PREFACE. 



UN arriving at the conclusion of their labours, the Authors feel that some 

 apology is, in the first place, due to the Subscribers, for the extent to which 

 the number of their pages has been increased beyond the original estimate. 

 They have, however, the pleasure of stating that no complaints have been 

 addressed to them on this head, but, on the contrary, strong injunctions, when 

 the work was somewhat advanced, to allow no considerations of arbitrary limits 

 to prevent equal justice being done to the subjects falling under the later 

 letters of the alphabet. They feel therefore that due allowance has been 

 made for the difficulty of calculating beforehand the extent of a work like the 

 present, and that the circumstance which has chiefly led to the enlargement of 

 the volume, namely, the revision of the articles at the latest moment before 

 committing them to press, has been duly taken into account. 



Secondly, a few observations may be offered on the character, objects and 

 uses of the work. It was stated in the Prospectus, that the ' Micrographic 

 Dictionary ' was offered as an index to our knowledge of the structure and 

 properties of bodies revealed by the Microscope. The Authors venture to 

 hope that their work may possess many useful qualities beyond those strictly 

 implied in the above definition. 



Few or none of the works hitherto published have dwelt upon the 

 manner in which observers might judge of the structure of objects from the 

 appearances presented under the microscope. There are works treating of the 

 construction of the mechanical and optical parts of the instrument, and the 

 manner of using them ; of the methods of preparing objects for examination ; 

 and to these are usually appended lists of objects presenting interesting appear- 

 ances. But there exists no work which will direct the Student how to vary the 

 methods of preparation of the objects examined, so as to elicit their true 

 structure. 



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