Before the pendulum, clocks were not accurate enough to compete with a
sundial, and there was little point in trying to set a clock or watch to
other than solar time, but the difference was certainly known.
Tables of the equation were published and sometimes engraved on sundials or
pasted inside the case of a longcase clock. The earliest such table I have
found is by Thomas Tompion, dated 1685 (when, of course, England was on the
Julian calendar). It shows a maximum of "watch too fast" of 14' 46" on Jan
31st, and a maximum of "watch too slow" of 16' 05" on October 23rd.
These compare with a table by Copland dated "1754 New Style" (England
adopted the Gregorian calendar in 1752) which has maxima of 14' 49" on
February 11th and 16' 13" on November 2nd. Notice the 11 day shift and the
slight difference in the values due, I imagine, to precession.
These tables are reproduced in:
A Book of English Clocks, R.W.Symonds, Penguin 1950.
The Country Life Book of Clocks, E. Joy, Hamlyn 1967.
Hope this helps
Chris Lusby Taylor
