Young Folks' Library, Volume XI (of 20) by Various

V >> Various >> Young Folks\' Library, Volume XI (of 20)

Pages:
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23

[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
coniferae. 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 debris 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 debris 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 debris. 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.

Things move fast now,--history begins to be made quickly as soon as
man takes a hand in it. Soon the trail is not enough: it must be
widened so that a wagon-load of boards for a new house can be carried
in (for the settler has found a wife). After the first cart-track is
made to carry the boards and shingles in, a better road will be needed
to haul firewood and grain out (for the wants of the new family have
increased, and things must be bought in the neighboring village with
money, and money can only be had by selling the products of the farm).
By and by the neighborhood is so well inhabited that it is to the
advantage of the villages all around it to have good and safe and easy
roads there; and the road is declared a public one, and it is
regularly kept in repair and improved at the public expense. Do not
forget the squirrels of long ago. They were the projectors of this
road. Their successors use it now,--men and squirrels alike,--and stop
at the spring to drink, and under the huge oaks to rest.

A few years more, and it becomes to the advantage of all to have a
railway through the valley and over the hillside. Then a young
surveyor, just graduated from college, comes with his chain-men and
flag-men, and finds that the squirrels, and bears, and hunters, and
all the rest have picked out the easiest way for him long centuries
ago. He makes his map, and soon the chief enigneer and the president
of the road drive along in a buggy with a pair of fast horses
(frightening the little squirrels off their road-way and into their
holes), and the route of the Bear Valley and Quercus Railway is
finally selected, and here it is. See! there comes a train along the
track. This is the way a railway route grew out of a squirrel path.
There are thousands of little steps, but you can trace them, or
imagine them, as well as I can tell you.

It is the same all over the world. Stanley cut a track through the
endless African forests. But it lay between the Pygmy villages, along
the paths they had made, and through the glades where they fought
their battles with the storks.

Sometimes the first road is a river--the track is already cut. Try to
find out where the settlements in America were in the very early
days--before 1800. You will find them along the Hudson, the Juanita,
the St. Lawrence, the James, the Mississippi Rivers. But when these
are left, men follow the squirrel-tracks and bear-tracks, or the
paths of hunters, or the roads of Roman soldiers. It is a standing
puzzle to little children why all the great rivers flow past the great
towns. (Why do they?) The answer to that question will tell you why
the great battles are fought in the same regions; why Egypt has been
the coveted prize of a dozen different conquerors (it is the gateway
of the East); why our Civil War turned on the possession of the
Mississippi River. It is the roadways we fight for, the ways in and
out, whether they be land or water. Of course, we really fought for
something better than the mere possession of a roadway, but to get
what we fought for we had to have the roadway first.

The great principle at the bottom of everything in Nature is that the
fittest survives: or, as I think it is better to say it, in any
particular conflict or struggle that thing survives which is the
fittest to survive _in this particular struggle_. This is Mr. Darwin's
discovery,--or one of them,--and the struggle for existence is a part
of the great struggle of the whole universe, and the laws of it make
up the methods of Evolution--of Development.

It is clear now, is it not, how the railway route is the direct
descendant of the tiny squirrel track between two oaks? The process of
development we call Evolution, and you can trace it all around you.
Why are your skates shaped in a certain way? Why is your gun rifled?
Why have soldiers two sets of (now) useless buttons on the skirts of
their coats? (I will give you three guesses for this, and the hint
that you must think of cavalry soldiers.) Why are eagles' wings of
just the size that they are? These and millions of like questions are
to be answered by referring to the principle of development.

Sometimes it is hard to find the clew. Sometimes the development has
gone so far, and the final product has become so complex and special,
that it takes a good deal of thinking to find out the real reasons.
But they _can_ be found, whether they relate to a fashion, to one of
the laws of our country, or to the colors on a butterfly's wing.

There is a little piece of verse intended to be comic, which, on the
contrary, is really serious and philosophical, if you understand it.
Learn it by heart, and apply it to all kinds and conditions of things,
and see if it does not help you to explain them to yourself....

"And Man grew a thumb for that he had need of it,
And developed capacities for prey.
For the fastest men caught the most animals,
And the fastest animals got away from the most men.
Whereby all the slow animals were eaten,
And all the slow men starved to death."

[Illustration]

HOW THE SOIL IS MADE

(FROM THE FORMATION OF VEGETABLE MOULD.)

