When a person once asked him to repair a watch upon which his name was fraudulently engraved, Tampion smashed it with a hammer, and handed the astonished customer one of his own master-pieces, saying, "Sir, here is a watch of my making." Graham invented the "compensating mercury pendulum," the "dead escapement," and the "orrery," none of which have been much improved since.

The clock which he made for Greenwich Observatory has been running one hundred and fifty years, yet it needs regulating but once in fifteen months.

Tampion and Graham lie in Westminster Abbey, because of the accuracy of their work.
To insure safety, a navigator must know how far he is from the equator, north or south, and how far east or west of some known point, as Greenwich, Paris, or Washington.

He could be sure of this knowledge when the sun is shining, if he could have an absolutely accurate timekeeper; but such a thing has not yet been made.

In the sixteenth century Spain offered a prize of a thousand crowns for the discovery of an approximately correct method of determining longitude.