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Ralph S. (Ralph Stockman) Tarr.

A laboratory manual for physical and commercial geography online

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Materials. For Each Student. — The topographic map of the region, if published.

Purpose. To study the form and stage of development of a valley in the home region; to interpret its

past history ; and to gain an appreciation of the probable changes in the future.

Introduc- For the purpose of this excursion a valley of moderate size is better than a large one.

tory. (Even a gully in a field would serve for such an excursion, though it would then be necessary

to modify this outline.) There would be no disadvantage in going to the same valley as that

studied in section XII.

The valley Where does the stream rise?.

form.

Where is the mouth ?

About how long is it?

To what is it tributary?

About how wide is its valley ? About how deep is the valley ?

What is the nature of the divide (sharp, flat, etc.) between this

valley and the next one ? Are the sides of

the valley steep or gently sloping? ._

If the sides are different in different parts, state the

nature of the difference.



Has the valley form the characteristics of youth, maturity, or old age?

Is there greater or

less maturity toward the mouth of the stream ? '_

Thestream. About how wide is the stream ? How does this compare with

the width of the valley?

^^ Is the stream ever larger? About how

much? Are there flood plains ?



231



Is the course meandering? Does the stream flow on bed rock

anywhere? Are there any lakes in this valley ?

Are there falls or rapids?

What evidence, if any, is there that the stream is enlarging its valley either

laterally or vertically?



What evidence, if any, is there that the stream is aggrading its valley?.



What does the condition of the stream and its relation to the valley indicate as to the age
stage of the valley?



Processes In what part of its valley does a young stream cut most rapidly ?

of valley

formation.



the valley form if this were the only process in valley formation ?

232



What would be



How does weathering aid

in valley widening?



How does the stream itself tend to widen its valley ?



Which is the more rapid, the verti-



cal cutting by the stream, or weathering?

Which, therefore, represents the longer time for its formation, a broad valley or a gorge valley ?

Apply these conclusions in proving your

previous statement about the age stage of this valley.







Rate of Have you ever observed, or heard of any change in the form of this valley?

valley for-
mation.

Are visible changes to be expected in a year ? In ten years ?

In a thousand years? Is the rate of valley formation rapid or slow?

About how much material has been removed from the valley where

you stand ? Answer by filling out the following sentence : A depth of about

feet, and a width of about 1 feet (or miles). Where has all this material

gone?

Is the stream always carrying sediment? Write a brief paragraph stating

what you conclude as to the rate of valley formation and the time required to form such a



valley as this one.

233



The future Will the stream continue to erode this valley deeper? Where is its

of the val-

ley> base level ? r __— r

Can it erode below that? _ Will weathering

continue? Will its rate increase or decrease ?

Write a brief paragraph

telling what you consider to be the future of this valley, if no accident intervenes, giving rea-
sons for your conclusions.



234



LV.— EXCURSION TO STUDY THE GENERAL PHYSIOGRAPHY OF THE

REGION

Materials. For Each Student. — The topographic map of the region, if published.

Purpose. To gain an appreciation of the physiographic features of the home region; its topography,

drainage, and cultural relations.



Introduc-
tory.



Topog-
raphy.



If possible, these observations should be made from some elevated view point, such as the
top of a hill overlooking the surrounding region, or a tower which affords a broad outlook.
Failing such a vantage point, it may still be possible to find a site from which the general
topography of the region can be appreciated and studied.

What great class or classes of rocks have you observed in this region ?



If sedimentary,



are the layers horizontal or inclined ?



What can you infer from this as to the former con-



dition of the region ?



What marked changes have occurred in the region since the time of

the formation of the rocks?



What is the topographic form of the region, i.e. is it a

plateau, flood plain, mountain valley, etc.? ■.

235



What is the elevation above sea level of the

place on which you are standing, as shown by your topographic sheet?

Locate and give the names and elevations of any other hills or

summits which are visible and are shown on your map.



What can you say regarding their

origin and history ?



Drainage. Locate and name the largest stream of the region.



Is it a continuous or an intermittent

stream? j What is the source of its water

supply?



To what drainage system does it belong ?

236



What tributaries has the main

stream of this region?



Has the main stream a straight or meandering course ?
Is it cutting down or building up its channel ?



How do you explain this condition ?



What is the topographic age of the stream valleys,

— young, mature, or old? : Describe their

form to show what you mean by applying such a term to them.



Are there any lakes, and if

so, what caused them?



