Clifford:

 

With further reference to the question about 1878 Boston Ballparks, here's a link to a Wikipedia entry on the old Boston NL ballpark:

 

 

It indicates that the South End Grounds were referred to by several names, including Union Baseball Grounds:

 

"South End Grounds refers to any one of three baseball parks on one site in Boston, Massachusetts. They were home to the Boston club in the National Association and the National League from 1871 to 1914.

 

"...  It was located on the northeast corner of Columbus Avenue and Walpole Street, just southeast of the current Carter Playground. Accordingly, it was also known over the years as Walpole Street Grounds; two other names were Union Baseball Grounds and simply Boston Baseball Grounds."

 

Perhaps the writer of the Advertiser article preferred the old Union grounds name?

 

Regards.

 

Steve Willoughby