294 MODERN SCIENCE READER 



valid and conclusive requisition of an ethereal medium 

 depends on the wave theory of light, one of the founders 

 of which was Dr. Thomas Young, at the beginning of last 

 century. 



No ordinary matter is capable of transmitting the undu- 

 lations or tremors that we call light. The speed at which 

 they go, the kind of undulation, and the facility with which 

 they go through vacuum, forbid this. 



So clearly and universally has it been perceived that 

 waves must be waves of something something distinct from 

 ordinary matter that Lord Salisbury, in his presidential 

 address to the British Association at Oxford, criticized the 

 ether as little more than a nominative case to the verb to 

 undulate. It is truly that, though it is also truly more than 

 that ; but to illustrate that luminif erous aspect of it, I will 

 quote a paragraph from the lecture of Clerk Maxwell's to 

 which I have already referred : 



The vast interplanetary and interstellar regions will no longer be 

 regarded as waste places in the universe which the Creator has not 

 seen fit to fill with the symbols of the manifold order of His kingdom. 

 We shall find them to be already full of this wonderful medium; so 

 full that no human power can remove it from the smallest portion of 

 space, or produce the slightest flaw in its infinite continuity. It 

 extends unbroken from star to star ; and when a molecule of hydrogen 

 vibrates in the dog-star, the medium receives the impulses of these 

 vibrations, and after carrying them in its immense bosom for several 

 years, delivers them, in due course, regular order, and full tale, into 

 the spectroscope of Mr. Huggins, at Tulse Hill. 



This will suffice to emphasize the fact that the eye is truly 

 an ethereal sense-organ the only one which we possess, the 

 only mode by which the ether is enabled to appeal to us 

 and that the detection of tremors in this medium the 

 perception of the direction in which they go, and some in- 

 ference as to the quality of the object which has emitted 

 them cover all that we mean by "sight" and "seeing." 



I pass then to another function, the electric and magnetic 

 phenomena displayed by the ether ; and on this I will only 

 permit myself a very short quotation from the writings of 



