Page:History of the Royal Society.djvu/340

 of several Pendulums depending one upon another, there might be represented motions like the Planetary Helical Motions, or more intricate: And yet that these Pendulums would discover without confusion (as the Planets do) three or four several Motions, acting upon one Body with differing Periods; and that there may be produc'd a Natural standard for Measure from the Pendulum for vulgar use,

He has invented many ways to make Astronomical Observations more accurate and easy: He has fitted and hung Quadrants, Sextants, and Radii, more commodiously than formerly: He has made two Telescopes, to open with a joynt like a Sector, by which Observers may infallibly take a distance to half minutes, and find no difference in the same Observation reiterated several times; nor can any warping or luxation of the Instrument hinder the truth of it.

He has added many sorts of Retes, Screws, and other devises to Telescopes, for taking small distances and apparent Diameters to Seconds. He has made apertures to take in more or less light, as the Observer pleases, by opening and shutting like the Pupil of the Eye, the better to fit Glasses to Crepusculine Observations: He has added much to the Theory of Dioptrics; much to the Manufacture it self of grinding good Glasses. He has attempted, and not without success, the making of Glasses of other forms than Spherical: He has exactly measured and delineated the Spheres of the Humours in the Eye, whose proportions one to another were only guess'd at before. This accurate discussion produc'd the Reason, why we see things erected, and that Reflection conduces as much to Vision as Refraction.

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