The Kingston Dry-dock as it appeared in early 1891.
Docked is the passenger steamship St. Lawrence. The Engine House, 
with the pumping engines in place is now part of the Marine Museum.

The gate, in the outer position can be seen behind the staging. The sill is the curved stone.
Normally the gate would be moved across the entrance of the dry-dock on the rollers shown just below the sill. In this instance the dry-dock is being repaired thus the gate in the outside position.
This remarkable piece of industrial archaeology is intact as shown in this 1950s photograph.

Detail of gate shown above.
Rollers support the gate as it is moved across the entrance to the dry-dock.