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STUDIES FOR STUDENTS 



linearly upon the plane of stratification. When rubbed to a batter 

 in water and allowed to dry and crack, the edges disintegrated and 

 the cake softened more rapidly, indicating that the original closer- 

 knit texture had given it superior resistance. Drying and baking 

 up to the boiling-point chd not affect the result. 



The modeling clay was not baked, but, in all respects tested, 

 behaved like the mixtures of Champlain clay and silty clay. 



Finally in August, 1906, excellent opportunities were offered 

 for observing the behavior of the unctious and sticky gray mud of 

 New Haven harbor; a reclamation company building turf walls 

 around many acres of salt marsh land, and pumping water, mud, 

 and sand from the center of the harbor into these artificial reservoirs, 

 the sediment setthng and the water draining away. In this way 

 from 6 to 20 feet of sediment were laid down under most favorable 

 conditions for observation. It was found that from mid July to mid 

 August beds of gray mud up to a foot in thickness, resting upon 

 sand, had dried and cracked into irregular polygons i, 2, and even 3 

 feet in diameter, the cracks opening from 3 to 4 inches. 



Where the mud was thicker, the bottom was still soft, but the 

 top was cracked. Where the water was s'fill standing no cracks had 

 formed, but upon the disappearance of the water they began to appear 

 as wedge-shaped cracks, while the top clay was still soft to the hand 

 and the bottom so fluid as to make walking impossible. 



These cracks had formed and the clay underlain by sand had 

 dried and hardened to the depth of a foot during an interval, as 

 stated, from mid July to mid August, during which time the mean 

 temperature was 71° F., the average humidity 0.83, the precipitation, 

 in thirty-one days, 3.0 inches, ten days partly cloudy, and twelve 

 days cloudy. 



Rain had failed to efface these cracks, though washing more or 

 less mud into them, especially when the cracks were still young and 

 narrow and the clay not yet hardened. Refiooding by pumping was 

 observed to soften the clay to the consistency of a stiff gelatine and 

 expand it somewhat, but did not obhterate the sharpness of the cracks 

 even in the course of days; and where mud or sand was washed 

 over the 'surface, the cracks were permanently buried and preserved. 

 Where filled with similar mud and redried, the filhng may be detected. 



