effects have been very remarkable. Many years ago the mouth of the
river having become blocked up with sand, it cut out for itself
its present channel, which conducts it, by a more direct course,
to the sea. In consequence of this, the old town of Findhorn had
changed its situation, from the east to the west side of the
river, and its site has since been covered by the sea. Previous
to this, however, the inhabitants, carrying with them the stones
of their former houses, had removed across the river, and erected
the present village. On the retiring of the tide from the bay,
the river almost disappears, being swallowed up by the sand, and
quick-sands are formed. The effect resulting from the same cause,
the drifting in of the sand is very different at high water. In
consequence of the channel of the river having been filled up, the
bay has increased in breadth. The sand constantly carried down by
the river has formed a bar, which prevents the entrance of large
vessels; and the river, probably owing to its increased breadth,
and this bar depriving it of the impetus acquired in the course
of its descent, is, at spring-tides, unable to force its way into
the sea, when it is made to flow back, and inundate a considerable
extent of carse-land situated at the head of the bay. It was at one
time proposed to render the river navigable by dredging. And it is
proposed to endeavour to save the adjoining carse-land, which is of
the richest quality, from the monthly inundation to which it is at
present subject, by building a wall along the river side.
I venture to suggest, that the plan Nature employs for fettering
down sand should first be imitated, and that seeds of the Arundo
arenaria, Elymus arenarius, and other plants, which grow readily
in sand, should be, from time to time, strewed over the Mavieston
Hills. The seeds of the Arundo arenaria are not always to be had;
but plants might easily be procured in abundance, and be dibbled
into the sand-hills. The circumstance of great accumulations of
sand having of late disappeared from Coubine, has given rise
to the expectation, that the barony is at no distant period to
become again serviceable to man. By cutting off fresh supplies
from Mavieston, this period would be accelerated, and the proposed
improvements rendered comparatively easy.
There is at present little bent on Coubine. It is chiefly confined
to a range of knolls, which forms the southern boundary of the
sand, and protects the adjoining cultivated fields from its
encroachments; and yet, notwithstanding the terrible calamity
the inhabitants of Moray brought upon themselves, by the pulling
of bent, this “bad practice” still prevails; this plant being in
no other district of country which I have visited so generally
employed for thatching cottars’ houses, and other economical
purposes.”
* * * * *
In the Outer Hebrides the effects of the sand-flood are also
considerable, as shewn in the following notice communicated by my
intelligent assistant Mr Macgillivray.
_Sand-Flood in the Hebrides, and other parts of Scotland._
“The bottom of the sea, along the whole west coast of the Outer
Hebrides, from Barray Head to the Butt of the Lewis, appears to
consist of sand. Along the shores of these islands this sand
appears here and there, in patches of several miles, separated
by intervals of rock, of equal or greater extent. In some places
the sandy shores are flat, or very gently sloping, forming what
are here called Fords; in others, behind the beach, there is an
accumulation of sand to the height of from twenty to sixty feet,
formed into hillocks. This sand is constantly drifting; and in
several places islands have been formed by the removal of isthmi.
The parts immediately behind the beach are also liable to be
inundated by the sand; and in this manner most of the islands have
suffered very considerable damage. Those of Pabbay and Berneray in
Harris may be particularised; in the former of which, a tract of
about a mile and a-half long, by half a mile in breadth, has been
converted into a desert of drifting sand; and in the latter a large
plain, that was formerly noted for its fertility, has been entirely
swept away. The sand consists almost entirely of comminuted shells,
apparently of the species which are found in the neighbouring seas.
It is rather coarse in the grain; but, during high winds, by the
rubbing of its particles upon each other, a sort of dust is formed,
which, at a distance, resembles smoke, and which, in the Island
of Berneray, I have seen driven into the sea, to the distance of
upwards of two miles, appearing like a thin white fog. The cure of
sand drift has been attempted in these islands in two different
ways. Mr Alexander Macleod, surgeon of North Uist, is the inventor
of the most efficacious method, which is that of cutting thin
square turfs from the neighbouring pasture grounds, and laying them
down at intervals of some inches. In the course of a very few years
the turfs coalesce, and the stript ground is little the worse; for
the roots remaining in it, a new vegetation rapidly springs up. The
other method was introduced by Mr Macleod of Harris, and tried
extensively upon his estate. It consists of planting small bundles
of Arundo arenaria, at distances of about a foot and a-half. These
take root, and prevent the drifting to a certain degree. But often
vegetation is tardy in establishing itself, and if the turf plan
be not considerably more expensive, it seems preferable, because
it very effectually prevents the drift, and moreover, produces
excellent pasture ground; the former of which indications, the
planting system, does not completely effect, and the latter in a
very imperfect degree.”
