child's mind is confirmed by the theory of the "culture epochs." I can
not discuss here the doctrine of "recapitulation," with its great
truths and its minor exceptions, but it is well known that in a
general way the development of the child, both physical and mental, is
an epitome of the development of the race. If we compare the physical
and mental activities of the modern civilized man with those of the
more primitive member of the race, we may learn what forms of physical
and mental activity are natural in the different periods of child
life. Some of the things which are characteristic of the modern as
contrasted with the primitive man are sedentary habits, manual
dexterities requiring finely co-ordinated movements both of the eyes
and fingers, increasing devotion to written language and books as
contrasted with spoken language, the lessened dependence upon the
memory, the increasing subjectivity of mental life as contrasted with
the purely objective life of the savage, and the increased importance
of reflection, deliberation, and reasoning, with decrease of impulsive
and habitual action. These things, then, we should expect to belong to
the later period of child life, and studied which involve these
activities will not be economically pursued in the elementary school
grades. These laws are wholly overlooked in our traditional school
curriculum. In practice we are saying to the young child: "Man is a
sedentary, reading, writing, thinking, reasoning being, possessing the
power of voluntary attention. I am to educate you to be a man.
Therefore you must learn to sit still, to read, write, think, reason,
and give attention to your work." The child of six or eight years is
therefore given a book or pen, and put into a closely fitting seat and
left to give attention to his work. This is precisely as if the mother
should say to the infant at the beginning of the period of creeping:
"You are a man, not a brute. Men go upright, not on all fours. You
must walk, not creep."
I wish to call especial attention to the fact that it is only late in
the history of the race that language has passed to its written form.
Man is indeed now a reading and writing animal, but only recently has
he become so. It is only since the invention of printing and the wide
dissemination of books, magazines, and newspapers that reading has
become a real determining factor in the life of the people. Even now
the human organism is engaged in adapting itself to the new strain
brought upon the eyes and fingers in reading and writing. We can
understand, therefore, that it will demand a considerable maturity in
the child before he is ready for that which has developed so late in
the history of the race. The language of the child, like that of the
primitive man, is the language of the ear and tongue. The child is a
talking and hearing animal. He is ear-minded. There has been in the
history of civilization a steady development toward the preponderating
use of the higher senses, culminating with the eye. The average adult
civilized man is now strongly eye-minded, but it is necessary to go
back only to the time of the ancient Greeks to find a decided
relative ear-mindedness. Few laboratory researches have been made upon
the relative rapidity of development of the special senses in
children, but such as have been made tend to confirm the indications
of the "culture epochs" theory, and to show that the auditory centers
develop earlier than the visual.
More and more attention is given in our elementary schools to the
subject of language--more, as some think, than the relative importance
of the subject warrants; but without discussing this question, it is
indubitably shown by child psychology that it is the spoken language
which belongs to the elementary school. The ear is the natural medium
of instruction for young children, and all the second-hand knowledge
which it is necessary that the child should receive should come to him
in this way. It should come from the living words of the living
teacher or parent, not through the cold medium of the printed book. In
the elementary school, then, the child may be instructed in language
as it relates to the ear and the tongue, and this is the real
language. He may be taught to speak accurately and elegantly, and he
may be taught to listen and remember. He may study in this way the
best literature of his mother tongue, and get a living sympathetic
knowledge of it, such as can never come through the indirect medium of
the book. Indeed, this language study need not be limited to the
mother tongue. There is no age when a child may with so great economy
of effort gain a lasting knowledge of a foreign language as when he is
from seven to eleven years old.
When the spoken language has been mastered in this way, and when the
child has arrived at the reading and writing age, language in its
written form may be acquired in a very short time, and that which now
fills so many weary years of school life will sink into the position
of comparative insignificance in which it rightfully belongs. Reading
and writing have usurped altogether too much time. In the schools of
to-day there is a worship of the reading book, spelling book, copy
book, and dictionary not rightfully due them. By dropping the study of
letters from the lower grades much needed time may be found for other
timely and important subjects, such as Nature study, morals, history,
oral language, singing, physical training, and play.
