M.-P.-VoL. I.] CRAWFORD-CONSTANT OF REFRACTION. 195 

 Weighted Observation Equations. 



; . ; - ' . , ' 'V i - ' 



To render these more nearly homogeneous, let D=D; 

 loox y and multiply the absolute term by 100. Then we 

 have the following 



Weighted Homogeneous Observation Equations. 



Combining these by the method of Least Squares we 

 obtain the following 



Normal Equations. 

 + 341.28 D 254.512 y= 61.7188 

 254-5 1 -fipV-JS 1 -f53-4383 



Solving these, remembering that the absolute terms had 

 been multiplied by 100, we have 



log 7.75694; log y=8. 00376 or log x=6. 00376. 



Now since D=Zx, we have log Z = 1.75318, 

 Whence x= -{-0.0001009 and Z=56 



Substituting the values of D and x, thus found, in the 

 Weighted Observation Equations, we find \_pw~\ = 



