An Experiment Demonstrating Proof of a Vacuum through the Descent of Mercury in a Glass Tube Sealed at the Top

Abstract

When I attended the Imperial Diet.in Regensburg (as we mentioned above in Chapter 27,) among other things, I demonstrated certain experiments of mine to the electors, various princes and legates, and on this occasion I became acquainted with the Right Reverend Capucchine Father, Valerianus Magnus. He performed an experiment he had devised, so he said, for demonstrating a vacuum. The procedure was as follows: (1) He took a glass tube which was longer than 6/4 of a Magdeburg cubit and completely sealed one end. (2) He filled this tube with mercury and inverted it (the opening was tightly blocked by his finger so that nothing could escape) and submerged it, with his finger still in place, in a small container filled with mercury. (3) He withdrew his finger gradually, and behold! the mercury descended little by little in the tube until it reached a certain height, actually about 5/4 of the height of a cubit. Provided only that the finger was not withdrawn suddenly, it remained unmoved at this height and descended no lower in the tube. If the finger was quickly removed, however, then the mercury fluctuated at different levels, now ascending and now descending before it came to rest at the same point.