368 MESSRS. R. T. GLAZEBROOK AND T. C. FITZPATRICK 



Tables VJI. and VIII., which contain the results of the observations, do not require 

 much explanation. The one unit tubes are given in Table VII. In tube VI. filling 

 2, the curvature of the ends of the mercury column was much less than in any other 

 case, and the correction 81/1 has, therefore, been calculated specially for this tube 

 The result is clearly too high, but there is no reason in the details of the measure- 

 ments for omitting it. It may be noticed that the results of the 4th and 7th fillings 

 are not given in the Table. These will be referred to again shortly ; they were fillings 

 of a special character, and it seemed best to treat them separately. 



The extreme difference between any two fillings is '000135, and the difference 

 between the mean result and the extreme is about half of this. In some of the 

 columns the figures have been given to six places ; the only object in this is to secure 

 accuracy in the fifth figure in the final result. 



In the Table for tube VIII., the fourth and sixth fillings are omitted for a similar 

 reason to that given above. The extreme difference between any two fillings is about 

 the same as in the case of VI. The mercury used in VIII. 5 was taken directly 

 from the iron bottle in which it was supplied by Messrs. TUBES and WILKINS, and 

 was not distilled in the Laboratory. In the first filling of VIII., and the first and 

 third fillings of VI., the filling from which the cross section is determined was different 

 from that used to determine the resistance. This was due to the fact that at first 

 the necessity of having the tube almost completely full when finding I was not fully 

 appreciated, and too much mercury was allowed to escape from the ends in removing 

 the terminals. In the other cases in this table the two fillings were the same. The 

 mean value for tube II. is reduced by the result of the 2nd filling, which is clearly too 

 low, but the observations themselves do not give us any reason for rejecting it. All 

 the fillings for this tube have been included. 



The mean value of r found from these three tubes is '95354 B.A. unit, and the 

 greatest difference between any two observations is '000241 B.A. unit. The average 

 error independent of sign is '00005. 



If, however, we rejected the results of VI. 2 and II. 2, the mean would hardly be 

 affected, but the mean error would be reduced to '000037. 



We may, therefore, fairly put as the result of the observations on the one unit 

 tubes r = '95354 '00004. This is, it will be observed, the value given by 

 tube VIII. The value for VI. is raised unduly by the observation VI. 2 ; that for 

 II. is unduly lowered by the result of II. 2. 



