20 
GENERAL GEOLOGY 
dikes of various basic igneous rocks. In places it has 
picked up large fragments of the limestone that occurs in 
mass near at hand. It has contorted and twisted the bed¬ 
ding very much, and has formed contact minerals (esso- 
nite, pyroxene) in the limestone at the border. 
On the nunatak at the eastern front of Hugh Miller 
Glacier the tonalite is cut by a diorite dike which contains 
a great horse of the tonalite and is itself cut and shifted 
by a later aplite dike (fig. 4). 
FIG. 4. DIKES IN GLACIER BAY. 
The limestone is determined as Carboniferous by Pro¬ 
fessor H. S. Williams, on the evidence of a single speci¬ 
men of Lonsdalia, and the tonalite must be younger, as it 
penetrates and alters this. It resembles closely the tonalite 
of Plover Bay, Siberia, and St. Lawrence Island, de¬ 
scribed below; and on St. Lawrence Island similar lime¬ 
stones and contact deposits are also found. 
The only point where observations were made which 
added to the information contained in Reid and Cushing’s 
map 1 was at the small glacier discharging into Reid Inlet 
next west of the Hugh Miller Glacier and named by the 
party Reid Glacier. This glacier was visited by Messrs. 
Gilbert and Palache, and the rocks on either side of its 
front were studied. 
The point on the east side is made up of coarsely crys¬ 
talline white marble, which is cut by a network of igneous 
dikes (plate 11). 
1 16th Ann. Rept. U. S. Geol. Survey, part i, plate xc. 1896. 
