REPORT OP THE KEW COMMITTEE. H 



1st Section contained a Tabular Synopsis of ninety-five of the principal dis- 

 turbances of the Declination recorded by the Kew photograms from January 

 1858 to December 1862, with a comparison of the Laws of the Distui-bances 

 derived therefrom with the Laws derived by the more usual method then 

 practised. The tabular summary at the close of Section 1 shows the result- 

 ing aggregate values both of Easterly and of "Westerly disturbance at each 

 of the 24 hours (or at 24 equidistant epochs) in each of the five years, as 

 well as in the whole period. It is strictly a tabular detail for the period in 

 question, showing the Disturhance-cliurnal Variation as it would result if the 

 investigation were limited to the 95 most disturbed days, and may be con- 

 sidered to represent the mode of investigation then practised by some mag- 

 neticians. 



The 2nd Section of the paper compared the Laws of the Disturbances thus 

 obtained with the Laws derived from a wider selection of disturbed obser- 

 vations ; i. e. a selection including eveiy anomalous record of which the ano- 

 malous character cannot with probability be ascribed to any other source than 

 that of the disturbing action whose laws are sought. This Section is also 

 accompanied by a tabular statement in full detail ; and from an examination 

 of the contents of the 1st and 2nd Sections the following conclusions arc 

 drawn : — 



1. That the disturbances have systematic laws : 



2. That both easterly and westerly deflections have eacli their own 

 systematic laws, distinct and different each from the other : 



3. That the laws are approximately the same, whether derived from the 

 more limited or the more extended selection, though the latter com- 

 prises three times as many cases of disturbance as the former. 



Hence it is inferred that, by taking into account only the most notable 

 days of disturbance (as was then the practice of some magneticians), an 

 approximately correct view of the disturbance-diiu-nal variation may be ob- 

 tained ; but, if we desire to eliminate the influence of the distiu'bances on 

 the diurnal variation due to other causes, the more comprehensive method 

 must be adopted. 



A selection of this latter character was then made for the five years 1858 

 to 1862, and the results exhibited, both in tabular and graphical represen- 

 tations ; and the laws derived therefrom were compared with corresponding 

 investigations in other parts of the globe. 



In the 4th Section of the paper is discussed the " Diurnal Inequality," 

 comprehending 1°, the disturbance-diurnal variation, and 2°, the undisturbed 

 solar-diurnal variation. This discussion may be regarded as exhibiting what 

 should be ih.Q primary step in the analysis of the periodical variations. 



The solar-diurnal variation derived from the record of the five years at 

 Eew, 1858 to 1862, is then compared with solar-diurnal variations similarly 

 obtained at Toronto, Nertschinsk, Pekin, St. Helena, the Cape of Good 

 Hope, and Hobartou ; and the several points of agreement or difference are 

 discussed. 



In the same 4th Section, the semiannual inequality which is seen to exist 

 at all the stations enumerated above is discussed, and is shown to manifest 

 a solar influence, evidenced by the diiferences exhibited in different parts of 

 the globe. 



In Section G the Lunar-diurnal Variation derived in each of the five years 

 at Kew is deduced and discussed. 



In Section 7 the Secular Change and Annual Variation of the Declination 



d2 



