VEHICLES OF THEM A POPULAR EXPOSITION OF MODERN AERONAUTICS WITH WORKING DRAWINGS VICTOR M3UGBEED GIFT OF Vehicles of the Air The Bleriot Monoplane, which Crossed the English Channel, Enthroned on the Stand of Honor in the Grand Palais, Paris, October, 1909. Reproduction of Original Montgolfier Balloon in Background. View down main hall of Paris Aeronautical Salon, which closed October 15, 1909. The value of the exhibits and accessories, the cost of the decorations, and the attendance was far greater than at any automobile show ever given in the United States or Europe. It was the second annual event of the kind to be held in Paris and a large number of orders for various makes of machines was placed for future delivery 110 being for one well-known monoplane. VEHICLES OF THE AIR A. Popular Exposition of Modern Aeronautics With Working Drawings By VICTOR LOUGHEED Member of the Aeronautic Society, Founder Member of the Society of Auto- mobile Engineers, former editor of Motor, and author of "Some Trends of Modern Automobile Design." PUBLISHERS THE REILLY AND BRITTON CO. CHICAGO Entered at Stationers* Hall Copyright. 1909. by the Reilly and Britton Co, AH Rights Reserved PHOTOGRAPHS BY M. Branger. E. Filiatre, M. Rol, and J. Theodoresco, of Paris. All illustrations herein are fully protected by international copyright. Reproductions positively will not be permitted without due credit, and written authorization from the publishers. Published November 1909 TABLE OF CONTENTS INTEODUCTION Scope and Prophecy 21 Skepticism is Ignorance 23 Three Traversable Media 24 Types of Air Craft 24 Aeroplane Most Successful 26 Speed and Radius 27 Sizes of Aeroplanes 28 First and Operating Costs ; 28 The Moral Aspect 29 The Physical Hazard 29 Dangers in All Travel 32 Fear a Habit of Mind 33 Commercial Applications 34 Limitations Expected 35 Relation to Warfare 36 An Imaginative Spectacle 37 Travel over Water 38 Conclusion 39 CHAPTEE 1 THE ATMOSPHEEE Introduction 43 EXTENT 43 PEOPEETIES AND CHAEACTEEISTICS 45 Weight 45 Composition 46 Color and Transparence 48 AIE AT EEST. 48 Compressibility 49 Effect of Temperature 49 Liquefaction and Solidification 50 AIE IN MOTION 50 Inertia 51 Elasticity 52 Viscosity 53 METEOEOLOGY 53 Temperature 54 Barometric Pressure , 56 Humidity 56 Condensation of Moisture 57 Winds 57 Coastal Winds 59 Trade Winds 60 - Cyclones, Whirlwinds, and Tornados 61 Ascending Components 62 Wind Velocities 62 Atmospheric Electricity 64 7 4645* u 8 VEHICLES OF THE AIR CHAPTER 2 UGHTER-THAN-AIR MACHINES Introductory 65 NON-DIRIGIBLE BALLOONS 66 History 66 Spherical Types 75 DIRIGIBLE BALLOONS 76 History 80 Spherical Types 88 Elongated Types 89 Pointed Ends 89 Rounded Ends 90 Sectional Construction 90 The Effect of Size 90 Envelope Materials 91 Sheet Metal 92 Silk 93 Cotton 93 Linen 94 Miscellaneous Envelope Materials 94 Coating Materials 95 Inflation 96 Heated Air 97 Hydrogen 98 Illuminating Gases 101 Vacuum 101 Miscellaneous 102 Nettings 103 Car Construction 104 Rattans 105 Wood 106 Miscellaneous 106 Height Control 106 Non-Lifting Balloons 107 Escape Valves 107 Ballast 109 Compressed Gas 109 Drag Ropes 110 Open Necks HO Internal Balloons Ill Moisture 112 Temperature 112 Steering 113 Lateral Steering 113 Vertical Steering 114 Balloon Housing 115 Sheds 115 Landing Pits 116 CHAPTER 3 HEAVIER-THAN-AIR MACHINES Introductory 117 ORNITHOPTERS 118 History 118 Two Chief Classes 124 Recent Ornithopters 124 Analogies in Nature 124 HELICOPTERS 125 History 126 CONTENTS 9 Recent "Experiments . 129 Lateral Progression . 130 Analogy with Aeroplane 131 AEROPLANES 131 AEROPLANE HISTORY 132 Clement Ader 134 Louis Bleriot 135 Octave Chanute 136 Samuel Pierpont Langley 136 Otto and Gustav Lilienthal . 137 John J. Montgomery 138 A. Penaud 146 Percy S. Pilcher . 147 Alberto Santos-Dumont 148 F. E. Wenham 149 Wilbur and Orville Wright 149 Voisin Brothers 153 Miscellaneous 153 CHAPTER 4 AEROPLANE DETAILS Introductory 158 ANALOGIES IN NATURE 159 Flying Fish 161 Comparison of Flying Animals and Aeroplanes 162 Flying Lizards 163 Flying Squirrels 163 Flying Lemur 163 Flying Frog 164 Soaring Birds 164 Soaring Bats 165 The Pterodactyl 165 Flying Insects 166 MONOPLANES 167 MULTIPLANES 168 Biplanes 169 More Than Two Surfaces 169 FORMS OF SURFACES 169 Flat Sections 171 Curved Sections 1 72 Arcs of Circles 172 Parabolic Surfaces 173 Force and Motion 193 Momentum 194 Action and Reaction 194 Impact of Elastic Bodies 195 The Impact of Fluids 198 Application 199 Flattened Tips 203 Angles of Chords 204 Wing Outlines : 204 Length and Breadth 204 ARRANGEMENTS OF SURFACES 205 Advancing and Following Surfaces 205 Superimposed Surfaces 205 Staggered Surfaces 205 Lateral Placings ; 206 Separated Wings I 206 Continuous Wings 206 10 VEHICLES OF THE AIR Lateral Curvature 207 Dihedral Angles 207 VERTICAL SURFACES -. 209 SUSTENTION OF SURFACES 210 Effect of Section 210 Effect of Angle 211 Effect of Speed 211 Effect of Outline 212 Effect of Adjacent Surfaces 212 Center of Pressure 213 Head Eesistances 213 METHODS OF BALANCING 215 Lateral Balance 215 Vertical Surfaces 216 Dihedral Angles 216 Wing Warping 216 Tilting Wing Tips 217 Hinged Wing Tips 217 Variable Wing Areas 218 Shifting Weight 218 Rocking Wings 218 Swinging Wing Tips 219 Plural Wing Tips 220 Longitudinal Balance 220 By Front Rudders 220 By Rear Rudders 220 Box Tails '. 220 Shifting Weights 221 Elevators as Carrying Surfaces 221 Automatic Equilibrium 221 Arrangement of Surfaces 222 Electric Devices 222 The Gyroscope 222 Compressed Air 223 The Pendulum, 223 STEERING 223 Effects of Balancing 223 Vertical Eudders 224 Pivoted Rudders 224 Flexible Rudders 224 Horizontal Eudders 225 Twisting Eudders 225 CONTROLLING MEANS 226 Compound Movements .- 227 Plural Operators 227 Wheels 228 Levers 228 Pedals - 229 Miscellaneous 229 Shoulder Forks 229 Body Cradles 229 FRAMING 230 CHAPTER 5 PROPULSION Introductory 231 MISCELLANEOUS PROPELLING DEVICES 231 Feathering Paddles Wave Surfaces 233 CONTENTS 11 Reciprocating Wings and Oars 234 SCREW PROPELLERS 236 Some Comparisons 237 Essential Characteristics 238 Effective Surface 241 Angles of Blades 242 Slip !'..!..'.! 244 Forms of Surfaces 244 Plane Sections 245 Parabolic Sections 245 Blade Outlines 246 Multibladed Propellers 248 Two-Bladed Propellers 249 Propeller Diameters 250 Arrangements of Blades 252 Right-Angled Propeller Blades 252 Dihedrally -Arranged Propeller Blades 253 Propeller Efficiencies 253 The Effects of Form 255 The Effects of Rotational Speed 255 The Effects of Vehicle Speed 256 The Effects of Skin Friction 257 Propeller Placings 258 Single Propellers 259 Plural Propellers 259 Location of Propeller Thrust 264 Propeller Materials 264 Wood 265 Steel 268 Aluminum Alloys 268 Framing and Fabric 269 Propeller Hubs 269 A TYPICAL PROPELLER 270 CHAPTER 6 POWER PI*ANTS Introductory 273 GASOLINE ENGINES 277 Multicylinder Designs 277 Cylinder Arrangements 279 Vertical Cylinders 279 V-Shaped Engines "280 Opposed Cylinders 281 Revolving Cylinders 282 Miscellaneous Arrangements 284 Ignition 284 Make-and-Break Ignition , 284 Jump-Spark Ignition 285 Hot-Tube Ignition 287 Ignition by Heat of Compression 287 Catalytic Ignition 288 Cooling 288 Water Cooling 289 Air Cooling 290 Carluretion 291 Carbureters 291 Fuel Pumps 294 12 VEHICLES OF THE AIR Muffling 296 Auxiliary Exhausts 297 Flywheels 297 STEAM ENGINES 299 Available Types 301 Boilers 301 Burners 303 Fuels 303 Comparison of Fuels 304 ELECTRICITY 304 Electric Motors 304 Current Sources 305 Storage Batteries , 306 Primary Batteries 307 Thermopiles 307 MISCELLANEOUS 308 Compressed Air 309 Carbonic Acid 309 Vapor Motors 309 Spring Motors 310 EocTcet Schemes 310 TANKS 310 CHAPTER 7 TRANSMISSION ELEMENTS Introductory 313 CHAINS AND SPROCKETS 314 Block Chains 316 Eoller Chains 317 Miscellaneous 317 Block Chains 317 Standard American Roller Chains 318 Roller Chains 318 Cable Chains 319 Reversible Sprockets 319 Missed Teeth 319 SHAFTS AND GEARS 320 Shafts 32 Spur Gears 321 Bevel Gears ' 322 Staggered and Herringbone Teeth 323 BELTS AND PULLEYS 324 Pulley Construction 324 Belt Materials 325 CLUTCHES 325 CHAPTER 8 BEARINGS Introductory 327 BALL BEARINGS 328 Adjustable Ball Bearings 328 Annular Ball Bearings 330 Annular Ball-Bearing Sizes, Capacities, and Weights 337 ROLLER BEARINGS 339 Cylindrical Eoller Bearings 340 Flexible Eoller Bearings 340 Tapered Eoller Bearings 341 PLAIN BEARINGS 342 Plain Bearing Materials 342 Steel . 342 CONTENTS 13 Oast Iron 343 Bronzes 343 Brasses 343 Babbitt 343 Graphite 344 Wood 344 Vulcanized Fiber 344 Finish of Plain Bearings 344 Areas 344 Scraping 345 MISCELLANEOUS BEARINGS 346 CHAPTER 9 LUBRICATION Introductory 347 SPLASH LUBRICATION 347 Ring and Chain Oilers 348 GRAVITY LUBRICATION 349 Oil Cups 349 Reservoir Systems 350 FORCED LUBRICATION. 350 Pressure Feed 350 Single Pumps 351 Multiple Pumps 351 Grease Cups 352 LUBRICANTS 352 Mineral Oils 352 Vaseline 353 Vegetable Oils 353 Castor Oil 353 Olive Oil 353 Animal Oils 354 Sperm Oil 354 Tallow 354 Miscellaneous Lubricants 354 Water 354 Kerosene 355 CHAPTER 10 STARTING AND ALIGHTING Introductory 356 STARTING DEVICES 357 Wheels 358 Rails ; 358 Floats 359 Runners 360 The Starting Impulse 360 Propeller Thrust 361 Dropped Weights 362 Winding Drums 363 Inclined Surfaces 364 Launching Vehicles 365 Automobiles 365 Railway Cars 365 Boats 366 Cleared Areas 366 Facing the Wind 367 Launching from Height 368 ALIGHTING GEARS 369 Wheels . 369 14 VEHICLES OF THE AIR Runners 370 Floats 370 Miscellaneous 371 CHAPTER 11 MATERIALS AND CONSTRUCTION Introductory 372 WOODS 373 Hardwoods 374 Applewood 375 Ash 375 Bamboo 375 Birch 376 Boxwood 376 Elm 376 Hemlock 377 Hickory 377 Holly 378 Mahogany 378 Maple 378 Oak 378 Walnut 378 Softwoods 379 Pines 379 Poplar 379 Spruce 379 Willow 380 Veneers and Bendings , 380 METALS 381 Iron 382 Steel 382 Alloy Steels 383 Cast Iron 384 Aluminum Alloys 384 Aluman 384 Argentalium 385 Chromaluminum 385 Magnalium 385 Nickel- Aluminum . , 385 Partinium 385 Wolframinium 385 Brasses and Bronzes 386 Aluminum Bronze ; 386 Phosphor Bronze 386 Metal Parts 386 CORDAGE AND TEXTILES 387 Linen 388 Silk 388 PAINTS AND VARNISHES 388 Oils 388 Shellacs 389 Spar Varnishes 389 Aluminum Paint 389 Miscellaneous 389 MISCELLANEOUS 389 Catgut 389 China Grass 390 Hair 390 Rawhide 390 CONTENTS 15 Silk Cord 390 Silkworm Gut 390 ASSEMBLING MATERIALS AND METHODS 390 Nails 390 Glues and Cements 390 Screws 391 Bolts 391 Clips 391 Rivets 391 Electric Welding 391 Autogeneous Welding 391 Brazing 391 Soldering 392 Tabular Comparisons of Materials 392 Metals 393 Miscellaneous Materials 393 Transverse Strength of Wood Bars 393 Woods 393 CHAPTER 12 TYPICAL AEROPLANES Introductory 394 Antoinette Monoplanes 396 Bleriot Monoplanes 396 Chanute Gliders 398 Cody Biplane 399 Curtiss Biplane 400 Farman Biplane 404 Langley Machine 404 Lilienthal 's Machines 404 Maxim Multiplane 405 Montgomery Machine 406 Pilcher Gliders 407 E. E. P. Monoplanes 408 Santos-Dumont Monoplane 408 Voisin Biplane 409 Wright Biplane 409 CHAPTER 13 ACCESSORIES Introductory . . . . 410 LIGHTING SYSTEMS 410 Electric Lighting 411 Advantages of Uniform Motor Speed 411 Arc Lamps 411 Incandescent Lamps 412 The Nernst Lamp 413 Acetylene 413 Storage Tanks 414 Acetylene Generators 414 Acetylene Burners 415 Oxygen Systems 416 With Hydrogen * 416 With Gasoline 416 With Acetylene 416 Incandescent Mantles 416 With Gas 417 With Liquid Fuels 417 Oil Lamps 417 Sperm Oil 417 Kerosene ,.,...,..,,..,, 418 16 VEHICLES OF TEE AIR Reflectors 418 Arrangement of Lights 419 SPEED AND DISTANCE MEASUEEMENTS 420 Anemometers 420 Miscellaneous 421 COMPASS 422 Fixed-Dial Compasses 423 Floating-Dial Compares 423 BAROMETERS 424 Mercurial Barometers 424 Aneroid Barometers 424 WIND VANES 425 MISCELLANEOUS INSTRUMENTS 425 CHAPTER 14 MISCELLANY Introductory 427 APPLICATIONS 428 Warfare 429 Sport 432 Mail and Express 433 News Service 434 Effects of Low Cost and Maintenance 434 General Effects 435 RADII OF ACTION 436 Influence of Wind 437 DEMOUNTABILITY 437 PASSENGER ACCOMMODATION 439 Seats 440 Housing 440 Upholstery 440 Pneumatic Cushions 440 Heating 441 By the Exhaust 441 PARACHUTES 442 DESIGNING 443 TESTING AND LEARNING 444 Learning from Teacher 444 Practice Close to the Surface 444 Practice over Water 445 Maintaining Headway 445 Landing 445 AERIAL NAVIGATION 446 Flying High 446 Steadier Air 446 Choice of Landing 447 Flying Low 447 Falling 448 Striking Obstacles >. 448 Vortices and Currents 448 TERRESTRIAL ADJUNCTS 449 Signals 449 Fog Horns and Whistles 450 PATENTS 451 GLOSSARY OF AERONAUTICAL TERMS 464 CHAPTER 15 FLIGHT RECORDS Introductory 473 TABULAR HISTORY OF FLIGHTS 476 LIST OF ILLUSTRATIONS FIGURE. PAGE. Bleriot Monoplane at Paris Aeronautical Salon Frontispiece General View of Paris Aeronautical Salon Frontispiece 1. Bleriot Flying from Etampes to Orleans 43 2. View in Paris Aeronautical Exhibition October, 1909 65 3. Layout of Gores for Spherical Balloon 76 4. Giffard's Dirigible Balloon 80 5. Tissandier's Dirigible Balloon 81 6. Renard's and Krebs' Dirigible Balloon 82 7. Texture of Modern Balloon Fabrics 65 8. Modern Spherical Balloon 90 9. Shuttles for Knotting Balloon Nettings, and Some Typical Knots.. 104 10. Balloon Valve 108 11. Car of Modern Spherical Balloon 90 12. Curious Drag Rope of Wellman Dirigible 94 13. Internal Balloon Ill 14. Balloon House for Dirigible "Russie" 94 153. Portable Balloon House Used By the French Army 96 16. Balloon Houses Nearing Completion 96 17. Rigid Construction of Zeppelin Dirigible 100 18. Dirigible Balloon, "Ville de Nancy" 104 19. Side View of Nacelle of Wellman Dirigible 108 20. Front View of Nacelle of Wellman Dirigible 108 21. Malicot Semi-Rigid Dirigible Balloon 104 22. Nacelle of the French Dirigible, "Zodiac III" 104 23. Count de Lambert Piloting Wright Biplane 117 24. Degen's Orthogonal Flier 120 25. Trouve's Flapping Filer 121 20. Engine and Wing Mechanism of Hargrave Model No. 18 122 27. Collomb Ornithopter 126 28. Toy Helicopter 127 29. Toy Helicopter 128 30. Toy Helicopter 128 31. Bertin Helicopter 126 32. Cornu Helicopter 140 33. Bertin Helicopter- Aeroplane 140 34. Box Kite 133 35. Henson Aeroplane of 1843 140 36. Le Bris' Glider 155 37. Moy's Aerial Steamer 156 38. Flying Fish 161 39. Flying Frog 164 40. Comparison of Pterodactyl and Condor 166 41. Wing-Case Insect 166 42. Pressure on Vertical and Inclined Surfaces 171 43. plane and Arched Surfaces without Angle of Incidence 172 44 to 67. Geometrical and other Drawings Explaining the Formation and Action of Wing Surfaces 176-199 68. Staggered Biplane. 205 69. Goupy Biplane 158 70. Langley's 25-Pound Double Monoplane 208 71. Internal Framing of Antoinette Monoplane Wing 158 72. Framing of Antoinette Wing Inverted 158 73. Framing of Bleriot Monoplane Wing 164 74. inverted Upper Wing Frame of Wright Biplane 164 75. Assembling Wright Wing Frames 170 76. Aileron Control of Lateral Balance in Antoinette Monoplane 170 77. Aileron Control of Bleriot Monoplane VIII 170 78. Lejeune Biplane with Double Aileron Control 174 79. Front View of Pischoff and Koechlin Biplane 174 80. Side View of Pischoff and Koechlin Biplane 174 17 18 VEHICLES OF THE AIR FIGURE. PAGE. 81. Aileron Control of Farman Biplane 174 82. Sliding Wing Ends 218 83. Swinging Wing Ends 219 84. Wright Flexible Elevator or Rudder 225 85. Rear Controls of Antoinette Monoplane 226 86. Double Control from Single Wheel 226 87. Shoulder-Fork Control 228 88. Frame of New Voisin Biplane 230 89. Fuselage of Bolotoff Monoplane 230 90. Feathering-Paddle Flying Machine 232 91. Partially-Housed Paddle Wheel 233 92. Wave Surface 233 93. Helices of Propeller Travel 239 94. Circles of Propeller Travel 239 95. Diagram of Propeller Pitch 240 96. Angle of Propeller Blade to Angle of Travel 242 97. Advancing and Following Surfaces 248 98. Three-Bladed Propeller 231 99. Four-Bladed Propeller 231 100. Chauviere Walnut Propeller 234 101. Propeller, Engine, and Wing Frame of Antoinette Monoplane.... 