Page:History of the Royal Society.djvu/339

 the Paper, might certainly conclude, what Winds had blown in his absence, for twelve hours space: After a like manner he contriv'd a Thermometer to be its own Register: And because the usual Thermometers were not found to give a true measure of the extension of the Air, by reason that the accidental gravity of the liquor, as it lay higher or lower in the Glass, weigh unequally on the Air, and gave it a farther contraction or extension, over and above that which was produc'd by heat and cold; therefore he invented a Circular Thermometer, in which the liquor occasions no fallacy, but remains always in one height moving the whole Instrument, like a Wheel on its Axis.

He has contriv'd an Instrument to measure the quantities of Rain that falls: This as soon as it is full, will pour out itself, and at the year's end discover how much Rain has fallen on such a space of Land, or other hard superficies, in order to the Theory of Vapours, Rivers, Seas, &c.

He has devis'd many subtil ways for the easier finding the gravity of the Atmosphere, the degrees of drought and moisture, and many of its other accidents. Amongst these Instruments there are Balances which are useful to other purposes, that shew the weight of the Air by their spontaneous inclination.

Amongst the new Discoveries of the Pendulum, these are to be attributed to him, that the Pendulum in its motion from rest to rest; that is, in one descent and ascent, moves unequally in equal times, according to a line of sines: That it would continue to move either in Circular, or Eliptical Motions; and such Vibrations would have the same Periods with those that are reciprocal; and that by a complication Rh