436 Transactions of the South African Philosophical Society. 



If we plot these values as ordinates, with the corresponding values 

 of \ as abscissae, we obtain a curve of the form given below, which 

 may be represented by the formula : — 



X — a + bp + cf 



where p is the radius of the bulb and a, b, c constants to be 

 determined. 



Substituting the values of \ and p, obtained from Table VII., we 

 have— 



•033 = a + b 8-0 + c 64-00 

 •072 = a + b 3-8 + c 14-44 

 •101 = a + b 1-85 + c 3-4225 



the solution of which gives — 



X = -135 - -020? + '00091 P 2 . 



