vent the back- gases as may be desired. ward rotation of the nut under the influence of jars and avoids all those errors incidental to the working of mercury air pumps of which the cocks are obliged to be worked by hand. Lastly, itcan maintain the vacuum indefinitely. size of a laboratory… … sue is, impermeable to gases. The utility of the device is This machine is composed of two reservoirs of cast iron, principally found in testing silk and other fabrics used for A A, which counterpoise each other, and are supported by the pulley, B. They communicate with two glass balloons, C, by…
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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-essaidephysiquep01muss-431-72.webp)