The Thames Tunnel is a tunnel beneath the river Thames, connecting Rotherhithe and Wapping. The tunnel is the first to have been successfully constructed beneath a river. It was built from 1825-1843 by Marc and Isambard Brunel. The tunnel was intended for horse-drawn carriages and became a tourist attraction as well as a site for crime and prostitution. Since 1869, it has been used as a railway tunnel.

In London Labour and the London Poor edition: 

Phase 1

A Visit to the Cholera Districts of Bermondsey  (Morning Chronicle): "Thénard also has proved that one eight hundredth part of this gas in the atmosphere is sufficient to destroy a dog, and one two hundred and fiftieth will kill a horse; while Mr. Taylor, in his book on poisons, assures us that the men who were engaged in excavating the Thames Tunnel suffered severely during the work from the presence of this gas in the atmosphere in which they were obliged to labour."