History of Science Museum: Collection Database Search

Narratives

Inventory no. 34022 - Former Display Label

English CALCULATING RODS
17th century

Twelve, boxwood rods, 304 x 5 x 5 mm, in tooled, leather case. Each side of the rods is divided into 36 sections, and in the sections are punched numbers. The numbers available for calculation range from 1/2q [= 1/8] to 90,000,000,000. Powers of ten are represented by a dot or cross over a digit. Thus {2 dot above}40 {congruent symbol} 2,400, or 240 x 10{1 superscript}; 24{O dot above} {congruent symbol} 240,000, or 240 x 10{3 superscript}; {2 x above}00 {congruent symbol} 2,000,000, or 200 x 10{4 superscript}; 32{0 x above} {congruent symbol} 320,000,000, or 320 x 10{6 superscript}.

These rods represent a novel, and powerful method for multiplying large numbers, as the rods are arranged to give one of the numbers at the left-hand end of the rods, and the multiplier is then selected from the divisions along a rod. The result of the multiplication is then the sum of the various columns. An example will make this clear.

To multiply 2, 383 by 412. First, the rod with the side showing 1-10-100-1,000-9,000 is taken as the bottom rod, which will represent the number 2,383. Then those rods are selected to make up the other number: 400, 10, 2. The rods are arranged one above the other, when 1, on the bottom rod, is below 412 as summed from the ends of the other rods. The next step is to add together the numbers above {2 dot above}00 [ie. 2,000] 300, 80, 3 as found on the bottom rod. Thus: 4,000 + 20,000 + 800,000; 600 + 3,000, + 120,000; 160 + 800 + 32,000; 6 + 30 + 1,200. Total 981, 796.

[79-21]
Purchase

Other narratives:

Related Objects: