C 2 f tt DISCOURSE ON THE STUDY 



splendour exceeds by many hundred times that of the 

 sun itself, although we may not deny the truth of 

 the assertion, we cannot but feel the keenest cu- 

 riosity to know how such things were ever made out. 

 (18.) The foregoing are among those results of 

 scientific research which, by their magnitude, seem 

 to transcend our powers of conception. There arc 

 others, again, which, from their minuteness, would 

 appear to elude the grasp of thought, much more of 

 distinct and accurate measurement. Who would not 

 ask for demonstration, when told that a gnat's wing, 

 in its ordinary flight, beats many hundred times in a 

 second ? or that there exist animated and regularly 

 organized beings, many thousands of whose bodies 

 laid close together would not extend an inch ? But 

 what are these to the astonishing truths which 

 modern optical enquiries have disclosed, which teach 

 us that every point of a medium through which a ray 

 of light passes is affected with a succession of periodi- 

 cal movements, regularly recurring at equal intervals, 

 no less than five hundred millions of millions of times 

 in a single second ! that it is by such movements, 

 communicated to the nerves of our eyes, that we 

 see : nay more, that it is the difference in the fre- 

 quency of their recurrence which affects us with the 

 sense of the diversity of colour ; that, for instance, 

 in acquiring the sensation of redness our eyes are 

 affected four hundred and eighty-two millions of 

 millions of times; of yellowness, five hundred and 

 forty-two millions of millions of times ; and of violet, 

 seven hundred and seven millions of millions of times 

 per second.* Do not such things sound more like 



* Young. Lectures on Nat. Phil. ii. 627. See also Phil. 

 Trans. 1801-2 



