s of the shafts, @ 6, have 60 teeth each, the earth. But as, while the earth is rotating on its and the pinions at the lower ends have 30 teeth each; own axis, it is also traveling forward in its orbit around and as the driving wheels, c d, having 90 teeth each, the sun, it therefore has to turn a… … in conse- of the earth’s motion, the sun appears to describe among the it is evident that the wheels, e jf, revolve twice This great circle of the sun’s apparent yearly while the wheels, ¢ d, revolve once. By thus pro- portioning the gears, the exact difference in the speeds called right ascension,…
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![An illustration from Essai de physique, par Mr. Pierre van Musschenbroek ... avec une description de nouvelles sortes de machines pneumatiques, et un recueil d'expériences par Mr. J. v[an] M[usschenbroek] Traduit du hollandois par Mr. Pierre Massuet .. (1751)](https://img.insideoutlibrary.com/img/200/ia-essaidephysiquep02muss-480-77.webp)
