returned for me, and we rowed round the weird little lake. It was
certainly very curious and beautiful; evidently a huge cavity out of
which the calcareous sand had been washed or dissolved, and whose
walls, still to a certain extent permeable, had been hardened and
petrified by the constant percolation of water charged with carbonate
of lime. From the roof innumerable stalactites, perfectly white, often
several yards long and coming down to the delicacy of knitting-needles,
hung in clusters; and wherever there was any continuous crack in the
roof or wall, a graceful, soft-looking curtain of white stalactite
fell, and often ended, much to our surprise. Deep in the water
Stalagmites also rose up in pinnacles and fringes through the water,
which was so exquisitely still and clear that it was something
difficult to tell where the solid marble tracery ended, and its
reflected image began. In this cave, which is a considerable distance
from the sea, there is a slight change of level with the tide
sufficient to keep the water perfectly pure. The mouth of the cave is
overgrown with foliage, and every tree is draped and festooned with
the fragrant _Jasminum gracile_, mingled not unfrequently with the
"poison ivy" (_Rhus toxicodendron_). The Bermudians, especially the
dark people, have a most exaggerated horror of this bush. They imagine
that if one touch it or rub against it he becomes feverish, and is
covered with an eruption. This is no doubt entirely mythical. The
plant is very poisonous, but the perfume of the flower is rather
agreeable, and we constantly plucked and smelt it without its
producing any unpleasant effect. The tide was with us when we regained
the Flats Bridge, and the galley shot down the rapid like an arrow,
the beds of scarlet sponges and the great lazy trepangs showing
perfectly clearly on the bottom at a fathom depth.
[Illustration: FIG. 1. CALCAREOUS CONCRETION SIMULATING A FOSSIL
PALM-STEM, BOAZ ISLAND, BERMUDAS.]
Every here and there throughout the islands there are groups of bodies
of very peculiar form projecting from the surface of the limestone
where it has been weathered. These have usually been regarded as
fossil palmetto stumps, the roots of trees which have been overwhelmed
with sand and whose organic matter has been entirely removed and
replaced by carbonate of lime. Fig. 1 represents one of the most
characteristic of these from a group on the side of the road in Boaz
Island. It is a cylinder a foot in diameter and six inches or so high;
the upper surface forms a shallow depression an inch deep surrounded
by a raised border; the bottom of the cup is even, and pitted over
with small depressions like the marks of rain-drops on sand; the walls
of the cylinder seem to end a few inches below the surface of the
limestone in a rounded boss, and all over this there are round
markings or little cylindrical projections like the origins of
rootlets. The object certainly appears to agree even in every detail
with a fossil palm-root, and as the palmetto is abundant on the
islands and is constantly liable to be destroyed by and ultimately
enveloped in a mass of moving sand, it seemed almost unreasonable to
question its being one. Still something about the look of these things
made me doubt, with General Nelson, whether they were fossil palms, or
indeed whether they were of organic origin at all; and after carefully
examining and pondering over several groups of them, at Boaz Island,
on the shore at Mount Langton, and elsewhere, I finally came to the
conclusion that they were not fossils, but something totally
different.
[Illustration: FIG. 2. CALCAREOUS CONCRETION IN AEOLIAN LIMESTONE,
BERMUDAS.]
[Illustration: FIG. 3. CALCAREOUS CONCRETION IN AEOLIAN LIMESTONE,
BERMUDAS.]
[Illustration: FIG. 4. CALCAREOUS CONCRETION, BERMUDAS.]
[Illustration: FIG. 5. CALCAREOUS CONCRETION IN AEOLIAN LIMESTONE,
BERMUDAS.]
The form given in Fig. 1 is the most characteristic, and probably by
far the most common; but very frequently one of a group of these, one
which is evidently essentially the same as the rest and formed in the
same way, has an oval or an irregular shape (Figs. 2, 3, and 4). In
these we have the same raised border, the same scars on the outside,
the same origins of root-like fibres, and the same pitting of the
bottom of the shallow cup; but their form precludes the possibility of
their being tree-roots. In some cases (Fig. 5), a group of so-called
"palm-stems" is inclosed in a space surrounded by a ridge, and on
examining it closely this outer ridge is found to show the same
leaf-scars and traces of rootlets as the "palm-stems" themselves. In
some cases very irregular honey-combed figures are produced which the
examination of a long series of intermediate forms shows to belong to
the same category (Fig. 6).
