It having been reported in Lincolnshire, that a large extent of islets
of moor, situated along its coast, and visible only at the lowest ebbs
of the tide, was chiefly composed of decayed trees, Dr. de Serra,
accompanied by Sir Joseph Banks, proceeded, in the month of September,
1796, to examine their nature and extent. They landed on one of the
largest of these islets, when the ebbs were at the lowest, and found its
exposed surface to be about ninety feet in length, and seventy-five in
width. They were enabled to ascertain, that these islets consist almost
entirely of roots, trunks, branches, and leaves of trees and shrubs,
intermixed with leaves of aquatic plants. The remains of many of the
trees were still standing on their roots; but the trunks of the greater
part of them lay scattered on the ground, in every direction. The bark
of the trees and roots appeared in general as fresh as when they were
growing; in that of the birches particularly, many of which were found,
even the thin silvery membranes of the outer skin were discernible. The
timber of all kinds, on the contrary, was decomposed and soft, in the
greater part of the trees; in some it was firm, especially about the
knots. Sound pieces of timber had been often found by the country
people. In general, the trunks, branches and roots of the decayed trees
were considerably flattened; a phenomenon which has been observed in the
_surtarbrand_, or fossil wood of Iceland, and also in that found near
the lake of Thun, in Switzerland. The soil was chiefly composed of
rotten leaves; and, on being thrown into water, many of these were taken
out in a perfect state.
These islets extended about twelve miles in length, and one in breadth,
opposite the shore of Sutton, at which place, on digging a well, a moor
of the same nature was found under ground, at the depth of sixteen feet,
and, consequently, very nearly on the same level with that which
constitutes the islets. On boring in the fields belonging to the Royal
Society, in the parish of Mablethorpe, to ascertain the cause of the
subterraneous stratum of decayed vegetables, a similar moor was found.
The appearance of these decayed vegetables was found exactly to agree
with that of the moor which was thrown up in Blankney fen, and in other
parts of the east fen of Lincolnshire, in making their embankments;
barks, like those of the birch-tree, being there also abundantly found.
This moor has been traced as far as Peterborough, sixty miles south of
Sutton. On the north side, the moory islets extend as far as Grimsby, on
the south of the mouth of the Humber: and it is a remarkable
circumstance, that in the large tracts of low land which lie on the
south banks of that river, a little above its mouth, there is a
subterraneous stratum of decayed trees and shrubs, exactly resembling
those observed at Sutton. At Axholme isle, a similar stratum extends
over a tract of ten miles in length, by five in breadth. The roots there
also stand in the places where they grew; while the trunks lie
prostrate, amid the roots of aquatic plants and reeds. Little doubt can
be entertained of the moory islets of Sutton being a part of this
extensive subterraneous stratum, which, by some inroad of the sea, has
been there stripped of its covering of soil. The identity of the levels;
that of the species of trees; the roots of these affixed, in both, to
the soil where they grew; and, above all, the flattened shape of the
trunks, branches, and roots, found in the islets, which can only be
accounted for by the heavy pressure of a superinduced stratum, are
sufficient reasons for this opinion. Such a wide-spread assemblage of
vegetable ruins, lying almost in the same level, and that level
generally under the common mark of low water, naturally gives rise to
reflections on the epoch of this destruction, and the agency by which it
was effected.
The original catastrophe which buried this immense forest must have been
of very ancient date; but it is to be suspected, that the inroad of the
sea which uncovered the decayed trees of the islets of Sutton, is
comparatively recent. The state of the leaves, and the timber, and also
the tradition of the country people, concur to strengthen this
suspicion. Leaves and other delicate parts of plants, though they may be
long preserved in a subterraneous situation, can not remain uninjured
when exposed to the action of the waves, and of the air. The inhabitants
of Sutton believe that their parish church once stood on the spot where
the islets now are, and was submerged by the inroads of the sea; that,
at very low water, their ancestors could even discern its ruins; and
that their present church was built to supply the place of that which
was washed away. So many concomitant (though weak) testimonies, render
their report to a certain degree deserving of credit, and lead to a
supposition, that some of the stormy inundations of the North sea, which
in these last centuries have washed away such large tracts of land on
its shores, may have carried away a soil resting on clay, and have
finally uncovered the trees of these moory islets.
