724 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



prismatic chambers by a medial glass diagonal partition inclined at 45° 

 to the two vertical glass ends. The back surface is silvered for reflection. 

 The deviation (really doubled) is read off on a suitable scale (Fig, 200). 



Fig. 19" 



Fig. 198. 



In Model ii., the metal cylinder K is divided horizontally by a 

 partition in the axis of the cylinder. There are now two glass plane 

 parallel-sided vertical partitions set at 45° to the end vertical glass 



Fig. 199 



III 



Fig. 200. 



Mil 



10 



20 



jll|il!lll|ilji- 

 10 30 



planes, but set so as to produce the deviation in opposite directions 

 (figs. 197 and 198). The horizontal partition is cut away so as to 

 place the two front compartments in communication ; the two rear com- 

 partments are also similarly in communication. The deviation is now 



