512 EDITOR'S NOTES. 



each other. There seems reason to believe that the general 

 characters of the regular solar-diurnal variation, in regard 

 to the hours of its easterly and westerly extremes, are 

 the same in all the extra-tropical portions of the same 

 magnetic hemisphere ; whilst in the case of the disturb- 

 ance-variation, it seems probable that every diversity 

 in the times of occurrence of the turning-hours may be 

 found in different localities. The stations at which 

 these laws have been elicited are not yet sufficiently 

 numerous and varied to afford sufficient indication of 

 the mutual connections, or of the geographical or mag- 

 netical relations, which may possibly hereafter be traced 

 and throw additional light on the nature of the causes 

 concerned. The easterly and westerly disturbance- 

 deflections at the same station have also distinct laws oi 

 diurnal variation, which appear to have no necessary 

 or determinate relation to each other, and are only to 

 be learnt, like their conjoint effects, by examination. 

 The determination of these effects with a view to their 

 elimination, is a first step towards a true presentation of 

 the phenomena of the regular diurnal^variation, inas- 

 much as prior to such determination we cannot antici- 

 pate, with any degree of certainty, at what hour of the 

 twenty-four either the easterly or the westerly extreme 

 disturbance-deflection may be found : nor, in reference to 

 the comparative magnitude of the disturbance-variation 

 and the variation from other sources upon which it is 

 superposed, can we with confidence affirm more than 

 that the disturbance-variation may be expected to be 

 smallest at magnetically equatorial stations, quite suffi- 

 ciently large in the middle latitudes to exercise fre- 

 quently a very perplexing influence on results from 



