Complex sentence: At the beginning of November, a meeting of 15 reformers at John Doel's house rejected Mackenzie call for an immediate attack on City Hall; they decided to send Mackenzie north to investigate public sentiment.
Split into simpler sentences: At the beginning of November, a meeting of 15 reformers at John Doel's house rejected Mackenzie's call for an immediate attack on City Hall. They instead decided to send Mackenzie north to investigate public sentiment.