1883.] Some Experiments on Metallic Reflection. 31 



of light varies inversely as the square of the distance from the source, 

 the percentage reflected by the plate is obtained by dividing the 

 numbers contained in the second column by those in the fourth, 

 squaring, and multiplying by 100. 



Two other series of observations were made with the silver plate, 

 the measurements being about as concordant as those given above. 

 Table I contains the results of these three series and their mean. 



Table I. 



Angle of 

 Incidence. 



Percentage amount of Light Reflected by the Silver Mirror. 



o 



A. 



B. 



C. 



| Mean. 



10 



72 -60 



64-79 



70-20 



'70-05 



20 



73 -38 



65-77 



71 02 



70 -06 



30 



74-67 



65 -80 



73-57 



71-35 



40 



74 15 



66-25 



72 -20 



70 -87 



50 



74-46 



69 -37 



73 65 



72 -49 



60 



75-94 



71 -46 



75 -18 



74-19 



65 



76 11 



70 -45 



74 17 



73 -58 



70 



77 -49 



72-30 



74 -09 



74-63 



75 



80 -0 



f 76-50 I 

 I 75-92 j 



76-58 



77 25 



77 



79-60 







79-60 



80 





/ 80 -95 1 

 \ 81-60 J 



81 -03 



81-19 



Note. — The mirror was slightly tarnished when the B series of 

 measurements were made. 



Similar measurements were made with steel, tin, and speculum 

 metal plates. The results are given in Tables II, III, and IV. 



Table II. 



Angle of 

 Incidence. 



Percentage amount of Light reflected by Steel Mirror. 



o 



A. 



B. 



C. 



Mean. 



10 



53 -53 



54-66 



54-97 



54 -38 



20 



55 -18 



54-42 



56-58 



55 -39 



30 



55-38 



53-77 



55 -64 



54 93 



40 



56 -04 



54-80 



56 -01 



55-62 



50 



56-10 



56-58 



57 -54 



56-74 



60 



58-50 



56-72 



57 -48 



57-63 



65 



59-23 



57-39 



58-50 



58-37 



70 



57 -22 



57'59 



59 -45 



58 -09 



75 



59-16 



56 -22 



60 -69 



58-69 



80 



65-23 



61 -23 



64-22 



63-56 



