THE PARALLEL ROADS OF GLEN 
ROY, IN SCOTLAND. 
HERE are phenomena in nature which 
I give the clew to so many of its mysteries, 
that their correct interpretation leads at once 
to broad generalizations and to the rapid ad¬ 
vance of science in new directions. The ex¬ 
planation of one very local and limited problem 
may clear up many collateral ones, when its 
solution includes the answer to a whole set 
of kindred inquires. The “ parallel roads ” of 
Glen Roy offer such a problem. For half a 
century they have been the subject of patient 
investigation and the boldest speculation. To 
them natural philosophers have returned again 
and again to test their theories, and until they 
are fully understood no steady or permanent 
advance can be made in the various views 
which they have suggested to different observ¬ 
ers. The theory of the formation of lakes by 
