1891. | VEEDER—ON THE ZODIACAL LIGHT. 143 
almost exactly equal to the inclination of the latter to the plane of 
these extensions of the corona. Induction at this angle, continued 
through long series of years, seems to have established the latitude of 
the magnetic poles, their location in longitude being determined, 
perhaps, by the magnetic properties of the materials of which the earth 
itself is composed. 
Changes in the sub-permanent magnetism of the coronal exten- 
sions, resulting from the variability manifest in the sun, necessarily 
cause slow variations in the strength and location of the permanent 
magnetic poles. Thus the well known secular variations of declination 
and magnetic dip become explicable. Changes in the temporary mag- 
netism of these same coronal conducting discs, such as must exist 
during magnetic storms, will on the other hand, occasion the induction 
of temporary magnetic poles in the same latitude as the permanent 
poles, but undergoing a diurnal change of longitude. The inductive 
effect is exercised at a fixed point as regards the coronal extensions, 
but different parts of the earth come under its influence in succession, 
because of the diurnal motion of rotation. Near the track which this 
temporary pole traverses, during magnetic storms, the needle is much 
more disturbed, and auroras are brighter than elsewhere. Thus, also, 
these phenomena are at their height at the hours of local time, when 
this temporary pole is brought nearest to the point of observation by 
the revolution of the earth on its axis. Once in twenty-four hours this 
temporary pole coincides with the permanent pole, re-enforcing the effect 
of both, and occasioning the absolute maximum of auroras for that day. 
Thus an aurora has been observed to attain its greatest brightness at 
about ten o'clock p. M., local time, in many different localities from 
Russia westward to Alaska, its greatest absolute brightness however 
being at the time of its closest approach to the permanent magnetic pole 
near Hudson’s Bay. During magnetic storms there is at midnight a 
reversal in the direction of the characteristic deflections of the needle, 
evidently due to the changing location of this temporary magnetic pole. 
When magnetic storms persist for several days the curves recorded by 
the declination magnetograph, not infrequently are almost precisely 
similar both as respects direction and extent, at corresponding hours 
each day. So, too, in the case of very severe magnetic storms the 
needles have been observed to have been thrown into a state of agitation 
at practically the same instant throughout the earth, but the direction 
and extent of the movements in different localities are not the same, 
being dependent upon proximity to the temporary pole, in the manner 
above indicated. 
