M. G. Wertheim on the d^ubk IRefraction 



the fifth and sixth cohimns. These thicknesses arc calculated 

 in millionths of the English inch, so that they may be immedi- 

 ately compared with the measures of Newton. 



Finally, we shall see that the designations of the colours, 

 which I have sought to render as faithful as possible, agree most 

 usually with those recently published by M. Briicke*. 



* PoggendorflTs Annalen, vol. Ixxiv, pp. 461, 582, 



