14 Prof, L. T. More on Electrostriction. 



Table VII. — Tube 2. Length of Armature, 52 cms. 



Spark- 

 length. 



Initial 

 Reading. 



Final 

 Reading. 



Deflexion. 



Remarks. 



j 



10 mm. ... 



88 

 63 

 18 



75 



38 



3 



13 



25(?) 



15 



1 jar in circuit. 



15 mm. ... 



218 



30 



243 



214 



160 

 243 



214 



185 



58 

 37 

 29 

 29 



For the remainder of experi- 

 ment no time elapsed between 

 successive charges. 



20 mm. ... 



148 



10 



230 



100 

 230 

 199 



48 

 30 

 31 



Zero changed. 



15 mm. ... 



185 

 168 

 143 



168 

 158 

 133 



17 

 10 

 10 





10 mm. ... 



102 

 90 



97 



84 



5 

 6 





The first series o£ observations, Table V., shows the influence 

 of the duration of the charge, of discharge, and of the 

 repetition of the charge when the potential-diiference is 

 maintained the same. When a quick charge is first given to 

 the tube, it apparently increases in length about 1 5 divisions for 

 a potential-difference of 12 mm. spark, or 110 C.G.s. If the 

 tube is charged more slowly, about a minute, the increase in 

 length is more than double, and, on the other, hand, a less 

 duration of charge diminishes the effect to a very small dis- 

 placement. Table VI. shows the first effect of a charge at a 

 greater potential to be the same as for a less. 



In Table VII. the effect of varying the potential is given. 

 With an increase of potential the elongation increases, but 

 not uniformly, and a return to the lower potentials shows a 

 much diminished value. 



Before a true interpretation of this elongation normal to 

 the field can be made, at least two corrections must be 

 allowed for. In the first place, since the armatures are in 

 contact with the glass, their mechanical attraction will com- 

 press the glass in the direction of the field, and this compression 

 will be attended by an expansion in the direction of the axis 

 of the cylinder, according to Poisson's theory. Finally, 

 charo;ino^ the armatures will certainlv heat the tube to some 

 extent. 



The formula for the first correction in my former paper 



