ACTUALITY OF CHANGE OF LEVEL. 783 



(1.) A section of the coal formation of Illinois, described by Worthen, contains 16 

 coal beds, large and small, separated by fragmental beds and limestones containing 

 abundant remains of marine life. The coal beds indicate eras of emerged land, the 

 marine fossils, intervening eras of submergence, and their number shows that, at least, 

 sixteen alternations between the two conditions there took place in the Carboniferous 

 period. Facts make it certain that the great interior sea of the continent communicated 

 at that time freely with the ocean to the south. The same region thus went up and 

 down, changing the dry land outline and the sea depths; and the changes went on with 

 extreme slowness, for coal beds, as well as the much thicker marine beds, were slow in 

 accumulation. Facts of similar import are afforded by all the successive formations, 

 from the Primordial upward, and alike on all the continents. 



(2.) During Paleozoic time, between 30,000 and 40,000 feet in average thickness of 

 sedimentary beds were laid down, according to geologists of New York and Pennsyl- 

 vania, along the region now covered by the Appalachian Mountains; of these, many 

 bear evidence of shallow water origin; and in the last period of that prolonged era, the 

 Carboniferous, peat-making marshes were spread out over the top of the great pile, but 

 little above the sea level. A sinking of 30,000 to 40,000 feet is thus proved for that region. 

 At the same time the region of Illinois and other parts of the Mississippi basin under- 

 went a sinking not exceeding 5,000 feet, and northern New York and Canada little if 

 any, and thus there were unequal changes of level during the same era in different parts 

 of the same continent. Further, the sinking in both regions went on with the alterna- 

 tions in level indicated in paragraph (1). 



(3.) The Red Sandstone formation (Triassico-Jurassic) of the Connecticut Valley was 

 made in an estuary, and therefore below the sea-level; and now, in its northern part, in 

 Massachusetts, it has, in Mount Toby, a height of 1,300 feet above the sea, while in its 

 southern part, near New Haven, it is less than 400 feet in height; the level follows 

 approximately the level of the crystalline rocks either side of the Connecticut Valley, 

 and the trap ranges associated with it show a similar change of level, though overtop- 

 ping the sandstone because of their superior hardness. 



(4 ) In the Cretaceous period, the region of a large part of the Rocky Mountains and of 

 the Atlantic, Gulf, and Pacific borders of the continent were beneath the sea, but mostly 

 near its surface; and the marine life of the sea contributed to the forming Cretaceous 

 beds. Now, the marine beds, filled with Cretaceous fossils, are at a height of 10,000 to 

 11,000 feet in the Rocky Mountain region, at a maximum height, on the Pacific border, 

 of only 5,000 feet, in Alabama of 700 to 800 feet, and in New Jersey not over 400. 



(5.) In the early Tertiary, the European and Asiatic seas grew Nummulites, and 

 limestones were made of the multiplying disks. Now, those Eocene Nummulitic beds 

 are at a height of 9,000 feet in the Pyrenees, 11,300 feet in the Alps, 16,500 feet in the 

 Himalayas in Western Thibet, and a few hundreds only near Paris. 



(6.) In the Quaternary, before the disappearance of the ice, the region along the St. 

 Lawrence, near Montreal, as shell deposits show, was about 500 feet below its present 

 level, that of the northern half of Lake Champlain, on the same evidence, over 300 

 feet; the coast of Maine, 200 to 220 feet; Southern New England, along Long Island 

 Sound, not over 25 feet. There has, consequently, been since then (1) a change of 

 level at these places of unequal amount; and (2) one varying in height more than 450 

 feet in a difference of latitude of five degrees. And this was, in all probability (pp. 

 553, 561), only a part of a much wider change of level. 



(7.) The region of atolls over the tropical portion of the Pacific Ocean, having a 

 length from east to west of 5,000 miles, has undergone a subsidence, as Darwin has 

 indicated, from a few hundreds to thousands of feet in depth, since the coral animals 

 began to make there their coral reefs; while the subsidence on the borders of the 

 region of atolls, as the limited reefs of the high islands show, was comparatively 

 small. 



(8.) Movements, up or down, are now going on along the coast of North America, 

 Scandinavia, Greenland, and elsewhere. Alexander Agassiz states that at Tilibiche, 

 in Peru, there is a coral limestone, 2,000 to 3,000 feet above the sea-level, extending 



