264 Mr. C. Spurge. On the Effect of Polish on the 



Table XIV — continued. 



No. 3. 



No. 4. 



Means 



of ten 

 readings Means 



of 1st of 50. 



vernier. 

 355° 49-5' 

 355 56'8 

 355 46 -0 

 355 51-7 

 355 51-5 



355 

 355 53-8 

 355 51-7 

 355 49-7 

 355 50-6 

 355 46-6 



Means 

 of ten 

 readings 

 of 2nd 

 vernier. 

 175° 58 '( 



51 



355 50-5 



No. 5. 



355 50-8 

 355 54 9 



355 51-8 



356 2-4 

 355 54-5 



176 5 



175 54 



176 

 176 

 1 



176 3 

 176 

 175 58 

 175 59 



175 55 



176 

 176 4 

 176 

 176 10 

 176 4 



355 54-9 



Means 

 of 50. 



176 4-06 

 Mean of 500 



Means 

 of 100. 



176° -0' 265° 55 -5 



175 59-5 265 55 '0 



265 59-5 

 265 57-28 



The results in Table XIV show a greatest error of 232' from the 

 mean for a 100 readings, and of about 47 for 10. Before polishing 

 the value of I as given by Table X is — 



I' = 266° 5-3'. 



After polishing, Table XIV gives — 



I' = 265° 57-28'. 



There is thus a difference of 8'. This is covered by the larger 

 limit above, but not by the lower. This is not surprising when the 

 errors and fluctuations of single observations are taken into account, 

 and also the number of observations. I 



The parallelism of the polished and repolished faces was tested by 

 means of the lines drawn round the sides. As these lines gave no 

 perceptible inclination, it did not seem worth while to measure the 

 angles with a spectrometer, since the differences caused by repolishing 

 are so small. 



Thus, we come to the conclusion that the repolishing produced 

 little, if any, alteration in the nature of the reflected light, and that 

 this alteration is very small compared with the change produced by 



