ON" THE THEORY OF THE MICEOSCOPE. 201 



view by Dr. Abbe's interpretation of the manner in which the 

 microscopic image is formed, and of the appearance of certain 

 details in this image, which he shews to be due to the influence 

 of the internal structural constitution of the object examined 

 upon rays of light transmitted through it. 



In this translation a few paragraphs relating to illuminating 

 apparatus, and the conditions upon which their effects depend, 

 are omitted, as being only supplementary to the principal subject, 

 and also because reference is therein made to doctrines which are 

 somewhat at variance with English opinion and practice, and 

 which require for their proper understanding further explanation 

 than is afforded by the curt mention of them in Dr. Abbe's essay. 

 To the reader who is not familiar with the teaching of the German 

 writers on the microscope, the reference made to the treatise of 

 N'ageli and Schwendener convoys no information; and this part 

 of the subject is therefore omitted in the present communication. 



"With this exception, however, the essay has been carefully 

 rendered, and the sense of each paragraph strictly conveyed. 

 It has been my aim to express the author's views as nearly as 

 possible in his own words, that his claim of originality might not 

 suffer by false or loose rendering of his meaning; and also because 

 such a claim carries with it an equal responsibility to the reader 

 as well as to the author for accuracy of translation, particularly 

 when the subject is professedly treated as one belonging to exact 

 science, and attention claimed on the special ground of novelty of 

 doctrine. If the absence of that ease and simplicity which is 

 thought essential to popular handling of a subject be matter of 

 regret, I fear that any deficiency in the original will be still more 

 felt in the translation ; for I am fully conscious that in adhering 

 to an almost verbal transcript of idiomatic expressions which have 

 no exact English equivalent, I do not lighten the labour of the 

 reader. Yet in no other way can a circumlocution still more 

 objectionable be avoided, or that significance of meaning preserved 

 which so many German expositors of science seek to convey by a 

 peculiarity of style which is scarcely compatible with fluent and 



