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 



