A. EL, Verrill—The Bermuda Islands; Geology. 65 
Pulpit Rock (fig. 22) and the North Rocks (figs. 23, 31) probably 
owe their existence mainly to their resistance due to infiltration, 
while the softer surrounding rocks were washed away. The same is 
doubtless true, in a marked degree, of all the other boldly sculp- 
tured rocks and projecting crags, such as Lion Rock (fig. 20), and the 
cliffs shown in figs. 17, 22. 
11. Unconsolidated Sands; no consolidation below low-tide level. 
Why the masses of shell-sand, mentioned above, remain unconsoli- 
dated, imbedded in or between hardened strata of the same composi- 
tion, has never been satisfactorily explained. The only suggestion 
that seems to me plausible, is that they were so situated that they 
were continually soaked in waters that were already saturated with 
calcium carbonate and from. which no evaporation could take place, 
owing to the nearly impervious or hard rocks above and below them. 
Under such conditions they might have become water-bearing strata 
without alteration, either by solution or hardening. This would 
also explain the remarkably perfect preservation of delicate land 
shells, even with their colors perfect, in these beds. 
I have already mentioned that there is no evidence that these 
shell-sands and marls, at Bermuda, ever become consolidated into 
lime when constantly covered by the sea, somewhat below low-tide 
level. In the excavations made at Ireland Island and elsewhere, 6 
to 10 feet of such unconsolidated materials have been found, over- 
lying eolian limestones. Stakes and probes can be driven down 
many feet into these sands almost everywhere in the harbors. 
The same conditions are found allover the world where shell-sands 
and coral-sands form the bottom deposits. Also, in the deep sea 
where Globigerina-ooze occurs of great depth, it is never consoli- 
dated. Probably this is also due to the absence of evaporation. 
Perhaps violent agitation, in shallow water seas, may take the place 
of evaporation, to some extent, and cause some consolidation, just 
below low tide, by loss of carbonie acid. 
But many geologists constantly refer to such shell-limestones and 
coral-limestones as if consolidated below sea-level. I do not know 
of any evidence that it ever occurs under ordinary conditions. <A 
marked or rapid change in temperature, or contact with water of a 
different chemical composition, or the action of living organisms, 
might cause it, under unusual conditions. 
