SCIENCE. 



[N. S. Vol. II. No. 52. 



current of thought. This current starts 

 from the phenomena of electro-magnetic in- 

 duction. The tributary streams make it 

 stronger and stronger. It grows wider and 

 wider, and finally as if expanding bej'ond 

 the limits of our mental vision disappears 

 in the dim regions, which, according to 

 Faraday's surmises, connect the phenomena 

 of light, electricity, and magnetism. The 

 phenomena of electro-magnetic induction 

 inspired the prophetic mind of Faraday 

 with the belief that there must be an in- 

 visible mechanism connecting material 

 bodies, and that it is the activity of this 

 mechanism which makes us cognizant of 

 the existence of electric and magnetic forces. 

 He gave expression to this belief by intro- 

 ducing into his mode of thought and of de- 

 scription a new term, the term magnetic 

 curves or lines of magnetic force. At first 

 he gave us only their geometrical definition. 

 " By magnetic curves," he added in a foot- 

 note. Volume I., page 32, " I mean the lines 

 of magnetic force, however modified bj* 

 juxtaposition of poles, which would be de- 

 picted by iron filings ; of those to which a 

 very small magnetic needle would form a 

 tangent." But the intimate connection be- 

 tween the phenomena of electro-magnetic 

 induction and these curves, or lines of 

 magnetic force, convinced him that these 

 curves had an actual physical existence and 

 that they were not mere geometrical space 

 relations, of which the iron filings give 

 us a convenient material picture. He 

 seemed to be aware that the nature of 

 these new physical existences could not 

 be revealed by a studj^ of phenomena 

 like those of electro-magnetic induction, as 

 long as these phenomena could be observed 

 in bodies of finite dimensions only, and this 

 being the case then he would naturally ex- 

 pect that the road leading to the under- 

 standing of the lines of force was bj' way of 

 the phenomena which can be traced with 

 certainty to the ultimate elements of mat- 



ter, to atoms and molecules. This would 

 have been the voice then M'hich called Far- 

 aday away from his researches in electro- 

 magnetic induction and bade him rise 

 higher and higher until he reached heights 

 so lofty that onlj^ a genius like that of Max- 

 well could reach him. This is, I venture 

 to suggest, why Faraday's discoveries in 

 electro-magnetic induction led him into re- 

 searches of what may be called the atomic 

 and molecular region of the science of 

 electricity. From this point of view, 

 the chronological order appears quite 

 natural in which his researches in electro- 

 chemistry, voltaic electricity, specific in- 

 ductive capacity of dielectrics, disruptive 

 discharges through gases, animal electricity, 

 action of magnets on light, on metals and 

 their compounds, on gases, on crystals, etc., 

 follow each other in rapid succession. The 

 numerous discoveries revealed by these pro- 

 found researches convinced the great phi- 

 losopher that his work was in the right di- 

 rection. With steady aim he forced his diffi- 

 cult journey ahead with giant sti-ides. The 

 most vigorous years of his life were con- 

 sumed in gathering a vast amount of evi- 

 dence with which to reveal before our eyes the 

 phj^sical nature of the lines of force, his first 

 inspiration, and banish the old superstition 

 of direct action at a distance. With re- 

 newed vigor he returned to this favorite 

 subject toward the closing years of his life. 

 His research ' On the Lines of Magnetic 

 Force ; Their Definite Character, and Their 

 Distribution Within a Magnet and Through 

 Sjmce' (Philosophical Transactions, 1852, 

 page 1), given in the twenty-eighth series of 

 his ' Researches,' mark the beginning of the 

 last epoch of his great work. It pi-epares 

 us to enter into Faraday's innermost 

 thoughts and see that inspiration and those 

 visions which guided his steps for twenty 

 years. The essays which now follow, ' On 

 the Lines of Magnetic Force,' ' On the 

 Physical Character of the Lines of Magnetic 



