INTRODUCTION 



[INTRO. 



rs 



ciples of microscopical technique. The present text-book [his "Prin- 

 ciples of Microscopy''] has no message to those who are content to 

 follow a system of rule of thumb, and to eke this out by blind trial 

 and error. It addresses itself to those who 

 are dissatisfied with the results thus obtained 

 and who desire to master the scientific prin- 

 ciples of microscopy, even at the price of 

 some intellectual effort." 



From the observation of ten generations 

 of students and their subsequent career I am 

 confirmed in the belief that for attainment 

 in study with the microscope, as in all other 

 human endeavor, a person must pay for all 

 he gets. 



(3) In considering the microscope, it may 

 be looked at as a machine composed of glass 

 and brass complete in itself, or it may be 

 considered as an artificial aid to the eye, 

 like a spectacle. When complete in itself 

 it is properly called a projection microscope, 



OBJECTIVE 



r-.f 



Object 



MIRROR 



FIG. 3. A COMPOUND MICROSCOPE HELPING 

 THE EYE TO FORM A RETINAL IMAGE OF A NEAR 

 OBJECT. 



Mirror The plane and concave mirror to re- 

 flect light through the object. 



Object The small object to be seen by the eye. 



Objective The objective of the compound micro- 

 scope to form a real image of the small object. 



Axis The principal optic axis of the micro- 

 scope. 



/ Principal focus of the ocular and of the ob- 

 jective. 



r im The real image formed by the objective. 



Ocular The double convex lens enabling the 

 eye to see the real image formed by the objective. 



cr The cornea of the eye. 



rs The refracting surface of the schematic eye. 



L The crystalline lens of the eye. 



r i The retinal image; it is erect with reference 

 to the object, but inverted as compared with the 

 real image. 



