There could be little doubt, however, that the stone was aimed at us, so the incident surely pointed to humanity—and malevolent humanity—upon the plateau.
We withdrew hurriedly from the chasm, our minds full of this new development and its bearing upon our plans.
The situation was difficult enough before, but if the obstructions of Nature were increased by the deliberate opposition of man, then our case was indeed a hopeless one.
And yet, as we looked up at that beautiful fringe of verdure only a few hundreds of feet above our heads, there was not one of us who could conceive the idea of returning to London until we had explored it to its depths.
On discussing the situation, we determined that our best course was to continue to coast round the plateau in the hope of finding some other means of reaching the top.
The line of cliffs, which had decreased considerably in height, had already begun to trend from west to north, and if we could take this as representing the arc of a circle, the whole circumference could not be very great.
At the worst, then, we should be back in a few days at our starting-point.
We made a march that day which totaled some two-and-twenty miles, without any change in our prospects.
I may mention that our aneroid shows us that in the continual incline which we have ascended since we abandoned our canoes we have risen to no less than three thousand feet above sea-level.
Hence there is a considerable change both in the temperature and in the vegetation.
We have shaken off some of that horrible insect life which is the bane of tropical travel.
A few palms still survive, and many tree-ferns, but the Amazonian trees have been all left behind.
It was pleasant to see the convolvulus, the passion-flower, and the begonia, all reminding me of home, here among these inhospitable rocks.
There was a red begonia just the same color as one that is kept in a pot in the window of a certain villa in Streatham—but I am drifting into private reminiscence.
That night—I am still speaking of the first day of our circumnavigation of the plateau—a great experience awaited us, and one which for ever set at rest any doubt which we could have had as to the wonders so near us.
You will realize as you read it, my dear Mr. McArdle, and possibly for the first time that the paper has not sent me on a wild-goose chase, and that there is inconceivably fine copy waiting for the world whenever we have the Professor's leave to make use of it.
I shall not dare to publish these articles unless I can bring back my proofs to England, or I shall be hailed as the journalistic Munchausen of all time.
I have no doubt that you feel the same way yourself, and that you would not care to stake the whole credit of the Gazette upon this adventure until we can meet the chorus of criticism and scepticism which such articles must of necessity elicit.
So this wonderful incident, which would make such a headline for the old paper, must still wait its turn in the editorial drawer.
And yet it was all over in a flash, and there was no sequel to it, save in our own convictions.
What occurred was this.
Lord John had shot an ajouti—which is a small, pig-like animal—and, half of it having been given to the Indians, we were cooking the other half upon our fire.
There is a chill in the air after dark, and we had all drawn close to the blaze.
The night was moonless, but there were some stars, and one could see for a little distance across the plain.
Well, suddenly out of the darkness, out of the night, there swooped something with a swish like an aeroplane.
The whole group of us were covered for an instant by a canopy of leathery wings, and I had a momentary vision of a long, snake-like neck, a fierce, red, greedy eye, and a great snapping beak, filled, to my amazement, with little, gleaming teeth.
The next instant it was gone—and so was our dinner.
A huge black shadow, twenty feet across, skimmed up into the air; for an instant the monster wings blotted out the stars, and then it vanished over the brow of the cliff above us.
We all sat in amazed silence round the fire, like the heroes of Virgil when the Harpies came down upon them.
It was Summerlee who was the first to speak.
"Professor Challenger," said he, in a solemn voice, which quavered with emotion, "I owe you an apology.
Sir, I am very much in the wrong, and I beg that you will forget what is past."
It was handsomely said, and the two men for the first time shook hands.
So much we have gained by this clear vision of our first pterodactyl.
It was worth a stolen supper to bring two such men together.
But if prehistoric life existed upon the plateau it was not superabundant, for we had no further glimpse of it during the next three days.
During this time we traversed a barren and forbidding country, which alternated between stony desert and desolate marshes full of many wild-fowl, upon the north and east of the cliffs.
From that direction the place is really inaccessible, and, were it not for a hardish ledge which runs at the very base of the precipice, we should have had to turn back.
Many times we were up to our waists in the slime and blubber of an old, semi-tropical swamp.
To make matters worse, the place seemed to be a favorite breeding-place of the Jaracaca snake, the most venomous and aggressive in South America.
Again and again these horrible creatures came writhing and springing towards us across the surface of this putrid bog, and it was only by keeping our shot-guns for ever ready that we could feel safe from them.
One funnel-shaped depression in the morass, of a livid green in color from some lichen which festered in it, will always remain as a nightmare memory in my mind.
It seems to have been a special nest of these vermins, and the slopes were alive with them, all writhing in our direction, for it is a peculiarity of the Jaracaca that he will always attack man at first sight.
There were too many for us to shoot, so we fairly took to our heels and ran until we were exhausted.
I shall always remember as we looked back how far behind we could see the heads and necks of our horrible pursuers rising and falling amid the reeds.
Jaracaca Swamp we named it in the map which we are constructing.
The cliffs upon the farther side had lost their ruddy tint, being chocolate-brown in color; the vegetation was more scattered along the top of them, and they had sunk to three or four hundred feet in height, but in no place did we find any point where they could be ascended.
If anything, they were more impossible than at the first point where we had met them.
Their absolute steepness is indicated in the photograph which I took over the stony desert.
"Surely," said I, as we discussed the situation, "the rain must find its way down somehow.