Lock at Muscle Shoals, Alabama.

Black and white lantern slides of canal locks with raised bridges in China.

Black and white lantern slide of a Chinese canal lock with two gates.

Black and white lantern slide close-up view of a recessed space carved into the brick wall holding a wooden beam. Ropes and other mechanisms are visible at the top of the frame.

Black and white lantern slide of a hand-drawn sketch diagram of canal lock systems.

Black and white photograph of steamships passing thorugh the Gatun Dam locks in Panama. Several people are standing along the edge of the lock to watch the ships pass. "Gatun Locks." is written on the bottom of the image.

Locks on the Kentucky River at Frankfort, Kentucky.

Locks on the Kentucky River at Frankfort, Kentucky.

Locks on the Kentucky River at Frankfort, Kentucky.

Paddleboat at the locks on the Kentucky River at Frankfort, Kentucky.

Paddleboat at the locks on the Kentucky River at Frankfort, Kentucky.

Paddleboat at the locks on the Kentucky River at Frankfort, Kentucky.