MICROSCOPY. 



2^3 



A tinted Condensing Lens.— Prof. E. Abbe, of Jena, whose 

 New Illuminating Apparatus seems not very unlike the common 

 English "Webster Condenser" modified so as to be available in 

 the limited space allowed between the stage and mirror in conti- 

 nental microscopes, suggests the employment as a condensing 

 lens, when lamplight is to be employed, of a large glass globe 

 filled with water colored of a moderate blue tint. This is placed 

 between the flame and the plane mirror below the condenser, and 

 gives, according to the depth of color employed, a nearly white 

 or a decidedly blue illumination. 



Wide Angled Objectives. — Having been a member of the 

 committee of the Memphis Microscopical Society appointed to 

 make certain tests of various object-glasses, it may prove of in- 

 terest to make public the results of our investigations. 



Dr. Carpenter lays down as a fixed law the statement that "all 



the superior value of objectives of moderate or even comparatively 

 small angle of aperture for ordinary working purposes ; the special 

 utility of the very wide apertures being limited to particular 

 classes of objects." (Carpenter, 4th ed., p. 172). 



It is now claimed that this no longer holds good ; and our in- 

 vestigations were undertaken simply with a view to testing the 



The glass we selected as the representative of the wide angles 

 was a "four-system" immersion ^th, of nearly 180°; the narrow 



by leading Germany, France an I 



and comprised both dry and net systems. Bearing in mind the 

 theory that the wide angles are only superior on diatoms and with 

 oblique illumination, we discarded diatom tests, and used only 

 central light. 



The first slide selected was a specimen of mosquito scales, dry. 

 Under the T ' ff th of nearly 180°, this object was beautifully defined, 

 the structure of the intercostal space-. longitudinal ribs and ter- 

 minal spines being all sharply aid clearly shown. Even under so 



esult that while not giving so good definition under low power 



successively brought to bear on the same c 