237



Human What was the main physiographic factor which led to the establishment and growth of

occupation.

the community in which you live?



What is the bearing of the fact that the mainstream is

navigable or not navigable?



That the region is level, hilly, or mountainous ?



What has

been the influence of the topographic age of the valleys on the growth and development of the



region ?



What are the main lines of transportation and travel ?



In what ways have these

been influenced or determined by the topography ?



238



Is the climate of the region humid, dry,

or arid? What has been the effect of the

climatic conditions on the human occupation of the region?



Is the region an agricultural,

grazing, mining, or manufacturing district?

What physiographic factors have determined

this? "_



Write a short paragraph stating the influence of the physiography on the settlement,
present occupation, and development of the region in which you live.



239







THE OCEAN
LVI. OCEAN CURRENTS

Purpose. To study the cause of the system of ocean currents, and to note the influence of the

currents on temperature.



Relation of Figure 22 is a chart showing the system of ocean currents in the oceans of the world ;

ocean cur- ant \ Figure 40 (p. 329) shows the prevailing winds over the oceans. In each case the arrows

rents to point in the direction of motion of the water or air. Compare these two charts to see
winds

how they resemble each other. For instance, how does the ocean current south of

Australia, South America, and Africa compare with the wind direction in that region?



How do the winds and currents agree in the northern Atlantic and Pacific ?



Why is the current in the southern hemisphere more regular than that in the northern ?



What is the direction of winds in the tropical zone on each side of the equator ?



How does the motion of the ocean waters correspond to this ?



What effect have the continents on the ocean currents ?.



If you were to blow on the surface of a pan of water, which way would the water move ?



241



What must be the effect of the steady blowing of the wind in one direction over a large body
of water like the ocean ?

From your study of the wind and ocean current charts, state the primary cause of the ocean
currents.




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The ocean
eddies.



Fig. 22. — A Chart showing the Principal. Ocean Currents and Ocean Drifts in the World.

On the chart (Fig. 22) locate two great eddies in the Atlantic Ocean and two in the
Pacific. On which side of the equator does each lie?



242



Selecting one in the northern hemisphere, describe the motion of water in it, e.g. " it flows
southwest, then west, then"



In other words, the direction of the current is constantly

turning. Going with the current, which way is it turning, toward the right or toward the left ?



The effect of the earth's rotation tends to turn, or deflect, all moving bodies toward the right in
the northern hemisphere. Study the eddies in the southern hemisphere, and state in which way

the currents are deflected in that hemisphere.



Warm and In the northern hemisphere, is a current from the south warm or cold, as compared

cold cur-
rents.

to the ocean water on either side of it?

How about a current from the north ?

Is the Labrador current cold or warm? "

The Gulf Stream? The west wind drift?

Which side of the North Atlantic has the

warmer water, the American or the European? ___.

Locate cool currents in the southern hemisphere and state their position and cause.



What effect on the temperature of the tropical oceans must the movement of ocean currents

have?

What effect on the temperature of the Arctic regions must the movement of the ocean currents

have?

243



Currents from which ocean, the Atlantic or Pacific, have the greatest effect on the Arctic ?

Trace the southern limit of icebergs in the North

Atlantic. On which side does the ice float farthest south?

Explain this. *<



Of what importance is the fact that icebergs come down across the path followed by the
transatlantic steamers ?



Fogs are caused by damp winds blowing from warm to cool regions. Knowing this, and
by the aid of the ocean current chart, explain why the ocean near Newfoundland is one of the

foggiest places on the earth.



Effect of Why cannot the ocean currents themselves affect the temperature of the land ?

ocean cur-
rents on
the temper-

the land What must help to carry their influence to the land?

What is the prevailing wind direction in the British Isles? 1

State why the climate of the British Isles is much warmer than that of southern Labrador,

which lies in the same latitude.



Are east winds on the coast of New England warmed or cooled in passing over the adjacent

ocean current ? How about winds from the

south in the New England region? State as

fully as you can how the ocean currents influence the climate (a) of northern Europe ;

244



(b) northeastern United States ;



and (c) northwestern United States and Alaska.



On the blank chart (Fig. 23) sketch from memory the great eddies and the principal
currents of the oceans, giving their names.



245




247



LVIL — TIDES

Purpose. To study the rise and fall of the tides at a given place in order to learn the time between

tides, the variation in height of tides, and their relation to the moon's phases; also to learn the
cause of tidal currents.







TIDES AT EASTPORT, ME.


, SEPTEMBER






High Tides




Low


Tides




a.m.


