There's more to them than meets the eye:

The term brass monkey appears to have originated with the British army in India.

The monkey was brass which has a higher or lower (can't remember which) coefficient of expansion than iron. They were either triangular or rectangular. If the temperature fell below about -5degC for more than an hour or so, the monkey contracted, only slightly, but enough. Off came the cannon balls, and hence the expression. But they were probably never used on ships except for ceremonial occasions, although they were used in land-based forts. The reason why they weren't very practical onboard warships was that in rough weather the balls would fall off anyway, and the last thing you would want is iron balls rolling around the deck in a blow.

The monkeys were apparently made on a 'one-size-fits-all' basis for one particular cannon calibre. Since cannon balls came in varying diameters depending on the bore size of the cannon, the balance of the balls on the monkey would probably have been rather, um, delicate in a lot of cases. It would therefore sometimes have required only a very small amount of contraction in the monkey to produce the effect.

The term "monkey" is easily explained. Boys were employed to convey the gunpowder charges from the magazines to the cannon, both on ships and on land. They were called "powder monkeys" because the crawlspace between the magazine and the firing positions was kept as small as possible to prevent flash fires. More than one ship scored an own goal this way in the heat of battle. In spite of being small, the boys always had to run crouched because of the extremely low overhead, and were called "monkeys" because of this crouching posture. On board warships, the powder monkeys were also responsible for keeping the supply of cannonballs up to the cannon position. The term was transferred to the brass triangle or rectangle that was used to "deliver" the cannon balls in land forts. Sailors and soldiers are nothing if not economical with their nomenclature, obviously.

I understand that you can still see examples of brass monkeys in some preserved forts, particularly the citadel in Gibraltar.

As an aside, the Otago Motorcycle Club here in Zild runs a mid-winter rally into central Otago over the old coach road called "The Brass Monkey Rally". I rode on it a few times myself in the early years. Usually it is pretty cold, but one year some people suffered from heatstroke!

Hope this was interesting ... apologies otherwise.


The idiot also known as Capfka ...