CONTENTS. 
T Page 
Introduction — 
Position and Description of the Observatory, 
System of Observation and Personal Establishment, . x i 
Magnetical Instruments — 
Declinometer — 
Description of the Declinometer, xii 
Values of the Scale Divisions, xiii 
Scale Reading for the Magnetic Axis, xv 
Correction for the effects of the Bifilar and Balance Magnets, xvi 
Correction for the effect of the Copper Ring or Damper, xvii 
Correction for the Non-Parallelism of the faces of the Plates of Glass in the Box, xviii 
Correction for the Torsion Force of the Suspension Thread, xviii 
Pacts relating to the Suspension Threads, xix 
Accidental Sources of Error xx 
Adopted Scale Zeros xxi 
Time of Vibration of the Declination Magnet ; xxi 
Absolute Magnetic Declination • • xxii 
Unifilar Magnetometer and Observations of the Absolute Horizontal Intensity of th< 
Earth's Magnetism — 
Position and Description of the Instrument, xxiii 
Mode of Observation and Reduction, xxiv 
Observations of Absolute Horizontal Intensity, xxvi 
Bifilar or Horizontal Force Magnetometer — 
Description of the Instrument, xxix 
Adjustments and Values of Constants, xxxi 
Constants for Reduction after altering the Reading of the Torsion Circle, xxxiii 
Corrections for the effects of the Declination and Balance Magnets, xxxiv 
Time of Vibration of the Bifilar Magnet, xxxiv 
Mode of Observation, xxxiv 
Temperature of the Magnet, - xxxiv 
Balance or Vertical Force Magnetometer — 
Description and Theory of the Instrument, xxxv 
Practical difficulties in Dr Lloyd's method of determining the Constants, " xxxvi 
New method of determining the Constants (Note), xxxvi 
Another method (that used in this volume) of determining the Constants, ■ • • • xxxvii 
Values of Constants and Adjustments, xxxviii 
Time of Vibration of the Balance Needle, xxxviii 
