Antiques of Science & Technology

W26-06: Palmer's Computing Scale, Early Version, Issue One A Fine precision circular logarithmic scale 26 3/4 inches in circumference. The divisions are printed with very fine spacing giving the user a minimum reading precision of 3 significant figures. There are 32 gauge points ranging from the area of a circle to B.G. Beer Gallons listed in the first column of the instructions for the computing scale printed on the back of the unit. The instructions are very complete, and easy to understand. The construction of the scale is of heavy cardboard, 11 1/8 inches sq. by 3/16 inches thick. On the face of the scale is the Aaron Palmer registration note, 1843, Clerk's Office of the District Court of Massachusetts; printed so fine one needs a magnifying glass to read it! A informative description of the differences between the various issues of Palmer's Computing Scales is given by Bobby Feazel in the March 1994 edition of the Journal of the Oughtred Society. The article estimates that Issue One of this early slide rule spanned only 6-8 weeks and is therefore very limited in number. This particular unit appears to be an early version of Issue One. Compared to the description in the article and another Issue One weÕve seen, this scale lacks the reference to the engraver, George G. Smith, and has only 16 gauge points versus 19 marked on the face. These omissions as well typographical errors were corrected in later versions. This unit also has other differences: the background color is grayish green versus pale yellow and the overall size of the card is a good half inch larger in both directions. Artistic patterns decorate the corners and glided red tape covers the edges. Some scuff marks and edge wear are noted especially at one corner where the card is exposed and a nail hole at another. Neither of these interfere with the usability of the computing scale. The overall condition is good; a fine and rare example of early American slide rules.
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