ere they
might be beyond the reach of falling ruins; but suddenly the quay sank
down with all the people on it, and not one of the dead bodies ever
floated to the surface. A great number of boats and small vessels
anchored near it, all full of people, were swallowed up, as in a
whirlpool.[682] No fragments of these wrecks ever rose again to the
surface, and the water in the place where the quay had stood is stated,
in many accounts, to be unfathomable; but Whitehurst says he ascertained
it to be one hundred fathoms.[683]

Circumstantial as are the contemporary narratives, I learn from a
correspondent, Mr. F. Freeman, in 1841, that no part of the Tagus was
then more than thirty feet deep at high tide, and an examination of the
position of the new quay, and the memorials preserved of the time and
manner in which it was built, rendered the statement of so great a
subsidence in 1755 quite unintelligible. Perhaps a deep narrow chasm,
such as was before described in Calabria (p. 481), opened and closed
again in the bed of the Tagus, after swallowing up some incumbent
buildings and vessels. We have already seen that such openings may
collapse after the shock suddenly, or, in places where the strata are of
soft and yielding materials, very gradually. According to the
observations made at Lisbon, in 1837, by Mr. Sharpe, the destroying
effects of this earthquake were confined to the tertiary strata, and
were most violent on the blue clay, on which the lower part of the city
is constructed. Not a building, he says, on the secondary limestone or
the basalt was injured.[684]

_Shocks felt at sea._--The shock was felt at sea, on the deck of a ship
to the west of Lisbon, and produced very much the same sensation as on
dry land. Off St. Lucar, the captain of the ship Nancy felt his vessel
so violently shaken, that he thought she had struck the ground; but, on
heaving the lead, found a great depth of water. Captain Clark, from
Denia, in latitude 36 degrees 24 minutes N., between nine and ten in the
morning, had his ship shaken and strained as if she had struck upon a
rock, so that the seams of the deck opened, and the compass was
overturned in the binnacle. Another ship, forty leagues west of St.
Vincent, experienced so violent a concussion, that the men were thrown a
foot and a half perpendicularly up from the deck.

_Rate at which the movement travelled._--The agitation of lakes, rivers,
and springs, in Great Britain, was remarkabl