R. M. Brown — Clays of the Boston Basin. 447 



of sand in the lower portions of the clay and by dark bands, 

 probably of vegetable matter, in the upper portions. Below 

 the clay was a bed of sand, and above a thin layer of till which 

 ran out towards the south (iig. 2). The disappearance of the 

 till was due probably to the removal of the material in a pre- 

 vious excavation further to the west. Before a second visit to 

 the pit was made enough material had been removed to yield a 

 better section (fig. 3). The bed of sand at the bottom of the 

 clay (shown in fig. 2) proved to be a stratum of sand 14 inches 

 thick, underlain by more clay. The sand was of fine texture, 



Figure 4. — Cross-section of end of Drumliu in Eevere, Mass. A. = Clay, 

 B. = Sand and Clay, C. = Till. 



similar to our beach sands, and homogeneous throughout. A 

 single small slate pebble was the only break in the uniformity 

 of the sand bed. At the same time enough of the talus had 

 been removed to show the sand bed extending to the edge of 

 the till and there cut oif before the deposit of the till. To the 

 north the clay was much more crumpled, and the interstratified 

 sands were, as a general rule, thicker than the layers above the 

 thick sand bed. The till averaged 18 inches in thickness, was 

 made up of coarse and fine material, and extended over the 

 entire section of the hill remaining. The slope of the hill was 

 very gradual and the question of the slipping of the till over 

 the clays was negatived by the rolling surface of the clay as well 

 as by the slope. 



In seeking for other instances of the same thing, a section 

 across the trend of a drumlin at the junction of Shirley Avenue 

 and Nahant Avenue in Revere, Mass., was found. The drum- 

 lin had the northwest — southeast position of the drumlins of 

 the district. The core of the drumlin was clay (fig. 4). 

 Above the more solid bottom clay was a thickness of about 

 three feet, made up of alternating layers of sand and clay, the 

 sand increasing upwards. Over the sand was 14 feet of till. 



Am. Jour, Sci, — Fourth Series, Vol. XIV, No. 84. — December, 1902. 

 31 



