﻿228 Prof. W. A. Norton on the Corona seen 



their known physical relations to the sun's spots. This theory 

 of the origin of the diverse perturbations of terrestrial mag- 

 netism I have elaborated, and followed out into a detailed 

 discussion of the variations of the"* different magnetic elements, 

 in former Numbers of Silliman's Journal (viz. for March and 

 July, 1855). 



We may add that it derives additional support from the 

 general result arrived at by Professor Chambers, in his discussion 

 of the " Nature of the Sun's Magnetic Action/' viz. that " the 

 mode in which forces originating in the sun influence the mag- 

 netic condition of the earth is not analogous to the action of a 

 magnet upon a mass of soft iron placed at a great distance from 

 it, but that these forces proceed from the sun in a form different 

 from that of magnetic force, and are converted into this latter 

 form of force probably by their action upon the matter of the 

 earth or its atmosphere." If this be admitted, then we must 

 conclude that the perturbations of the earth's magnetic con- 

 dition, as evinced by the variations of the position and 

 directive force of the magnetic needle, must result either from 

 some action, direct or indirect, on the earth or its atmosphere, of 

 some form of matter emitted from the sun, or from a wave- 

 action propagated from the sun, or from both of these operative 

 causes combined. 



(4) The streamers of the corona should have at different 

 points of the sun's photospheric surface different directions, 

 parallel to the diverse directions of the magnetic force of the 

 sun at this surface. These directions should be variously 

 inclined, in different heliographic latitudes, to the horizontal 

 lines at the points of the surface, and also to the plane of the 

 sun's equator ; like the dipping-needle on the earth and the 

 streamers of a terrestrial aurora. In low latitudes the angles of 

 inclination to the plane of the equator should be large ; and the 

 streamers proceeding from corresponding points in the two 

 hemispheres should converge and intersect in the plane of the 

 equator. In proportion as these corresponding streamers 

 proceed from points more remote from the sun's equator, they 

 will intersect under a smaller angle, and their point of inter- 

 section will be more distant from the sun's surface, until at the 

 heliographic latitude of 30° to 35° they will become parallel to 

 the plane of the equator. Those emanating from still higher 

 latitudes will diverge from the plane of the equator and from 

 each other*. 



; If these facts be attentively considered, it will be seen that 

 the result should be the formation of a luminous appearance 



* It is here assumed that the magnetic equator of the sun is coincident 

 with his heliographic equator. 



