Museo Galileo
Virtual Museum
Napier's bones
Napier's bones

Set of rods invented in 1617 by the famous English mathematician John Napier (1550-1617) for performing multiplication by mechanical means. Each rod carries a table of the multiple of a given number; the tens are separated from the units by slanted bars. To multiply 267 by 8, for example, the user brings together the 2, 6, and 7 rods; the result is obtained by summing the numbers recorded in the eighth rows of the three rods.