Geological Changes of the Cape.—How they affected the
Wreck.—Effects of Single Storms.
A shore composed of the geological formation known as “drift,” and
directly exposed to the action of the sea, is doomed to undergo many
and rapid changes. By comparing the map, inserted on the next page, of
Cape Cod as it was at the time of its discovery, with the modern map,
the great changes made on the eastern coast by winds, waves and tides
will be at once made apparent.
[Illustration:
1. Site of former entrance to Potanumaquut or old ship harbor. The
locality of the old ship is represented in black.
2. Present entrance to Chatham harbor.
3. Island Ledge.
4. Webb’s island.
5. Namskachet creek. ]
In regard to the geological changes, we present here a short extract
from the recently published and highly entertaining work of Thoreau:
“Between October, 1849, and June of the next year, I found
that the bank [in Truro] had lost about forty feet in one place,
opposite the lighthouse, and it was cracked more than forty feet
from the edge at the last date, the shore being strewn with the
recent rubbish. But I judged that generally it is not wearing away
here at the rate of more than six feet annually.... The general
statement of the inhabitants is, that the Cape is wasting on both
sides, but extending itself on particular points on the south and
west, as at Chatham and Monomoy Beaches, and at Billingsgate, Long
and Race Points. James Freeman stated in his day that above three
miles had been added to Monomoy Beach during the previous fifty
years, and it is said to be still extending as fast as ever. A
writer in the Massachusetts Magazine, in the last century, tells
us that ‘when the English first settled upon the Cape, there was
an island off Chatham, at three leagues’ distance, called Webbs’
Island, containing twenty acres covered with red cedar or savin.
The inhabitants of Nantucket used to carry wood from it;’ but he
adds that in his day a large rock alone marked the spot, and the
water was six fathoms deep there. The entrance to Nauset harbor,
which was once in Eastham, has now travelled south into Orleans....
“On the eastern side the sea appears to be everywhere encroaching
on the land.... The bars along the coast shift with every storm.”
In the hurricane of April, 1851, in which Minot’s Ledge lighthouse was
swept away, many and great changes took place on the eastern side of
the Cape. A deep and spacious entrance was made into Chatham harbor,
which still continues to be very advantageous to the towns of Harwich
and Orleans; but the subsequent extension of bars, from an island lying
in the direction of Chatham, now prevents the business portion of that
place from deriving that benefit from the new opening which they at
first received.
Thoreau thus speaks of what fell under his own observation, during his
last visit to Cape Cod:
“We ourselves observed the effect of a single storm with a high
tide in the night, in July, 1855. It moved the sand on the beach
opposite [Highland] lighthouse to the depth of six feet, and three
rods in width as far as we could see north and south, and carried
it bodily off, no one knows exactly where, laying bare in one place
a rock five feet high, which was invisible before, and narrowing
the beach to that extent. There is usually, as I have said, no
bathing on the back side of the Cape, on account of the undertow,
but when we were there last the sea had three months before cast
up a bar near this lighthouse, two miles long and ten rods wide,
leaving a narrow cove, then a quarter of a mile long, between it
and the shore, which afforded excellent bathing. This cove had
from time to time been closed up as the bar travelled northward,
in one instance imprisoning four or five hundred whiting and cod,
which died there, and the water as often turned fresh, and finally
gave place to sand. This bar, the inhabitants assured us, might be
wholly removed, and the water six feet deep there in two or three
days.”—p. 142.
Along the eastern shores of Eastham and Orleans, the strong current
of the ebb and of a portion of the flood tide sets in a southerly
direction,—the undertow breaking up and carrying with it the sands
from the bottom. On reaching the mouth of the Potanumaquut harbor the
current, setting in, deposits this sand, thus prolonging the northern
point of the entrance-way; but, acting more directly on the southern
point, and aided by the retreating sea at ebb tide, the moving mass
of water must necessarily cut away the southerly bank,—so that the
northern point continually increasing in length and the southern point
shortening, or losing material, the harbor entrance is continually
travelling southward.
When the Sparrow-Hawk grounded for the last time within the northern
point, under the influence of a westerly gale, the sand must have
rapidly accumulated about her, in the manner and from the causes we
have just described. Still there would be, for a considerable time,
shallow waters about her after the sand had filled in the bay nearly
to her deck; and the ends of her timbers which were uppermost show at
this date the rounded form which we should expect to find from a flow
of waves and the attrition of the sands. But the wind is also busy on
the bleak shore of the Cape; the sand is blown inward from the top of
the sea line of cliffs; and in a few years from her first becoming
embedded, she must have been completely submerged. Above and around
her, at length the salt-marsh extended itself; but the place was well
known, and the name of “Old Ship Harbor” then obtained,—nor was this
name forgotten, although all knowledge of the ship itself had faded
from the memory of men.
