Fesruary 18, 1904] 
NATORE 
37t 
knowledge and of the meaning of personal identity, 
which must always most strenuously exercise our 
highest faculties. If there has been any marked 
shifting of ground, it has been towards the region of 
personal experience, a return to the principle of cogito, 
ergo sum, a principle of more metaphysical treasure | 
than Descartes himself discovered. The living and 
dynamic nature of the self has come to stand out in | 
more striking relief. The self-realisation of Hegel 
and the will of Schopenhauer, ideas so typical of the 
resolute individual character of western ethics, will 
illustrate one of the many lines along which Kant’s 
impulse has acted. In nothing is he more emphatic 
than in urging the necessity of a critical inquiry into 
the foundations of knowledge before attempting to deal 
with the opposing dogmatisms of physics and meta- 
physics, and it is just the validity of his own Kritik 
which has made the later times so productive of re- 
constructions. The parts in our vast system of know- 
ledge have at the same time become more and more 
related to an organic whole. More and more has the 
analogy of the living organism, with its parts in the 
whole and its whole in the parts, become descriptive 
of the body corporate of thought, and it may perhaps 
be said that it enters into our conceptions of the whole 
of being. Perhaps the full result of this idea in its 
religious aspect has not yet been realised. Certainly 
the living purpose of the abstract physical law has not 
yet been successfully formulated either by trans- 
cendentalist or materialist. ALFRED EARL. 
THE FORMATION OF CORAL REEFS. 
ORAL reefs are divided into three classes, fring- 
ing, barrier and atoll. A fringing reef forms a 
terrace at the low tide level, extending out from the 
coast of any land, while a barrier reef is a rampart at 
the same level, lying parallel to the coast, from which 
it is separated by a deep channel. An atoll is a ring- 
brings up a cup. Probably sedentary life is far from 
scarce, as the fine coral mud, so deleterious to coral 
life, appears to be swept further out. 
agoons vary greatly in accordance with their size 
and depth. A fairly open one has its bottom above 
the 25 fathom line either bare or covered with coarse 
sand, but deeper a fine mud may be found. Commonly 
the depth of any deep lagoon bears some proportion 
to the depths of the passages into it. Shoals occur 
anywhere in it, reaching the surface and forming 
broad flats. From the lagoon floor they arise abruptly, 
as does also the encircling reef (Fig. 3), a gradual 
slope to 20 fathoms or less covered with decaying 
coral masses, and then a perpendicular cliff to the 
surface. 
The examination of the surface of the encircling 
reef shows it to have been formed by corals, bound 
together by other organisms. These corals form a 
definite class not extending below 25 fathoms in any 
luxuriance. They feed mainly—and many entirely— 
by their commensal algz, so that they, as also the 
nullipores, are dependent for their growth on light and 
constant change of the water. They are profoundly 
affected by any deposition of mud, and for this reason 
upgrowing shoals are rare in lagoons except near 
passages. The enormous amount of mud formed is 
shown by its sinking as a deposit around atolls. The 
muddy water that streams out of the lagoons in stormy 
weather shows where it originates; but little can come 
| from the surface of the reef, which is stationary in 
height, and still less from the reef platform, covered 
as it is by the bodies of living organisms. It is the 
result of the action of the boring and sand-feeding 
animals of the lagoons breaking up the coral skeletons 
and grinding them into the finest mud, much of which 
passes into suspension in the water. The corals on 
any low part of the encircling reef over which the 
lagoon water may pour are killed by this mud, leaving 
bare areas for the entrance of boring organisms, with 
| the result that a new passage may be cut through the 
shaped reef surrounding the lagoon, a basin varying | 
up to 50 fathoms in depth; it is thus in no way con- 
nected with any land other than may form upon it. 
A typical atoll has a flat encircling reef, generally 
with a series of islands upon it and a number of 
channels leading into its lagoon. Where land exists, 
the reef may be a mile or more broad, but commonly 
averages about 500 yards. Its surface is a flat of 
coral limestone almost completely bare of sedentary 
life. Towards the ocean its edge appears as if the 
waves were cutting a series of canals into it, but this | 
appearance is really due to buttresses being built out 
from the rock behind by the reef organisms. Beyond 
this edge the bottom is extremely rough, but passes 
gradually into a more even slope. This area, the reef 
platform, may have hollows and pockets filled with 
débris, but its prevailing characteristic is its almost | 
complete covering of corals, nullipores, Foraminifera, 
Polyzoa, and other sedentary organisms. At about 
250 yards from the edge of the reef, where its depth 
is about 40 fathoms, it passes somewhat abruptly into 
a steep at a slope often exceeding 50°. This continues 
to about 140 fathoms, after which the slope, becoming | 
quite moderate, passes gradually into the contour of | 
the surrounding sea. The steep has never been 
properly investigated, but swabs bring up loose dead | 
masses of such organisms as cover the reef platform 
above. Their presence is due to the undercurrents re- 
sulting from the sea striking on the atoll, which sweep 
down the reef platform, giving a talus slope (Fig. 3). 
Again, we have little knowledge of the lower slope 
down to 500 fathoms, where deep-sea life probably 
dominates. Shoals at such depths are densely covered 
with corals, but off atolls the lead only occasionally 
NO. 1790, VOL. 69] 
rim into the lagoon. That solution is also of great 
importance in the lagoons seems certain, for the mud 
at the bottom of such a lagoon as Suvadiva contains 
more than 2 per cent. of silica, whereas the sand of 
the reef has less than 0.04 per cent. 
At 40 fathoms different genera of corals, not depen- 
dent on commensal alge, dominate, and at the edge 
of the reef platform are the builders, their mortar 
consisting mainly of the encrusting Polytrema. They 
range from the surface, where they are almost choked 
out by others to 50 fathoms or more, and probably 
form an important connecting link between the sur- 
face builders and the true deep-sea corals, which in 
the tropics are seldom found above this latter depth. 
Their rate of growth, and also that of the surface 
forms, is enormous. Indeed, it would be moderate 
to estimate that a shoal at 25 fathoms would be built 
up to the surface in 1000 years, and that one at 50 
fathoms would scarcely tale more than twice as long. 
Recent work has shown that all coral reefs can 
scarcely be explained on one method of formation. 
Four modes naturally suggest themselves.’ (1) (Fig. 
1) On any elevation on the bottom of the ocean seden- 
tary animals naturally congregate. Their remains 
build up its summit to an extent out of all proportion 
to the upgrowth of the surrounding area, so that it 
ultimately approaches the surface. The deep-sea 
corals in warm latitudes give place to their inter- 
mediate depth allies, and these again to the reef 
builders, so that our peak is ultimately crowned with 
a surface reef. It will be readily understood from the 
1 A fuller consideration of some of the views here put forward will be 
found in ‘“*The Fauna and Geography of the Maldive and Laccadive 
Archipelagoes,” pp. 12-50, 146-183, 313-346 and 376-423. 
