At Barnesville, samples were taken from two points, one a mile east of town, and one about the same distance north at the site of an old brick yard. Both of these samples were taken so as to include several feet of the blue clay as well as the very thin layer of leached material on top. Scattered crystals of gypsum appear in one of the samples. Furthermore, a test of the adhesive quality of pieces of wet clay pressed together shows that the use of an auger machine might result in very defective structure. Both the clays burn buff… (Clays and Shales of Minnesota, Frank F. Grout and E. K. Soper, The University of Minnesota, Minneapolis, Minnesota, 1914, Page 89)