Besides lifting the meteorological instruments described, kites can carry apparatus for other investigations in the free air, such as the measurement of atmospheric electricity, and the collection of samples of air, to be examined for cosmic dust and bacteria. Cameras have been lifted by kites, as already said, and for the purpose of photographing the upper surfaces of clouds there is being constructed for the Blue Hill Observatory a very light automatic camera, similar in principle to M. Cailletet's apparatus for photographing the ground from a balloon. The use of the kite as an aeroplane can only be alluded to in this book, and it may be sufficient to say that if a motor attached to a kite can, by wings or screws, propel it against the wind, the sustaining string is unnecessary, and we shall have the flying machine which Professor Langley tells us will soon be realized. The surface of our globe has been tolerably well explored; the exploration of the atmosphere by balloons and kites will continue to make great progress during the last year of the century, and at the end of the twentieth century we may confidently expect that as the seas now are a medium for transportation, so the ocean of air will have been brought likewise into man's domain. INDEX A Abercromby (R.), classification of clouds, 42 Academy of Sciences, French, 18, 72-3 Academy of Sciences, Russian, balloon ascent, 72 Accademia del Cimento, 14 Actinometer, ViollÈ's, 115 Adiabatic rate of change of temperature, 29 Aeronautical Conference at Chicago, 125 ---- Conference at Strassburg, 97, 110 ---- Committee; International, 108 _AÈrophile_ balloons, 102, 104 Aerostatic Commission, French, 111 Air, collection and analysis of, 70, 73, 75, 82, 112 ---- weight of, 16 Aitken (J.), dust particles, 39 Alhazen (B. A.), height of atmosphere, 12 Altitudes, comparative, 20 AndrÈe (S. A.), balloon voyage to North Pole, 90 Anti-cyclones, 59, 170 Aratus, _Diosemeia_, 11 Archibald (D.), kites for meteorological observations, 122 Archytas, supposed inventor of kite, 117 Aristotle, 10, 11, 15 Assmann (R.), 86, 94, 108 Atmosphere, composition of, 24 ---- energy of upper portion, 58 ---- extent of, 28 ---- methods of exploring same, 35 _et seq._, 145 ---- moisture of, 34 ---- origin of, 23 ---- phenomena showing height of, 26 ---- Pliny on, 9 ---- temperature of, 28 Atmospheric circulation in cyclones and anti-cyclones, 60 ---- electricity, 70, 76, 121, 141 B