position of leaves.
(3) The story of the sunflower.
Experiments showing use of water to plants:
(1) Place a very much wilted cut plant in water, and note result.
(2) Place seeds in earth which is dry, and in earth which is
kept moist.
(3) Plant seeds on batting floating on a tumbler of water, and note
results.
These experiments should extend over several weeks.
_Winter and spring work._--Begin the study of trees. Choose some tree in
the schoolyard, if possible, and make this the basis of the work. The
following is an outline for the study of a maple tree: Begin
observations in January. Make drawings of the tree, showing the
relations of branches to trunk and general outline. Note the following
details: The color of trunk and branches in January, and the color in
February and March; when the buds begin to swell; the arrangement of
buds; watch closely to determine whether a bud develops into a blossom
or a leaf; the peculiarities of bark on trunk and branches; do the
leaves or the blossoms appear first; the shape and color of the
blossoms; draw them and study them thoroughly; the color and position of
the leaves when they first appear; draw the different stages of the
unfolding of the leaves; keep a calendar of all the year's history of
the tree; when in full leaf make another drawing of the whole tree;
study the tree from below, and if possible from above, to show
arrangement of leaves in reference to light; make drawings of the fruit
when it is formed; study how it travels; when the first autumn tints
appear; make colored drawings of the tree in its autumn foliage, and
note when leaves begin to fall and when the branches are finally bare;
note different form of maple in the open and maple in the forest.
In connection with the year's history of the tree, study the tree from
an economic point of view. Make a special study of sugar-making in
connection with the maple tree. Study maple wood. To do this get a
quarter section of a piece of maple log and study the grain lengthwise
and in cross sections. Study all the industries possible in which maple
is used. Devote one notebook to all the work on the maple tree, and at
the end summarize the observations. For drawing of trees, see Cornell
Teachers' Leaflet, No. 12 (Nos. XXIX and XXX, this volume). Home
Nature-Study, Vol. V, Nos. 2, 5.
FIFTH GRADE.
The work during this grade may be devoted to plant physiology. For this
work use First Studies of Plant Life, Atkinson. The experiments
described in this book are simple and excellent; they give the pupil
definite knowledge of the life processes of plants, and the use to the
plant of roots, stems, leaves, flowers, and fruit.
Continue studies of trees. Select some other species than the one
studied during the last grade. Study it in the same way. Note the
differences between the two. Two or three contrasting species may thus
be studied.
SIXTH GRADE.
Having studied in the previous year the uses of different parts of the
plant, the pupil will be fitted now to take up the general subject of
weeds.
Take some common forms and let the pupils observe that they grow where
other plants do not grow, or that they drive out other plants; then
study the special reasons why each kind of weed is able to do these
things. Botany, Bailey, pp. 214-222; Elements of Botany, pp. 196-205.
During the autumn another subject for study in this grade is
_Mushrooms_. Lead the pupils to see how these flowerless plants produce
seed, and let them bring in as many forms as possible. Do not try to
teach which mushrooms are poisonous. Lessons with Plants, p. 347;
Mushrooms, by Atkinson.
_Winter work._--Evergreen trees. Cornell Teachers' Leaflet, No. 13 (No.
XXXIII, this volume).
_Spring work._--The spring work may well be the making of a calendar for
trees and plants. Keep a record each day of the leafage of plants, the
appearance of weeds, and the appearance of blossoms of fruit trees and
all common flowers. Record which appear first, leaves or blossoms.
This work will be good preparation for the study of the "struggle for
existence," which comes in the next grade.
SEVENTH GRADE.
The work for this year, both fall and spring, may be the study of the
cross fertilization of flowers. Choose a few of the common flowers, and
let the pupils study the means by which pollen is carried from flower to
flower.
In studying any flower fertilized by insects always ask: Where is the
nectary? Where in relation to the nectary are the stigma and the
anthers? What path must the insect follow in order to get the nectar? Do
the flowers attract insects by color? By fragrance? What insects do you
find visiting the flowers studied? Lessons with Plants, pp. 224-245;
Plants, Coulter, pp. 109-137; Elements of Botany, pp. 182-196; Readers
in Botany, Newell, Part II, p. 86; Plant World, Bergen, pp. 57-127; Ten
New England Blossoms, Weed.
The cross fertilization of flowers is only one adaptation for succeeding
in the struggle for existence.
Study as many other ways of insuring the continuance of a plant as is
possible. Botany, Bailey, pp. 197-217; Lessons with Plants, pp. 15-20;
Elements of Botany, pp. 199-212.
Study plant communities. Botany, Bailey, pp. 219-227; Plant Relations,
pp. 146, 162, 168; Plant Structures, p. 313; Cornell Teachers' Leaflet,
No. 19 (No. XXXV, this volume).
EIGHTH GRADE.
It seems to be the experience of most teachers that pupils of the
seventh and eighth grades are with difficulty kept interested in
nature-study. This is probably due to the fact that the methods suited
to earlier grades are not suited to these. Pupils of this age, now
feeling "grown up," are attracted only by more mature work. They may be
interested in some of the following subjects:
_Horticulture and Gardening._--Cornell Teachers' Leaflets.
Garden-Making; The Pruning-Book; The Principles of Fruit-Growing; The
Principles of Vegetable-Gardening, all by Bailey. Plant Culture, by
Goff.
_Forestry._--Relations of forests to preservation of rain-fall and
streams. Preservation of Forests. Use of Forests. Reforesting waste
lands, etc. A Primer of Forestry by Pinchot, United States Department
Agriculture. A First Book of Forestry, Roth.
_Ferns._--Study and make collections of all the ferns of the locality.
Make drawings of each fern and its fruiting organs, and press and mount
the specimens with full accounts of habits and locality of the plant.
How to Know the Ferns, Mrs. Parsons; Gray's Botany; Our Ferns, Clute.
BIBLIOGRAPHY.[7]
[7] This list comprises some of the books that have been helpful to me.
It is not intended to be complete. Good new books are constantly
appearing. The teacher should endeavor to keep up with the new books.
INSECTS.
Every Day Butterflies. S. H. Scudder. Houghton, Mifflin & Co. $2.00.
Insect Life. J. H. Comstock. D. Appleton & Co. $1.25.
Lessons in Nature-Study. Jenkins & Kellogg. W. B. Harrison, $1.00.
Manual for Study of Insects. J. H. Comstock. Comstock Pub. Co. $3.75.
Moths and Butterflies. (a) Julia P. Ballard. Putnam's Sons. $1.50.
Moths and Butterflies. (b) Mary C. Dickerson. Ginn & Co. $2.50.
Stories of Insect Life. Weed & Murtfeldt. Ginn & Co. 35 cents.
Outdoor Studies. James B. Needham. American Book Co. 40 cents.
Bee People. Margaret W. Morley. A. C. McClurg. $1.25.
The Butterfly Book. W. J. Holland. Doubleday, Page & Co. $3.00.
Caterpillars and Their Moths. Eliot and Soule. The Century Co. $2.00.
Wasps and Their Ways. Margaret W. Morley. Dodd, Mead & Co. $1.50.
The Ways of the Six-Footed. Anna Botsford Comstock. Ginn & Co. 40 cents.
How to Know the Butterflies. J. H. and Anna Botsford Comstock. D.
Appleton & Co. $2.25.
ANIMALS OTHER THAN INSECTS.
Animal Life. Jordan & Kellogg. D. Appleton & Co. $1.25.
Familiar Fish. Eugene McCarthy. D. Appleton & Co. $1.50.
Story of the Fishes. James N. Baskett. D. Appleton & Co. 65 cents.
Familiar Life of the Roadside. Schuyler Mathews. D. Appleton & Co.
$1.75.
Squirrels and Other Fur Bearers. John Burroughs. Houghton, Mifflin & Co.
$1.00.
Wild Life in Orchard and Field. Harper & Bros. Wild Neighbors. The
Macmillan Co. Ernest Ingersoll. $1.50 each.
Kindred of the Wild. Roberts. L. C. Page. $2.00.
Wild Life Near Home. Dallas Lore Sharp. The Century Co. $2.00.
Four Footed Americans. Wright. The Macmillan Co. $1.50.
American Animals. Stone & Cram. Doubleday, Page & Co.
$4.00.
Food and Game Fishes. Jordan & Evermann. Doubleday, Page & Co. $4.00.
Various books that deal with animals from the story or narrative point
of view will be found to be interesting and helpful. They are often
useful in arousing an interest in the subject. There are many good
animal books not mentioned in the above list.
Birds.
Bird Homes. A. R. Dugmore. Doubleday, Page & Co. $2.00.
Bird Life (with colored plates). Frank M. Chapman. D. Appleton & Co.
$5.00.
Bird Neighbors. Neltje Blanchan. Doubleday, Page & Co. $2.00.
Birds of Village and Field. Florence Merriam. Houghton, Mifflin & Co.
$2.00.
First Book of Birds. Olive Thorne Miller. Houghton, Mifflin & Co. $1.00.
Second Book of Birds. Olive Thorne Miller. Houghton, Mifflin & Co.
$1.00.
Our Native Birds. D. Lange. The Macmillan Co. $1.00.
Story of the Birds. James N. Baskett. D. Appleton & Co. 65 cents.
How to Attract the Birds. Neltje Blanchan. Doubleday, Page & Co. $1.35.
The Bird Book. Eckstorm. D. C. Heath & Co. 80 cents.
The Relations of Birds to Man. Weed & Dearborn. Lippincott. $2.50.
The Woodpeckers. F. H. Eckstorm. Houghton, Mifflin & Co. $1.00.
Bird Lore. A magazine. The Macmillans. Houghton, Mifflin & Co. $1.00.
PLANT LIFE.
Botany; an Elementary Text for Schools. L. H. Bailey. The Macmillan Co.
$1.00.
Corn Plants. F. L. Sargent. Houghton, Mifflin & Co. 60 cents.
Elements of Botany. J. Y. Bergen. Ginn & Co. $1.10.
Familiar Flowers of Field and Garden. S. Mathews. D. Appleton & Co.
$1.75.
First Studies in Plant Life. George F. Atkinson. Ginn & Co. 70 cents.
Flowers and Their Friends. Margaret W. Morley. Ginn & Co. 60 cents.
Flowers of Field, Hill and Swamp. C. Creevey. Harper & Bros. $2.50.
Glimpses at the Plant World. Fanny D. Bergen. Ginn & Co. 35 cents.
A Guide to the Wild Flowers. Alice Lounsberry. Frederick A. Stokes Co.
$2.50.
How Plants Grow. Asa Gray. American Book Co. 80 cents.
How to Know the Ferns. Mrs. Frances Theodore Parsons. Chas. Scribner's
Sons. $1.50.
Our Ferns in Their Haunts. Clute. Stokes Co. $2.00.
How to Know the Wild Flowers. Mrs. Wm. Starr Dana. Chas. Scribner's
Sons. $2.00.
Lessons With Plants. L. H. Bailey. The Macmillan Co. $1.10.
Little Wanderers. Margaret W. Morley. Ginn & Co. 35 cents.
Mushrooms. George F. Atkinson. Andrus & Church, Ithaca, N. Y. $3.00.
Plants; a text-book of botany. J. M. Coulter. D. Appleton & Co. $2.00.
Plants and Their Children. Mrs. Wm. Starr Dana. American Book Co. 65
cents.
Reader in Botany. J. H. Newell. 2 vols. Ginn & Co. 70 cents.
Seed Dispersal. W. J. Beal. Ginn & Co. 40 cents.
Ten New England Blossoms. Clarence M. Weed. Houghton, Mifflin & Co.
$1.25.
With the Wild Flowers, $1.00; Field, Forest and Wayside Flowers, $1.50.
Maud Going. Baker, Taylor & Co.
Flowers and Their Insect Visitors. Gibson. Newson & Co. $1.00.
TREES.
A Guide to the Trees. Alice Lounsberry. Frederick A. Stokes Co. $2.50.
Familiar Trees and Their Leaves. S. Mathews. D. Appleton & Co. $1.75.
Our Native Trees. Our Native Shrubs. Harriet Keeler. Chas. Scribner's
Sons. $2.00 each.
A Primer of Forestry. Pinchot. U. S. Dept. Agri.
Getting Acquainted with the Trees. J. H. McFarland. Outlook Co. $1.75.
The First Book of Forestry. Roth. Ginn & Co. $1.00.
Among Green Trees. Julia E. Rogers. Mumford. $3.00.
Trees, Shrubs and Vines. Parkhurst. Chas. Scribner's Sons. $1.50.
Practical Forestry. John Gifford. D. Appleton & Co. $1.20.
* * * * *
The Nature-Study Idea. L. H. Bailey. Doubleday, Page & Co. $1.00.
Science Sketches. David Starr Jordan. McClurg & Co. $1.50.
