of America. 

Those of our readers who have read the previous books of this series
will have good cause to remember George Benton, Charley ("Sandy")
Green, Tommy Gregory and Will Smith.  The adventures of these lads
among the Pictured Rocks of Old Superior, among the wreckers and
reptiles of the Florida Everglades, in the caverns of the Great
Continental Divide, and among the snows of the Hudson Bay wilderness
have been recorded under appropriate titles in previous works. 

The four boys were members of the Beaver Patrol, Chicago.  Will Smith
was Scoutmaster, while George Benton was Patrol Leader.  They wore
upon the sleeves of their coats medals showing that they had passed
the examination as Ambulance Aids, Stalkers, Pioneers and Seamen. 

Instructed by Mr.  Horton, a well-known criminal lawyer of Chicago, the
boys had reached the almost deserted mine at dusk of a November day.
There they had found Canfield, the caretaker, waiting for them in a
dimly-lighted office.  The mine had not been operated for a number of
months, not because the veins had given out, but because of some