96 THE POPULAR SCIENCE MONTHLY. 



the telescope is absolutely essential ; and, in biology, vast depai't- 

 ments can be brought witliin our reach only by the aid of the micro- 

 scope. This latter instrument, especially, has a wide range of appli- 

 cation. The investigations of the anatomist and physiologist cannot 

 go on without it ; the educated physician has it in daily use ; the 

 tradesman finds it an important aid in testing the purity of commodi- 

 ties ; and the student in many departments of physical science is 

 obliged to use it in his work. When to all these considerations we 

 add that the manipulation of the microscope, for the purpose of ordi- 

 nary observation, may be acquired without much difficulty, and that 

 the instrument itself may be procured at a moderate cost, we have 

 said enough to justify the assertion that every educated person ought 

 to possess a microscope, even as he possesses a collection of books. 



Fig. 1. Complete Instrument. 



To derive advantage from the use of the microscope, it is not ne- 

 cessary that one should master all the technicalities of the instrument, 

 or be possessed of all the improved appliances for extremely minute 

 observations. Professional microscopists have recognized the error 

 of directing all one's efforts on such tasks as the resolution of test- 

 plates, so long as really urgent work remains undone. Thus, the 

 President of the " Quekett Microscopical Society" remarked: 



" Our opticians have gone ahead of the observers, they have placed in our 

 hands powerful means of research. I fear the account of the talent committed 

 to our charge will not be one of which we may be proud. I fear we are too 

 apt to pride ourselves as being the possessors of superior instruments; each man 

 pits his instrument in rivalry against his neighbor's, and rejoices that he can 

 beat him in the resolution of Robert's test-plate." 



