250 ON LIGHT. 



be a movement, or an influence, we must admit in that 

 movement or influence a similar capacity for analysis or 

 composition, or else have recourse to some unknown 

 modification of the one or the other, leaving the phe- 

 nomenon as unexplained as before. There may, for 

 instance, be a great variety of such movements, all 

 luminiferous, but not all alike ; and some may be de- 

 stroyed, or some exaggerated, in the act of reflexion or 

 transmission. 



(34.) The key to this mystery, up to a certain point, 

 was furnished by Newton, in his analysis of white light 

 by prismatic refraction. A full account of the manner 

 in which that analysis is performed, of the phenomena 

 it presents, and of the nature and subdivisions of the 

 " Prismatic spectrum," is given in our lecture on " The 

 Sun," 29, to which, to avoid repetition, we refer our 

 readers. Let us, however, consider what kind of general 

 theoretical interpretation we are entitled to put on this- 

 analysis. Now, the first and most obvious conclusion is, 

 that the phsenomenon we have to deal with, is not what 

 in the accuracy of modern scientific language is under- 

 stood by the term " analysis." It is the separation and 

 redistribution (according to degrees of a certain quality 

 common to all its elements viz., that of REFRANGI- 

 BILTTY) of a mixture, rather than the dzalysis of a true 

 compound. The simile by which we there illustrated it 

 is so far exact. A glacier moraine might be redistributed 

 by tidal action over the floor of the Ocean ; the great 

 blocks left in situ, or little moved the smaller forming 

 shingle, gravel beds, sandstones, or incoherent muddy 



