Cambridge, Mass. Thoreau checks out American Medical Botany, 1817-21 by Jacob Bigelow, volumes 1, 2, 3, 4, 5, and 6, and The North American Sylva by François André Michaux, volumes 2 and 3, from Harvard College Library (Companion to Thoreau’s Correspondence, 289).
Concord, Mass. Thoreau writes in his journal:
  What is a chamber to which the sun does not rise in the morning? What is a chamber to which the sun does not set at evening? Such are often the chambers of the mind, for the most part.  Even the cat which lies on a rug all day to prowl about the fields at night, resumes her ancient forest habits. The most tenderly bred grimalkin steals forth at night,—watches some bird on its perch for an hour in the furrow, like a gun at rest. She catches no cold; it is her nature. Caressed by children and cherished with a saucer of milk. Even she can erect her back and expand her tail and spit at her enemies like the wild cat of the woods. Sweet Sylvia!What is the singing of birds, or any natural sound, compared with the voice of one we love? To one we love we are related as to nature in the spring. Our dreams are mutually intelligible. We take the census, and find that there is one.
