GENERAL REMARKS. 



525 



of the curves from all sides towards the centre^ by which the areas 

 severally comprehended by them become less ; and the lower varia- 

 tions^ as they successively reach the centre, disappear, and are 

 replaced by the closing-in of those of next higher amount. The 

 changes which have taken place at all Captain Fitz- Roy's stations 

 comprised within the space referred to, are accordant with the 

 systematic alteration thus described. 



In all other parts of the hemisphere the lines of variation have 

 a progressive westerly movement, and to this also Captain Fitz- 

 Roy's observations correspond. 



It follows, from what has been stated, that the lines on the 

 western side of the concentric system in the South Pacific have an 

 eastward movement, which presents an apparent anomaly to the 

 general progress of the lines of variation in the southern hemis- 

 phere, which is from east to west. 



Otaheite, and the Bay of Islands in New Zealand, present exam- 

 ples of changes in the variation corresponding to this apparent 

 anomaly. The consistency, however, both of the movement and of 

 the configuration of the lines of variation in this quarter, with 

 those in other parts of the southern hemisphere, and with the 

 general system of the magnetic phenomena, has been shewn by 

 Mr. Hansteen in the Magnetismus der Erde, and in the Annalen 

 der Physik, vol. xxi. 



The annual amount of the change of the variation appears con- 

 siderably greater at the Cape of Good Hope and Mauritius than 

 at any other of Captain Fitz- Roy's stations, amounting to about 

 eight minutes ; shewing that the variation lines in that quarter are 

 changing their position more rapidly than elsewhere. The north 

 pole of the needle is moving to the west at the Cape, and to the 

 east at Mauritius ; but it will be seen, by a reference to the map, 

 that these opposite movements are in perfect correspondence 

 with the uniform westerly progression of the variation lines, and 

 result from their configuration. 



At the stations in the vicinity of the meridian of 65*^ west, the 

 change appears to be very small. 



[The variation at Ascension (13° 30' W.) is correctly inserted in the 

 tables : it is the only one of Captain Fitz-Roy's stations at which his 

 observations are not accordant with those of other observers : the dis- 

 cordance may be occasioned by the great prevalence of local disturbances 

 at Ascension.] 



