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Ralph S. (Ralph Stockman) Tarr.

A laboratory manual for physical and commercial geography online

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353



In what wind belts (Fig. 40)?

What are the temperature and rainfall conditions in the tropical forest belt ?



Make a list of the tropical trees of which you know the names.



Through what countries does

the belt of m ost extensive forest in the temperate zone extend ?



What are the temperature

and rainfall conditions there?

Make a list of some trees that grow in the cool temperate
forest.

In which, fhe temperate or tropical forest belt, does vegetation grow most luxuriantly?

Through which of these forest belts would it

be more difficult for an explorer to pass ?

Why should so much forest be left in the more
northerly countries, while it has been stripped off in the regions immediately to the south ?



Explain the long, narrow strips of forest in the belt south of the northern forests.



9



9



354



3



ft



In what zones are the principal agricultural belts located ?



What leading countries in

the northern hemisphere are included?



What countries in the southern hemisphere ?



What are the rainfall conditions in these belts ?



.. If the land were not needed for agricul-



ture, would forests grow in these belts? Trace the northern limit of

grain. What countries of the northern hemisphere are partly to the north of this line ?



What countries of the southern hemisphere extend beyond the limit of grain growth ?

In which hemisphere, northern or southern, is most agricultural land found in the temperate

zone?

Locate the chief deserts and tell in which part of each continent they are found.



Which continent has most desert? Which

continent least? How does North America

rank in amount of desert?



Why will forests not grow in deserts ? ..
355



In what zones are the largest deserts located?

In what rainfall

belts?



Where are the principal grazing lands located ?



What are the rainfall conditions in

such regions ? W T hy are the savannas of the

torrid zone arid in one season ?



Why are there great areas of grazing land in the interiors

of continents ?

Why do forests not grow in these regions ?



Are the grazing lands sparsely

or densely settled? How must they com-
pare with the agricultural lands in respect to density of population?



With the deserts?



Why are the tropical forests not densely settled ?



Distribu- Figure 45 shows the three realms of animal life, and some of the main subdivisions. In

tion of each f these divisions the animals differ very much. From this map, what should vou iudee

animal life. r j j t>

was the chief barrier to the spread of types of animals that live on the land ?

356



}




ANTARCTIC CIRCLE



100° Longitude WeBt 60" from Greenwich 20 s



20° Longitude East 60° from Greenwich 100°



Fig. 45. — Map showing Three Realms of Animal Life and Main Subdivisions.

Do deserts also serve as a barrier?

mountain ranges ? Do differences in temperature ?

Why should South American animals differ so greatly from those of Africa ?



Do



What bar-
rier would serve to check the spread of life to Australia ?

What barrier partly cuts off the Oriental Region from the Northern Realm ?

What barrier tends to prevent the spread of

animal life from the Northern Realm into the Ethiopian Region?

Is such a barrier as effective as that between Africa and South America?

357




How may differences in climate help to account for the failure of

animals of North and South America to migrate more freely ?



What one condition affecting animal life is practically the same throughout the extensive
Northern Realm ?

How can you explain the fact that the animal life throughout this great

realm is so nearly alike?



What would be the effect of former greater elevations partly or

wholly closing up the water areas between the continents ?



Australian animals are wholly

different from those of southern Asia. What does this fact indicate as to the probability of

former connection between these two lands ?



#



t



358



J



LXXIII. — MAGNETISM

Materials. For Each Student. — Two small needles.

For General Class Use. — Several small bar magnets (preferably one for each student). One or
more magnetic compasses.

Purpose. To study the properties of a magnet, the magnetism of the earth, and the use of a compass.

The attrac- Let each student take one of the magnets and place it near his needle. What happens?

tion of a

magnet ' Place one end of the magnet near the needle

point. Now place the other end near the needle point. Repeat this at the other end of the

needle. What happens in each case ?



Try the magnet on objects other than iron (such as

glass, a penny, a nickel, a dime, etc.) What is the result?

What can you say about the

attraction of the magnet ?



Complete this sentence : There is some force in the _ _

which draws the to it. Of what metal is the needle made ?



Does the magnet attract other iron objects (such as a knife, nails, etc.)?

Magnetiz- Rub one of the needles over the magnet several times. Place this needle near the other one.
inga

needle. What happens? .

Now place one end of the magnet near the point of the needle

that you have rubbed on the magnet. What happens ?

Try the other end of the magnet. What happens?

359



Go through the same procedure with the eye of the needle. What is the difference in the be-
havior of this needle as compared to the one that was not rubbed on the magnet ? _



The two ends of the magnet are called its poles. Since the needle is now a magnet, what may

its two ends be called ? Like poles of a magnet repel each other ;

and unlike poles attract each other. From this principle determine the like poles in the mag-
net and the needle. Find which end of the magnet will repel the north end of the needle in

the compass.