Poetry of the Seasons. Mary I. Lovejoy. Silver, Burdette & Co. 60 cents.
Nature in Verse. Mary I. Lovejoy. Silver, Burdette & Co. 60 cents.
Nature Pictures by American Poets. The Macmillan Co. $1.25.
Arbor Day Manual. Charles Skinner. Bardeen & Co. $2.50.
Songs of Nature. John Burroughs. McClure, Phillips & Co. $1.50.
Among Flowers and Trees. Wait & Leonard. Lee & Shepherd. $2.00.
LEAFLET VI.
A SUMMER SHOWER.[8]
BY R. S. TARR.
[8] Teachers' Leaflet, No. 14: Cornell Nature-Study Bulletin, June,
1899.
[Illustration]
A Rainstorm comes, the walks are wet, the roads are muddy. Then the sun
breaks through the clouds and soon the walks are no longer damp and the
mud of the road is dried. Where did the water come from and where has it
gone? Let us answer these questions.
A kettle on the stove is forgotten and soon a cracking is heard; the
housewife jumps to her feet for the kettle is dry. The kettle was filled
with water, but it has all boiled away; and where has it gone? Surely
into the air of the room, for it can be seen issuing as "steam" and then
disappearing from view, as if by magic. The heat of the fire has changed
the liquid water to a gas as invisible as the air itself. This gas is
_water vapor_.
[Illustration: _Fig. 9. A glass of cold water on which vapor has
condensed in drops._]
Do you wish to prove that the water vapor is there, although unseen?
Then, if the day is cool, watch the window and notice the drops of water
collect upon it. Or, if the day is warm, bring an ice-cold glass or
pitcher into the room and see the drops collect upon it (Fig. 9). People
sometimes say, when drops of water collect on a glass of cold water,
that the glass is "sweating;" but see whether the same thing will not
happen with a cold glass that does not contain water.
These two simple observations teach us two very important facts: (1)
That heat will change liquid water to an invisible vapor, or gas, which
will float about in the air of a room; and (2) that cold will cause some
of the vapor to change back to liquid water.
Let us observe a little further. The clothes upon the line on wash day
are hung out wet and brought in dry. If the sun is shining they probably
dry quickly; but will they not dry even if the sun is not shining? They
will, indeed; so here is another fact to add to our other two, namely
(3) that the production of vapor from water will proceed even when the
water is not heated.
This change of water to vapor is called _evaporation_. The water
evaporates from the clothes; it also evaporates from the walks after a
rain, from the mud of the road, from the brooks, creeks and rivers, and
from ponds, lakes, and the great ocean itself. Indeed, wherever water is
exposed to the air some evaporation is taking place. Yet heat aids
evaporation, as you can prove by taking three dishes of the same kind
and pouring the same amount of water into each, then placing one on the
stove, a second in the sun, and a third in a cool, shady place, as a
cellar, and watching to see which is the last to become dry.
About three-fourths of the earth's surface is covered by water, so that
the air is receiving vapor all the time. In fact, every minute thousands
of barrels of water-vapor are rising into the atmosphere from the
surface of the ocean. The air is constantly moving about, forming winds,
and this load of vapor is, therefore, drifted about by the winds, so
that the air you are breathing may have in it vapor that came from the
ocean hundreds or even thousands of miles away. You do not see the
vapor, you are perhaps not even aware that it is there; yet in a room 10
feet high and 20 feet square there is often enough vapor, if it could
all be changed back to water to fill a two-quart measure.
There is a difference in the amount of vapor from time to time. Some
days the air is quite free from it, and then clothes will dry rapidly.
On other days the air is damp and humid; then people say it is "muggy,"
or that the "humidity is high." On these muggy days in summer the air is
oppressive because there is so much vapor in it. Near the sea, where
there is so much water to evaporate, the air is commonly more humid or
moist than in the interior, away from the sea, where there is less water
to evaporate.
We have seen that there is some vapor in all air, and that there is more
at some times than at others. We have also seen how it has come into the
air, and that cold will cause it to condense to liquid water on cold
window panes and on water glasses. There are other ways in which the
vapor may be changed to liquid.
After a summer day, even when there has been no rain, soon after the
sun sinks behind the western horizon the grass becomes so damp that
one's feet are wet in walking through it. The dew is "falling." During
the daytime the grass is warmed by the sun; but when the sun is gone it
grows cooler, much as a stove becomes cool when the fire is out. This
cool grass chills the air near it and changes some of the vapor to
liquid, which collects in drops on the grass, as the vapor condenses on
the outside of a glass of ice water.
In the opposite season of the year, on a cold winter's day, when you
step out of a warm house into the chilly air, a thin cloud, or fog,
forms as you expel the air from your lungs, and you say that you can
"see your breath." What you really see are the little drops of water
formed as the vapor-laden breath is chilled on passing from the warm
body to the cold air. The vapor is condensed to form a tiny mist.
[Illustration: _Fig. 10. A wreath of fog settled in a valley with the
hilltops rising above it._]
Doubtless you have seen a wreath of fog settling in a valley at night;
or in the morning you may have looked out upon a fog that has gathered
there during the night (Fig. 10). If your home happens to be upon a
hillside, perhaps you have been able to look down upon the fog nestled
there like a cloud on the land, which it really is. Such a fog is caused
in very nearly the same way as the tiny fog made by breathing. The damp
air in the valley has been chilled until the vapor has condensed to form
tiny mist or fog particles. Without doubt you can tell why this fog
disappears when the sun rises and the warm rays fall upon it.
On the ocean there are great fogs, covering the sea for hundreds of
miles; they make sailing dangerous, because the sailors cannot see
through the mist, so that two vessels may run together, or a ship may be
driven upon the coast before the captain knows it. Once more, this is
merely condensed vapor caused by chilling air that has become laden with
vapor. This chilling is often caused when warm, damp winds blow over the
cold parts of the ocean.
This leads the way to an understanding of a rain storm; but first we
must learn something about the temperature of the air. The air near the
ground where we live is commonly warmer than that above the ground where
the clouds are. People who have gone up in balloons tell us so; and now
scientific men who are studying this question are in the habit of
sending up great kites, carrying thermometers and other instruments, in
order to find out about the air far above the ground.
[Illustration: _Fig. 11. Fog clouds among the valleys in the mountains,
only the mountain peaks projecting above them._]
It is not necessary, however, to send up a kite or a balloon to prove
this. If your home is among mountains, or even among high hills, you can
prove it for yourself; for often, in the late autumn, when it rains on
the lower ground, it snows upon the mountain tops, so that when the
clouds have cleared away the surface of the uplands is robed in white
(Fig. 12). In the springtime, or in the winter during a thaw, people
living among these highlands often start out in sleighs on a journey to
a town, which is in the valley, and before they reach the valley their
horses are obliged to drag the sleigh over bare ground. It is so much
warmer on the lower ground that the snow melts away much more quickly
than it does among the hills.
The difference in temperature is, on the average, about one degree for
every three hundred feet, so that a hill top rising twelve hundred feet
above a valley would have an average temperature about four degrees
lower than the valley. Now some mountains, even in New York, rise
thousands of feet above the surrounding country. They rise high into the
regions of cold air, so that they are often covered with snow long
before any snow has fallen on the lowlands; and the snow remains upon
them long after it has disappeared from the lower country (Fig. 12).
[Illustration: _Fig. 12. A mountain whitened by snow on the top, while
there is no snow at the base._]
Some mountains are so lofty that it never rains upon them, but snows
instead; and they are never free from snow, even in mid-summer. If one
climbs to the top of such peaks he finds it always very cold there.
While he is shivering from the cold he can look down upon the green
fields where the birds are singing, the flowers blossoming and the men,
working in the fields, are complaining of the heat.
[Illustration: _Fig. 13. A mountain peak snow capped, and covered on the
very crest by a cloud._]
One who watches such a mountain as this, or in fact any mountain peak,
will notice that it is frequently wrapped in clouds (Fig. 13). Damp
winds blowing against the cold mountains are chilled and the vapor is
condensed. If one climbs through such a cloud, as thousands of people
have done when climbing mountains, he often seems to pass through
nothing but a fog, for really many clouds are only fogs high in the air.
(Fig. 14).
But very often rain falls from these clouds that cling to the mountain
sides. The reason for this is easy to understand. As the air comes
against the cold mountains so much vapor is condensed that some of the
tiny fog particles grow larger and larger until they become mist
particles, which are too heavy to float in the air. They then begin to
settle; and as one particle strikes against another, the two unite, and
this continues until perhaps a dozen have joined together so as to form
a good-sized drop, which is so heavy that it is obliged to fall to the
ground as rain.
[Illustration: _Fig. 14. Clouds clinging to the mountain sides. If one
were climbing these mountains he would find himself, in passing through
the clouds, either in a fog or a mist._]
Let us now look at our summer storms. These do not form about mountain
peaks; yet what has been said about the mountains will help us to
understand such showers.
It is a hot summer day. The air is muggy and oppressive, so that the
least exertion causes a perspiration, and even in the shade one is
uncomfortably hot. Soon great banks of clouds appear (Fig. 15),--the
"thunder heads,"--and people say "a thunder shower is coming, so that we
will soon have relief from this oppressive heat." The clouds draw near,
lightning is seen and thunder heard, and from the black base of the
cloud, torrents of water fall upon the earth. If we could have watched
this cloud from the beginning, and followed it on its course, we would
have seen some facts that would help explain it. Similar clouds perhaps
began to form over your head in the early afternoon and drifted away
toward the east, developing into thunder storms many miles to the east
of you.
On such a day as this, the air near the ground is so damp that it gives
up vapor easily, as you can prove by allowing a glass of ice water to
stand on a table and watching the drops of water gather there, causing
the glass to "sweat" (Fig. 9). The sun beats down upon the heated ground
and the surface becomes like a furnace, so that the air near the ground
is warmed.
[Illustration: _Fig. 15. A "thunder head," or cumulus cloud._]
Air that is warm is lighter than cool air, and, being lighter, will
rise, for the heavy cool air will settle and push it up, as a chip of
wood will rise in a pail of water, because it is lighter than the water
which pushes it to the top. This is why the warm air rises from a
furnace, or a stove, or a lamp. It is the reason why the hot air rises
through a house chimney; undoubtedly you can find other illustrations,
as ventilation, and can find abundant opportunity to prove that warm air
will rise.
The warm, moist air near the ground becomes so light that the
heavy air above settles down and pushes it up, so that an uprising
current of air is formed above the heated ground, much as an
uprising current of hot air rises through the chimney when the
stove is lighted. Rising thousands of feet into the sky the warm
air reaches such a height, and finally comes to a place so cool, that
some of the vapor must be condensed, forming fog particles, which
in turn form a cloud.
On such a day, if you will watch a cloud, you will notice that its base
is flat (Fig. 15); and this flat base marks the height above ground
where the temperature of the atmosphere is low enough to change the
vapor to fog particles. Of course the air still rises somewhat above
this base and continues to get cooler, and to have more and more vapor
condensed. This makes a pile of clouds resting on a level base, but with
rounded tops (Fig. 15). Sometimes the base of these summer clouds,
called cumulus clouds, is a mile above the ground and their tops fully a
mile higher than this.
[Illustration: _Fig. 16. Photograph of a lightning flash._]
Just as on the mountain side, where the drops grow larger until they
must fall, so here, fog particles grow to drops of such a size that they
are too heavy to float. This growth is often aided by the violent
currents of air, which sometimes tumble and toss the clouds about so
that you can see the commotion from the ground. These currents blow one
particle against another, forming a single drop from the collision of
two; then still others are added until the rain drop is so heavy that it
must fall.
But sometimes the air currents are so rapid that the drops are carried
on up, higher and higher, notwithstanding the fact that they are heavy.
Then they may be carried so high, and into air so cold, that they are
frozen, forming hail. These "hailstones" cannot sink to the ground until
they are thrown out of the violent currents, when they fall to the
ground, often near the edge of the storm.
Some hailstones are of great size; you will find it interesting to
examine them. If you do this, notice the rings of clear and clouded ice
that are often to be seen. These are caused when the hail, after
forming, settles to a place where it melts a little, then is lifted
again by another current, growing larger by the addition of more vapor.
This continues until finally the ice ball sinks to the ground.
There is thunder and lightning in such storms. Few things in nature are
grander than these, and those who will watch the lightning flash will
see many beautiful and interesting sights (Fig. 16). Sometimes the flash
goes from cloud to cloud, again from the cloud to the ground. No one
knows exactly why the lightning comes; but we do know that it is an
electric spark, something like that which one can often see pass from
the trolley to the wire of an electric car line. The main difference is
that the spark in a thunder storm is a powerful lightning bolt that
passes over a space of thousands of feet and often does great damage
where it strikes.
