| Oil-tempering the lining of a big gun | Frontispiece |
| FACING
PAGE |
| Lines of zig-zag trenches as viewed from an aËroplane | 8 |
| French sappers using stethoscopes to detect the mining operations of the enemy | 9 |
| A 3-inch Stokes mortar and two of its shells | 36 |
| Dropping a shell into a 6-inch trench mortar | 36 |
| The Maxim machine-gun operated by the energy of the recoil | 37 |
| Colt machine-gun partly broken away to show the operating mechanism | 37 |
| The Lewis gun which produces its own cooling current | 44 |
| The BenÈt-MerciÉ gun operated by gas | 44 |
| Browning machine-gun, weighing 34½ pounds | 45 |
| Browning machinw-rifle, weight only 15 pounds | 45 |
| Lewis machine-guns in action at the front | 52 |
| An elaborate German machine-gun fort | 53 |
| Comparative diagram of the path of a projectile from the German super-gun | 60 |
| One of our 16-inch coast defence guns on a disappearing mount | 61 |
| Height of gun as compared with the New York City Hall | 61 |
| The 121-mile gun designed by American ordnance officer | 68 |
| American 16-inch rifle on a railway mount | 69 |
| A long-distance sub-calibered French gun on a railway mount | 76 |
| Inside of a shrapnel shell and details of the fuse cap | 77 |
| Search-light shell and one of its candles | 77 |
| Putting on the gas-masks to meet a gas cloud attack | 84 |
| Even the horses had to be masked | 85 |
| Portable flame-throwing apparatus | 85 |
| Liquid fire streaming from fixed flame-throwing apparatus | 92 |
| Cleaning up a dugout with the "fire-broom" | 93 |
| British tank climbing out of a trench at Cambrai | 112 |
| Even trees were no barrier to the British tank | 113 |
| The German tank was very heavy and cumbersome | 113 |
| The speedy British "Whippet" tank that can travel at a speed of twelve miles per hour | 120 |
| The French high-speed "baby" tank | 120 |
| Section through our Mark VIII tank showing the layout of the interior | 121 |
| A Handley-Page bombing plane with one of its wings folded back | 128 |
| How an object dropped from the Woolworth Building would increase its speed in falling | 129 |
| Machine-gun mounted to fire over the blades of the propeller | 136 |
| Mechanism for firing between the blades of the propeller | 136 |
| It would take a hundred horses to supply the power for a small airplane | 137 |
| The flying-tank | 144 |
| An N-C (Navy-Curtiss) seaplane of the type that made the first flight across the Atlantic | 145 |
| A big German Zeppelin that was forced to come down on French soil |
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