THE ACTION OF TWO SUPERPOSED CRYSTALLOID BODIES. 347 



To facilitate the comparison of the colours, which is here the 

 question at issue, the following synopsis may be of service ; it 

 consists of observations with different pairs of plates, which inter- 

 sected at angles of 22J, 45, and 67|. In the first combination 

 series the acceleration colours move in the second order i.e., they 

 are colours which for e = follow the second order of Newton's 

 Table. The second combination series refers, on the other hand, to 

 acceleration colours which belong to the third order. The selenite 

 plate, upon which rotation was made, was red I. The colour 

 of the consecutive position is denoted by C, that of the 

 alternative by A. 



FIRST COMBINATION SERIES. 



SECOND COMBINATION SERIES. 