234 102. Engine and Propeller of Santos-Dumont Monoplane 234 103. Wooden Propeller of Clement Dirigible Balloon 240 104. All-Metal Propeller Applied to Dirigible Balloon 240 105. Straight, Dihedral, and Curved Propellers 252 106. Effect of Gyroscopic Action of Single Propeller on Steering 263 107. Twin Wood Propellers on Single Shaft 264 108. Working Drawings of a Wooden Propeller 266 109. Templets for Securing a Desired Form in a Wooden Propeller. . . 271 110. Four Cylinder Motor of Wright Biplane 273 111. Pump-Fed Antoinette Engine 273 112. Three-Cylinder, 22-Horsepower Anzani Engine 276 113. Four-Cylinder "Double-Twin" Anzani Motor 278 114. Renault Eight-Cylinder V-Shaped Motor 278 115. Fiat and Panhard Aeronautical Motors 280 116. Darracq and Dutheil-Chalmers Aeronautical Motors 280 117. Diagram of Revolving-Cylinder Motor 283 118. Gnome Revolving-Cylinder Motor 284 119. Ten-Cylinder Motor with Concentric Exhaust and Inlet Valves 276 120. Magnetic Plug 285 121. Make-and-Break Ignition 285 122. Mechanical-Break Jump-Spark Ignition System 286 123. Jump-Spark Ignition , 286 124. Hot-Tube Ignition -. 287 125. Fuel-Injection Aeronautical Engine 290 126. Carbureter 292 127. Mietz and Weiss Fuel Pump 295 128. Silencer 296 129. Muffler 296 130. Steam Engine For Aeronautical Use 300 131. Flue Boiler 302 132. Water-Tube Boiler for Aeronautical Use 300 133. Aeroplane Power-Transmission System 313 134. Aeroplane Power-Transmission System 313 135. Aeroplane Power-Transmission System 313 136. Aeroplane Power-Transmission System 313 137. Block Chain 316 138. Roller Chain 317 139. Chain Transmission of Wright Biplane 313 140. Chain Transmission in Hydroplane, Driven by Aerial Propellers . . . 313 141. Belt Transmission in Recent Santos-Dumont Monoplane 316 142. Voisin Biplane Modified into a Triplane 327 343. Henry Farman's Biplane in Flight 327 144. Adjustable Ball Bearing 329 145. Annular Ball Bearing 330 146. Full Type Annular Ball Bearing 332 147. Annular Ball Bearing 332 148. Annular Ball Bearing 333 LIST OF ILLUSTRATIONS 19 FIGURE. PAGE. 150. Ball Thrust Bearing 334 151. Resultants of Load on Ball Bearing 335 152. Cylindrical Roller Bearing 340 153. Flexible Roller Bearing 341 154. Projected Area of Plain Bearing 345 155. Adjustment of Plain Bearing 346 149. Annular Ball Bearing Subjected to Thrust 333 156. Cone Bearing 346 157. Bleriot XI. in Flight 347 158. Bleriot XII. in Flight 347 159. Ring oiler on Crankshaft 349 160. Force-Feed Lubricator 351 161. Wright Biplane Starting and in Flight 348 162. Koechlin Monoplane in Flight 350 163. Wright Machine on Starting Rail 350 164. Bleriot Alighting Gear 350 165. Wright Starting System 358 166. Wright Machine and Starting Derrick 360 167. Starting by Rope Attached to Stake and Wound in on Drum.... 364 168. Rougier's Voisin Rising from Starting Ground 360 169. Bleriot Starting Device 368 170. Typical Alighting Gear 370 171. Details of Bleriot Monoplane 372 172. Alighting Gear of Paulhan's Voisin 372 174. Alighting Gear of Farman Machine 374 175. Boat-Like Body of Antoinette Monoplane 374 176. Alighting Gear of Antoinette Monoplane 374 177. Built-Up Bamboo Spar 376 178. Sections of Wooden Spars 380 179. Built-Up Hollow Wooden Spar 381 180. Built-Up Bamboo, Hickory, and Rawhide Wing Bar 381 181. Methods of Fastening Wire Ends 386 182. Strut Sockets and Turnbuckles 387 183. Wire Tightener 387 184. Texture of Modern Aeroplane Fabrics 372 185. Scale Drawings of Wright Biplane 392 186. Side View of Wright Machine 394 187. Three-Quarters View of Wright Machine 394 188. Rear View of Wright Machine 398 189. Paul Tissandier Seated in Wright Biplane 400 190. Count de Lambert in Wright Biplane 400 19 1 Wilbur Wright Instructing a Pupil 400 .,02 Details of Wright Strut Connections 402 ., 03* gi e view of Wright Runner Construction 402 194* Wright Runner and Rib Details 402 195] Rudder Frame of Wright Machine 404 196. Elevator Frame of Wright Machine 404 197. Scale Drawings of Bleriot Monoplane Number XI 406 198. Bleriot Monoplane Number XII 408 199. Bleriot Monoplane Number XI 408 200. Front View of Bleriot XI 408 201. Three-Quarters View of Bleriot XI 408 202. Scale Drawings of Cody Biplane 412 203. Latest Model of Voisin Biplane 414 204. Three-Quarters Rear View of Voisin Biplane 414 205. Three-Quarters Front View of Voisin Biplane 414 206. Scale Drawings of Farman Biplane 416 207. Side View of Farman Biplane 418 208. Three-Quarters View of Farman Biplane 418 209. Maurice Farman's Biplane 420 210. Front View of Maurice Farman's Biplane 420 211. Farman's Modified Voisin 420 212. Scale Drawings of Antoinette Monoplane 397 213. Three-Quarters View of Antoinette III 424 214. Rear View of Antoinette V 424 215. Front View of Antoinette VII 424 216. Rear View of Antoinette VII 426 217. Side View of Santos-Dumont's Belt-Driven Monoplane 426 218. Front View of Santos-Dumont's Belt-Driven Monoplane 426 20 VEHICLES OF THE AIR FIGURE. PAGE. 219. Side View of Santos-Dumont's Demoiselle 424 220. Front View of Santos-Dumont's Demoiselle 426 221. Scale Drawings of Santos-Dumont Monoplane 428 222. Side View of R. E. P. Monoplane 430 223. Three-Quarters View of R. E. P. Monoplane 430 224. Captain Ferber's Dihedral Biplane 430 225. Scale Drawings of Montgomery Glider 432 226. Front View of Montgomery Monoplane Glider 434 227. View from Beneath of Montgomery Double Monoplane 434 228. Scale Drawings of Curtiss Biplane 401 229. Side View of Latest Curtiss Biplane 436 230. Early Lilienthal Monoplane Glider 405 231. Lilienthal Monoplane Glider 405 232. Lilienthal's Biplane 405 233. Pilcher Glider 407 234. Pilcher Glider 408 235. Maxim Multiplane 406 236. Maxim Multiplane 406 237. Chanute Biplane Glider. 398 238. Santos-Dumont's Demoiselle in Flight 410 239. Paulhan's Voisin in the Douai-to-Arras Flight 410 240. Suggested Nernst Lamp 413 241. Lens Mirror 418 242. Locomotive Headlight 419 243. Anemometer Speed and Distance Recorder 421 244. Universal Level 426 245. Side View of Bleriot XI. with Wings Tied on Frame ... 427 246. Front View Bleriot XL, Showing Demountable Wings 427 247. Assembling Bleriot XI 427 248. Wicker Chair and Foot Control of Ailerons in Farman Biplane 440 249. Cockpit of Bleriot Monoplane Number XI 440 250. Seating Arrangement and Control System of Antoinette Monoplane 448 251. Sling Seat of Captain Ferber's Biplane 448 252. Cockpit and General Details of R. E. P. Monoplane 450 253. Latham's Antoinette Monoplane in the English Channel 450 254. Latham Heading off the Cliffs at Sangatte 452 255. Suggested Use of Exhaust Gases to Heat Foot Warmer 441 256. Parachute 442 257. Effect of Height Upon Choice of Landing 447 258. United States Weather Signals 450 259. Wright Patent Drawings 453 260. Montgomery Patent Drawings 459 261. Chanute Patent Drawing 462 262. Mouillard Patent Drawing 463 263. Lilienthal Patent Drawing 464 264. Diagrammatic Comparisons of Modern Aeroplanes 473 265. Flights over English Channel 474 266. Farman Flights, Chalons to Rheims, and Chalons to Sulppes 474 267. Bleriot Flights, Toury to Artenay, and Etampes to Orleans 474 268. Cody's 40-Mile Cross-Country Flight in England 475 269. Count de Lambert's Flight over Paris 475 270. Map Showing Principal Zeppelin Flights 475 " * * * the heavens fill with commerce, argosies of magic sails, Pilots of the purple twilight, dropping flown with costly bales." TENNYSON. INTRODUCTION To the preparation of this work, the author has been influenced largely by the lack of any concrete and popular treatise on aerial navigation. With the ob;iect of remed y in S this condition in at least some degree it has been sought to produce an adequate, up-to-date, and at the same time a comprehensive presentation of what is fast becoming one of the most important and alluring fields of modern engineering. In the accom- plishment of this purpose it has seemed desirable to plan a volume that should appeal to general curiosity as well as to particular interest. This is because the subject is so new that very few can lay any claim to its mastery, though thousands are commencing its study. These conceptions of the need, and of the sort of interest to be met by a book of this character, have dictated the inclusion not only of timely and authori- tative data concerning contemporary successes, but also of some material that is chiefly historical often the history of now discredited mechanisms as a help in easily and clearly conveying to the casual reader a logical idea of just what progress has been made and is making in the modern science of aeronautics. It even has appeared reasonable to venture occasional suggestions of the future forecasts intended simply 21 22 VEHICLES OF THE AIR to stimulate still doubtful imaginations rather than to invalidate themselves by too-complicated or far-fetched premises. Yet in such prophecies it will be readily appreciated by the technically versed that the prophet is sufficiently safe if he don his robe without too reck- less a disregard of his limitations, and confine himself to impressing upon the general attention only such facts as are already evident and obvious to the few specialists who are closely in touch with their subject. Necessarily some portion of the matter herein pre- sented is in a way the product of compilation. It being the province of the writer at a task of this sort to record rather than to create, it is not to be expected that much more can be accomplished than a discrimi- nating and consistent addition of new material to old, with the two arranged and related in an orderly and informing manner. No more than this has been attempted ; if no less has been accomplished the author will feel well satisfied. The publishers join with the author in the hope that this book may help to stimulate the English- speaking races into some parallel with foreign enthu- siasm in aeronautics. For it seems as true as it is regrettable that the nations that developed the Wright brothers, Montgomery, Chanute, Langley, Herring, Pilcher, Stringfellow, Wenham, Hargrave, Henson, Maxim, McCurdy, Curtiss, and others, and which once were found always in the van of the world 's progress in science and invention, are replacing their one-time zeal for promising innovations and scorn of hampering precedents with an imitative and trailing commer- cialism, of which there already has been at least one other sufficient example. Certainly it is an inescapable fact that the less tradition-trammeled engineers of INTRODUCTION 23 continental Europe are the first to perceive the begin- nings of the practical and commercial era in aero- nautics, just as they were the first to perceive it in the case of the automobile. And equally is it a fact that the United States and the British governments, and American and English capitalists, continue con- spicuously tardy in their recognition of the newest and least-limited advance in the history of transportation. Nothing but the utmost blindness to existing achievements can continue to belittle what it cannot SKEPTICISM comprehend. Aerial navigation today is IGNORANCE is no more a joke than was the railway eighty years ago, or the steamship seventy years ago, or the automobile ten years ago. On the contrary, it is already the basis of a vast and progressing industry, founding itself surely on the most advanced discoveries of exact science and the finest deductions of trained minds, and possessed of a future that in its sociological as well as in its engi- neering aspects sooner or later must stir the imagina- tions of the dullest skeptics. Inevitably it is a matter of perhaps no more than a few months certainly of no more than a few years after this is written when in every country of the world the flying machine will enter upon an epoch of wide development and appli- cation, the far-reaching reactions of which are certain to carry significances of the profoundest import to every phase of civilization and every activity of the race. Man's movements about the planet he inhabits are 24 VEHICLES OF THE AIR restricted to a maximum of the three traversable media with which he can come in physical contact. He can THREE travel by land, by water and by TEAVEBSABLE air. Of the difficulties of these, he first MEDIA overcame the simplest, as was to have been expected; he next fell to devising one kind and another of water craft, and progressed to navigation of the seas; and now, after centuries of ineffective struggle, he is beginning to apply the hard-won les- sons of his slowly-accumulated knowledge to the con- quest of the air. Of the three media, the air alone exists over the earth's entire surface, thus demanding for its utilization neither specially-constructed high- ways nor restriction of journeys such as limit or make costly all efficient transportation on land and water. And, more than all this, there are unknowable forces greater than the mere opinions and activities of men, so it is only consistent with experience of human progress and observation of the eternal logic of things to recognize that sooner or later mankind must conquer this last highway of the world, thus finally asserting the dominion over all things terrestrial that is declared his right by the scriptures. Concerning the types of machines that will survive, as most successfully applicable to practical and com- mercial navigation of the air, present knowledge is distinctly informing. It seems rather clearly indicated, for example, that the "lighter-than-air" type, the balloon, can have little future beyond such as is too often founded upon the activities of ignorant inventors or unscrupulous promoters, or upon the thrills it undoubtedly affords as a Gargantuan spectacle. As is hereinafter suggested the balloon is an evasion rather INTRODUCTION 25 than a solution of the real problem of aerial naviga- tion. It floats in the air rather than navigates it, and so is no more a flying machine than a cork in the sea is an ocean liner.* The helicopter is the type of "heavier-than-air" machine designed to ascend by the action of one or more lifting propellers, rotating on vertical axes. This type must for the time be dismissed as without present status to condemn or approve it. It is enough to say that more than one engineer of unquestioned eminence has faith in it, while there are others of equal standing who as positively disapprove. The term ornithopter is given to any type of heavier-than-air machine in which there is attempted imitation of nature's wing motions. The matter of its merit comes down chiefly to the simple question of whether or not a reciprocating-wing system can be made superior in reliability and efficiency to the rotating-wing system that constitutes a propeller. Probably no engineer of practical abilities will con- tend that it can. It is a common argument that birds, which may be considered the flying machines par excellence, fly on this plan. True enough, but it is equally true that most animals walk on legs and most fishes swim with tails and fins, despite which man finds that with wheels and screw propellers he can secure results vastly superior to any that are to be found in attempts to copy nature's mechanisms more closely. It is a point deserving of regard in * It being a fact, however, that the dirigible balloon exists, and that its problems are enlisting the activities of able engineers and powerful governments, for these reasons it will herein in all fairness be accorded such attention as seems demanded by its present prominence rathe* than by its future prospects. 