Opera mechanica, geometrica, astronomica et miscellanea

HUGENII VITA.

these two excel above the rest in the size of the telescopes they must serve, and, if we are to believe our author, in excellence original: "excellentia"; the larger was destined for a telescope of two hundred and ten feet, the other for a telescope of one hundred and seventy. England now possesses these two. Many others serving telescopes exceeding one hundred feet, as well as smaller ones, still remain among his heirs.

* See page 698. In the year 1656, he wrote a treatise on reasoning in games of chance original: "de ratiociniis in ludo alex"; this was published at the end of the Mathematical Exercises of Schooten. In this treatise, he demonstrated the method of subjecting chance itself to mathematical computation, and he was the first to make public the principles of an art that, after him, was brought to an expectation of perfection that was hardly hoped for.

In the year 1657, he was the first of mortals to measure time most accurately when he applied pendulums to clocks. Before him, astronomers indeed measured time using pendulums, but only for short intervals, since such pendulums required a human who would ensure they continued in motion. He, however, by means of clocks, communicated an almost perpetual motion to the pendulums, for the clocks were driven by weights, which could be raised without changing the action upon the clocks.

He was convinced that such clocks could be used at sea, and that nothing else would be required on a ship to determine longitudes.