Walker (c. 1820-1893) graduated from Trinity College in 1844, becoming a Fellow in 1845. He provided the winning entry for the Adams Prize - the Cambridge award for mathematics - in 1865, offering a “systematic account of the phenomena and laws of terrestrial and cosmical magnetism so far as they have been hitherto ascertained by experiment”. This published version deals with declination, inclination and intensity, and draws on observations from the sixteenth to the nineteenth centuries. Walker incorporates findings from several observing stations, including those of Arctic and Antarctic expeditions, and also acknowledges the assistance of Sir Edward Sabine, one of the major promoters of the investigation of terrestrial magnetism during the nineteenth century.