Dr. Wells's Observations 
380 
and to become unalterable by light, an effect might at the 
same time be produced by it upon vision, similar to that which 
I have just described. I had, indeed, in the course of a few 
years immediately preceding, applied Belladonna several times 
to my own eyes, without observing any change in my sight, 
beyond what I referred to the increased size of the pupils ; 
but as I had not looked for any other, I thought it possible, 
that some additional one might have happened, without my 
having perceived it. I resolved therefore to make the expe- 
riment anew. But to conduct it with precision, it was previ- 
ously necessary to know, to what extent 1 possessed the 
faculty of adapting my eyes to different distances. On this 
subject I had made many experiments with great care, nearly 
twenty years before, and had ascertained,* that with my left 
eye, which was more perfect than the right, I could bring to 
single points on the retina pencils of rays, which flowed from 
every distance, greater than that of seven inches from the 
cornea. In the mean time, however, my eyes had altered 
considerably, with respect to their seeing near objects dis- 
tinctly, and I had, in consequence, been obliged, not only to 
use convex glasses, but to change them several times for 
others of higher power. No dependance therefore being now 
to be placed in my former experiments, in regard to the pre- 
sent state of my sight, I repeated them, and found, to my 
great surprise, that the power I once possessed of adapting 
my eyes to different distances was entirely gone ; in other 
words, that I was now obliged to regard all objects, whether 
near or remote, in the same refractive state of those organs. 
1 found also, that my eyes, considered as mere optical instru- 
f Essay on Single Vision with two eyes, &c. p. 1 37. 
