Used with permission of Maiken Naylor, University at Buffalo, Buffalo, NY,
USA,
http://ublib.buffalo.edu/libraries/units/sel/exhibits/stamps
John Napier's (1550-1617) invention of logarithms immensely facilitated mathematical computations before the age of computers. Lengthy multiplications and divisions of large numbers were replaced by the addition or subtraction of their logarithms, which were calculated and conveniently available in tables of great accuracy. The Nicaraguan stamp shows astronomical equipment and the Big Dipper. Astronomical calculations benefitted enormously from the use of accurate logarithmic tables. Napier's "bones," or sliding scales, later became the slide rule, an essential tool for engineers and scientists until replaced by the hand-held calculator of the 1970's. On the Romanian stamps of 1957 publicizing a Congress of Engineers and Technicians, calipers and slide rule represent quintessential tools for measurement and calculation.