Complex sentence: The cowl could either be lowered inverted, or alternatively, a ladder would be placed against the kiln roof and the cowl be carried down by the wheelwright, the weight being mainly taken by those in the kiln working on the rope.
Split into simpler sentences: The cowl could either be lowered inverted, or alternatively, a ladder would be placed against the kiln roof and the cowl be carried down by the wheelwright. The weight being mainly taken by those in the kiln working on the rope.