Here's a fairly heavy Spanish seige mortar captured at Manila during the Spanish-American War in 1898. The Spanish Army classified this as a 12-inch mortar since that's what the bore measured in Paris inches, then used by France and Spain. The bore measures almost exactly 13 English (and American) inches. The mortar weighs about 2500 English pounds. At some time before I first photographed it in 1986, someone had sawed off a part of the vent pan. There should be a smooth transition toward the bottom of that feature which terminates in a small ball-like shape, but the bottom inch or so has been sawed off somewhat crudely with a hacksaw. I'm guessing that was done after it arrived at the Naval Academy but there's no way to tell for sure. Why anyone would saw off a part of one of these weapons is a complete mystery to me, the scrap value of that much bronze, maybe a couple of ounces, was negligible at the time it must have been done. The patination looks lighter in that area, so that probably means it was done well after 1925 when most of the weapons were sent to USNA.
You can clearly see the bright green stain on the concrete where the copper is being leached off by atmospheric corrosion. I suspect this is happening to all 23 of the bronze guns displayed outside at USNA, but the concrete or marble foundations that are in more highly visible locations are cleaned regularly. That's a good cure for the corroding cannons, right? Clean up the green stain and you're done for a while!
This mortar is mentioned in passing in the Monument Survey under "Facility No. 716" which is the number assigned to another mortar nearby. For size comparison, the pad of paper in the photos is 8.5 x 11 inches.
If I'm reading the basering inscription correctly is reads: "N. 1306 SEVILLA 4 DE MARZO DE 1784." I'm documenting that here because I don't think the inscription will be legible for too many more years the way the copper is dissolving off of it. The number is the "heat number" as I understand it. The two major royal cannon foundries at Seville and Barcelona marked their larger weapons with the heat number. For speed and efficiency, many cannons were cast at one heating of the furnace, and the heat number was apparently used for some sort of quality-control purposes. I once thought the number was a foundry of serial number for each individual weapon, but I read about the heat number in a book called "The Royal Cannon Foundry of Seville." The book is all in Spanish and I had to figure it out myself, and I don't speak Spanish, so there's always a chance I got it wrong.
http://s17.photobucket.com/albums/b62/cannonmn/miscforumsetc/forums17/?action=view¤t=394dcb48.pbw
