INTRODUCTORY. 



The knowledge which this volume attempts to 

 convey in the proper use of the microscope, may 

 be gleaned by following several methods. 



First. By reading carefully all contents from 

 first to last. This is strongly recommended, as an 

 effort has been made to make the contents progres- 

 sive and it is hoped that in this manner a general 

 knowledge of terms and optical principles involved 

 will be acquired, which will greatly aid in intelli- 

 gently and with greater facility and pleasure 

 carrying out the instructions in the chapter " How 

 to Work." 



Second. By reading the general principles and 

 studying the various terms and omitting some of the 

 instructive processes, as " How to Judge Chromatic 

 and Spherical Aberration," " How to Measure 

 Angle," " How to Measure Working Distance," 

 etc., which may be carried out after some famili- 

 arity with manipulation of the instrument has been 

 acquired. 



Third. By studying the parts of the stand and 

 then referring to chapter " How to Work." This 

 is not in any case advised, but may be done when 



