Patent Revolving Interest Table

In the early 19th century, Joseph Jelleff of Butternuts, New York, and Gilbert D. Lowe of Hampfield, Pennsylvania, took out patents for mathematical tables that eased calculations of interest. This instrument is a version of their inventions, probably made after their patents had expired.

The instrument consists of two overlapping concentric discs held together with a metal pivot at the center and attached to a cardboard cover. It is designed for finding the interest on a principal of up to $5,000 at an interest rate of six percent, for times ranging from one to thirty days and then from two months to twelve months. Amounts of principal ranging from $1 to $5,000 are listed on the top disc, going out from the center. Next to this list is a notch in the disc that reveals the disc below. Printed on the lower disc, also going out from the center, are amounts of interest for a given length of time. Lengths of time are marked around the edge of the top disc. Rotating an index on the lower disc so that it points to the appropriate time turns that disc so that the correct amounts of interest are shown in the notch.

A mark on the front of the rotating disc reads: PATENT Revolving Interest TABLE. Another mark there reads: Published by C.M.Riley Cincinnati, Ohio. A mark on the inside of the cover reads: Cost [/] $1.00. Another mark there reads: John F. Kern (/) Germantown (/) September 30th 1839. John F. Kern was a shopkeeper in Germantown, Ohio.

Compare 1980.0588.02.

References:

L.C. Karpinski, Bibliography of Mathematical Works Printed in America through 1850, New York: Arno Press, 1980, pp. 206-207. This describes Jelleff’s Patent Revolving Interest Table

Joseph Jelleff, “Circular Interest Table,” U. S. Patent (no number), September 8, 1812. Apparently no copy of the patent survives.

Gilbert D. Lowe, “Circular or Revolving Interest Table,” August 12, 1815. Apparently no copy of the patent survives.

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