[balti]

Thoreau was anxious to get the balance right. “This habit of close observation—in Humboldt—Darwin & others. Is it to be kept up long—this science?” he asked himself. As Walls noted in her previous book about Thoreau’s relationship to 19th-century science, Seeing New Worlds, his reading of Charles Lyell’s revolutionary Principles of Geology in 1840 had given him the insight that small details add up to one bigger truth: Lyell argued that the Earth had been shaped gradually by minute changes, and that these slow forces were still active. Steeped in the sciences, Thoreau emphasized that orderly data needn’t be dead. Carl Linnaeus’s binomial system for classifying plants was “itself poetry,” and in the early 1850s Thoreau jotted in his journal, “Facts fall from the poetic observer as ripe seeds.”

Still, Thoreau felt the limits of disciplined scrutiny. “With all your science can you tell how it is, and whence it is, that light comes into the soul?” he asked in one of his July 1851 entries. In December, when he saw a crimson cloud hanging deep over the horizon on a cold winter day, he wrote, “You tell me it is a mass of vapor which absorbs all other rays,” only to lament that this was not a good enough explanation, “for this red vision excites me, stirs my blood.” What kind of science was this, he wanted to know, “which enriches the understanding but robs the imagination?” The following summer he summed up the dilemma. “Every poet has trembled on the verge of science,” he wrote after a long day at the Sudbury River, even as he also noted, “I wanted to know the name of every shrub.” Was his knowledge becoming so fine-grained “that in exchange for views as wide as heaven’s cope I am narrowed down to the field of a microscope”? He saw “details not wholes,” and feared being “dissipated by so many observations.” Or could the sensual be entwined with the scientific? For Thoreau, in a short entry about frogs, that happened: “They express, as it were, the very feeling of the earth or nature. They are perfect thermometers, hygrometers, and barometers.”