Here are pictures of a rare weapon that you don't see in any modern cannon books. I sent pictures and complete descriptions to an author who was writing a book about artillery, many years ago, but it didn't get in, and so it remains sort of unknown today.
The first photo comes from the National Army Museum in London and has a pencilled-in caption "The Whitworth 3 Pounder Experiment, Liverpool." We think it was taken ca. 1860 because there is a well-documented test of the Whitworth 3-pounder which was conducted at Southport, England in 1860. The gun fired 1.5-inch projectiles (measured flat to flat, since projectiles were roughly hexagonal.) The range achieved was over 9000 yards. Southport is only 20 miles from Liverpool, so the caption-writer could at least conceivably have identified Southport as Liverpool.
I published this photo originally in the ARTILLERYMAN in 1986 in a letter to the editor, after George Wray of Atlanta found it in London while doing some Whitworth research. He sent me a shapshot of the original, and I got the museum to make me this large copy the next time I was in London.
The weapon shown is pictured in drawings and described in a number of 19th C. books (Holley, Fave', etc.) I think my article in the ARTILLERYMAN vol. 7, no. 2, Spring 1986, is the latest hard-copy documentation of it. The article contains pictures and descriptons of the only known surviving 1.5 inch Whitworth breechloader, shown in the second picture. The mounting shown in the second picture is only a display stand.