Is not the midnight like Central Africa to most of us? Are we not tempted to explore it--to penetrate to the shores of its lake Tchad, and discover the sources of the Nile, perchance the Mountains of the Moon? Who knows what fertility and beauty, moral and natural, are there to be found? In the Mountains of the Moon, in the Central Africa of the night, there is where all Niles have their hidden heads. It was to discover these Mountains of the Moon, these mysterious sources of the Nile, forever so far away and yet forever so near, that Thoreau went to Nature. He went not to gather and to classify facts; he went to satisfy his soul. Burroughs is inclined to wonder and even laugh because of the many times he speaks of hearing the voice of unknown birds. To Burroughs the forest contained no unknown birds; to Thoreau the forest was valuable only because it _did_ contain unknown birds. His straining for hidden melodies, his striving for deeper meanings, his dreaming of Mountains of the Moon that might become visible at any moment just beyond the horizon--it is in these things that he differs from all other nature writers. He was not a reporter; he was a prophet. "My profession is always to be on the alert, to find God in nature, to know His lurking places, to attend all the oratorios, the operas in nature. Shall I not have words as fresh as my thought? Shall I use any other man's word?" To him Nature was of value only as it furnished message for humanity. "A fact," he declared, "must be the vehicle of some humanity in order to interest us." He went to Nature for tonic, not for fact; he sought only truth and freedom and spontaneousness of soul. He had no desire to write a botany, or an ornithology; rather would he learn of Nature the fundamentals of human living. "I went into the woods because I wished to live deliberately, to front only the essential facts of life, and see if I could not learn what it had to teach, and not, when I came to die, discover that I had not lived." Burroughs went into the woods to know and to make others to know, Thoreau went in to think and to feel; Burroughs was a naturalist, Thoreau a _super_naturalist.