The thunder is a sound which may be compared to the crack heard when a
spark passes from the trolley, though of course the noise is very much
louder. The crack of the lightning echoes and reverberates among the
clouds, often changing to a great rumble; but this rumbling is mainly
caused by the echo, the sound from the lightning being a loud crack or
crash like that which we sometimes hear when the lightning strikes near
by.
Some of the vapor of the air, on condensing, gathers on solid objects
like grass, or glass; but some, as fog, floats about in the air. Really
this, too, is often gathered around solid objects. Floating about in the
air are innumerable bits of "dust" which you can see dancing about in
the sunlight when a sunbeam enters a dark room. Some of these "dust"
particles are actual dust from the road, but much of it is something
else, as the pollen of plants, microbes, and the solid bits produced by
the burning of wood or coal.
Each bit serves as a tiny nucleus on which the vapor condenses; and so
the very "dust" in the air aids in the formation of rain by giving
something solid around which the liquid can gather. The great amount of
dust in the air near the great city of London is believed to be one of
the causes for the frequent fogs of that city.
That there is dust in the air, and that the rain removes it, is often
proved when a dull hazy air is changed to a clear, bright air by a
summer shower. Watch to find instances of this. Indeed, after such a
hazy day, when the rain drops first begin to fall, if you will let a few
drops fall upon a sheet of clean white paper, and then dry it, you will
find the paper discolored by the dust that the rain brought with it. So
the rain purifies the air by removing from it the solids that are
floating in it.
These are only a few of the things of interest that you can see for
yourself by studying the air. Watch the sky; it is full of interest. See
what you can observe for yourself. Watch especially the clouds, for they
are not only interesting but beautiful (Fig. 17). Their forms are often
graceful, and they change with such rapidity that you can notice it as
you watch them. Even in the daytime the colors and shadows are
beautiful; but at sunrise and at sunset the clouds are often changed to
gorgeous banks of color.
[Illustration: _Fig. 17. A sky flecked with clouds high in the air._]
Watch the clouds and you will be repaid; look especially for the great
piles of clouds in the east during the summer when the sun is setting
(Fig. 18). Those lofty banks, tinged with silver and gold, and rising
like mountains thousands of feet into the air, are really made of bits
of fog and mist. Among them vapor is still changing to water and rain
drops are forming, while violent currents are whirling the drops about,
and perhaps lifting them to such a height that they are being frozen
into hailstones. Far off to the east, beneath that cloud, rain is
falling in torrents, lightning is flashing and thunder crashing, though
you cannot hear it because it is so far away.
[Illustration: _Fig. 18. The cloud banks of a thunder storm on the
horizon._]
You see the storm merely as a brightly lighted and beautifully colored
cloud mass in the sky; but the people over whom it is hanging find it a
threatening black cloud, the source of a furious wind, a heavy rain, and
the awe-inspiring lightning. To them it may not be beautiful, though
grand in the extreme; and so, too, when the summer thunder shower visits
you in the early evening, you may know that people to the west of you
are probably looking at its side and top and admiring its beauty of form
and color.
The storm passes on, still to the eastward, and finally the cloud mass
entirely disappears beneath the eastern horizon; but if you watch, you
will see signs that it is still there, though out of sight; for in the
darkness of the night you can see the eastern horizon lighted by little
flashes, the source of which cannot be seen. You call it "heat
lightning," but it is really the last signal that we can see of the
vanishing thunder storm, so far away that the sound of the crashing
thunder cannot be heard.
You watch the mysterious flashes; they grow dimmer and dimmer and
finally you see them no more. Our summer shower is gone. It has done
what thousands of others have done before, and what thousands of others
will do in the future. It has started, moved off, and finally
disappeared from sight; and as it has gone it has told us a story. You
can read a part of this story if you will; and in reading it will find
much that interests.
LEAFLET VII.
A SNOW STORM.[9]
BY ANNA BOTSFORD COMSTOCK.
The snow had begun in the gloaming,
And busily all the night
Had been heaping field and highway
With a silence deep and white.
Every pine and fir and hemlock
Wore ermine too dear for an earl,
And the poorest twig on the elm-tree
Was ridged inch deep with pearl.
From sheds new-roofed with Carrara
Came Chanticleer's muffled crow
The stiff rails were softened to swan's-down
And still fluttered down the snow.
--_Lowell._
[9] Home Nature-Study Course, December, 1903.
[Illustration]
The storm which Lowell describes so delightfully is the first soft,
gentle snow fall that comes in November or early December. "The silence
deep and white" settles like a benediction over the brown, uneven
landscape, and makes of it a scene of enchantment. Very different from
this is the storm that comes when the winter cold is most severe and
winter winds most terrific. Then the skies are as white as the fields,
with never a sign of blue; if the sun appears at all, it shines cold
instead of warm, and seems but a vague white spot behind the veil of
upward, downward whirling snowflakes; the wild wind takes the "snow
dust" in eddies across the fields and piles it at the fences in great
drift billows with overhanging crests. On such a day the snow is so cold
and dry, the clouds so low and oppressive, the bare trees so brown and
bleak, that we shiver even though we gaze on the dreary scene from the
window of a warm and comfortable room.
[Illustration: _Fig. 19. Snow crystals enlarged._]
But another change is sure to come. Some February day the wind will veer
suddenly to the south and breathe warm thawing breaths over the white
frozen world. Then will the forests appear in robes of vivid blue-purple
against the shining hills; and in the mornings the soft blue of the
horizon will shade upward into rose-color and still upward into yellow
and beryl green; these hues are never seen on the forest or in the sky
except when the snow covers the earth to the horizon line. The eye that
loves color could ill afford to lose from the world the purples and
blues which bring contrast into the winter landscape.
The snow storm to our limited understanding, begins with a miracle--the
miracle of crystallization. Why should water freezing freely in the air
be a part of geometry, the six rays of the snow crystal growing at an
angle one to another, of sixty degrees? Or as if to prove geometry
divine beyond cavil, sometimes the rays include angles of twice sixty
degrees. Then why should the decorations of the rays assume thousands of
intricate, beautiful forms, each ray of a flake ornamented exactly like
its five sisters? And why should the snowflake formed in the higher
clouds of the upper air be tabular in shape but still, in cross section,
show that it is built on the plan of six radii? Look at it as we will,
the formation of a crystal is a beautiful mystery and is as unfathomable
as is the mystery of life.
[Illustration: _Fig. 20. Snow crystals enlarged._]
I am indebted to the courtesy of Mr. R. G. Allen, Section Director for
New York of the U. S. Weather Bureau, for suggestions in making out the
following questions. The beautiful pictures of snow crystals
illustrating this lesson were made from photographs taken by Mr. W. A.
Bentley of Jericho, Vt. It is our desire to interest all teachers in
the natural history of a snow storm, to the end that "they may love the
country better and be content to live therein."
A thermometer hung in a sheltered, open place away from the warmth of
the house is a necessary preliminary to the proper observation of the
phenomena of a snow storm.
Dark woolen cloth is the best medium on which to catch and observe snow
crystals.
[Illustration: _Fig. 21. "With a silence deep and white."_]
QUESTIONS ON A SNOW STORM.
1. What causes snow?
2. At what temperature do snow crystals form?
3. How do the clouds appear before a snow storm?
4. What is the temperature of the air before the storm?
5. What is the direction of the wind before the storm?
6. Does the storm come from the same direction as the wind?
7. What are the conditions of the wind and temperature when the snow
crystals are most perfect in form?
8. What are these conditions when the snow crystals are matted together
in great flakes?
9. What are these conditions when the snow crystals appear sharp and
needle-like?
10. Are the snow crystals of the same storm similar in structure and
decoration?
11. What is the difference in structure between a snowflake and a hail
stone?
12. What is sleet?
13. What is the difference between hoar frost and snow?
14. Does the temperature rise or fall during a snow storm?
15. Is it colder or warmer after a snow storm has passed than it was
before it began?
16. What are the conditions of weather which cause a blizzard?
17. Why does a covering of snow prevent the ground from freezing so
severely as it would if bare?
18. Why is snow a bad conductor of heat?
19. Pack snow in a quart cup until it is full and let it melt; then tell
how full the cup is of water. What do you infer from this?
20. Have you ever observed the grass to be green beneath snow drifts?
Tell why.
21. Does snow evaporate as well as melt?
22. How does snow benefit the farmer and the fruit grower?
23. Do the snow storms in your locality come from one general direction
all winter?
LEAFLET VIII.
A HANDFUL OF SOIL: WHAT IT IS.[10]
BY R. S. TARR.
[10] Nature-Study Quarterly, No. 2: Leaflet 15.
[Illustration]
Wind drifts a seed from the parent plant until it settles to the ground,
perhaps in a field or by the roadside, or even in the schoolyard. There
it remains through the long winter; but with the return of spring,
encouraged by the warm sunlight, the seed awakens from its dormant
condition, breaks open the seed-cover and sends leaves into the air and
roots into the ground. No one planted the seed; yet the plant has made
its way in the world and it thrives until it has given to other seeds
the same opportunity to start in life.
Had the seed fallen upon a board or a stone it might have sent out
leaves and roots; but it could never have developed into a plant, for
something necessary would have been lacking. What is there in the soil
that is so necessary to the success of plant life? How has it come to be
there? What is this soil that the plants need so much? These are some of
the questions which we will try to answer.
One readily sees that the soil furnishes a place in which the plants may
fix themselves,--an anchorage, as it were. It is also easy to see that
from the soil the plants obtain a supply of water; and, moreover, that
this water is very necessary, for the vegetation in a moist country
suffers greatly in time of drought, and few plants are able to grow in a
desert region because there is so little water. You can make a desert in
the schoolroom and contrast it with moist soil by planting seeds in two
dishes of soil, watering one, but furnishing no water to the other.
That water is necessary to plants is also proved by the plant itself.
The sap and the moisture which may be pressed out of a grass stem or an
apple are principally water taken from the soil by the roots. But there
is more than water, for the juice of an apple is sweet or sour, while
the sap and juice of other plants may be sweet or bitter. There are
substances dissolved in the water.
It is these dissolved substances that the plants need for their growth,
and they find them ready for use in the soil. There is a plant-food
which the roots seek and find, so that every plant which sends roots
into the soil takes something from it to build up the plant tissue. The
sharp edges of some sedges, which will cut the hand like a dull knife,
and the wood ashes left when a wood fire is burned, represent in part
this plant-food obtained from the soil.
Let us take a handful of soil from the field, the schoolyard, or the
street and examine it. We find it to be dirt that "soils" the hands; and
when we try to brush off the dirt, we notice a gritty feeling that is
quite disagreeable. This is due to the bits of mineral in the soil; and
that these are hard, often harder than a pin, may often be proved by
rubbing soil against a piece of glass, which the hard bits will often
scratch, while a pin will not.
[Illustration: _Fig. 21. A boulder-strewn soil of glacial origin with
one of the large erratics on the right similar to those which early
attracted attention to the drift. See page 105._]
Study this soil with the eye and you may not see the tiny bits, though
in sandy soils one may easily notice that there are bits of mineral.
Even fine loamy and clay soils, when examined with a pocket lens or a
microscope, will be found to be composed of tiny fragments of mineral.
It is evident that in some way mineral has been powdered up to form the
soil; and since the minerals come from rocks, it is the rocks that have
been ground up. That powdered rock will make just such a substance as
soil may be proved by pounding a pebble to bits, or by collecting some
of the rock dust that is made when a hole is drilled in a rock. Much the
same substance is ground from a grindstone when a knife is sharpened on
it, making the water muddy like that in a mud hole.
It will be an interesting experiment to reduce a pebble to powder and
plant seeds in it to see whether they will grow as well as in soil; but
in preparing it try to avoid using a sandstone pebble, because sandy
soils are never very fertile.
[Illustration: _Fig. 22. A glacial soil, containing numerous transported
pebbles and boulders, resting on the bed rock._]
Not only is soil made up of bits of powdered rock, but it everywhere
rests upon rock (Fig. 25). Some consider soil to be only the surface
layers in which plants grow; but really this is, in most places,
essentially the same as the layers below, down even to the very rock, so
that we might call it all soil; though, since a special name, _regolith_
(meaning stone blanket), has been proposed for all the soft, soil-like
rock-cover, we may speak of it as regolith and reserve the word soil for
the surface layers only.
In some places there is no soil on the bare rocks; elsewhere the
soil-cover is a foot or two in depth; but there are places where the
regolith is several hundred feet deep. In such places, even the wells do
not reach the bed rock; nor do the streams cut down to it; but even
there, if one should dig deep enough, he would reach the solid rock
beneath.
How has the hard rock been changed to loose soil? One of the ways, of
which there are several, may be easily studied whenever a rock has been
exposed to the air. Let us go to a stone wall or among the pebbles in a
field, for instance, and, chipping off the surface, notice how different
the inside is from the outside. The outer crust is rusted and possibly
quite soft, while the interior is harder and fresher. Many excellent
examples of this may be found in any stony field or stone wall.
