List of Illustrations 



PAGE 



Welwitsch's Bat . . . .16 



Plate 1. Vertical Central Section of the Apparatus for 



Producing the Vibrations 36 



Plate 2. Side Elevation of the Siren or Vibrator . . .37 



Plate 3. Receiver that Makes and Breaks Electrical Circuits 



for Ringing Bells 39 



Plate 4. Receiver for Recording the Vibrations . . 40 



Plate 5. System of Mounting the Receivers . . . .41 

 Iceberg in the South Pacific ....... 44 



