32 ROYAL SOCIETY OF CANADA 
form the bottom of such basins and have reduced their original depth 
to a total upwards of some forty or fifty feet as now found. Originally 
also, these basins had open communication with the sea in precisely the 
manner which obtains at present among the numerous islands of Mahone 
Bay in Nova Scotia, and where later changes might establish conditions 
exactly parallel with those now found at Kittery and York. 
Two of these basins in particular, serve to illustrate in a very strik- 
ing manner the course of development which, through a somewhat 
prolonged period, has resulted in the formation of the marshes now under 
discussion. One of these basins lay between Cutts’ Island and the 
mainland with an opening to the sea on the easterly side, and a narrow 
and shallow channel running southward into what is known as Chauncey 
Creek. The other basin lay between Cutts’ and Gerrish Islands with 
two outlets into the ocean on opposite sides of the islet now known at 
Sea Point, and with a shallower but broad outlet toward the west, leading 
into Chauncey Creek. 
Evidence has been brought forward to show that in Pliocene time 
the general area of the territory was considerably higher than at present, 
and on the basis of the known rate of subsidence which,may be assumed 
to apply to this locality, the whole district must have been at least eight 
to ten feet higher than at present, probably much more. This would 
mean that the shallow channel leading from the Sea Point Basin west- 
ward, and from the Brave-Boat Harbor Basin southward, were low lying 
portions of the mainland which did not afford communication with 
Portsmouth harbor until a much later period, and that the present 
rocky channel known as Chauncey Creek did not exist, its location being 
occupied by sedimentary deposits. With a continued subsidence, 
however, water gradually found its way westward and southward from 
the two basins under discussion, and flowing over the slight incline 
between Gerrish Island and the main land, rapidly eroded ‘the loose 
material and cut down to the underlying rock, thus forming a connec- 
tion with Portsmouth harbor through Chauncey Creek and the smaller 
channels at its head. 
Hither concurrently with these changes or at a somewhat later period, 
barrier beaches were thrown across the openings of these basins, so that 
for the Brave-Boat Harbor Basin there was one such barrier, and for 
the Sea Point Basin there were two. When these were completed, the 
drainage of the surrounding more elevated areas converted both basins 
into fresh water ponds, the overflow from which then found its only 
outlet southward and westward through Chauncey Creek into Ports- 
mouth harbor. It isa matter of very great interest in this connection, 
that at various points along the coast, especially at York Beach, 
