( 334 ) 



Especially in a coramiitator for the galvanometer-current these difficulties 

 arose. Contacts made by solid homogeneous copper have given the 

 greatest satisfaction. With this arrangement for measuring the 

 temperature the current through the L^-tube, the chief current, had 

 to be cut off for a moment during the reading of the galvanometer. 

 Therefore the gahanometer commutator was combined with an inter- 

 rupter for the chief current. 



Changes in the meridian during the experiments w^ere eliminated 

 by noting, before the deflection., the position of the galvanometer- 

 mirror when at rest. This position w^as more or less affected by the 

 magnetic field of the chief current, but this obstacle was overcome 

 by systematically combining readings with reversed chief current 

 and galvanometer-current. 



The galvanometer, made by Carpentier, was of the TnoMsoN-type. 

 Provided with a sensitive set of magnets after Paschen, suspended 

 by a quartz-fibre of ± 7 n, with electromagnetical damping and 

 with coils of small resistance (2,76 i2), this instrument answered to 

 all the special requirements of the problem. 



The strength of the current was determined by measuring the drop 

 of the potential at the ends of a known resistance, and comparing this 

 with that at the poles of a WESTOX-element. The potential differen- 

 ces w^ere measured with a five-cell quadrant-electrometer (H. Haga, 

 These Proc. I p. 56). 



The course of the experiments was the following : 



A sufficiently long time beforehand the fluid in the boiling-reci- 

 pient was set boiling and the tapwater was allowed to run. Then the 

 current in the L"-tube was closed. When the distribution of the tem- 

 perature had grown constant, the positions of the gahanometer resp. 

 when at rest and deflected were read. After five minutes these readings 

 were repeated, but now the commutator for the galvanometer was closed 

 in the opposite direction. Then the current in the t^-tube was 

 reversed and after 10 or 15 minutes the galvanometer-readings were 

 resumed. In a corresponding way the measuring of the Joule-heat 

 was carried out. 



Tn each series 8 deflections were read, as well for the determina- 

 tion of A Thi' as of L jU ; first four of one quantity, then eight of 



the other, and again four of the first. In the meanwhile during the time 

 necessary for the temperature to become constant, the current strength 

 was measured from time to time, and the temperature of the run- 

 ning ^vater was read. In this way the following results have been 

 obtained ; 



