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PREFACE. 



ON 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 these 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 ( Micro- 

 graphic 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 appearances. 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. 



An Introduction has been prefixed to the ' Dictionary/ affording in- 

 struction for the selection of a Microscope and the accessory apparatus, 

 explaining the manner of using these, and particularly the precautions 

 requisite with the less perfect but more economical foreign glasses ; and, 

 lastly, entering minutely into what may be called microscopical manipu- 

 lation and the special education of the eye. 



Many valuable contributions to our knowledge of the structure or 

 functions of microscopic organisms are probably lost through the inability 

 of microscopic observers to ascertain readily the name and position in 

 Nature of objects which fall under their notice. It is hoped that the very 



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