This is a photo of the J Haines dry dock that was in Middleport. The photo is dated 1909, and was taken when the dry dock existed on the canal.

What is a dry dock?
A dry dock  is a narrow basin or vessel that can be flooded to allow a load to be floated in, then drained to allow that load to come to rest on a dry platform. Dry docks are used for the construction, maintenance, and repair of ships, boats, and other water craft, and this one was in Middleport at the turn of the century.