Looking at an old-time cannon, most people are sure of just one thing: the shot came out of the front end. For that reason these pages are written; people are curious about the fascinating weapon that so prodigiously and powerfully lengthened the warrior's arm. And theirs is a justifiable curiosity, because the gunner and his "art" played a significant role in our history. The development of heavy ordnance through the ages is a subject with many fascinating ramifications, but this survey has of necessity been brief. It has only been possible to indicate the general pattern. Most of the interesting details must await the publication of much larger volumes. It is hoped, however, that enough information has been included herein to enhance the enjoyment that comes from inspecting the great variety of cannon and projectiles that are to be seen throughout the National Park System.