306 



6. Reduction of the ohsei'vations and results obtained. The micro- 

 meter readings are all reduced with the above mentioned values 

 for the run of the screws in micromms and for the periodic errors 

 in micrometer 1. 



The errors of thermometer 4570 belonging to the Dutch platinum- 

 iridium metres, which was used for the temperature-determinations 

 of metre No. 27, were determined by comparison with two thermo- 

 meters standardized at Breteuil, and by separate determinations of 

 the freezing point. It appeared, that between 0° and 30° the ther- 

 mometer is free from errors, except the error of the freezing point, 

 which was — 0.48°. The determinations were made by Mr. H. C 

 Volkers, lecturer at the Technical University at Delft. 



For the thermometers 15355 and 15356 belonging to the invar- 

 bar both the errors of division and tlie correction for the zero ai-e 

 negligible. 



In the reduction of the length of the metre and the measuring- 

 bar the following coefticients of expansion were used. For the metre 

 the value communicated by Bosscha in his paper: "Relation des 

 experiences cpii ont servi a la construction de deux metres étalons en 

 plcXtine iridié, compares direetement avec le metre des archives" and 

 which from if to t^ gives an expansion for the metre in micromms 

 of: 



8.4327 ^ + 0.00401 ^^ 



For the measuring bar, the determination made at Breteuil was 

 used, which gives for the expansion per metre in micromms; 



1,6245/ -I- 0.001065^*. 



After the introduction of these reductions, the three observers 

 obtained the following results for the lengths of the 4 portions of 

 the measuring-bar, each about a metre in length, diminished by the 

 length of N". 27 both at the temperature of zero. These results 

 are the mean of the observations of one series. 



Portion 0—1. 



WiLUEBOER DlEPERINK BaKHUYZEN 



Position A Position B Position A Position B Position A Position B 



l^ —29.70 —27.43 —28.65 —27.39 —27.93 -26.40 



/, 28.25 27.84 28.28 27.19 28.60 27.13 



r, 29.25 28.39 28.85 27.94 29.89 27.96 



r, 29.01 28.95 28.89 28.23 29.49 27.91 



