116 B. WILLIS—DRIFT PHENOMENA OF PUGET SOUND. 
lower, forming inlets and valleys. Their typical relation is that of the 
stem and arms of a Y or of one inverted, X. They branch both north- 
ward and southward, the branches connect, and they thus enclose a 
number of “meucllan ly polygonal areas, whose relations suggest a curious 
mosaic. The deepest axes of the hollows are delineated on plate 6, which 
also expresses by interrogation points the existing doubt as to some of the 
connections across land areas. 
Variations of depth.—The depths of the hollows are peculiarly distrib- 
uted. Specific figures taken from the United States Coast Survey chart 
are given in plate 7, and gradations of depth for each 50 fathoms (91.4 
meters) are indicated in plate 6 by the character of the line which fol- 
lows the channel. All depths are referred to sealevel, which is a datum 
not genetically related to the topographic form. The true depth of the 
hollows should be measured from the plateau level, and therefore from- 
400 to 500 feet (120 to 150 meters) or, say, 75 fathoms (187 meters) may be 
- added to the figures on plate 7. 
Admiralty inlet is relatively shallow at its northern end; opposite 
Admiralty head the depth of water is but 46 fathoms (84 meters), and 
the bottom is rocky. Shoal water extends thence northwest into the 
strait of Fuca, it being 12 miles (20 kilometers) to the 50 fathom (91.4 
meters) contour. Toward the southeast the channel deepens rapidly. 
Five miles (8 kilometers) from Admiralty head the sounding is 104 
fathoms (190 meters); about midway of the length of the inlet north of — 
Seattle occurs the maximum depth of 153 fathoms (280 meters), and 
thence almost to Tacoma the figures are not less than 95 fathoms (143 
meters). From Admiralty head south to Tacoma the bottom is described 
as coarse sand, fine sand,and mud. ‘These facts indicate that along the 
line of this hollow for 60 miles (96 kilometers) the hard rock bottom 
slopes southward. For half the distance the descent is 600 feet (183 
meters), carrying the bottom on mud down to 900 feet (274 meters) below 
tide. Ifthe slope continues at the same rate, bed rock at Tacoma is not 
less than 1,500 feet (457 meters) below sealevel. 
Profiles of Admiralty inlet and Hood canal.—A cross-section of Admiralty 
inlet is given in figure 1. The locality selected is one exhibiting the 
VASHON ISLAND ADMIRALTY INLET DES MOINES ISLAND 
Figure 1.—Section across Admiralty inlet just South of Point Pully. 
average relations of width and depth. The section extends from the 
Des Moines island on the east to Vashon island. on the west, a distance 
