Tapping into history’s depths

Like other kettle lakes, idyllic Walden Pond in Concord is sensitive to pollution. Like other kettle lakes, idyllic Walden Pond in Concord is sensitive to pollution. (Aram Boghosian for The Boston Globe/File 2008)
By Michael Kenney
Globe Correspondent / August 4, 2009

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As huge, mile-thick glaciers advanced and then retreated across New England over a period of thousands of years, they left behind the makings of such idyllic, summery places as Walden Pond, Fresh Pond, and Jamaica Pond.

To geologists, they are known as kettle lakes, from their basic, but sometimes skewed, cooking-kettle shape. Early New Englanders chose to call them by the Old English ponde rather than the French lac.

Robert M. Thorson’s account mixes hands-on geology, boyhood reminiscence, and a good dash of Thoreau. As his title, “Beyond Walden,’’ suggests, his account carries the kettle lakes westward across their northern United States range.

The key difference between kettle lakes and “normal’’ lakes, as Thorson puts it, is that “unlike normal lakes, which usually have significant inlet or outlet streams, kettle lakes are natural wells tapping the groundwater table.’’

And in addition to being sensitive to pollution - and to development, commercial and recreational - they are “individually quirky.’’

Thorson, a geologist at the University of Connecticut, has previously explored New England’s stone walls. Growing up in North Dakota and Minnesota, at the western extent of the kettle lake region, his family summered at Union Lake in northern Minnesota.

Kettle lakes, he recalls, “were ideal for young families. The waves were non-threatening, the shorelines were sandy, a surface layer of warm water developed fairly quickly, and there were neither sharks nor jellyfish for mothers to fret about.’’

But observing Union Lake “as the summers rolled by,’’ Thorson saw “a shift from a leaner and cleaner lake to a murkier [one]’’ with rising counts of fecal bacteria and levels of toxins such as DDT. “At the time,’’ he writes, “I didn’t make the connection between changes within the water and the rising number of cottages on the shore.’’

One of Thorson’s first excursions after arriving at UConn was to Walden Pond where similar changes were occurring but where “because of its international fame, [its] degradation . . . has been unusually well documented.’’

It began in Thoreau’s time, he writes, under the impact of summer visitors and, more recently, with the building of a town dump which “will probably leak forever.’’ And even now under state protection, its fish “remain inedible’’ and “the input of tainted dust from the nearby urban population and urine from its many swimmers remain threats.’’

Thoreau was attracted to Walden not only by its natural environment, but also by the presence of a nearby settlement of former Concord slaves and their descendants, as Elise Lemire writes in “Black Walden: Slavery and Its Aftermath in Concord, Massachusetts’’ (University of Pennsylvania Press, 2009).

Lemire, who grew up in Lincoln and took swimming lessons at Walden, now teaches literature at Purchase College of the State University of New York.

“For Thoreau,’’ Lemire writes, “it was the marks left on the landscape by the former slaves and other outcasts as much as the plants and animals that made these areas so interesting,’’ devoting a chapter in “Walden’’ to their community which he describes as “a small village.’’

A key figure was Brister Freeman, a former slave of a prominent landowner, who in 1792 acquired an acre on the road across from Walden Pond. He was eager, Lemire writes, “to be a landowner’’ as that was “the only way former slaves would be fully able to divest themselves of their former identities as someone else’s property.’’

The community sustained itself for close to 100 years with a variety of cottage crafts including spinning, weaving baskets and chair bottoms, and living on the beans and peas that would thrive in the sandy soil that typically surrounds kettle lakes.

The community gradually died off, and the last piece of black-owned property was sold in 1873.

Michael Kenney is a Cambridge-based freelance writer.

BEYOND WALDEN: The Hidden History of America’s Kettle Lakes and Ponds By Robert M. Thorson

Walker, 308 pp., illustrated, $26

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