Contributed By Dan Eckert
Another gram of knowledge to stash away.
Back in the days when every sailing ship had to have a cannon for protection, cannons of the times required round iron cannonballs. The Captain or Master wanted to store the cannonballs such that they could be of instant use when needed, yet not roll around on the gun deck.
The solution was to stack them up in a square-based pyramid next to the cannon. The top level of the stack had one ball, the next level down had four, the next had nine, the next had sixteen, and so on. Four levels would provide a stack of 30 cannonballs.
The only real problem was how to keep the bottom level from sliding out from under the weight of the higher levels. To do this, they devised a small brass plate ("brass monkey") with one rounded indentation for each cannonball in the bottom layer. Brass was used because the cannonballs wouldn't rust to the "brass monkey," but would rust and stick to an iron one.
When the temperature falls, brass contracts in size faster than iron. As it got cold on the gun decks, the indentations in the brass monkey would get smaller than the iron cannonballs they were holding. If the temperature got cold enough, the bottom layer would pop out of the now smaller indentations spilling the entire pyramid over the deck.
Thus, it was, quite literally, "cold enough to freeze the balls off a brass monkey."
A little military trivia that you always thought meant something else.
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