P.M.


A.


M.


p


M.


Date


Time


Height in Feet


Time


Height


Time


Height


Time


Height




h. in.




h. m.




h. m.




h. m.




1


2.01


18.6


2.25


18.7


8.10


-0.2


8.41


-0.5


2


2.54


17.8


3.14


18.0


9.01


0.7


9.38


-0.1


3


3.50


17.0


4.15


17.4


10.00


1.5


10.40


0.7


4


4.52


16.3


5.19


17.0


11.03


2.0


11.46


0.9


5


6.00


16.0


6.26'


17.1






12.11


2.1


6


7.08


16.1


7.31


17.5


0.54


0.7


1.18


1.8


7


8.11


16.8


8.32


18.2


1.56


0.2


2.21


1.1


8


9.08


17.6


9.28


19.0


2.55


-0.5


3.17


0.1


9


9.59


18.3


10.18


19.4


3.45


-1.2


4.08


-0.6


10


10.43


19.0


11.04


19.7


4.34


-1.5


4.54


-1.2


11


11.27


19.3


11.48


19.5


5.16


-1.6


5.37


-1.4


12






12.08


19.2


5.58


-1.4


6.20


-1.3


13


0.30


19.0


12.49


18.9


6.38


-0.8


7.02


-0.8


14


1.12


18.3


1.30


18.2


7.18


0.0


7.43


-0.1


15


1.54


17.4


2.12


17.4


8.00


1.0


8.28


0.7


16


2.38


16.4


2.56


16.6


8.42


2.0


9.15


1.5


17


3.25


15.5


3.43


15.9


9.30


2.9


10.07


2.2


18


4.16


14.8


4.37


15.3


10.23


3.6


11.02


2.5


19


5.12


14.4


5.34


15.1


11.21


3.9


11.58


2.6


20


6.10


14.4


6.31


15.4






12.20


3.7


21


7.08


15.0


7.26


16.0


0.55


2.2


1.16


3.1


22


8.00


15.9


8.18


16.9


1.48


1.5


, 2.11


2.1


23


8.48


16.9


9.07


17.9


2.38


0.7


2.58


1.0


24


9.32


17.9


9.53


18.8


3.22


-0.2


3.44


-0.1


25


10.16


18.9


10.38


19.4


4.08


-1.0


4.27


-1.1


26


10.59


19.6


11.22


19.7


4.49


-1.5


511


-1.8


27


1142


20.0






5.31


-1.7


5.55


-2.1


28


0.08


19.8


12.26


20.0


6.15


-1.5


6.41


-2.1


29


0.54


19.6


1.13


19.7


7.00


-1.0


7.30


-1.7


30


1.42


18.9


2.04


19.1


7.48


-0.3


8.23


-1.1



249



Figure 24 is a diagram showing the rise and fall of the tides at Eastport, Me., for the
first 15 days of September during a certain year. At the top of the diagram, the figures 12,
6, 12, 6, 12, etc., represent hours of the day, the first 12 being midnight, the second 12 noon,
the third 12 midnight again, etc. The first 6 is 6 o'clock in the morning; the second 6 is-
6 p.m. Each of the vertical lines of the cross-section paper represents two hours of time. On
the right and left margins the figures 0, 5, 10, 15, 20, etc., represent feet ; and each horizontal
line of the cross-section paper stands for 1 foot. The zigzag line represents the rise and fall
of the tide for the first 15 days of the month. Study this diagram until you understand it.
Notice, for example, in the tide table for this month, printed below, that the first high tide
of Sept. 1 came at 2.01 a.m., and reached a height of 18.6 feet; the second high tide
came at 2.25 p.m., and reached a height of 18.7 feet; the first low tide came at 8.10 a.m.
and its elevation was —0.2 foot; the second low tide, at 8.41 p.m., stood at — 0.5 foot. In
making the diagram, four dots were placed in the proper positions under Sept. 1, two for
the high tides and two for the low. These were then connected by the lines. The same pro-
cedure was followed for each of the other days.

In the table on page 467 are data for the completion of the diagram (Fig. 24). Place dots
in the proper positions for the last fifteen days of September, and then connect them with lines.
You then have a diagram showing the rise and fall of the tides at one place for a month.



How many high {flood) and low (ebb) tides are there each day ?

From the table, determine the exact length of time between flood and ebb tide on a certain

day. - Between ebb and flood tide.

. Between two successive flood tides.



Between two successive ebb tides.

