328 



The Propagation of Light in Biaccals. 



accuracy of the arithmetic they were calculated independently 

 and the results were compared with those from fig. 4. 



Section by a Plane at 45° to axes of x and y and 

 passing through axis of z. 



Inner. Outer. 



y- 



z* 



y- 



z. 



o-oo 



3-00 



o-oo 



4-00 



1-00 



2-70 



1-00 



3-70 



1-57 



2-00 



1-91 



3-00 



1-90 



1-00 



2-00 



2-91 



2-00 



0-00 



2-79 



2-00 







3-00 



1-63 







3-25 



1-00 







3-39 



o-oo 



Another section of the surface which is of interest is that 



Fie:. 8. 



taken through a singular point and containing the axis of Y. 

 The curves thus obtained are shown in fig. 8. If the axis of 



