CONTENTS. 



Page 



Introduction — 



Position and Description of the Observatory, ix 



System of Observation, and StaJ^ of Observers, xi 



Declinometer — 



Description of the Declinometer, xii 



Values of the Scale Divisions, xiii 



Scale Readings for the Magnetic Axis, xiv 



Corrections, xiv 



Removal of Torsion, &c., • xv 



Time of Vibration, xvi 



Method of Observation, xvi 



Absolute Magnetic Declination, xvi 



Unijilar Magnetometer and Observations of the Absolute Horizontal Intensity of the Ea/rth's 

 Magnetism — 



Position and Description of the Instrument, xix 



Formula of Reduction, methods of Observing, &c., xx 



Results of Observations (see Addendum). 



Bifilar or Horizontal Force Magnetometer — 



Description of the Instrument, xxv 



Usual formula of Reduction, xxvii 



New formula of Reduction, xxvii 



Determinations of the Coefficient of Reduction, xxviii 



Coefficients applicable to the observations since 1841, xxxi 



Constants for Reduction after turning the Arms of the Torsion Circle, xxxi 



Time of Vibration of the Bifilar Magnet, xxxiii 



Mode of Observation, xxxiii 



Balance or Vertical Force Magnetometer — , 



Description of the Instrument, xxxiii 



Usual formula of Reduction, xxxiv 



Times of Vibration, • xxxv 



Conclusions from the observations of the Time of Vibration, xxxvi 



Observations to discover the causes of the anomalies in the Time of Vibration, • • • • xxxvii 



Insufficiency of the usual formula, xxxix 



Observations for a statical determination of the Balance Coefficient, xl 



Adjustment of the Balance, and connection of the Observations, xlii 



Method of Observation, xliii 



The Temperature Coefficients of the Deflecting, Balcmce, and Bijilar Magnets — 



Temperature Coefficient of the Deflection Magnet, xliii 



Coefficient Constant for High and Low Temperatures, xliii 



Temperature Coefficient of the Bifilar Magnet by hot- water experiments, xliv 



Coefficient Constant for High and Low Temperatures, xliv 



h 



