POPULAR SCIENCE REVIEW. 
136 
sing and which, artists love to represent. Varying in their 1 
origin according to the nature of the rock they lay open for 
our inspection, and indicating the history and progress of the 
changes they have undergone before arriving at their present 
state, they have a special interest for the geologist ; and it is 
astonishing how completely geological points regulate also their 
value and interest to the naturalist, the artist, and the mere 
seeker after adventure and picturesque scenery. 
First let us consider the case of caverns in those noble old 
granites and porphyries, those gneissic rocks, those slates, 
and those basaltic and volcanic regions where the battle is ever 
going on between the dash of the wave and the tough fibre of 
a hard rock. It is a battle that can end only in one way, for, 
unlike all human contests, in which both sides suffer, the water, 
however often beaten back, always comes again to the charge 
unweakened by the effort — it always finds at last the weak 
point in the enemy’s armour — each time it succeeds in removing 
a few grains or fragments, it enlists these as recruits to bring 
away more — and thus it advances steadily if stealthily — surely 
if slowly — “ here a little and there a little,” until very often it is 
enabled to act on a larger scale and assume a more important 
attitude of offence. 
Look at the “ iron-bound ” shores of the Atlantic on the 
European side. Take any part of this extended line where the 
granite is firmest and the porphyry toughest. How do we 
find these rocks? Many of the hardest are islands, already 
detached from the main land, many others are headlands and 
promontories. Between them and amongst them are lovely 
little bays with sandy and rocky beaches. The cliffs exposed 
are hoary enough to look at, and covered with lichens. But 
what mean the angular blocks of stone on the beach ? Whence 
came those vast fallen masses almost like islands, at the foot of 
the cliff? The question is easily answered. They have fallen 
from above. The cliff has been undermined, the ruin and 
destruction of the whole mass long ago commenced, and there 
is no longer any question but that of the time that wi 1 1 be 
required to complete the work. 
The study of a single island, or even part of an island, is very 
instructive, and the account of a single group of caverns will 
be more satisfactory than a long description of varied dis- 
turbance. 
There is in the English Channel a wonderful little island, 
three miles long-, and a mile and a half across at the widest 
part, entirely surrounded by steep cliffs, some 250 or 300 feet 
high, the whole of which, without exception, are composed of 
granitic and porphyritic rock. One would say, looking at the 
walls of rock surrounding it, that the waves, angry and 