[Illustration: _Fig. 23. The bed of a stream at low water, revealing the
rounded pebbles that have been worn and smoothed by being rolled about,
thus grinding off tiny bits which later are built into the
flood-plains._]
As hard iron rusts and crumbles to powder when exposed to the weather;
so will the minerals and the rocks decay and fall to bits; but rocks
require a very much greater time for this than does iron. It happens
that the soil of New York has not been produced by the decay of rock;
and, therefore, although the soils in many parts of the world have been
formed in this way, we will not delay longer in studying this subject
now, nor in considering the exact way in which rocks are enabled to
crumble.
Another way in which rocks may be powdered may be seen in most parts of
New York. The rains wash soil from the hillsides causing the streams to
become muddy. In the streams there are also many pebbles, possibly the
larger fragments that have fallen into the stream after having been
broken from the ledges. The current carries these all along down the
stream, and, as they go, one piece striking against another, or being
dragged over the rocks in the stream bed, the pebbles are ground down
and smoothed (Fig. 23), which means, of course, that more mud is
supplied to the stream, as mud is furnished from a grindstone when a
knife or scythe is being sharpened on it. On the pebbly beaches of the
sea or lakeshore much the same thing may be seen; and here also the
constant grinding of the rocks wears off the edges until the pebbles
become smooth and round.
[Illustration: _Fig. 24. Near view of a cut in glacial soil, gullied by
the rains, and with numerous transported pebbles embedded in the rock
flour._]
Supplied with bits of rock from the soil, or from the grinding up of
pebbles and rocks along its course, the stream carries its load onward,
perhaps to a lake, which it commences to fill, forming a broad delta of
level and fertile land, near where the stream enters the lake. Or,
possibly, the stream enters the sea and builds a delta there, as the
Mississippi river has done.
[Illustration: _Fig. 25. A scratched limestone pebble taken from a
glacial soil._]
But much of the mud does not reach the sea. The greatest supply comes
when the streams are so flooded by heavy rains or melting snows that the
river channel is no longer able to hold the water, which then rises
above the banks, overflowing the surrounding country. Then, since its
current is checked where it is so shallow, the water drops some of its
load of rock bits on the flood-plain, much as the muddy water in a
gutter drops sand or mud on the sidewalk when, in time of heavy rains,
it overflows the walk.
Many of the most fertile lands of the world are flood-plains of this
kind, where sediment, gathered by the streams farther up their courses,
is dropped upon the flood-plains, enriching them by new layers of
fertile soil. One does not need to go to the Nile, the Yellow, or the
Mississippi for illustrations of this; they abound on every hand, and
many thousands of illustrations, great and small, may be found in the
State of New York. Doubtless you can find one.
[Illustration: _Fig. 26. The grooved bed rock scratched by the movement
of the ice sheet over it._]
There are other ways in which soils may be formed; but only one more
will be considered, and that is the way in which most of the soils of
New York have been made. To study this let us go to a cut in the earth,
such as a well or a stream bank (Figs. 22 and 24). Scattered through the
soil numerous pebbles and boulders will doubtless be found; and if these
are compared with the bed rock of the country, which underlies the soil
(Fig. 22), some of them will be found to be quite different from it. For
instance, where the bed rock is shale or limestone, some of the pebbles
will no doubt be granite, sandstone, etc. If you could explore far
enough, you would find just such rocks to the north of you, perhaps one
or two hundred miles away in Canada; or, if your home is south of the
Adirondacks, you might trace the pebbles to those mountains.
On some of these pebbles, especially the softer ones, such as limestone,
you will find scratches, as if they had been ground forcibly together
(Fig. 25). Looking now at the bed rock in some place from which the soil
has been recently removed, you will find it also scratched and grooved
(Fig. 26); and if you take the direction of these scratches with the
compass, you will find that they extend in a general north and south
direction, pointing, in fact, in the same direction from which the
pebbles have come.
All over northeastern North America and northwestern Europe the soil is
of the same nature as that just described. In our own country this kind
of soil reaches down as far as the edge of the shaded area in the map
(Fig. 27), and it will be noticed that all of New York is within that
area excepting the extreme southwestern part near the southern end of
Chautauqua lake.
Not only is the soil peculiar within this district, but there are many
small hills of clay or sand, or sometimes of both together (Figs. 33
and 34). They rise in hummocky form and often have deep pits or
kettle-shaped basins between, sometimes, when the soil is clayey enough
to hold water, containing tiny pools. These hills extend in somewhat
irregular ranges stretching across the country from the east toward the
west. The position of some of these ranges is indicated on the map (Fig.
27).
For a long time people wondered how this soil with its foreign pebbles
and boulders, altogether called "drift," came to be placed where it is;
they were especially puzzled to tell how the large boulders, called
erratics (Fig. 21), should have been carried from one place to another.
It was suggested that they came from the bursting of planets, from
comets, from the explosion of mountains, from floods, and in other ways
equally unlikely; but Louis Agassiz, studying the glaciers of the Alps
and the country round about, was impressed by the resemblance between
the "drift" and the materials carried by living glaciers.
Agassiz, therefore, proposed the hypothesis that glaciers had carried
the drift and left it where we now find it; but for many years his
glacial hypothesis met with a great deal of opposition because it seemed
impossible that the climate could have changed so greatly as to cover
what is now a temperate land with a great sheet of ice. Indeed, even
now, although all who have especially studied the subject are convinced,
many people have not accepted Agassiz's explanation, just as years ago,
long after it was proved that the earth rotated each day, many people
still believed that it was the sun, not the earth, that was moving.
[Illustration: _Fig. 27. Map showing the extent of the ice sheet in the
United States. Position of some of the moraines indicated by the heavily
shaded lines._ (_After Chamberlain._)]
The glacial explanation is as certain as that the earth rotates. For
some reason, which we do not know, the climate changed and allowed ice
to cover temperate lands, as before that time the climate had changed so
as to allow plants like those now growing as far south as Virginia to
live in Greenland, now ice covered. When the ice of the glacier melted
away it left many signs of its presence; and when the temperate latitude
plants grew in Greenland they left seeds, leaves and tree trunks which
have been imbedded in the rocks as fossils. One may now pick the leaves
of temperate climate trees from the rocks beneath a great icecap.
[Illustration: _Fig. 28. A view over the great ice plateau of Greenland,
with a mountain peak projecting above it._]
To one who studies them, the signs left by the glacier are as clear
proof as the leaves and seeds. From these signs we know that the climate
has changed slowly, but we have not yet learned why it changed.
There are now two places on the earth where vast glaciers, or ice
sheets, cover immense areas of land, one in the Antarctic, a region very
little known, the other in Greenland, where there is an ice sheet
covering land having an area more than ten times that of the State of
New York. Let us study this region to see what is being done there, in
order to compare it with what has been done in New York.
[Illustration: _Fig. 29. The edge of a part of the great Greenland ice
sheet (on the left) resting on the land, over which are strewn many
boulders brought by the ice and left there when it melted._]
In the interior is a vast plateau of ice, in places over 10,000 feet
high, a great icy desert (Fig. 28), where absolutely no life of any
kind, either animal or plant, can exist, and where it never rains, but
where the storms bring snow even in the middle of summer. Such must have
been the condition in northeastern America during the glacial period.
[Illustration: _Fig. 30. A scratched pebble taken from the ice of the
Greenland glacier._]
This vast ice sheet is slowly moving outward in all directions from the
elevated center, much as a pile of wax may be made to flow outward by
placing a heavy weight upon the middle. Moving toward the north, east,
south and west, this glacier must of course come to an end somewhere. In
places, usually at the heads of bays, the end is in the sea, as the end
of our glacier must have been off the shores of New England. From these
sea-ends, icebergs constantly break off; these floating away toward the
south, often reach, before they melt, as far as the path followed by the
steamers from the United States to Europe. Between the bays where the
glacier ends in the sea, the ice front rests on the land (Fig. 29), as
it did over the greater part of New York and the states further west.
There it melts in the summer, supplying streams with water and filling
many small ponds and lakes. The front stands there year after year,
sometimes moving a little ahead, again melting further back so as to
reveal the rocks on which it formerly rested.
[Illustration: _Fig. 31. A part of the edge of the Greenland glacier,
with clean white ice above, and dark discolored bands below where laden
with rock fragments. In the foreground is a boulder-strewn moraine._]
The bed rock here is found to be polished, scratched and grooved just
like the bed-rock in New York; and the scratches extend in the direction
from which the ice moves. Resting on the rock are boulders and pebbles
(Fig. 22), sometimes on the bare rock, sometimes imbedded in a clay as
they are in the drift. As we found when studying the soil in our own
region, so here the pebbles are often scratched, and many of them are
quite different from the rock on which they rest.
[Illustration: _Fig. 32. Hummocky surface of the boulder-strewn moraine
of Greenland._]
Going nearer to the ice we find the lower part loaded with pebbles,
boulders and bits of clay very like those on the rocks near by. Fig. 30
shows one of these, scratched and grooved, which I once dug from the ice
of this very glacier. The bottom of the ice is like a huge sandpaper,
being dragged over the bed rock with tremendous force. It carries a
load of rock fragments, and as it moves secures more by grinding or
prying them from the rocks beneath. These all travel on toward the edge
of the ice, being constantly ground finer and finer as wheat is ground
when it goes through the mill. Indeed the resemblance is so close that
the clay produced by this grinding action is often called _rock flour_.
Dragged to the front of the ice, the rock bits, great and small, roll
out as the ice melts, some, especially the finest, being carried away in
the water, which is always muddy with the rock flour it carries; but
much remains near the edge of the ice, forming a _moraine_ (Figs. 31 and
32). This moraine, dumped at the edge of the glacier, very closely
resembles the hummocky hills of New York (Figs. 33 and 34), mentioned
above, which are really moraines formed at the ice-edge during the
glacial period. While their form is quite alike, the New York moraines
are generally less pebbly than the Greenland moraines, because the
Greenland glacier carries less rock flour than did the glacier which
covered New York.
[Illustration: _Fig. 33. A view over the hummocky surface of a part of
the moraine of the great American ice sheet in Central New York._]
In the Greenland glacier, as you can see in Fig. 31, there is much dirt
and rock; in the glacier of the glacial period there was even more. When
it melted away the ice disappeared as water, but the rock fragments of
course fell down upon the rock beneath and formed soil. If over a
certain region, as for instance over your home, the ice carried a great
load of drift, when this gradually settled down, as the ice melted, it
formed a deep layer of soil; but if the glacier had only a small load a
shallow soil was left. Again, if the ice front remained for a long time
near a certain place, as near your home, it kept bringing and dumping
rock fragments to form moraines, which, of course, would continue to
grow higher so long as the ice dumped the rock fragments, much as a sand
pile will continue to grow higher so long as fresh loads are brought and
dumped.
There are other causes for differences in the glacial soils, but most of
them cannot be considered here. One of them is so important, however,
that it must be mentioned. With the melting of so much ice, vast floods
of water were caused, and these came from the ice, perhaps in places
where there are now no streams, or at best only small ones. These rapid
currents carried off much of the rock flour and left the coarser and
heavier sand, gravel, or pebbles, the latter often well rounded, with
the scratches removed by the long-continued rolling about in the glacial
stream bed.
One often finds such beds of sand or gravel in different parts of the
State, telling not only of ice where it is now absent, but of water
currents where is now dry land. The rock flour was in some cases carried
to the sea, elsewhere to lakes, or in still other places deposited in
the flood-plains of the glacier-fed rivers. Now some of this rock flour
is dug out to make into bricks.
Enough has been said to show that the soils of New York were brought by
a glacier, and to point out that there are many differences in thickness
as well as in kind and condition of the soil. The agriculture of the
State is greatly influenced by these differences. In some cases one part
of a farm has a deep, rich soil, another part a barren, sandy, pebbly or
boulder-covered soil (Fig. 21), while in still another part the bed rock
may be so near the surface that it does not pay to clear the forest from
it. Moreover, some farms are in hummocky moraines, while others, near
by, are on level plains (Fig. 34), where a broad glacial stream built up
a flood-plain in a place where now the stream is so small that it never
rises high enough to overflow the plain.
There are even other differences than these, and one who is familiar
with a region is often puzzled to explain them; but they are all due to
the glacier or to the water furnished by its melting, and a careful
study by a student of the subject of Glacial Geology will serve to
explain them. Each place has had peculiar conditions and it would be
necessary to study each place much more carefully than has been done
here in order to explain all the differences.
