Black and white photograph of the steamer Medora at the Port Carling Lock, Ontario. Several people are visible on the boat deck and the ground below.

Black and white photograph of the Poe Lock, Sault Ste. Marie, Michigan. A boat is visible in the background.

Black and white photograph of a hydraulic lock in Little Falls, New York.

Black and white photograph of a person standing on a hill of mining spoil in front of several buildings and a smokestack in Little Falls, New York.

Black and white photograph of a partially frozen river in the middle of a city. Buildings are visible on both sides of the river, and there is a bridge across the river in the distance.

Black and white photograph of a lock. A building is next to the lock, and a flagpole and flag are visible in the center of the image. Taken my Merrill while attending the American Society of Civil Engineers conference in New Orleans, Louisiana.

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.

Black and white lantern slide of a breakwater structure near a canal lock at Wei Hu, China.

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

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

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 Chinese canal lock with two gates.