The imaginary question I propose to answer in this address is—how does it come about that a person with such a very ordinary sort of intellect, and certainly with no particular flair for mathematics, should be the author, or nominal author, of such an imposing publication as a volume of nautical tables?

To build up the background to the story briefly let me explain that in my training ship days I received the impression that a ship's position was found by mathematical calculations. True, we knew that sextants and chronometers were necessary instruments in the scheme of things; but they only seemed to supply certain ingredients to the calculations that ultimately produced one of the components, latitude or longitude. It was when I was consigned to a stretch of service on the North Pacific in 1927 that, for something to do, I decided to try and improve my limited understanding of astronomical navigation. In the volume of Raper's Tables which I had always used there was an appendix by the Naval Instructor William Hall which explained what was then called by the Navy ‘The New Navigation’, and gave four-figure cosine-versine tables for the work. It was in reading, and re-reading, and thinking about Hall's marvellously lucid explanation of the St. Hilaire process that the light suddenly burst upon me.