Not only is agriculture influenced greatly by the differences in the
soil from place to place, but also by the very fact that they are
glacial soils. Being made up of partly ground-up rock fragments the
soils are often stony and difficult to till. Unlike the soil of rock
decay, the particles of which the glacial soil is made have been derived
by mechanical grinding, not by chemical decay and disintegration. There
has been less leaching out of the soluble compounds which make plant
foods. These are stored up in the rock fragments ready for use when
decay causes the proper changes to produce the soluble compounds which
plants require.
[Illustration: _Fig. 34. Hummocky moraine hills in the background and a
level gravel plain--an ancient glacial-stream flood-plain--in
foreground._]
Slowly the glacial soils are decaying, and, as they do so, are
furnishing plant-food to the water which the roots greedily draw in. So
the glacial soil is not a mere store house of plant-food, but a
manufactory of it as well, and glacial soils are therefore "strong" and
last for a long time. That decay is going on, especially near the
surface, may often be seen in a cut in the soil, where the natural blue
color of the drift is seen below, while near the surface the soil is
rusted yellow by the decay of certain minerals which contain iron.
Few materials on the earth are more important than the soil; it acts as
the intermediary between man and the earth. The rocks have some
substances locked up in them which animals need; by decay, or by being
ground up, the rocks crumble so that plants may send roots into them and
extract the substances needed by animals. Gifted with this wonderful
power the plants grow and furnish food to animals, some of which is
plant-food obtained from the rocks; and so the animals of the land, and
man himself, secure a large part of their food from the rocks. It is
then worth the while to stop for a moment and think and study about
this, one of the most marvelous of the many wonderful adjustments of
Nature, but so common that most persons live and die without even giving
it more than a passing thought.
LEAFLET IX.
A HANDFUL OF SOIL: WHAT IT DOES.[11]
BY L. A. CLINTON.
[11] Nature-Study Quarterly, No. 2: Leaflet 15, October, 1899.
[Illustration]
The more one studies the soil, the more certainly it will be found that
the earth has locked up in her bosom many secrets, and that these
secrets will not be given up for the mere asking. As mysterious as the
soil may appear at different times, it always is governed by certain
laws. These principles once understood, the soil becomes an open book
from which one may read quickly and accurately.
USES OF THE SOIL.
The soil has certain offices to perform for which it is admirably
fitted. The most important of these offices are:
1. To hold plants in place;
2. To serve as a source of plant-food;
3. To act as a reservoir for moisture;
4. To serve as a storehouse for applied plant-food or fertilizer.
Some soils are capable of performing all these offices, while others are
fitted for only a part of them. Thus a soil which is pure sand and
almost entirely deficient in the essential elements of plant-food, may
serve, if located near a large city, merely to hold the plants in
position while the skillful gardener feeds the plants with specially
prepared fertilizers, and supplies the moisture by irrigation.
Early in the study of soils an excursion, if possible, should be made
into the woods. Great trees will be seen and under the trees will be
found various shrubs and possibly weeds and grass. It will be noticed
that the soil is well occupied with growing plants. The surface will be
found covered with a layer several inches thick of leaves and twigs.
Beneath this covering the soil is dark, moist, full of organic matter,
loose, easily spaded except as roots or stones may interfere, and has
every appearance of being fertile.
SOIL CONDITIONS AS FOUND IN MANY FIELDS.
After examining the conditions in the forest, a study should be made of
the soil in some cultivated field. It will be found that in the field
the soil has lost many of the marked characteristics noticed in the
woodland. In walking over the field, the soil will be found to be hard
and compact. The surface may be covered with growing plants, for if the
seeds which have been put into the soil by the farmer have not
germinated and the plants made growth, nature has quickly come to the
rescue and filled the soil with other plants which we commonly call
weeds. It is nature's plan to keep the soil covered with growing plants,
and from nature we should learn a lesson. The field soil, instead of
being moist, is dry; instead of being loose and friable, it is hard and
compact, and it appears in texture entirely different from the woodland
soil. The cause of the difference is not hard to discover. In the woods,
nature for years has been building up the soil. The leaves from the
trees fall to the ground and form a covering which prevents washing or
erosion, and these leaves decay and add to the humus, or vegetable
mould, of the soil. Roots are constantly decaying and furnish channels
through the soil and permit the circulation of air and water.
In the field, nature's lesson has been disregarded and too often the
whole aim seems to be to remove everything from the soil and to make no
returns. Consequently the organic matter, or humus, has been used up;
the tramping of the horses' feet has closed the natural drainage canals;
after the crop is removed, the soil is left naked during the winter and
the heavy rains wash and erode the surface, and remove some of the best
plant-food. After a few years of such treatment, the farmer wonders why
the soil will not produce as liberally as it did formerly.
_Experiment No. 1._--The fact that there is humus, or vegetable mould,
in certain soils can be shown by burning. Weigh a potful of hard soil
and a potful of lowland soil, or muck, after each has been thoroughly
dried. Then put the pots on the coals in a coal stove. After the soil is
thoroughly burned, weigh again. Some of the difference in weight may be
due to loss of moisture, but if the samples were well dried in the
beginning, most of the loss will be due to the burning of the humus.
CONDITIONS WHICH AFFECT FERTILITY.
There are certain conditions which affect soil fertility and of these
the most important are:
Texture;
Moisture-content;
Plant-food;
Temperature.
TEXTURE AND ITS RELATION TO FERTILITY.
By texture is meant the physical condition of the soil. Upon good
texture, more than upon any other one thing, depends the productivity of
the soil. When the texture is right the soil is fine, loose, and
friable; the roots are able to push through it and the feeding area is
enlarged. Each individual particle is free to give up a portion of its
plant-food, or its film of moisture. The conditions which are found in
the woods' soil are almost ideal.
_Experiment No. 2._--The importance of good texture may be well shown in
the class room. Pots should be filled with a soil which is lumpy and
cloddy, and other pots with the same kind of material after it has been
made fine and mellow. After seeds are planted in the different pots, a
careful study should be made of the length of time required for
germination and of the health and vigor of the plants.
_Experiment No. 3._--The greater part of our farming lands do not
present ideal conditions as regards texture. Clay soils are especially
likely to be in bad condition. If samples of the various soils can be
collected, as sand, loam, clay, etc., it may be clearly shown how
different soils respond to the same kind of treatment. With a common
garden trowel, the soils should be stirred and worked while wet, and
then put away to dry. After drying, the conditions presented by the
soils should be noted, also the length of time required for the soils to
become dry. Whereas the sand and the loam will remain in fairly good
condition when dry, the clay will have become "puddled," _i. e._, the
particles will have run together and made a hard, compact mass. Thus it
is found in practice that clay soils must be handled with far more care
and intelligence than is required for the sand and loams, if the texture
is to be kept perfect.
_Experiment No. 4._--If, in the experiment above suggested, the clay
soil is mixed with leaf-mould, or humus soil, from the woods, it will
be found to act very differently. The vegetable matter thus mixed with
the mineral matter prevents the running together of the particles of
clay.
Two principles, both important as relating to soil texture, now have
been illustrated. Soils must not be worked when they are so wet that
their particles will cohere, and organic matter, or humus, must be kept
mixed with the mineral matter of the soil. In practical farm operations,
if the soil can be made into a mud ball it is said to be too wet to
work. The required amount of humus is retained in the soil by
occasionally plowing under some green crop, as clover, or by applying
barn manures.
[Illustration: _Fig. 35. The glass of water at the right has received
lime and the clay has been flocculated; the other was not treated._]
Clay soils are also frequently treated with lime to cause them to remain
in good condition and be more easily tilled. Lime causes the fine
particles to flocculate, or to become granular, _i. e._, several
particles unite to form a larger particle, and these combinations are
more stable and do not so readily puddle, or run together. A mud-puddle
in clay soil will remain murky until the water has evaporated entirely.
Let a little water-slaked lime be mixed with the muddy water, and the
particles of clay will be flocculated and will settle to the bottom;
thus the water will become clear.
_Experiment No. 5._--Into two glasses of water put some fine clay soil;
thoroughly stir the mixture (Fig. 35). Into one glass thus prepared put
a spoonful of water-slaked lime; stir thoroughly, then allow both
glasses to remain quiet that the soil may settle. Notice in which glass
the water first becomes clear, and note the appearance of the sediment
in each.
THE MOISTURE IN THE SOIL.
In Leaflet VI has been given the history of a thunder shower. We are not
told much about the history of the water after it reaches the earth. If
we go out immediately after a heavy shower, we find little streams
running alongside the road. These little streams unite to make larger
ones, until finally the creeks and rivers are swollen, and, if the rain
was heavy enough, the streams may overflow their banks. In all these
streams, from the smallest to the largest, the water is muddy. Where did
this mud come from? It was washed largely from the cultivated fields,
and the finest and best soil is certain to be the first to start on its
voyage to the valleys or to the sea. If the farmer had only learned
better the lesson from nature and kept his fields covered with plants, a
large part of the loss might have been prevented. A rain gauge should be
kept in every school yard, so that every shower can be measured. It can
then be easily determined by the pupils how many tons of rain fall upon
the school grounds, or how much falls upon an acre of land. It will be a
matter of surprise that the amount is so great.
[Illustration: _Fig. 36. a. Soil too dry. b. Soil in good condition. c.
Soil too wet._]
Not all the water which falls during a summer shower is carried off by
surface drainage, since a considerable part sinks into the soil. As it
passes down, each soil grain takes up a portion and surrounds itself
with a little film of water, much as does a marble when dipped into
water. If the rain continues long enough, the soil will become saturated
and the water which cannot be retained, will, under the influence of
gravity, sink down to the lower layers of soil until it finally reaches
the level of the free water. From this free water, at varying depths in
the soil, wells and springs are supplied. If the soil were to remain
long saturated, seeds would not germinate, and most cultivated plants
would not grow because all the air passages of the soil would be filled
with water (Fig. 36). The water which sinks down deep into the soil and
helps to supply our wells is called free water. That part which is held
as a film by the soil particles (as on a marble) is called capillary
water. After the rain is over and the sun shines, a part of the moisture
which is held by the particles near the surface is lost by evaporation.
The moisture which is below tends to rise to restore the equilibrium;
thus there is created a current toward the surface, and finally into the
air; the moisture which thus escapes aids in forming the next thunder
storm.
_Experiment No. 6._--Humus enables the soil to take up and hold large
quantities of water. To illustrate this, two samples of soil should be
obtained, one a humus, or alluvial, soil, rich in organic matter, and
the other a sandy soil. Put the two samples where they will become
thoroughly air dry. Procure, say five pounds each of the dry soils, and
put each into a glass tube over one end of which there is tied a piece
of muslin, or fine wire gauze. From a graduated glass pour water slowly
upon each sample until the water begins to drain from the bottom of the
tube. In this way it can be shown which soil has the greater power of
holding moisture. Both samples should then be set away to dry. By
weighing the samples each day, it can be determined which soil has the
greater power of retaining moisture. This experiment may be conducted
not only with sand and humus, but with clay, loam, gravel, and all other
kinds of soil.
_Experiment No. 7._--A finely pulverized soil will hold more
film-moisture than a cloddy soil. To illustrate the importance of
texture as related to moisture, soil should be secured which is cloddy,
or lumpy. One tube should be filled, as heretofore described (Exp. No.
6), with the lumpy soil, and the other tube with the fine soil which
results from pulverizing the lumps, equal weights of soil being used in
each case. From a graduated glass pour water upon each sample until the
drainage begins from the bottom. Notice which soil possesses greater
power of absorbing moisture. Put the samples away to dry, and by careful
weighing, each day, it can be determined which soil dries out more
readily.
[Illustration: _Fig. 37. "Foot-prints on the sands of time."_]
[Illustration: _Fig. 38. A cross section through one of the
foot-prints._]
The prudent farmer will take measures to prevent the escape of this
moisture into the air. All the film-moisture (on the soil particles)
needs to be carefully conserved or saved, for the plants will need very
large amounts of moisture before they mature, and they can draw their
supply only from this film-moisture. We can again apply the lesson
learned in the woods. The soil there is always moist; the leaves form a
cover, or blanket, which prevents the evaporation of moisture.
Underneath an old plank or board, the soil will be found moist. If we
can break the connection between the soil and the air, we can check the
escape of moisture. A layer of straw over the soil will serve to prevent
the loss of moisture; yet a whole field cannot be thus covered. It has
been found that the surface soil, if kept loose, say about three inches
of the top soil can be made to act as a blanket or covering for the soil
underneath. Although this top layer may become as dry as dust, yet it
prevents the escape, by evaporation, of moisture from below. It is a
matter of common observation that if tracks are made across a freshly
cultivated field, the soil where the tracks are will become darker (Fig.
37). This darker appearance of the soil in the foot-marks is due to the
moisture which is there rising to the surface. The implement of tillage
makes the soil loose, breaking the capillary connection between the
lower layers of soil and the surface; thus the upward passage of the
water is checked. Where the foot-print is, the soil has been again
pressed down at the surface, the particles have been crowded closer
together, and capillarity is restored to the surface so that the
moisture is free to escape (Fig. 38). In caring for flower-beds, or even
in growing plants in a pot in the school-room, it is important that the
surface of the soil be kept loose and mellow. Far better in a flower
garden is a garden rake than a watering pot.
