PKEFACE TO THE SIXTH EDITION. 



N issuing the SIXTH Edition of this Work on 

 the MICROSCOPE, we may state that it has 

 been thoroughly revised and for the most part 

 re-written. Eight carefully and beautifully 

 executed Plates are added, which were drawn 

 by Tuffen West from natural objects, engraved 

 and printed by Edmund Evans in the first style of colour- 

 printing. 



The Author cannot but express his grateful surprise at 

 the extraordinarily popular reception which his t>ook has 

 met with : a sale of fifty thousand is an unprecedented 

 event for a work of the kind. This circumstance is 

 extremely gratifying to him, because it affords reasonable 

 grounds for believing that his work has been useful, and 

 encourages renewed effort to make the volume still more 

 acceptable. It has been his endeavour to bring the 

 information contained in its pages up to the most recent 

 discoveries ; although, in a daily progressing field of 

 science, it is almost impossible to keep pace with the 

 advance of knowledge in all its ramifications. 



The passing remarks the Author has seen occasion to 

 make upon the various objects that have fallen under his 

 notice are intended to serve, as would a finger-post or 



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