A minute of longitude is measured East West, and read off
the top or bottom a typical chart.

"Dave" wrote

said:

For longitude lines which converge at the poles things are different.
At the poles a minute of longitude is impossibly short and approaches
zero as you approach the pole.

On second thought, I'll accept your formulation, Bart. When I say one
minute
of longitude, I'm thinking one minute on a longitude line. But I think
you're correct that a minute "of" longitude should properly be regarded as
a
minute measured along a parallel of latitude.