Just an image from Dickens' Our Mutual Friend... but what is THAT?

by Bognis

This picture is cropped from the opening illustration to Dickens' Our Mutual Friend. It's the original illustration by Marcus Stone and was thus drawn in around 1864/1865, and the action depicted is described as taking place between Southwark and London Bridges. My question is "what is that curious Shard-like structure on the horizon?" I'm afraid I can't make any sense of it.

Bodark43

That thing looks to be a hoisting tripod, called sheers or sheer-legs