Thoreau, the scientist
Much more has been said and written about Thoreau’s philosopher-poet side than his naturalist side, but as a scientist I am more interested in the latter. The journals that he kept from 1837 to 1861 were so full of natural history observations that they might have become a major scientific work if he had not died of a lung ailment at age 44. He probably thought so, too. Two months before his death in 1862 he wrote a letter to a friend, saying, “if I were to live, I should have much to report on Natural History generally.”
During the winter of 1846, Thoreau drilled more than a hundred holes through the ice of Walden Pond and lowered a weighted line to produce what may be the first map of the floor of an American lake, thereby identifying Walden’s deepest point in the western basin near his cove. In August 1860, he also sent a thermometer down in a stoppered bottle to measure the layered structure of the water column, a first formal analysis of the thermal stratification of the lake. He was amazed at the temperature difference between the upper and lower layers, and he speculated on what it might mean for the resident fish. “What various temperatures, then, the fishes of this pond can enjoy,” he wrote. “They can in a few minutes sink to winter or rise to summer. How much this varied temperature must have to do with the distribution of the fishes in it.”
In August 1939, lake ecologist Ed Deevey made similar measurements from a rowboat and confirmed Thoreau’s reports. He also measured the stratification of the water in more detail, finding temperatures close to 79 degrees Fahrenheit (26 degrees Celsius) in the upper 15 feet (5 meters) that fell to 41 degrees Fahrenheit (5 degrees Celsisus) near the bottom. Writing in Quarterly Review of Biology, Deevey noted that Thoreau’s curiosity was “unusually fruitful when directed toward lakes,” and called him the first American limnologist, or lake scientist.
Other scientists have also used Thoreau’s observations in their own research. The Boston University ecologist Richard Primack has compared recent observations of ice-out dates, flowering times, and other signs of spring to the dates that Thoreau recorded in his journals. In Walden Warming, he used those data to show that climate change has shortened the ice-cover season by several weeks since the 19th century. And one journal entry from 1854 tripped up another friend of mine, biophysicist Charles McCutchen.
While standing beside a local stream in 1970, Charlie had noticed something resembling a fine thread on the surface that undulated crosswise to the current. After careful study, he identified it as an ephemeral wrinkle where the surface film folded inward on itself. Soon after he published his discovery in Science, however, another researcher pointed out that Thoreau had already described the same phenomenon, both accurately and more poetically. “It is interesting,” Thoreau wrote, “to distinguish the different surfaces,—here broken into waves and sparkling with light … and there quite smooth and stagnant. I see in one place a sharp and distinct line, as if it were a cobweb on the water … as if it were a slightly raised seam.”
As we watched the sunlight sparkle on Lake Placid, it seemed to me that Charlie relished the thought of being scooped by Henry David Thoreau. [Continue reading…]