isle > ile?

I was looking at a book I had borrowed from my school's library, and in
it, there is a French map of the Philippines dating from 1682. What struck
me was that instead of ile, they used isle, for island (not odd in and of
itself). It got me to wondering, was the s still pronounced then? If not,
how long did it take for is to stop being pronounced in that word, and
when did the French decide to write island as ile?

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Yours truly,

Cesar Javier Jaime Garcia