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.

You tell me you would like to know the device by which I was able to assure myself that the vertically falling  body leaving from the rest passed 100 braccia of height in five seconds. Here two things are sought: the first is the time of descent through 100 braccia, and the second is to find what part that time is of 24 hours in the [del primo mobile].