INFLUENCE OF ELECTEICITY ON VEGETATION. 103 



successive formation and destruction of a magnet by induction, 

 vk'liich in turn induces in a wire bound round it corresponding- 

 electric currents. 



The eftects of current galvanic electricity on vegetation may 

 be supposed nearly identical with those of frictional electricity, 

 as the chief effects of the latter have been described as being- 

 produced by it in its dynamical state ; and hence the consider- 

 ation of this form of electric power resolves itself rather into a 

 consideration of its sources as regards vegetation. The obser- 

 vations already made, witii respect to the close connexion between 

 chemical action and electricity, apply to all forms of current 

 electricity, whetlier of frictional or galvanic origin ; such cur- 

 rents are constantly being formed both by the gradual neutrali- 

 zation of atmospheric electricity, and also by the chemical 

 changes continually going on in the soil and in the organs of 

 growing plants. 



We may now proceed to inquire in how far the plans proposed 

 in England and America for the application of atmosplieric and 

 galvanic electricity are calculated to assist vegetation ; consider- 

 ing, firstly, in how far they are adapted to the object in view, 

 and, secondly, whether tlie eftect desired, if obtained, is likely to 

 promote the growth of plants ? From some of the statements 

 which arose out of Dr. Forster's description of his original expe- 

 riments, it was evident that a very indefinite conception was 

 entertained of the mode in which such an apparatus could act, 

 some seeming to imagine tliat the wire, in consequence of its re- 

 lation to the axis of magnetic power in the earth, would be in 

 the same position as a wire in the vicinity of the pole of a 

 magnet, and that consequently a current would be established 

 throughout the entire length of the wire ; whilst others viewed 

 it merely as a means of discharging or collecting the free elec- 

 tricity of the atmosphere. When a magnet is moved in a certain 

 position to a circle of wire, an electric current is generated in the 

 wire, or, if the magnet be kept stationary whilst the wire is moved, 

 the same effect is produced ; and by extending this prin- 

 ciple, and moving a portion of a wire circle so as to cut the lines 

 of magnetic influence of the earth, an electric current may be 

 obtained ; but of course in this case, as with an artificial magnet, 

 either the wire or the magnet must be moved ; if both are 

 stationary, or, what is the same thing, if both are moved at the 

 same rate and in tlie same direction, no current can be produced : 

 hence we see at once that, upon tlieoretical reasons, we cannot 

 expect any current to be generated by induction in a wire sus- 

 pended above the surface of the earth, with the intention of 

 cuttins: its line of magnetic force ; and the truth of this is more- 

 over borne out by experimental evidence, as no current whatever 



