(Our pal, Camber, the old son-of-a-gun, found this one in his email box.  It's been circulating on the net.  Is it a myth?)

In the heyday of sailing ships, all war ships and many freighters carried iron cannons. Those cannon fired round iron cannon balls.  It was necessary to keep a good supply near the cannon.  But 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 thirty cannon balls could be stacked in a small area right next to the cannon.

Pyramid of cannon balls next to a Civil War gun.

There was only one problem -- how to prevent the bottom layer from sliding or rolling out from under the others.  The solution was a metal plate called a "Monkey" with sixteen round indentations.  But, if this plate was made of iron, the iron balls would quickly rust to it.  The solution for 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 cannon balls would come right off the monkey.  Thus, it was quite literally, "Cold enough to freeze the balls off a brass monkey!" (and all this time you thought that was a dirty expression, didn't you?)

HMS Victory, the oldest commissioned warship on the planet. It was on the deck of this 100-gun Ship of the Line that Vice-Admiral Horatio Nelson died during the   Battle of Trafalgar.
 
 
 

(OMED: Is this another e-myth? This source thinks it is.  Click here.  But,"monkey," it turns out, actually was a sailing warship term. Click here. It's possible that the original reference may not have been to the stack plate, but to the boy described in that lower link. That would just leave the "brass" item to be dealth with.  We know that cannon balls were made out of both lead and iron.  Were they ever made out of anything else?  No matter what the experts say, the origin of this famous phrase may actually lie in the lore of ancient war at sea, after all.)

© 2002 ????  Photos are a link to their source.  The first one leads to a working model.