38 0. 8. Hastings-— Constitution of the Sun. 
above the vaporizing point of all elements contained in it, as it 
rises to higher levels, it cools, partly by radiation, more by 
expansion, until finally the temperature falls to the boiling 
oint of one or more of the substances present. Here such 
substances are precipitated in the form of a cloud of fine 
particles which are carried on suspended in the current. The 
change of state marked by the precipitation is accompanied by 
a sudden increase in radiating power; hence these particles 
rapidly lose a portion of their heat and become relatively dark, 
to remain so until they are returned to lower levels by the 
currents in a reverse direction. 
elements only. I shall attempt to define these elements 
farther on. 
In our theory, then, the granules are those portions of up: 
ward currents where precipitation is most active, while the 
darker portions, between these bodies, are where the cooler 
products of this change with accompanying vapors are sinking 
to lower levels. 
Having stated the theory we will now apply it to the four 
classes of phenomena defined above. 
rom the nature of the condensation, the granules or cloudy 
masses must be very transparent, because the condensation 1s 
confined to elements which have very high boiling points, an 
because such elements can be but a portion, perhaps but 
small portion, of the whole matter contained in the upward 
currents. 
It is not @ priori improbable that we receive light from 
many hundreds of miles below the general outer surface of the 
Thus the fundamental and most important class of phenom- 
ena above classified finds a simple and logical explanation. 
With regard to the phenomena of class II, we have but te 
define the problem in order to find the solution at hand. All 
the lines of class II belong to vapors which lie high in the 
