Peter Barlow (mathematician)

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 integer numbers from 1 to 10,000. These tables were regularly reprinted until 1965, when computers rendered them obsolete. He contributed to Rees's Cyclopædia articles on Algebra, Analysis, Geometry and Strength of Materials. Barlow also contributed largely to the Encyclopædia Metropolitana''. ==Work in physics and engineering==

In collaboration (1827–1832) with optician George Dollond, Barlow built an achromatic lens that utilized liquid carbon disulfide. (Achromatic lenses were important optical elements of improved telescopes.) In 1833, Barlow built an achromatic doublet lens of joined flint glass and crown glass. He is credited with ''Barlow's wheel (an early homopolar electric motor) and with Barlow's law'' (an incorrect formula of electrical conductance). Barlow investigated a suggestion made by André-Marie Ampère in 1820 that an electromagnetic telegraph could be made by deflecting a compass needle with an electric current. In 1824 Barlow proclaimed the idea impractical after he found that the effect on the compass seriously diminished "with only 200 feet of wire". Barlow, and other eminent scientists of the time who agreed with him, are criticised for retarding the development of the telegraph. A decade passed between Ampère's paper being read at the Paris Academy of Sciences and William Ritchie building the first demonstration electromagnetic telegraph. In Barlow's defence, Ampère's design did not enclose the compass in a multiplying coil, as Ritchie's demonstrator did, so the effect would have been very weak at a distance. Steam locomotion received much attention at Barlow's hands and he sat on the railway commissions of 1836, 1839, 1842 and 1845. He also conducted several investigations for the newly formed Railway Inspectorate in the early 1840s. Barlow made several contributions to the theory of strength of materials, including Essay on the strength and stress of timber (1817) which contains experimental data collected at Woolwich. The sixth edition (1867) of this work was prepared by Barlow's two sons after his death and contains a biography of their father. Barlow also applied his knowledge of materials to the design of bridges. Following his death in 1862 at his home in Charlton, he was buried in Charlton Cemetery. ==See also==