Trench warfare, 4 Trenches, 21 barbed wire gates, 9 duck-boards, 9 Tunnels, mines, 17 to observation posts, 12 U-boats, see Submarines Villages, underground, 7 Walking-machine, 108 War, paint, 209 Water kites, 283 Waves, fighting with air, 334 Wireless compass, 201 spy detector, 200 Wireless telegraph, rapid, 199 Wireless telegraphy explained, 188 Wireless telephone, 178 airplane, 184 Wireless telephony across Atlantic, 192 Woolworth Building, falling from, 135 Wrecks, see Salvage Zeppelin and Lowe's balloon, 149 Zeppelin balloon, construction, 156 Zeppelin, suspended observer, 162 Zeppelin's failures and successes, 154 * * * * * * Transcribers' note: Punctuation and spelling were made consistent when a predominant preference was found in this book; otherwise they were not changed. Simple typographical errors were corrected; occasional unbalanced quotation marks retained. Ambiguous hyphens at the ends of lines were retained. Some illustrations have been slightly repositioned to improve their appearance in eBooks. Page 76: "eight tenths of an inch" may be a misprint for "eight ten-thousandths of an inch". Page 100: "inhaled air" was misprinted as "inhaled aid". Page 104: "would send the stream" was misprinted as "sent". Page 113: "Secretely" was printed that way. Page 209: "psycologists" was printed that way.