Brass Monkeys and Cold Weather

Many messages have addressed the implausibility of the nautical cannonball derivation of the otherwise
entertaining expression, "Cold enough to freeze the balls off a brass monkey." And the article in
"Meanings and origins of phrases and sayings" includes a scientific analysis to demonstrate the
unlikelihood that the expression could have come about this way. My minor contribution is to point
out that this quantitative analysis incorrectly concludes that a 200 degree Celcius drop in temperature
would cause a one-meter leg on the triangular "monkey" to shrink relative to the cast iron balls by
"a quarter of a millimetre" and is in error by an order of magnitude (factor of about 10). A leg would
shrink relative to a one-meter row of cannonballs by about 2 mm. This still is not enough to push the
cannonballs up and out of the frame constraining them, so the argument about the implausibility of this
supposed derivation still holds up. And a temperature change of 200 C is extremely unlikely on
shipboard, so the shrinkage will be even less than 2 mm (but not nearly as small as 1/4 of
a mm) over one m of original length.

For those interested in the calculation, the most reliable values I could find for the linear coefficients of
thermal expansion for brass and gray cast iron are 0.0000199/degree C and 0.0000105/degree C
respectively (from the ASM Metals Reference Book). So if a one-meter long leg of a brass triangle
"monkey" were cooled -200 degrees C, it would shrink unconstrained by 0.00398 m, or about 4 mm.
And a one-meter long row of cast iron cannonballs would shrink less, about 0.0021 m, or about 2 mm.
The difference between these two contractions is obviously about 2 mm (1.88 mm without rounding),
an order of magnitude larger than the "quarter of a millimetre" in the cited article. Not a big deal, and
not a large enough difference to invalidate the conclusion that the nautical cannonball explanation for
the expression cannot hold up, but when science is invoked, the calculations should at least be the right
order of magnitude.

In actuality, the outward force of the cannonballs pushing along the leg of the brass triangle would
prevent the brass from contracting the full 4 mm, and the inward force of the triangle along the row of
cannonballs adjacent to the brass leg would cause the cast iron balls to contract more than the
calculated 2 mm. The joint contraction for both the cannonballs and the triangle leg probably would be
about 2 to 3 mm. And a temperature change of -200 C is too extreme to be plausible. A temperature
of -100 C (equal to -180 F) probably is larger than any ship on the high seas would be expected to
experience, which would decrease the maximum expected shrinkage to about 1 to 1.5 mm, even less
likely than 2 to 3 mm to cause the cannonballs to fall off/out of the triangle (whether or not it was
called a "monkey") but still greater than 1/4 mm.

Are you sure? perhaps the textbooks on co-efficients need revising and anyway. if you packed the cannonballs tight enough (sub 1mm gap) and placed a small oxy-acetelene torch with the jet directed into the pyramid to keep them warm, (entirely plausible as they sometimes used to heat shot to maximise it's destructive power against fortifications) ; wouldn't accidentally dropping a keg of liquid nitrogen on the deck (missing the pyramid of shot) cause them to pop out? You wouldn't read of such a situation actually happening because the likely destructive effect would kill any witnesses and the oxy torch and the thermally insulated cannister would be blown through the porthole on the gun deck in the explosion.
Perhaps the expression started as "cold enough to freeze the superheated balls off a supercooled brass monkey"?

Actually "brass" is a slang term for prostitute (as in the need to give her some coinage to have sex) and a "monkey" was a cabin boy, so a "brass monkey" might be a cabin boy that sold sexual favours. On a ship, it might be necessary to go either into the cold-store or the forecastle to do such a thing in private and so perhaps these brass-monkeys used to suffer frostbite on the extremities. if the brass-monkey was the active not passive part of the duo, the risk of exposure to the testicles ("balls") would support it being a nautical term for being very cold and it might have been a kindly warning to such catamites.