The dispatches report that a man connected with one of our American arsenals has about completed a 3-inch machine gun. The ordinary machine gun throws a missile about like a rifle bullet, raining a regular stream of lead upon an advancing enemy; but this invention will make a machine gun out of a 3-inch field piece, which throws a shell ranging from fourteen to eighteen pounds, according to the make of the weapon. Think of what it will mean for an army to be equipped with such slaughtering devices! The rapidity of fire of the largest guns has been increased some ten or twelve times during recent years; and now if these larger weapons are made to carry the machine attachment so that they will pour a steady stream of these missiles, like water from a garden hose, what will be the terror of their destructiveness! It is not at all surprising that the dispatch says this invention will revolutionize the modern cannon.