the same proportion as that in which the distance I'"L is greater 

 than O'"L. 



If we suppose the object o'" to be gradually removed from the 

 lens, so as to assume successively the positions o", o', &c., the 



Fig. 21. 



image will gradually approach the lens, assuming successively 

 the positions i", i', &c., and the linear dimensions of the object 

 and image being still in the proportion of their distances from the 

 lens, the image will necessarily decrease as the distance of the 

 object from the lens increases. 



30. Now, it might be imagined that by removing the object to 

 distances increased without limit, the distance of the image from 

 the lens would be decreased without limit. This, however, is not 

 the case. "While the object recedes through great spaces, its image 

 approaches the lens through very small spaces, and when the object 

 has been removed to a certain distance, the image is found to 

 become sensibly stationary, not being capable of approaching nearer 

 to the lens than a certain minor limit of distance, even though the 

 distance of the object should be augmented indefinitely. 



