MR. R. T. GLAZEBROOK ON PLANE WAVES IN A BIAXAL CRYSTAL. 351 
Section VI.— Application of the Theory to Experiment. — Tables giving Theoretical 
Values of g.—Discussion of Results. 
We can now continue the work of calculating the theoretical values of the reciprocal 
of the velocity. 
Consider first the plane P IP. 
With the same notation we have [Section IV. (3 and 4)]. 
Fig. 10. 
tan \= tan OL cos ALN 
„. cos O'L' . .. 
cos 6 = C0S ( NL ~ X ).( 2 ) 
tan \'= tan 0'L cos ALN 
OC = 0'C = 9° 4' 5" [Section V. (5)] 
LC=1° 21' 42" [Section II. (15)] 
.-. OL=10° 25' 47".(3) 
and 
0'L=7° 42' 23".(4) 
ALN=x=59° 20' 11" [Section II. (17)]. 
Whence 
X=5°21 / 47" .(5) 
log 1-9946(398 .(6) 
cos X ' 7 
\'=3° 56' 52".(7) 
log i 9970915 .(8) 
° cos A, v 7 
