184 
IOWA ACADEMY OP SCIENCE 
that perhaps in the making of any variety of selenium that something in the 
selenium itself causes it to maintain given rates of change. On this view 
definite rates of change establish definite configurations, and the one must go 
with the other in any equilibrium state. If filing destroys a fixed configura- 
tion it must also alter the rates of change. The fact that different varieties of 
selenium can have different rates of change under the same temperature, pres- 
sure, humidity and electrical conditions, merely proves that there is another 
condition which varies in different samples of selenium, and further indicates 
that that this varying condition may lie in the selenium itself. If so the condi- 
tion would be a matter of history. It is really not strange that the previous 
treatment of the selenium should determine its fixed rates of change and prop- 
erties also. Rupture by abrasion perhaps undoes a certain amount of history, 
and further perhaps may make possible a growth or change under altered con- 
ditions. In any event it is necessary to regard light-sensitive selenium as made 
up of changing and moving parts, which reach equilibrium but never come 
to rest. 
SUMMARY. 
1. The effect of rupture by abrasion has been studied on both light-positive 
and light-negative selenium. 
2. The specified types of rupture produce a temporary increase in the con- 
ductivity of the selenium of the Giltay cell. 
3. Rupture of the same nature produces a change of conductivity in light- 
negative selenium of opposite sign to that in light-positive selenium. 
4. Both varieties of selenium recover from the effect, but more slowly than 
they recover from any other known agencies, that alter the conductivity. 
5. The changes in conductivity following rupture are favorable to certain 
views of the kinetic theory of matter. 
