Prof. L. T. More on Electrostriction, 9 



the armatures, and a more sensitive apparatus than Ercolini^s, 

 confirm mv former ones. 



As my previous experiments did not convince my critics, 

 there was no alternative but to repeat them, and as conclu- 

 sively as possible. In doing so the following points were kept 

 in view : the apparatus should be more sensitive and more 

 carefully adjusted ; extraneous effects guarded against or 

 eliminated ; effect of heating measured ; and the mechanical 

 attraction of the armatures, when adherent, calculated. The 

 task has been an extremely difficult one ; but perhaps in all 

 four particulars something has been done. 



In a general way, the apparatus is similar to the one pre- 

 viously employed ; but it was certainly more efficient because 

 of better construction. Whether the interferometer method 

 is better or not, I do not know ; but the errors do not result 

 from any lack of sensitiveness or accuracy of the magnifying 

 machine used. 



A brass tube A (PL I. fig. 1) was screwed in a heavy iron 

 flanged collar,aud thistoawooden base. The experimental glass 

 tubes were placed coaxially over this brass tube and cemented 

 to a brass collar C at the base. The brass tube thus formed 

 one armature and the glass tube the dielectric of a condenser. 

 For the other armature several defaces served, either a sheet 

 of tinfoil was pasted on the outer surface of the experimental 

 tube ; or a glass tube, silvered on its inner surface, cemented 

 in a position coaxially to the other two ; or a brass tube F 

 capped with short glass tubes at the top and bottom, as shown 

 in the figure. The brass tubes were seamless, quite straight, 

 and of uniform thickness. The glass tubes were obtained 

 from Messrs. Eimer and Amend, of JS'ew York, who kindly 

 examined their entire stock in order that they might supply 

 me with j^erfect pieces. 



The dimensions of the tubes are oiven in the table. 



Table 11. — Experimental Glass Tubes. 



No. • 1 Length. 



Outer 

 Diam. 



l^Z Thickness.! 



1 j 



1 65 cms. 



2 65 „ 



3 65 „ 



4 ' 65 „ 



5 65 ,. 



6 65 „ 



4-40 cms. 

 4-48 „ 

 4-43 „ 

 4-55 „ 

 4-53 „ 

 4-67 „ 



4*05 cms.i 1-8 mm. 

 4-05 „ i 2-2 „ 

 4-03 „ i 20 „ 

 413 „ 1 2-1 „ 

 4-15 „ I 1-9 „ 

 4-23 „ 2-2 „ 



Inner brass tube A, Length 64 cms., outer diam. 3-9 cms. 



Outer glass „ F, „ 62 „ inner „ 4-9 „ base to silver G cms. 



Outer brass „ F, „ 55 „ „ „ 4*7 „ ,, tube 5 cms. 



