CONTENTS. 



Page 



Preface, vii 



Introduction — 



Description and Position of the Observatory, ix 



Personal Establishment, x 



Magnetical Instruments — 



Declinometer — 



Description of the Declinometer, xi 



Value of the Scale Divisions, xii 



Reading for Magnetic Axis, xiii 



Effect of Bifilar and Balance Magnets, xiv 



Effect of Copper Ring, xv 



Suspension Thread and its Torsion Force, xvi 



TT 



Values of -"> - xvi 



Facts relating to Suspension Threads, xvii 



Absolute Declination, xix 



Method of Observing, xxiii 



Bifilar Magnetometer — 



Description of the Instrument, • xxiii 



Constants for the Reduction of Observations after altering the Reading of the 



Torsion Circle, xxv 



Adjustments, xxv 



Value of Scale Divisions, xxvi 



Times of Vibration, xxviii 



Mode of Observing and Reductions, xxix 



Values of k and q, xxx 



Sources of error in determining the Temperature of the Magnet, xxx 



Absolute Horizontal Intensity, xxxi 



Balance Magnetometer — 



Description of the Instrument, xxxii 



Value of Micrometer Divisions, xxxiii 



Deviation of Magnetic Axis from the line joining the Bisection Crosses, xxxiv 



Times of Vibration in a Horizontal Plane, •' xxxv 



Times of Vibration in a Vertical Plane, xxxvi 



Effect of other Magnets, ^ xxxvii 



Observations and Reductions, • xxxvii 



Values oik and q, xxxix 