We may add, as this subject is a very interesting one, that further
details, in regard to the moving sands of Scotland, will be found,
on consulting the Statistical Account of Scotland, vol. xx. p. 220.
In the Appendix to the Account of the parish of Dyke, vol. xx. p.
228. _et seq._ there is an account of the Sand-Hills of Mavieston,
which overwhelmed the barony of Coubine, as mentioned in Mr Ritchie’s
communication. In vol. xix. p. 622. is a notice of the shifting of
two hills of the Mavieston Range 500 yards in twenty years. In vol.
xxi. p. 207. is a notice of some hundred acres in Duffus’ parish
covered three feet deep by drift sand; fourteen inches accumulating
in one night. In Neill’s Tour in Orkney and Shetland 1804, it is
observed, that, in the neighbourhood of the Castle of Noltland,
in Westra, much havoc has been done by the blowing of the sand.
No measures are there employed for putting a stop to this kind of
devastation. In the 6th volume of the Highland Society’s Transactions
will be found a report of the operations carried on in Harris, and
alluded to in Mr Macgillivray’s communication. And in Dr Walker’s
Account of the Hebrides, and Mr Macdonald’s Work on the Hebrides,
farther details may be seen. In Jameson’s Account of the Shetland
Islands, and in Shirreff and Fleming’s Reports on these islands,
are also facts connected with this devastating agent. We may add,
that Dr Oudney, Major Denham, and Captain Clapperton, have added
to our knowledge of the blowing sands of the African deserts. The
coloured engraving of the sand-hills of the African Desert in Denham,
Oudney and Clapperton’s Narrative, is a striking and interesting
representation of the form of the moving sand-hills of Africa.
_The moving Sands of Africa and their effects are thus described in
the_ Mercure de France _for September 1809, by De Luc_.
The sands of the Lybian desert, he says, driven by the west winds,
have left no lands capable of tillage on any parts of the western
banks of the Nile not sheltered by mountains. The encroachment of
these sands on soils which were formerly inhabited and cultivated is
evidently seen. M. Denon informs us, in the account of his _Travels
in Lower and Upper Egypt_, that summits of the ruins of ancient
cities buried under these sands still appear externally; and that,
but for a ridge of mountains called the _Lybian chain_, which borders
the left bank of the Nile, and forms, in the parts where it rises, a
barrier against the invasion of these sands, the shores of the river,
on that side, would long since have ceased to be habitable. Nothing
can be more melancholy, says this traveller, than to walk over
villages swallowed up by the sand of the desert, to trample under
foot their roofs, to strike against the summits of their minarets,
to reflect that yonder were cultivated fields, that there grew trees,
that here were even the dwellings of men, and that all has vanished.
If, then, our continents were as ancient as has been pretended, no
traces of the habitation of men would appear on any part of the
western bank of the Nile, which is exposed to this scourge of the
sands of the desert. The existence, therefore, of such monuments
attests the successive progress of the encroachments of the sand;
and those parts of the bank, formerly inhabited, will for ever
remain arid and waste. Thus the great population of Egypt, announced
by the vast and numerous ruins of its cities, was in great part
due to a cause of fertility which no longer exists, and to which
sufficient attention has not been given. The sands of the desert
were formerly remote from Egypt; the _Oases_, or habitable spots,
still appearing in the midst of the sands, being the remains of the
soils formerly extending the whole way to the Nile; but these sands,
transported hither by the western winds, have overwhelmed and buried
this extensive tract, and doomed to sterility a land which was once
remarkable for its fruitfulness.
It is therefore not solely to her revolutions and changes of
sovereigns that Egypt owes the loss of her ancient splendour; it is
also to her having been thus irrecoverably deprived of a tract of
land, by which, before the sands of the desert had covered it, and
caused it to disappear, her wants had been abundantly supplied. Now,
if we fix our attention on this fact, and reflect on the consequences
which would have attended it if thousands, or only some hundreds, of
centuries had elapsed since our continents first existed above the
level of the sea, does it not evidently appear that all the country
on the west of the Nile would have been buried under this sand before
the erection of the cities of ancient Egypt, how remote soever that
period may be supposed; and that in a country so long afflicted with
sterility, no idea would even have been formed of constructing such
vast and numerous edifices? When these cities indeed were built,
another cause concurred in favouring their prosperity. The navigation
of the Red Sea was not then attended with any danger on the coasts;
all its ports, now nearly blocked up with _reefs of coral_, had
a safe and easy access; the vessels laden with merchandize and
provisions could enter them and depart without risk of being wrecked
on these shoals, which have risen since that time, and are still
increasing in extent.
