EDITOR'S PREFACE. 



The scope and purpose of this work are sufficiently 

 stated in the authors' preface. The need of such a work 

 has often been felt in directing the work of advanced 

 students especially, and it is with the hope of aiding them 

 that it has been undertaken to place the contents of this 

 work within their easy reach. Because of numerous 

 mistakes in the references in the original, all of those 

 which refer to Plates in the atlas have been verified or 

 corrected, and also as many of those which refer to the 

 literature as were accessible. A few references to original 

 articles in English have been inserted. 



