The characteristics of experiments

The world of an early modern naturalist was filled with stories, many of which were full of wonders and impossible to explain with the existing body of knowledge. Think about the functioning of the compass or the attraction of magnets. For us, they are phenomena that can be easily explained and predicted. But for the early moderns, the attraction between a magnet and a piece of iron was as wondrous as the theory according to which a wound was easier cured by applying the medicine to the weapon that provoked it, theory which people like Giambattista della Porta, Francis Bacon, or Jan Baptista von Helmont tried to explain.

Many of the early modern natural philosophers attempted to establish whether such fantastical stories were true or not, and they also tried to discover the causes of those phenomena which were proven to be true. But how can they check the veracity of a story? And how can one have access to the causes that produce visible phenomena? As we have already seen, Bacon made it clear that the simple observation of a phenomenon does not bring knowledge about its causes. And this is because, on the one hand, senses are deceiving and not enough to gain access to the structure of the things.

And on the other, if we contrive experience, it is easier to disclose those features which are not easily remarked through mere observation. The story Bacon is willing to verify in the experiment you just read is saying that in a closed cave, there were found vessels with a very thick water, almost to the consistency of ice, a story reported by Pseudo-Aristotle in his work On Marvellous Things Heard. The report mentions that there was no source of water in the cave, and thus Bacon assumes that the story is true, then it should be due to two processes– the transformation of air into water, and the condensation and induration of that water so it becomes denser and more consistent, closer to ice.

It was common knowledge at the time that condensation and its opposite, rarefaction, were caused by cold and respectively heat. The basis of this theory was the transformation of water into vapour when boiled and its transformation back into water when cooled. Because Bacon could not replicate the phenomenon given that he did not dispose of a cave, he proposes to imitate tit by producing conditions similar to a cave. He assumes that cold can be produced by substances like snow, nitre or quicksilver, and the phenomenon replicated by inflating a bladder with air and hanging it in such substances.

Bacon’s conclusion is this: If the experimenter finds the bladder fallen or shrink, then it means indeed that cold causes air to transform into water. Moreover, water is heavier than air, so the bladder would fall, but it is also denser, so a certain volume of air would need less space when transform into water and thus the bladder would shrink. There are three characteristics I would like to emphasise regarding this experiment. First, as many other early modern natural philosophers, Bacon is undermining the authority of the ancients by claiming that the simple detail that the story is written in Aristotle or any other author does not make it true by default.

In order to establish its veracity, one has to check whether the processes described in it are true or not. Second, this experiment shows us how instruments and laboratories started to be used. Bacon lacked access to a cave and thus, he reproduced the phenomenon by using an instrument, a bladder filled with air and handy substances that created in an artificial setting the natural conditions of a cave. Third and finally, this experiment leads us to what is generally called the mathematisation of nature. The experiment is one in a series studying condensation and the transformation of air into water in which measurement plays a significant role.

The next step to be taken is to measure the volume of the two bodies, which will bring significant information about their densities and their relation between them mathematising in this way the visible process we observe.