Gaussian Logarithms and Navigation

Abstract

The following comments on Captain C. H. Cotter's note (this Journal, Vol. 24, page 569) on the use of addition and subtraction logarithms in navigation may be of interest. Captain C. Carić was not the first to introduce gaussian logarithms to navigators, since their use was advocated, at least to Portuguese navigators, in 1920 by Admiral Gago Coutinho (see my review of Precision Astrolabe by Francis M. Rogers, 25, 135), and actually used by him on his pioneering transatlantic flight in 1922. They are included in several collections of nautical tables, including Tábuas Náuticas by Fontoura and Coutinho, as well as those of Friocourt and Hoüel; but I have been unable to obtain the dates of their first inclusion. However, it is most unlikely that either Coutinho or Carić, who incidentally used quite different basic formulae, were the first to advocate the use of addition and subtraction logarithms, or possibly to publish methods and tables. They were in use to a small extent in astronomical calculations, and to a somewhat larger extent in surveying. Dr. L. J. Comrie, the computer and table-maker, who was Superintendent of H.M. Nautical Almanac Office (N.A.O.) from 1930 to 1936, was an enthusiastic advocate and designed many computational forms incorporating their use.