350 



PROCEEDINGS OP THE AMERICAN ACADEMY. 



These data are plotted in Figure 16. 



1 2 

 Time from birth of crystal 



Figure 16. Diagram Representing Rate of Increase in Crystal 



Diameter. 



n represents point from averanre of crystals taken at random. 

 O re])resents point from avera;j,e of solccteil crystals. 



represents prohnhle actual rate of growth. 



represents equation />* = kt. 



represents equation D- = kt. 



The unit of time is tlie time of one revolution of the shutter, or 1.25 seconds. 

 The substance was potassic iodide. 



The inspection of the fifjure show.s at once that the curve is similar in 

 general .shape to one represented l)v iIr; ('(|iiati<)n D" = /•/, wliere /) is 



