THE LOST VOLCANOES OF CONNECTICUT. 225 



w^ 



Fig. 4. 



Zuni plateaus, Dutton describes numerous relatively small iso- 

 lated buttes or sharply conical hills, steeper sided than volcanic 

 cones, of a different profile, and without the crater at the top. 

 They consist of dense lava, not in laj^ers spread out from a cen- 

 tral vent upon the surrounding surface, but in a solid mass with 

 columnar structure ; and 

 at their bases it is some- 

 times possible to see that 

 they are inclosed on all 

 sides by the country 

 rock. It is believed that 

 these buttes are nothing 

 more than lava - plugs, 

 frozen solid in the pipes up through which the lava rose at the 

 time of eruption from its deep source to the surface where it 

 overflowed ; but that the time of eruption is so long ago that the 

 cones and all the surface outpourings are worn away, and only 

 the stumps of the plugs remain to tell the tale. Fig. 6 attempts 

 to show the early and late forms, one below the other. Struct- 

 ures of the same kind are 



known in the Black Hills, r^^^^ 



in Scotland, and elsewhere. 

 Perhaps this hint will help 

 us in understanding Con- 

 necticut. 



There is one thing about 

 the ash-bed and lava-sheets 

 in Connecticut that is cer- 

 tainly favorable to the sug- 

 gestion given by the Zuni buttes. The lava-sheets are not now 

 level, as they undoubtedly were when they were poured out ; but 

 all the series of sandstones, ash-beds, lava-sheets, and the rest have 

 been lifted up together on the western side of the valley, so that 

 they slant down or dip to the eastward at a moderate angle. Stand- 

 ing on the bluff of the ash-bed, it is easy to trace its edge north and 

 south, and to perceive that it is continued slanting underground 

 on the east, and to imagine that it was once continued upward 

 into the air on the west ; for on this side the uplifting exposed it 

 to the patient, persistent attack of the weather, by which in the 

 course of ages it may have been greatly worn away. In the same 

 way, other lava-ridges in the neighborhood, such as Mount Lam- 

 entation and the beautiful Hanging Hills, are simply the worn 

 edges of lava-sheets that still plunge underground eastward, and 

 that once rose high into the air westward. 



It follows from this new understanding that if the vent, from 

 which the ashes were blown and the lavas poured, lay to the east 



VOL. XL. — 18 





Fig, 5. 



