Assumption of a Solar Electric Potential. 165 
the sun wherever they are not, as in the vicinity of the 
equatorial plane, withdrawn from that attraction by planetary 
revolution. Hence a constant inflow of dissociated matter to 
the sun must take place, especially in the polar regions, where 
there is a total absence of centrifugal force, as my brother 
supposes. If the mass of the sun, as may well be assumed, 
remains invariably the same, this means that a state of equili- 
brium has entered, in which just as much burnt matter flows 
out from the sun's equatorial zone as is again conveyed by 
attraction, in a state of dissociation, to its polar regions. 
Then the flow from the pole to the equator, as well as the 
proved lower angular velocity of rotation of the gaseous mass 
of the sun in its higher latitudes, would consequently follow. 
Although, however, this gives the possibility of the pro- 
duction of a solar electric potential by friction and continual 
removal from the sun of the parts charged with one of the 
electricities, yet the mechanism of this electrification still re- 
mains very obscure. The light of the sun proceeds from a sea 
of flame which, according to Bitter's beautiful calculations, 
must have a thickness of about 25 kilometres. Whether a 
flame of burning gases of this thickness will still transmit much 
of the heat- and light-rays from a hotter source of emission, 
how much of them it will absorb or, like a layer of cloud, will 
reflect, we cannot know. I have recently* shown that gases 
heated to from 1500° to 2000° C. still appear perfectly dark, 
while even at a lower temperature they emit the more slowly 
vibrating heat-rays. Whether gases become self-luminous on 
being raised to a much higher temperature has not yet been 
determined by experiment. As, however, a small flame in a 
brighter light casts a shadow, it seems unlikely that many of 
the light- and heat-rays from the deeper and hotter strata of 
the sun can traverse the huge photosphere. The observed 
temperature and light of the sun are then phenomena origi- 
nating essentially in the chemical action that goes on in the 
solar atmosphere. This requires that that atmosphere ascend- 
ing in a state of dissociation and at the same time cooled by 
increase of volume, shall begin to burn when the limit of the 
temperature of dissociation for the respective compound is 
passed, and that this combustion shall continue until the loss 
of heat by expansion is equal to the heat liberated by combus- 
tion. The apparent temperature of the sun will hence be 
approximately the dissociation-temperature of those compounds 
which have the highest chemical heat-equivalent, consequently 
of water, the elements of which will burn at the greatest alti- 
tude, while the masses which are heavier and at the same time 
* Sitzungsb. der Akad. der Wiss., Wied. Ann. xviii. pp. 311-316, 1883. 
