332 Mr. P. E. Chase on Gravity and Magnetic Inclination. 



portions of the globe, I have obtained the following results, which 

 serve to show the character of some of these modifications : — 



I. Declination. 



1. The currents manifest a tendency to follow the lines of most 

 direct ocean communication between the warmest and the coldest 

 portions of the globe, the general declination being westerly in 

 the Atlantic, and easterly in the Pacific Ocean. 



2. The lines of no variation are apparently determined in part 

 by the contours of the land* that divides the waters of the globe 

 into two great bodies. 



3. The currents are deflected by the southern pointed extremi- 

 ties of the several continents toward the east on the eastern shores, 

 and toward the west on the western shores, of New Holland, 

 Africa, and South America. 



4. The magnetic currents, in the three respects above enume- 

 rated, exhibit a precise parallelism to the ocean tidal flow. 



5. In the comparatively narrow belt of the Atlantic Ocean, the 

 declination between the parallels of 35° reaches 30°; in the 

 broad expanse of the Pacific, the maximum within the same 

 limits of latitude is 15°. 



6. Between the parallels of 70° and 80° the declination be- 

 comes very great, and the currents tend to a gyratory or cyclonic 

 motion, which appears to be modified by glaciers or local poles 

 of great cold. 



7. The cyclonic tendency is most marked in the southern 

 hemisphere, where the ocean waters experience the least inter- 

 ruption to their normal motions. Mr. FerrePs computation gives 

 " 28° 30' for the polar distance of the parallel where the surface 

 of the fluid or the stratum of equal pressure meets the surface 

 of the earth "f. It will be readily seen that at that distance the 

 south pole is entirely surrounded by water; and it seems there- 

 fore highly probable that, if there were no land in the frigid 

 zones, there would be no definite magnetic poles, but a simple 

 polar belt toward which the magnetic currents would flow in 

 parallel spirals J, except when deflected by land radiation, or 

 tidal or other gravitation-currents. 



Evans's English Admiralty Chart for the United States Coast Survey Re- 

 port of 1859, and Nos. 1 and 2 of the ' Admiralty Manual for ascertaining 

 and applying the deviations of the Compass caused by the iron in a ship/ 

 second edition, 1863. 



* The influence of coast-lines in producing a tendency to equality of de- 

 clination is beautifully shown in the United States Coast Survey Chart of 

 " Lines of equal Magnetic Declination on the Gulf of Mexico for the 

 epoch 1860-0." 



t hoc. cit. 



X This inference accords with Barlow's conclusion, that every place has 

 its particular polarizing axis. 



