the Thermal Conductivity of Water. 

 Table II. 



63 



irregularities in the windings of the heating-coils. Table II. 

 also shows an increase in the conductivity with rise of tem- 

 perature, which is roughly about 1 per ceut. per degree ; 

 but the actual variation of temperature from which it is 

 obtained is so small that not very much weight can be laid on 

 its value*. 



The final mean value of k for water obtained from these 

 experiments is 



0-001433 c.g.s. at 20° C. 



Below are given the results of some previous observers for 

 comparison : — 



Lundquist . 

 Winkelmann . 

 Weber f . . 



Lees | . . . 



* The results which have been obtained by different observers for the 

 temperature-coefficient are very different. Weber (Wied. Ann. x.) 

 obtains an increase with rise of temperature of 08 per cent., whde Lees 

 (Pnil. Trans. 1893, p. 425) finds a decrease of 0'5 per cent, per degree. 

 The value given above is roughly confirmed by some direct differential 

 measurements of the tempera ture-co fficieut made by taking readings, at 

 constant current and with very different water thicknesses in the two 

 vessels, of the alteration of the bridge- wire contact produced by varying 

 the temperature of both sinks of heat. These, however, were not very 

 reliable in consequence of the fluctuations already mentioned caused by 

 artificial heating of the water, we hupe to repeat them, with improved 

 arrangements for keeping the temperature constant. 



f Loc. cit. 1 Loc. eit. 



k. 

 0-0015G 



Temperature 

 40-8 



154 



14 



124 



4-1 



143 



23-6 



136 



25 



120 



47 



