tools operated by compressed air. Most pneumatic tools are hand tools, and the mechanism for operating them is placed in the handle. They are divided into two classes--those which work as hammers and those which have a rotary motion. To the first class belong the hammer proper, chipping tools, rock drills, riveting machines and caulking machines. The rotary tools include various kinds of boring machines for metal and wood. The tools of the first class are used in metal working and in carving wood. The air is conveyed to the handle by a flexible hose and usually has a pressure of from 80 to 90 pounds to the square inch, except for riveting machines, in which it has a pressure of about 125 pounds to the square inch. The speed and force with which the tool operates are controlled by means of a valve in the handle.