Chemical Affinity in terms of Electromotive Force. 345 



under these conditions with the following results, clearly show- 

 ing that whilst no very material influence is exerted by dis- 

 continuous stirring with weak currents, the effect is marked 

 with currents of 0*23 to 0'29 C.G.S. unit. 



Cells in 

 battery. 



Average 

 temperature. 



Average 

 current. 



Potential- 

 difference, in 

 volts. 



Resistance 



at average 

 temperature 



of 

 experiment. 



corrected to 

 8°-75. 



3 



6 



9 



12 



7 - 75 

 7-25 

 8-30 

 7-70 



003155 



0-1350 



0-2285 



0-2880 



0-3628 

 1-562 

 2-717 

 3-441 



1-150X10 9 

 1-157 „ 

 1-189 „ 

 1-195 „ 



1-152 xlO 9 

 1-160 „ 

 1-190 „ 

 1-197 „ 



52. In order to see whether any analogous effect would be 

 produced by varnishing the wire, as was done in Joule's ex- 

 periments (owing to possible diminution in rate of passage of 

 heat from wire to water through diminished conducting-power 

 of the varnish), a thin coat of clear filtered shell-lac varnish was 

 lightly applied to the wire ; and after two days drying, some 

 of the observations were repeated, with the result of show- 

 ing that whilst the effect of the varnishing was inappreci- 

 able with a weak current, it became noticeable with currents 

 of 0*14 to 0*24 C.G.S. unit. To make sure that the resist- 

 ance of the wire itself had not been altered permanently by 

 strain &c. during varnishing, the varnish was dissolved off by 

 immersion in alcohol, after which the resistance-value again 

 diminished to its former amount. Thus the following numbers 

 were obtained : — 





Current. 



Cells 

 used. 



Mean 

 temperature. 



Potential- 

 difference. 



Eesistance. 





0-0808 

 0-0772 



0-1426 

 01459 



0-2273 



0-2398 



0-2426 



4 

 4 



6 

 6 



9 

 9 



9 



8-85 

 8-50 



Increase in 



8-79 

 8-20 



Increase in 



8-93 



8-87 



Increase in 



8-75 



0-9347 XlO 8 



0-8931 „ 



resistance . . . 



1-675 „ 

 1-697 „ 



resistance . . . 



2-676 „ 

 2-806 „ 



resistance . . . 



2-835 „ 



1-157X109 

 1-157 „ 



Before „ {supra) 

 After varnishing 



Nil. 



1-174 „ 

 1-163 „ 



Before ,, 



After varnishing 



0-011 „ 



1-178 , 

 1-169 „ 



Before „ 



After varnish again "1 

 dissolved off J " 



0-009 „ 

 1-168 „ 



Phil. Mag. S. 5. Vol. 9. No. 57. May 1880. 



20 



