246 HOW TO SEE WITH THE MICROSCOPE. 



favor work with centrally disposed light make a note 

 ol this. 



Says one (alluding to the second proposition), I don't 

 exactly see that thing as you do. Suppose, for instance, 

 that the objective and the eye were both so perfect as 

 to allow the illumination to become axial, as in your 

 first illustration, wouldn't that be better still? 



We reply, ask the artist if he would prefer the land- 

 scape thus lighted. The architect of the universe ex- 

 pressly arranged things to prevent such a catastrophe. 

 A certain amount of shade is as necessary as that of 

 light. Such a thing as " dead central illumination," 

 although often talked about, is a myth. 



Feeling deeply the importance of calling the atten- 

 tion of the reader to an element which we regard as of 

 vital importance, we have accordingly done so at the 

 risk of being somewhat tedious. 



POSITION OF OBSERVER. 



Our experience is, that in sixty cases out of the hun- 

 dred, having made some preliminary examination of an 

 object under study, and thus demonstrating the neces- 

 sity of the use of higher amplifications, that with the 

 latter comes also the necessity of a long and protracted 

 sitting ; in fact a downright seige is inaugurated. It is 

 better in all such cases to postpone work until evening, 

 or at least so to arrange that the observer shall have 

 perfect immunity trom interruptions of any nature; 

 and at the commencement of such work it is of para- 

 mount importance that the operator adopt such a posi- 



