GENERAL HEMARKS. 



527 



alternate increase and decrease of dip. Commencing with the 

 meridian of Greenwich, and proceeding eastwardly round the 

 hemisphere, we may distinguish the divisions as follows, in the 

 order of their geographical succession. 



1^^. South dip increasing. 



annually, 



St. Helena . . . . i754 to i775- • 6,9' 



Do 1775 to 1836.. 6,5 



Cape of Good Hope 1751 to 1775.. 7,2 



To this division also belongs Ascension ; but as the north end of 



the needle dips at that island, the change is north dip dimifiishing, 



instead of south dip increasing. 



annually. 



Cape of GoodHope i775 to 1836. . 6,t> 

 Mauritius . . . • 1754 to 1824. . 1,3 

 Do 1824 to 1836.. 0,8 



Ascension 

 Do. 



New Zealand 



1754 to 1775 

 1775 to 1836 



Otaheite 



Lima and Callao 

 Do. .. 



Valparaiso .. 



Concep9ion . . 

 Do. .. 



2d. South dip decreasing. 

 .. .. 1824 to 1835 .. 



3d. South dip increasing. 

 ,. .. c. 1775 to 1836 .. 



4^^. South dip decreasing. 



annually. 



6,3 annually. 

 7,2 



1,2 annually.* 



0,5 annually. 



1710 to 1799.. 0,4' 

 1799 to 1835.. 4,9 

 1794 to 1835 10,0 

 1710 to 1786.. 3,7 

 ] 786 to 1835.. 8,3 



Tierra del Fuego 

 Falkland Islands 

 St^ Catharina . . 

 Rio de Janeiro . . 

 Do 



annually, 

 1774 to 1828.. 8,0 

 1820 to 1834.. 8,2 

 1822 to 1827.. 8,4 

 1751 to 1817.. 4,8 

 1817 to 1832.. 4,3 



In the 2d and 3d divisions the annual change is small ; in the 

 1st and 4th considerably greater. It is greatest at the southern 

 station in South America ; the observations at Valparaiso, Con- 

 ception, Tierra del Fuego^ and the Falkland Islands, concur in 

 shewing it to exceed 8'. The observations at Ascension, St. Helena, 

 and the Cape of Good Hope, concur in shewing an annual change 

 in that quarter of the 1st division exceeding Q\ 



As the south dip decreases in South America, and increases in 

 Africa, it is obvious that somewhere intermediately the dip must 

 be stationary. Between Africa and New Zealand, for the same 

 reason, there must be a second locality so characterised. Between 

 New Zealand and Otaheite, a third ; and between Otaheite and the 

 west coast of South America, a fourth. Captain Fitz-Roy has 



* This is derived from the observations of Captains Duperrey and Fitz-Roy 

 at the Bay of Islands, in Lat. 35°. 16'. The interval is short ; but the indication 

 receives confirmation from the observations of Captains Cook and Vancouver at 

 Dusky Bay, New Zealand, in Lat. 45°. 47'. 



Cook .. .. 1773 .. 70°. 06' ) / , , 



Vancouver.. 1791 .. 43 5 ^'-4 annual decrease. 



