LIST OF ILLUSTRATIONS. 



Facing 

 page 



Pi,aTE I. A and B. Two views of reef off Loggerhead Lighthouse as seen at extreme 

 low tide on June 6, 1910. Heads above water are Orbicella annu- 

 laris. The alcyonarian Rhipidogorgia Habellum and Plexaura sp. are 

 also shown 142 



C and D. Two views of storm-proof live-car in which the tiles bearing 

 attached planulae were planted. 



C, before launching, showing how tiles are fastened. 



D, after launching, showing its appearance in water. 



Plate 2. One-Hundred-and-Fifty-Foot Tower Telescope on Mount Wilson, Octo- 

 ber 1910 156 



Plate 3. Ha Flocculi around spots of the Bipolar type 160 



Plate 4. Spiral Nebula Messier 51 Canum Venaticorum 168 



Plate 5. Magnetic Work of Department of Terrestrial Magnetism, 1905-1910 204 



VII 



