IS 
BULLETIN OF THE NATURAL HISTORY SOCIETY. 
I have made some study of them, with results as follows. 
Portage Island is composed of a series of approximately- 
concentric low dune-beaches with intermediate shallow hollows, 
a series of sand swells or billows, arranged somewhat as shown 
by the accompanying map, which, as to the beach lines, is merely 
a crude sketch. Near its northern end the beaches, bearing 
the oldest woods, are parallel with the axis of the island, and 
here they are being cut away, together with their covering woods, 
by the sea. Farther south these same beaches curve around 
to the westward and finally sink gradually beneath the waves 
of the Inner Bay, their summits projecting as points, while 
their intermediate hollows form coves of salt marsh. These 
beach lines, as may be seen at many points, form only above 
the reach of the highest tides, and their gradual disappearance 
beneath the waters of the Inner Bay forms one of the very best 
evidences we possess of progressing subsidence in this region, 
evidence still further strengthened by the occurrence, near the 
north end of the island, of peat in situ on the beach below high- 
water mark. Farther south the beaches are very obviously 
newer; at first they are clothed with young birch woods but 
finally they are entirely bare except for the ubiquitous beach 
grass. Towards the extreme south the beaches are very wide r 
with very broad hollows, and are forming so rapidly that not 
only have they every aspect of newness, but the driftwood some 
hundreds of yards from the sea has not yet had time fully to 
decay. The rapidity of growth, far surpassing anything I have 
seen elsewhere in this region, is fully confirmed by local tradition. 
Not only is the growth thus rapid at present, but it appears 
to have commenced abruptly; for not far from the margin of the 
older woods and beaches there lies a great broad beach hollow 
now occupied by a considerable lake, while two or three others 
of much smaller size exist in the woods near by. It is thus 
evident that while this island is now being rapidly washed away 
at its northern end it is forming rapidly, no doubt from the same 
materials, at its southern end, and the whole island is, so to 
speak, rolling southward along its outer margin. In this respect, 
as well as in the general construction of its beaches, in its lower 