26 VEHICLES OF THE AIR this connection that the real reason the continuous rotating mechanism is unknown in the animal economy may be the most excellent one that it is not available. A wheel or any similar continuous-rotating element in a machine involves a complete separation of parts, mere contact or juxtaposition being substituted for the complete structural continuity that is rendered impera- tive in the natural machine by nature's self-contained processes of manufacture, growth, and repair proc- esses with which man's mechanisms are not handi- capped, however imperfect they may be in other respects. The aeroplane is far and away the most promising of the several types of machines in so far as any AEROPLANE present vision can discern. This type MOST of air craft is sustained by the reac- SUCCESSFUI* tions of the air rotations and streams under and adjacent to its inclined curved surfaces, and in nature finds its analogy in the soaring bird, and particularly in certain insects. Ordinarily, to fly an aeroplane must keep moving, wherefore it must attain lateral speed before it can rise and must retard to a stop in alighting. Without exception all the suc- cesses recently achieved in the United States and abroad have been with curved-wing* aeroplanes. The questions of speed and flying radius are still some way from any sort of settlement. Certainly the speeds ultimately attained will be very high, but, what is more to the point, they will be easily maintained. In this regard aerial navigation is comparable with * The modern substitution of curved surfaces for the flat ones of earlier experiments has made the term "aeroplane" a misnomer, but it seems nevertheless to have fixed itself ineradicably upon the language. and so may as well be accepted. INTRODUCTION 27 travel on water rather than with travel on land, maximum speeds being also average speeds in the case steamsm P> though this is not SPEED AND RADIUS ^ e case w ^k l an( * locomotion. In addition to its other advantages, high speed of aerial travel may prove the soundest engineering because it admits of sustaining the heaviest loads upon the smallest surfaces. Another and imperative reason for speed will be to overcome adverse winds. To progress against wind, speed higher than the highest speed in which flying is to be attempted may be required. The limit of wind velocity with which it may prove possible to battle will be determined mainly by conditions of starting and landing. As for the possible radii of action the maximum distances of travel without return to a base or descent to the earth for additional supplies of fuels, lubricants, etc. it is evident first of all that the greater the radius the greater the utility. Indeed, the ability to combat long-continued adverse winds, appli- cation to polar and other exploration, transoceanic travel, and sustained rapid transit overland may hinge directly upon capacity to accomplish great dis- tances on minimums of supplies and fuel. The sizes of the machines that will be built is another matter for the future to determine. It being a law of geometry that the areas of structures increase with the squares of their linear dimensions, while bulks and weights increase with the cubes, it is evident that at some point the gain of the weights over the areas will impose a limit that cannot be passed. Against this, however, is the likelihood that there may not be much use for large craft. Traffic experts agree 28 VEHICLES OF THE AIR that the secret of all rapid transit is the maintenance of speed, it being the slowings down and the stops that chiefly account for the slow average AEROPLANES s P ee d s on l anc * despite the wonder- ful spurts that have been made by land vehicles for short distances. More than this, the existence of the expensive large-unit vehicle on land is mainly due to the necessity for highly-specialized, prepared highways, while on water it has been found an essential means to high speeds and maximum safety. In the air conditions will be different. Here the inexpensive and ideal small-unit vehicle, suggested in some degree by the automobile, and likewise eman- cipating its user from other persons' routes, stops, and time schedules, will find an unlimited field for development. Moreover, such development will pro- gres under the stimulus of lower first and maintenance cost than apply to any other system of travel*. Flying machines will be inexpensive to build because their construction calls for little use of FIRST AND complex forms in resistant metals. OPERATING Wood, wire, and fabric, of common qualities and at low cost, are almost the extent of what is necessary, barring the question of motors, which will be cheaply manufactured in quantities, to standardized designs. And even more vital than mere low cost of manufacture will be the fact that manufacture will not require the facilities of costly factories, but can be undertaken by any one possessed of the requisite data and an ordinary sort of carpentering ability. That flying machines will be inexpensive to operate must reasonably follow from the small power needed for their propulsion and from the fact that they have INTRODUCTION 29 no working parts in constant destructive contact with a roadway. Indeed, the transition from the expedient of confining air in automobile tires to the utilization of the unconfined air of the atmosphere as a vehicle support is rather definitely an advance from a lower to a higher order of engineering. Nor are these questions of cost in any sense the least important factors in the future of aerial naviga- tion. Modern engineering abounds in examples of things that are possible but not profitable. Indeed, it is just this point, that limited utilities do not warrant unlim- ited expenditures, that so utterly condemns the dirig- ible balloon. With flying machines, sufficing for the safe, inexpensive, and rapid conveyance of one or two persons, cheaper to build than a modern motorcycle, there enter prospects that must ultimately loom larger on the horizon of transportation and the whole struc- ture of modern society than even so great a prospect as the actual accomplishment of aerial navigation itself. Laws, customs, and conventions must fall in the tremendous readjustments that will ensue. Many forms of social trespass will have to be fought by removal of incentives rather than by attempts at pun- ishment, and there will be discovered innumerable outlets for various movements for race improvement, which the iron inflexibility of present-day environment keeps suppressed and silent. Questions of safety are ever uppermost in most persons' contemplations of aerial travel. To the average individual let there be said THE PHYSICAL flying mac hi ne and at once his brain must visualize some horrifying con- ception of an unstable craft of vague outlines and 30 VEHICLES OF THE AIR terrible hazards, precariously poised in the cloudland at an illimitable height above terra firma. How dis- tinctly such ideas are at variance with the facts has been shown by the Wright brothers, Farman, Bleriot, and others, in flying for mile after mile only four or five feet from the ground.* People are prone to appraise casualty by its horror rather than by its statistics, and the thought of one individual tumbling from the skies grips harder on the popular imagination than the slaughter of a few scores in a railway accident or the drowning of a few hundreds in a shipwreck. As a matter of fact, there are many more factors of safety in present and pros- pective aerial travel than at first appear, even to the well-informed. Besides the proved practicability of close-to-the-ground flight, there is in the case of the aeroplane the complete stability of the type as a glider.f This means that the immediate safety at any moment is not contingent upon the operation of a more-or-less complicated motor, the continued func- tioning of which is dependent upon the unfailing operation of an interconnected aggregation of parts rapidly revolving or reciprocating under heavy stresses. On the contrary, a motor is necessary, if * In teaching Captain Lucas Gerardville of the French army to operate the Wright flyer, Wilbur Wright required the control of the levers to be returned to him whenever the machine \vas steered lower than two meters (6% feet) or higher than four meters (13 feet) from the ground, thus indicating that he considered inability to keep within this zone, even for a beginner, as definitely incompetent driving as would be steering out of the road with an automobile. Such close-to- the-ground flight is particularly well shown in the photographs repro- duced in Figure 161. t The Wright machine was first developed as a glider without a motor, and in its later motor-propelled models has been on more than INTRODUCTION 31 at all, only to maintain continued upward or hori- zontal travel, the ability to soar reliably at a flat angle down a slant of air being contingent only upon the continued structural integrity of non-moving ele- ments, or at worst, of elements readily made very strong or even provided in duplicate, and demanding only moderate and occasional control adjustment against very light stresses. As a consequence, the only risk likely to continue ever-present is that of such derangement or the encountering of such adverse weather conditions as may compel landing upon unfavorable areas without immediate but with the prospect of ultimate disaster. Thus, to be compelled by engine failure or adverse weather to descend in a desert or forest, or on rough mountains, would result in a situation fairly comparable to that of a wrecked vessel, or of a 'derailed train, or of a ditched auto- mobile, rather than in one ascribable to any undue and inherent hazard pertaining to the new conveyance regardless of the conditions of its use. These differ- ent considerations will, however, doubtless produce definite effects on the progress that will be made. And, as progress continues and engineering resource one occasion driven to considerable altitudes, the engine stopped pur- posely or inadvertently, and a safe soaring descent to the ground ac- complished. The Montgomery machine, built primarily as a glider, can be dropped upside down in the air, even with loads, and such is its automatic stability that it invariably rights itself and comes to the ground as gently as a parachute. The Antoinette, Bleriot, Voisin, Curtiss, E. E. P. and many other successful flyers likewise have proved safe gliders with engines stopped. Particularly significant in this con- nection were Latham's two descents, enforced by engine failure, into the waters of the English Channel once without even wetting his feet I A similar experience, showing that engine failure does not necessarily mean serious disaster, was C. F. Willard's descent upon Lake Ontario, on September 3, 1909. 32 VEHICLES OF THE AIR makes of the trackless air an unrestricted highway of ever-increasing stability, those of the sky pilots whose temerity is greatest may be expected to become more and more venturesome and capable, so that the development of the flying machine, from commencing with cautious flights in favorable weather, at moderate speeds and low altitudes, and over surfaces upon which landing is comparatively safe, must in time pro- gress to exceedingly rapid travel at somewhat greater heights, and with less regard to the state of the weather or to the character of the surface beneath. Aerial navigation offers little prospect of ever becoming safe to the extent of relieving those who take it from the common chances of DANGERS IN jif e an( j d eatn , but it does most L TRAVEL emphatically promise that its hazards per passenger carried a given distance will not exceed the corresponding hazards of terrestrial and aquatic transportation. The railroads of the United Stales alone exact an annual toll of 12,000 persons killed and 72,000 injured, yet many very timid individuals think nothing of riding for hours at a time, at speeds of forty, sixty, and eighty miles an hour, along the tops of precipitous embankments and over unguarded bridges and trestles, with their safety never for a moment independent of the somewhat precarious hold of thin wheel flanges on the smooth edges of narrow rails. Thus does familiarity breed contempt. Never- theless, compelled to a choice between being plunged to the ground through a distance of, say, fifteen feet in a light, elastic, and protecting structure of wood, wire, and fabric, against the proposition of rolling a similar distance down an embankment, surrounded by INTRODUCTION 33 the crushing mass of a railway coach, what sane indi- vidual would prefer the hazards of the latter? As progress continues and safety becomes more and more assured under conservative and reasonable conditions, the timid will in increasing num ^ ers venture first trips as pas- sengers and be reassured by their experiences, until the time will arrive when to fear to travel by air will be to class one with the people who today are afraid to dare the risks of rail and water travel. A gradual overcoming of the inertia of the mind appears to be an essential process in reconciling the generality of people to innovations. Even in the cases of many institutions of the longest standing there are persistent inconsistencies in many people's attitudes. For example, the automobile, which com- pared "passenger-mile" against "passenger-mile" is found responsible for far fewer accidents than regu- larly attend the use of horses, still is regarded as a 'sort of death-dealing juggernaut by many normally sensible persons. Likewise, it is commonplace to find people thoroughly hardened to travel by the most dan- gerous type of rail vehicle, the street car, who cannot restrain a feeling of terror at the thought of travel by steamship, which is statistically provable to be any number of times safer. At the time this is written the power-driven heavier-than-air flyer has been respon- sible for the death of only three individuals in the whole world, despite an aggregate of experimental flights totalling fully 35,000 miles. Undoubtedly the first commercial applications of aerial vehicles will be to classes of service involving minima of human risk with maxima of utility serv- ices such as the conveyance at high speed of special 34 VEHICLES OF THE AIR classes of mail and express matter by aeroplanes, each requiring for its management only a single operator, or the rapid distribution of news- COMMEECIAL paper matrices and illustrations under APPLICATIONS ., -I-,- -XT similar conditions. Next may come the daring spirits who will take desperate chances in the exploration and prospecting of remote and unset- tled regions not to consider the red-blooded few who from the beginning find in navigation of the air a new means of reckless sport and dangerous recreation, chiefly interesting in the improvements that result from their successes and the lessons that are gleaned from their mishaps. To any one who has kept abreast of recent progress it is genuinely amazing that there are still so many who question this matter of commercial applica- tions. Many who even concede that the flying machine may find important application in warfare and meet with considerable success in sport, still are disposed to deny that it ever can find extensive use as a common- place, every-day means of transportation. Such per- sons mistake the bounds of their own knowledge for defects in the thing examined, and see in every failure of an experimental mechanism, no matter to what cause due, a conclusive condemnation of a whole propo- sition, and when they find themselves astute enough to glimpse a limitation, no matter how trifling, its sub- traction from the original quality clearly leaves a remainder of zero. Yet an inability to fly at all through not knowing how is a distinctly different thing from a mere