Complex sentence: The inspectors were assisted by'superintendents', who had none of their powers (the lack of a right of entry being a particular weakness): by the Factory Act of 1844 the superintendents became'sub-inspectors' with the right of entry at will.
Split into simpler sentences: The inspectors were assisted by'superintendents', who had none of their powers (the lack of a right of entry being a particular weakness). By the Factory Act of 1844 the superintendents became'sub-inspectors' with the right of entry at will.