u 
MECHANICAL PORTION OF THE MICROSCOPE. 
are attached by a screw to an adapter, which is inserted by a 
bayonet joint into the body of the microscope. They are very 
carefully corrected for chromatic and spherical aberration, and 
are adjusted for a glass cover xio of an inch thick. With this 
correction, which is permanently fixed, this class of objectives 
will perform very nearly as well if the thickness of glass cover- 
ing an object is one-eightieth or one hundred and twentieth of 
an inch in thickness. These objectives will resolve nearly all 
the test objects mentioned in works on the microscope. The 
i inch of this class, with eye-piece ITo. 2, with good illumina- 
tion, will show very clearly all the lines and dots on the JPleu- 
rosigma angulata. The inch will resolve the Namcula 
Baltica and Hijppocamjpus in balsam, and will resolve the 
PleuTOsigma angulata when mounted dry. All this class of 
objectives answer well for investigations in botany, entomology, 
and pathology. The low price at which this class of object- 
ives is furnished, will commend them to all who desire cheap, 
but good object-glasses. 
J. & W. GRUNOW & GO’S ILLUSTRATED 
