species, M. alcicornis and M. ramosa, is extremely
abundant at Bermudas, where it acts in every way
the part of a coral, forming massive additions to tho
reef of carbonate of lime abstracted from the sea.
Beneath these large things there is usually a close
felting of an undergrowth, consisting partly of sponges
and smaller zoophytes, but chiefly of what are sometimes
called lithophytes, sea-weeds of such genera as
Corallina, Melohesia,o.Vid NuUipora, which like corals
take carbonate of lime from tbe sea-water and incorporate
it with their tissues.
All these things living and dying are constantly
yielding a fine powder of lime, which sinks down and
compacts in the spaces among tbeir roots, and every
breaker of the eternal surf grinds down more material
and packs it into every hollow and crevice
capable of receiving and retaining it. A great order
of Avorms including the genus serpula secrete carbonate
of lime and form thick and large calcareous
tubes, or make galleries through tbe partially consolidated
calcareous mud and harden it and bind it
together. So great a part do these Avorms play in the
construction of the reefs at Bermudas that General
Nelson, in an admirable paper on tbe Geology of
tbe Island, published by him in the Transactions
of tbe Geological Society in the year 1834, calls
some small circular reefs found everyAvhere round
the sliores in tbe wash of the breakers, and Avbicb
appear to be due to tbeir agency alone, ‘ Serpuline
reefs.’
As I have already said, tbe Bermudas Islands, in
common Avitb most otber coral islands, are formed by
tbe raising of tbe weather edge of tbe reef above the
le v e l of tb e sea. T b is a p p e a r s to lie a c c om p lish e d ,
in tb e fir s t p la c e , b y th e a g e n c y o f tb e Avaves a lo n e .
L r a gm e n t s , m a n y o f tb em w ith th e in h e r e n t poAver
o f in c r e a s in g tb em s e lv e s a n d c em e n t in g tb em s e h - e s
t o g e th e r tlir o u g h t lie g r ow th o f th e l iv in g th in g s
Avhich in v e s t th em , a r e p ile d u]) o n o n e a n o tlie r
u n t i l t li e y r e a c h t lie h ig h e s t p o in t a c c e s s ib le to th e
s ea in s to rm s .
T h e m om e n t th e r id g e a p p e a r s a h o v e Avater a h e a c li
o f c o r a l- s a iid is fo rm e d a g a in s t it. T h e to p o f tb e
b e a ch d r ie s a t low w a te r , a n d th e s a n d is b low n on ,
fir s t am o n g th e c r e v ic e s o f th e breakAvater a lr e a d y
fo rm ed , Avhich i t w id e n s a n d s t r e n g th e n s , a n d th e n
o v e r th e b r e a k w a te r to th e le d g e s a n d r e e fs b e y o n d ;
Avliich i t t e n d s to r a is e to th e su r fa c e . In th i s Avay in
a ll c o r a l s e a s is la n d s lia v e a t e n d e n c y to fo rm a lo n g
th e w in d w a r d e d g e s o f a n n u la r r e e fs. T h e Avind-
Avard is la n d t h e n fo rm s a s h e lt e r to th e le ew a r d
p o r t io n o f th e r in g , d e p r iv in g i t o f th e m a in s o u r c e
o f i t s e le v a t io n , th e p il in g u p o f f r a gm e n t s b y th e
AvaA'es, so th a t o n th e le ew a r d s id e w e u s u a lly h a v e
m o r e or le s s o f th e r e e f r em a in in g su bm e r g e d , a n d
a n y p a s s a g e s o f c om m u n ic a t io n b e tw e e n tb e c e n t r a l
la g o o n a n d tb e o u t e r sea .
I have little to add to tbe excellent account of the
geology of Bermudas given by General Nelson. Tbe
Bermudas of tbe present day is simply a bank of
hloAvn sand in various stages of consolidation. The
depth of Avater increases round the island Avith extreme
rapidity. Seven miles to the north there is a
sounding of 1,375 fathoms, and about two miles
further off one of 1,775 fathoms. To tbe north-east
tlie r e is Avater of 1,500 fa th om s a t a distance o f t e n
X