hy Alexander von Ilumholdt. xix 



that this pomt of intersection had already shifted four 

 degrees to the westward. A period of twenty years having 

 elapsed since Sabine's expedition for determining observa- 

 tions with the pendulum, it would be most desirable that 

 fresh investigations should be made in that neighbourhood, 

 for the purpose of verifying the secular changes of all 

 magnetic curves, especially with regard to their variation. 

 In 1840, the line of no declination in America began 

 9° 30' E. of South Georgia, whence it ran to the S.E. coast 

 of Brazil, near Cape Frio, thus traversing the mainland of 

 South America only between the latter point and the parallel 

 of 0° 36' S., when it leaves the continent a little to the east 

 of Gran Para, near Cape Tigioca, cutting the terrestrial 

 equator again, but in 50° 6' W. According to Bache's Map 

 of Equal Magnetic Declination, it reaches the coast of North 

 America near Cape Fear, to the south-west of Cape Look- 

 out. This line, along which the magnetic declination is nilj 

 extends to a point in Lake Erie, 2° 40' W. of Toronto, 

 where the declination is already V 2T W* 



It is evident from the observations of Captains Beechey and 

 Findley, and still more particularly from those of the French 

 Captain Kerhallet, that the remarkable subdivision of the 

 main equinoctial current, flowing from east to west into two 

 branches, one directed to the N.W., the other to the S.S.W., 



* Wlierever, in tliis paper, it is not precisely expressed' to the contrary, 

 tlie scale of the Centigrade Thermometer, the longitude from the Meridian of Paris, 

 the French foot {pied du ro/=12'79 inches Enghsh), and the geographical mUe, 

 15 to a degree of the Equator, measuring 3807 " toises," are meant. 



6 2 