BY CHARLES DARWIN.

[Illustration: W]

Worms have played a more important part in the history of the world
than most persons would at first suppose. In almost all humid
countries they are extraordinarily numerous, and for their size
possess great muscular power. In many parts of England a weight of
more than ten tons (10,516 kilogrammes) of dry earth annually passes
through their bodies and is brought to the surface on each acre of
land; so that the whole superficial bed of vegetable mould passes
through their bodies in the course of every few years. From the
collapsing of the old burrows the mould is in constant though slow
movement, and the particles composing it are thus rubbed together. By
these means fresh surfaces are continually exposed to the action of
the carbonic acid in the soil, and of the humus-acids which appear to
be still more efficient in the decomposition of rocks. The generation
of the humus-acids is probably hastened during the digestion of the
many half-decayed leaves which worms consume. Thus the particles of
earth, forming the superficial mould, are subjected to conditions
eminently favorable for their decomposition and disintegration.
Moreover, the particles of the softer rocks suffer some amount of
mechanical trituration in the muscular gizzards of worms, in which
small stones serve as mill-stones.

[Illustration: DIAGRAM OF THE ALIMENTARY CANAL OF AN EARTH-WORM.]

The finely levigated castings, when brought to the surface in a moist
condition, flow during rainy weather down any moderate slope; and the
smaller particles are washed far down even a gently inclined surface.
Castings when dry often crumble into small pellets and these are apt
to roll down any sloping surface. Where the land is quite level and is
covered with herbage, and where the climate is humid so that much dust
cannot be blown away, it appears at first sight impossible that there
should be any appreciable amount of sub-aerial denudation; but worm
castings are blown, especially while moist and viscid, in one uniform
direction by the prevalent winds which are accompanied by rain. By
these several means the superficial mould is prevented from
accumulating to a great thickness; and a thick bed of mould checks in
many ways the disintegration of the underlying rocks and fragments of
rock.

[Illustration: A WORM CASTING, FROM NICE. (Natural Size.)]

The removal of worm-castings by the above means leads to results which
are far from insignificant. It has been shown that a layer of earth,.2
of an inch in thickness, is in many places annually brought to the
surface per acre; and if a small part of this amount flows, or rolls,
or is washed, even for a short distance, down every inclined surface,
or is repeatedly blown in one direction, a great effect will be
produced in the course of ages. It was found by measurements and
calculations that on a surface with a mean inclination of 9 deg. 26', 2.4
cubic inches of earth which had been ejected by worms crossed, in the
course of a year, a horizontal line one yard in length; so that two
hundred and forty cubic inches would cross a line one hundred yards in
length. This latter amount in a damp state would weigh eleven and
one-half pounds. Thus, a considerable weight of earth is continually
moving down each side of every valley, and will in time reach its bed.
Finally, this earth will be transported by the streams flowing in the
valleys into the ocean, the great receptacle for all matter denuded
from the land. It is known from the amount of sediment annually
delivered into the sea by the Mississippi, that its enormous
drainage-area must on an average be lowered.00263 of an inch each
year; and this would suffice in four and a half million years to lower
the whole drainage-area to the level of the seashore. So that if a
small fraction of the layer of fine earth,.2 of an inch in thickness,
which is annually brought to the surface by worms, is carried away, a
great result cannot fail to be produced within a period which no
geologist considers extremely long.

[Illustration: SECTION THROUGH ONE OF THE DRUIDICAL STONES AT
STONEHENGE, SHOWING HOW MUCH IT HAD SUNK INTO THE GROUND.

(Scale, 1/2 inch to 1 foot.)]

Archaeologists ought to be grateful to worms, as they protect and
preserve for an indefinitely long period every object, not liable to
decay, which is dropped on the surface of the land, by burying it
beneath their castings. Thus, also, many elegant and curious
tesselated pavements and other ancient remains have been preserved;
though no doubt the worms have in these cases been largely aided by
earth washed and blown from the adjoining land, especially when
cultivated. The old tesselated pavements have, however, often suffered
by having subsided unequally from being unequally undermined by the
worms. Even old massive walls may be undermined and subside; and no
building is in this respect safe, unless the foundations lie six or
seven feet beneath the surface, at a depth at which worms cannot work.
It is probable that many monoliths and some old walls have fallen
down from having been undermined by worms.

Pages:
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23