October 13: Peter Barlow

Peter Barlow

October 13, 1776 – March 1, 1862

Peter Barlow was an English mathematician and physicist.

In 1801, Barlow was appointed assistant mathematics master at the Royal Military Academy, Woolwich, and retained this post until 1847. He contributed articles on mathematics to The Ladies' Diary as well as publishing books such as: An Elementary Investigation of the Theory of Numbers (1811); A New Mathematical and Philosophical Dictionary (1814); and New Mathematical Tables (1814).

The latter became known as Barlow's Tables and gives squares, cubes, square roots, cube roots, and reciprocals of all numbers from 1 to 10,000. These tables were regularly reprinted until 1965, when computers rendered them obsolete. Barlow also contributed largely to the Encyclopaedia Metropolitana.

Barlow made an important contribution to astronomy by inventing the Barlow lens, an achromatic telescope lens in which two glass layers enclosed a colourless liquid (later replaced by a different kind of glass).

In 1823 he was made a fellow of the Royal Society and two years later received its Copley Medal for his work on correcting the deviation in ship compasses caused by the presence of iron in the hull. Some of his magnetic research was done in collaboration with Samuel Hunter Christie. Barlow's Wheel is an early electric motor he invented, while Barlow's law is an (incorrect) law describing electrical conductance.