76 



GEOLOGY. 



Fig. 26. 



away above, and below extend to unknown depths be- 

 low the water. Looking like ruins of some ancient 

 work too great for man, it is not strange that popular 

 tradition has connected with them the agency of giants. 

 In most cases the tendency is only partially exhibited, 

 as, for instance, in East and West Rock, at New Haven. 

 The columns are prisms, having from three to eight 

 sides, commonly five or six, and 

 they are generally divided into 

 blocks by joints, as seen in 

 Fig. 27. Each block is usually 

 concave on its upper part, hav- 

 ing the lower convex end of 

 the block above fitting into it. 

 Commonly the columns stand 



Fig. 2T. 



upright, but sometimes 

 they are horizontal, as in 

 Fig. 28, representing a ba- 

 saltic dike in North Caro- 

 lina. The appearance in this case is that of a wall built 

 as a fortification. Sometimes the columns are in the po- 

 sition represented in Fig. 29. Sometimes the columnar 

 and massive forms are conjoined, as seen in this figure. 

 A remarkable example both of this position of columns 



Fig. 28. 



