It was amusing, and after a little I could see the joke and laugh myself. The Tigris was on my right, and by-and-by the two began to prattle down over a hard bottom from higher ground. Only for a little way, though, for here we came to another wide swamp which the two traversed under low sprouts of swamp maple and birch, the ground having been cut over within a few years.
And right here I ran into a full chorus, a raucous cacophony, an Homeric din that sounded as if all the rough-voiced goblins between Blue Hill and the Berkshires were assembled in convention up stream and had just heard the story, particularly well told. I knew them. They were the wood frogs, holding their annual convention, indeed, in the water all along the marshy margin of the swamp. Once a year they come down, as people go to the seashore, disporting themselves in the waves and making very merry about it. They were not laughing at me. They were simply shouting their happiness at being thawed out and finding it springtime once more.
Their voices, pitched about an octave below middle C, and all on one note, sound not unlike a great flock of ducks gabbling wildly, but they are really more nearly musical than that. After the convention is over they go back to the woods, where you will find them sitting among the leaves, though you will never see them till they see you. And when you do see them they are in the air. They have surprisingly long legs and can jump tremendously, turning in the air as they go, so that, having landed, their next leap will take them in a new direction. The earth seems to swallow them as they touch it, for their coloration is that of the brown leaves, and they leap from one invisibility to the next.
Beyond the frog chorus I found my stream again, dancing daintily along hemlock shaded shallows and rippling over slate ledges in the latticed shade of oak and maple twigs, and here another voice called me, a staccato whistle with a suspicion of a trill in it now and then, the voice of the very spirit of the spring woodland,—the hyla. I have called it a whistle, yet it is hardly that; it is rather the soft rich tone of a pipe, such as Pan might have imitated when he first blew into the hollow reed on the brook margin.
He is a shy fellow, this inch-long brown frog that swells his throat till it is like a balloon and pipes forth this mellow note, and he is even more invisible than the wood-frog. You may seek him diligently for years and not find him, for his voice is that of a ventriloquist and he seems to send it hither and thither. It is as if this were a trick of some frisky Ariel of the wood that danced about and whistled, now before and now behind you. When the trill comes in it you may well think the tricksy spirit is laughing at you so that his voice shakes. It would be no surprise if some trilling note ended in a giggle and Ariel himself should float by you on the mocking air.
The great chorus of spring peepers is to come later; now, but an occasional one has waked from his frosty nest beneath the woodland leaves and come down to the water margin to sing. Nor do I know whether it was the ventriloquial call of one that sounded now ahead and now behind, now above and now below, or whether relays of jovial invisible sprites passed me on from pool to pool. What I do know is that, a mile or more beyond its outlet under the ooze of the little bog, I found the source of my Euphrates in springs that boil clear through the sand and send forth the cool, pure water for the delectation of all who will come to drink.
Here upon the margin I heard another chorus that repaid me for all the rough laughter of the wood-goblin frogs,—the plaintive melodies of a little flock of vesper sparrows, newly arrived and very happy about it. These come later than the song sparrows, and bring a quality of wistfulness in their song which in this differs from the bluff heartiness of the earlier bird. It is as if their joy in the strong sun and the awakening of creation was tempered and softened to a touch of tears at some gentle remembrance. The vesper sparrows recall the vanished happiness of past summers in their greeting to that which comes.
After that my way led me home through the purpling woodland toward the golden greeting of the sunset. I had tasted to the full the joy of exploration and discovery. I doubt if Humboldt felt any better coming back from his exploration of the sources of the Caspian. My Euphrates I know; my Tigris I have reserved for future, perhaps even greater joy of tracing to its source in the mystic depths of, to me, untrodden woodland.