Suggestion Take the magnetized needle home. Cut off a thin slice from a small cork and thrust the needle through

for home the thin edge and parallel to the flat surface. Place this in a dish of water and the cork will float the needle,
work.



Which way does the needle point.



Change its position



and note if it returns to the same position as before ? Repeat this experiment

several times. If you could get the same result in all parts of the world, what useful purpose would such a



floating needle serve ?



The com-
pass.



How can you prove that the needle of the compass is not an ordinary piece of steel ?

Does it behave like the ordinary needle, or the magnetized needle, when the different poles of
the magnet are brought up to it ?



Earth's
magnetism.



What does this prove



In what directions do the two ends of the needle of the compass point?

What makes the needle always come to rest in that position ?



On a large globe or a map of North America find Boothia Land where the north magnetic pole is

situated. What is its location with reference to the north pole of the earth ?

360



O



In which of your previous experiments have you determined the

true north-south line ? Does the compass

needle point toward the north pole or the north magnetic pole?

What is the meaning of "true north " ?



Of "magnetic north"?



With the compass find how many degrees difference there is between true and magnetic north

in your locality. ..

Isogonic Figure 560 in the Text-book is an Isogonic Map. What does it illustrate ?

map.



Find the

isogonic line that runs nearest your home and draw it on the map (Fig. 46). How much is the

declination? Is it east or west declination?

Knowing the declination, what correction to a compass reading

would you have to make to get true north ?

2 Draw on the map the isogonic line that runs

nearest New York City. What is the amount and direction of the declination there ?

Do the same for Columbia, S.C.

For Augusta, Me.

For San Francisco. In what part of

the United States is there greatest east declination ?

Greatest west declination ?

Use of the Of what use is the compass ?

compass.



361




Fig. 46. — Blank Chart fob drawing Isogonic Links.
Why is it more useful to sailors than to any other class



of men ?



What is the significance of the fact that the use of the compass was discovered just before the
time of Columbus ?



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BOOKS BY RALPH S. TARR

Professor of Dynamic Geology and Physical Geography at Cornell University



New Physical Geography

Fully illustrated, cloth, l2mo, $1.00 net

" I like the spirit and tone of this work more than anything else I have seen on the subject.
The presentation especially of erosion, land formation, glacial action and effect is especially
clear, and with the aid of the admirable pictures and diagrams becomes truly fascinating.
The topical questions and ample references at the end of each chapter make it a very usable
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First Book of Physical Geography

• , Illustrated, cloth, l2mo, $1.10 net

"This is, in every case, the new physical geography, skillfully and attractively presented. It
is a thoroughly scientific work, and yet its treatment is so elementary that it may be used
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needed by every grammar school pupil, but what signifies vastly more, the pupils get this
information in a way that gives thorough discipline in observation, careful reading, dis-
criminating thinking." — Journal of Education.

Elementary Physical Geography

Illustrated, i2mo, half leather, $1.40 net

This book is designed specially for classes in the latter part of the high school course.'
The material has been carefully selected so as to weed out the superfluous and less important,
and care has been taken to insure scientific accuracy. The illustrations are a prominent
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The Physical Geography of New York State

Illustrated, cloth, 8vo, $3.50 net

Summary of Contents

General Physiographic Features — The Mountains of the State — Plains and Plateaus — The
Influence of the Glacial Period upon Topography — The Rivers of New York — Lakes and
Swamps — Origin of the Basins of the Great Lakes — Post-glacial History of the Great Lakes
— Niagara — The Shore Lines — The Climate of New York — Influence of Physiographic
Features upon the Industrial Developments of the State.



Teachers are invited to send for a full list of the series
of geographies by Tarr and McMurry.



PUBLISHED BY

THE MACMILLAN COMPANY

64-66 Fifth Avenue, New York



Books for Supplementary Reading in Geography

How We are Fed: A Geographical Reader
By JAMES FRANKLIN CHAMBERLAIN

Department of Geography, State Normal School, Los Angeles, Cal.

Illustrated, cloth, I2mo, $.40 net
Here the pupil is given a clear idea of those great world activities which touch the daily life
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Similar in scope and treatment to How We are Fed. The chief materials and processes
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How We are Sheltered: A Geographical Reader
By JAMES FRANKLIN CHAMBERLAIN

Cloth, l2tno, $.40 net
An intelligent study of the homes of men in various nations and of every degree of advance-


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Online LibraryRalph S. (Ralph Stockman) TarrA laboratory manual for physical and commercial geography → online text (page 15 of 16)