CONTENTS xiii 



CHAPTER XV. 



PREPARING OPAQUE OBJECTS FOR THE MICROSCOPIC STUDY OF INTERNAL 



STRUCTURE. 



PAGE 



Fundamental principles 383 



Grinding; abrasive wheels 384 



Grade and grain of abrasive wheels 385 



Selecting wheels 386 



Speed of rotating wheels 387 



Abrasive papers 388 



Preparing specimens 389 



Etching 391 



Etching liquids 392 



APPENDIX. 



Table of melting points 395 



Periodic classification of the elements 396 



Books for reference 397 



INDEX 399 



