Posted by Peter on September 01, 2004
Found on your site the common story about this expression - the one about the stacks of cannonballs on the ship's deck - and its debunking. Here is what my uncle, a Lieutenant Commander in the RAN has to say about it:
On sailing ships, the binnacle compass rested in a brass pedestal by the helm. The compass needle would be pulled out of its true bearing by iron fittings, guns, nails, etc. in the ship. To stabilise the magnetic field around the compass needle, two massive iron balls sat either side of the compass, supported on curved brass arms projecting from the sides of the binnacle. This entire assembly was called "the brass monkey" presumably because of its appearance. In extremely cold conditions, the differential expansion of the brass and the iron could crack the weld between the brass arm and the iron balls, allowing the balls to crash to the deck. This seems to me a much more credible story than the idea of expecting stacks of cannonballs to stay put in rough weather, although I have not been able to find any other source corroborating this version of the story.