50 A, FE. Verrill—The Bermuda Islands; Geology. 
Such valleys may have since been partly filled up by the red-clay 
soils and calcareous sands washed down from the hillsides. When 
occupied by swamps, they are filled with thick accumulations of peat 
and muck, said to be 45 feet deep in some of the larger ones. 
Many of the smaller and more abrupt valleys, both those on the 
dry land and those now beneath the sea, have certainly been made 
by the falling in of the roofs of more or less extensive caverns, aided 
Figure 4.—Diagrammatic section of seolian limestone, as seen in Hamilton, show- 
ing irregular sand-drift structure ; s, pocket of loose sand. 
by the subsequent erosion of the shores. Probably some even of the 
larger sounds and harbors, like Castle Harbor, Harrington Sound, 
etc., have had a similar origin, at least in part. This will be dis- 
cussed more fully in the chapters on subsidence and erosion, These 
enclosed sunken areas or small valleys are like the “sinks” often 
found in the cavernous limestone regions of the United States and 
Europe, but they are unusually frequent in Bermuda, so that they 
Figure 5.—Diagrammatic section of zolian limestone at Mt. Langton, showing 
very diversely stratified sand-drift structure. Both this and fig. 4 slightly 
altered and reduced from Rice. 
become a notable feature. Those that are above the level of the 
sea usually contain rich soil and are locally called “banana holes,” 
because bananas and other tender plants grow best in them, owing 
to the shelter from the winds and the richness of the soil. 
Many of the sinks on the land extend below sea-level and then 
form small pools or larger ponds, often quite deep and filled with 
sea water, which may rise and fall with the tide. Some of those 
situated near the shore contain a variety of marine fishes, ete., 
