Palmer's Computing Scale [ Full Size ]

Massachusetts: Aaron Palmer, 1845. Boards. Good. A circular slide rule. 10 15/16 x 11 inches x 3/8 inch thick constructed of two layers of book board. The upper board with a cutout volvelle in a circular form attached to the rear book board with a metal rivet. Upper board with affixed lithograph to both inner volvelle and outer remainder, showing scales, decorative elements, and imprint information. 1/4 inch gilded leather trim affixed to the edges, and holding the pair of boards together (also likely glued in the area without the volvelle). The rear board also covered with a lithographed sheet, this time a set of instructions and covering most of the leather edge wrapper. Front and rear lithographs lightly lacquered. Scuffed and with uniform minor wear. Leather trim is worn with some loss. The recessed metal 'button' insert usually present in the volvelle for turning is lacking, leaving a 5/16 inch blank cutout which serves the same purpose. The volvelle is warped away from the plane of the base but turns freely. Some evidence of dampstaining to the disc in one portion raising the grain a bit underneath the lithographed overlay. There is a small nail (?) hole where it likely was hung on the wall. The usual darkening to the varnish on the rear instructions. Instructions and scales quite readable and in nice condition given the construction standards of these objects. Engraved by George G. Smith, 186 Washington St. Boston in center of volvelle. Boards. Palmer's Computing Scale (so noted in the center of the volvelle) is one of the most desirable objects for those who collect early American Slide Rules and calculating devices. It is important because it is, as far as we are aware, the First American circular slide rule.

Designed by Mr. Aaron Palmer and Mr. George G Smith in early 1841, a prototype was shown in early 1842, and later in Boston in the fall of 1843. It was first released commercially in 1843, and underwent a continual, if minor, set of changes during the next few years. We have yet to find two examples of this device that are exactly the same, and suspect that only a few were made at one time allowing for dynamic changes as needed. Fuller later bought the rights and added a second wheel (the Time Telegraph) to the rear and publishing the instructions separately, starting in 1845.

This is a later example (still within a few years of original publication but before Fuller bought the rights in 1845). The rear board has four columns of text and many examples of the application of the slide rule rather than a list of guage points as in earlier examples. It also notes in the lower left 'Stereotyped by T. S. Sprague, Hartford, CT' and the printer's name (Ela) is no longer present as it is in earlier examples.

For more information on these fascinating objects, see Origins of Cyberspace #353, Feazel (Journal of the Oughtred Society Vol 3, No 1 and Vol 4, No 1), and Barnes, Slide Rule Gazette Issue 6 Aug 2005.