1 82 Mr. Henry Wilde on 



well-defined lines of no declination in the northern hemi- 

 sphere, for two similar lines of no declination in the southern 

 hemisphere. The declination also varies very considerably 

 for equal latitudes and longitudes in the northern and 

 southern hemispheres, for the same or for different epochs. 

 This is seen in the large amount of the declination at the 

 Cape of Good Hope, and the small amount on the great 

 land areas of Eastern Europe and Asia, as well as over 

 the Eastern States of North America. The comparatively 

 small area, or oval, of westerly declination in Eastern 

 Asia, surrounded by considerable areas of easterly variation, 

 together with the closed curve of small easterly variation in 

 the equatorial parts of the Pacific, contributes still further 

 to increase the difficulty of the problem of reducing the 

 distribution of the earth's magnetism to general laws. 

 The unsymmetrical character of the lines of equal variation, 

 and the devious courses of the lines of equal inclination and 

 the magnetic equator, are no less perplexing to magneticians 

 than the irregularities of the declination at different epochs 

 for equal latitudes. 



In the course of my experiments, it was noticed that the 

 lines of no declination of the internal sphere of the magnet- 

 arium were generally in advance of those on the charts for 

 a given epoch. Thus the two antartic lines of no declination 

 were more than 40° east of the similar lines of the electro- 

 dynamic sphere for the epoch 1880. 



With the object of ascertaining what influence the 

 configuration of the surfaces of the terrestrial globe, as 

 indicated by the general distribution of land and water, 

 had on the magnetic elements, the ocean areas of the outer 

 globe of the magnetarium were covered with thin sheet 

 iron roughly contoured to the coast lines in both hemi- 

 spheres. On turning the internal electro-dynamic sphere 

 84 W. to correspond with the epoch 1880, a remarkable 

 change in the magnetic elements was manifested. The two 



