An Ocean of Air Read Online Free PDF

tube; the presence or absence of air in the globe outside should be irrelevant. But if Torricelli and Boyle were right, removing air from the globe would take away the force holding the mercury up and it would fall.
    The assistant manning the pump grasped the handle and began firmly ratcheting it downward. One cylinder's worth of air was drawn out of the great glass globe. And ... the quicksilver unmistakably fell. Turn the valve, replace the plunger, try again. Another cylinder's worth of air disappeared from the globe, and the quicksilver dropped still farther down the glass tube that protruded from the top of the pump. Soon, it had disappeared below the neck of the globe and Boyle could no longer mark its level on the paper he had attached for the purpose. Hampered by his poor eyesight, he had to peer through the walls of the glass globe to make out the shiny surface of the quicksilver as, with each crank on the pump's handle, it successively lurched its way down the inside of its tube toward the box waiting below.
    This surely was the proof Boyle had been looking for, but to be extra careful he decided to try reversing the procedure. He turned the valve and allowed air to begin flooding back into the globe. Immediately the quicksilver raced back up the tube. The more air Boyle allowed inside the globe to squeeze down on the quicksilver, the higher up its tube it climbed. The more he removed air from the globe to take the pressure off, the farther the quicksilver fell. The pressure of air had to be keeping the quicksilver aloft. What could be clearer?
    And yet the argument wasn't quite over. Boyle was now being baited by one of his
bêtes noires,
a Jesuit named Linus who was doggedly convinced that a vacuum could not exist. Instead, he declared, the answer lay in a bizarre invention of his that he called a "funiculus." This was some
kind of strange, invisible thread that hung in the apparently empty space above the mercury, holding it up like a puppet on a string.
    The mild-mannered Boyle was polite as ever in his response to this absurd idea. But even he couldn't resist saying that it was "partly precarious, partly unintelligible, and partly insufficient, and besides..."—and this was the final blow—"needless."
    For the final irrevocable proof that air really does push, and in all directions, too, was already there in the results of another of Boyle's experiments with his air pump—number 31. To do this experiment, Boyle had dispensed with the glass globe altogether. All he needed was the air pump itself.
    The idea was dazzlingly simple. First, open the valve at the top of the cylinder and push the plunger all the way to the top so it fills every scrap of the cylinder's bore. Then close the valve at the top, so that no more air can rush in. Finally, attach weights to the bottom of the plunger to try to pull it back down. Ten pounds, twenty pounds, fifty ... sixty ... seventy pounds. Still the plunger wouldn't budge. Finally, with one hundred pounds dragging it downward, the plunger began to fall.
    By that time Boyle had made his point. There was nothing at all inside the cylinder above the plunger, no vacuum or "funiculus" to hold it up from the inside. The force that kept the plunger in place when such a huge weight was pulling it downward had to have come from the outside. It could only be the apparently insubstantial and inconsequential stuff that surrounds us and squeezes down on us every day of our lives: our all-embracing ocean of air.
    ***
    Boyle published his results in 1660. By then, the Oxford group of intellectuals had largely scattered. Many of them had backed Cromwell and were now fearful of the consequences of a Royalist revival. Boyle himself had remained steadily neutral, but even he left Oxford for a while to wait out the new political uncertainties at the country house of a friend. While there he prepared his book, to be called
New Experiments Physico-Mechanical Touching the Spring of Air.
    Though