356 ANNUAL OF SCIENTIFIC DISCOVERY. 



shallow swamps, and in the bottoms of the deeper swamps, such timber is 

 found, which is to them a plain evidence that it grew there. Further, they 

 find at the bottom of such swamps gum and magnolia trees which have 

 grown upon the hard ground. Pine stumps are also found at considerable 

 depths below the surface ; these are tap-rooted, and their roots reach the so 1 , id 

 ground so that they are not liable to settle. It is the general impression, 

 however, that the cedar swamps do not settle as long as they remain con- 

 stantly wet. 



After examining all I have been able to find written upon the subject, and 

 after studying it in the field, I can think of no other theory which will apply to 

 all the facts, except that of a slow and continued subsidence of the land. 



The rapid wear of the shores may fairly be adduced as confirming my 

 conclusions in regard to subsidence. A few cases of this rapid wear may be 

 given. Egg Island, a point well known to those who are familiar with Dela- 

 ware Bay, is put down on the first map, made by the proprietors of West 

 Jersey, in 1694, as containing three hundred acres of land. It now contains 

 only about three-fourths of an acre at low water, and high tides cover it en- 

 tirely. Capt. J. W. Herbert, a very intelligent wreck master, at Kcyport, 

 has a number of marks on the beaches to determine the location of sunken 

 vessels, and from these he is able to measure the wear from year to year, and 

 the average which he deduces from these is not less than twelve feet a year 

 along the whole shore. On Long Island the wear of the beaches is not so 

 uniform, but is perceptible. On the east end of the Island the wear is very 

 great, and has attracted attention ever since the first settlement of the 

 country. 



As to the rapidity with which this subsidence is going on, we have no very 

 certain data. There are some stumps of trees, probably cut within the last 

 150 years, which are now run over by high tide, so that the person who 

 pointed them out to me was confident that there must have been a change of 

 three feet in the tide. At a milldam one person was confident that the tides 

 rose higher than they did twenty years ago, though how much he could not 

 tell, for a mark which he had made had become obliterated. At another 

 place a miller told me he could not run his mill as long as he used to be able 

 to, because the tide backed up against his wheel. He thought he had lost 

 eight inches in twenty-five years. At another mill the tide rose some twelve 

 or fifteen inches higher, and its wood-work and foundation were placed on 

 the solid upland. Another mill, built 100 years ago, has lost so much that 

 the tides come up half way on the dam, and they can only run that mill by 

 having built another dam below it to keep out the tide. 



Another mill had been watched for twenty-five years, and my informant 

 was confident it had lost four inches, and, ho thought, more. 



From these facts we may set down the subsidence at, perhaps, two feet in 

 a century. 



With the exception of the statements of two pilots, upon the Raritan River, 

 I have nothing upon which to base any estimates for the pi*csent rate of sub- 

 sidence in the vicinity of New York. One of the pilots founds his conclusion 

 upon observations made upon the wharf at Washington, and is confident 



