Whereas several, who have been curius in measuring of Time, have taken Notice, that the Vibrations of a Pendulum are slower in Summer than in Winter; and have very justly supposed this Alteration has proceeded from a Change of Length in the Pendulum itself, by the Influences of Heat and Cold upon it, in the different Seasons of the Year; with a View therefore of correctiong, in some degree, this Defect of the Pendulum, I made several Trials, about the Year 1715.

I should have here described some Clocks and Time-keeppers of great use, nay absolute necessity in these and many other Astronomical observations, but that I reserve them for some attempts that are hereafter to follow, about the various wayes I have tryed, not without good success of improving Clocks and Watches, and adapting them for varius uses, as for accurating Astronomy, compleating the Tables of the fixt Stars to Seconds, discovery of Longitude, regulating Navigation and Geography, detecting the proprieties and effctes of motions for promoting secret a

To time the descent of bodies along inclined planes Galileo uses the method of water weighing: