76 O. D. VON ENGELN 
Recovery and nature of material.—tIn the course of gardening 
operations a trench approximately 25 feet long, 4 feet wide, and 3 feet 
deep was made in the lake clay. The clay deposit continued right 
up to the surface and was undisturbed and unmodified except for 
the top 12 or 16 inches that had been rendered more friable and 
amorphous in structure by plant growth and tillage. Below that 
the clay was exceedingly compact, fine grained, and slightly jointed 
with one-half- to one-inch spacing. From this clay, below the soil 
Fic. 2.—Iceberg-dropped bowlders recovered from lake-clay deposit. Smaller 
pile apparently from single berg. Those marked A are striated or soled. Left to 
right diameter of bowlder at top of small pile is three inches. 
layer, were dug the bowlders illustrated in Fig. 2. For the most 
part these were found in clusters of from three to five or more 
specimens occurring near each other. ‘The bowlders in the smaller 
pile in Fig. 2 were all clustered within some 3 cubic feet of the clay 
at about the same depth. The total weight of all the bowlders is 
74.5 pounds, of those in the smaller pile 8.5 pounds. In addition 
there were no doubt other rather large-sized bowlders that were 
overlooked, as no effort was made to go over the material with 
extreme care; and many observed smaller pebbles were not pre- 
served. Inany event the actual mass of the material present within 
the space excavated has no special significance; the figures are 
quoted merely to give some idea of the quantity of such bowlder 
