Interestingly, the word 'cambric' (some sort of fabric) is also pronounced
with a long 'a'. This could, however, be because the Flemish town from which
it takes its name is Kameryk, with an open first syllable (subsequently closed
as the second syllable was lost).
Richard Coates's mention of the Latin form of the river-name puzzles me
slightly as I thought the form Cam was considered to be a back-formation from
The long 'e' in 'ingenious' (or 'genius') accords with the usual rules for
English Latin pronunciation: antepenultimate stressed 'e' is long if open and
a hiatus occurs in the last three syllables, otherwise short (contrast
'genius' with 'genera' /'dZEn@r@/, plural of 'genus' /'dZi:n@s/).