j^ CONTENTS. 



PAr.E 



Hes^ilUfor the Horisontal Component of Magnetic Force — 



Secular Change, 



Annual Period, 



Differences of the Daily Means from the Monthly Means, 357 



Variations with reference to the Positions of the Moon, 358 



Diurnal Ranges; Annual Variation, 358 



Diurnal Ranges with reference to the Positions of the Moon, 360 



Diurnal Variation of the Horizontal Component, 361 



Ranges of the Mean Diurnal Variation, 363 



Variation with reference to the Moon's Hour- Angle, 364 



Intermittent Disturbances ; effect on the Yearly Mean, 365 



Intermittent Disturbances ; effect on the Monthly Means, 365 



Intermittent Disturbances ; effect on the Hourly Means, 366 



Mean Difference of a Single Observation from the Monthly Means ; Annual 



Variation, 



Mean Difference of a Single Observation from the Monthly Mean with reference 



to the Positions of the Moon, 369 



Mean Difference of a Single Observation from the Monthly Means ; Diurnal 



„ . ^. 370 



Variation, 



Number of Positive Differences ; Annual Variation, 371 



Number of Positive Differences ; Diurnal Variation, 371 



Mean Disturbance; Annual Variation, 371 



Mean Disturbance ; Diurnal Variation of Positive and Negative Sums, 371 



Mean Disturbance ; Diurnal Variation of Mean, 372 



Mean Disturbance ; Diurnal Variation of Positive and Negative Means, 372 



Number of Positive Disturbances ; Annual Variation, 372 



Number of Positive Disturbances ; Diurnal Variation, 372 



Note on the least probable Error of an Observation, •• 373 



Rmdtxfor the Vertical Component of Magnetic Farce — 



Secular Change, 374 



Annual Period, 374 



Differences of tlie Daily Means from the Monthly Means, 374 



Variations with reference to the Positions of the Moon, 375 



Diurnal Ranges ; Annual Variation, 376 



Diurnal Ranges \vith reference to the Positions of the Moon, 377 



Diurnal Variation of the Vertical Component, 379 



Ranges of the Mi^an Diurnal Variation, 381 



Variation with reference to the Moons Hour-Angle, 382 



Intermittent Disturbances ; effect on the Yearly Mean, 384 



Intermittent Disturbances ; effect on the Monthly Means, 384 



Intermittent Disturbances; effect on the Hourly Means, 384 



Mean Difference of a Single Observation from the Monthly Mean; Annual 



Variation, ^^^ 



Mean Difference of a Single Observation from the Monthly Mean with reference 



to the Positions of the Moon, 386 



