THE NEWARK ROCKS 47 



to estimates made from the angle of dip and the width of out- 

 crop. At Fort Lee a well penetrated the trap for 875 feet 

 before reaching the underlying metamorphosed shale and the 

 total thickness here is about 950 feet. 



In New York the thickness varies considerably, judging by 

 the width of outcrop. A thickness of considerably over 700 

 feet is known to occur north of Nyack, whereas north of Rock- 

 land Lake it probably does not exceed 300 feet. 



The thickness of First Mountain at Paterson is estimated to 

 be 600 to 675 feet; at Orange Valley about 670 feet; at Scotch 

 Plains about 680 feet, and at Chimney Rock about 580 feet. 



With the exception of the thickness at Scotch Plains these 

 figures agree closely with those obtained for First Mountain by 

 Darton along the same sections. At Scotch Plains the out- 

 crop is narrower than elsewhere, but the dip of the inclosing 

 shales is steeper and his estimate of 450 feet is probably too 

 low. 



The thickness of Second Mountain is apparently somewhat 

 greater than that of First Mountain, but owing to the faults 

 which traverse it, estimates are liable to error. Darton's figures 

 range from 600 to 8 50 feet. My own estimates, based on the 

 width of outcrop and the dip, range from 840 feet to 990 feet. 

 At Caldwell the well at the Mount St. Dominic Academy 

 penetrated the trap for nearly 800 feet, but some addition must 

 be made for what has been removed from the crest of the ridge 

 by erosion. 



At Millington the thickness of the Long Hill trap sheet is 

 about 300 feet. At Pompton a well drilled at the Norton house 

 is reported to have passed through but seventy feet of trap 

 before reaching sandstone. Hook Mountain, east of White 

 Hall, has an apparent thickness of 400 feet or more. 



The New Vernon trap-sheet has a thickness of about 250 

 feet, measured at the gorge near Green Village. 



The outcrop of the New Germantown sheet is comparatively 

 narrow, but the dip is steep and the thickness is estimated to be 

 at least 400 feet. 