One of the greatest goods which would follow the banishing of the book
from the primary and elementary schools would be the cultivation of
better mental habits. Children suffer lasting injury by being left
with a book in their seats and directed to "study" at an age when the
power of voluntary attention has not developed. They then acquire
habits of listlessness and mind-wandering afterward difficult to
overcome. They read over many times that which does not hold their
attention and is not remembered. Lax habits of study are thus
acquired, with the serious incidental result of weakening the
retentive power which depends so much upon interest and concentration.
With the substitution of the oral for the book method, reliance upon
the memory during the memory period will permanently strengthen the
child's power of retention.
The period between the ages of five and ten years is an important one
in the child's life. It is the time when the "let-alone" plan of
education is of most value, for the reason that nearly all our
educational devices beyond the kindergarten are more or less attempts
to make men and women out of children. If the child at this age must
be put into the harness of an educational system, his course of study
will not be impoverished by the omission of reading and writing. To
teach him to speak and to listen, to observe and to remember, to know
something of the world around him, and instinctively to do the right
thing, will furnish more than enough material for the most ambitious
elementary school curriculum.
FOOTNOTE:
[45] See the article on Courses of Study in the Elementary Schools of
the United States, by T. R. Crosswell, Pedagogical Seminary, April,
1897.
SOILS AND FERTILIZERS.[46]
BY CHARLES MINOR BLACKFORD, JR., M. D.
The word "soil" is used in several arts and sciences to denote the
material from which something derives nourishment. The meat broths and
jellies on which bacteria are grown are soils for them, as the earth
of a field is a soil for the ordinary farm crops; but in general we
mean by soils the various mixtures of mineral and organic substances
that make up the surface of the earth.
The object of this paper is to show as briefly as possible the way it
was formed, of what it is composed, the manner in which it nourishes
plants, and the rules that should guide us in replenishing its
nutritious matter when exhausted. So broad a field can be but lightly
touched, and the effort will be to give only hints from which rules
for specific cases may be deduced.
When a sample of ordinary fertile soil is analyzed, it is found to
consist of a number of minerals, of carbon, nitrogen, and phosphorus
in various combinations, water, and certain other ingredients
dependent on the locality. Among the minerals the most important are
potassium, sodium, lime, iron, and silicon, and the history of these
is of the greatest interest.
Scientific students are generally agreed that the surface of the earth
is but a shell inclosing a liquid, or at all events a highly heated
interior. Originally the whole mass was fluid, but the surface has
cooled more rapidly than the interior, and so a firm crust has been
formed. As the central mass cooled, it contracted, and the crust
became wrinkled and folded, as does the skin of an apple as its pulp
dries, and, by this folding, great ridges were thrown up in some
places and vast depressions formed in others. When the crust became
cool enough for water to remain on it, most of the depressions were
filled by it, and the "dry land appeared," not only on the crests of
the ridges, but on the elevated plateaus about them, and thus oceans
and continents were formed.
Had one of us seen the earth at that time he would have been loath to
select it as a residence. Rugged, rocky ranges of precipitous
mountains surrounded by stretches of naked rock made the landscape.
Dense clouds from the tepid oceans dashed against the icy peaks, and
torrents of water rushed back to the sea. Where the slopes permitted,
the glaciers spread over wide areas, for no vegetation checked the
rapid radiation of heat, and night brought bitter cold. The crust
waved and fluctuated over the liquid interior as does thin ice under a
daring skater, and as it fell the sea rushed over the land, only to
flow elsewhere as the depressed area rose again. The freezing and
thawing and the effects of wind and water in time produced a change.
The rocks were riven and broken to powder, their nearly vertical
slopes became less steep, and instead of bare rock the earth showed
dreary morasses and stretches of sand.
