REPORTS FROM THE SECTIONS. 181 
ell seen without change of focus. In flatness of field or marginal 
4 ition this glass is not any better than Zeiss’s }th or Powell 
and Lealand’s 4th. In all wide-angled objectives which I have ever 
Seen this appears to be their weakest point, and the one where 
there is most room for improvement, though perhaps improvement 
m this point is scarcely necessary, as these lenses are mostly em- 
n 
resolving power with glycerine is, to quote Mr. Tolles, stronger 
By glass, glycerine immersion, Wenham’s reflex and 
T can now easily resolve (into striz) the most attenuated 
ven 
‘ rag particularly hard slide of @ pellucida in balsam gi 
Jn point of external finish and mechanical perfection this 
aes 
is oil in mession .cliective | y shown to mem- 
ersion | jective has been already “4g ewe 
the Society at one of the Microscopie Section meetings, 
-heIple of construction ably ined, and its perfor- 
own by Mr, Hirst, I will only mention that its air angle 
