64 GOETHE'S "FARBENLEHRE." 



elongation of his spectrum was due to the fact "that 

 light is not similar or homogeneal, but consists of 

 difform rays, some of which are more refrangible 

 than others; so that, without any difference in their 

 incidence on the same medium, some shall be more 

 refracted than others; and therefore that, according 

 to their particular degrees of refrangibility, they were 

 transmitted through the prism to divers parts of the 

 opposite wall. When," continues Newton, " I under- 

 stood this, I left off my aforesaid glass works; for I 

 saw that the perfection of telescopes was hitherto 

 limited, not so much for want of glasses truly figured 

 according to the prescriptions of optick authors, as 

 because that light itself is an heterogeneous mixture of 

 differently refrangible rays; so that were a glass so 

 exactly figured as to collect any one sort of rays into 

 one point, it could not collect those also into the same 

 point, which, having the same incidence upon the 

 same medium, are apt to suffer a different refraction." 



Goethe harped on this string without cessation. 

 " The Newtonian doctrine," he says, " was really dead 

 the moment achromatism was discovered. Gifted men 

 our own Kliigel, for example felt this, but expressed 

 themselves in an undecided way. On the other hand, 

 the school which had been long accustomed to support, 

 patch up, and glue their intellects to the views of Newton, 

 had surgeons at hand to embalm the corpse, so that even 

 after death, in the manner of the Egyptians, it should 

 preside at the banquets of the natural philosophers." 



In dealing with the chromatic aberration of lenses, 

 Goethe proves himself to be less heedful than usual as 

 an experimenter. With the clearest perception of 

 principles, Newton had taken two pieces of cardboard, 

 the one coloured a deep red, the other a deep blue. 

 Around those cards he had wound fine black silk, so 



