Dr. Young’s Lecture 
64, 
in the length of the axis. This opinion had derived very great 
respectability, from the most ingenious and elegant manner in 
which Dr. Olbers had treated it, and from being the last result 
of the investigation of Mr. Home and Mr. Ramsden. But 
either of the series of experiments which have been related, 
appears to be sufficient to confute it. 
X. It now remains to inquire into the pretensions of the 
crystalline lens to the power of altering the focal length of the 
eye. The grand objection to the efficacy of a change of figure 
in the lens, was derived from the experiments in which those 
who have been deprived of it have appeared to possess the 
faculty of accommodation. 
My friend Mr. Ware, convinced as he was of the neatness 
and accuracy of the experiments related in the Croonian Lec- 
ture for 1795, yet could not still help imagining, from the ob- 
vious advantage all his patients found, after the extraction 
of the lens, in using two kinds of spectacles, that there must, 
in such cases, be a deficiency in that faculty. This circumstance, 
combined with a consideration of the directions very judiciously 
given by Dr. Porterfield, for ascertaining the point in ques- 
tion, first made me wish to repeat the experiments upon various 
individuals, and with the instrument which I have above de- 
scribed as an improvement of Dr. Porterfield’s optometer : 
and I must here acknowledge my great obligation to Mr. 
Ware, for the readiness and liberality with which he intro- 
duced me to such of his numerous patients as he thought most 
likely to furnish a satisfactory determination. It is unnecessary 
to enumerate every particular experiment ; but the universal 
result is, contrary to the expectation with which I entered on 
the inquiry, that in an eye deprived of the crystalline lens, the 
