INDEX 175 LIST OF ILLUSTRATIONS PAGE PLATE I. Comparative Altitudes 22 PLATE II. Optical Phenomena showing the Height of the Atmosphere 26 PLATE III. Temperature at different Latitudes and Altitudes 31 FIG. 1. Nephoscope at Blue Hill Observatory. 52 FIG. 2. Cloud Theodolite at Blue Hill Observatory 54 PLATE IV. Heights and Velocities of Clouds 57 PLATE V. Atmospheric Circulation at different Heights in Cyclones and Anti-cyclones 61 FIG. 3. German Balloon equipped for Meteorological Observations 87 PLATE VI. Temperatures observed in Four High Balloon Ascents 91 FIG. 4. German Kite-balloon. 95 FIG. 5. Baro-thermograph of Richard 102 FIG. 6. The _AÈrophile_ rising 103 PLATE VII. Heights and Temperatures recorded in eight Ascents of the _Cirrus_ 109 FIG. 7. Oriental tailless Kites. 119 FIG. 8. Eddy tailless Kite 129 FIG. 9. Hargrave Kite 130 FIG. 10. Modified Hargrave Kites at Blue Hill 133 FIG. 11. Lamson's Aero-curve Kite 135 FIG. 12. Meteorograph lifted by Kites at Blue Hill 138 PLATE VIII. Meteorogram from the Kite-flight of Oct. 8, 1896, at Blue Hill 148 PLATE IX. Mean Changes with Height, and Changes during the Kite-flight of Oct. 8, 1896 150 PLATE X. Changes with Height recorded by Kites at Blue Hill 155 PLATE XI. Kite Observations at Blue Hill, Sept. 5-11, 1897 163 PLATE XII. Automatic Records during a High Kite-flight at Blue Hill 166 PLATE XIII. Results of Kite-flights at Blue Hill during an Anti-cyclone and a Cyclone 168 SOUNDING THE OCEAN OF AIR ---------- CHAPTER I THE ATMOSPHERE--ANCIENT AND MODERN KNOWLEDGE--METHODS OF INVESTIGATION