Between the flood tides of successive days.



If the flood tide were to reach its greatest height at 12 o'clock, noon,

on Sept. 10, at what time (approximately) would it reach its greatest height on Sept. 11 ?



On Sept. 15 ?



Height of What is the range (in feet) between the high and low tide on Sept. 1 ?

the tide.

Find a day in which the range is greater than this.



Find one in which the



range is less.



How many periods of high range of tide are there in this month ? ___

How many of low range of tide ?

Between what days of the month is the tidal range high?



250



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251



§



Between what days is it low ?



moon?



Which two of these periods correspond with new and full



quarters of the moon ?



Which two with the first and last



Which of these are

the spring tides (see Text-book, p. 189)?

Which are the neap tides?

Are the sun and

moon more nearly in line at new and full moon, or at the quarters ?

What does the relation between moon and tidal range suggest as to

the cause of tides?



Tidal cur- The tide causes a gradual rise and fall in the level of the ocean. It is essentially a ver-

rents. tical movement ; but under some conditions the tide causes horizontal movements, which are

called tidal currents. (Text-book, pp. 187-189.) In the diagram (Fig. 25) the tide rises 4.6 feet

on one side of the island, and 4 feet on the other side. What will be the movement of water



through the strait (s) at high tide ?



If the tide rose to a height of 4 feet on both sides of

the island, but high tide came a half hour later on one side than on the other, what would be



the result in the strait (s) ?







253




Fig. 25. — To show Differences in Height of Tide at Different Points.
How would such tidal currents affect the movements of ships ?



The transportation of



sand and other sediment?



When the currents move swiftly, they can carry much sedi-
ment. What must happen when the current is checked ?



254







Materials.



Purpose.

The air has
substance.



THE ATMOSPHERE
LVIII. — THE ATMOSPHERE HAS SUBSTANCE AND WEIGHT

For Each Student. — A drinking glass. A piece of candle.

For General Class Use. — Air pump. A glass cylinder open at both ends. A glass tube 35 inches
long sealed at one end. A bottle of mercury. A glass funnel. A ruler.

To show that the atmosphere Jias substance and weight; also the principle of the barometer.

What resemblance is there between a balloon floating in the air and a boat floating on the

water? :



Why does the balloon float?



What is the difference between water and air to sight ?



Could a bird fly if the air were not a real substance? Could a sailboat

move along? Would a windmill be turned?

Give other proofs that the air is something real.



The air is What takes place when a match burns?

a mixture

of gases. ^



Would it burn more or less rapidly if the air were all oxygen?

All carbon dioxide ? Light a small piece of candle, and over it set

an upturned glass. Note what happens. T



255



Explain why the candle light went out.



Why is a lamp chimney made with an opening at both the top and bottom ?



Make a list of the other substances of which the air is composed. (Text-book, p. 229.)



The air Why must all substances on the earth have weight '

has weight.



Why, then, must the atmosphere also have weight ?



Place a glass cylinder, open at both ends, on the air pump. Press the palm of your hand on
the upper end of the cylinder. Pump out the air from beneath your hand. What is the effect of



the air above your hand '



Why do you not ordinarily feel the weight of the air?



How much Two members of the class perform this experiment, the others watching closely and

the air answering the questions below. One of the experimenters stands the glass tube on its closed

weighs.

end. What fills the tube? The other experimenter carefully fills

the tube with mercury, using the glass funnel. What now fills the glass tube ?

256



Into a drinking glass pour mercury enough to fill it to a depth of two inches. The student
holding the glass tube now puts his thumb firmly over the open end of the tube, turns the
tube upside down, thrusts the end beneath the mercury in the glass, and then removes his

thumb. What happens ?



The other experimenter next measures the height of the mercury in the tube, measuring from
the surface of the mercury in the glass. How many inches long is the column of mercury ?

What is above it? Why does the mercury

not drop out of the tube?



The result would have been the same if the tube had been a foot square, or an inch square,
or any size. Fill out the following sentence. The weight of a column of air is equal to the

weight of a similar column of mercury inches high. A column of

mercury 1 inch square at the base and 1 inch high weighs approximately \ pound. How much

would a column of mercury 1 inch square and 30 inches high weigh ?

How much, then, is the weight of a column of air 1 inch square?

Fill out the following sentence. The pressure of the atmosphere is equal to

pounds on every square inch.

The barom- The apparatus just used is a rough form of barometer. Could water or other liquids be

eter.

used in a barometer? If water were used, would the column in the tube be


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