Bogs and mosses are little more than lakes filled up with vegetable
matter, usually of aquatic origin. They are to be found not only in
Ireland and Scotland, but also in every northern country, more
especially when thinly peopled. It should be remarked, that Ireland
abounds in springs, which are mostly dry in summer; and that grass and
weeds grow abundantly about these spots. In the winter these springs
swell and run, softening and loosening all the earth about them. Now,
that sward or surface of the earth which consists of the roots of grass,
being lifted up, and made fuzzy or spongy by the water in the winter, is
dried in the spring, and does not fall together, but withers in a tuft.
The new grass which springs through it is again lifted during the
following winter; and thus the spring is still more and more stopped,
and the sward grows thicker and thicker, till at length it makes what is
called a quaking bog. In proportion as it rises and becomes drier, and
as the grass roots and other vegetables become more putrid, together
with the mud and slime of the water, it acquires a blackness, and
becomes what is called a turf bog. When the vegetables rot, it is
considered that the saline particles are in general carried away by the
water, in which they are dissolved; but that the oily or sulphureous
particles remain and float on the water; and it is thus that the turf
acquires its inflammability. The highest mountains of Ireland are, as
well as the plains, covered with bogs, because they abound in springs,
which, on account of a defective population, are not cleared; and thus
they are overrun with bogs. In that country mosses also abound; and the
particular kind which grows in bogs, is remarkable on this account, that
a congeries of its threads, before it is decayed, constitutes the
substance of the light spongy turf, which thus becomes so tough as not
to yield to the spade. This curious substance, in the north of Ireland,
is called _old wives’ tow_, and is not unlike flax. The turf hardens by
degrees, but is still stringy when broken, and at length becomes the red
turf employed as fuel.
The production of the quaking bogs is as follows. When a stream or
spring runs through a flat, it becomes filled with weeds in summer, and
trees fall across and dam it up. During the winter season the water
stagnates more and more every year, until the whole flat is covered. A
coarse kind of grass, peculiar to these bogs, springs up in tufts, the
roots of which are consolidated, and which, in a few years, grow to the
hight of several feet. In the winter the grass rots, and falls with its
seed on the tufts, thus adding to their growth the ensuing spring. The
tops of flags and grass are sometimes interwoven on the surface of the
water, and gradually becoming thicker, cover its surface. On this
covering herbs grow; and by the interweaving of their roots, it is
rendered so strong as to bear a man. Some of these bogs sink, where a
man stands, to a considerable depth, and rise before and behind:
underneath, the water is clear. Even these in time become red bogs; but
may easily be converted into meadow land, by clearing a trench for the
passage of the water.
Sir Hans Sloane, in his account of the bogs of Ireland, published in the
“Philosophical Transactions,” notices a curious fact, namely, that when
the turf-diggers, after having dug out the earth proper to make turf or
peat, reached the bottom, so as to come to the clayey or other soil, by
draining off the water, they met with the roots of fir-trees, with their
stumps standing upright, and their branches spread out on every side
horizontally. This was evidently the place of the growth of these trees,
the branches of the roots of which are in some parts matted, as is seen
in the roots of trees closely planted. Large pieces of wood have been
found, not only in clay-pits, but likewise in quarries or stone-pits, in
the blocks of stone raised out of their strata or layers. The black
spongy mold employed for peat smells strongly of bitumen, or petroleum,
a great proportion of the oil of which is yielded by distillation; so
that, singular as it may appear, not only oil, but a material which may
be used for candles, may be extracted from these peat-bogs in large
quantities; and it has even been proposed that this business should be
carried on on a large scale, with a view to giving prosperity to the
country. In several parts of Ireland a singular phenomenon has been
observed: on horses trampling with their feet on a space of soft ground,
a sudden appearance of light ensued. On the mold, which agreed in color,
lightness, &c., with peat earth, being examined with a microscope, the
light was found to proceed from an abundance of small, semi-transparent,
whitish, live worms which lay in it.
