GEOLOGY OF DELAWARE COUNTY. 413 



A further uphcavnl of the land followed, perhaps somewhat paroxysmal in its 

 character, that placet! the upper beds out of reach of all currents, but leaving 

 the country occupied by the lower beds still under water, and at the same time 

 subjecting; the sandstone rocks north of us to disintegration. A current was 

 established that swept over these rocks, and in its course over the southeastern 

 front of the County, (which still remained submerged.) and carried with it these 

 more distant disintegrated materials, to be mingled with the accumulated wasie- 

 agc of the rocks in the vicinity. The presence of the pebbles in these lower 

 beds is not the only evidence of this current and its direction. The water-wora 

 blocks of hard sandstone are larger and more numerous in the vicinity of Phila- 

 delphia, than they are in the vicinity of Darby. Still lower down they are again 

 smaller, and probably disappear before we reach the circular line, where even 

 gravel beds are scarce. 



Another upheaval in its turn placed these lower beds above water. Whether 

 it was gradual or sudden can only be a matter of conjecture, but there is unmis- 

 takeable evidence that this upward movement did not cease till the land was 

 higher above the water than the position it now occupies. Unmistakeable 

 evidence also exists that there has been a subsidence in the land constituting the 

 southern margin of the County, and there are those who believe that this subsi- 

 dence, however slow it m.ay be, is still in progress. 



The proof of this subsidence rests upon a fact not generally known, and was 

 only brought to the knowledge of the author within a few years past. This fact 

 is the existence of the remains of an ancient cedar swamp on the marsh of Tini- 

 cum Island that would now be under tide-water but for the meadow banks. The 

 white cedar, (Ciipressiis thyoides, Michx.) as is well known, only grows with vigor 

 in sphagnous swamps that are abundantly supplied with spring water. There 

 is proof at hand to show that this ancient swamp was once provided with all 

 the conditions necessary to insure the thrifty growth of its cedars. Internal 

 terrestrial forces had adapted the land to their growth. Planted by the hand of 

 nature, they grew and flourished for ages. A subsidence of the land ensues ; 

 they are overwhelmed by the tide, die out, and but for the almost miraculous 

 durability of their timber, not a vestige of these once stately trees would remain 

 to mark the place of their growth. As it is, but a few stumps and a few trunks 

 are visible at the surface, but doubtless many more are buried in the marsh. 



The relics of this swamp was pointed out to me by Sketchley Morton, Esq., of 

 Springfield, who informed me that his attention had been called to it by his 

 father many years since. 



Nearly all the accounts we have of the fort built on Tinicum Island by Gov. 

 Prinlz, represent (in the English translation) that it was built of Hemlock logs. 

 This is unquestionably a mistake, as no hemlock, beyond a few scattering, 

 stunted trees, ever grew in this part of the country, and none in the vicinity of 

 Tinicum. It has occurred to me, that at the time Printz came to this country, 

 large numbers of the cedar logs of this ancient swamp were lying on the sur- 

 face of the mud, and that this early Swedish fortress was built of these logs. 

 It will be remembered that the fort accidentally took fire and was burned, a 

 circumstance very likely to happen, if built of cedar logs after they had become 

 dry ; but hemlock logs rot before they dry sufficiently to ignite. Part of the old 

 Ferry-house, at Darby Creek Ferry, within a few hundred yards of the site of the 

 ancient Cedar Swamp, and erected in 1694. is built of white cedar logs, which 

 are still in a perfect state of preservation. Another very old house in the imme- 

 diate neighborhood is built of the same timber. It is not probable that the 

 timber for these humble edifices was brought from distant places in Jersey at 

 that early day, and the fact of their construction out of cedar is almost conclu- 

 sive that there was no scarcity of cedar logs strewed on the surface near the 

 spot where the trees had grown. Such logs are still often encountered in digging 

 the marsh ditches in this vicinity. 



