PREFACE TO THE SECOND EDITION 
The first edition of this report having been exhausted in a few months 
and without satisfying the demand which the importance of the subject 
created, a second was ordered by Congress in March, 1879. The authors 
were thus given an opportunity to revise their text and eliminate a few 
formal errors which had crept in by reason of their absence while the first 
edition was passing through the press. The substance of the report is 
unchanged. 
Jar We et 
Juny, 18.79. 
xI 
