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Surveyor's Vernier Compass
"Thos Whitney maker Philadelphia No 437"
length 14 inches; needle 5.25 inches
In the Aurora General Advertiser for Feb. 23, 1808, Thomas Whitney boasted that he made surveyor's compasses "of the most accurate construction, and with several late improvements, which have been approved of, in preference to any other, by several eminent surveyors, and others." What these improvements were, however, he did not say. In Whitely's Philadelphia Annual Advertiser for 1820, Whitney announced that during the past 13 years or so he had made about 500 compasses, "the good qualities of which are well known to many Surveyors, in at least sixteen of the States and Territories of the Union." Another Whitney document, this one dated March 1, 1814 and headed "Variation of the Compass," provides information about the extent of the variation in several states as observed by different surveyors, and the change of variation with time. It also describes five ways to determine a meridian line, so that the local variation can be found.
This compass has a variation arc on the north arm that extends 25 degrees either way; the vernier is moved by rack and pinion, and reads to 5 minutes. There is a level vial on the south arm. Under the socket on the bottom of the compass is the date "1818."
The cover of the box is marked in ink "R. R. MORRIS NEW YORK, May 27th 1817 red'd from Philadelphia." There are two printed cards inside the box. One, signed by Whitney and dated March 1, 1817, is headed "Care in the Use of the Compass." The other is a trade card that indicates that while Whitney specialized in compasses, he made many other instruments as well; the date of the card can be inferred from the statement that Whitney "has made near 400