[Illustration: FIG. 6. CONCRETIONS IN AEOLIAN ROCKS, BERMUDAS.]
In the caves in the limestone, owing to a thread of water having found
its way in a particular direction through the porous stone of the
roof, a drop falls age after age on one spot on the cave-floor,
accurately directed by the stalactite which it is all the time
creating. The water contains a certain proportion of carbonate of
lime, which is deposited as stalagmite as the water evaporates, and
thus a ring-like crust is produced at a little distance from the spot
where the drop falls. When a ring is once formed, it limits the spread
of the drop, and determines the position of the wall bounding the
little pool made by the drop. The floor of the cave gradually rises by
the accumulation of sand and travertine, and with it rise the walls
and floor of the cup by the deposit of successive layers of stalagmite
produced by the drop percolating into the limestone of the floor which
hardens it still further, but in this peculiar symmetrical way. From
the floor and sides of the cup the water oozes into the softer
limestone around and beneath; but, as in all these limestones, it does
not ooze indiscriminately, but follows certain more free paths. These
become soon lined and finally blocked with stalagmite, and it is
these tubes and threads of stalagmite which afterwards in the
pseudo-fossil represent the diverging rootlets.
[Illustration: A STALAGMITE CAVE.]
Sometimes when two or more drops fall from stalactites close to one
another the cups coalesce (Figs. 2, 3, and 4); sometimes one drop or
two is more frequent than the other, and then we have the form shown
in Figs. 3 and 4; sometimes many drops irregularly scattered form a
large pool with its raised border, and a few drops more frequent and
more constant than the rest grow their "palmetto stems" within its
limit (Fig. 5); and sometimes a number of drops near one another make
a curious regular pattern, with the partitions between the recesses
quite straight (Fig. 6).
I have already referred to the rapid denudation which is going on in
these islands, and to the extent to which they have been denuded
within comparatively recent times. The floors of caves, from their
being cemented into a nearly homogeneous mass by stalagmitic matter,
are much harder than the ordinary porous blown limestone; and it seems
that in many cases, after the rocks forming the walls and roof have
been removed, disintegration has been at all events temporarily
arrested by the floor. Where there is a flat surface of rock exposed
anywhere on the island, it very generally bears traces of having been
at one time the floor of a cave; and as the weather-wearing of the
surface goes on, the old concretionary structures are gradually
brought out again, the parts specially hardened by a localized slow
infiltration of lime resist integration longest and project above the
general surface. Often a surface of weathered rock is so studded with
these symmetrical concretions, that it is hard to believe that one is
not looking at the calcified stumps of a close-growing grove of palms.
[Illustration]
THE BIG TREES OF CALIFORNIA
(FROM STUDIES SCIENTIFIC AND SOCIAL.)
BY ALFRED RUSSEL WALLACE.
[Illustration]
In the popular accounts of these trees it is usual to dwell only on
the dimensions of the very largest known specimens, and sometimes even
to exaggerate these. Even the smaller full-grown trees, however, are
of grand dimensions, varying from fourteen to eighteen feet in
diameter, at six feet above the ground, and keeping nearly the same
thickness for perhaps a hundred feet. In the south Calaveras grove,
where there are more than a thousand trees, the exquisite beauty of
the trunks is well displayed by the numerous specimens in perfect
health and vigor. The bark of these trees, seen at a little distance,
is of a bright orange brown tint, delicately mottled with darker
shades, and with a curious silky or plush-like gloss, which gives them
a richness of color far beyond that of any other conifer. The tree
which was cut down soon after the first discovery of the species, the
stump of which is now covered with a pavilion, is twenty-five feet in
diameter at six feet above the ground, but this is without the thick
bark, which would bring it to twenty-seven feet when alive. A
considerable portion of this tree still lies where it fell, and at one
hundred and thirty feet from the base I found it to be still twelve
and a half feet in diameter (or fourteen feet with the bark), while at
the extremity of the last piece remaining, two hundred and fifteen
feet from its base, it is six feet in diameter, or at least seven feet
with the bark. The height of this tree when it was cut down is not
recorded, but as one of the living trees is more than three hundred
and sixty feet high, it is probable that this giant was not much short
of four hundred feet.
[Illustration: THE "MOTHER OF THE FOREST."]
In the accompanying picture the dead tree in the centre is that from
which the bark was stripped, which was erected in the Crystal Palace
and unfortunately destroyed by fire. It is called the "Mother of the
Forest." The two trees nearer the foreground are healthy, medium-sized
trees, about fifteen feet diameter at six feet above the ground.
The huge decayed trunk called "Father of the Forest," which has fallen
perhaps a century or more, exhibits the grandest dimensions of any
known tree. By measuring its remains, and allowing for the probable
thickness of the bark, it seems to have been about thirty-five feet
diameter near the ground, at ninety feet up fifteen feet, and even at
a height of two hundred and seventy feet, it was nine feet in
diameter. It is within the hollow trunk of this tree that a man on
horse-back can ride--both man and horse being rather small; but the
dimensions undoubtedly show that it was considerably larger than the
"Pavilion tree," and that it carried its huge dimensions to a greater
altitude; and although this does not prove it to have been much
taller, yet it was in all probability more than four hundred feet in
height.
[Illustration]
Very absurd statements are made to visitors as to the antiquity of
these trees, three or four thousand years being usually given as their
age. This is founded on the fact that while many of the large Sequoias
are greatly damaged by fire, the large pines and firs around them are
quite uninjured. As many of these pines are assumed to be near a
thousand years old, the epoch of the "great fire" is supposed to be
earlier still, and as the Sequoias have not outgrown the fire-scars in
all that time, they are supposed to have then arrived at their full
growth. But the simple explanation of these trees alone having
suffered so much from fire is, that their bark is unusually thick,
dry, soft, and fibrous, and it thus catches fire more easily and
burns more readily and for a longer time than that of the other
coniferæ. Forest fires occur continually, and the visible damage done
to these trees has probably all occurred in the present century.
Professor C.B. Bradley, of the University of California, has carefully
counted the rings of annual growth on the stump of the "Pavilion
tree," and found them to be twelve hundred and forty; and after
considering all that has been alleged as to the uncertainty of this
mode of estimating the age of a tree, he believes that in the climate
of California, in the zone of altitude where these trees grow, the
seasons of growth and repose are so strongly marked that the number of
annual rings gives an accurate result.
Other points that have been studied by Professor Bradley are, the
reason why there are so few young trees in the groves, and what is the
cause of the destruction of the old trees. To take the last point
first, these noble trees seem to be singularly free from disease or
from decay due to old age. All the trees that have been cut down are
solid to the heart, and none of the standing trees show any
indications of natural decay. The only apparent cause for their
overthrow is the wind, and by noting the direction of a large number
of fallen trees it is found that the great majority of them lie more
or less towards the south. This is not the direction of the prevalent
winds, but many of the tallest trees lean towards the south, owing to
the increased growth of their topmost branches towards the sun. They
are then acted upon by violent gales, which loosen their roots, and
whatever the direction of the wind that finally overthrows them, they
fall in the direction of the over-balancing top weight. The young
trees grow spiry and perfectly upright, but as soon as they overtop
the surrounding trees and get the full influence of the sun and wind,
the highest branches grow out laterally, killing those beneath their
shade, and thus a dome-shaped top is produced. Taking into
consideration the health and vigor of the largest trees, it seems
probable that, under favorable conditions of shelter from violent
winds, and from a number of trees around them of nearly equal height,
big trees might be produced far surpassing in height and bulk any that
have yet been discovered. It is to be hoped that if any such are found
to exist in the extensive groves of these trees to the south of those
which are alone accessible to tourists, the Californian Government
will take steps to reserve a considerable tract containing them, for
the instruction and delight of future generations.
The scarcity of young Sequoias strikes every visitor, the fact being
that they are only to be found in certain favored spots. These are,
either where the loose débris of leaves and branches which covers the
ground has been cleared away by fire, or on the spots where trees have
been uprooted. Here the young trees grow in abundance, and serve to
replace those that fall. The explanation of this is, that during the
long summer drought the loose surface débris is so dried up that the
roots of the seedling Sequoias perish before they can penetrate the
earth beneath. They require to germinate on the soil itself, and this
they are enabled to do when the earth is turned up by the fall of a
tree, or where a fire has cleared off the débris. They also flourish
under the shade of the huge fallen trunks in hollow places, where
moisture is preserved throughout the summer. Most of the other
conifers of these forests, especially the pines, have much larger
seeds than the Sequoias, and the store of nourishment in these more
bulky seeds enables the young plants to tide over the first summer's
drought. It is clear, therefore, that there are no indications of
natural decay in these forest giants. In every stage of their growth
they are vigorous and healthy, and they have nothing to fear except
from the destroying hand of man.
[Illustration: REDWOOD TREE WITH TRIPLE TRUNK.]
Destruction from this cause is, however, rapidly diminishing both the
giant Sequoia and its near ally the noble redwood (_Sequoia
sempervirens_), a tree which is more beautiful in foliage and in some
other respects more remarkable than its brother species, while there
is reason to believe that under favorable conditions it reaches an
equally phenomenal size. It once covered almost all the coast ranges
of central and northern California, but has been long since cleared
away in the vicinity of San Francisco, and greatly diminished
elsewhere. A grove is preserved for the benefit of tourists near Santa
Cruz, the largest tree being two hundred and ninety-six feet high,
twenty-nine feet diameter at the ground and fifteen feet at six feet
above it. One of these trees having a triple trunk is here figured
from a photograph. Much larger trees, however, exist in the great
forests of this tree in the northern part of the State; but these are
rapidly being destroyed for the timber, which is so good and durable
as to be in great demand. Hence Californians have a saying that the
redwood is too good a tree to live. On the mountains a few miles east
of the Bay of San Francisco, there are a number of patches of young
redwoods, indicating where large trees have been felled, it being a
peculiarity of this tree that it sends up vigorous young plants from
the roots of old ones immediately around the base. Hence in the
forests these trees often stand in groups arranged nearly in a circle,
thus marking out the size of the huge trunks of their parents. It is
from this quality that the tree has been named _sempervirens_, or ever
flourishing. Dr. Gibbons, of Alameda, who has explored all the remains
of the redwood forests in the neighborhood of Oakland, kindly took me
to see the old burnt-out stump of the largest tree he had discovered.
It is situated about fifteen hundred feet above the sea, and is
thirty-four feet in diameter at the ground. This is as large as the
very largest specimens of the _Sequoia gigantea_, but it may have
spread out more at the base and have been somewhat smaller above,
though this is not a special characteristic of the species.
[Illustration]
WHAT IS EVOLUTION?
(FROM THE ATLANTIC MONTHLY, MARCH, '93.)
BY PROFESSOR E.S. HOLDEN.
[Illustration]
I was once trying to tell a boy, a friend of mine, what the scientific
men mean by the long word _Evolution_, and to give him some idea of
the plan of the world. I wanted an illustration of something that had
grown--evolved, developed--from small beginnings up through more and
more complicated forms, till it had reached some very complete form. I
could think of no better example than the railway by which we were
sitting. The trains were running over the very track where a
wagon-road had lately been, and before that a country cart-track, and
before that a bridle-path, and before that again a mere trail for
cattle. So I took the road for an example, and tried to show my boy
how it had grown from little things by slow degrees according to laws;
and if you like, I will try to tell it again.
Just as one can go further and further back, and always find a bird to
be the parent of the egg, and an egg to be the parent of that bird, so
in the history of this road of ours; we may go back and back into the
past, always finding something earlier, which is the cause of the
something later. The earth, the planets, and the sun were all a fiery
mist long ago. And in that mist, and in what came before it, we may
look for the origin of things as they are. But we must begin
somewhere. Let us begin with the landscape as we see it now,--hills,
valleys, streams, mountains, grass,--but with only a single tree.
We will not try to say how the tree came there. At least, we will not
try just yet. When we are through with the story you can say just as
well as I can.
