INTRODUCTION 1 1 



came out of the water. Some of what is now the coastal strip of 

 New Jersey, all the Cape May region, some of the territory just 

 north of the pine-barrens, and much of the lower Delaware Valley, 

 was either not above water at all, or only slightly so, and in the 

 latter case was soon considerably eroded. This cutting down of 

 the emerged Beacon Hill by erosion, particularly to the south and 

 east, was very great, so that finally it was a very different region 

 from the great upland plain it is supposed to have been immedia- 

 tely after the Post-Miocene uplift. 



21. This erosion of the Beacon Hill formation was brought to 

 an end finally by the gradual subsidence of the whole region. 

 Little by little the lower part of New Jersey sank so that ulti- 

 mately everything except the then upland Beacon Hill formation 

 (the present pine-barrens) was submerged (Pensauken Submer- 

 gence). It is curious to note, by the way, that the encroachment 

 of the sea thus occasioned by this submergence has been marked 

 by several plants that are normally salt-marsh species, which seem 

 to have followed this ancient marine shore-line. On the northern 

 and southern edges of the dotted area on the map (pi. 4), have been 

 found Hibiscus Moscheutos (see pi. 9) and Ptilimnium capillaceum, 

 and there may be others. This dotted area is the old Pensauken 

 Sound and it is significant that these maritime species should be 

 found today miles from the sea and evidently relics of their 

 migration along the shores of Pensauken Sound. At least, the 

 Hibiscus has spread so that it occupies some stations in the middle 

 of the old Sound bed, notably near Spotswood, Middlesex Co., 

 and near Princeton Junction. 



22. The map (pi. 4) shows the extent of this submergence, as 

 everything covered by the dotted area was under water. The 

 undotted light area was not submerged, and has never since been 

 submerged. After an indefinite period of subsidence the whole 

 dotted area was again raised so that all of lower New Jersey as we 

 know it today came out of the water. The Pensauken formation, 

 which is the geologists' name for most of the material eroded from 

 the uninterruptedly emerged Beacon Hill, was itself subject to 

 erosion, giving us the present characteristic stream beds of the 

 coastal plain in the state. 



23. The next step of serious significance was the encroachment 

 of the ice-sheet, which came down to Perth Amboy, not more 



