OPTICAL IMAGES. 
the same proportion as that in which the distance l'"i, is greater 
than o" L. 
If we suppose the object o'" to he 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. 
96 
