I have just learned from James Graham (Books, THES , October 12) that Gutenberg invented printing and thus defined the Renaissance. Did William Gilbert's invention of the magnetic compass provide a similar "defining moment" for Elizabethan maritime exploration? I must now go round local schools explaining why the posters they display with a different version of the history of technology are wrong.
Roger Mason
China University of Geosciences
Wuhan, Hubei, China