The hole in the bottom of Walden Pond (Walden 129)

Thoreau's map of his soundings of Walden Pond. Wikimedia Commons

Thoreau’s map of his soundings of Walden Pond. Wikimedia Commons

There is something deeply strange about Walden Pond. “The pond rises and falls,” Thoreau wrote, “but whether regularly or not, and within what period, nobody knows, though, as usual, many pretend to know.”

What’s weird is that the water level doesn’t seem to vary with local rainfall. It rises and falls for no apparent reason. Henry said “I can remember when it was a foot or two lower, and also when it was at least five feet higher, than when I lived by it.”

The Concord Magazine reprinted a fascinating 1971 article by Eugene Walker, a geologist and local resident. Walker writes, “Tales are told around town of the hole in the bottom of and the stream that comes through it, connected perhaps to a river that is rumored to run underground from somewhere in the White Mountains, perhaps Lake Winnipesaukee, southward to Cape Cod.”

But the truth, Walker explains, is that the pond’s water level varies exactly with the water table in the sand and gravel that surrounds the lake. In other words the lake bed is apparently porous:

“Walden occupies what the geologists call a glacial kettle. About 10-11 thousand years ago a very large block of ice lay melting there, a short distance south of the main body of the shrinking glacier. Torrents of meltwater from the ice to the north spread sheets of sand and gravel around the isolated block for many years before the currents turned elsewhere. Finally, the block of ice melted and left a pool of water surrounded by banks of sand and gravel.”

So there you have it. Mystery solved, and by the sort of careful measurement and scientific approach that Henry favored. But Walker laments,

“Mystery exerts an attraction that people often regret losing — one remembers how the poet Keats complained that a rainbow never meant as much to him after he heard someone explain how it was formed by raindrops bending light rays. Walden can never have for us the magical quality it possessed for those who dreamed that it had no bottom and extended indefinitely down into cold darkness.”

Would Henry have felt that way? Walker concludes:

“For such lost magic and for dreams of water-bearing tunnels from the White Mountains we have to substitute the satisfaction of knowing that Walden rises and falls, as if breathing, in perfect harmony with the surroundings that supply its water.”

Thoreau certainly understood the lure of nature’s mysteries, but I think he’d have strongly disagreed with Keats, and I think he’d have felt that Walker’s final sentence was too weak — admirable in its appreciation of natural harmony, but failing to acknowledge the “magic of reality” (to borrow the title of a children’s book by biologist Richard Dawkins). As Henry got older his interest in science grew deeper and deeper. He was working on an ambitious study of seed dispersal when he was felled by tuberculosis at age forty-four. Rather than subtracting from Henry’s sense of awe and wonder, his growing scientific knowledge seemed to fuel it.

Henry had as much appreciation for the old legends as anyone (and he tells a few in his book), but I think he’d have been thrilled by our current knowledge of ice ages and glaciers and formation of lakes and the mysteries of aquifers — mysteries that nineteenth century geologists were just beginning to unravel. The little legends that once attached themselves to Walden Pond have been replaced by a much grander, deeper, and more complex story… which in turn raises new mysteries, and which has the additional advantage of being true.

(About  “A Year in Walden”)

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