( 188 ) 



the scale of the galvanometer at two values of R'\o (see tables I 



and IV). 



, c. In order to find Ec, Re and E'c, which with regard to Re have 



|a similar meaning as R\o and E\o with regard to Rw , are treated 



ilike R'w and R\ concerning the corrections a, /?, y and d. The 



I thence derived result R"'c holds for the temperature at which the 



j water boils in the boiling apparatus at the barometric height B 



I existing there during the observation. 



I' 8. R"'c is corrected to the value which it would have at a pres- 



Isure of 760 m.m. mercury at the sealevel in a northern latitude of 45°. 



• d. To find R' the corrections mentioned sub y and ö are applied 



; to the invariable resistance R'. 



I' e. E', referring to the temperature i of the Weston-battery, is 



derived from Jaeger's table ^). 



§ 7. Survey of a measurement. Table I contains all the readings 

 : which serve for a measurement of the electromotive force namely 

 ! foi' that at — 217° (comp. ^ 8). We suppose that during the short 

 time required for the different readings (comp. § 3 of comm. N°. 89) 

 the electromotive force of the accumulator (comp. § 4, c) remains 

 constant. We further convince ourselves that the temperature in the 

 boiling apparatus of the comparison-element has remained sufficiently 

 constant and that we have succeeded *) in keeping the temperature 

 of the bath in the cryostat constant to within 0°.01 ^) (see table I). 



In exactly the same way we have obtained on the same day of 

 observation the values for the electromotive forces which are combined 

 in table III. 



From the preceding survey it appears that the measurements can 

 be made with the desired precision even at — 217°. At — 253° the 

 sensitiveness of the element constantin-steel is considerably less 

 than at — 217°. It seems to us of interest to give also for this very 

 low temperature a complete survey of the readings and adjustments 

 so that the reader may judge of what has been attained there 

 (see Table IV). 



1) Jaeger, Die Normalelemente 1902. p. 118. 



'i) Comp. Comm. N". 83, § 5 and PI. III. 



3) Together with the readings we have also recorded the temperature of the 

 room [tk) and of the galvanometer {Uj) ; these are of interest in case one should 

 later, in connection with the sensitiveness, desire to know the resistance of the 

 galvanometer and the conducting wires during the observation. For the notation of 

 the combination P3 + Qo of die comparison-elements we refer to Comm. N'. 89 § 2. 