cessation of flight from break- down. The first leaves mankind as positively unable to travel in the air as to travel to Mars. The second is with perfect reasonableness comparable with such INTRODUCTION 35 negative disabilities as broken flanges, punctured tires, leaking hulls, and the like, which similarly may termi- nate particular trips by particular means in delay and even in death. As for limitations, it certainly is to be admitted, for example, that the aeroplane appears totally unsuited for urban travel. In its Z I n J^j ^ S present most successful forms it re- EAFECTED . . quires special devices or, at least, con- siderable clear and unobstructed areas for starting and alighting. But for interurban travel, on the other hand, these limitations fail to constitute objections of material magnitude. There is no more reason for expecting the aeroplane to find its utility by developing a facility in maneuvering through mazes of wires and alighting amid street traffic than there would be for condemning Atlantic liners because they have to dock at Hoboken instead of sailing up Broadway. Undoubt- edly the time will come when it will be considered quite as reasonable that the beginnings and endings of aerial voyages should involve the presence of special launching and landing facilities, as it is that railway trains should travel from station to station. No type of transportation is unlimitedly flexible. Bail vehicles are confined to rails, automobiles must keep to roads or good surfaces, water craft cannot leave the water, bicycles require at least a fair path, and not even beasts of burden and men walking can disregard all topographical difficulties. Against these, surely the ability of the air vehicle to progress in an air line at its high and maintained speed from selected start to selected destination, always regardless of what may be beneath, and ever ready should necessity compel to settle under control and without immediate danger 36 VEHICLES OF THE AIR upon any fair area of unencumbered land or water space, may be regarded as a form of flexibility suffi- ciently valuable to offset the lack of other sorts. Moreover, there is some reason for expecting that small aeroplanes and helicopters may arrive ultimately at such reliability and perfection of control that it will be feasible to direct them from or upon almost any place that affords space to accommodate them. Particularly interesting is the relation of aerial navigation to war it appearing more than probable that this latest of man's inventions RELATION w ^j serve fi rs t in adding to the ter- TO WAEFAEE. -. ,, . ,, n . ,, , , . rors of and then in the laying of this grim specter of the centuries. For aside from all mere tactical questions of airships versus battleships it is most of all to be considered, as a very few mili- tary authorities have pointed out, that in the develop- ment of the flying machine there is placed for the first time in history, in the hands of weak and strong com- batants alike, a weapon capable of as effective and unpreventable direction against the kings, congresses, presidents, and diplomats who declare war as it is of direction against the fighting men on the faraway battlefronts. Already more than one great military and naval captain has suffered disquieting visions of what will happen when, maneuvering unopposed and unseen in the obscurity of the night, not merely one or a few, but veritable swarms of light aeroplanes, in twenty- thousand lots costing no more than single dreadnoughts, commence trailing assortments of high explosives at the ends of thousand-foot lengths of piano wire, over cities and palaces and through fleets and armies. Many authorities are inclined to disparage the INTRODUCTION 37 fighting utility of the aeroplane, basing their views on the fact that it has been demonstrated exceedingly difficult to drop bombs with any considerable accuracy from great heights. But from a slow-moving aero- plane flying very low it should be an easy matter to cast generous parcels of picric acid or fulminate of mercury into the twenty-foot diameters of a battle- ship's funnels. The answer that such an attempt might be foiled by the use of searchlights and quick- firing guns is one that contemplates attack by only one or two of the air craft, rather than to the con- certed descent of a whole host of such emissaries of destruction, each manned by a competent and deter- mined crew, realizing that if only one of the wasp-like swarm achieves its purpose the picking off of a few by lucky shots or extraordinary gunnery will be fear- fully avenged. Fancy for a moment the disillusionment to come when in some great conflict of the future a splendid up-to-date battleship fleet of the traditional order, with traditional sailors, traditional admiral, and traditional tactics, finds itself beset in midseas by a couple of great, unarmored, liner-like hulls, engined to admit of speeds and steaming radii such as will permit them $ to .pursue or run away from any IMAGINATIVE armored craft yet built, and designed SPECTACLE with dear and leyel deckg for aeroplane launching. Conceive them provided with storage room for hundreds of demountable aeroplanes, with fuel, repair facilities, and explosives, and with housing for a regiment or two of expert air navi- gators. Then picture the terribly one-sided engage- ment that will ensue the thousands of tons and millions of dollars' worth of cunningly-fashioned 38 VEHICLES OF THE AIR mechanism all but impotent against the unremitted, harrying, and reinforced attacks from aloft, and unable either to escape from or give chase to the enemy's floating bases of supplies, which, ever warned and convoyed by their aerial supports, will unreach- ably maneuver out of gun range, picking up from the water, reprovisioning, remanning, launching and relaunching their winged messengers of death until the cold waters close over the costly armada of some nation that has refused to profit by the lessons of progress. The question of aerial travel over water is one of particular significances. Water areas, in common with the atmosphere, possess a quality OVER WATER ^ a ^ ^ oes no ^ pertain to land the quality of uniformity. The conse- quence is that just so soon as means are devised for launching aeroplanes over water, by the use of hydro- plane under surfaces, boat convoys (as suggested in the preceding paragraph), or any other serviceable expedient, the way is at once opened to the establish- ment of transaquatic mail lines utilizing craft pro- vided with hull-like floats and made capable of flying with almost perfect safety just above the wave crests. Indeed, it is quite to be anticipated that the institu- tion of some such service may constitute the first serious commercial exploitation of the aeroplane. A special incentive to experiment in this direction is the low speed of even the fastest present water travel, by contrast affording to the flying machine an advan- tage that it does not yet possess in comparison with the higher speeds of land travel. The still unsettled ques- tions of flying radius and motor reliability can be at the outset tentatively evaded by establishing the firsf INTRODUCTION 39 services over the shorter distances, or by stationing patrol boats with fuel supplies at necessary intervals. It is an irresistible conclusion that the practical utility of the flying machine is no longer to be CONCLUSION doubted - The onl y questions are those of the exact methods of realiz- ing these utilities, and the extent of their applica- tion when realized. People begin to see that it is absurd to characterize as impossible what has been long accomplished. The bird flies, and there is nothing occult about either the mechanism of the bird or the laws of its operation. Not even the soaring feats of the bird violate any of the laws of aerody- namics or the law of the conservation of energy, how- ever they may scandalize some pedantic conceptions of these laws. Difficulties are no greater than the knowledge required to surmount them, and knowledge is accumulating hour by hour. The time is arriving when it will be no more difficult to maneuver a flying machine than it is to ride a bicycle. Both are dis- tinctly mechanical inventions, both tend unfailingly to develop from inferior to superior forms, and both have had to encounter various skepticisms. Here to digress for a moment let the doubter just consider this case of the bicycle, less as an analogy in mechanism than an analogy in mental attitudes. Think of a "trained engineer" or "conservative business man" of a few years ago confronted with a modern "safety", exhibited with the assertion that here was a vehicle of perfectly practical utilities, inexpensive to build and operate, capable of considerable speeds under an ordinarily vigorous rider, and perfectly suit- able for the use of old people and children under ordi- nary traffic conditions. Fancy the derision the criti- 40 VEHICLES OF TEE AIR cism that would be leveled at the pneumatic tires, the strictures that would be visited upon the light construc- tion, and, above all, the ridicule that would be heaped upon the proposition of requiring from ordinary people the balancing instict of the acrobat then, perhaps, some appreciation will be had of the way most present- day opinions on aeronautics will fit conditions five years from now. And if all this insistence brings the reader to some belief that possibly, after all, this epic development in transportation is upon us, what of the changes it must involve the far-reaching influences it must inevitably exert in all possible fields of human thought and activity? Ponder the romance of it the certainty that it must completely reorganize more than one fun- damental factor of the present social order. And believe as one must unless lost to all optimism and faith that even -present ills work for ultimate good, and inquire what it will mean to live under skies thronged with aerial fleets, to live in a world from which the artificial barriers of national boundaries and the natural barriers of physical characteristics are by advancing intelligence erased past re-establishment. What must be the result when, with a means of travel limited neither by difficulties of topography nor by the shores of the seas, lending itself perfectly to individual use but not at all to the uses of monopoly, and not confined to the narrownesses of specially built highways, the greatest freedom the individual can possess the freedom of travel far and wide at will is vastly enhanced by the vehicles of the skies, vehicles that will prove cheaper to own, maintain, and operate than any other vehicles that have ever existed ! Travel on land will be reduced to the extent that it INTRODUCTION 41 is slow, inefficient, expensive, and inflexible. Travel on water will become a mere adjunct to that of the air. The world will be narrowed by the speeds attained. Tariff and exclusion laws will be annulled through the sheer impossibility of their enforcement. And the skies will be as thronged with the craft of man's devis- ing as they are today with the fowl of the air. Throughout the territories of every nation of the earth there will appear the leveled, circular, landing areas, perhaps provided with strange-appearing start- ing devices and probably bordered with low, capacious, shed-like housings. Automobiles will be at hand to afford rapid transportation to the business centers of adjoining communities. There will develop a technique and a language of aerial navigation, and experts will become skilled in contending with the perversity of special mechanisms, in starting and landing under difficult circumstances, in battling with fog and rain and storm, in taking advantage of air currents at different levels, and in seeking out the lanes of the atmosphere in which to add to their speed the sweep of the trade winds. And over all will soar with the ease of the gull or drive with the speed of the whirlwind, the myriad ships of the air, transforming the face of the heavens. Of many sizes and at many altitudes, midgets and levi- athans, close to the earth and up in the clouds in the days the shadows of their wings will speed over every corner of all the lands and seas, and in the nights of that future time the eye-like gleams of their search- lights will mingle to the uttermost ends of the earth, beacons of science and romance and progress and brotherhood VlCTOR LouGHEED . CHICAGO, November, 1909. a > CHAPTEE ONE THE ATMOSPHERE At least a brief consideration of the properties and phenomena of the atmosphere, as the medium through which all aerial vehicles must travel and from which they must derive their support, has a logical place in a work of this character. EXTENT The extent of the gaseous envelope that sur- rounds the earth is a subject that has been much investigated by physicists. Knowing the weight of the air, the area of the earth's surface, and the approximate mass of the earth, it is not especially difficult to compute the total weight of the atmos- phere, which is found to be about y.inrJ.Tnnr that of the rest of the earth. Determination of the height of the atmosphere is a more difficult problem, whether it be attempted by purely mathematical methods or reasoned more or less empirically from such observations as are available. Were the air of uniform density from the earth's surface to its limit of height it can be easily demonstrated that this upper limit (termed by scientists the "height of the homogeneous at- mosphere") would be at an altitude of about 26,166 feet lower than the highest mountain tops but 43 44 VEHICLES OF THE AIR since the air decreases in density at an increasing ratio as the pressure due to air above grows less with each increase in height, until the atmosphere attenuates by imperceptible graduations into a perfect vacuum, no known calculated solution of its ultimate height can be closely depended upon. The greatest heights above sea level to which man has actually ascended in the atmosphere have been reached with balloons, Glaisher and Coxwell (see Page 74) having attained a probable height of 29,520 feet, while Berson and Sirring (see Page 75) undoubtedly reached an altitude of 35,400 feet. The atmosphere has been explored to much greater heights by " sounding balloons" (see Page 75), the greatest height on record having been reached by a balloon of this type released from Uccle, Belgium, on November 5, 1908. As shown by self-registering instruments attached to this balloon, it rose to a height of 29,040 meters (95,275 feet), over eighteen miles. Estimates based on the calculated heights of meteors at the times when they commence to be- come luminous from friction with the earth's at- mosphere have been held to indicate that this must extend, in an exceedingly tenuous state, to a height of 200 miles. Other authorities contend that the extreme upper limit cannot be over 100 miles high. In any case, it is an obvious deduction from the barometric pressures recorded at great heights (see Page 56) that | of the whole atmosphere is below 30,000 feet, T V below 43,000 feet, and below 95,275 feet. THE ATMOSPHERE 45 PROPERTIES AND CHARACTERISTICS The atmosphere being chiefly composed of sev- eral common forms of matter, its principal phys- ical properties and characteristics have been well investigated. WEIGHT According to Kegnault, air at sea level, freed absolutely from water vapor, carbon dioxid, and ammonia, weighs .0012932 grams to the cubic cen- timeter at zero Centigrade, under a pressure of 760 millimeters of mercury in the latitude of Paris (48 50' N.), and at a height of 60 meters above sea level. In English equivalents this is approxi- mately equal to .080681 pound to the cubic foot or 12.384 cubic feet