108 Di\ G. Gore on the Relation of Volt a 



General Remarks and Conclusions. 



The currents were manifestly occasioned by difference of 

 pressure at the upper and lower electrodes, and apparently 

 by that circumstance alone. They were not due to the unequal 

 temperatures of the room or to heat evolved by the pressure 

 at the lower electrode, nor to air or impurities dissolved in the 

 water, nor to bubbles of gas &c. adhering to the electrodes, 

 nor to greater conduction resistance of the electrolyte in a 

 downward than in an upward direction, nor to difference of 

 altitude of the electrodes except so far as it affected the 

 difference of pressure ; nor were the deflexions caused by 

 mechanical disturbances of the galvanometer or by any 

 magnetic substance near it. They were also not produced by 

 thermoelectric action due to greater chemical heat at the 

 lower electrode. In all the cases in which a diaphragm was 

 employed, the electric current due to pressure was not per- 

 ceptibly affected by any current produced by flow of the 

 electrolyte through the partition ; the considerable conduction 

 resistance of the septum, however, largely reduced the quantity 

 of the current due to pressure. 



The results of the experiments in general indicate that the 

 upper and lower ends of a column of an electrolyte are not in ex- 

 actly the same physical or chemical state ; that a fixed difference 

 of condition of the liquid and metal was gradually produced 

 when the tube was placed vertical, and that this condition re- 

 quired several minutes in order to attain its maximum. That 

 both the metal and the liquid are altered by the pressure is 

 shown, not only by the fact that a change of either affects the 

 amount (and in some cases also the direction) of the current, 

 but also by the circumstance that the period of time required to 

 reverse the condition, and the current, by reversing the tube 

 varies with a change of metal as well as of liquid. These cir- 

 cumstances are interesting, and indicate the gradual produc- 

 tion by pressure of a state of mechanical stress of the lower 

 electrode and of the liquid near it ; and as action and reaction 

 are always equal and opposite, the state of stress of the metal 

 must be attended by one of counter stress of the liquid. The 

 same states of stress might of course be produced by means 

 of a hydraulic press, a lever, &c, or by centrifugal action 

 during rapid whirling of the tube. As the increase of pressure 

 and stress at the lower electrode was followed by the production 

 of a permanent electric current, it must also have been followed 

 by increased energy of chemical union of the metal and liquid 



