263 
i0n. 
MARK STIRRUP, P.G.S. 
c^;e£* 
JOHN BOYD. 
CL0wndU 
CHAS. BAILEY, P.L.S. 
A. BROTHERS, P.R.A.S. 
R. E. CUNLIFPE. 
ALEX. HODGKINSON, B.Sc., M.B. 
F. NICHOLSON, F.Z.S. 
T. ROGERS. 
THEODORE SINGTON. 
J. TATHAM, B.A., M.B. 
On the Diffraction of MicrosGopic Objects in relation to 
the Resolving Power of Objectives” by Dr. Hodgkinson. 
That property of an objective in virtue of which very 
minute closely approximated markings, whether lines, dots» 
or apertures, are discerned is termed its resolving power, a 
function the importance of which, in microscopic investiga- 
tion, it would be difficult to over-estimate. 
For a long time, this property of Objectives was supposed 
to be directly due to their capacity for taking in a large 
quantity of light from the object, and thus forming a more 
intensely illuminated conjugate image. This idea was sup- 
posed to be strengthened by the fact that such structures 
as the above were seen to the greatest advantage when 
viewed with objectives of wide angle of aperture; in other 
words, by such as were specially constructed for receiving 
and bringing to a remote conjugate focus, a large proportion 
of the rays diverging from the several parts of a near 
object. Hence the introduction of the immersion system 
of objectives, the chief feature of which is their capacity 
to take in a widely divergent pencil of rays. 
To Professor Abbe, the distinguished scientist of Lena, is 
