Dr. W. E. Sumpner on the Di fusion of Light. 95 



Table V. — Keflecting-Power of Tracing-cloth (shiny side) 

 A=1300. K=12. k=2. t? = 35-7. Y calc- =30'9-f 48X/4. 



x 



y 



x .. 



Y obs. 



y 



calc 



50 



55 



623 



59-8 



47-5 



44-5 



90 



1044 



127 7 



1202 



82-5 



75-5 



7-82 



9-10 



11-13 



1045 



7-22 



6-55 



404 



41-8 



441 



43-2 



396 



38-6 



403 



41 8 



442 



43-4 



39-6 



38-7 



Fiar. 4. 



Several sets of tests were taken. Some of these are repre- 

 sented by the sheet of curves shown in fig. 4. Y is the 

 percentage of the incident light which the surface apparently 

 reflects or transmits, assuming that it is all diffused, and is 

 calculated from equation (16). The true values of the co- 

 efficients are obtained from the curves by applying equations 

 (19) and (20). The numerical details of the observations are 

 of no special interest, and the essential results may be sum- 

 marized as follows : — 



