BY A. GIBB MAITLA^T), C.E., F.G.S. 19 



On examining any recent geological map of the United 

 States, it will be found that the lowest member of each series 

 occurs on the surface along the Atlantic coast from Long Island 

 as far as the James River in Virginia. It reappears from 

 beneath a mantle of Tertiary and Recent beds on the western 

 boundary of the State of Georgia, and continues without 

 interruption as far into Kentucky as the junction of the Ohio 

 and Tennessee Rivers, resting alternately on impervious beds of 

 Carboniferous and Archean age. The Cretaceous rocks again 

 rise from beneath Tertiary rocks in Arkansas, near the head of 

 the Onachita River, and cover a large area in the western 

 interior, flanking the Rocky Mountains, from Texas northwards 

 through the States of Kansas, Nebraska, and Dakota, as far as 

 the Canadian frontier, and thence through Manitoba, Saskat- 

 chewan, Athabasca, British Columbia, and Alberta. The 

 western boundary of these rocks in the United States is in 

 Montana, from whence it travels southwards through Wyoming, 

 Utah, Colorado, and New Mexico. Cretaceous beds, having no 

 physical connection with those above mentioned, are known 

 along the Pacific border in the ranges to the west of the 

 Sierra Nevadas. 



The Atlantic Border Region, in which the water-bearing 

 strata crop out, consists of land rising gradually from the sea to 

 the foot of the Appalachian Ranges, increasing in width to the 

 south, and attaining a greater elevation as the mountains are 

 reached. The western edge of this coast belt in Pennsylvania 

 varies from one to three hundred feet ; in Virginia it is about 

 500ft. ; while in Georgia it attains a height of from 300ft. to 

 400ft. above sea level. Everywhere in this region the Tertiary 

 and Cretaceous beds have a gentle dip towards the sea. 



In the State of New Jersey, the Cretaceous formation can be 

 divided into an upper and lower series, the former consisting for 

 the most part of impervious clays, marls and sands, about 500ft. 

 thick, the basal bed being a clay marl of some thickness. The 

 lower series is made up of plastic clays, sands and gravels, 

 attaining an aggregate thickness of 347ft. ; at the base is a thick 

 mass of sandstone, arkose, gravel, sand and clay, known as the 

 Potomac formation. None of these beds, which are continuous 

 to the northward through Long Island, appear to rise much 

 above 250ft. above sea level. 



