John Walter Gregory, FRS, FRSE, FGS (27 January 1864 – 2 June 1932) was a British geologist and explorer, known principally for his work on glacial geology and on the geography and geology of Australia and East Africa.
https://github.com/davepinch/pinchy.cc/blob/master/content/topics/people/j/john-walter-gregory/en.wikipedia.org.md
He visited central Kenya in 1893 and again in 1919 and his 1896 book The Great Rift Valley is considered a classic.