44 Profs. Ayrton and Perry on Ice as an Electrolyte. 



occur at the melting-point. A series of further experiments 

 made with the same apparatus, since the writing of the previous 

 aper, have enabled us to draw approximate curves (PI. II.), 



A B C, D £ for the specific capacity of j w ^ r 1 from- 12°*2 



C. to + 5° C, all tests of capacity being made by charging 



I ice ") 



for ten seconds and then short-circuiting the-j wa + er r con ~ 



denser for fifteen seconds. From these it will be seen that, 

 although the change at the melting-point is not quite as sudden 

 as we expected, our anticipations are on the whole realized. 

 It must be remembered too (see the description of the appa- 

 ratus in our former paper) that, as the present experiments 

 were made with a gradually rising temperature, the thermo- 

 meter will always indicate a temperature a little higher than 

 that of the ice ; the curve B C ought probably, therefore, to 

 be even more vertical than it is. 



Distances measured perpendicularly to Y Y represent 

 temperature — positive temperature if measured to the right, and 

 negative if measured to the left. Distances measured perpen- 

 dicularly to X X represent specific capacity per cubic centi- 

 metre for points on the dotted lines, and conductivity for points 

 on the continuous lines. The scale for temperature is the same 

 for all the curves. The scale for vertical distances for the 

 capacity-curve D E is one eighth of that for the capacity- 

 curve ABC; and the scale for vertical distances for the con- 

 ductivity-curve J K is three thousandths of that for the curve 

 FGH. 



The point A corresponds with a capacity per cubic cen- 

 timetre of about 0*002 microfarad, at —12° C. ; E corre- 

 sponds with a capacity per cubic centimetre of about 0*1185 

 microfarad, at + 5° C. ; at this apparent temperature the capa- 

 city was increasing so rapidly as to make exact measurements 

 very difficult, although the temperature was increasing but 

 slowly. The point F corresponds with a specific resistance 

 per cubic centimetre of about 2240 megohms, at — 12°*4 C. ; 

 and K with a resistance per cubic centimetre of about 0*34 

 megohm, at +11°*02 C. As in our previous experiments, the 

 water employed in the water-condenser was distilled, and the 

 ice was formed by freezing it with an external freezing-mixture 

 no particle of which was allowed to fall into the distilled 

 water. 



The important theory which Prof. Clerk Maxwell has deve- 

 loped, by comparing the propagation of electro-magnetic dis- 

 turbances through the ether with the propagation of light-vi- 

 brations, has been illustrated only by paraffin (a non-conductor); 



