48 A GEOLOGICAL HISTORY. 



dip towards the west, and from ten to twenty-five 

 feet or more in thickness. 



5th Trap. — (See plate 2, fig. 5.) This rock, 

 viewed from a distance, has the appearance of an 

 columnar structure on a large scale ; but on a 

 nearer approach, it is seen to be full of seams and 

 fissures in all directions ; with an uneven surface. 

 When the excavations were making at Bergen hill 

 for the railroad, three six-sided joints were ex- 

 posed, similar to those of the Giant's Causeway, 

 of Carraefergus, but in their horizontal seams, they 

 were without those grooves of parting, which the 

 Irish Basalt has. I have seen from three to seven 

 sided pieces at this and many other places ; at 

 Weehawken in many parts and at one particular 

 spot on the shore this rock takes the columnar 

 form. The trap of the Palisades has a long range, 

 beginning at the north end of Staten Island, (where 

 it lies beneath the diluvium,) running from thence 

 along the Hudson River to Vredideka hook, (which 

 according to Captain Partridge, is 668 feet in 

 height) to Harvestraw Bay, where it ends on the 

 Hudson River, from thence it runs west. In this 

 formation are found all the varieties of Trap, Ba- 

 salt, Sienite, Greenstone, Porphyritic Greenstone, 

 Greenstone Slate, Toadstone, Amygdaloid, &c, 

 &c. 



