PREFACE V 



as is necessary to recall knowledge already acquired but not 

 yet applied in practice. 



In discussing the polarizing microscope, only the barest pos- 

 sible outline of its use and application has been thought wise. 

 This chapter is intended to be largely suggestive in character 

 and to induce at least some students to extend their studies to 

 include optical crystallography and petrography. 



In the chapter dealing with grinding, polishing and etching, 

 it was found impossible to properly present the subject without 

 unduly enlarging the book and encroaching too deeply into the 

 field of microscopic metallurgy; only the most fundamental 

 methods of alloy treatment have therefore been given. 



The instruments figured (and the methods described) have all 

 been tested and tried by the author with but one or two excep- 

 tions. The instruments are those with which the Cornell Uni- 

 versity Laboratories are supplied or those which have kindly 

 been loaned by their makers. Doubtless there are other pieces 

 of apparatus and other instruments which may be as satisfactory, 

 but it has been thought best to discuss only such as have actually 

 been examined and tested experimentally by the author and his 

 students. 



For the benefit of those who may wish to obtain similar in- 

 struments the manufacturers have in most cases been indicated. 



In preparing such an outline the work of an author must of 

 necessity be largely one of compilation, of modification of old 

 methods and the presentation of old ideas from a new viewpoint. 

 The present writer, therefore, makes no claims for originality, and 

 as a student of that remarkable teacher, the late Professor Behrens 

 of the Polytechnic School of Delft, he naturally has followed and 

 favored the methods developed by this master of the art of the 

 qualitative analysis of minute quantities of material and he 

 acknowledges fully his indebtedness to his former teacher, and 

 takes this opportunity of expressing his gratitude for the advice 

 and help given him by his guide and friend. 



To Simon Henry Gage, Professor Emeritus of Histology and 

 Embryology, the writer also acknowledges his indebtedness for 

 much that is here presented. It is largely due to the spirit of 