Over these marshes vegetation began to thrive. In the sea there lived
then, as now, a teeming population, animal, vegetable, and living
beings that can with difficulty be assigned to either of these
classes. Each of them, however, contained carbon, and many had built
lime, phosphorus, nitrogen, and other valuable substances into their
bodies. Where food was abundant these grew in vast numbers, and though
many are infinitely small singly, their aggregate mass is enormous.
Among the tiny organisms is one called the _Globigerina_, a being so
small as to require a microscope to study it, but in the past, as now,
growing in great numbers in the sea. The animal is soft and jellylike,
but it forms an outside skeleton of shell of carbonate of calcium or
chalk, a structure that protects it living, but entombs it dead. When
death comes, the little _Globigerina_ sinks to the bottom, and its
tiny shell helps to cover the sea floor.
In the days of long ago these lived as now, and when some convulsion
of Nature lifted the bottom of prehistoric seas, the _Globigerina_
ooze was lifted as well, and thus the "limestone" formed. In our land
a bed of this kind extends from Alabama to Newfoundland; thence, as
the "telegraphic plateau," it passes under the Atlantic, rising into
the chalk downs and cliffs of England; then, again dipping under the
sea, it passes through Europe, and finally furnishes the marble
quarries of Greece. Heat, water, and chemical action give a ceaseless
variety to the forms of the limestone, but wherever found it shows the
former seat of an ocean.
As soon as the "ooze" was lifted from below the sea it began to
change. Some has been exposed to heat and has crystallized into
marble, but for our purposes the most interesting changes have been
wrought by water. Chalk, limestone, and marble--for these are
chemically the same--are almost insoluble in pure water. But water is
rarely pure; it dissolves many things, and among them the
carbonic-oxide gas that every fire, every animal, every decaying scrap
of wood is pouring into the atmosphere. The rain, charged with this
gas, dissolves the limestone, but when the gas escapes the lime falls,
as you know happens when "hard" water is boiled, for the heat drives
off the gas. By this solution, however, the lime is scattered widely
through the soil, and is rarely lacking in untilled earth.
Besides lime, phosphorus is necessary in a good soil. This is widely
spread in Nature, but its great reservoir is the ocean, that boundless
mine of wealth. Many marine animals have the power of building it into
their tissues, and the shells of oysters and other mollusks, the bones
of nearly all animals, terrestrial and marine, and parts of other
organisms, are composed of phosphates to a greater or less degree. In
the ceaseless changes of level the primal oyster beds and coral reefs
are raised to the surface or far above it, and the slow action of time
begins to tear down the deposits and spread them wide-cast. Since that
far-off time "in the beginning" no new matter has been put on earth
save the small amounts of the meteorites, and the economy of Nature
can allow not one atom to lie in idleness, but calls on each one to
play its part ceaselessly, "without haste and without rest." A certain
amount of a substance is disseminated through the earth; by rains it
is washed into the streams, and thence to the sea. Here plants or
animals eagerly await it, and by means of them it is again restored to
the land, to begin again its endless round.
The metals most necessary for plant life are potassium, sodium, and
iron; indeed, the very name of the first shows its importance. If the
ashes which contain all the mineral constituents of plants be put in a
vessel and water poured on them, a solution of lye will percolate
through the mass. The word lye is an abbreviation for alkali, and when
chemistry became sufficiently advanced, a metal was discovered in this
lye to which the name potassium--i. e., potash-metal--was given. If
seaweeds be burned and leeched in the same way we can obtain from the
lye another metal, sodium, that is much like potassium, and that is
one of the most widely spread substances on earth as its chloride, or
common salt.
Potassium and sodium enter into the composition of many rocks, and as
these become eroded by weather they are scattered through the soil,
whence their salts are extracted by rootlets and enter into the
formation of vegetable tissue.
Behind these stands iron. The green coloring matter of plants is a
very complex substance known as chlorophyll, the duty of which is to
take carbonic oxide from the air, utilize the carbon, and restore the
oxygen. Iron enters into the composition of chlorophyll, and to it is
due the brown color of dead leaves. This metal is well-nigh universal,
all the reds and browns in soils and rocks being made by it, and so it
is rarely lacking anywhere.