to the pound at sea level in the latitude of Washington, D. C. Ordinarily, not freed from water vapor and other impurities, air at sea level, at 32 F., can be taken to weigh very close to .080728 pound to the cubic foot. At any height above sea level a given volume of the atmosphere weighs an amount less than a similar volume at sea level, in exact proportion to the difference in barometric pressure, other con- ditions being equal. Thus, at the 29,000 feet reached in the Coxwell and Grlaisher balloon ascent the weight of the air was only .052171 pound to the cubic foot. The weight of the air is an important consid- eration in the design of aerial vehicles, particu- larly in the case of lighter-than-air constructions, 46 VEHICLES OF THE AIR since these are enabled to float only by being lighter than the volume of air they displace. With heavier-than-air machines the weight of the appa- ratus is sustained by the quantity of air acted upon, varying with area of surfaces, rapidity of the action, and mass of the air affected. COMPOSITION Air consists chiefly of oxygen and nitrogen mechanically admixed (not chemically combined) in the proportion of about 21 volumes of oxygen to 79 volumes of nitrogen (by weight the propor- tions are 23.16 units of oxygen to 76.77 of nitro- gen). In addition to these principal ingredients air carries minute quantities of many other con- stituents, some of which appear in the constant proportions indicative of normal components, while others are variable with locality and circumstance. Among the more evident of these minor con- stituents of the atmosphere are water vapor, car- bon dioxid, ammonia, nitric acid, argon, helium, neon, krypton, and ozone, besides quantities of dust, germs, and other minute solid particles held in suspension. The water vapor may represent as much as 2-J- parts by weight of saturated warm air, but ordinarily the quantity is much less. The carbon-dioxid content varies from .0043 in the country to as much as .07 or even .1 of the whole weight of the air in cities. This gas, which is pro- duced in the lungs of all animals, from which it is THE ATMOSPHERE 47 constantly given off as a waste product of the con- tinuous oxidation of the blood that is essential to life, to the vegetable kingdom bears the relation of a food, thus beautifully disclosing the wonderful adaptation of all natural phenomena to interlink with one another. For in the leaves of all plants there constantly goes on a mysterious absorption and fixation of the carbon from the carbon dioxid of the atmosphere, apparently by some not under- stood action of the green chlorophyl they contain, while the oxygen thus freed from its combination is in this case the waste product. Argon constitutes about .01 of air. The total amount of ammonia and other less important gases js probably less than .01 in the lower atmos- phere, though there are reasons for supposing some of these gases to be more abundant above. The ammonia in air is generally stated as amount- ing to about .000006 of the total weight, while neon is present to the extent of about .00001. Both argon and helium have been determined to exist at all heights up to 46,000 feet, but above this height no helium has been detected. Ozone, which is an allotropic form of oxygen, varies from none in cities to .0000015 in the country, and is more abundant in summer, especially during thunder- storms and high winds. The amount of dust in the air is much the greatest in the lower strata of the atmosphere, to which it is so closely confined that balloonists are frequently able to discern definite dust levels at certain heights. 48 VEHICLES OF THE AIR COLOE AND TEANSPAEENCE Though in small quantities air is without any color that can be perceived, the fact that distant objects seen through it acquire a blue tinge, which also appears as the color of the sky, makes it evi- dent that even the smallest quantity of air must faintly possess this hue. While commonly regarded as perfectly trans- parent, air nevertheless offers considerable ob- struction to the passage of light rays and to vision. Indeed, were the atmosphere in undiminishing density to extend to any great height it is a safe conclusion that its presence would prevent our seeing even the brightest of the heavenly bodies. As it is, the whole amount of air above the earth being only equivalent to 26,166 feet of air at sea- level density, it offers more obstruction to vision in a lateral direction than in the vertical a fact that becomes very apparent when it is attempted to make out distant details from a mountain top or balloon, affording an outlook of many miles in a horizontal direction. Weight for weight, air is little more transparent than glass or water, 30 feet of the former and 18 feet of the latter being equivalent to the entire height of the atmosphere and offering little more obstruction to vision, espe- cially when compared with air containing much dust or water vapor. AIR AT REST Air in a state of rest, subjected to any given but unvarying conditions of pressure, temperature, THE ATMOSPHERE 49 and composition, presents comparatively few and simple problems. Of its static properties, the most important are its compressibility, those re- lating to the effects of temperature, and those relating to its phenomena of liquefaction and solidification. COMPEESSIBILITY Air in common with all other gases has the quality of compressibility a quality not measur- ably possessed by most liquids. For this reason its volume is always proportionate to the pressure upon it, it expanding with every reduction in pres- sure and occupying less space with every increase. Through a considerable range of pressures the space occupied is almost directly proportionate to the pressure a doubling of the pressure reducing the volume by one-half, etc. Air cannot be com- pressed without the work expended appearing in the form of a rise in temperature, and, conversely, allowing compressed air to expand always results in a lowering of temperature. EFFECT OF TEMFERATUKE Heating or cooling of air causes it to expand or contract. Through a considerable range of the com- moner temperatures such expansion or contraction is closely proportionate to the amount of change in temperature. This property is taken advantage of in hot-air balloons, as explained on Page 97. Heating air that is confined results in an increase of pressure, and cooling compressed air results in a decrease of pressure. 50 VEHICLES OF THE AIR LIQUEFACTION AND SOLIDIFICATION Almost every known form of matter, whether normally appearing as a solid, liquid, or gas, can by sufficient change in the conditions of tempera- ture and pressure be made to assume any of these three conditions. Thus the hardest rocks and the strongest metals can be melted into liquids and volatilized into gases, while practically all known liquids can be solidified as in the familiar case of the freezing of water. Likewise, the lightest gases, when subjected to sufficient cold and pres- sure, assume first a liquid and then a solid form. Air is no exception to this rule, becoming a liquid at 220 Fahrenheit under a pressure of 574 pounds to the square inch or less, if the tempera- ture be lower. Further cooling causes it to become solid, though the temperature required to pro- duce this condition is so low that it can be at- tained only with the greatest difficulty. Liquid air, because of its compact form as a source of oxygen, and its expansion into the gas- eous form at high pressure upon exposure to or- dinary atmosphere temperatures, often has been proposed as a source of stored energy for motors, but so far no such application has proved suc- cessful. AIR IN MOTION Air in motion possesses properties that are very little understood, the laws of its dynamic actions and reactions not having been gener- ally investigated or formulated. Particularly with THE ATMOSPHERE 51 reference to the operation of heavier-than-air ma- chines is this the case. Indeed, more than one of the world's foremost physicists, even in compara- tively recent years, has positively declared aerial navigation to be impossible, basing his conclusions upon difficulties encountered in reconciling the idea of man flight with established hypotheses of aerodynamics. Air, possessing almost perfect elasticity in addition to its weight, fluidity, and other qualities, cannot be set in any but the most simple movements without occasioning a multi- tude of resultants that are so utterly complex and involved as to defy analysis. The result is that even such comparatively simple phenomena as those of the movement of air in pipes and in jets are only understood in a general way, while the work of most investigators of flight problems has had to be almost purely empirical, or, when mathematical, has been unsuccessful. The one conspicuous exception with which the writer is familiar is found in the investigations and ex- periments of Professor Montgomery, whose con- clusions are outlined in the article printed in Chapter 4. Of the dynamic properties of air, the most im- portant from present standpoints are its inertia, elasticity, and viscosity. INEETIA Air, in common with all other matter having weight, exhibits the various phenomena of inertia, which may be defined as the tendency of a mass to 52 VEHICLES OF THE AIR remain at rest, or to continue in uniform motion in a straight line, until acted upon by some disturb- ing or retarding force. Naturally, air being much lighter than solid and liquid forms of matter, its inertia is less marked than in the case of heavier substances. But that under favorable conditions this is a factor to reckon with is abundantly proved throughout a great range of natural phenomena, from the flight of birds to the extraordinary vaga- ries of cyclone action. In fact, as one great in- vestigator has tersely expressed a profound truth in form to be appreciated by the man in the street, "the air is hard enough if it is hit fast enough." ELASTICITY The property of elasticity is one of the funda- mental qualities that distinguish air and other gases from liquids. Air and other gases are in fact the only perfectly elastic substances known that is, the only substances that will withstand compression to an indefinite extent and for in- definite periods without in the slightest degree losing their ability fully to recover the original volume. Gases compressed under thousands and even hundreds of thousands of pounds to the square inch, for no matter how long a period, in- stantly and unfailingly expand to any extent per- mitted by release of the pressure. It is to a great extent this property that, under favorable conditions, makes for the high efficiencies realized with suitably-designed mechanisms for operating on masses of air. THE ATMOSPHERE 53 VISCOSITY Viscosity is a property of fluids closely com- parable to the cohesion of solids and may be de- fined as the tendency of the molecules to occasion friction when driven against or past one another. The viscosity of air is often stated to be much higher than that of water (not per unit of volume, but per unit of weight), but there is reason for doubting the soundness of this conclusion. How- ever, it is at least true that air possesses viscosity, and that this sets up increasing resistances to movement as the speed of the movement rises. The question of skin friction on aeroplane and propeller surfaces is closely related to that of the viscosity of air. METEOROLOGY The matters of climatic conditions, storm phenomena, and temperature, and barometric and electrical conditions in the atmosphere must all, in the nature of things, be of the utmost interest to both present and future air navigators. Meteorological conditions may be broadly grouped in two classes the first comprised of con- ditions of a primary or static character, and there- fore not directly inconsistent with fair weather, while the second class includes such meteorological phenomena as are directly related to winds and storms. Generally speaking, there are three funda- mental or primary changes to be noted in the at- 54 VEHICLES OF THE AIR mosphere in a given period in any locality changes in temperature, changes in barometric pressure, and changes in humidity. Secondary ef- fects, usually rather definitely resultant from the foregoing, are the condensation of moisture and its precipitation in the f orfri of rain, snow, or hail and the movement of the air in the form of winds. TEMPEEATUEE Besides the seasonal variations in temperature, which vary greatly with locality, there is the re- markably uniform lowering of temperature with increase of height, the atmosphere being warmest at or near the surface at sea level and progressive- ly colder at greater altitudes, as is evident in the phenomenon of perpetual snow on high mountains, even in warm climates. Observations with sounding balloons have dis- covered temperatures lower than 100 F. at great heights, with 50 commonly prevailing, even in summer. The lowest temperature ever recorded at the earth's surface is 90 F., observed in Si- beria this degree of cold exceeding any that has been recorded elsewhere on the surface, even in polar exploration. At the other end of the range are temperatures of about 140 above zero Fahren- heit, noted in India, the Sahara, the southwestern United States, Australia, and elsewhere in the desert and equatorial regions of the world. The following two tables of sounding-balloon records will be of interest: THE ATMOSPHERE 55 FROM SAINT LOUIS, MAY 6, 1906 FROM SAINT LOUIS, MAY 10, 1906 HEIGHT ABOVE HEIGHT ABOVE SEA LEVEL TEMPERATURE SEA LEVEL TEMPERATURE 623 feet 57.2 F. 623 feet 68.0 F. 3,281 feet 46.4 F. 3,281 feet 59.0 F. 6,562 feet 31.2 F. 6,562 feet 46.4 F. 9,843 feet 21.2 F. 9,843 feet 37.2 F. 13,123 feet 15.8 F. 13,123 feet 21.2 F. 16,404 feet 17.6 F. 16,404 feet 6.8 P. 19,685 feet 5.0 F. 19,685 feet 2.2 F. 32,808 feet 52.6 F. 22,966 feet 26.6 F. 26247 feet 29.2 F. 26,247 feet 32.8 F. 29,527 feet 40.0 F. 29,527 feet 45.4 F. 32,808 feet 52.6 F. 32,808 feet 59.0 F. 36,089 feet 50.8 F. 36,089 feet 76.0 F. 39,370 feet 49.0 F. 39,370 feet 70.6 F. 42,651 feet 54.4" F. 42,651 feet 67.0 F. 45,932 feet 56.2 F. 45,932 feet 70.6 F. 49,212 feet 59.0 F. 49,212 feet 72.4 F. 52,893 feet 68.8 F. 54,298 feet 67.0 F. A remarkable feature well shown in the above is the " permanent inversion layer", or isothermal stratum, of the upper atmosphere, it being noted that at from 33,000 to 49,000 feet beginning just higher than the tops of the highest mountains a minimum temperature is reached, after which there tends to be a slight but fairly regular rise. This change has been discovered to exist all over the world in both the tropical and temperate zones, near the arctic circle, and over the Atlantic ocean. In the record ascent of the sounding balloon from TIccle (see Page 44) the lowest temperature registered was 108.6 F., at 42,323 feet. At 95,275 feet, the greatest altitude reached, the tem- perature had risen to 82.12 P. In the Berson and Sirring ascent, on December 4, 1894, the lowest temperature at 28,750 feet- was _54 F. At the start in Berlin the tempera- ture was 37 F. 56 VEHICLES OF THE AIR BABOMETKIC PEESSUEE The weight of the atmosphere, as shown by the barometric pressure, varies with height, tempera- ture, and latitude. As is elsewhere explained herein, by far the most considerable variations are those due to height, for which reason a high-grade aneroid barometer constitutes a very accurate means of estimating altitude. At sea level, under normal conditions, the baro- metric pressure is almost exactly 14.7 pounds to the square inch. At great heights it is much less, as, for example in the Glaisher and Coxwell ascent (see Page 74). The Uccle sounding balloon