NOTES. 203 
complete the chain. North of Adam’s Bridge extends Palk bay, 
a shallow mud-floored almost currentless sea, and to the south the 
Gulf of Mannar stretches as a low platform, deepening fairly 
evenly to the south at about the rate of one fathom in two miles 
to twenty fathoms, after which it sinks more rapidly to great 
depths. The platform consists of sands, which in places have 
been cemented in situ into calcareous sandstones or calcretes, 
chiefly by the agency of Polyzoa and Nullipores. These masses 
of solid rock, known as 44 paars,” are sometimes accompanied by 
coral reefs in all stages of decay, from the living forms to almost 
structureless limestone. 
In places along the west coast of Ceylon spits of sand stretch 
across the platform mainly near the mouths of rivers. They result 
from the detritus brought down by rivers, and their general trend 
to the north-west may be due to the combined flow of the streams 
and the prevailing inshore currents on the Indian side, and in 
Palk bay rivers form similar spits of sand which extend to wards the 
north-east. The coasts of India and Ceylon are swept by strong 
marine currents running up and down the coast according to the 
monsoons, but owing to the longer duration of the south-west 
monsoon this produces greater effects, and ail rivers flowing into 
the gulf have a tendency to extend their deltas towards the north. 
Near the coasts the spits consist of coarse fragments, while 
further out the sands become successively of finer grain. Long- 
continued growth of these spits would result in the formation 
of a platform arching to north. The rocky 44 paars ” arrange 
themselves roughly into three groups running parallel with 
Adam’s Bridge. The first line is found at a depth of to 4^ 
fathoms, the second at 6 to 8 fathoms, and the third at 9 to 10 
fathoms. If an area of this character were raised above the sea 
level we should expect the harder 44 paars ” and limestones to exist 
as islands, between which would be areas of loose drifting sand. 
Such is exactly the structure of Adam’s Bridge. Rameswaram 
Island has an ancient coral reef along its northern border, but the 
bulk of the island, as well as the others constituting the bridge, 
are composed of calcareous sandstones, like those now forming 
in the 44 paars.” Similar sandstones are found all along the east 
coast of India from Cape Comorin to Madras, and are represented 
on the west coast by 44 the littoral concretes,” which are considered 
by Oldham to have been originally sand spits or beach deposits. 
All these contain none but recent shells exactly like those living 
in the neighbouring seas. As no rocks of undoubted Tertiary age 
are found on the adjacent coasts, it would appear that all through 
that period the district has been in a state of equilibrium. Since 
