AERIAL COLUMN AND AERIAL ELECTROSCOPE. 87 



There is some sort of impediment to the wol'ion of the electric But progres- 



fliiid along the column, probably caused by a reluctance in the '*'^*^* 



%inc plates to part with the superior quantity of e/cf/rfc J?KJrZ 



they must possess when united with copper, to produce 



their electrical ecjuilibrium. The consequence is : that, 



after having observed the divergence of \.\\e gold leaves in bo(Ii 



electrometers, if one of the extremities of the column be made 



to, communicate with the ground ; by which the gold Igrvgs fall 



on this sidC;, and they diverge more on the other side; it requires 



a long time, in some cases many hours, for the same divergences 



to be restored. 



15. There is an entertaining experiment, which may lead to Similarity be- 

 some discovery respecting the physiology of vegetables. Each ^i^^^ ^^ ^j^^^ ^^_ 

 of the electrometers of the column may be made to imitate the iumn, and that 

 sensitive plant (mimosa sensitiva :J for, as the contact of one > 



of the extremities of the co/«/7m produces the/b// of the ^oW 

 leaves on this side, which rise slowly ; the contact of the sen- 

 sitiue plant makes its leaves /«//, and they also rise slowly. This 

 analogy of slow effects, pointing oat some general analogy 

 between their causes, must render us cautious not to assign 

 hastily to some \3gu.e property the effects that we may follow 

 distinctly in their process, such as those of the electric column ; 

 for they may lead us, in time, to the discovery of causes, in 

 those phaenomena which now appear the most obscure. 



16. The lid part. Sir, of the same paper in your iournal, "^J^^. '".^pidity 



'^ . I r J •' ' of elective cir- 



concerns the ele. trie column in its phaenomena as an aerial dec- dilation influ- 



tioscope, and contains the observations which I had already '^"'^^'^ ^y ^""^'^ 

 ' . , , . r,.> ■ \ r • 1 ' external cause, 



made wjth that instrument. Ihis ciass or experiments relates 



to the opinion of Dr. Maycock, forasmuch as they prove, not 



only a constant motion o( the electric Jluid in the column, but 



that some external cause influences much the rapidity of its 



motions ; an object the explanation of which I had postponed. 



17. These changes -are seen, when the extremities oi the As shown by 



,. , ... , the aerial elec- 



columnare not made to communicate immediately with eacri ^^.^^j,^ 



other ; but only by the alternate strikings of a body suspended 



betvx'eeu them, taking some electric fluid from the positive 



side, and bringing it back to the negative. Now, tlie more 



rapidh the motion of the electric fluid in the column, the moic 



numerous are the sirikings in a given time; and the difference 



is 



