iiJ.j OF NATURAL PHILOSOPHY. 411 of the pendulum at Paris (which was 3 Paris feet and 8f lines), he found it shorter by 1 j line. Afterwards, our friend Dr. Halley, about the year 1677, arriving at the island of St. Helena, found his pendulum clock to go slower there than at Isondon without marking the difference. But he shortened the rod of his clock by more than the \ of an inch, or l£ line ; and to effect this, be cause the length of the screw at the lower end of the rod was riot sufficient, he interposed a wooden ring betwixt the nut and the ball. Then, in the year 1682, M. Varin and M. des Hayes found the length of a simple pendulum vibrating in seconds at the Royal Observatory of Paris to be 3 feet and S