and each foot divided into tenths, etc. In reference to the chain, a quotation from the book from which the tables given above are extracted, will not be without interest. After explaining that by a rather laborious process the following measures of surface may be derived:

144 square inches are 1 square foot,
9 " feet " 1 " yard,
30-1/4 " yards " 1 " pole,
40 " poles " 1 rood,
4 roods are 1 acre,

the author remarks: "Thus the acre contains forty-eight hundred and forty square yards, which is ten times a square of twenty-two yards in length and breadth. This twenty-two yards is the length which land-surveyors' chains are made to have, and the chain is divided into one hundred links, each 0·22 of a yard or 7·92 inches. An acre is, then, ten square chains. It may also be noticed that a square whose side is sixty-nine yards and four sevenths is nearly an acre, not exceeding it by a fifth of a square foot." This is a fair example of the beautiful simplicity of a system which all English-speaking people are assumed to understand and which many of them are reluctant to give up.

Again, in accurate machine-shop practice the use of decimal divisions is becoming almost universal. The unit is generally the inch, and it is subdivided into tenths, hundredths, thousandths, etc. "True to one hundredth, or one thousandth, or one ten-thou-