16 
ALASKA GLACIERS 
reached the three-eighth-mile limit is roughly measured 
by the age of a half-grown forest. 
GLACIER BAY 
The next depression west of Lynn Canal is broader, 
as well as more complex in the details of its config¬ 
uration, and its general trend is northwestward in¬ 
stead of northward. On the west it is separated from 
the Gulf of Alaska by the Fairweather Range, the 
dominant mountain mass of this region. Glacier Bay, 
occupying its main axis, sends many branches into 
the troughs among its hills and mountains, and would 
be still more complicated in outline but for the clog¬ 
ging of the valleys by glaciers. Six of its inlets head 
against ice walls, from which bergs are constantly 
falling. 
The glaciers of this basin are better known to the phys¬ 
ical geographer than any others of the Alaska belt, and 
one of their number, the Muir, enjoys the same preemi¬ 
nence in popular acquaintance and appreciation. The 
group was explored, sketched, and studied by Muir in 
1879 and 1880. Wright made a visit in 1886, producing 
a rough map and working out the main elements of the 
later glacial history. Reid, in 1890 and 1892, executed 
a careful survey of the shores, the lower portions of the 
tidal glaciers, and a broad inland tract including the 
greater part of Muir Glacier; developed much further 
the history of recent changes; and instituted a number 
of investigations bearing on the physics of glaciers. 
Minor studies were made by Cushing (1890) and Rus¬ 
sell (1890), the map work has been extended by the 
Canadian Boundary Commission, and a fine series of 
photographs were made by the Commission in the sum¬ 
mer of 1894. 
