Archæological surveys offer a fascinating opportunity for airplane or dirigible balloon photography to render scientific service. Buried in desert sands or overgrown with tropical vegetation the ancient cities of Asia Minor, of Burma, and of Yucatan evade discovery, and even when found remain unmapped for decades. Discovery and mapping can now go hand-in-hand. The topography of barbaric or colonial towns and villages, whose importance could not warrant elaborate surveys, but which should nevertheless be a matter of record, will be quickly and easily plotted by photography (Fig. 207). To this day who knows how the streets run in Timbuctu, and how, save from the air, can we ever map the teeming cities of China? He who would follow in the footsteps of Haroun-al-Raschid can even now explore the by-ways of Bagdad by the aid of the Royal Air Force photographic map! INDEX Aberrations, lens, 47, 54 Aberration, spherical, 47, 54 chromatic, 48, 54 Acetylene light, 284 Advertising, use of aerial photography in, 392 Aero 1 and Aero 2 filters, 241 Airplane, as camera platform, =20= types of, 24 Air speed, 27, 308 indicator, 33, 34 Alcohol, use of in plate drying, 275 use of in print drying, 286 Altimeter, 33, 174 reading recorded on film, 135, 171 Altitudes of flight for photography, 61, 224 Anastigmatic type of lens, 47 Aperture, lens, 39, 44, 56, 57 Archæological surveying, 413 Astigmatism, 49, 50, 54 Auxiliaries, camera, =163= installation of, 214 Bagley camera, 286, 314 Balance, of camera, 96 of plane, 157, 208, 217 Balloons, 15, 16, 18 Banking, 27, 324 Batteries, storage, 150, 156 Bay, camera, 120, 210 Bellows, camera, 65, 95 Biplane, 24 Blast marks in front of guns, 363 Bleaching out print to leave interpretation marks, 367 Boat, flying, 25, 374 Bowden wire, 103, 106, 108, 111, 114, 116, 118, 126, 129, 136, =163= Brightness, range of, 221, 225 Burchell photographic slide rule, 303, 339 Camera, airplane, =39=, 384 automatic, 18, 43, 90, 116, =124=, 125, 311 B. M., =120=, 203 Bagley, 286, 314 Brock automatic plate, =126= C type, 43, 87, 103, =109= classification of, 43 deMaria, 86, 89, 103 deRam, 82, 93, =121=, 129, 157, 205, 214, 326 E type, 43, 87, 103, =109= elements of, =42= film, _see_ Film cameras Folmer automatic plate, =126= hand held, =95=, 321, 369 English, =99= German, =99= U. S. Air Service, =100= Ica, =103= Lamperti (Italian), =112=, =211= L. B., =120= long focus, 103, 301, 324 L type, 43, 82, 94, 102, =117=, 162, 210 M., =106=, 203 non-automatic, 43, =102= Piserini and Mondini, =111= semi-automatic, 43, =116=, 149 stereoscopic, 341 Camouflage, filters for the detection of, 225, =243= stereoscopic views and, 329, 358 Ceiling of plane, 27, 130 Channels, detection of by photography, 408 Chemicals, photographic, =257=