CONTENTS. 



Introduction — 



Position and Description of the Observatory, '" 



System of Observation, and Staf of Observers, '^ 



Declinometer — 



Description of tlie Declinometer, ^^ 



Values of the Scale Divisions, xii 



Scale Readings for the Magnetic Axis, xiii 



Corrections, ^"^ 



Removal of Torsion, &c., ^^ 



Time of Vibration, x'" 



Method of Observation, ^'^ 



Absolute Magnetic Declination, ^"^^ 



Unifilar Magnetometer and Observations of the Absolute Horizontal Intensity of the Earth's 

 Magnetism — 



Position and Description of the Instrument, six 



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



Results of Observations, xxvi 



Bijilar or Horizontal Force Magnetometei — 



Description of the Instrument, xxvii 



Usual formula of Reduction, xxviii 



New formula of Reduction, xxix 



Determinations of the Coefficient of Reduction, xxx 



Coefficients applicable to the observations since 1841, xxxii 



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



Time of Vibration of the Bifilar Magnet, xxxiii 



Mode of Observation, xxxiii 



Balance or Vertical Force Magnetometer — 



Description of the Instnunent, xxxiv 



Usual formula of Reduction, xxxv 



Times of Vibration, xxxv 



Conclusions from the observations of the Time of Vibration, xxxix 



Observations to discover the causes of the anomalies in the Time of Vibration, xl 



Insiifficiency of the usual formula, xlii 



Observations for a statical determination of the Balance Coefficient, xlii 



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



Method of Observation, xlv 



a 



