Complex sentence: Mistaking smoke for a kind of steam, they began filling their balloons with hot smoky air which they called "electric smoke" and, despite not fully understanding the principles at work made some successful launches, and in December 1782 flew a cu.m.
Split into simpler sentences: Mistaking smoke for a kind of steam, they began filling their balloons with hot smoky air which they called "electric smoke". Despite not fully understanding the principles at work they made some successful launches and in December 1782 flew a cu.m.