Complex sentence: The Demerara region was opened to settlement in 1746, and new opportunities attracted British settlers from nearby Barbados who, by 1760, had become the largest contingent there--the 1762 business registers showed that 34 of 93 plantations owned by Englishmen.
Split into simpler sentences: The Demerara region was opened to settlement in 1746, and new opportunities attracted British settlers from nearby Barbados. By 1760, they had become the largest contingent in Demerara; the 1762 business registers showed that 34 of 93 plantations owned by Englishmen.