WHAT IS ELECTRICITY ? 87 



electrical and magnetic effects. Such a person could then see the quick 

 ebb and flow and interchanges of attractive forces as we now see the 

 play of colors. Have you ever reflected that we may possibly have 

 some day an electrical spectrum — perhaps I should call it an attract- 

 ing-force spectrum — in which the electro-magnetic manifestations of 

 energy shall be spread out and differentiated, just as that part of the 

 energy which we receive from the sun and which we call light and 

 heat is now dispersed in the visible solar spectrum ? We regard to-day 

 the manifestations of the different colors of bodies — the tints of the 

 objects in the room — as the visible expression of the great law of con- 

 servation of energy. The energy which we have received from the 

 sun is making interchanges and is modified by the different molecular 

 structure of the different objects. Thus, a red body has absorbed, so 

 to apeak, certain wave-lengths of energy, and has transmitted or re- 

 flected back only the red or long waves of energy. The rest of the 

 energy has been devoted to molecular work which does not appeal to 

 us as light or even in certain cases as heat. If we suppose that radi- 

 ant energy is electro-magnetic, can not we suppose that it is absorbed 

 more readily by some substances than by others, that its energy is 

 transformed so that with the proper sense we could perceive what 

 might be called electrical color ; or, in other words, have an evidence of 

 other transformations of radiant energy other than that which appeals 

 to us as light and color ? 



I have thus far conducted you over a field that, in comparison with 

 what lies before us, seems indeed barren and churlish of results. Have 

 we, then, nothing upon which we can congratulate ourselves ? I can 

 only reply by pointing to the rich practical results which you can see 

 in the fine electrical exposition which we owe to the energy and liber- 

 ality of the citizens of Philadelphia. Although we must glory in this 

 exposition, it is the duty of the idealist to point out the way to greater 

 progress and to greater intellectual grasp. 



Perhaps we have arrived at that stage in our study of electricity 

 where our instruments are too coarse to enable us to extend our inves- 

 tigations. Yet how delicate and eflicient they are ! Compare the in- 

 struments employed by Franklin, and even by Faraday, with those 

 which are in constant use to-day in our physical laboratories. Frank- 

 lin, by the utmost effort of his imagination, could not conceive, proba- 

 bly, of a mirror-galvanometer that can detect the electrical action of a 

 drop of distilled water on two so-called chemically pure platinum plates, 

 or of a machine that can develop from the feeble magnetism of the earth 

 a current sufiiciently strong to light the city of Philadelphia. Let 

 him who wanders among the historical physical instruments of many 

 of our college collections stand before the immense frictional electri- 

 cal machine of Franklin's day, or gaze upon the rude electrometers 

 and galvanometers of that time, and contrast Franklin's machine 

 with the small Toepler-Holtz electrical machine which with a tenth 



