The Sixth Experiment to Obtain the Best Possible Vacuum

Abstract

In the foregoing experiment, a bubble was always produced because of the separation of the water, which was undoubtedly caused by the vigorous rushing together or collision of the water when the tube was shaken (that is, when the keys of the stop-cocks were closed.) This bubble rose into the empty space in the upper part of the tube and gave those who did not want to admit there was a vacuum, a reason for suspicion. (For even though Doctor Deusing in his treatise De Vacuo together with others, does not believe that air has an elastic quality or a particular ability to expand itself unless there is an external force to drive it into a confined place, and that therefore a small air bubble of this kind cannot fill the tube because there is no external force to cause it to expand and thus fill the tube, they raise an objection, nevertheless, to this experiment by saying that a very small particle of air can so extend itself in an evacuated glass or tube as to fill it completely. Therefore, they would only concede that the tube was empty when they saw (1) all the water leave the tube, (2) absolutely no air was able to enter through any passage to replace the water that left, (3) no bubble, even though it be very small, develop in the water itself.) For this reason, I designed another piece of apparatus with two tubes. One of these (the narrower and longer) was always protected from the penetration of air or the formation of bubbles, and in consequence preserved the best possible vacuum.