202 O'N THE THEOEY OF THE MICROSCOPE. 



unlaboured English, though strikingly characteristic of German 

 habit of thought, and of the genius of the German language, — a 

 style, namely, which throws an atmosphere of minute qualification 

 around every positive statement ; and which, though expressive 

 of thoroughness and conscientiousness, has to the unlearned the 

 effect sometimes of obscuring rather than clearing the view. To 

 use a German proverb, ** One cannot see the wood for the trees !" 

 Unfortunately, however, translation loses point in proportion as 

 it fails to render back the many-sided aspect of the original. 



Having read Dr. Abbe's essay with that pleasure which 

 attends the acquisition of new ideas, (vainly sought for in English 

 works on the microscope) I feel a natural desire to introduce the 

 author's views to an English public, so far as a plain and, I trust, 

 faithful translation may afford the means of introduction; and 

 shall be amply repaid for any trouble incurred in executing my 

 self-imposed task if the researches here recorded should prove as 

 instructive and acceptable to others as to myself. 



That no one may be deterred from reading these pages by the 

 supposed abstract nature of the subject, or its technical treatment, 

 I may here state that the mathematical demonstrations on which 

 Dr. Abbe builds his theory, and the detail of experimental method 

 pursued by him in the practical portion of this enquiry, are not 

 communicated in the present article, which is simply a general 

 statement of results. A more detailed account is promised in an 

 article to be published in the Jena Journal of Natural Sciences. 



H. E. FRIPP. 



Section I. — The construction of the Microscope on a theoretical 

 basis. 

 I. In our handbooks of micrography occasion is sometimes 

 taken to allude to the fact that the construction of the microscope, 

 and its progressive improvement, have been almost exclusively 

 matters of empirical practice, — that is to say, of skilful and 

 persevering trials prosecuted by experienced, practical men. ]^ow 

 and then, perhaps, the question may be asked, "Why is it that 



