The next advance was the invention of the wheel-and-weight-clock, such as has been in use ever since. The first instrument of this kind may have been made by the ancients; but no clear allusion to its existence has been discovered earlier than 996, when Pope Sylvester II. is known to have had one constructed. It was Christian Huygens, the famous Dutch philosopher, who applied, in 1658, the pendulum to the clock, and thus led directly to those more refined and subtle improvements, which render our present clocks and watches among the least imperfect of all human contrivances. George Graham, the great London clock-maker of Queen Anne's and George the First's time, and one of the most noted improvers of the clock, was born in 1675. After spending the first thirteen years of his life in a village in the North of England, he made his way to London, an intelligent and well-bred Quaker boy; and there he was so fortunate as to be taken as an apprentice by Tompion, then the most celebrated clock-maker in England, whose name is still to be seen upon ancient watches and clocks. Tompion was a most exquisite mechanic, proud of his work and jealous of his name. He is the Tompion who figured in Farquhar's play of "The Inconstant;" and Prior mentions him in his "Essay on Learning," where he says that Tompion on a watch or clock was proof positive of its excellence. A person once brought him a watch to repair, upon which his name had been fraudulently engraved. He took up a hammer and smashed it, and then selecting one of his own watches, gave it to the astonished customer, saying: "Sir, here is a watch of my making." Graham was worthy to be the apprentice of such a master, for he not only showed intelligence, skill, and fidelity, but a happy turn for invention. Tompion became warmly attached to him, treated him as a son, gave him the full benefit of his skill and knowledge, took him into partnership, and finally left him sole possessor of the business. For nearly half a century George Graham, Clock-maker, was one of the best known signs in Fleet Street, and the instruments made in his shop were valued in all the principal countries of Europe. The great clock at Greenwich Observatory, made by him one hundred and fifty years ago, is still in use and could hardly now be surpassed in substantial excellence. The mural arch in the same establishment, used for the testing of quadrants and other marine instruments, was also his work. When the French government sent Maupertuis within the polar circle, to ascertain the exact figure of the earth, it was George Graham, Clock-maker of Fleet Street, who supplied the requisite instruments.