LIGHT. 123 



frame schemes of the universe as though it was formed for 

 man alone : painted by an artist of the sun, a man might not 

 represent so prominent an object of creation as he does 

 when represented by his own pencil. 



Light was regarded, by what was termed the corpuscular 

 theory, as being in itself matter or a specific fluid emanating 

 from luminous bodies, and producing the effects of sensation 

 by impinging on the retina. This theory gave way to the un- 

 dulatory one, which is generally adopted in the present day, 

 and which regards light as resulting from the undulation of a 

 specific fluid to which the name of ether has been given, 

 which hypothetic fluid is supposed to pervade the universe, 

 and to penetrate the pores of all bodies. 



In a Lecture delivered in January 1842, when I first 

 publicly advanced the views advocated in this Essay, I stated 

 that it appeared to me more consistent with known facts to 

 regard light as resulting from a vibration or motion of the 

 molecules of matter itself, rather than from a specific ether 

 pervading it ; jnst as sound is propagated by the vibrations 

 of wood, or as waves are by water. I am not here speaking 

 of the character of the vibrations of light, sound, or water, 

 which are doubtless very different from each other, but am 

 only comparing them so far as they illustrate the propagation 

 of force by motion in the matter itself. 



I was not aware, at the time that I first adopted the 

 above view, and brought it forward in my Lectures, that the 

 celebrated Leonard Euler had published a somewhat similar 

 theory ; and, though I suggested it without knowing that it 

 had been previously advanced, I should have hesitated in 

 reproducing it had I not found that it was sanctioned by so 

 eminent a mathematician as Euler, who cannot be supposed 

 to have overlooked any irresistible argument against it the 

 more so in a matter so much controverted and discussed as 

 the undulatory theory of light was in his time. 



Although this theory has been considered defective by a 



