upon
which they landed was quite low, and bordered with mangroves, of which
fact they took advantage by concealing themselves among the trees, and
from that secure hiding-place examining the harbour at leisure.

They found that they were on the north-eastern extremity of the island
of Baru, with the whole of the harbour of Cartagena before them, the
roofs and spires of the town just showing waveringly, in a sort of
mirage, over the low land which forms the easternmost extremity of the
island of Tierra Bomba. It is this same island of Tierra Bomba, by the
way, which converts what would otherwise be an open roadstead into a
landlocked harbour, for it forms the western side of the harbour, and
serves as a natural breakwater, sheltering the roadstead very
effectually when the wind happens to blow from the westward. Also,
being roughly triangular in shape, its eastern and western sides each
measuring about four miles long, and its northern side about three
miles, it divides the entire harbour into two parts, namely, the upper
and the lower bay. The upper bay in its turn is divided into the inner
and the outer harbour by two irregularly shaped spits of low land, the
western spit jutting out south and east in a sort of elbow from the
promontory on which the city is built, while the eastern spit is divided
from the mainland by a narrow channel, and is called Manzanillo Island.

The foregoing is a brief and rough description of Cartagena harbour,
given for the information of the reader and to enable him the better to
understand what follows; but comparatively few of the above details were
apparent to the two Englishmen lurking among the mangroves on the
north-eastern extremity of Baru, for the island of Tierra Bomba, the
most prominent object in sight, shut out much of the upper bay. They
obtained, however, a good view of the Boca Chica, or harbour entrance,
and took careful note of the fact that it was effectually commanded, at
its narrowest and most difficult point, by a battery built on the very
beach itself, and a fort, or castle, crowning the crest of a hill
immediately above. They both agreed that if this was the only entrance
to the harbour, and if the garrisons of those forts maintained a proper
lookout, it should be quite impossible for a ship to enter or leave
Cartagena harbour, except with the full permission of the authorities.

"Well," exclaimed Marshall at last, when they had both familiarised
themselves wit