THE FIELD OF EXPERIMENTAL RESEARCH. 123 



scientific research, not alone as adding to the sum total of knowledge 

 and for the admirable training it gives, but because it can not fail to 

 have an ultimate practical effect. Discoveries which at first seem to 

 have no useful nor practical outcome are often the very ones which 

 underlie development of the greatest importance in the arts and 

 industries. 



The work of Hertz upon electric waves was to the physicist a grand 

 experimental demonstration, tending to prove the truth of the elec- 

 tro-magnetic theory of light, and subsequent progress was profoundly 

 influenced by it, though no practical use followed at once. The phys- 

 icist to-day may see in the wireless telegraph only an extension of 

 Hertz's original work, for he need not consider the commercial or 

 economic outcome. He ma}^, however, recognize the fact that in the 

 wireless telegraph, as developed by Marconi, practice calls for a 

 broader theoretical view. Certain elements of construction and 

 adjustment of apparatus, at first used and regarded as essential from 

 a theoretical standpoint, have already been laid aside. The radiator, 

 with its large polished brass spheres and special spark gap, has been 

 found of no more effect than the simple pair of small balls ordinarily 

 constituting the terminals for high potential discharges. It has been 

 found that the transmitting and receiving apparatus do not require to 

 be attuned, and that the receiving coherer is not the true recipient of 

 the electric wave or disturbance in the ether. 



These later developments are, in fact, departures, more or less wide, 

 from the principles underlying the Hertz demonstration. A vertical 

 wire is charged to a high potential and discharges to earth over a 

 spark gap. During the discharge the wire becomes a radiator of elec- 

 tro-magnetic pulses or waves, regardless of the spark radiation. The 

 receiving vertical wire is likewise alone relied upon to absorb the 

 energ}". Being in the path of the electro-magnetic wave conveyed in 

 the ether from the transmitting wire, it becomes the seat of electro- 

 motive forces which break down the coherer. This, in substance, 

 may be considered as a series of small or microscopic spark gaps 

 which can be crossed by the comparatively^ low potentials developed 

 in the receiving wire. We are thus taught to recognize the fact that 

 the refinements in methods and apparatus needed for a delicate phys- 

 ical demonstration as of the Hertz waves in this instance may often 

 be laid aside in practical application, where the end to be achieved is 

 different. The sudden discharge of the Marconi transmitting wire 

 may possibl}^ give rise to a series of oscillations or high-frequency 

 alternating waves in the wire; but since the first half of the first wave 

 at each discharge will have the greatest amplitude, it is doubtful if 

 those which follow in the short train have any decided effect upon the 

 receiver. According to this view the fact of the discharge being 

 oscillatory may, indeed, have no essential relation to the work done. 



