338 COLORfFICATION IN GENERAL. 



The motions, which the different colorific 

 rays describe, in passing through different me- 

 dia, are so regular and uniform, that these 

 motions are reducible to mathematical princi- 

 ples, and can be illustrated and proved by ma- 

 thematical rules. Of the utmost importance, 

 it must, nevertheless, be confessed, is the dis- 

 tinction which exists between the illustration of 

 those phenomena, by mathematical rules, and 

 the causes by which those phenomena are pro- 

 duced. Each of these objects has its own 

 principles, and he who confounds the one with 

 the other, involves himself in error and in con- 

 fusion. To the mathematician, the office be^ 

 longs of ascertaining the quantity of matter 

 which the different rays contain, and the extent 

 of space which they fill, the velocity they 

 describe, and the degree of mechanical effect (if 

 any) which they produce on other bodies. To 

 the chemist, the province belongs, of explor- 

 ing the quality of the material? of which differ- 

 ent colors are composed, and the best means by 

 which they may be factitiously prepared. To 

 the physiologist and metaphysician, are the 

 higher duties allotted, of ascertaining the rela- 



Jemy was also as well acquainted as we are with the refraction 

 which light undergoes, in passing from air into water or into 

 glass, and that he has given tables of it for every ten degrees 

 of the angle of incidence. 



