M. E. Edlund on the Nature of Electricity . 89 



In the sequel we shall make use of a proposition which has 

 not_, to our knowledge, been yet established as a principle in the 

 explanation of natural phenomena^ but which appears to us none 

 the less axiomatic. This principle is, that every thing which 

 takes place or is effected in external nature requires a certain 

 time. The time may be as short as we will, but is never =0. 

 '^Time and space are conditions indispensable to the existence 

 of natural phenomena '' is an a priori truth ascertained by expe- 

 riment in proportion as scientific methods for the measurement 

 of time and space have been improved. For example, it was 

 formerly believed that light and electricity propagated themselves 

 instantaneously; but better methods of observation have shown 

 that this is by no means the case. We may be perfectly assured 

 that a galvanic current does not at once arrive at its whole force, 

 and does not disappear without occupying a certain time in doing 

 so, independently of the extra currents which retard these two 

 phenomena. We must reject as absurd the proposition that the 

 action exerted by a material body upon another at a certain dis- 

 tance, or the repulsion of one molecule by another at a distance, 

 does not require time to propagate itself from the one to the 

 other. However short the time may be, it always exists, even if 

 it escapes our observation. When reciprocal action between two 

 material bodies or two molecules of sether commences, it does 

 not attain in a mathematical instant the full value determined 

 by the reciprocal distance. It must increase from zero to that 

 final value, and must have time for this. In like manner an 

 action cannot vanish or change its amount without time being 

 necessary for these effects. The above-formulated proposition, 

 " Every thing which takes place or is effected in external nature 

 requires a certain time,'^ niay, with regard to its importance, be 

 compared with that which may be said to constitute the founda- 

 tion of the mechanical theory of heat, and which is expressed in 

 the words "nothing springs from nothing" [ex nihilo nihil fit). 

 The proposition we have established must find its application 

 particularly in the domain of electricity, seeing that the great 

 velocity of propagation of this phenomenoii calls forth rapid mo- 

 difications in the reciprocal action exerted by the aether molecules 

 upon each other. According to the determinations given by 

 Fizeau and Gounelle, electricity is propagated in a copper wire 

 with a velocity of 180 metres in the miUionth part of a second; 

 so that in this brief fraction of time two molecules of sether can 

 diminish or augment their reciprocal distance by 360 metres, 

 and their action upon one another be modified in consequence. 

 The question now is whether this modification in the reciprocal 

 action can be accomplished with a velocity corresponding to the 

 rapid variation of the distance. Electrodynamic phenomena 

 furnish the answer. 



