18 Mi\ Charles Tomlinsons 



thus in both instances the same in point of nodal arrange- 

 ment as when mercury, oil, water, &c., were employed. 



110. These results were obtained from a vast number 

 of trials, all of which, except those now stated, were unsuc- 

 cessful. It was, therefore, necessary to inquire in what 

 consisted our want of success in so many trials, so as to 

 obviate the causes of failure and be able to produce these 

 effects at will. As our trials had been confined to the two 

 conical glasses before mentioned, and having succeeded but 

 twice, I supposed it possible that in consequence of the 

 severe vibratory action to which these glasses had long- 

 been subjected they had lost, in great measure, their nodal 

 properties, if I may so speak, their particles undergoing a 

 certain change, which though producing notes by vibration, 

 did so without a strict and spontaneous division into vibrat- 

 ing sectors.* I, therefore, procured other glasses and on 

 covering the exterior surface as before with lycopodium 

 was gratified by the production of the trains every time I 

 attempted their formation, and found that in proportion 

 as the glass was new so were the trains vs^ell defined and 

 perfect in their formation. They are produced by one bold 

 stroke of the bow, and if not produced at once it is seldom 

 of any avail to apply the bow a second time. 



111. There was also another cause which in the former 

 trials militated against success ; the glass and powder were 

 always kept quite dry, and after each trial the glass was 

 well cleaned with a dry cloth and sometimes with soft lea- 

 ther ; this produced a disturbance of electricity which inter- 

 fered greatly with the success of the experiment which 

 may be probably thus explained ; the surface of the glass 

 both exterior and interior acquired positive electricity from 

 the cloth or leather, the latter being negative, the powder 

 being sifted upon the exterior surface of the glass partici- 

 pated in electricity also in a positive state ; its attempts, 

 therefore, to enter the glass would be repelled, at least to a 

 degree sufficient to prevent a symmetrical arrangement of 

 figure. I, therefore, found this objection obviated by pre- 

 paring the glass with powder, &c., and allowing it to re- 

 main several minutes at rest previous to the experiment. 



• It is known tliat tlie glass plates employed in Chladni's experiments by 

 frequent use become incapable of producing the acoustical figures. 



