66 A. E. Verrill—The Bermuda Islands; Geology. 
12. Surface Hardening and Infiltration by Sea Water and Spray. 
Wherever the limestones have been exposed for some time to the 
joint or alternate action of salt spray and the atmosphere, their sur- 
faces becomes hard and deeply corroded, pitted, or rudely honey- 
combed, with the intervening portions rising up into sharp ridges, 
rough and ragged points, and other strange, rude, and irregular 
forms, so that they are very unpleasant to walk upon or climb over, 
for they are very destructive to shoes and clothing. (PI. xxii.) 
This is due partly to the solvent action of the sea water, eating 
out the pits, and partly to the infiltration and hardening of the inter- 
vening spaces by the evaporation of the calcareous water. As the 
intermediate ridges and points become higher they seem to act by 
capillary action, like wicks, to draw up the water from the pits and 
crevices, and the stalactitic material is deposited at their points and 
edges, building them up and making them very hard. (See figs. 8, 
15, 22.) This action is going on everywhere along the cliffs. When 
the surface of the rocks becomes thus hardened, they are very resist- 
ant to erosion by the waves, and thus even limestones that are soft 
beneath the surface may endure for a long period. 
Below high tide the action is somewhat different, for here the 
sharper projections are worn off, but the infiltration and hardening 
of the rock goes on to low-water mark, especially wherever it is 
alternately wet and partly dry. In such places the rocks usually 
become rudely pitted, partly by solution and partly by the mechani- 
cal erosion of the softer spots, but the pits are generally larger than 
above sea-level, and often form shallow tidal pools, large and small. 
Owing partly to this hardening of the rocks, nearly or quite to low- 
water mark, but not much lower down, and partly to the diminished 
force of the waves on the rocks while submerged, these hardened 
limestones often form nearly flat platforms or benches, at or just 
above low-water mark. Sometimes this is aided by the horizontal 
stratification of the rocks, by corals and other growths, and by other 
causes. But the infiltration of these partly exposed rocks, convert- 
ing soft limestones into those that will ring under the blow of a 
hammer, has a great effect in preventing their rapid destruction by 
the waves. 
13. Compact Limestones; Building Stones. 
In its downward course all the percolating waters must eventually - 
be stopped, by the layer of sea-water which everywhere fills the 
porous beds of limestone to near the level of mean-tide and some- 
