Galileo's Telescope

Galileo heard the news that somebody in Holland had invented a telescope. Instead of waiting for one to be sent from Holland he invented his own. But there was a difference between the one in Holland and the one he invented. The one in Holland had convex lenses at both ends. The one invented by Galileo had convex at one end and concave at the other. Apparently he did not have enough clues to fully duplicate the Dutch invention.

'What one man can invent, another can discover.'

--Sherlock Holmes, The Adventure of the Dancing Men