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THE POPULAR SCIENCE MONTHLY. 



at least are described by Dr. Dawson, con- 

 sisting of conifers, ferns, sigillarids, cycads, 

 lycopods, etc. Several interesting varieties 

 of this Devonian flora have recently been 

 discovered in Ohio. The fifth flora is the 

 Carbonaceous, the sixth the Liassic, and the 

 seventh the Cretaceous, a flora containing 

 broad-leaved plants of the angiosperms, 

 which, with slight change, has continued to 

 the present time. The Jurassic group is 

 plainly cretaceous, and is entirely unlike the 

 Tertiary. Not a single plant can be identi- 

 fied with any of the Old World tertiary flora. 

 The various tertiary floras of the Rocky 

 Mountains occur in the dried-up basins of 

 old lakes. When the glacial period came on, 

 the trees were entirely destroyed over the 

 northern part of the continent. After the 

 melting of the ice, the present flora made 

 its appearance. 



The Depression of our Atlantic Coast. 



Professor George H. Cook, State Geolo- 

 gist of New Jersey, has presented, in a paper 

 which he has read before the American As- 

 sociation, a large array of evidence showing 

 that the Atlantic coast of our continent is 

 gradually subsiding. It consists largely of 

 the testimony afforded by the remains of 

 ancient forests, composed for a considerable 

 part of upland growths, which have been 

 found in various places from the Carolinas 

 to Greenland, either submerged at high wa- 

 ter or at depths beneath the surface lower 

 than the high-water mark of the neighbor- 

 ing coast, and at these places sometimes 

 with present or former swamps over them. 

 Sunken forests possessing some or other of 

 these characteristics are mentioned as exist- 

 ing in the Carolinas and Georgia, where 

 they were noticed by Bartram in 1773, Lyell 

 in 1845, Professor Tuorney, of South Caro- 

 lina, in 1846, and in Albermarle Sound, 

 North Carolina, by Dr. Emmons. General 

 Cutts, of the Coast Survey, has observed 

 timber in the place of its growth several 

 feet below the level of tide-water along the 

 shores of Chesapeake Bay, in Virginia. The 

 coast of New Jersey is marked by the oc- 

 currence of timber and stumps below the 

 present tide-level in the marshes which bor- 

 der the State from the head of Delaware 

 Bay to Cape May, and thence to the mouth 

 of the Hudson. A marked example of yel- 



low-pine stumps may be observed in the 

 banks of the canal which connects South 

 River at Washington with the Raritan. 

 Similar submerged forests on Long Island 

 have been described by Elias Lewis, Jr., in 

 " The Popular Science Monthly." In Massa- 

 chusetts, they have been observed at Nan- 

 tucket, Ilolmes's Hole, Yarmouth, and Prov- 

 incetown ; in New Hampshire, at Eye Beach ; 

 in Maine, at Portland ; and at the head of 

 the Bay of Fundy in Nova Scotia. Other 

 evidences are afforded by the subsidence of 

 human structures since the period of settle- 

 ment; in the flooding of farm-lands that 

 have had to be abandoned, the submersion 

 of boat-stakes, and the approach of the sea 

 to buildings on the shore. Instances of this 

 kind are observable at Southampton, Long 

 Island, Barnegat, New Jersey, the shores of 

 Delaware Bay, and on the west coast of 

 Greenland. The encroachments of the sea at 

 Long Branch and the changes going on at 

 Sandy Hook are public facts. Professor 

 Cook believes that the change thus marked 

 is common to the whole northern hemisphere. 

 It is certainly taking place in parts of 

 Sweden. Some doubt has been thrown 

 upon the theory of a subsidence from the 

 fact that sea-shells and buried timber, both 

 of kinds now living, have been found in de- 

 posits a few feet above the present sea-level. 

 These instances are, however, regarded as 

 belonging to another era than the present 

 period of depression, and are distinguished 

 by several important differences of features 

 from those now under consideration. Pro- 

 fessor Cook thinks that they belong to a 

 previous period of depression ; that the 

 present period may not have been going on 

 for more than five hundred or a thousand 

 years, and that in the one which preceded 

 it the surface of the upland was ten feet or 

 more nearer the sea-level than it now is. 

 He adds : " A careful study of the numer- 

 ous cases like this will satisfactorily prove 

 that there have been other periods of alter- 

 nate depression and elevation in compara- 

 tively recent times, the phenomena of which 

 are so nearly alike that they are very com- 

 monly confounded with each other. And, 

 when they are clearly distinguished, it will 

 be found that the rise or the depression is 

 one common to our whole coast, and proba- 

 bly to the whole northern hemisphere." 



