484 Mr. 1\. Sabine on Electricity disengaged 



It was two minutes before the disturbed surface of the mer- 

 cury had resinned a condition similar to that of the undis- 

 turbed. 



Surface B scraped ; deflection =185 divisions left, = 0*051 

 volt. Then left at rest. 



After 15 seconds, 



deflection 



= 75 div 



isions left. 



„ 30 



77 



?> 



45 



7) 



„ 45 



73 



V 



30 



37 



„ 60 



» 



37 



15 



77 



„ 75 



73 



» 



10 



77 



» 90 



73 



73 



3 



33 



Instead of using a scraper, the point of a glass tube was next 

 inserted in the mercury, and air blown through so as to keep 

 its surface in continued motion and to break up any covering 

 of suboxide. The 'electromotive force between the moving 

 and quiet surfaces was then observed and similar results re- 

 corded. 



In order to find whether this current might be due to ther- 

 moelectricity resulting from heat developed by the motion, 

 the following experiment was made. 



A vessel of heated mercury was provided, and, by means of 

 a pipette, a quantity introduced into one of the compartments. 

 The deflection consequent on the sudden change of tempera- 

 ture was observed as soon as it became steady. Heated mer- 

 cury introduced into A. Temperature of A rose from 22°*5 C. 

 to 27°-8 C. Temperature of B 22°-5 C. Deflection =35 di- 

 visions right (of the same galvanometer). After an interval 

 of ten minutes, heated mercury was introduced into B. Tem- 

 perature of B rose from 24° C. to 29°'5 C. Temperature of 

 A 23 0, 5 C. Deflection =40 divisions left. It was evident 

 that whilst a difference of temperature of 5°*5 C. occasioned 

 only a deflection of about 40 divisions, a difference of 20° C. 

 to 25° C. would have been required to produce effects equal 

 to those observed through the scraping, whereas, during 

 the whole of the previous readings, the temperature of 

 the mercury had not varied in either of the dishes more 

 than 1° C. ; the currents were therefore not due to heat. 

 The only other conclusion is that the metallic condition of 

 the surface of the mercury is changed by the scraping, such 

 as would result from a very thin film of mercurous oxide 

 being pushed aside and exposing metallic mercury or a less 

 oxidized surface to the action of the liquid. It is in the 

 highest degree probable, indeed, that mercury, when exposed 

 at ordinary temperatures to air or water, never presents a 

 really metallic surface, or, if it ever does so, that this condi- 



