DILUVIUM. 281 



responding cavities are of similar shapes, as in the 

 following sketch : 



Near Gape Cod, in Massachusetts, these eleva- 

 tions rise to a height of 200 or 300 feet, and are 

 very numerous, giving to the country a hilly and 

 even mountainous aspect. On digging into them, 

 they are found to he composed of a loam, which 

 has thus been piled up and scooped out by the ac- 

 tion of v^ater. Similar ones formerly existed on 

 New- York Island, and over much of the surface 

 where the city is now built. Some of these were 

 250 feet high, and made up of sand, gravel, and 

 bowlders of greenstone, porphyry, serpentine, and 

 granite ; most of which evidently came from the 

 Palisades across the river. Occasionally, also, 

 masses of secondary limestone, containing fossil 

 shells, were met with, which must have been brought 

 from above the Highlands. Occasionally we meet 

 with consolidated alluvium, composed of pebbles 

 and, perhaps, masses of different kinds of slate, and 

 consolidated together by a cement of iron or lime ; 

 which, having been dissolved in water, has thus been 

 diffused through the mass. Such conglomerates are 

 often called pudding-stone. The reader will now be 

 able, perhaps, to form a correct idea of what is un- 

 derstood by diluvial ; and he can readily perceive the 

 mode of its formation, if he w^ill suppose the agents 

 which we have described as destroying rocks 

 Y 