So much for the metals in soils; but, important as they are, plants
can not live on them alone. Among the nonmetallic bodies phosphorus
stands high among essentials, and for it we are indebted to the sea
and the interior of the earth. Many living creatures extract
phosphorus from the sea water--combine it chiefly with lime, and use
the phosphate for making skeletons or shells, as the case may be.
After the death of the possessors the bones or shells sink to the
bottom, as do the _Globigerina_, and in time are either lifted up, as
were the limestones, and form "phosphate beds" like those of Georgia
and Florida, or are dredged up and ground into powder with bones of
land animals.
Much of the matter forced up from the interior of the earth contains
phosphorus; indeed, it is the bane of Southern iron ores; but though
iron masters dread it, farmers welcome it, as the rains and frosts
crumble the phosphatic rocks and add them to the mass of _débris_ that
forms our soil.
Now let us take a test tube and put into it lime, potash, soda, iron,
silicon, or sand, and phosphorus, add to it a grain of corn, and watch
results. Under suitable conditions of warmth and moisture the grain
will sprout, but when the store of food laid up in it is exhausted our
little plant will die. It is obvious that something else is needed for
a soil, and analysis shows that it is nitrogen, the gas that forms
nearly four fifths of our atmosphere--a gas useless, as such, to
animals, but essential to plants. Nitrogen is abundant in Nature.
Besides being nearly four fifths of the air, it forms twenty-two per
cent of nitric acid, forty-five per cent of saltpeter or niter,
eighty-two per cent of ammonia, and about twenty-five per cent of sal
ammoniac. Plants can not use nitrogen in its pure form, but one or
another of these forms will be found in the soil, whence it may be
extracted.
Now we have the chief articles of plant food, and it is necessary to
know how they are to be used. A plant usually consists of two parts,
one that appears above ground, bearing branches, twigs, and leaves,
and another that remains below ground. It is this latter that concerns
us now, and it is worth study. This lower part consists of a number of
twigs called rhizomes, from which proceed a vast number of fine,
threadlike rootlets, and these are the mouths of the plant, through
which it draws nourishment from the earth about it.
Before any living thing can use nourishment from without, it must be
dissolved, and this solution requires much preparation at times. Men,
and other animals with a wide range of food stuffs, effect this by the
secretions of the digestive organs; but most plants have no digestive
apparatus, strictly speaking, and were they supplied with an abundance
of the foods they most need, they would starve unless the food were in
a suitable state for absorption.
The way in which Nature effects this solution is the key to many of
her secrets, and it has been understood only within the past few
years. If we have a piece of meat freshly taken from an animal we find
it firm, coherent, and almost odorless. If it be put into a warm,
moist chamber for a few days a great change comes over it, and it
becomes soft, offensive in odor, and liable to fall to pieces. We say
that it is rotten or putrid. If a bit of it be put under a microscope,
it is seen to be teeming with bacteria, and these are responsible for
the decay. Now, if a specimen of earth be examined, we find that it
contains bacteria, that attack all kinds of organic matter, tearing it
to pieces to get their food, and making many different things out of
what is left. There is one sort of ferment that grows in apple juice
and splits the sugar into alcohol and carbonic acid, forming "hard
cider," and if the fermentation stops at this point the well-known
drink results. However, there is another ferment called "mother of
vinegar" that may get in, and, if so, a different kind of fermentation
is started that forms acetic acid instead of alcohol; or the bacteria
of decomposition may come in and the whole go back to its elements.
There is a wonderful provision of Nature shown in these stages. The
bacteria--the organisms that produce decay--can not live in a strong
sugar solution, but the ferments, like common yeast, can live in it,
and they split the sugar into alcohol, carbonic oxide, and other
things. In these another set can live, and when the first have died of
starvation or from the alcohol they form, the second set step in and
turn the weak alcohol into acetic acid. Acetic acid is a preserving
agent, as our sour pickles show, but if it is not too strong there are
some organisms that can live in it, and the whole process ends in
decay. Now, it should be noticed that each of these organisms paves
the way for the next by converting an unsuitable food stuff into a
suitable one.