recorded a pressure of 1.74 pounds to the square inch at 42,240 feet, and of only .2 pounds to the square inch at its greatest height of 95,275 feet. HUMIDITY Humidity is a general term for the presence of water vapor in air, but in the more restricted and more specific scientific sense it is commonly under- stood to refer to the percentage of saturation that is to say, to the proportion that the amount of moisture actually present in the air bears to the maximum it might contain. The saturation point varies with temperature cold air being capable of holding less and warm air more water vapor. At a temperature of about 90 F. a cubic foot of saturated air will contain about -g-V ounce, or about T V cubic inch, of water. Saturated air THE ATMOSPHERE 57 cooled to a lower temperature always precipitates its excess of water. This is the explanation of the condensed moisture that is often precipitated from the air on the outside of a glass of cold water, or upon any other cold surface in warm weather, and it has most important bearings upon the phe- nomena of rain and snow fall. The moisture in the air is chiefly derived by evaporation from water areas and land wetted by rains or floods. CONDENSATION OF MOISTURE This always occurs when the atmosphere is cooled until the amount of water present in it amounts to more than the saturation quantity for the given temperature, and the result is ordinarily a precipitation of rain, snow, or hail though it is established that under certain conditions mois- ture thus precipitated may pass into vapor, or be frozen in exceedingly minute crystals, and so re- tained in suspension in the form of clouds. WINDS Winds, amounting simply to more or less rapid movement of portions of the atmosphere with re- lation to the earth's surface, present many aspects of interest to the air navigator, and are worthy of his prof oundest consideration. Atmospheric movements vary in direction, velocity, and duration, and in the presence of ascending or descending components, and are classified according to their velocity, direction, 58 VEHICLES OF THE AIR and duration into the different classes of storms and winds. Winds are supposed to be due chiefly to varia- tions in temperature, though they are affected by tidal movements in the atmosphere and influenced by the earth's rotation. The latter, however, can- not be of very great effect because, though the equatorial speed of rotation is over 1,000 miles in hour, everything terrestrial is so subjected to the earth's attraction that it must be moved uniformly along without materially lagging behind, as might be the case were the rotation irregular or inter- mittent. Tidal currents in the air, caused by the attrac- tion of the sun and moon, are well established to exist, but because of the comparatively small mass of the air they do not vary the barometric pressure more than -^ ounce at sea level, and therefore cannot be of any considerable effect in establishing or controlling winds. Changes in temperature produce effects of much greater magnitude. Air heated through a range of 50 P. is dilated about one tenth of its volume with corresponding lightening of its weight per unit of volume. The result, therefore, of a change of temperature in any portion of the atmosphere is a compression or attenuation that can be relieved only by a flow of air from or to the locality affected, with a violence proportionate to the suddenness and amount of the temperature change and the quantity of air it affects. Also, air being lightened by heating, heated bodies of it THE ATMOSPHERE 59 have a tendency to rise, causing an upward com- pression with a radial inflow from all surrounding places to occupy the spaces thus becoming vacated. Again, air thus caused to ascend into the upper regions of the atmosphere, where, as has been ex- plained, conditions of the most intense cold prevail throughout the year, becomes cooled and thus is turned from its vertical into a horizontal and final- ly a descending course. The fact that a rapid fall of the barometer indicating a reduction in the weight of the air almost always precedes violent winds, seems proof positive of the soundness of the accepted theories of wind causation. There are two principal modes of heating to which the atmosphere is subjected. One is the regular diurnal heating due to the alternation of day and night, a wave of heated air progressing around the world with the sun while a converse cool wave follows the night. The other type of heating is that to which the atmosphere is sub- jected over great areas in contact with the earth a type of heating that becomes particularly mani- fest over great areas of prairie or desert country in summer. Coastal Winds are common along almost all seacoasts and even along the shores of large lakes. They seem distinctly due to the effects of tempera- ture, and, commencing with a light breeze from the sea in the morning rise to a stiff wind by midday, subsiding again to a calm by evening. Then, as darkness comes on, a breeze sets in from the land, 60 VEHICLES OF THE AIR reaching its maximum velocity sometime in the night, and thereafter dying down towards morn- ing. These winds are rarely felt more than twenty miles out to sea or inland, and investigation with kites and balloons has shown them to be invariably accompanied by an opposite movement of the air at some distance above usually at a very moderate height (500 to 1,000 feet). This, besides proving that the air travels in a complete circuit, goes a long way towards explaining the phe- nomenon, it being reasoned that as the air is warmed over the land by the heat of the day it rises, is replaced by air flowing in from the sea, and then flows seaward at an upper level because of the reduced pressure in that direction. At night the land is more quickly affected by the withdrawal of the sun's rays, so now the ascending current commences over the sea, with a sequence of results exactly the converse of the foregoing. Trade Winds, so called because of the de- pendence placed in them by navigators of sailing vessels, are always in the same direction but with seasonal variations in the areas they extend over. They are due to cold currents flowing in from the polar regions to replace the warm air that rises from the equatorial regions of the earth. Normally, they would flow directly north and south to the equator, but the influence of the earth's rotation and the configuration of the land and water areas in the northern hemisphere causes them gradually to veer about, as they progressively reach latitudes where the peripheral speed of the earth's surface THE ATMOSPHERE 61 is higher, until they flow almost directly west, but slightly north or south (constituting the "north- east trade" and the "southeast trade"). The trade winds follow the sun very closely in their areal variations. Over the Atlantic, for example, they come farthest south in February and go farthest north in August, the northeast trades blowing between 7 and 30 north latitude and the southeast trades blowing between 3 north latitude and 25 south latitude. Between the two is a region of calms, from 3 to 8 wide, which goes as far north as 11 north latitude in August and as far south as 1 north latitude in February. Above the trade winds there are well estab- lished to exist return currents, blowing in the op- posite directions. In high latitudes this return current often comes down to the surface and pro- duces easterly trade winds. Cyclones, Whirlwinds, and Tornadoes are local winds of terrific violence and rotary character, which are started by rapid and intense local heating, with consequent rapid rising of locally-heated atmosphere at such a rate that the radial inflow of adjoining air assumes a rotary movement similar to that of water in draining out through a hole in a vessel. The vortex of the storm is at the center of this rotation, where most ter- rible wind velocities are attained if their frightful- ly-destructive effects are any criterion. For- tunately cyclones are usually very small in their areas of maximum violence and are of compara- tively brief duration. 64 VEHICLES OF THE AIR ATMOSPHEEIC ELECTEICITY The presence of electrical action in the atmos- phere, due to the accumulation of enormous static charges of current generated presumably by fric- tion of the air upon itself, accounts for the various phenomena of lightning and thunderstorms. To the student of aerial navigation the most interest- ing aspect of these phenomena is their danger from the standpoint of the balloonist, it being well established that hydrogen balloons have been set on fire by electrical discharges, often of otherwise quite imperceptible character. FIGURE 2. A corner of the Aeronautical Exhibition held in the Grand Palais Paris during October, 1909. The small decorated balloon in the background is a reproduction of the original Montgolfier balloon of 1783 the first ever made. C. Double (Silk and Cotton) G. Double (Silk and Cotton) P. Double (Percale). Q. Double (Percale). FIGUHE 7. Texture of Modern Balloon Fabrics Reproduced Actual Size. Of these, A is a very light fabric ; B is similar but heavier ; C is the material of the Baldwin government balloon ; D, E, and F are heavy fabrics ; G is similar to C, but heavier ; H is a very light fabric for sounding balloons ; I is a very light double fabric, used in the Zeppelin dirigibles ; T and K are double fabrics with the layers crossed to add strength ; L and M are exceedingly heavy double fabrics, for semi-rigid and non-rigid dirigibles ; N is one of the heaviest balloon fabrics used, weighing 14% ounces to the square yard; and O, P, and Q are all high-grade diagonal fabrics with gray rubber to retain the gas and red surfaces to resist sunlight. CHAPTER TWO LIGKETER-THAN-AIR MACHINES I Though as a vehicle of practical utilities it is fast losing ground in comparison with the develop- ing forms of heavier-than-air fliers, and seems con- demned by insuperable objections inherent in its very principle of operation, the lighter-than-air machine the balloon was nevertheless the first with which man succeededftn sustaining himself in the air for considerable periods of time. Since the essential feature of lighter-than-air craft is their ability to float in the air much as a vessel floats in the water, and since the only sub- stances that even approach air in lightness are also gases, it follows that the design of no conceiv- able sort of lighter-than-air machine can escape the necessity for two essential elements space oc- cupied by something lighter than air, and an envel- ope of heavier-than-air material to enclose this S p ace w ith the relations between these two ele- ments so proportioned that the lifting force of the gas is sufficient to overcome the weight of the envelope. In any practical air craft, to the weight of these primary essentials must be added such further weight of structure as may be considered 65 66 VEHICLES OF THE AIR necessary to afford passenger or cargo accommo- dation, and such further quantity of gas as may be required to lift such passengers or cargo as it may be planned to carry. NON-DIKIGIBLE BALLOONS The most elementary type of balloon is that de- signed for mere ascension and flotation in the air, with no attempt at navigation in a lateral direction except as such lateral travel may result from fa- vorable winds. It was a very early suggestion in the history of the balloon that, inasmuch as the direction of the winds frequently varies with dif- ferences in altitude, upper currents often flowing directly contrary to those near the surface, sys- tematic prospecting through these different cur- rents by control of height might result in control of the direction of travel. Yet in the hundreds of attempts made to work something practical out of this idea, nothing of real value has developed. HISTOBY If somewhat uninvestigated, but in nowise dis- credited Oriental history is to be believed, the invention of the balloon is properly to be ascribed to that inscrutable people, the Chinese, who, ac- cording to a French missionary writing in 1694, sent up a balloon in celebration of the corona- tion of the emperor Fo-Kien, at Pekin, in 1306. Furthermore, this ascension is stated to have been only the carrying out of an established custom, rather than the first ever made by the Chinese. It LIGHTER-THAN-AIR MACHINES 67 is not recorded whether or not any of the Chinese balloons ever carried passengers. The first European appreciation of the prin- ciple by which a balloon is made to ascend appears to have been due to a Jesuit, Francis Lana, who in a work published at Brescia, Italy, in 1670, pro- posed an airship sustained by four hollow copper vacuum balls, each twenty-five feet in diameter and ^ inch thick, affording a total ascensional force of about 2,650 pounds, of which some 1,620 pounds would be the weight of the copper shells, leaving 1,030 pounds for the weight of the car, pas- sengers, etc. The difficulty of securing sufficient strength to withstand the pressure of the atmos- phere Lana assumed would be met by the domed form of the surface, but in view of the fact that the total pressure on each sphere would figure over 4,000,000 pounds, the possibility of resisting it with so thin a shell still remains to be demon- strated. In 1766 Cavendish made public his estimations of the weight of hydrogen, immediately following which Dr. Black, of Edinburgh, made a calf-gut balloon which, however, proved to be too heavy for sustention by the hydrogen it could contain. A few years later, Tiberius Cavallo, to whom a simi- lar idea occurred, found bladders to be too heavy and paper too permeable, but he did succeed in inflating soap bubbles with hydrogen in 1782, with the result that they floated upwards until they burst. It is a somewhat remarkable coincidence that 68 VEHICLES OF TEE AIR just as the modern aeroplane has been most promi- nently associated with the names of two brothers, so to two brothers, Stephen and Joseph Mont- golfier, is generally ascribed the invention of the balloon. Tradition has it that, inspired originally by reading Dr. Priestly 's " Experiments Relating to Different Kinds of Air", the Montgolfiers, who were sons of Peter Montgolfier, a paper manufac- turer of Annonay, France, were next impressed from observation of the clouds with the idea that if they could fill a light bag with "some substance of a cloud-like nature" it would similarly float in the atmosphere. Accordingly with the notion of using smoke as the required "substance" Stephen, who appears to have been the prime mover in the enterprise, started to experiment with large paper bags, of capacities up to 700 cubic feet, under which were burned fires of chopped straw. Though success immediately resulted, it is inter- esting to note that it was some time before the brothers realized that the real source of the lift- ing effect was the heating of the air within the bags and not the smoke with which they sought to fill them. Having demonstrated the possibility of making small balloons ascend, the Montgolfiers next built a spherical paper balloon thirty feet in diameter, with a capacity of about 13,000 cubic feet and pos- sessed of a consequent ascensional force, when inflated with heated air, of probably 500 pounds. This balloon was sent up from Annonay, without passengers, on June 5, 1783, in the presence of L1GHTER-THAN-AIR MACHINES 69 many spectators. It rose to an estimated height of a mile and a half before the air within it cooled sufficiently to cause its descent, ten minutes after its release. A modern reproduction of one of the first Montgolfier balloons is shown in Figure 2. Following this first balloon ascent, on August 27, 1783, M. Faujas de Saint-Fond, a naturalist; M. Charles, a professor of natural philosophy in Paris, and two brothers by the name of Robert, sent up a hydrogen balloon from the Champ de Mars, in Paris. This balloon, thirteen feet in diam- eter and weighing less than twenty pounds, was made of thin silk coated with caoutchouc, and required four days for its inflation, the hydrogen being generated by the action of 500 pounds of sulphuric acid on half a ton of iron filings a proc- ess that only very recently shows signs of being superseded (see Page 99). When liberated the balloon rose rapidly to a height of about 3,000 feet, burst, and then landed three-quarters of an hour later in a field near Gonesse, fifteen miles away, where it was destroyed by terrified peasants. The next balloon ascent was that of a spherical bag, of linen covered with paper, made by the brothers Montgolfier. This balloon, which was the second of the same material the first having been destroyed by a storm of wind and rain before it could be used had a capacity of 52,000 cubic feet, and was sent up from Versailles, France, on Sep- tember 19, 1783. A small car was attached, in which were placed a sheep, a cock, and a duck, which thus had thrust upon them the distinction 70 VEHICLES OF THE AIR of being the first balloonists. The descent occurred eight minutes after the start, and the sheep and duck were uninjured. The cock had not fared so well, and his condition was gravely attributed by the savants present to the effects of the tenuous atmosphere of the upper regions. Calmer subse- quent diagnosis, however, indicated that he had been tramped upon by the sheep. The first ascent of a man-carrying balloon was one ventured by Pilatre de Rozier, who entrusted himself to a captive balloon, built by the Mont- golfiers, on October 15, 1783. The balloon was per- mitted to ascend only to a height of less than 100 feet, at which elevation it was kept for a period of a little over four minutes by continuous heating of the air inside of it by means of a fire of chopped straw. Following this, on November 21, 1783, de Rozier and a friend, the Marquis d'Arlandes, made the first free balloon ascension, in which the start was from Paris, with the descent safely accom- plished in a field five miles from the French metropolis after about twenty minutes of drifting at not over 500 feet high. It is recorded that Benjamin Franklin, who was a witness of this first aerial voyage, was asked by a pessimistic spectator for his opinion of the utility of the new device, to which Franklin is said to have replied, "Of what use is a new-born babef Only seven days after the foregoing, on Novem- ber 28, there was made from Philadelphia, under the auspices of the Philosophical Academy of that LIGHTER-THAN-AIR MACHINES 71 city, a balloon ascent that has escaped the atten- tion of most of the writers on the subject. The enterprise was in charge of two local scientists, Hopkins and Eittenhouse, who first made experi- ments by sending up animals in a car attached to forty-seven small hydrogen balloons. They then persuaded one James Wilcox, a carpenter, to go aloft, with the result that to this man belongs the honor of having first ascended with a hydrogen balloon. The descent, which barely missed being into the Schuylkill River, was so abrupt that the lone passenger dislocated his wrist. The first European ascent with a hydrogen bal- loon was made on December 1, 1783, by Charles and Robert, who safely accomplished a twenty- seven mile trip at about fifteen miles an hour from Paris to Nesle, France, in two hours, reaching a height of 2,000 feet. At Nesle a landing was effected and Robert got out, whereupon Charles made a further journey of two miles in the course of which it is asserted he rose to a height of 10,000 feet, at which altitude he suffered severely from cold and the rapid lowering of the atmospheric pressure. The balloon used on this occasion was over twenty-seven feet in diameter, sewed up of varnished silk gores, and on the whole very well designed, being provided with a net and valve. The car was boat-like, eight feet long, and weighed 130 pounds. Ballast was used to control and a barometer to measure the height. Indeed, nearly every essential feature was closely similar to the 72 VEHICLES OF THE AIR corresponding features in the best modern gas balloons, which therefore date back more defin- itely to the ingenious Charles than to any other investigator. During 1784 balloons became common through- out all Europe and many successful ascents were made. The first woman to ascend in a balloon was a Madame Thible, who went up from Lyons, France, during this year. On January 7, 1785, a remarkable balloon voy- age was made with a hydrogen balloon by Jean- Pierre Blanchard and an American physician named Jeffries, these two embarking from the cliff near Dover castle and crossing the English Channel to the forest of Guines, in France, the distance being made with a favorable wind in something less than three hours. In an attempt to repeat this feat, on June 15, 1785, at the age of twenty-eight years, Pilatre de Rozier, the first aeronaut, became also the first victim of aerial travel, he and a friend, M. Romaine, both losing their lives through the balloon, which was of the Montgolfier type, catch- ing fire at a considerable height. Since the foregoing, which are the more impor- tant and interesting of the early balloon ascensions, thousands of others have been made all over the world. In the course of these some utility has developed in the way of military and meteorolog- ical observation, but in most cases the immediate purposes and the ultimate results have not been more serious than the catering to a somewhat LIGHTER-THAN-AIR MACHINES 73 the crowd to pay its money for the spectacle of a parachute jump. However, despite the extreme and often unnecessary risks that have been taken by the ignorant or reckless, an examination of the statistics of ballooning discloses a surprisingly small number of fatalities in proportion to the number of ascensions that have been made. The history of ballooning has been from the first closely associated with warfare. Indeed, it is said that one of the avowed purposes of the Montgol- fiers was to render more effective the siege of Gibraltar, by the combined French and Spanish forces, who, however, gave up the fight some time before the Montgolfiers proved the practicability of the balloon. Subsequently a regular " aero- static corps" was attached to the French army, and did service during the French Revolution and Napoleon's Egyptian campaign. Considerable utility was demonstrated during the battle of Fleu- rus, in the course of which two aerial reconnais- sances from a captive balloon contributed mate- rially to the victory of the French over the Aus- trians. But when a balloon sent up in honor of his coronation was wrecked against a statue of Nero, the great Corsican seems to have lost inter- est in the new invention. Some use of balloons was made by both sides in the American Civil War, and in the Spanish- Amer- ican war a balloon was successfully employed to discover the presence of Cervera's fleet in Santiago harbor, but by far the most important use ever 74 VEHICLES OF THE AIR made of balloons was in the siege of Paris, dur- ing the Franco-Prussian war in 1870. In this remarkable application seventy-three postal bal- loons were built and sent out from the beleaguered city with cargoes of mail and carrier pigeons, which were used to bring back replies to the messages. In this way over 3,000,000 letters were transmitted, those brought back by the pigeons being reduced so small by photography that 5,000 separate missives weighed only nine grains. One of the longest balloon voyages on record not exceeded until within comparatively recent years was that of John Wise from St. Louis to Henderson, N. Y., in July 1859. This journey was accomplished in a lively gale, with the result that the distance of 950 miles was covered in nineteen hours. October 9-11, 1900, Count Henry de la Vaulx and Count Castillion de Saint Victor super- seded the Wise record by a journey from Vin- cennes, France, to Korostichev, Russia, a distance of 1,139 miles, in thirty-five hours and forty-five minutes. The present balloon duration record is held by Lieutenant-Colonel Schaeck, of the Swiss Aero Club, who in the balloon Helvetia, sent up from Berlin on October 11, 1909, remained in the air sev- enty-two hours, finally landing in the sea off the coast of Norway. The balloon altitude record was long credited to Glaisher and Coxwell, who on September 3, 1862, reached a height claimed to have been 36,090 feet. Some discredit has been cast upon the achievement LIGHTER-THAN-AIR MACHINES 75 by doubt concerning the possibility of sustaining life at such a height without carrying a supply of artificial oxygen, with the result that the maxi- mum altitude is now believed to have been not over 29,520 feet. On December 4, 1894, Professors Berson and Gross ascended from Berlin and defi- nitely recorded an altitude of 28,750 feet. Subse- quently, on July 31, 1901, Berson and Sirring, of the "Berlin Verein fur Luftschiffahrt", reached a height of 35,400 feet, using oxygen tanks. So-called "sounding balloons", for meteorolog- ical investigation, but without passengers and car- rying only self-registering instruments, have reached much greater heights, the record being held by the balloon which was sent up from the Uccle Observatory in Belgium (see Page 44). SPHERICAL TYPES The simplest and in some respects the most advantageous form of balloon is the spherical, because a given surface of envelope will enclose a greater volume in the form of a sphere than in any other shape. More than this, since a sphere is the form into which any flexible hollow struc- ture tends to distort under the influence of an interior pressure, a sphere is, therefore, the only form not subject to distortion stresses. In the construction of spherical balloons, the plan usually followed is to cut the material into narrow, double-tapered gores, laid out as shown in Figure 3. These gores when sewn together along their adjacent edges afford a practically 76 VEHICLES OF THE AIR perfect approximation to the required form, as is indicated at a, &, c, and d, Figure 3. The correct shape of the gores is found by laying them out as shown in Figure 3. Practically all non-diri- gible balloons are now made spherical sometimes modi- fied into a pear-shape to provide the open neck com- monly used to allow for ex- pansion and contraction of the gas. Except from the standpoint of dirigibility there are few advantages and many positive disad- vantages in all but the spherical form. One of the most serious of these dis- advantages is the necessity for some sort of rigid or semi-rigid construction to protect non-spherical struc- FIGURB 3. Layout of Gores for Spherical Balloon. The dimension a e is one-half of the circumference of the balloon and the dimension 6 c is the circumference di- vided by the number of gores it is intended to use. These major dimensions settled upon, intermediate points on the gore curve, as at q, will be found as shown at the Junctures of lines projected from similar points on the diameters of the large and small semicircles. tures against dangerous distortion. DIRIGIBLE BALLOONS Naturally in the development of the balloon it was early attempted to navigate definite courses from one point to another, either in calm weather or independent of the direction of the winds. It was soon seen to be manifestly impos- LIGHT EE-TH AN -AIR MACHINES 77 sible, though, to derive propulsion from the wind except directly before the wind, anything analo- gous to the tacking of a ship being out of the ques- tion because of the lack of any fulcrum such as is provided by the hull of a ship in the water. This compelled recourse to various systems of internal power development and application, commencing with the hand-manipulated oars and sails of early investigators and coming down to the engines and propellers of modern dirigibles. Another obvious line of improvement along which much work has been done consists in the reduction of the head resistances against which it is necessary to propel a balloon, reduction of these resistances being the ideal held in view in the con- struction of the many cylindrical, cigar-shaped, and other elongated and pointed gas bags with which the modern student of this subject is familiar. So far, however, all successes achieved with dirigible balloons have been more spectacular than practical, and there is little reason for expecting that results of more serious value are in any pres- ent prospect of attainment. Certainly, admitting the possibility of an exceedingly limited and pre- carious utility for the dirigible in warfare, it is, in the opinion of those best qualified to judge, most unlikely ever to assume the least importance as a means of travel. The great difficulties with the balloon are its inescapably enormous volume and its strict limita- 78 VEHICLES OF THE AIR tions in weight of structure. To ascend, a balloon must be lighter than the volume of air it displaces and, the weight of a given volume of air being fixed and unchangeable, no possible discovery or inven- tion (unless of some structural materials of alto- gether ultra-terrestrial strength) can open a way of escape from this inexorable factor of the prob- lem. A sphere of air ten feet in diameter weighs almost exactly seventy-six pounds, while a simi- lar sphere of hydrogen weighs something less than six pounds. Consequently, enclosing the hydrogen in an envelope and causing it to occupy the space of an equivalent volume of air manifestly affords a gross lifting capacity within this consid- erable bulk of seventy-six minus six only seventy pounds. Evidently the unlikely discovery of some gas lighter than hydrogen can effect no material benefit, for even should it become feasible to encase a vacuum of the requisite size, as some enthusiasts have hoped, this could help the sustention only to the extent of the eliminated six pounds of hydro- gen. And always within whatever lifting capacity there may be provided must come not only the loads that it is required to convey, but also the weight of the structure and the enveloping mate- rial, which it is highly desirable to have far stronger and rigider than the strongest and rigid- est ever likely to be attainable. From all of which it follows that the best of balloons are, and are likely to continue, hopelessly bulky and fearfully flimsy, and of only the very LIGHTER-THAN-AIR MACHINES 79 smallest lifting capacities in proportion to their size. Held captive or let drift with the wind, they can be made to afford fair security with very lim- ited utility. Provided with motors and propelling means, they not only oppose the resistance of enor- mous areas to rapid motion, but also prove of such fragility that their structure must inevitably col- lapse under the heavy stresses, should sufficient power within the weight limit ever become avail- able to drive them greatly faster than the maxi- mums of twenty-five or thirty miles an hour that have been so far attained, and which are nowhere near sufficient to combat ordinary adverse winds. The cost of gas alone for each filling of a large balloon at present places it utterly out of the ques- tion for performing commercial service at reason- able cost. About a thousand dollars worth of gas on the basis of the most economical production pos- sible (see Page 99) is required for each inflation of a Zeppelin balloon, 443 feet long and 42 feet in diameter, but possessed of a reserve carrying capa- city of only five and a half tons. Moreover, no bal- loon builder as yet has been able within the weight limitation to devise an envelope capable of retain- ing a filling of gas for more than a limited period not to consider the further loss that occurs in the necessary trimming of the craft to desired heights by alternate discharges of gas and ballast the latter of which, by the way, is a burden to be reck- oned with in all estimates of passenger and cargo- carrying capacities. 