Note 220 — Chapter V · THE ACTION OF WORMS IN THE DENUDATION OF THE LAND.
Reading edition
A. A. Julien “On the Geological action of the Humus-acids,” ‘Proc. American Assoc. Science,’ vol. xxviii., 1879, p. 311. Also on “Chemical erosion on Mountain Summits;” ‘New York Academy of Sciences,’ Oct. 14, 1878, as quoted in the ‘American Naturalist.’ See also, on this subject, S. W. Johnson, ‘How Crops Feed,’ 1870, p. 138.