This familiar example indicates the lines on which Nature works. It is
the same everywhere, and shows the advantage of specialization, of
allowing some one with peculiar facilities for performing an act to do
that exclusively, that others may profit by his skill. So long as each
man sought and killed his food, cooked his meals, made his own
clothing, weapons, and implements--in a word, lived alone--advance was
impossible. It was only when he who was most skillful with the needle
made garments for the hunter in exchange for a haunch of venison, that
the hunter could practice marksmanship, and the tailor design a new
cut for the mantle with which the warrior might dazzle the daughter of
the arrow maker. It is the same in Nature. Some organisms possess
powers of elaborating certain materials of which others are quick to
avail themselves. Plants can manufacture starch, an article needed by
animals, but of which their own capacity, so far as producing it is
concerned, is very limited, and thus animals find it advantageous to
avail themselves of these stores instead of taxing their own
resources. Similarly, plants need the organic matters of the animal
bodies, and wise agriculture supplies carbon, nitrogen, and other
articles of food in the shape of animal and vegetable refuse. But this
matter requires digestion; it must be made soluble before it can be
absorbed, and but few plants can effect this solution unaided. The
"Venus's flytrap," the sundew, the wonderful "carrion plant," and
others, are equipped with elaborate apparatus by which they are
enabled to capture, kill, and literally digest the insects that supply
them with nitrogeneous food, but these are exceptional cases. Nature
usually employs other agents.
The action of bacteria in causing decay has been said to be in general
similar to fermentation--that it is effected by the bacteria in
seeking their food. If oxygen be abundant, putrefaction occurs; if it
be scant or absent, then fermentation takes place, for the tiny
organisms require oxygen, and, if the air fails them, they pull to
pieces the organic matters near them to obtain it. In doing this they
get the nitrogen into such shape that the plants can use it, and thus
digest their food for them. All organic matter contains carbon,
hydrogen, and oxygen as a general rule, and to these are often united
phosphorus, sulphur, nitrogen, and others, making very complex
arrangements, veritable houses of cards, in fact, only held together
by the strange power of life. When a leaf falls or a bird dies, some
of these combinations are broken, and then the bacteria and other
lowly organisms have full sway, for living matter is impregnable to
all save a few of them. As oxygen or something else is taken out of
the complex molecules, the compound falls to pieces, but as in the
kaleidoscope the bits of colored glass tumble into endless varieties
of symmetrical figures, so do the atoms fall into new combinations. If
the keystone of an arch be removed, the stones fall apart; but atoms,
unlike bricks or stones, can not stand alone as a rule; they must be
united to something, and so, as soon as old associations are
dissolved, new ones are formed. These new ones are those needed by
plants, and thus is plant food digested.
The term "plant food" has been frequently used, and should now be
distinctly explained, for merely stating the chemical elements is not
describing the food. When a physician tells a nurse to feed a patient
he does not order so much carbon, nitrogen, phosphorus, and the like,
but specifies a soup, certain vegetables, and so on, detailing every
particular; and the same should be done for vegetable invalids.
In medical practice a condition is recognized that is called scurvy.
It is not exactly starvation, but is produced by lack of some food
materials usually supplied by fresh vegetables. If scurvy appears at
sea, no amount of meat, bread, cakes, or pastry will stop it;
vegetables, and they only, will stay it. Sometimes a similar condition
prevails among crops: some ingredient in a soil is lacking, and the
others may be supplied indefinitely without giving the desired relief.
To this may be attributed much of the fault found with fertilizers;
for if the soil does not need a particular compound it is useless to
apply it, and an excellent fertilizer is often blamed for not
producing a crop on land already overstocked with it and crying for
something else.
Let us suppose a field on which cotton has been grown for many
successive years until it has become exhausted. Analysis shows that a
crop yielding one hundred pounds of lint to the acre removes from the
soil: