Add spaces: Itwasbecauseofthispublicationthat,inSeptember1624whenhereturnedtoParis,hemetGassendiwhohadbeenaskedtocommentonMersenne'sresults,andlaterbecamehisclosestfriend.
It was because of this publication that, in September 1624 when he returned to Paris, he met Gassendi who had been asked to comment on Mersenne's results, and later became his closest friend.