266 Prof. Norton on Molecular Physics. 



rotation; and the current developed on the side nearest the 

 sun will run from west to east. East and west currents will 

 therefore be developed at every place during the greater part 

 of any single day, and the opposite current will originate only 

 during a certain interval of time before and after the middle 

 of the day. Also the east and west current will be more intense 

 than the opposite current developed in corresponding posi- 

 tions. At the close of a day, a certain resultant current for 

 each place should remain, running from east to west. As the 

 obliquity of the ecliptic to the meridian at the hour of noon 

 at any place is continually changing during the year, this result- 

 ant current must be continually changing its direction. This 

 change of direction may be represented by supposing the cur- 

 rent developed each day to lie in a small circle traced around the 

 point 90° from the ecliptic, on the meridian 90° from the station, 

 and that this magnetic pole is carried through the geographical 

 pole in the course of a year. Under this idea, each place will 

 have its separate oscillating magnetic pole. At the end of a 

 year these diverse directions of current will also have a result- 

 ant; and by considering contiguous places, it may be seen that 

 these annual resultants will lie for a certain district in parallel 

 small circles having a common pole. If we confine our atten- 

 tion to points on the equator, and suppose the magnetic proper- 

 ties of the crust of the earth to be the same at all points, it is 

 plain that every such pole will coincide with the geographical 

 pole, since the annual resultants would be coincident with the 

 equator. But should the conductibility of the earth be unequal 

 in different directions, the final currents developed in such direc- 

 tions should be unequal, and hence the annual resultants should 

 be variously inclined to the equator, and their poles have diverse 

 positions. At points situated without the equator the unequal 

 intensities of the currents developed at different seasons of the 

 year will determine at each locality an annual resultant having 

 a certain direction, generally more or less inclined to the equator. 

 In what precedes, we have confined our attention to the action 

 of the aether in directions tangential to the earth. Such currents 

 should be chiefly of the nature of galvanic currents — that is, pro- 

 ceeding from molecule to molecule. Those which result daily 

 from the combined effect of the two motions of the earth will 

 originate in lines parallel to the ecliptic, and follow the directions 

 (or at least in their mean course) of circles traced around the 

 position of the pole above mentioned, on the earth's surface, on 

 the day considered. These may be called ecliptic currents. The 

 currents due to the earth's rotation alone will be of a similar 

 character, and follow circles parallel to the equator. These two 

 sets of currents, especially the former, play the prominent part 



