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I think it well to embrace this opportunity, the best I have had, and, perhaps, the last I ever shall have, of making some return, (as far as acknowledgement is a return,) for an obligation, of a nature never to be repaid, by acknowledging publicly, that, to the best and most affectionate of brothers, I owe the invention of those Charts.
At a very early period of my life, my brother, who, in a most examplary manner, maintained and educated the family his father left, made me keep a register of a thermometer, expressing the variations by lines on a divided scale. He taught me to know, that, whatever can be expressed in numbers, may be represented by lines. The Chart of the thermometer was on the same principle with those given here; the application only is different. The brother to whom I owe this, now fills the Natural Philosophy Chair in the University of Edinburgh. [end of page #xvi]
CONTENTS.
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Page
BOOK I.