CONTENTS. 
IntTRopucTION— fa 
Position and Description of the Observatory,---++++-+-++++rs+rssssreseeeeeseenneeeeeeeses cence: ix 
System of Observation and Personal Establishment, -----+-++++-++sesseeeseeeeeeneee ere eeeees xi 
Maeneticat [nstRUMENTS— 
Declinometer— 
Description of the Declinometer, xii 
Values of the Scale Divisions, -----++-++++++++++seeese tee tee ten sen tease ceeseesneereneeees xiil 
Scale Reading for the Magnetic Axis,.-.-+-+-+++seeeeeennsrerteceneeeessenestesceenen ees XV 
Correction for the effects of the Bifilar and Balance Magnets, -------+-++++++--+-+- xvi 
Correction for the effect of the Copper Ring or Damper, --------++++++++r++-++0-0+ 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 
Facts relating to the Suspension Threads, ---++--+-++++-++-sseereererreeeseeeee tenons xix 
Accidental Sources of Error xx 
Adopted Scale Zeros-.s:ssesesseeeecnees sree eee enerec eee Coe Se non nsedkubes acct sascucdcosr tes Xxi 
Time of Vibration of the Declination Magnet xxi 
Absolute Magnetic Declination ----.------+- Seo RO LURE ERO AEGOSaES abr Boss negecenne 2 xxii 
Unifilar Magnetometer and Observations of the Absolute Horizontal Intensity of the 
Earth's Magnetism— 
Position and Description of the Instrument, «---+-1--++++seeeretreeceeseseeeeeteetes xxiii 
Mode of Observation and Reduction, ---------+++-++-+ Micatle csieesieus/aciclemeoapmeuianesies(sin XXiv 
Observations of Absolute Horizontal Intensity, xxvi 
Bifilar or Horizontal Force Magnetometer— 
Description of the Instrument,-------0++-:eeeeeeece eee eee ene eee reece cere re ees castasateso XxXix 
Adjustments and Values of Constants, --+++--+--eereeesee teense eee eeeneecuseeereneeeees XXxi 
Constants for Reduction after altering the Reading of the Torsion Circle,--.--- xxiii 
Corrections for the effects of the Declination and Balance Magnets, ------------ XXXiV 
Time of Vibration of the Bifilar Magnet, xxxiv 
Mode of Observation,----+--++s:+ss+0scerreeeteeeeesecea tes eseaerseeseeeecaeeaeeccueneeseces XXxXiv 
Temperature of the Magnet,--+--++-+++s+sssescessescersereesseeersceeeeeneeens Scere Racoon xxxiv 
Balance or Vertical Force Magnetometer— 
Description and Theory of the Instrument, ------:00sseseeeee eee eee ec teee eee eeees aces XXXV 
Practical difficulties in Dr Luoyn’s method of determining the Constants,----- XXXVi 
New method of determining the Constants (Note), -----++-+++++se+--+s1rseeerseen ees XXXVI 
Another method (that used in this volume) of determining the Constants, ----  XXxvil 
Values of Constants and Adjustments, 
Time of Vibration of the Balance Needle, -------++-+-+++-+++erees-serecnerereeeaeeees XXXVili 
