THE COMPOUND MICROSCOPE. 



As has been stated a magnified image is observed 

 in the Compound Microscope. Any two lenses, 

 one of short, the other of long focus, placed suffi- 

 ciently far apart, will attain this object and this 

 was for years the method of its construction. 



In any microscope, whether .simple or com- 

 pound, the difficulty of holding- it or the object 

 steady during observation, increases with the 

 increase in magnifying power and in the com- 

 pound form with only a moderately high power, 

 it is utterly impossible to retain sufficient steadi- 

 ness to make any reliable observation. Mechanical 

 contrivances therefore became a necessity and 

 were applied in the very earliest constructions of 

 the microscope. Even when such a luxury as an 

 achromatic lens was unknown they were all made 

 to fulfill the following conditions : 



A platform for holding the object. 



A means of adjustment for properly focusing on 

 the object. 



Provisions for suitably illuminating the object. 



From what may be called a crude attainment of 

 of these three purposes, the construction gradually 

 became more complex. Many additions have 