In further illustration of our subject, we insert an extract from the
Massachusetts Historical Collections, vol. viii. p. 143. Boston: Munroe
& Francis, 1802:—
“Few towns in the county are so well provided with harbors as
Chatham. The first and most important, is on the eastern side of
the town, and is called Old harbour. It is formed by a narrow
beach, which completely guards it against the ocean. The haven on
the western side of this beach is extensive; but the harbour of
Chatham is supposed to reach not farther north than Strong island,
a distance of about four miles. Above that, the water, which is
within the limits of Harwich and Orleans, is known by other names.
The breadth of the harbour, is about three-quarters of a mile. Its
entrance, a quarter of a mile wide, is formed by a point of the
beach and James’ head, east of it on the main land. On the inside
of the beach are flats and salt marsh. There is also a piece of
marsh on the southern part of Strong island. These marshes are
covered during every tide.
“There are no rocks either within or near the harbour; but its
mouth is obstructed by bars, which extend east and southeast of
the point of the beach three quarters of a mile. On each side of
this mouth is a breaker,—one called the North, and the other the
South breaker. There are also several bars in the harbour within
the outer bars. These bars are continually shifting,—the causes
of which are storms and a strong current which sets in and out
of the harbour. At low water, there are seven feet on the outer
bars, common tides rising about six feet. North of them, the shore
is bolder. There is good holding ground in the harbour. At the
entrance, the bottom is sandy. Farther in there is a muddy bottom.
The depth at low water is about twenty feet.
“Not only do the bars alter, but the mouth of the harbour also is
perpetually varying. At present it is gradually moving southward
by the addition of sand to the point of the beach. The beach has
thus been extended above a mile within the course of the past forty
years.
“In the year 1626, there was an entrance into Monamoyick harbour,
opposite Potanumaquut, six miles north of the present mouth. The
ship mentioned by Prince[2] came in here, and was stranded on the
beach, where its ruins were to be seen about twenty years ago.
This part of the beach still bears the name of the Old Ship. The
entrance has been closed for many years. Several passages into
the harbour have been opened and shut since that time. At a late
period, there were two openings into the haven,—one of which, that
which now exists, was styled the Old harbour, and the other, the
New harbour.[3] Though the mouth of the New harbour is entirely
choked up with sand, yet the name, Old harbour, is still retained.
“It is not easy to give directions for sailing into so inconstant
a port. None but a pilot who is well acquainted with its yearly
variations can guide in a vessel with safety. On a signal being
made, however, boats are ready to put off from the shore, to yield
assistance. In a north-east storm, in which a pilot cannot leave
the land, a vessel, by getting to the south of the South breaker,
may, at present, ride with safety. But how long this will be true,
it is impossible to say.”
The following account of a tremendous storm and its effects, is from
the able work of the Rev. FREDERICK FREEMAN,—“History of Cape Cod;
Annals of Barnstable County and of its several towns”:—
“Among the remarkable events of this early period is recorded that
of a violent storm which did great damage, the tide rising twenty
feet perpendicular.” Hubbard and Morton say: “The Narragansets were
obliged to betake themselves to the tops of trees, and yet many of
them were drowned. Many hundred thousand of trees were blown down,
turning up the stronger by the roots, and breaking the high pines
and such like in the midst. Tall young oaks and walnut trees of
good bigness were wound as a withe by it.”
“Governor Bradford’s account of the storm is as follows: ‘In 1635,
August 15, was such a mighty storm of wind and rain as none living
in these parts, either English or Indians, ever saw. It began in
the morning a little before day, and came with great violence,
causing the sea to swell above twenty feet right up, and made many
inhabitants climb into the trees.... It began southeast, and parted
toward the south and east, and veered sundry ways. The wrecks of it
will remain a hundred years. The moon suffered a great eclipse the
second night after it.
“It was in this storm that Mr. Thacher was cast ashore at Cape Ann,
on what was afterward known as Thacher’s Island. Twenty-one persons
were drowned. None were saved but Mr. Anthony Thacher and wife.”