Suppose, then, a single oak-tree stood just on that hillside thousands
and thousands of years ago. Grass was growing everywhere, and flowers,
too. The seeds came with the winds. Year after year the oak-tree bore
its acorns, hundreds and hundreds of them, and they fell on the grass
beneath and rolled down the smooth slopes, and sprouted as best they
could,--most of them uselessly so far as producing trees were
concerned,--but each one did its duty and furnished its green sprout,
and died if it found no nourishment.
All the hundreds of acorns rolled down the slopes, Not one rolled up;
and here was a _law_,--the law of gravitation,--in full activity.
There were scores of other laws active, too; for evolution had gone a
long way when we had an earth fit to be lived on, and hills in their
present shape, and a tree bearing acorns that would reproduce their
kind. But ever since the fiery mist this simple law of gravitation has
been acting, binding the whole universe together, making a
relationship between each clod and every other clod, and forcing
every stone, every acorn, and every rain-drop to move down and not up.
Just as this law operates,--continuously, silently, inexorably,--so
every other law makes itself felt in its own sphere. Gravitation is
simple. The law according to which an acorn makes an oak--and not a
pine-tree is complex. But the laws of Nature are all alike, and if we
understand the simple ones, we can at least partly comprehend the more
complex. They are nothing but fixed habits on a large scale.
So the acorns fell year by year and sprouted; and one out of a
thousand found good soil, and was not wasted, and made a tree. And so
all around (below) the tree with which we started there grew a grove
of oaks like it, in fact its children; and finally the original trees
died, but not without having left successors.
First of all, the green hillside is smooth and untrodden. There is
nothing but grass and flowers, borne there by the winds, which leave
no track. There is no animal life even in this secluded spot save the
birds, and they too leave no track. By and by there comes a hard
winter, or a dearth of food, and a pair of stray squirrels emigrate
from their home in the valley below; and the history of our hill and
its woods begins. Mere chance decides the choice of the particular
oak-tree in which the squirrels make their home. From the foot of this
tree they make excursions here and there for their store of winter
food,--acorns and the like,--and they leave little paths on the
hillside from tree to tree.
The best-marked paths run to the places where there are the most
acorns. A little later on there are more squirrels in the colony,--the
young of the parent pair, and other colonists from the valley. The
little tracks become plainer and plainer.
Later still come other wild animals in search of food,--squirrels will
do. The wild animals do not remain in the colony (there are too few
squirrels, and they are too hard to catch), but they pass through it,
sometimes by day but oftenest by night.
You might think it was perfectly a matter of chance along which path a
bear or a wolf passed, but it was not. He _could_ walk anywhere on the
hillside; and sometimes he would be found far out of the paths that
the squirrels had begun. But usually, when he was in no haste, he took
the easiest path. The easiest one was that which went between the
bushes and not through them; along the hillside and not straight up
it; around the big rocks and not over them. The wolves and bears and
foxes have new and different wants when they come; and they break new
paths to the springs where they drink, to the shade where they lie, to
the hollow trees where the bees swarm and store the wild honey.
But the squirrels were the first surveyors of these tracks. The bears
and wolves are the engineers, who change the early paths to suit their
special convenience.
By and by the Indian hunter comes to follow the wild game. He, too,
takes the easiest trail, the path of least resistance; and he follows
the track to the spring that the deer have made, and he drinks there.
He is an animal as they are, and he satisfies his animal wants
according to the same law that governs them.
After generations of hunters, Indians, and then white men, there comes
a man on horseback looking for a house to live in. He, too, follows
along the easiest paths and stops at the spring; and near by he finds
the place he is looking for. Soon he returns, driving before him herds
of cattle and flocks of sheep, which spread over the grassy glades to
feed. But everywhere they take the easiest place, the old paths, from
the shady tree to the flowing spring. After awhile the hillside is
plainly marked with these sheep trails. You can see them now whenever
you go into the country, on every hillside.
Soon there are neighbors who build their homes in the next valley, and
a good path must be made between the different houses.
A few days' work spent in moving the largest stones, in cutting down
trees, and in levelling off a few steep slopes, makes a trail along
which you can gallop your horse.