He realized the vital necessity for checking the Doraine in her flight before she accomplished the miracle of passing unhindered through the channel and out into the open sea beyond.

The swiftness of the current indicated plainly enough that this natural canal was of no great length.
The ship slid on between the tree lined banks.

The trees were of the temperate zone, with spreading limbs, thick foliage and hardy trunks.
There were no palms visible, but in the rarely occurring open spaces a large shrub abounded.

This was instantly recognized by Percival, who proclaimed it to be the algaroba, a plant commonly found on the Gran Chaco in Argentina.

While the woodland was thick there was nothing about it to suggest the tropical jungle with its impenetrable fastnesses.
The keel of the half-sunken Doraine was scraping ominously on the bed of the channel.