ON THE ELECTRIC COLUMN. 



87 



negative, but in a^egree which can merely affect the gold 

 leaf electroscope, be applied to one extremity, ti)e eiFect is 

 instantly perceived at the other. This agaiii is the same as 

 ila stream of water were introduced at one side of the pOnd 

 of the above example, and an opening made at the oppo- 

 site side ; for a current would be diiectly produced through 

 the pond. 



Exp. 5. After having disturbed the state of the diver- Exp. 5. 

 gences at the extremities of the column, by placing- a finger 

 on one of them, the mode of reproducing speedily the for- 

 mer state is, to lay the fingers on both extremities together, 

 and reuttove them at the same instant: if this last condition 

 be really obtained (which is not easy] the original divergences 

 are restored. 



These experiments cannot leave any doubt, that the phe- A fluid set ia 

 notnena of the column, as well as the electric part of those ™o^'*^"' 

 of the pile, are produced by -ajluid set in motion. 



Exp. 6. In the same case as that of the above experi- Exp. 6, 



ments, namely, when the divergences are not too great, if 



one side of the column be placed in communication with the 



ground, the effects of the contact on the other side are so Effect like 



similar to those produced in the same manner on the leaves l"*^^*^ on the 

 ... . . leaves of the 



of the mimosa seusitiva, that this conformity of effects seems sensitive plant. 



to indicate some analogy between the causes: both contacts 

 make the leaves fall ; they rise again, but it requires, some 

 time. Th^re is an objection against the idea tliat the phe- 

 nomenon of tlie plant is electric; because in the colnmn the 

 same effect is produced, at one side by imparting, and at 

 the other by taking off, some electric jiuid. This objection 

 however is not absolute, for we do not know all the actions 

 of organic bodies on the electric jiuid', but if it is not this, 

 it must be some other fluid, which is acted upon by the 

 contact of the plant. In general, we are very little ad- 

 vanced in the knowledge of the subtile agents operating 

 in terrestrial phenomena ; and as we cannot make any real 

 progress in this knowledge but by endeavouring to increase, 

 by observation and experiments, the number of the pheno- 

 mena which have analogies with each other in some respect, 

 it might be useful to follow an attentive comparison, at dif- 

 ferent times and in dift'eient arrangements of circumstances, 



- btitvvteu 



