508 



Dr. E. J. Mills on Electrostriction. [Dec. 13, 



Zinc. — Two pint Daniell's cells were employed, and thermometer 454. 

 The results were as follows : — 









Hours. 



local descent. 



Temp 



0-5 



0-352 



o 



12-4 



1-0 



0-308 



12-5 



1-5 



0-366 



12-7 



2-5 



0-404 



13-2 



3-5 



0-382 



13-8 



4-5 



0-574 



14-5 



47-0 



0-749 



11-6 



It is probable, from the graphic projection of these numbers, that the 

 descent attained after the forty-seventh hour would have been little, if 

 at all, exceeded by prolonging the experiment. 



Cadmium. — The conditions were those of the preceding set of obser- 

 vations. 



Table VII. 



Hours. Total descent. Temp. 



1- 0-185 15-0 



2- 0-274 15-5 



3- 0-164 15-8 

 5-0 0-166 16-8 



23-5 0-207 15-3 



At the end of the experiment the deposit was found to be somewhat cor- 

 rugated, but fairly satisfactory. The electrolyte had the disadvantage of 

 being freshly prepared, and not having been continuously worked prior 

 to this deposition. 



Value of the Electrostrictive Effect. 



In order to ascertain the value of the electrostrictive effect, thermo- 

 meter 454 was adjusted in a water-pressure apparatus capable of indi- 

 cating about 2| atmospheres : it was then submitted to uniform com- 

 pression, and the resulting ascent of the mercury in its stem noted. 

 Two sets of observations at higher pressures showed, after the usual 

 reductions, that a unit of scale corresponded to 8-2 and 8-5 atmospheres 

 respectively ; the mean is 8*3 atmospheres. After this the bulb of the 

 instrument was unfortunately broken, w T hile preparing it for considerably 

 increased compression. I have, however, little hesitation in accepting 

 this result as a datum for calculating the total electrostrictive effect at 

 much higher readings. Similarly with thermometer 502, a depression of 

 0°*199 C. was caused by opening ; this would correspond to 5-03 atmo- 

 spheres per scale-unit. Again, ten experiments with thermometer 455 

 were conducted in an Andrews's duplex apparatus (a most admirable 



