OF THE MICROSCOPE. 23 



tinctly seen, and consequently all microscopes, except the 

 simplest forms of hand magnifiers, are provided with means 

 for throwing the light upon the object, and for regulating the 

 amount which shall either fall upon it or pass through it. 



Hence the importance of providing efficient means for ad- 

 justing the focus and holding and illuminating the object, and 

 the purpose which the stand is intended to fulfil, is to furnish 

 these means in a compact and convenient form. Every micro- 

 scope, therefore, of a grade above a hand magnifier, whether 

 it be simple or compound, must possess : 



1. Suitable means for supporting the object, and placing and 

 maintaining it in proper position. 



2. Means for illuminating the object, either by throwing the 

 light upon it when it is opaque, or transmitting the light 

 through it when it is transparent. 



3. Means for transmitting to the eye an enlarged image of the 

 object. 



The different parts which are employed for securing these 

 several ends, have been constructed of an almost endless va- 

 riety of forms, according to the fancies of the different makers 

 and the requirements of different microscopists. As it is im- 

 portant that the student should familiarize himself with the 

 names of these different parts, we give a definition of them, 

 and in order that there may be no opportunity for mistake or 

 misapprehension, we have also engraved an outline of one of 

 the ordinary forms of the microscope, and on this we have 

 marked the names of the different parts. 



NAMES OF THE DIFFERENT PARTS. 



The following are the names of the essential parts of a com- 

 pound microscope of ordinary construction. The names of the 

 different parts of the simple microscope are the same as those 

 of the compound microscope, but the latter has several parts 

 which do not exist in the former. 



The Stand is the name properly applied to the entire frame 

 used for supporting and illuminating the object, and for carry- 

 ing and adjusting the optical part, the latter consisting of the 