_Experiment No. 8._--To show the importance of the surface mulch, fill
several pots with a sandy loam soil, putting the same weight of soil
into each pot. In one pot, pack the soil firmly; in another pot, pack
the soil firmly and then make the surface loose. These pots of soil may
then be put away to dry; by daily weighing each it can be readily
determined what effects the various methods of treatment have upon the
moisture-holding power of soils.
_Experiment No. 9._--The above experiment may be varied by covering the
soil in some of the pots with leaves, or straw, or paper, care being
taken that the added weight of the foreign matter is properly accounted
for.
SOIL TEMPERATURE.
[Illustration: _Fig. 39. The moss-grown lawn or grass plot._]
If a kernel of corn be placed in the ground in early spring before the
soil has become warm, the seed will not germinate. Abundance of moisture
and oxygen may be present, but the third requisite for germination,
proper temperature, is lacking. The soil is very slow to become warm in
the spring, and this is due to the large amount of water which must be
evaporated. During the winter and spring, the rain and melting snow have
saturated the soil. The under-drainage is deficient so there is no way
for the escape of the surplus water except by evaporation, and
evaporation is a cooling process. A well-drained soil is thus warmer
than a poorly-drained one.
The atmosphere is much quicker to respond to changes in temperature than
is the soil. In the spring, the air becomes warm while the soil
continues cold, and the rains which fall during this time are warmed by
passing through the warm air. Then in sinking through the soil the
rain-water parts with some of its heat which makes the soil warmer.
During mid-summer the soil becomes very warm, and it is not affected by
cool nights, as is the atmosphere. Consequently as a summer rain may be
several degrees cooler than the soil, the water in passing through the
soil takes up some of the heat; thus the soil conditions are made more
favorable for plant growth. Therefore, soil temperature is regulated
somewhat by the rainfall.
_Experiment No. 10._--The color of a soil also affects its temperature,
a dark soil being warmer than a light colored soil. By having
thermometers as a part of the school room equipment, interesting
experiments may be conducted in determining the effect of color and
moisture upon the temperature of soils.
AIR IN THE SOIL.
Although that part of the plant which we can see is entirely surrounded
by air, it is also necessary that the soil be in such a condition that
it can be penetrated by the air. Indeed, growth cannot begin in a soil
from which the air is excluded.
[Illustration: _Fig. 40. The clover roots penetrate the soil deeply._]
_Experiment No. 11._--To prove this, put clay soil in a pot and plant
seeds; then wet the surface of the soil and puddle or pack the clay
while wet and watch for the seeds to germinate and grow. At the same
time put seeds in another pot filled with loose, mellow, moist soil.
Frequently, after the farmer has sown his grain, there comes a heavy,
beating rain, and the surface of the soil becomes so packed that the air
is excluded and the seeds cannot germinate. If plants are grown in pots
and the water is supplied at the top, the soil may become so hard and
compact as to exclude the air and the plants will make a sickly growth.
The surface soil must be kept loose so that the air can penetrate it.
[Illustration: _Fig. 41. After the clover dies the soil is in better
condition for its having lived._]
On many lawns it may be noticed that the grass is not thriving. It has a
sickly appearance, and even the application of fertilizer does not seem
to remedy the conditions. Perhaps the ground has become so hard that the
air cannot penetrate and the grass is being smothered. If the surface of
the soil can be loosened with a garden rake, and clover seed sown, much
good may be accomplished. The clover is a tap-rooted plant, sending its
main root deep into the soil.
After the death of the plant, the root decays, and the nitrogen which is
stored in it can be used as food by the other plants. Most useful of
all, however, in such cases, the decay of the tap-root of the clover
makes a passage deep into the soil and thus allows the air to enter.
Consult Figs. 39-41.
LEAFLET X.
THE BROOK.[12]
BY J. O. MARTIN.
INTRODUCTION BY L. H. BAILEY.
[12] Nature-Study Quarterly, No. 5: Leaflet 18. June, 1900.
[Illustration]
A brook is the best of subjects for nature-study. It is near and dear to
every child. It is a world in itself. It is an epitome of the nature in
which we live. In miniature, it illustrates the forces which have shaped
much of the earth's surface. Day by day and century by century, it
carries its burden of earth-waste which it lays down in the quiet
places. Always beginning and never ceasing, it does its work as slowly
and as quietly as the drifting of the years. It is a scene of life and
activity. It reflects the sky. It is kissed by the sun. It is caressed
by the winds. The minnows play in the pools. The soft weeds grow in the
shallows. The grass and the dandelions lie on its sunny banks. The moss
and fern are sheltered in the nooks. It comes one knows not whence; it
flows one knows not whither. It awakens the desire of exploration. It is
a realm of mysteries. It typifies the flood of life. It goes "on
forever."
In many ways can the brook be made an adjunct of the school-room. One
teacher or one grade may study its physiography; another its birds;
another may plat it. Or one teacher and one grade may devote a month or
a term to one phase of it. Thus the brook may be made the center of a
life-theme.
L. H. B.
I. A BROOK AND ITS WORK.
On a rainy day most of us are driven indoors and thus we miss some of
nature's most instructive lessons, for in sunshine or rain the great
mother toils on, doing some of her hardest labor when her face is
overcast with clouds. Let us find our waterproofs, raise our umbrellas,
bid defiance to the pattering rain, and go forth to learn some of the
lessons of a rainy day.
[Illustration: _Fig. 42. The brook may be made the center of a
life-theme._]
Along the roadside, the steady, down-pouring rain collects into pools
and rills, or sinks out of sight in the ground. The tiny streams search
out the easiest grade and run down the road, digging little gullies as
they go. Soon these rills meet and, joining their muddy currents, flow
on with greater speed down the hillside until they reach the bottom of
the valley and go to swell the brook which flows on, through sunshine or
rain. The water which sinks into the ground passes out of sight for a
time, but its journey is also downward toward the brook, though the
soil, acting as a great sponge, holds it back and makes it take a slower
pace than the rushing surface water. This slower-moving underground
water percolates through the soil until it comes to a layer of rock,
clay, or other impervious substance, along the slope of which it flows
until it is turned again to the surface in the form of a spring. Perhaps
this spring is one of those clear, cold pools, with the water bubbling
up through its sandy bottom, from which we love to drink on a hot
summer's day; or, again, it is a swampy spot on the hillside where the
cat-tails grow. In whatever form it issues from the ground, a tiny rill
carries away its overflow, and this sooner or later joins the brook.
The brook, we see, is simply the collected rainfall from the hillsides,
flowing away to join the river. It grows larger as other brooks join it,
and becomes a creek and finally a river. But where is the dividing line
between brook, creek, and river? So gradually does the brook increase in
volume that it would be difficult to draw any dividing line between it
and the larger streams. And so with the rills that formed the brook:
each is a part of the river, and the names rill, brook, creek, and river
are merely relative terms.
Brooks are but rivers on a small scale; and if we study the work that a
brook is doing, we shall find it engaged in cutting down or building up,
just as the river does, although, owing to the smaller size of the
brook, we can see most of these operations in a short distance. Let us
take our way through the wet grass and dripping trees to the brookside
and see what work it is doing.
The countless rain-born rills are pouring their muddy water into the
brook and to-day its volume is much greater than when it is fed, as it
is in fair weather, by the slower-moving underground water of the
springs. It roars along with its waters no longer clear but full of clay
and sand ("mud" as we call it).
If we should dip up a glassful of this muddy water, we should find that
when it had settled there remained on the bottom of the glass a thin
deposit of sediment. The amount of this sediment is small, no doubt, for
a single glassful, but when we think of the great quantity of water
constantly flowing by, we can see that considerable sediment is going
along with it. But this sediment in suspension is not all the load that
the brook is moving. If you will roll up your sleeve, plunge your hand
to the bottom of the brook and hold it there quietly, you will feel the
coarser gravel and small stones rolling along the bottom.
All this load of sand and gravel comes, as we have seen, from the valley
sides, the banks of the brook, and from its bed. It is moving downward
away from its original resting place; and what is the result? For
thousands upon thousands of years, our brook may have been carrying off
its yearly load of sediment; and though each day's labor is small, yet
the added toil of centuries has been great. The result of this labor we
can see in the great trough or valley through which the brook flows.
Tennyson speaks of the ceaseless toil of the brook in the following
words:
"I chatter, chatter, as I flow
To join the brimming river,
For men may come and men may go,
But I go on forever."
[Illustration: _Fig. 43. A brook cutting under its bank and causing a
landslide._]
We have seen how the rills and torrents bring into the brook their loads
of sand, clay, and gravel; now let us walk along the bank and see what
the brook is doing to increase this load. Just here there is a sudden
turn in the channel and so sharp is the curve that the rushing stream is
not able to keep in mid-channel, but throws itself furiously against the
outer bank of the curve, eating into the clay of which it is composed,
until the bank is undermined, allowing a mass of clay to slide down into
the stream bed, where it is eaten up and carried away by the rushing
water (Fig. 43). Farther on, the brook dashes down a steep, rocky
incline, and if we listen and watch we may hear the thud of boulders
hurled along, or even see a pebble bound out of the muddy foaming water.
These moving pebbles strike against each other and grind along the
bottom, wearing out themselves as well as the large unmovable boulders
of the rocky bed of the brook. Thus the larger stones are ground down,
rounded at first but in time reduced to sand, adding in this way to the
moving burden of the brook. By this slow process of cutting and
grinding, the deep rock gorges of New York state, like those at Watkins,
Ithaca, Au Sable Chasm, and even the mighty gorge of Niagara, have been
made. The Grand Canyon of the Colorado, over a mile in depth, is one of
the greatest examples of stream cutting to be found in the world.
[Illustration: _Fig. 44. A pile of brook debris deposited by the
checking of the current._]
Now the brook leads us into a dripping woodland, and just ahead we can
hear the roar of a little waterfall, for at this point the cutting
stream flows upon the bed rock with its alternating bands of hard and
soft rock through which the busy brook is cutting a miniature gorge.
Here is a hard layer which the stream has undermined until it stands out
as a shelf, over which the water leaps and falls in one mass with a drop
of nearly ten feet. Watch how the water below boils and eddies; think
with what force it is hammering its stone-cutting tools upon the rocky
floor. Surely here is a place where the brook is cutting fast. Notice
that swirling eddy where the water is whirling about with the speed of a
spinning top; let us remember this eddy and when the water is lower we
will try to see what is happening at its bottom.
On the other side of the woods our brook emerges into a broad meadow;
let us follow it and see what becomes of its load, whether it is carried
onward, or whether the tired brook lays it down occasionally to rest.
Out of the woods, the brook dashes down a steep incline until the
foaming tide comes to rest in a deep pool. What becomes of the large
pebbles which have been swept down? Do they go on or do they stop? If
you go to the outlet of the pool you will see that the water is coming
out with nothing in its grasp but the fine clay and sand, the gravel and
pebbles having been dropped by the less rapid current of the pool. This
is one of the most important of the brook's lessons, for anything that
tends to check the current makes it drop some of the sediment that it
carries (Fig. 44). Yonder is an old tree stump with its crooked roots
caught fast on the bottom; the mid-stream current rushes against it only
to be thrown back in a boiling eddy, and the waters split in twain and
flow by on either side with their current somewhat checked. In the rear
of the stump is a region of quiet water where the brook is building up a
pile of gravel. Farther on, the banks of the brook are low and here the
waters no longer remain in the channel, but overflow the low land,
spreading out on either side in a broad sheet. The increased friction of
this larger area reduces the current, and again we see the brook laying
down some of its load. The sand and gravel deposited here is spread out
in a flat plain called a _flood plain_, because it is built up when the
stream is in flood. It is on the large flood plains of rivers that many
of our richest farm lands occur. These receive, each spring when the
stream is in flood, a fresh coating of soil mixed with fragments of
vegetable matter, and thus grow deeper and richer year by year. The
flood plains of the Mississippi and of the Nile are notable examples of
this important form of stream deposit.
[Illustration: _Fig. 45. A delta built by a tiny rill flowing from a
steep clay bank._]
And now let us make one more rainy-day observation before going back to
our warm, dry homes. Just ahead on the other side of that clump of
alders and willows lies the pond into which the brook flows and where
its current is so checked that it gives up almost all its burden of
sediment. Close to the shore it has dropped its heaviest fragments,
while the sand and clay have been carried farther out, each to be
dropped in its turn, carefully assorted as to size and weight. Here you
can see that the stream has partly filled this end of the pond, and it
is now sending its divided current out over the deposit which it has
made in a series of branching rivulets. This deposit is called a _delta_
(Fig. 45), and deltas are another important form of stream deposits. In
the lakes and ponds, deltas may grow outward until the lake is filled,
when the stream will meander across the level plain without much current
and hence without much cutting power (Fig. 46). In the sea, great deltas
are being formed in some places, like those at the mouths of the
Mississippi, the Nile, and the Ganges. Large areas of dry land have thus
been built. Deltas, like flood plains, afford rich farming lands when
they are built high enough to remain above the water.
