Those guns that have survived often provide a wealth of historical information. They are almost always more ornate than common iron guns. Because they corrode only very slowly, the markings remain visible even after the passage of centuries. In order to decipher the information embedded in such a cannon, it is necessary to know a little about technology, a lot about history . . . The trick to wringing information from a cannon is not having an encyclopedic knowledge of all cannons, but rather knowing how to record it in sufficient detail to show someone on the other side of the world exactly what it looks like.
Photographs are nice, but cannon experts prefer to work from detailed scale drawings.
Such a drawing will require something on the order of one hundred measurements everything from the diameter of the vent to the length of the first reinforce. There is a specialized vocabulary for the different parts of a cannon. They allow the cannon to be mounted on a carriage. When a military unit was in danger of having its guns captured, it was common practice to knock off the trunnions, rendering the cannons useless. For better or for worse, firearms have been with us so long that they have become part of our culture and our vocabulary.