Joseph Priestley had a lot of unusual ideas. As a clergyman and philosopher in the late 18th century, his theological notions (he wrote that the Anglican Church, and its teachings, were a corruption of Christianity) got him rioted out of Birmingham. As a scientist, he was interested in what exactly air was made of—but even as he discovered gases like nitrous oxide and, most famously, oxygen, he was also drawn to a theory of fading scientific relevance that attributed flammability to a (nonexistent) special element called phlogiston.
But among his unusual ideas, Priestley lit on one discovery that endured in both popularity and profitability—he figured out how to make carbonated water.
At one point in his career, Priestley lived near enough to a brewery that he had started investigating the airs that its fermenting beer gave off. And he noticed that the water, left above the brewer's mash, would take on a flavor not unlike much-valued, naturally occurring mineral springs. This water was absorbing the carbon dioxide—what Priestley called "fixed air."
Soon, he had come up with a more efficient method of mixing air with water. The idea was simple enough, he wrote in 1772:
“If water be only in contact with fixed air, it will begin to imbibe it, but the mixture is greatly accelerated by agitation, which is continually bringing fresh particles of air and water into contact. All that is necessary, therefore, to make this process expeditious and effectual, is first to procure a sufficient quantity of this fixed air, and then to contrive a method by which the air and water may be strongly agitated in the same vessel, without any danger of admitting the common air to them."
Here's how Priestley did it. He filled a bottle "with a pretty narrow neck" with water, put a piece of paper on it, turned it upside-down and put it in partially filled bowl of water. He removed the piece of paper from the invented bottle and snuck in a piece of flexible piping. That piping led to a bladder (an actual animal bladder), which on the other end could be connected, via a cork with a hole in it, to a second bottle filled with chalk and a little bit of water.