[Illustration: _Fig. 46. A brook flowing across a pond which has been
filled._]
Here let us end our study of the brook for to-day, and wait until the
rain ceases and the water runs clear again; then we can see the bottom
and can also learn by contrast how much more work the brook has been
doing to-day than it does when the volume of water is less.
On the road home, however, we can notice how the temporary streams, as
well as the everflowing brook, have been cutting and depositing. See
where this tiny rill has run down that steep clay bank until its
current was checked at the foot. Notice how it has spread out its
sediment in a fan-shaped deposit. This form of deposit is sometimes made
by larger streams, especially in a mountainous country with plains at
the foot of the slopes. They are called _alluvial fans_ or _cone deltas_
(Fig. 47), but they are not as important as flood plains and deltas.
[Illustration: _Fig. 47. A brook building a delta into a lake. Formerly
the brook flowed straight ahead, but its own delta has caused it to
change its direction._]
The first dry, sunny morning that comes we visit the brook again. It no
longer roars, but its clear waters now sing a pleasant melody as they
ripple along the stony bed. We can see at a glance that comparatively
little work is going on to-day, and yet if we look closely, we shall see
glittering particles of sand moving along the bottom. The clear water,
however, allows us to study the bottom which before was hidden by the
load of mud.
First we see the rounded boulders and pebbles of all sizes which must
have been rolled about for a long time to make them so smooth. Some of
them are so very hard that we cannot even scratch them with our knives;
others are soft and easily broken. What would be the effect of rolling
together stones of such varying hardness? We must think of these stones
as the tools with which the brook cuts and grinds, for water without
sediment can do little more than slightly to dissolve the rock.
Let us go at once to the little waterfall, for we shall be curious to
see what lies at the bottom of the whirling eddy that drew our attention
yesterday. As we look down into the sunlit pool we see that the eddy is
gone, for the volume of water is not great enough to cause it to
revolve, but there in the rock on the bottom is a deep basin-like hole.
In the bottom of this hole we shall see a number of well-rounded stones,
with perhaps some sand and gravel. These stones are the tools which,
whirled about by the eddying water, have cut the basin-like holes. Holes
of this sort are common in rocky stream beds, especially in the
neighborhood of falls or in places where falls have once been; they are
called _pot-holes_ and represent another form of stream cutting (Fig.
48).
[Illustration: _Fig. 48. A pot-hole cut in the rock of a stream's bed._]
Next let us visit the flood plains which we saw forming when the water
was high. Now we shall find the brook flowing in its channel with the
flood plain deposits left high and dry. If we dig down into the flood
plain, we shall see that it is made up of successive layers varying in
thickness and in the size of the fragments. Each of these layers
represents a period of high water and the size of the fragments in the
layer tells us something of the strength of the current, and therefore
of the intensity of the flood. Some layers are thicker than others,
showing a longer period of flood, or perhaps several floods in which
there was little variation. This _stratification_, as it is called, is
one of the peculiarities of water deposits and it is due to the
assorting power of currents which vary in force. If we were to cut into
the delta we should find the same thing to be true,--a regular
succession of layers, though sometimes confused by changes in direction
of flow.
To-day we shall notice something which escaped our attention when it was
held by the rushing torrent--the valley bottom is much wider than the
bed of the stream; if we keep our eyes open we shall see the explanation
of this in the abandoned channels, where, owing to some temporary
obstructions, the stream has been turned from side to side of the
valley, now cutting on one bank and now on the other. In this turning
from side to side the cutting area of the stream is increased, and it
goes on widening its valley as well as cutting it downward.
And now we have learned some of the most important ways in which the
busy brook is toiling; but there are other points which we might have
seen, and in some brooks there are special features to be noted.
However, we have learned that the brook is no idler, that its main work
is to conduct to the ocean the rain that falls upon the earth's surface,
and that in doing this it is wearing down the hills, carrying them away
only to build up in other places. The cheerful song of the brook takes
on a new meaning as we lie in the shade and watch it hurry by. It is not
the song of idleness nor of pleasure, but like the song with which a
cheerful and tireless worker seeks to make its task lighter.
LEAFLET XI.
INSECT LIFE OF A BROOK.[13]
BY MARY ROGERS MILLER.
[13] Nature-Study Quarterly, No. 5: Leaflet 18, June, 1900.
[Illustration]
What wader, be he boy or water-fowl, has not watched the water-insects?
How they dart hither and thither, some skimming the surface, others
sturdily rowing about in the clear shallows! The sunlight fastens, for
an instant, their grotesque reflections on the smooth bottom, then
away--the shadow is lost, except for the picture it left in the memory
of the onlooker.
The splashing, dashing wader, with his shout and his all-disturbing
stick, stands but a poor chance of making intimate acquaintances among
water-folk. Your true brook-lover is a quiet individual except when
occasion demands action. The lad who, from the vantage ground of a
fallen log or overhanging bank, looks down on the housekeeping affairs
of his tiny neighbors has the right spirit. Indeed, I doubt whether
these little folk are aware of his presence or curiosity.
Time was when the enjoyment of brook-life was limited to boys. White
aprons, dainty slippers and fear of being called "Tom-boy" restrained
the natural impulses of the "little women." Happily that day is past,
and it no longer looks queer for girls to live in the open air and
sunshine, free to chase butterflies and hunt water-bugs with their
brothers.
My brooks abound in swift eddies, perfect whirlpools in miniature, and
water-falls of assorted sizes. They have also their quiet reaches, where
whirligig beetles perform their marvelous gyrations, and bright-eyed
polliwogs twirl their tails in early May. On the banks are ferns and
mosses; sometimes willows and alders form a fringing border.
The heart-leaved willows along many brooksides are found to bear at the
tips of many of their branches, knob-like bodies which look like pine
cones. (Fig. 49.) Now everybody knows that willows bear their seeds in
catkins. Why, then, should so many brookside willows thrust these cones
in our faces? On cutting one of the cones open, we learn the secret. A
tiny colorless grub rolls helplessly out of a cell in the very centre of
the cone. It is the young of a small gnat, scarcely larger than a
mosquito, and known as a "gall gnat." The cone-shaped body on the willow
branch is called a "pine-cone willow-gall." The little gray gnat comes
out in the spring. Any one can collect the galls from the willows and
keep them in some kind of cage in the house until the gnats come forth.
[Illustration: _Fig. 49. Knob-like bodies resembling pine cones._]
The pine-cone gall is an enlarged and deformed bud. The twig might have
developed into a branch but for the presence of the little larva. The
scales of the cone are the parts which under more favorable conditions
would have been leaves. The brook-lover cannot afford to miss the
pine-cone willow-galls.
Wandering along the brookside in spring or early summer, one is
surprised to find so many insect visitors darting about in the air.
There are dragon-flies of many shapes, sizes and colors; dainty
damsel-flies perch airily on reeds, their gleaming wings a-flutter in
the sunshine; sometimes a nervous mud-wasp alights for a moment, and
then up and away. The dragon-flies seem intent on coming as near to the
water as possible without wetting their wings. They pay no heed to other
visitors, yet how easily they escape the net of the would be collector!
Let them alone. Their business is important if we would have a new
generation of dragon-flies to delight the eye next year. The eggs of
these creatures are left in the water and the young ones are aquatic. If
you would know more of them, dip down into the stream in some sluggish
bay. Dip deep and trail the net among the water plants. Besides
dragon-fly nymphs there will be caddice-worm cases like tiny cob-houses,
water-boatmen, back-swimmers, and giant water-bugs.[14] These are
insects characteristic of still or sluggish water, and are found in
spring and summer.
[14] These and other forms found in still or slow flowing water are
described and pictured in Leaflet No. XII, Life in an Aquarium.
[Illustration: _Fig. 50. Water-striders have long, thin legs._]
The insects which skip lightly over the surface of the water where the
current is not too strong, are water-striders. (Fig. 50.) Some are short
and stout, others slender-bodied; but all have long thin legs. Their
color is nearly black. As they scurry about in the sunshine the
delighted watcher will sometimes catch a glimpse of their reflections on
the bottom. Six oval bits of shadow, outlined by rims of light; there is
nothing else like it! Be sure you see it.
[Illustration: _Fig. 51. The dobson makes no pretensions to beauty.
(Natural size)._]
Let us leave the quiet, restful pools and the sluggish bays, and follow
the hurrying water to the rapids. Every stone changes the course of the
current and the babble makes glad the heart of the wayfarer. Let us
"leave no stone unturned," until we have routed from his favorite haunt
that genius of the rapids, the dobson. (Fig. 51.) These creatures bear
other common names. They are prized by fishermen in the black bass
season. Dirty brown in color and frankly ugly in appearance and
disposition, these larvæ, for such they are, have little to fear from
the casual visitor at the water's edge. When a stone is lifted, the
dobsons beneath it allow themselves to be hurried along for some
distance by the current. The danger over, they "catch hold" and await
their prey farther down stream. In spite of their vicious looking jaws
these insects are not venomous. At the very worst they could do no more
than pinch the finger of the unwary explorer.
[Illustration: _Fig. 52. May-fly nymph._ (_Three times natural size_).]
When the dobson is full grown, it is called a hellgrammite fly or horned
corydalis. It has lost none of its ugliness, though it has gained two
pairs of thin, brownish-gray wings, and flies about in the evening. It
has been known to create some consternation by flying in at an open
window. It is harmless and short-lived in the adult stage.
Upturned stones are likely to bring to view other strangers. Lying close
against these wet stony surfaces one usually finds young May-flies.
(Fig. 52.[15]) These, like the young dragon-flies, are called _nymphs_.
[15] Figures 52, 53 and 54 are adapted from Dr. R. Leuckart's Zoological
Charts.
When they are ready to leave the water they make their way to the shore,
and, clinging to some convenient tree trunk or building, they shed their
nymph skins. I have seen trees and buildings on the banks of the St.
Lawrence river literally covered with these cast skins. In the early
morning in June and July one may watch the molting process, the
unfolding of the gauzy wings, and the unsheathing of the long filaments.
(Fig. 53.)
Do not believe that May-flies are harmful. They are sometimes too
numerous for comfort at summer resorts where myriads of them swarm about
the lights; but stories of their stinging and biting are entirely
without foundation. They are short-lived in the adult stage. The name of
the family to which they belong, _Ephemeridæ_, suggests their ephemeral
existence. It is of these that poets have sung.
Stone-fly nymphs, also, cling closely to the flat stones. The cast skins
of these are frequently found on the banks of streams. They resemble
the May-fly nymphs but can be identified by a comparison with these
illustrations. (Fig. 54.)
Sometimes on the very brink of a cataract one will see what appear like
patches of loose black moss. Strangely enough, these are the larvæ of
black-flies, related to the terrible black-fly of the north woods. The
black-fly larvæ can live only in the swiftest water. There they pass
through their transformations and succeed in emerging into their aërial
stage, in spite of the rushing current.
[Illustration: _Fig. 53. The May-fly sheds its nymph skin._ (_Twice
natural size._)]
All these things and many more are seen by those who frequent the water
brooks. Observers cannot tell all they see, for some things are too deep
for words. They can and do say to one and all, "Come, let us visit the
brook together. The water and all that dwell in it and round about,
invite us and make us welcome."
[Illustration: _Fig. 54. Stone-fly, showing one pair of wings. The
lower figure is a nymph._ (_Twice natural size._)]
LEAFLET XII.
LIFE IN AN AQUARIUM.[16]
BY MARY ROGERS MILLER.
[16] Teachers' Leaflet No. 11. May, 1898.
[Illustration]
There is no more fascinating adjunct to nature-study than a well-kept
aquarium. It is a never-ending source of enjoyment, interest and
instruction to students of any age. Children in the kindergarten or at
home will watch with delight the lively occupants, which cut all sorts
of queer capers for their amusement, and older people may read some of
nature's choicest secrets through the glassy sides of the little water
world. To many, the word aquarium suggests a vision of an elaborately
constructed glass box, ornamented with impossible rock-work and strange
water plants, or a globe in which discouraged and sickly-looking
gold-fish appear and disappear, and take strange, uncanny shapes as they
dart hither and thither.
Such forms of aquaria have their place in the world, but they are not
suited to the needs of an ordinary school-room. Every school may have
some sort of an aquarium if the teacher and pupils are willing to give
it some daily thought and care. Without such attention a fine aquarium
may become an unsightly and disagreeable object, its inhabitants
unhealthy and its beauty and usefulness lost.
