CONTENTS. 



Page 



Introduction — 



Position and Description of the Observatory, ix 



System of Observation, and Staff of Observers, x 



Declinometer — 



Description of the Declinometer, - xi 



Values of the Scale Divisions, xii 



Scale Readings for the Magnetic Axis, • xiii 



Corrections, xiii 



Removal of Torsion, &c, xv 



Time of Vibrati on, xvi 



Method of Observation, xvi 



Absolute Magnetic Declination, xvi 



Unifila/r Magnetometer and Observations of the Absolute Horizontal Intensity of the Earth's 

 Magnetism — 



Position and Description of the Instrument, xix 



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



Results of Observations, xxvi 



Bifilar or Horizontal Force Magnetometer — 



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 Instrument, xxxiv 



Usual formula of Reduction, xxxv 



Times of Vibration, xxxv 



Conclusions from the observations of the Tim e of Vibration, xxxix 



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



Insufficiency of the usual formula, xiii 



Observations for a statical determination of the Balance Coefficient, xiii 



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



Method of Observation, xlv 



a 



