Patent Model for Combination Rule, Protractor, and Calculating Device by Nels Ockerlund

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This combination instrument may be used to measure distances of up to 24 inches, to measure angles, to solve problems relating to ratios, to assist in finding the area of triangles when the lengths of three sides are known, and to add three-digit numbers. It is in the general shape of a four-fold rule, with a wooden core covered on both sides with German silver. A scale of inches, divided to 1/16" and numbered by ones from 1 to 12 twice, runs along the outer edges of the arms. Along the inner edges of both arms are scales of equal parts, with 30 parts to the inch.
A protractor is at the center joint. A hollow in one arm contains two rules. One rule unfolds to reveal a 10" scale and a scale of 30 parts per inch. The other rule has a 4-1/2" scale and a scale of 30 parts per inch. These rules are supposed to attach to slides that move in a groove in one of the arms, allowing the solution of problems of proportion. To add numbers, one removes the longer rule from the groove, and places it alongside the scale on the arm.
A third rule slides and pivots in a hollow in the other arm. Using this rule and the two arms of the instrument as sides, one can represent a triangle. The grooved arm serves as the base and a rule sliding in the groove measures the height of the triangle, from which one can calculate its area.
The object is marked: Nels Ockerlund New York. Nels Ockerlund (1837–1903) was born in Sweden. He immigrated to the United States in 1865 and settled in New York City. In addition to the improved rule and calculator represented by this patent model, he took out a second patent in 1870 for an improvement in adding-machines. He became a citizen in 1879 and is listed in the 1900 census as still living in New York City.
References: Nels Ockerlund, "Improvement in Rule and Calculator" (U.S. Patent 102,034 issued April 19, 1870), and "Improvement in Adding Machine" (U.S. Patent 105,717 issued July 26, 1870).
Currently not on view
date made
Ockerlund, Nels
place made
United States: New York, New York
Physical Description
wood (overall material)
german silver (overall material)
overall: 3.2 cm x 17.7 cm x 4.4 cm; 1 1/4 in x 6 31/32 in x 1 23/32 in
ID Number
catalog number
accession number
Rule, Measuring
Rule, Calculating
Patent Models
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Medicine and Science: Mathematics
Science & Mathematics
Scale Rules
Data Source
National Museum of American History


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