Complex sentence: Between January 30,1819 and January 22,1830, the society's membership rolls reached 52 members; although as few as 15 members attended the bimonthly meetings, and no more than 17 members were ever present at a meeting.
Split into simpler sentences: Between January 30,1819 and January 22,1830, the society's membership rolls reached 52 members, and regularly as few as 15 members attended the bimonthly meetings. No more than 17 members were ever present at a meeting.