PE V EFACE. 



THIS translation of Ncnegeli and Schwendener's well-known treatise 

 " Das Mikroskop " was commenced by Mr. Frank Crisp, Secretary of 

 the Eoyal Microscopical Society, immediately after the publication 

 of the last (G-erman) edition (1877), with the intention as indi- 

 cated by him in a communication to the Quekett Microscopical 

 Club of filling up a blank in English microscopical literature 

 in regard to the scientific technical treatment of the theory of the 

 Microscope, in which English text-books were so deficient. 



The student refers in vain, even at the present date, to English 

 works on the Microscope for explanations of the theory of the 

 construction of objectives, eyepieces,*&c., or for the discussion of 

 the phenomena of diffraction and polarisation in their connexion 

 with the Microscope, or for any scientific treatment of the question 

 of interpreting microscopical images or the theory of microscopic 

 observation. These subjects are dealt with systematically in 

 German works only, and notably in that of Naegeli and Schwen- 

 dener. 



The translation was thus undertaken with a view to placing 

 before English readers the then best known collective exposition 

 or technical treatment of these points by German writers. 



When the rough draft of the translation was completed, the first 

 five sheets (80 pp.) were revised and put in type, but in conse- 

 quence of prior claims upon his time in connexion with the Koyal 

 Microscopical Society, Mr. Crisp was compelled to relinquish the 

 task of further revision and of passing the volume through the 

 press, a labour which was undertaken by Mr. John Mayall, jun., 

 one of the editors of the Society's Journal. 



Just as the printing was completed a fire destroyed the premises 

 of the printers, and the whole of the printed sheets of the volume 



