189r.] VEEDER—ON THE ZODIACAL LIGHT. 145 
It will be observed that no account has been made of any presumed 
variability of solar heat. The forces concerned in the various forms of 
periodicity described, whatever else they may be, do not appear to be 
thermo-electric. It is inconceivable that puffs of heat should be 
conveyed from disturbances at the eastern limb, or any other point on 
the sun exclusively, so as to originate a periodicity, such as that manifest 
in the case of auroras. The electrical impulses are conveyed, not as 
heat radiations, but in accordance with ordinary principles of magnetic 
induction, bearing no other than merely incidental relations to heating 
effects. Noris there any conclusive evidence that these impulses are 
conveyed as light radiations. Indeed, some of the chief effects which 
they produce are confined to the darkened side of the earth. In short 
the preponderance of evidence is to the effect that they constitute a 
special form of solar activity, having well defined peculiarities and 
standing apart from the rest. 
It will be observed also that no reference has been made thus far 
to the idea that tidal strain due to planetary positions may originate 
the conditions in the sun upon which magnetic phenomena depend. 
The writer has been unable to reconcile the eleven year period and 
other peculiarities with any schedule of planetary positions thus far 
devised. On the other hand the somewhat irregular character of the 
periodicity, and the ways in which it tends to manifest itself all indicate 
that the originating forces in the sun are chiefly, if not entirely, volcanic. 
At times of apparent solar quiet, there is an accumulation of energy 
which bursts forth when a certain limit has been reached, causing the 
characteristic rapid increase of sunspots, auroras and magnetic storms at 
the beginning of each fresh cycle of solar activity, which in turn is fol- 
lowed by the usual comparatively slow decline. In aviscous mass, such 
as that of which the sun probably very largely consists, eruptions will be 
most likely to recur with considerable regularity, as they do in the case 
of the terrestrial volcano Kilauea, whose lavas are characterized by 
unusual viscidity. Thus the eleven year period may be simply of solar 
volcanic origin. 
As bearing upon the manner in which the explosive forces mani- 
fest at certain points on the sun, originate and propagate electrical 
impulses, the various facts in regard to the zodiacal light acquire 
very special interest. The purpose of the present discussion has not 
been so much to elaborate a working hypothesis, although perhaps this 
is really involved, as to present a compendious account of phenomena 
actually observed in their natural relation to each other. It is a con- 
tinuation of the research some of the results of which were presented 
