Geissler Tubes. Vacuum Tubes of Crookes, Hittorf, and Lenard. The Cathode Ray. Roentgen’s Great Discovery in 1895. X-Ray Apparatus. Salvioni’s Cryptoscope. Edison’s Fluoroscope. The Fluorometer. Sun- burn from X-Rays. Uses of X-Rays. CHAPTER XXVI. GAS LIGHTING. Early Use of Natural Gas. Coal Gas Introduced by Murdoch. Winsor Organizes First Gas Company in 1804. Melville in United States Lights Beaver-Tail Lighthouse with Gas in 1817. Lowe’s Process of Making Water Gas. Acetylene Gas. Carburetted Air. Pintsch Gas. Gas Meter. Otto Gas Engine. The Welsbach Burner. CHAPTER XXVII. CIVIL ENGINEERING. Great Bridges, Pneumatic Caissons, Tunnels. The Beach Tunnel Shield. Suez Canal. Dredges. The Lidgerwood Cable Ways. Canal Locks. Artesian Wells. Compressed-Air Rock Drills. Blasting. Mississippi Jetties. Iron and Steel Buildings. Eiffel Tower. Washington’s Monument. The United States Capitol. CHAPTER XXVIII. WOODWORKING. Early Machines of Sir Samuel Bentham. Evolution of the Saw. Circular Saw. Hammering to Tension. Steam Feed for Saw Mill Carriage. Quarter Sawing. The Band Saw. Planing Machines. The Woodworth Planer. The Woodbury Yielding Pressure Bar. The Universal Woodworker. The Blanchard Lathe. Mortising Machines. Special Woodworking Machines. CHAPTER XXIX. METAL WORKING. Early Iron Furnace. Operations of Lord Dudley, Abraham Darby, and Henry Cort. Neilson’s Hot Blast. Great Blast Furnaces of Modern Times. The Puddling Furnace. Bessemer Steel and the Converter. Open Hearth Steel. Regenerative Furnace. Siemens-Martin Process. Forging Armor Plate. Making Horse Shoes. Screws and Special Machines. Electric Welding, Annealing and Tempering. Coating with Metal. Metal Founding. Barbed Wire Machines. Making Nails, Pins, etc. Making Shot. Alloys. Making Aluminum, and Metallurgy of Rarer Metals. The Cyanide Process. Electric Concentrator. CHAPTER XXX. FIRE ARMS AND EXPLOSIVES. The Cannon, the Most Ancient of Fire Arms. Muzzle and Breech Loaders of the Sixteenth Century. The Armstrong Gun. The Rodman, Dahlgren, and Parrott Guns. Breech-Loading Ordnance. Rapid Fire Breech-Loading Rifles. Disappearing Gun. Gatling Gun. Dynamite Gun. The Colt, and Smith & Wesson Revolvers. German Automatic Pistol. Breech-Loading Small Arms. Magazine Guns. The Lee, Krag-Jorgensen, and Mauser Rifles. Hammerless Guns. Rebounding Locks. Gun Cotton. Nitro Glycerine, and Smokeless Powder. Mines and Torpedoes. CHAPTER XXXI. TEXTILES.