of Refraction of the Metals. 7 



on dispersion are not strictly comparable amongst themselves 

 for all the prisms. 



In most of the experiments, however, the maximum of the 

 red light corresponds nearly to the line C, and that of the 

 blue to the line Gr of the solar spectrum. The measurements 

 of angle and deflection for the separate prisms, given in the 

 following experiments, are in each case the mean of a large 

 number of observations. In each case ten observations were 

 made, and the mean taken as the value of the angle or de- 

 flection. For most of the prisms a number of such determi- 

 nations was made; and the Tables give the final mean of all. 

 The limits of error may be sufficiently seen from the differences 

 which the several prisms show for n ; it does not appear 

 necessary to discuss the errors further. It may be remarked, 

 however, that the main error results from the fact that the 

 surfaces of the prisms were seldom perfectly plane. I have 

 myself made all the adjustments; the readings of the micro- 

 scope were made and noted by an assistant without reading- 

 out the several deflections. 



I must not omit to express my thanks to the gentlemen 

 who have assisted me in this work, Dr. L. Arons, Dr. C. 

 Schmidt, and Dr. 0. Wiener, the last of whom also assisted 

 me in the manufacture of the prisms, and undertook certain 

 measurements of angles made by way of control. 



Silver. 



No. 



5. 



a. 



n. 



Remarks. 



Red. 



White. 



Blue. 



Red. 



White. 



Blue. 



1 

 2 

 3 

 4 



5 

 6 



7 

 8 



5-58 

 DCS 

 11-59 

 12-68 

 14-38 

 11-32 

 1544 

 21-40 





- 4-37 



- 7-71 



- 8-29 



- 8-10 

 -10-18 



- 8-41 

 -10-53 

 -10-77 



... 



••• 



0-22 

 0-20 

 028 

 0-36 

 029 

 0-26 

 032 

 0-22 





1 



| Electroly tically deposited 



\ fi om a bath of silver 



potassium cyanide. 



i 



\ Chemically reduced. 











Mean . . . 





0-27 





The dispersion in silver is 

 so small that it could not 

 be measured. 









Gold. 





1 

 2 



9-05 

 13-87 



- 5-60 



- 0-33 



... |- 1-34 

 - 5-82 4- 1-96 



0-42 1 ... 

 0-33 0-58 



086 

 114 



Electrolytically deposited. 









Mean . . . 



0-38 





100 





