OPTICAL IMAGES. 



lens, but on the same side of it with the object, as explained 

 in (36). 



61. With the same lens the dispersion will increase with the 

 refraction, and consequently the more the image is magnified 

 the greater will be the dispersion and the aberration, and the more 

 confused and indistinct the image. 



62. It might naturally therefore be supposed that if two lenses 

 made of different transparent substances produce images of the 

 same object at the same distance from them, and consequently 

 equally magnified, they would produce the same dispersion and 

 aberration. It is found, however, that this is not the case. A 

 lens of diamond and a lens of glass may be so formed that the 

 same object being placed at equal distances from them, the 

 distances at which the violet image will be produced shall be 

 exactly equal, but the same equality will not prevail between the 

 distances of the red image and those of the intermediate colours. 



112 



