THE COMPOUND MICROSCOPE. 



As was previously stated a magnified image is 

 observed in the Compound Microscope. Any two 

 lenses, one of short, the other of long focus, placed 

 sufficiently far apart, will attain this object, and this 

 was for years the method of its construction. 



On any microscope, whether simple or compound, 

 the difficulty of holding it or the object steady during 

 observation increases with the increase in magnifying 

 power, and in the compound form with only a mod- 

 erately high power, it is utterly impossible to retain 

 sufficient steadiness to make any reliable observation. 

 Mechanical contrivances thesefore became a neces- 

 sity, and were applied in the earliest constructions of 

 the microscope. They were all made to fulfill the fol- 

 lowing three conditions : A platform for holding the 

 object ; a means of adjustment for properly focusing 

 on the object, and a mode of suitably illuminating the 

 same. 



From what may now be called a crude attainment of 

 these three purposes, the construction gradually 

 became more complex. Many additions have been 

 made which have proven useful and have remained, 

 while others have been discarded, and these have led 

 to the present construction of the microscope. 



