Additional cables, called backstays, were connected to anchorages behind each tower to balance the horizontal forces, similar to the way suspension bridges work with their towers and abutment anchorages.
Unmindful of the tedious rope-ladders of the shrouds, the men, like shooting stars, slid to the deck, by the isolated backstays and halyards; while Ahab, less dartingly, but still rapidly was dropped from his perch.
You can see the cables let go from Tower 4, the platform swinging downward, the support cables crashing through the suspended catwalk, and the top section of Tower 4 breaking off from the unbalanced force of the backstays.