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Dear Frank,

A question on Lunars may "look like a dinosaur fossil in 1872" to a practically minded person, but not to a phycisit or mathematician. (For example, mathematicians did a lot of research on "compass and ruler constructions", until they nearly exhausted the question. This was long after the question lost all its practical significance). So I can imagine that Kelvin really proposed such questions in Tripos. It would be interesting to see the exact statement.

Kelvin was really thinking a lot about questions of navigation. For example he substantially improved the construction of magnetic compass, and designed the first analog computer for automatic tide prediction. His invention developed into a set of powerful analog computers ("harmonic analizers/syntesizers") of the first half of 20th century. (Once I've seen a collection of these computers in a museum in Btirain; their size, comlexity and precise machinery impressed me).

I remember finding some Tripos problems on Internet, but I am not sure whether all of them are digitalized. One can try to search. Knowledge of the year when it was presumably given will help. And the indication of the year in the joke suggests that the question was really given, since in 1908 anyone in Canbridge could check this:-)

Alex.