Interesting tid bit of info...
In the heyday of sailing ships, all war ships and many freighters carried iron cannons. Those cannons fired round iron cannon balls. It
was necessary to keep a good supply near the cannon.
However, how to prevent them from rolling about the deck
The best storage
method devised was a square-based pyramid
with one ball on top, resting on four resting on nine,
which rested on sixteen. Thus, a supply of 30 cannon
balls could be stacked in a small area right next to the
cannon. There was only one problem...how to prevent the
bottom layer from sliding or rolling from under the others.
The solution was a metal plate called a 'Monkey' with 16
However, if this plate were
made of iron, the iron balls would quickly rust to it. The
solution to the rusting problem was to make 'Brass
Monkeys.' Few landlubbers realize that brass contracts much
more and much faster than iron when chilled.
Consequently, when the
temperature dropped too far, the brass indentations would
shrink so much that the iron cannonballs would come right
off the monkey. Thus, it was quite literally, 'Cold enough
to freeze the balls off a brass monkey ..'