^'ouS.Krff 1 ^oyal Microscopical Society, . SQS 
the glasses to be fought, and the manner in which the subject of 
aberration has been treated amply justifies my apprehensions. 
I point to the immersion lens as an irrefragible proof of the 
deficiencies of the corrections of old-fashioned glasses to grapple 
with some of the exquisite difficulties of microscopic research, and if 
my poor efforts shall in any way advance the excellence of defining 
power, especially in the higher range of investigations, I shall 
in the end feel amply rewarded. The work has been earnest and 
sincere. 
Note. — Dr. Pigott desires to have it stated that this paper was sent to the 
Koyal Microscopical Society on the 21st of May last. — Ed. M. M. J. 
VOL. II. 
Y 
