PREFACE TO THE THIRTEENTH EDITION. 



In the preparation of a thirteenth edition of the Compend an opportunity 

 has been furnished for the revision of many paragraphs for the addition of 

 such new material as seemed necessary for the needs of students during their 

 attendance on lectures and for reviewing the subject prior to their examina- 

 tions. That it may continue to meet the needs of the student class in the 

 future as it has in the past is the sincere wish of the author. 



ALBERT P. BRUBAKER. 