The defects of the present government of Egypt, and the discovery of
the passage from Europe to India round the Cape of Good Hope, are
therefore not the only causes of the present state of decline of this
country. If the sands of the desert had not invaded the bordering
lands on the west, if the work of the sea polypi in the Red Sea had
not rendered dangerous the access to its coasts and to its ports, and
even filled up some of the latter, the population of Egypt and the
adjacent countries, together with their product, would alone have
sufficed to maintain them in a state of prosperity and abundance.
But now, though the passage to India by the Cape of Good Hope
should cease to exist, though the political advantages which Egypt
enjoyed during the brilliant period of Thebes and Memphis should
be re-established, she could never again attain the same degree of
splendour.
Thus the reefs of coral which had been raised in the Red Sea on the
east of Egypt, and the sands of the desert which invade it on the
west, concur in attesting this truth: That our continents are not of
a more remote antiquity than has been assigned to them by the sacred
historian in the book of Genesis, from the great era of the deluge.
NOTE H, p. 30.
_Action of the Sea upon Coasts._
The ocean, in its action upon the cliffs and banks situated on the
coast, breaks them down to a greater or less extent, and either
accumulates the debris at their basis in the form of sea beaches
of greater or less magnitude, or by currents carries it away to be
deposited upon other shores, or to give rise to sand-banks near the
coast, which, in the course of time, become united to the land, and
thus secure it from the further action of the sea. These _destroying_
and _forming_ effects of the waters of the ocean are to be observed
all around the coasts of this island; and beautiful examples of such
actions are to be seen on the coasts of Ireland, and in many of the
islands that lie to the west and north of Great Britain. In a paper
read before the Wernerian Natural History Society, Mr Stevenson,
engineer, mentions many facts illustrative of the destroying effects
of the ocean on our coasts.--Thus he informs us that the waters
of the sea are wearing away the land upon both sides of the Frith
of Forth, not only in exposed, but also in sheltered situations,
and the solid strata, as well as the looser alluvial formations,
which owe their origin to the destroying agency of the ocean at a
former period, are again yielding to its action. At Saint Andrew’s,
the famous castle of Cardinal Beaton, which is said originally to
have been some distance from the sea, now almost overhangs it:
From St Andrew’s northward to Eden water and the River Tay, the
coast presents a sandy beach, and is so liable to shift, that it is
difficult to trace the change it may have undergone. It is certain,
however, that, within this last century, the sea has made such an
impression upon the sands of Barray, on the northern side of the
Tay, that the light-houses at the entrance of the river, which were
formerly erected at the southern extremity of Button-ness, have
been from time to time removed about a mile and a quarter further
northward, on account of the wasting and shifting of these sandy
shores, and that the spot on which the outer light-house stood in
the 17th century, is now two or three fathoms under water, and is at
least three quarters of a mile within flood-mark.
NOTE, p. 32.
_On the growth of Coral Islands._
Of all the genera of lithophytes, the madrepore is the most abundant.
It occurs most frequently in tropical countries, and decreases
in number and variety as we approach the poles. It encircles in
prodigious rocks and vast reefs many of the basaltic and other
rocky islands in the South Sea and Indian Ocean, and, by its daily
growth, adds to their magnitude. The coasts of the islands in
the West Indies, also those of the islands on the east coast of
Africa, and the shores and shoals of the Red Sea, are encircled
and incrusted with rocks of coral. Several different tribes of
madrepore contribute to form these coral reefs; but by far the most
abundant are those of the genera carophylla, astrea and meandrina.
These lithophytic animals not only add to the magnitude of land
already existing, but, according to some naturalists, they form whole
islands. Dr Forster, in his Observations made during a Voyage round
the World, gives an account of the formation of these coral islands
in the South Sea.
All the low isles, he says, seem to me to be a production of the
sea, or rather its inhabitants, the polype-like animals forming the
lithophytes. These animalcules raise their habitation gradually
from a small base, always spreading more and more, in proportion as
the structure grows higher. The materials are a kind of lime mixed
with some animal substances. I have seen these large structures in
all stages, and of various extent. Near Turtle Island, we found, at
a few miles distance, and to leeward of it, a considerable large
circular reef, over which the sea broke every where, and no part of
it was above water; it included a large deep lagoon. To the east
and north-east of the Society Isles, are a great many isles, which
in some parts are above water; in others, the elevated parts are
connected by reefs, some of which are dry at low water, and others
are constantly under water. The elevated parts consist of a soil
formed by a sand of shells and coral rocks, mixed with a light black
mould, produced from putrified vegetables, and the dung of sea-fowls;
and are commonly covered by cocoa-nut trees and other shrubs, and
a few antiscorbutic plants. The lower parts have only a few shrubs
and the above plants; others still lower, are washed by the sea at
high-water. All these isles are connected, and include a lagoon in
the middle, which is full of the finest fish; and sometimes there is
an opening, admitting a boat or canoe, in the reef, but I never saw
or heard of an opening that would admit a ship.
