Further to Luke Coletti's contribution on the discovery of the Equation of Time and mention of:-
"In Dava Sobel's excellent book, "Longitude", about the struggle of John Harrison to construct a clock for determining longitude, she points out that the equation of time was known before Harrison" In the excellent book by Humphrey Quill (then Senior Warden of the Worshipful Company of Clockmakers) "John Harrison - the man who discovered Longitude" published by John Baker in the sixties - I recall a photograph of a hand-written Equation of Time - possibly in John Harrison's own hand - taken from the inside of a longcase clock he (and his brother?) constructed before their pursuit of the Longitude prize.
