378 WILLIAM HERBERT HOBBS 
To the well-developed jointing found in the rocks of the Glacier 
National Park must be ascribed the well-marked checkerboard 
pattern displayed by the park valleys, a pattern which strikes one 
at once when the topographic map is examined. A number of 
observations of the bearings of master-joints which were made by 
a 
*e (Cirque 
¥\ 
Cirque Y C 
Irque 
“ 
Ge 
Cirque 
GrooveD UPLAND EARLY FRETTED UPLAND 
(Youth) (Adolescence) 
Bighorn Range Welsh Highland 
Cirque 
(mature) 
Cirque & a 
(mature) 
Horn 
FRETTED UPLAND MoNUMENTED UPLAND 
(Maturity) (Old Age) 
Alps Glacier National Park 
Fic. 10o.—Stages of sculpture by mountain glaciers 
the writer indicated a rather general correspondence between them 
and the trends of the valleys in which they were found. In some 
instances the lower spurs which have been less extensively sapped 
by glacial erosion indicate very clearly the dominating influence 
of the joint planes in shaping them. ‘The cirques themselves also 
display this tendency by their approach to rectangular outlines. 
