482 A, FE. Verrill—The Bermuda Islands. 
X.—Western Blue Cut, apparently partly roofed over by the 
reef, leading to Sink III. 
XI.—North Rocks Northeastern Cut, leading toward a small sink 
11 fathoms deep, not numbered (North Rocks Sink). 
XII. and XIII.—Ledge Flat Cuts, 7-9 fathoms deep, connected 
together inside the outer reefs. 
XIV.—Mills Breaker Cut, 8-10 fathoms deep, leading towards an 
irregular sink (not shaded) 9 to 14 fathoms deep, and about 
2 miles long. 
XV.—Main Ship-channel or the Narrows, a narrow, deep cut lead- 
ing to Murray Anchorage. 
Norr.—The map is much altered from that of Agassiz by the addition of the 
three contour lines, at 10, 20, and 100 fathoms depths; by shading the deeper 
parts of the larger lagoons, where the depth exceeds 50 feet ; and in some other 
respects. It is based on the Admiralty Chart, reduced by photography. 
11.—Anchorages or submerged Lagoons ; Bottom Deposits. 
As stated on a previous page (p. 465), the area covered by the sub- 
merged reefs and lagoons is more than ten times as great as the dry 
land. It has been estimated at from 200 to 230 square miles. 
But of this whole amount a very considerable part consists of sub- 
> or anchorages, nearly free of reefs over 
merged lagoons, ‘sounds,’ 
large areas, or often equal in area to Castle Harbor and Harrington 
Sound. 
The more important of these are represented by the ruled areas 
(I to VI) on the map (fig. 26). One of the largest and best known is 
Murray Anchorage (I), just within the narrows. This is large enough 
for a large fleet of war vessels, and the bottom, in 7 to 9 fathoms, is 
of tenacious white mud. 
The same white shell-mud and shell-sand are found over the bot- 
toms of all these enclosed lagoons, at depths of 4 to 14 fathoms. 
In the deeper parts the mud prevails and often becomes very fine 
and tenacious. It is called chalky mud by the sailors, or simply 
“chalk.” 'To the eye it appears to be almost entirely composed of a 
fine powder, but when washed through seives a considerable amount 
of shell-sand can almost always be separated, together with many 
small living mollusks, foraminifera, etc., but it is rather barren of 
life. 
We dredged up large quantities of such mud at many localities in 
Great Sound, Bailey Bay, Murray Anchorage, Castle Harbor, and 
Harrington Sound. In all these places its nature was similar, only 
