CONTENTS. xv 



SECTION XI. 



ON THE CONTINUOUS REGISTRATION OF SMALL CHANGES IN 

 TERRESTRIAL MAGNETISM. 



Articles 8387. Pages 189-206. 



ART. PACK 



8J. General principle of photographic self- registration, now usually 

 adopted. Distinction of the magnetic elements which are 

 to be registered, and appropriate positions of the recording 

 apparatus 189 



8 t. Kecord of the small changes of magnetic declination, and 



evaluation of their scale 191 



85. Bifilar magnetometer for record of the small changes of mag- 



netic horizontal force, and evaluation of their scale . .192 



86. Balance-magnetometer for record of the small changes of mag- 



netic vertical force, and evaluation of their scale . . .198 



87. Results obtained from the continuous registers of small changes 



in terrestrial magnetism ....... 202 



SECTION XII. 



ON THE RELATION BETWEEN GALVANIC CURRENTS AND MAGNETIC 

 FORCES; AND ON THE REGISTER OF TERRESTRIAL GALVANIC 

 CURRENTS, WITH SPECIAL REFERENCE TO DISTURBANCES OF TER- 

 RESTRIAL MAGNETISM. 



Articles 88- 91. Pages 207 220, 



88. Fundamental principles of the creation of a galvanic current, 



and of its magnetic action ; application to the galvanometer 

 and to the speaking-telegraph ...... 207 



89. Inductive magnetic power of the galvanic current; its action 



on steel and on iron : formation of transient magnets ; regis- 

 tering-telegraphs . . . .211 



90. Spontaneous terrestrial galvanic currents.; investigation of the 



magnetic effects due to them, and comparison of those mag- 

 netic effects with the magnetic disturbances recorded by tho 

 self- registering magnetometers 214 



91. Note on thermo-electric or thermo-galvanic currents, and on 



their possible connexion with terrestrial magnetism . . 218 