The commissioners appointed by parliament to inquire into the nature and
extent of the bogs of Ireland, and the practicability of draining them,
represent them as occupying thousands of acres, indeed, many square
miles. Their nature and constituent parts are described by them as
consisting of an accumulation of vegetable matter, settling in
successive generations on itself, and converted by the want of
ventilation and motion to a stagnant pool, which first furnished the
elements of life and increase to the plants covering its surface. The
progress of the accumulation may be best conceived by imagining a basin,
or concave reservoir, of a certain extent and depth, formed of clay,
limestone, gravel, &c., through which the water, scantily but constantly
supplied, can not obtain an issue. Undisturbed in this water, a surface
of bog moss grows, decays and putrefies. To this a second generation
succeeds; and this is followed by others, until, at length, the bulk
rises considerably above the level of its bed, forming hillocks of
various hights, shapes and dimensions. The surface of a bog is not level
like a lake, but undulating; and it terminates somewhat abruptly, and
almost perpendicularly. The average hight of the great bogs, above the
level of high-water mark in Dublin harbor, is about two hundred and
fifty feet. Many acres of these bogs have been reclaimed; and the
practicability of draining and cultivating the greater proportion of
them has been pointed out in the reports of the commissioners.
Perthshire, in North Britain, abounds in mosses, the contents of which
are computed to exceed nine thousand acres. The greatest hight of the
moss, above the clay on which it lies, is fourteen feet and a half. Its
surface, when viewed at a distance, seems wholly covered with heath: but
when closely examined, is found to be composed of small tufts of heath,
intermixed with a variety of moss-plants. Here also are found
innumerable trunks of trees, lying along close to their roots, the
latter being still fixed in the clay, as in the natural state.
The irruption of what is called Solway moss has greatly attracted the
public attention; for, although the cause of it is obvious, still the
alteration it produced on the surface of the earth, was more
considerable than any known in Great Britain, as resulting from a
natural cause, since the destruction of Earl Goodwin’s estate. It
happened in the year 1771, after severe rains which had in many places
produced great inundations of the rivers. The following is a concise
description of the spot where this event happened. Along the side of the
river Esk, is a vale, about a mile in breadth, bounded on the south-east
by the river, and on the north-west by a steep bank, about thirty feet
in hight above the level of the vale. From the top of the bank the
ground rises on an easy ascent for about a quarter of a mile, where it
is terminated by the moss, which extends about two miles north and
south, and about a mile and a half east and west, being bounded on the
north-west by the river Sark. It is probable that the solid ground, from
the top of the bank above the vale, was continued in the same direction
under the moss, before its irruption, for a considerable space; for the
moss, at the place where the irruption happened, was inclined toward the
sloping ground. From the edge of the moss there was a gully or hollow,
called by the country people _the gap_, and said to be thirty yards deep
where it entered the vale: down this hollow ran a small rill of water,
which was often dry in summer, not having any other supply but what
filtered from the moss.
The irruption happened, at the head of this gap, on the night of the
sixteenth of November, between the hours of ten and eleven, when all the
neighboring rivers and brooks were prodigiously swollen by the rains. A
large body of the moss was forced, partly by the great fall of rain, and
partly by the springs beneath, into a small beck or burn, which runs
within a few yards of its border to the south-east. By the united
pressure of the water behind it, and of this beck, which was then very
high, it was carried down a narrow glen between two banks about three
hundred feet high, into a wide and spacious plain, over a part of which
it spread with great rapidity. The moss continued for some time to send
off considerable quantities of its substance, which, being borne along
by the torrent, on the back of the first great body, kept it for many
hours in perpetual motion, and drove it still further on. During the
first night, at least four hundred acres of fine arable land were
covered with moss from three to twelve or fifteen feet in depth. Several
houses were destroyed, much corn lost, &c.; but all the inhabitants
escaped. When the waters subsided, the moss also ceased to flow; but two
pretty considerable streams continued to run from the heart of it, and
carried away some pieces of mossy matter to the place where it burst.
They then joined the beck, already mentioned, which with this addition,
resumed its former channel, and with a little assistance from the people
of the neighborhood, made its way to the Esk, through the midst of that
body of moss which obstructed its course. Thus, in a great measure
drained, the new moss fell several feet, and when the fair weather came
on at the end of November, it settled in a firmer and more solid body on
the lands it had overrun. By this inundation about eight hundred acres
of arable ground were overflowed before the moss stopped, and the
habitations of twenty-seven families destroyed.
Tradition has preserved the memory of a similar inundation in another
part of North Britain. At Monteith a moss changed its course in one
night, and covered a great extent of ground. There is also an account in
the “Philosophical Transactions” of a moving moss near Churchtown, in
Lancashire, which greatly alarmed the neighborhood, and was regarded as
a miracle. The moss was observed to rise to a surprising hight, and soon
after to sink as much beneath the level, moving slowly toward the south.