The reef, or the first origin of these isles, is formed by the
animalcules inhabiting the lithophytes. They raise their habitation
within a little of the surface of the sea, which gradually throws
shells, weeds, sand, small bits of corals, and other things, on the
tops of these coral rocks, and at last fairly raises them above
water; where the above things continue to be accumulated by the sea,
till by a bird, or by the sea, a few seeds of plants that commonly
grow on the sea-shore, are thrown up, and begin to vegetate; and
by their annual decay and reproduction from seeds, create a little
mould, yearly accumulated by the mixture with sand, increasing the
dry spot on every side; till another sea happens to carry a cocoa-nut
hither, which preserves its vegetative power a long time in the sea,
and therefore will soon begin to grow on this soil; especially as
it thrives equally in all kinds of soil; and thus may all these low
isles have become covered with the finest cocoa-nut trees.
The animalcules forming these reefs want to shelter their habitation
from the impetuosity of the winds, and the power and rage of the
ocean; but as, within the tropics, the winds blow commonly from one
quarter, they, by instinct, endeavour to stretch only a ledge, within
which is a lagoon, which is certainly entirely screened against the
power of both. This, therefore, might account for the method employed
by the animalcules in building only narrow ledges of coral rocks, to
secure in their middle a calm and sheltered place; and this seems to
me to be the most probable cause of the origin of all the Tropical
Low Isles, over the whole South Sea.
That excellent navigator, the late Captain Flinders, gives the
following interesting account of the formation of Coral Islands,
particularly of Half-way Island on the north coast of Terra
Australis[381].
“This little island, or rather the surrounding reef, which is three
or four miles long, affords shelter from the south-east winds;
and being at a moderate day’s run from Murray’s Isles, it forms
a convenient anchorage for the night to a ship passing through
Torres’ Strait: I named it _Half-way Island_. It is scarcely more
than a mile in circumference, but appears to be increasing both in
elevation and extent. At no very distant period of time, it was one
of those banks produced by the washing up of sand and broken coral,
of which most reefs afford instances, and those of Torres’ Strait a
great many. These banks are in different stages of progress: some,
like this, are become islands, but not yet habitable; some are
above high-water mark, but destitute of vegetation; whilst others
are overflowed with every returning tide.
“It seems to me, that, when the animalcules which form the corals
at the bottom of the ocean cease to live, their structures adhere
to each other, by virtue either of the glutinous remains within, or
of some property in salt water; and the interstices being gradually
filled up with sand and broken pieces of coral washed by the sea,
which also adhere, a mass of rock is at length formed. Future races
of these animalcules erect their habitations upon the rising bank,
and die in their turn, to increase, but principally to elevate,
this monument of their wonderful labours. The care taken to work
perpendicularly in the early stages, would mark a surprising
instinct in these diminutive creatures. Their wall of coral,
for the most part, in situations where the winds are constant,
being arrived at the surface, affords a shelter, to leeward of
which their infant colonies may be safely sent forth; and to
this, their instinctive foresight, it seems to be owing, that the
windward side of a reef exposed to the open sea, is generally,
if not always, the highest part, and rises almost perpendicular,
sometimes from the depth of 200, and perhaps many more fathoms. To
be constantly covered with water, seems necessary to the existence
of the animalcules, for they do not work, except in holes upon the
reef, beyond low-water mark; but the coral, sand, and other broken
remnants thrown up by the sea, adhere to the rock, and form a solid
mass with it, as high as the common tides reach. That elevation
surpassed, the future remnants, being rarely covered, lose their
adhesive property; and remaining in a loose state, form what is
usually called a _key_, upon the top of the reef. The new bank is
not long in being visited by sea-birds: salt plants take root upon
it, and a soil begins to be formed; a cocoa-nut, or the drupe of
a pandanus, is thrown on shore; land birds visit it, and deposit
the seeds of shrubs and trees; every high tide, and still more
every gale, adds something to the bank; the form of an island is
gradually assumed; and last of all comes man to take possession.
“Half-way Island is well advanced in the above progressive state;
having been many years, probably some ages, above the reach of
the highest spring tides, or the wash of the surf in the heaviest
gales. I distinguished, however, in the rock which forms its basis,
the sand, coral, and shells, formerly thrown up, in a more or less
perfect state of cohesion. Small pieces of wood, pumice stone, and
other extraneous bodies which chance had mixed with the calcareous
substances when the cohesion began, were inclosed in the rock; and
in some cases were still separable from it without much force. The
upper part of the island is a mixture of the same substances in
a loose state, with a little vegetable soil; and is covered with
the _casuarina_ and a variety of other trees and shrubs, which
give food to parroquets, pigeons, and some other birds; to whose
ancestors, it is probable, the island was originally indebted for
this vegetation.”