A tidbit of knowledge

It was necessary to keep a good supply of canon balls near the
>> cannon on war ships. But how to prevent them from rolling about the
>> deck was the problem.
>>
>> The best storage method devised was to stack them as 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/rolling from under the others. The solution was a metal plate
>> with 16 round indentations, called a Monkey.
>>
>> But if this plate was madeof 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 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 vulgar
>> expression, didn't you?