ELEMENTARY 
CHEMICAL MICROSCOPY. 
CHAPTER I. 
OBJECTIVES AND OCULARS. 
The modern compound microscope, in any one of its many 
complicated forms employed by chemists, consists essentially of 
three parts, (i) an objective, (2) an eyepiece or ocular and (3) a 
device for properly illuminating the object. The manner in which 
these three essential components are mechanically mounted, 
and their relative importance with respect to each other will de¬ 
pend upon the nature of the investigation to which the instru¬ 
ment is to be specifically applied. The mechanical parts of the 
microscope can therefore be best discussed under the different 
types of microscopes applied to special investigations.^ 
The optical components, however, need a few words in order 
that the student may refresh his memory relative to the optics 
involved. 
Objectives have as their function the formation of an enlarged 
real image of the object placed upon the stage of the microscope. 
From the viewpoint of the chemist, their construction should be 
such as to keep them as far above the object as possible, yet 
yield an image of as great an area of the object as can be ob¬ 
tained without distortion and without color bands or fringes. 
In addition, they should possess considerable depth of focus. 
Objectives are commonly designated by their equivalent focal 
length, as, for example, i inch, 32 millimeters, etc., the numbers 
indicating that the objective will produce a real image of approxi¬ 
mately the same size as that produced by a simple convex lens 
1 For the nomenclature of the different parts of the compound microscope see 
frontispiece. 
1 