The great fundamental principle underlying success in making and
maintaining an aquarium is this: _imitate nature_. We all know how much
easier it is to formulate a principle, and even to write a book about
it, than to put it into practice. Most of us have not had the time and
opportunity for the close observation of nature necessary to interpret
her methods and to imitate her. It is to those teachers who are anxious
to learn what nature has to teach and who wish to lead their pupils to a
higher and wider conception of life, that these suggestions are offered.
Four things are important in making and keeping an aquarium:
1. The equilibrium between plant and animal life must be secured and
maintained. It is probable that an aquarium in an elementary school is
mainly used for the study of animal life; but animals do not thrive in
water where no plants are growing. Nature keeps plants and animals in
the same pond and we must follow her lead. The plants have three
valuable functions in the aquarium. First, they supply food for the
herbivorous creatures. Second, they give off a quantity of oxygen which
is necessary to the life of the animals. Third, they take up from the
water the harmful carbonic acid gas which passes from the bodies of the
animals. Just how the plants do this is another story.
[Illustration: _Fig. 55. A museum-jar aquarium. (More animal life would
make a better equilibrium._)]
2. The aquarium must be ventilated. Its top should be broad and open.
Every little fish, snail and insect wants air, just as every boy and
girl wants it. A certain quantity of air is mixed with the water, and
the creatures must breathe that or come to the surface for their supply.
How does Mother Nature manage the ventilation of her aquaria,--the ponds
and streams? The plants furnish part of the air, as we have said. The
open pond, whose surface is ruffled by every passing breeze, is
constantly being provided with fresh air. A tadpole or a fish can no
more live in a long-necked bottle than a boy can live in a chimney.
3. The temperature should be kept between 40° and 50° Fahr. Both nature
and experience teach us this. A shady corner is a better place for the
aquarium than a sunny window on a warm day.
4. It is well to choose such animals for the aquarium as are adapted to
life in still water. Unless one has an arrangement of water pipes to
supply a constant flow of water through the aquarium, it is better not
to try to keep creatures that we find in swift streams.
Practical experience shows that there are certain dangers to guard
against,--dangers which may result in the unnecessary suffering of the
innocent. Perhaps the most serious results come from overstocking. It is
better to have too few plants or animals than too many of either. A
great deal of light, especially bright sunlight, is not good for the
aquarium. A pond that is not shaded soon becomes green with a thick
growth of slime or algæ. This does not look well in an aquarium and is
likely to take up so much of the plant-food that the other plants are
"starved out." The plants in the school-room window may provide shade
for the aquarium, just as the trees and shrubs on its banks shade the
pond. If we find green slime forming on the light side of our miniature
pond, we should put it in a darker place, shade it heavily so that the
light comes in from the top only, and put in a few more snails. These
will make quick work of the green slime, since they are fond of it, if
we are not.
[Illustration: _Fig. 56. A rectangular glass aquarium._]
Some of the most innocent-looking "water nymphs" may be concealing
habits that we can hardly approve. There are some which feed on their
smaller and weaker neighbors, and even on the members of their own
families. We know that such things go on in nature, but if we wish to
have a happy family we must keep the cannibals by themselves.
After an aquarium has been filled with water and the inhabitants well
established, it is not necessary to change the water, except in case of
accident. The water that is lost by evaporation has to be replaced. It
should be poured in gently in order not to disturb the water and destroy
its clearness. If a piece of rubber tubing is available, a practical use
of the siphon can be shown and the aquarium replenished at the same
time. It is a good plan to use rain water, or clear water from a pond,
for this purpose.
A piece of thin board or a pane of glass may be used as a cover to keep
the dust out of the aquarium. This need not fit tightly or be left on
all the time. A wire netting or a cover of thin cotton net would keep
the flying insects from escaping, and it might be tied on permanently.
Dust may be skimmed off the top of the water or may be removed by laying
pieces of blotting paper on the surface for a moment.
If any of the inhabitants do not take kindly to the life in the
aquarium, they can be taken out and kept in a jar by themselves--a sort
of fresh air and cold water cure. If any chance to die they ought to be
removed before they make the water unfit for the others. Bits of
charcoal in the water are helpful if a deodorizer or disinfectant is
needed.
[Illustration: _Fig. 57. A home-made aquarium._]
Experience, the dear but thorough teacher, is of more value to every one
of us than many rules and precepts. Nothing can rob us of the pleasure
that comes of finding things out for ourselves. Much of the fun as well
as much of the success in life comes from overcoming its difficulties.
One must have a large store of patience and courage and hopefulness to
undertake the care of an aquarium. After it is once made it is less
trouble to take care of than a canary or a pet rabbit. But most things
that are worth doing require patience, courage and hopefulness, and if
we can add to our store of any of these by our study of life in an
aquarium we are so much the better for it.
Two kinds of aquaria will be found useful in any school. Permanent
ones--those which are expected to continue through a season or through a
whole year if the school-room is warm enough to prevent freezing; and
temporary ones--those which are for lesson hours or for the study of
special forms.
If some one phase in the life of any aquatic animal is to be studied
during a short period, it is well to have special temporary aquaria.
Also, when a talk on some of the occupants of the larger aquarium is to
be given, specimens may be placed in small vessels for the time being
and returned later. For such purposes glass tumblers can be used, or
small fruit jars, finger bowls, broken goblets set in blocks of wood,
ordinary white bowls or dishes, tubs, pails or tanks for large
fishes,--in fact any wide-mouthed vessel which is easy to get. Special
suggestions will be made in connection with the study of some of the
water insects and others.
A permanent aquarium need not be an expensive affair. The rectangular
ones are best if large fishes are to be kept, yet they are not
essential. Here, again, it is easier to write directions for the
construction of a perfect aquarium than it is for the most patient
teacher, with the help of the boys who are handy with tools, to put
together a box of wood and glass that will not spring a leak some day
and spoil everything. But failures do not discourage us; they make us
only more determined. If a rectangular water-tight box is out of the
question, what is the next best thing? One of the busiest laboratories
in New York State has plants and animals living in jars of all shapes
and sizes,--fruit jars, glass butter jars, candy jars, battery jars,
museum jars, and others of like nature. There are rectangular and round
aquaria of various sizes kept by all firms who deal in laboratory
supplies, and if some money is to be spent, one of these is a good
investment. Fig. 56 shows one of these rectangular ones, and Fig. 57
shows a round one of small size which is useful and does not cost much.
A GOOD SCHOOL AQUARIUM.
A cheap, substantial aquarium for general use may be made of glass and
"angle" or "valley" tin. Pieces of glass are always handy and the tin
can be had at any tin-shop. The tinsmith will know just how to cut,
"angle" and solder it.
The following directions for making an aquarium of this kind are
supplied us by Professor C. F. Hodge of Clark University. He has made
and used them for years with great satisfaction in the university
laboratory and in graded schools.
The illustration (Fig. 58, 59) shows various sizes. A good all-round
size has these dimensions: 12 inches high, 15 inches long and 8 inches
wide. One may use spoiled photographic plates for small desk aquaria, in
which to watch the development of "wigglers," dragon-fly nymphs or other
water insects. Lids of wire screen are shown on some of the aquaria in
the picture (1, 2 and 3).
_To make the frame._--If the aquarium is to be 10 x 8 x 5 inches, we
shall need two pieces of glass for sides 10 x 5 inches, two for ends 8 x
10, and one for bottom 8 x 5; and two strips of tin 3/4 inch wide, 28
inches long, and four strips 10-3/8 inches long. These should be angled
by the tinner, and out of them we shall make the frame. The 28-inch
strips should be cut with tinner's snips half way in two at 10-3/8,
5-3/8, 10-3/8 and 5-3/8 inches, cutting off the end at the last mark.
This keeps the top and the bottom of the frame each in one piece. Next
we bend them into shape. When the corners are well squared they should
be soldered. The four 10-3/8 pieces make the vertical corners and we
will solder them in place. An easy way to be sure that each angle is
square is to hold it in a mechanic's square while soldering it.
[Illustration: _Figs. 58, 59. Permanent aquarium made of tin and
glass._]
_To set the glass._--Lay the aquarium cement (see recipe) on evenly all
around the bottom of the frame and press the bottom glass into place.
Put in the sides and ends in the same way. Next carefully put a few very
limber twigs into the aquarium to hold the glass against the frame till
the cement takes hold. Cut off the extra cement with a knife and smooth
it nicely. Cover the frame with asphaltum varnish or black lacquer. In
a week it will be ready to use.
Double thick glass must be used for large aquaria.
_Cement._--Shun all resinous cements that require to be put on hot. The
following is a recipe for cement used in successful angle tin aquaria,
for both salt and fresh water:
10 parts, by measure, fine, dry, white sand,
10 parts plaster of Paris,
10 parts litharge,
1 part powdered resin.
Stir well together and, as wanted, mix to consistency of _stiff_ putty
with _pure_ boiled linseed oil.
The formula given by the U. S. Fish Commission is recommended:
8 parts putty,
1 part red lead,
1 part litharge.
Mix, when wanted, to consistency of _stiff_ putty, with raw linseed oil.
After reading all these directions and getting the idea of an aquarium,
one should think the whole matter out for himself and make it just as he
wants it. Directions are useful as suggestions only. The shallow form is
better for raising toads, frogs and insect larvæ; the deeper aquaria
show water plants and fishes to better advantage.
INHABITANTS OF THE AQUARIUM.
[Illustration: _Fig. 60. Eel-grass._]
It is now time to begin to think about what shall be kept in the
aquarium. At the bottom a layer of sand, the cleaner the better, two or
three inches deep will be needed. A few stones, not too large, may be
dropped in on top of this first layer, to make it more natural. The
water plants come next and will thrive best if planted securely in the
sand. The most difficult thing is to get the water in without stirring
things up. A good way is to pour the water in a slow stream against the
inside of the aquarium. The best way is to use a rubber tube siphon, but
even then the water ought not to flow from a very great height. If the
aquarium is large, it had better be put in its permanent place before
filling.
The aquarium will soon be ready for snails, polliwogs, and what ever
else we may wish to put into it. In the course of a few days the plants
will be giving up oxygen and asking for carbon dioxid.
[Illustration: _Fig. 61. Duck-weed._]
_Plants that thrive and are useful in aquaria._--Many of the common
marsh or pond plants are suitable. The accompanying illustrations show a
few of these. Nothing can be prettier than some of these soft, delicate
plants in the water. The eel-grass, or tape grass (Fig. 60), is an
interesting study in itself, especially at blossoming time when the
spiral stems, bearing flowers, appear.
Any who are especially interested in the life-history of this plant may
read in reference books a great deal about what other observers have
learned from the plant concerning its methods of growth and development.
The best that we learn will be what the plant itself tells us day by
day.
Some of the best reference books on both plant and animal life are found
in the New York State Teachers' Library and can be obtained by teachers
through the school commissioners.
[Illustration: _Fig. 62. Water plants._]
Every boy and girl who likes to taste the fresh, peppery plants which
they find growing in cold springs, knows watercress. If the aquarium is
not too deep, this plant will grow above the surface and furnish a
resting place for some snail which, tired perhaps by its constant
activity, enjoys a few minutes in the open air.
Duck-weed or duck's-meat (Fig. 61) grows on the surface, dangling its
long thread-like roots in the water. A little of it is enough. Too much
would keep us from looking down upon our little friends in the water.
The parrot's feather (Fig. 62, A) is an ornamental water plant that can
be obtained from a florist; a plant that looks very like it grows in our
ponds. It is called water-milfoil.
The water purslane, B, or the common stoneworts, _Nitella_ and _Chara_,
D, E, the waterweed, F, and the horn-wort, C, appear graceful and pretty
in the water. If you do not find any of these, you are sure to find
others growing in the ponds in your neighborhood which will answer the
purpose just as well.
[Illustration: _Fig. 63. Snail._]
_Animals that may be kept in aquaria._--_The snail._ The common pond
snail with the spiral shell, either flat or conical, can be found
clinging to the stems of the cat-tails or flags and to floating rubbish
in ponds or swamps. If these are picked off carefully and taken home in
a pail of water they will be valuable inhabitants for the aquarium. They
are vegetable feeders and unless there is some green slime in the water,
cabbage or lettuce leaves may be put where the snails can get them. The
eggs of the snail are excellent food for fishes, and if a few could be
secured for special study, their form, habits and development may be
made delightful observation and drawing lessons. Snails can be kept out
of the water for some time on moist earth. Land snails and slugs should
be kept on wet sand and fed with lettuce and cabbage leaves. The common
slug of the garden is often injurious to vegetation. It may always be
tracked by the trail of slime it leaves behind it. Gardeners often
protect plants from those creatures by sprinkling wood-ashes about them.