80 VEHICLES OF THE AIR HISTORY One of the earliest well studied attempts to pro- duce a successful dirigible balloon was made by Henri Giffard, in Prance, in 1852. In Giffard's FIGURE 4. Giffard's Dirigible Balloon. Propelled by 3-horsepower steam engine, weighing, with fuel and water for one hour, 462 pounds. Length 144 feet, diameter 39 feet, capacity 88,300 cubic feet. Made 7 miles an hour In 1852. machine, illustrated in Figure 4, the gas bag was spindle-shaped, 144 feet long. Though the motor proved very weak it was found possible in very quiet air to steer and to travel in circles, with a maximum speed of scarcely seven miles an hour. In 1870 another French experimenter, Dupuy de Lome, at Vincennes, tried out a machine pro- vided with an enormous two-bladed propeller, 29 feet 6 inches in diameter. This propeller was turned slowly by the muscular efforts of the eight passengers and, in a breeze of about twenty-six miles an hour, "a deviation of twelve degrees" LIGHTER-THAN-AIR MACHINES 81 from a normal straight drifting course was obtained. At Grenelle, France, in 1884, Gaston and Albert Tissandier maneuvered for two and a half hours in ithe dirigible illustrated in Figure 5. This was driven by a one and one-third horsepower Siemens electric motor, weighing 121 pounds and taking current from a bichromate battery weighing 496 FIGURE 5. Tissandier's Dirigible Balloon. Propelled by 1% -horsepower electric motor and primary battery, weighing 616 pounds. Length 92 feet, diameter 30 feet, capacity 37,440 cubic feet. Made 7 miles an hour in 1884. pounds. The propeller was two-bladed, nine feet in diameter. In a wind of eight miles an hour and with a horsepower output estimated to have run as high as one and a half, a large semicircle was suc- cessfully described, following which, in a wind of seven miles an hour, headway was made across the wind and various evolutions performed above the Grenelle observatory. 82 VEHICLES OF THE AIR Following the Tissandier experiments, Com- mandant Eenard of the balloon corps of the French army, on September 23, 1885, navigated from Chalais-Meudon to Paris against a light wind and returned with little difficulty to the point of depar- FIGURB 6.- Renard and Kreb's Dirigible Balloon. Propelled by 9-horse- power electric power plant, weighing 1,174 pounds. Length 165 feet, diam- eter 27 feet, capacity 65,836 cubic feet. Made 14 miles an hour in 1885. ture, making several ascents and descents en route. Little more of especial interest was accom- plished until in 1901 a young Brazilian, Alberto Santos-Dumont, commenced in France a record- breaking series of performances with a succession of dirigibles. His most notable accomplishment was winning, on the fourth attempt, with his San- tos-Dumont No. 6, the M. Deutsch prize of about $15,000 on October 9, 1901, for traveling from the Pare d' Aerostation at St. Cloud to and around the Eiffel tower and back. His time was about thirty minutes for the distance of nine miles. The bal- loon, which was the sixth dirigible built by Santos- Dumont, was 108 feet long and 20 feet in diameter, and was propelled by a 16-horsepower gasoline automobile engine. Subsequent to this Santos Dumont built at least six more dirigibles. The Lebaudy brothers, in 1903, built a dirigible LIGHTER-THAN-AIR MACHINES 83 185 feet long and 32 feet in diameter which, with a 40-horsepower gasoline motor, is said to have attained a speed of 24 miles an hour. In England the most successful early dirigibles were those of Spencer, Beedle, and Dr. Barton. The first of these was 93 feet long and 24 feet in diameter, with a 24-horsepower motor. The Beedle balloon was of the same proportions, but had only a 12-horsepower motor. Dr. Barton's balloon was 170 feet long and 40 feet in diameter and was pro- pelled by two separate 50-horsepower gasoline motors. It was complicated by an excess of aero- plane stabilizing surfaces that undoubtedly sub- tracted from, rather than added to, its utility. Recent military dirigible balloons of some suc- cess or prominence are the English "Baby", the French "Liberte", "and "Republique", and the " Ville de Nancy", and the German Gross and Par- seval balloons. The first of these is very small and makes a speed of only 7 miles an hour, but it is exceedingly convenient and portable. The "Lib- erte" and the "Republique" are up-to-date devel- opments of the Lebaudy type, and the "Ville de Nancy", illustrated in Figure 18, is a Clement- Bayard product designed for the Russian army. The latter airship, which is 180 feet long and 33 feet in diameter, with a capacity of 180,000 cubic feet, is provided with an internal balloon or bal- lonet, of the type illustrated in Figure 13, by which the main gas bag is kept constantly distended under an internal pressure of a little over seven pounds to a square foot. This balloon made its first ascent 84 VEHICLES OF THE AIR on June 27, 1909, and subsequently, on June 28 and July 2, it twice remained five hours in the air. Late in August, 1909, it was badly damaged by an inadvertent descent into the Seine, occasioned by a heavy wind coming up while it was at a height of 4,000 feet. On September 25, 1909, the "Be- publique" exploded at a height of 500 feet, near Paris, and fell to the ground, causing the death of four French army officers. The latest Gross dirigible has a capacity of 270,000 cubic feet and is propelled by two motors with a total output of 75 horsepower, driving two propellers. Twin ballonets are used to keep the envelope taut, and journeys of over fifteen hours' duration have been accomplished. On May 22, 1909, a race was held near Berlin between the " Gross II" and the "Parseval II", which is of similar construction. The contest was a tie, with a time of fifteen minutes for a circuit over the Templehof parade grounds. A very curious small dirigible, designed by Isa- buro Yamada, was used by the Japanese army during the siege of Port Arthur. This balloon, which was 110 feet long, differed from all other dirigibles in that the 50-horsepower gasoline motor was in a separate car, much below and in advance of the car proper. A dirigible that has been much in the public eye is the " America", designed by Melvin Vani- man and Louis Godard for use in the polar explora- tion project promoted by Walter Wellman. This LIGHTER-THAN-AIR MACHINES 85 balloon, details of which are illustrated in Figures 12, 19, and 20, is 184 feet long and 52 feet in diameter, with a capacity of 258,500 cubic feet of gas. The total ascensional force at sea level is 19,000 pounds, the weight of the envelope 3,600 pounds, and that of the car, motors, and full tanks of fuel 4,500 pounds. Propulsion is by two bevel- gear-driven steel propellers, 11 feet in diameter, revolved by a 70-80-horsepower Lorraine-Dietrich motor. An 80-horsepower Antoinette motor with a duplicate pair of propellers is kept in reserve. Despite the expenditure of large sums of money and attempts made season after season, the nearest this balloon has come to reaching the pole has been a thirty-mile flight from its base in Spitzbergen. In the United States little has been done toward the development of dirigible balloons, such activity as there has been being confined to the more or less perfect copying of the best foreign construc- tions. Knabenshue, Baldwin, and Stevens have been the most successful among the American dirigible balloon navigators. In every way the most interesting and most important devices in this field of aerial navigation are the great dirigibles of Count Zeppelin, which unquestionably are so far in advance of other con- structions of the same general character that their points of merit constitute a fair measure of all dirigible practicability, while their more serious shortcomings are reasonably to be regarded as among the defects of all possible craft of the lighter-than-air type. 86 VEHICLES OF THE AIR In his work Zeppelin appears particularly to have sought the attainment of the utmost possible length in proportion to diameter, with a view to keeping down head resistance while at the same time securing lifting capacity. This in turn has compelled recourse to a rigid structure for the gas bag as the only possible means of keeping one of such length in shape. Safety has been provided by a multiplication of lifting units, there being seventeen separate and independent balloons enclosed between par- titions in the structure. Great lifting capacity is secured by sheer size, while height control is in large measure attained by the provision of fin and rudder-like stabilizing or balancing surfaces. The partially-sectioned illustration in Figure 17 affords an excellent idea of the construction of all the Zeppelins, of which several have been built. The first of these were commenced in the late nineties at Friedrichshafen, on Lake Constance, where there was built a mammoth floating balloon house, 500 feet long, 80 feet wide, and 70 feet high, mounted on ninety-five pontoons. This house, being anchored only at its forward end, was free to swing so as always to face the wind, with the result that the balloon could be taken out and housed without danger of collision. The first Zeppelin balloon was 410 feet long and 39 feet in diameter, with its framing made up of sixteen twenty-four-sided polygonal rings, sepa- rated by spaces of 26 feet. The rings, stays and even the wire bracing were at first made of "wol- LIGHTER-THAN-AIR MACHINES 87 framinium" (see Chapter 11), but in subsequent models it is said that this metal has been by degrees given up, until in balloons now building for the German government it is almost entirely replaced with wood and steel. Over the framing and between the chambers ramie netting was liberally applied, reinforcing both structure and fabric. The nose of the bal- loon was capped with a sheet-aluminum bow plate. The compartments, which in the first model contained a total of 351,150 cubic feet of hydrogen, affording a total lift of eleven tons, are lined with rather lighter balloon fabric than is necessary for non-rigid dirigibles, and this fabric is proofed with the gray quality of rubber which affords the high- est resistance to the leakage of gas. Over the outside of the framing a non-gasproof fabric is used. A space of about two feet is provided all around the internal balloons, under this external cover, to serve as a protection from the heat of the sun. Two boat-like cars, at the ends of a stiffen- ing keel of latticed framework, are provided on the underside of the cylindrical body, and are suffi- cient to float the whole craft on the water. These cars, each 21.32 by 5.96 by 3.28 feet, are connected by a passageway 326 feet long and from one to the other a cable is stretched, along which a sliding weight can be adjusted to trim the craft fore and aft. In the first Zeppelin a 15-horsepower Daim- ler motor at 700 revolutions a minute was 88 VEHICLES OF THE AIR located in each car, each motor driving two four- bladed propellers, 3 |feet in diameter. The speed of the first Zeppelin was not over seventeen miles an hour and only short journeys were attempted, but in later models in which the sizes have been increased materially and as much as 250 horsepower applied through four three or two-bladed propellers, speeds of as high as twen- ty-five or perhaps thirty miles an hour have been maintained in calm air for distances as great as 950 miles. With the wind the speed is, of course, higher, but, conversely, it is correspondingly lower when the wind is adverse. Landing with the balloons of the Zeppelin type always has proved precarious, especially when the descent has not been on water. Of the several that have been built, one has been burned and all of the others more or less seriously damaged at different times in coming to the ground. Nevertheless, at least the German government continues to interest itself in this phase of aero- nautics, and at the time this is written is reported to be building dirigibles of the Zeppelin type even larger than any that heretofore have been constructed. The map in Figure 270 shows the more impor- tant of the Zeppelin journeys. SPHEEICAL TYPES Very few balloons of the true dirigible type have been built with spherical envelopes, the most noteworthy being one of Blanchard's first bal- LIGHTER-THAN-AIR MACHINES 89 loons, which he sought to propel by hand-manipu- lated wings or oars. However, all balloons may be said to be in some degree dirigible, even those of ordinary spherical types being capable of a slight degree of control by the manipulation of drag ropes, as is explained on Page 114. ELONGATED TYPES As has been previously explained, to reduce head resistances and permit of special strengthen- ing of the bow surfaces practically all dirigible balloons are given elongated forms, necessitating structural stiffening beyond what is obtainable by mere strength and guying of the envelope alone. There are two principal means of attaining such stiffness as is to be had one the use of an under- frame or long truss-like car to which the envelope is securely stayed at intervals, and the other the employment of internal strengthening within the gas bag itself. The first of these constructions, which has been termed "semi-rigid" to distin- guish it from the second type, is the one used in practically all dirigible balloons except the Zep- pelin. The latter machine is not only the foremost exponent, but is also practically the sole represent- ative of the "rigid" system, its details being described in Pages 85 to 88, and in Figure 17. Pointed Ends to reduce air resistance are util- ized in most elongated dirigible constructions, but probably have little if any advantage in this 90 VEHICLES OF THE AIR regard over hemispherical ends; besides which they are heavier and less strong. Rounded Ends, of exact hemispherical shape, are geometrically and mechanically the lightest, simplest, and most stable forms to resist the end pressures in cylindrical envelopes, while, as is sug- gested in the previous paragraph, there is no ground for supposing that they noticeably increase head resistances especially at such speeds as have been attained so far. Sectional Construction, though not altogether new, has been worked out in more detail and is more practically applied in the Zeppelin than in any previous airship. In the great balloons of this type see Page 96 and Figure 17 the sixteen or seventeen disk-like sections are entirely indepen- dent of one another, so that leakage from any one can not affect the others. The Effect of Size on balloon design is a subject concerning which there is much misunderstanding. It is asserted, for example, that doubling the dimensions of a balloon cubes its capacity while only squaring the areas of its surfaces. This is, of course, perfectly true, but the consequent rea- soning that this makes it possible to secure greater proportionate strength with each increase in size seems largely unwarranted. For, to maintain a proportionate strength, it is necessary to double the thickness of the surface material with the doubling in size, with the result that the quan- tity of material used is cubed, after all, just as the capacity is. Even at this, though, the strength 3 ~ ^ m t I * .3 a 3 O 5 a 2 *3 ** O 01 & * a 1 g . a .* -n s 5 a O> O fQ fl 35a|| S oa . M ' .PH 01 03 ^J j, S ^3 w a/ u "K "g ^ 2 S =5 " "' ~ , 3 ^ es - ^ "3 ^? ^ be u 5 5 P -9 >? ^ ^