recovers its
transparency at the distance of sixty miles from the coast, this
depression must be gradually shoaling, especially as during the
monsoons, the sea loaded with mud and sand, is beaten back in that
direction towards the delta. Now, if a ship or human body sink to the
bottom in such a spot, it is by no means improbable that it may become
buried under a depth of a thousand feet of sediment in the same number
of years.

Even on that part of the floor of the ocean to which no accession of
drift matter is carried (a part which probably constitutes, at any given
period, by far the larger proportion of the whole submarine area), there
are circumstances accompanying a wreck which favor the conservation of
skeletons. For when the vessel fills suddenly with water, especially in
the night, many persons are drowned between decks and in their cabins,
so that their bodies are prevented from rising again to the surface. The
vessel often strikes upon an uneven bottom, and is overturned; in which
case the ballast, consisting of sand, shingle, and rock, or the cargo,
frequently composed of heavy and durable materials, may be thrown down
upon the carcasses. In the case of ships of war, cannon, shot, and other
warlike stores, may press down with their weight the timbers of the
vessel as they decay, and beneath these and the metallic substances the
bones of man may be preserved.

_Number of wrecked vessels._--When we reflect on the number of curious
monuments consigned to the bed of the ocean in the course of every naval
war from the earliest times, our conceptions are greatly raised
respecting the multiplicity of lasting memorials which man is leaving of
his labors. During our last great struggle with France, thirty-two of
our ships of the line went to the bottom in the space of twenty-two
years, besides seven 50-gun ships, eighty-six frigates, and a multitude
of smaller vessels. The navies of the other European powers, France,
Holland, Spain, and Denmark, were almost annihilated during the same
period, so that the aggregate of their losses must have many times
exceeded that of Great Britain. In every one of these ships were
batteries of cannon constructed of iron or brass, whereof a great number
had the dates and places of their manufacture inscribed upon them in
letters cast in metal. In each there were coins of copper, silver, and
often many of gold, capable of serving as valuable historical monuments;
in each were an infin