PREFACE. 



THE Author's object in presenting this work to the student 

 of microscopy is to supply at a reasonable cost a book 

 written upon somewhat similar lines to Quekett's ' Prac- 

 tical Treatise on the Use of the Microscope,' the second 

 and last edition of which appeared in 1852. The necessity 

 of a treatise bringing the science to the present day has 

 been long felt, and it is hoped that a vacant place in micro- 

 scopical literature is now filled up. 



Although essentially a practical work upon microscopy, 

 the reader is treated to a little theory, in the hope that it 

 may lead to a more minute study of the optical principles 

 upon which the microscope is constructed. Some may 

 object, perhaps, to so little theory being introduced, espe- 

 cially on those subjects intimately connected with Professor 

 Abbe's recent researches ; but it should be remembered that 

 the addition of such matter would have added considerably 

 to the cost of production and detracted somewhat from the 

 practical character of the book : this, taken together with 

 the fact that ample references have been given to Professor 

 Abbe's papers, will, it is hoped, be sufficient apology. 

 Moreover, the information lately put forth is novel to the 



general body of microscopists ; the views now held are so 



a 2 



