December 27, 1895.] 



SCIENCE. 



879 



War es ein Gott der diese Zeichen sohrieb, 

 Die niit gelieimnissvoll verborg'nem Ti-ieb 

 Die Kriitte der Natur urn mioli enthiillen 

 Und mir das Herz mit stiller Freude fiillen. 



The summary with which Hertz con- 

 cluded his famous lecture ' On the Relation 

 between Electricity and Light,' cited above, 

 is the most comprehensive statement of the 

 tendencies of modern electrical research 

 that I know of. I shall, therefore, conclude 

 my discussion with a translation of this 

 summary, hoping that I have succeeded in 

 paving the way to a clear understanding 

 of the following comprehensive language of 

 one of the most profound students of Fara- 

 day and Maxwell. Hertz speaks as follows: 



" l>ro longer do we see the flow of cur- 

 rents nor the heaping up of electricities in 

 conductors. We only see the waves in air, 

 passing through each other, dissolving and 

 uniting, intensifying and neutralizing each 

 other. Parting from the region of purely 

 electric we arrive step by step to purely 

 optic phenomena. "VVe have crossed the 

 pass; our path grows less steep and ap- 

 proaches a level. The union between light 

 and electricity which the theory surmised, 

 expected, predicted, has been accomplished, 

 comprehensible by the senses, intelligible 

 to our common intelligence. A broad veiw 

 into both regions greets us at the highest 

 point which we have reached, at the pass 

 itself The domain of optics is no longer 

 limited to ether waves, the length of which 

 is only a small fraction of a millimeter; it 

 extends to waves which are measured by 

 decimeters, meters, kilometers. But in 

 spite of this extension, this domain appears 

 to us, when viewed from here, as an appen- 

 dix only to the domain of electricity. This 

 last one gains the most. We see electricity 

 in a thousand places where formerly we 

 found no sure record of its presence. In 

 every flame, in every luminous atom, we 

 see an electric process. But even a non- 

 luminous body, as long as it radiates heat, 



is the seat of electric impulses. Thus the 

 domain of electricity is being extended over 

 all nature. It approaches us personally ; 

 we learn that in reality we possess an elec- 

 tric oi-gan, the eye. This is the view of the 

 things below, the view of details. The view 

 from this standpoint of the things above, the 

 view of the lofty peaks, the general aims, is 

 not less inviting. There lies directly before 

 us the question concerning direct actions 

 at a distance. Do they exist ? Among the 

 many which we believed to possess, one 

 only remains, gravitation. Does this one 

 also deceive us? The law, in accordance 

 with which it acts, makes it suspicious. In 

 another direction, not far away, is the 

 question concerning the nature of electric- 

 ity. It hides itself, when viewed from 

 here, behind a more specific question con- 

 cerning the nature of electric and magnetic 

 forces in space, and directly alongside of 

 this, rises the mighty chief problem con- 

 cerning the nature, the properties of the 

 medium which fills all space, the ether, its 

 structure, its rest or motion, its infinite ex- 

 tension or its finite boundary. Stronger and 

 stronger grows the appearance that this 

 question towers way above all the others, 

 that a knowledge of ether will reveal to us 

 not only the nature of former imponder- 

 ables, but also of old matter itself and its 

 innermost properties, gravitj' and inertia. 

 The quintessence of pi-imeval physical doc- 

 trines is preserved in the words that ' all 

 that is is made of water, of fire.' Physics of 

 to-day approaches the question whether 

 all that is is made of ether ? These things 

 are the ultimate aims of our Science, of 

 Physics. They are, to continue our simile, 

 the last ice-capped peaks of its highlands. 

 Will it ever be granted to us to place our 

 foot upon one of these peaks ? Will that 

 happen late ? Can it be soon ? We do not 

 know it. But we have gained for further 

 efforts a foothold which is a step higher 

 than those which were used before ; the 



