It was in the early forenoon of the next day that we made the great departure.  Since dawn Professor Challenger had been acutely uneasy, continually scanning each bank of the river.  Suddenly he gave an exclamation of satisfaction and pointed to a single tree, which projected at a peculiar angle over the side of the stream.

“What do you make of that?” he asked.

“It is surely an Assai palm,” said Summerlee.

“Exactly.  It was an Assai palm which I took for my landmark.  The secret opening is half a mile onwards upon the other side of the river.  There is no break in the trees.  That is the wonder and the mystery of it.  There where you see light-green rushes instead of dark-green undergrowth, there between the great cotton woods, that is my private gate into the unknown.  Push through, and you will understand.”

It was indeed a wonderful place.  Having reached the spot marked by a line of light-green rushes, we poled out two canoes through them for some hundreds of yards, and eventually emerged into a placid and shallow stream, running clear and transparent over a sandy bottom.  It may have been twenty yards across, and was banked in on each side by most luxuriant vegetation.  No one who had not observed that for a short distance reeds had taken the place of shrubs, could possibly have guessed the existence of such a stream or dreamed of the fairyland beyond.

For a fairyland it was—­the most wonderful that the imagination of man could conceive.  The thick vegetation met overhead, interlacing into a natural pergola, and through this tunnel of verdure in a golden twilight flowed the green, pellucid river, beautiful in itself, but marvelous from the strange tints thrown by the vivid light from above filtered and tempered in its fall.  Clear as crystal, motionless as a sheet of glass, green as the edge of an iceberg, it stretched in front of us under its leafy archway, every stroke of our paddles sending a thousand ripples across its shining surface.  It was a fitting avenue to a land of wonders.  All sign of the Indians had passed away, but animal life was more frequent, and the tameness of the creatures showed that they knew nothing of the hunter.  Fuzzy little black-velvet monkeys, with snow-white teeth and gleaming, mocking eyes, chattered at us as we passed.  With a dull, heavy splash an occasional cayman plunged in from the bank.  Once a dark, clumsy tapir stared at us from a gap in the bushes, and then lumbered away through the forest; once, too, the yellow, sinuous form of a great puma whisked amid the brushwood, and its green, baleful eyes glared hatred at us over its tawny shoulder.  Bird life was abundant, especially the wading birds, stork, heron, and ibis gathering in little groups, blue, scarlet, and white, upon every log which jutted from the bank, while beneath us the crystal water was alive with fish of every shape and color.

For three days we made our way up this tunnel of hazy green sunshine.  On the longer stretches one could hardly tell as one looked ahead where the distant green water ended and the distant green archway began.  The deep peace of this strange waterway was unbroken by any sign of man.