3()9 



Th the fiisf place it was investigated, whether there was a systematic 

 ditference in tlie results of a series of observations according to 

 whether tlie microscope was pointed 3 times on tiie metre and 

 4 times on the measniing-bai-, or 4 times on the metre and 3 times 

 on the measuring-bar. For tliis pui-pose the mean was tirst formed 

 of corresponding series in the positions .1 and />, in which the 

 number of times that the microscope was pointed on the metre and 

 therefore also on the measuring bar, was the same. A-Ccording to 

 these averages the mean error of observation in micromms was: 



WiLDEBOKR DiEPERiNK Bakhuyzen Mean 



0.371 0.366 0.509 0.420 (I) 



After this the average was foi-iued of corresponding series in 

 A and B in which the number of times pointed on tiie metre and 

 on the measuring bar was unequal ; according to these averages the 

 mean error of observation for a series was : 



Wildeboer Dieperink Bakhuyzen Mean 



0.496 0.330 0.440 0.428 (II) 



From the agreement of the two means we may infer that tiiere 

 is no systematic ditference in the series witli 3 or with 4 poinlings 

 on the metre or measuring bar. 



It was next investigated, if there was a systematic difference in 

 the results of series in wliicli the metre was in a different position 

 relatively to the observer, i.e. in the results of the series / and /•. 



This was done in two way«. 



'i. The differences were found of the corresponding series in 

 which the observer and the metre were in the same position in 

 which differences the systematic error referred to plays no j)art. The 

 mean error for a series ni deduced from this is: 



Wildeboer Dieperink Bakhuyzen Mean 



0.450 0.346 0.492 0.434. (Ill) 



After this the mean was formed of all the corresponding values 

 found with the same position of the observer, in position / as well 

 as position r of the metre. 



The dexiations of all these values from their mean, in which the 

 influence of the systematic error is present give the following values 

 for the mean error of a series. 



Wildeboer Dieperink Bakhuyzen Mean 



0.454 0.594 0.630 0.564 (IV) 



2. The means were found of an observation-series in position 



A and in a corresponding series in position B, in which the metre 



21 

 Proceedings Royal Acad Amstenlam. Vol >'VU 



