vi CONTENTS. 
NO. PAGE 
Horizontal Component of Magnetic Force — 
Horizontal Component in Absolute Measure, 48 ' xxx 
Secular Change from Observations of Absolute Measure, 49 xxx 
Mean Values of the Variations of the Horizontal Component 51 Tyyi 
Comparison of the Secular Change from Observations of Absolute Measure 
with that from Observations of the Bifilar Magnetometer, 53 xxxii 
Effect of Disturbance on the Mean Value, 54 xxxii 
Secular change employed in Deducing the Annual Variations, 55 xxxii 
Aimual Variations — 
Mean Horizontal Component, 56 xxxii 
Foot-note on the Annual Period Deduced from the Observations at Toronto 
and Munich, xxxii 
Effect of Disturbance on the Monthly Means, 57 xxxiii 
Mean Horizontal Component from Undisturbed Days, 58 xxxiii 
Differences of the Daily Means from the Monthly Means, 59 xxxiv 
Diurnal Ranges, 60 xxxv 
Ranges of the Monthly Mean Diurnal Variation, from all the Observations 
and from Selected Days, 61 xxxv 
Mean Difference of an Observation from the Monthly Mean, 63 xxxv 
Probable Error of an Observation of the Horizontal Component, 64 xxxvi 
Number of Observations greater than the Monthly Mean, 65 xxxvi 
Monthly Variations — 
Mean Horizontal Component, 66 xxxvi 
Diurnal Ranges, 67 xxxvii 
Mean Difference of an Observation from the Monthly Mean, 68 xxxvii 
Diurnal Variations — 
Results from all the Observations, for each Month, 69 xxxviii 
Results from all the Observations, for Groups of Months, 70 xxxix 
Results from Undisturbed Observations, for Groups of Months, 71 xl 
Effect of Disturbance on the Hourly Means, 72 xl 
Frequency of Positive and Negative Departures from the Hourly Mean 
Positions, 74 xlii 
Mean Difference of an Observation from the Hourly Mean Position for 
each Hour, 76 xlii 
Probable Error of an Observation from the Monthly Mean, 78 xliv 
Variations with reference to the Moon's Hour-Angle, 79 xliv 
Vertical Component of Magnetic Force — 
Vertical Component in Absolute Measure, 81 xlv 
Adjustment of Balance Magnetometer in different Years, 82 xlv 
Yearly Means of the Variations of the Vertical Component with the Secu- 
lar Change, 83 xlvi 
Effect of Disturbance on the Yearly Mean, 85 xlvi 
