Did you know that the first air conditioned building in London was Westminster Abbey…back in the year 1620? No? Well, it was a bit of a one-off, but even so it’s such a fun story!
James I was King of England then. He was getting on in years and suffered from several health complaints, among them an extreme sensitivity to sunlight. He was also deeply paranoid after surviving several assassination attempts and always wore thickly padded doublets, even in summer. So I don’t think he very much looked forward to the advent of warmer weather, even though England’s summers tend to the more temperate. Evidently he had a discussion about this with his court magician, one Cornelis Drebbel, who offered to make a room as cold as winter in the midst of summer for his majesty. James jumped at the offer, and chose the room he wanted cooled–namely, the Great Hall of Westminster Abbey!
Drebbel was an interesting fellow, much closer to a Leonardo da Vinci than to a magician, though he often found it easier to get people to listen to him about his scientific studies if he pretended they were magic. He was a pioneer in the study of submarines (for all intents and purposes discovering oxygen in the process, 150 years before Joseph Priestley) and took King James for a ride in one in the Thames, making James the first British monarch to travel underwater.
Drebbel did not leave a detailed account of how he cooled Westmister on that July day in 1620, but cool it he did–in fact, James had to leave after becoming chilled. But according to accounts left by some of the courtiers who were there, it’s possible to reconstruct what Drebbel did: he and his assistants brought several long, low metal troughs and set them around the edges of a narrower part of the Hall, filling them with salt and ice cut from the Thames in winter and stored in ice houses. They also added nitre, today called saltpetre or potassium nitrate, to the troughs, which in combination with the salt and icy water created a compound that was actually below the freezing point of water. Drebbel had doubtless observed that cold air sinks and displaces warm air upward, so by carefully selecting his location in that narrow part of the hall, was probably able to cool the lower part of the air (and force the warm air up toward the lofty ceiling) to a relatively chilly sixty five degrees or so…which would certainly feel like winter if you’d just stepped inside from 80 degree heat. Smart guy!