viii PKEFACE TO THE SEVENTH EDITION 



mounting of objects, and a review of the whole Animal, Vegetable, 

 and Inorganic Kingdoms specially suited for microscopic purposes, 

 must be essentially a cyclopaedic work. This was far more possible 

 to one man when Dr. Carpenter began his work than it was even 

 when he issued his last edition. But it is practically impossible 

 now. It is with Microscopy as with every department of scientific 

 work we must depend upon the specialist for accurate knowledge. 



In the following pages I have been most generously aided. In 

 no department, not even that in which for twenty years I have 

 been specially at work, have I acted without the cordial interest, 

 suggestion, and enlightenment afforded by kindred or similar workers. 

 In every section experts have given me their unstinted help. 

 To preserve the character of the book, however, and give it homo- 

 geneity, it was essential that all should pass through one mind and 

 be so presented. My work for many years has familiarised me, 

 more or less, with every department of Microscopy, and with the 

 great majority of branches to which it is applied. I have therefore 

 given a common form, for which I take the sole responsibility, 

 to the entire treatise. The subject might have been carried over 

 ten such volumes as this ; but we were of necessity limited as 

 to space, and the specific aim has been to give such a condensed 

 view of the whole range of subjects as would make this treatise 

 at once a practical and a suggestive one. 



The first five chapters of the last edition are represented in this 

 edition by seven chapters ; the whole matter of these seven chapters 

 has been re- written, and two of them are on subjects not treated in 

 any former edition. These seven chapters represent the experience 

 of a lifetime, confirmed and aided by the advice and practical help 

 of some of the most experienced men in the world, and they may be 

 read by any one familiar with the use of algebraic symbols and the 

 practice of the rule of three. They are not in any sense abstruse, 

 and they are everywhere practical. 



In the second chapter, on The Principles and Theory of Vision 

 with the Compound Microscope, so much has been done during the 

 past twenty years by Dr. ABBE, of Jena, that my first desire was to 

 induce him to summarise, for this treatise, the results of his twenty 

 years of unremitting and marvellously productive labour. But the 

 state of his health and his many obligations forbade this ; and at 

 length it became apparent that if this most desirable end were to 

 be secured, I must re-study with this object all the monographs of 

 this author. I summarised them, not without anxiety ; but that was 

 speedily removed, for Dr. ABBE, with great generosity, consented to 

 examine my results, and has been good enough to write that he has 

 * read [my] clear expositions with the greatest interest ; ' and, after 



