Imágenes de páginas

countries having usually moist weather. The and rapids. This enables boats to have rivers in these dry sections cut deep gorges called a continuous line of transportation and canyons. There are many canyons in the highlands of western United States. Observe those lessens the expense of shipping. How? in the pictures.

Rivers help Rivers and smaller

the lumbermen. streams usually have

How? wooded banks. The

The waterfalls richest farming lands

in our rivers in the world lie in the

have long been flood-plains of the

utilized by man river valleys. Fine pas

for turning millwheels. More and more, how ever, steam is taking the place of water power alone.

The tremendous force of Niagara is used in generating electricity to light and serve as motor

power in cities a GOODRICH FALLS,N.H.

[ocr errors]
[ocr errors]

tures lie in

NIAGARA FALLS. the higher land of the valley slopes.

long distance from the fall. The Niagara Falls are Great cities or trade-centers are upon the

one of the wonders of the world. The American rivers. These are connected by railways Fall on the left of the picture is about 165 feet, and boats, which serve as outlets for the and the Canadian Fall is about 150 feet high.

Carefully study and describe each of the pictures products of the great farming districts.

on this page. Observe how the water is wearing Canals are usually made around falls down the rocky ledge in the Yosemite Falls.

Many of the higher mountains of the ice melts, leaving the rock fragments world have rivers of ice flowing for and other material strewn over the some distance down their sides. You ground. Large rivers full of fine soil wonder how they

come from these ice were formed ?

streams. The soil is If you squeeze a snow

carried to the floodball very hard and work

plain or to the sea. it for some time with

Many gravel and your hands, it becomes almost a ball of ice.

sand hills are formed This is caused by the

by the material pressure and warmth of

brought down by your hands.

these rivers. In mountainous lo

Rains wash the calities where there

sand from these sand is a great fall of snow,

hills to the lower the snow does not

land, covering it with a all disappear through

sandy, barren soil. the summer months.

Glaciers, or ice More snow falls each

rivers, are in Alaska, winter for several

Greenland, western years than can melt

Canada and United during the summer, so

States, and on the that the depth is con

mountains of Europe, stantly increasing. The

South America, and great weight of this accu

Asia. mulation, together · with the heat from

There was a time in the

Earth's history when the the sun's rays, causes

cold belts extended much the snow to change

farther towards the to ice. This ice forms

Equator than at the into streams which

present time. After

many, many years there flow slowly down

was a great accumulathe mountain sides.

tion of snow. Through Ice streams tear

pressure and heat this

snow changed to ice, and up trees, plants, and

flowed slowly down the

END OE ULACIER soil, and break off

slopes in streams, or

spread out on the plains large rock masses in

in a broad, continuous their descent. They carry these in the sheet of ice. This ice sheet covered all of the ice to lower, warmer sections, where the northern parts of North America and Europe,


extending across the continent of North America courses down the mountain side. Many in a westerly direction from New Jersey.

people visit the regions where the ice How do we know that there were once

rivers and ice sheets now are. They do this ice-sheets in the

because of the grandeur and beauty world? We

which they present, and also because know this

the history of the past conditions because of

may be read through what is the great

taking place to-day. amount of

The ice from some material

of the glaciers of which was

to-day is utilized

by man as an left when GRAVEL &

article of trade. the ice was

Men cut it into melted by SAND HILLS

blocks and LEFT BY the warmer

transport it to THE ICE

cities, where it weather. RIVER..

is sold to supLarge pieces

ply people with of rocks,

ice during the

su m m er which we

months. call bowlders, were left

When the strewn over the surface at this time.

ice river descends to the sea the weight Do you know of any bowlders in your school district ?

of the ice, together with the pressure In some cases the valleys were filled of the water underneath, causes great and the mountains completely buried by masses of ice to break off. These are this mate.

icebergs. rial. Some

They float of our

away, and plains and

are dan. prairie

gerous to land were

steamer's made in

and boats this way.

because of The soil of

their great the areas


(P. 117.) covered with ice is quite different from Describe each of the pictures. Note the great that of other sections.

chasms or gorges in the ice which make traveling

over the glaciers very dangerous. Visit sand hills, Many lakes lie in the depressions made clay beds, and bowlder-strewn surfaces. Learn all by the old ice rivers as they gouged their you can about them. Describe and sketch them.


Here is the picture of a lake. It lies On the next page is the picture of a in the lowest part of a hollow in the lake which lies in a basin in the lowland. land surface high up in the mountains. Tell how this lowland Jake basin differs from The entire hollow is a lake basin. the mountain lake basin. Trace its shore-line.

Tell what plants The lake is

are growing on its fed by the

shiore. What evstreams which

idences of life are

there? form from the rains and melt

On the next ing snow, and

page there are flow down the

pictures of inside slopes

ponds; one is of the basin.

in the mounThe land

tains, and one which borders

is in the lowthe water of

lands. a lake is a lake

Trace around shore. The

each. Trace the

slopes of each. shoreline is

What evidences the line where

of life are there the land slopes

in these pictures? under the wa

You see ter. The high

ponds are like er and lower

lakes in form, land of the

only they are lake shore

smaller. causes many

Α ιι irregularities A MOUNTAIN LAKE.


BY FEEDER CAPE in the shore-line. In places where

PONDS are the shores are high the land pro

fed by jects out into the water; in places

streams where the shore is low the water

and springs. flows over the land, making indenta

Some lakes tions of the lake into the land.

and some ponds If you could lo vk down on this lake you should

have only one

MAP OF A MOUNTAIN LAKE. see its true shape or map. Trace the shore-line

large feeder. of the lake pictures. Tell where there are projec- Lakes and ponds usually have OUTLETS tions and indentations. Model this lake-basin. Tell which part is occupied by the lake. Represent

which carry the water away from them to the streams which feed it.

lower land and to the sea.

[ocr errors]

The feeders are usually muddy. This All lakes and ponds of the world are is because they

filling up. carry a great

· We can find deal of soil.

old lake botThey carry

toms in almost much more

any locality. soil during

Observe the heavy rains or

pictures on the melting snows

next page. than at any

Both are fine other time.

illustrations of The dirt or soil

a lake basin is washed from

in the process

of filling. the mountain

You see vil sides as the

lages are streams de A LOWLAND LAKE.

built on the scend to the

mud plains. During flood-time the hollows occupied by the lakes and ponds are completely filled with water. The water often reaches far up on the shore. In the highland region the basin overflows at its lowest point and the water flows away to lower land. The


A MOUNTAIN POND. lake. This soil settles in the bottom of that part of the pond or lake which is nearest the entrance of the stream.

Streams continue to carry soil to the pond or lake until it is filled up. It first becomes swampy, and

A LOWLAND POND. then a solid, fertile plain. Such plains are usually drained by one or more water from the lake in the lowland streams.

spreads far out over the low-lying land.

« AnteriorContinuar »