IN THE SHETLANDS 49 
almost fills, and up which the boat can no longer 
proceed. Yet far beyond, where all is opaque dark- 
ness, one still hears the muffled wash and sob of the 
waves as they ceaselessly eat and eat into the hidden 
bowels of the rock. As the whole force and vastness 
of the ocean lies beyond this little tip of its tongue, 
to where may not such burrows extend? and might 
not, by a knowledge of their position and the direc- 
tion in which they run, some inland towns be supplied 
with the blessing of sea-water ? 
The water in these caverns is delightfully clear, 
revealing in every detail, through its lucid green, 
the smooth-rolled pebbles and great white rounded 
boulders which strew, or rather make, their floor. 
To look down at them is like looking up into the 
arched roof of some other cave. One might think 
it the reflection of the one overhead, till, glancing up, 
the difference is remarked—jagged, bright-hued peaks 
and niches instead of smooth, even whiteness. This 
effect, as of a roof beneath one, is due, I think, to 
the continuation downwards of the sides of the cavern, 
for this gives the same vaulted appearance, but re- 
versed, that there is overhead, and the mind, as with 
the image on the retina of the eye, soon sets it the 
right way up. 
These caves must have been known from time 
immemorial to as many as were accustomed to coast 
round the island, and it is interesting to think of 
who, and what kind of craft may, from age to age, 
have visited or sheltered in them. Recently, how- 
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