Coast Lines and Magnetic Declination. 183 



lines of no declination in the southern hemisphere of the 

 outer globe were nearly coincident with those on the chart ; 

 and in the northern hemisphere four zero lines appeared 

 similarly coincident ; two of which lines on the North 

 American and European continents were continuations of 

 those in the southern hemisphere. But the most remark- 

 able and unexpected feature of the distribution of the 

 magnetism on the iron-covered globe was the reproduc- 

 tion of the oval area of small westerly declination in 

 Eastern Asia (uo° — 160° E.), surrounded by large areas 

 of eastern declination. The oval also agreed in detail with 

 that on the chart in having the largest westerly declination, 

 about 8° in the centre, between the lines of no declination. 



Scarcely less interesting was the unlooked-for reproduc- 

 tion of the oval area of small easterly declination, about 5 , 

 surrounded by a large area of greater eastern declination 

 in the equatorial parts of the Pacific (120 — 170 W.), while 

 the unsymmetrical form of the magnetic equator was very 

 similar in its deviations to that of the earth for the epoch 1880. 



Further experiments with the iron-covered globe showed 

 that the land areas, besides retarding the translatory 

 movement of the lines of the declination, generally diminished 

 the amplitude of the declination itself, and to a greater 

 amount as the broad features of the continental coast lines 

 extended more or less in a direction parallel to the earth's 

 equator. 



On the other hand, continental coast lines extending 

 more or less parallel to the earth's axis and terminating in 

 capes or headlands, diminish the horizontal force, and, 

 consequently, increase the rate and range of the declination ; 

 as instanced : — (1) In the large amount of the secular change 

 along the South African coasts, where at the Cape of Good 

 Hope the declination is 30°W. (2) On the South American 

 coasts about Cape Horn, 20°E. (3) On the Greenland coasts 

 at Cape Farewell, 5<D°W. (4) The coasts of Southern India 



