moisture. In the end of one of the boxes was in- 

 serted a thin piece of zinc, the height and breadth 

 of the box, and in the other end a piece of copper 

 of similar size. Both were pressed down almost to 

 the bottom of the box, and were connected above 

 ground by a copper wire soldered to their projec- 

 tions. Thus arranged the box was an earth-battery, 

 the like of which has been used for running clocks 

 and other machinery requiring but little current, 

 and also by previous experimenters in electro- 

 horticulture. The results were always in favor of 

 the seeds planted in the earth-battery, the plants 

 resulting from them being from twenty per cent, 

 to forty per cent, in advance of those in the box 

 without the zinc and copper. 



Briefly, what goes on in the earth-battery is as 

 follows : some compounds in the moist, soil act 

 chemically upon the zinc (positive element), one of 

 the results of which is that a current of electricity 

 is generated; this passes through the soil to the 

 copper (negative element), up the copper to the 

 wire above the soil and through it to the zinc, 

 making a circuit. By inserting a sensitive galvano- 

 meter into this wire a current can be proved to be 

 flowing by the deflection of the needle. It is this 

 continuous current going through the soil which 

 acts upon some of the compounds in it, and also 

 upon the roots of the plants, giving us the good 

 results we generally obtain. Ordinary galvanic 

 cells, such as the " gravity," can be used to fur- 

 nish the current; all that is needed is to attach the 

 wire from the positive electrode of the battery to 



