206 



Dm W. De La Rue and H. Miiller. [Jan. 10, 



V. " Experimental Researches on the Electric Discharge with 

 the Chloride of Silver Battery." By WARREN De La Rue, 

 M.A., D.C.L., Ph.D., F.R.S., and Hugo Muller, Ph.D., 

 F.R.S. Received December 21, 1883. 



Elasticity and Viscosity of Strata. 



During our experiments we have often been struck by the evident 

 plasticity of strata whose form at times becomes modified when they 

 meet with an obstacle or are influenced by other causes, as, for 

 example, the crossing of other strata produced by a separate dis- 

 charge ;* and we have stated in Part IV of our researches that " one 

 cannot but be impressed from this (an experiment therein spoken of) 

 and others before,f and herein described, by the apparent plasticity of 

 the aggregate assemblage of molecules which constitute a stratum." 

 In all probability the molecules are being continuously thrown off 

 and are replaced by others which become controlled and held in 

 position by the same balance of forces as those they replace. 



One of our tubes, No. 9, with a residual hydrogen vacuum, has a 

 diaphragm in the centre \ of an inch, 0"63 centim., thick, through 

 the centre of which there is a hole j of an inch., 0"63 centim., in 

 diameter. To the end of the tube is attached a potash absorption 

 chamber, the heating and cooling of which causes a change in the 

 number of strata ; when the number of strata increases they approach 

 closer and closer to the diaphragm, and occasionally one threads itself 

 through it, as if squeezed through, and its form is gradually changed 

 thereby; when by a change in the temperature of the absorption 

 chamber, the number of strata becomes less, the stratum which had 

 been forced through the hole in the diaphragm returns through it, its 

 form becoming modified to enable it to do so. 



A tube, No. 368, fig. 1, with a hydrogen residue gives evidence 

 of the viscosity of a stratum. 



The tube is 14*5 inches, 36'8 centims., long, and 1*5 inches, 

 3"8 centims., in diameter, 9*75 inches, 24*8 centims., distant between 

 the terminals, a point T and a ring T'. At right angles a tube of 

 smaller diameter is attached 5 inches, 12*7 centims., long ; in this tube 

 is a stopper having a loop underneath from which is suspended by 

 two silk fibres, s, a piece of decarbonised iron, n n', § inch, 1*6 centims., 

 long, and 0*026 inch, 0'66 millim., in diameter. The stopper when 

 greased turns quite smoothly, and by turning it the needle can be 

 easily placed in any direction with regard to the tube. 



* " Phil. Trans.," Part II, vol. 174, p. 393. Separate copy, p. 220. 

 f " Phil. Trans.," Part I, vol. 171, p. 257. Separate copy, p. 392. 



