1884.] NATURAL SCIENCES OP PHILADELPHIA. 319 



made up of a vertical palisade of 120 or more columns, measuring 

 individually from 15 to 40 or 42 feet in height, and from 3 to 5 

 feet, or even more, in thickness. Towards the middle the height 

 of this palisade has been greatlv reduced, partly through the 

 failing of the columns themselves, and partly through the artificial 

 destruction that has here been effected. Above this line, which 

 in some parts is sheared off as evenly as though it had been 

 manipulated b}' the hand of man, the columns suddenly diminish 

 in size, and instead of retaining the vertical position, now arch 

 diagonally upward and outward, meeting from opposite sides to 

 form an apex immediately under the highest point of the exposure. 

 Many of the columns rest horizontally, or nearly so. Beyond the 

 horizontal layer, what may be considered as a third series of 

 columns makes its appearance, and here, again, the vertical posi- 

 tion is assumed. The material of the glacial drift, as indicated 

 by a heterogeneous assemblage of pebbles and boulders, rests on 

 top, forming the subsoil of the region. 



The first impression produced upon the casual observer by the 

 complete exhibit is one indicating disturbance ; the arched or 

 diagonally inclined, and apparently disturbed, position of the 

 columns of the upper and inner portion of the mass, would seem 

 to imply an upheaving thrust from below, just underneath the 

 apex. In other words, it would appear that we were over the 

 seat of some subterranean disturbing force, or in the centrum of 

 volcanic action, and, therefore, in the position of a true vent. But 

 had there been such a thrust as is here implied, we should expect 

 to see its effects revealed in a fracture or dislocation below the 

 top, whereas none such is apparent. On the contrary, the con- 

 tinuit}'^ of the columnar mass is fully as well marked on top as 

 anywhere else, and no indications of special disturbance are any- 

 where manifest. We are hence forced to the conclusion that the 

 irregular and apparently disturbed position of the columns is not 

 in reality due to any disturbing agent, but is merely the result of 

 peculiar conditions of cooling and solidification of the original 

 molten substance (lava). In other words, while some portions of 

 this molten lava " crystallized " into vertical prismatic columns, 

 other portions " crystallized " horizontally, and in all the interme- 

 diate planes lying between the horizontal and vertical. This 

 irregular method of columnar formation, a perfect parallel of 



