Geography - The Earth As A Planet
( Originally Published 1915 )
IN ADDITION to the daily rotation of the earth on its axis, the earth has another motion. What is it? It has this motion round the sun in common with the other planets of the solar system.
How long does it take the earth to make one revolution round the sun? It takes it almost 3651 days. What name is given to this interval of time? Why is every fourth year made a "leap year"? If you are given the number designating the year, how can you tell whether it is a leap year or not? If the number is divisible by four, it is called a leap year. What exception is there to this general rule? The last year of a century is not considered a leap year unless its designation number is divisible by 400. For example, of the years 1600, 1700, 1800, and 1900, only the year 1600 was a leap year. The year 1896 was a leap year; the next leap year was 1904, after an interval of eight years. What is the reason of this? The sun year is a little less than 3651 days, and unless three leap years were dropped every four centuries, our time would get faster than the sun time.
THE EARTH'S ORBIT
The pathway on which the earth is supposed to travel round the sun is called its orbit. It is almost, but not quite, a circle; it is a sort of flattened circle. Make a drawing of it on the black-board, and mark the sun a little to one side of its centre. Note that this will bring the earth a little nearer to the sun at certain times of the year than at others. Strange to say, the earth is nearer the sun in winter than it is in summer. It is the slanting rays of the winter sun that counteract this advantage. Perhaps you have noticed that the sun appears somewhat larger in mid-winter than it does in midsummer.
What is meant by the plane of the earth's orbit? A very clear notion of it may be obtained by imagining the sun to be a large, stationary buoy floating, half submerged, on the surface of a perfectly smooth sea. Then imagine the earth to be a ball, also half submerged, floating swiftly in a circle round the sun-buoy. This circular pathway will represent the earth's orbit, and the surface of the water will represent the plane of the earth's orbit. Note that the orbit lies on this plane all the way round and that the plane cuts the earth into halves.
THE INCLINATION OF TIIE EARTH'S AXIS
The earth does not move round the sun with its axis straight up and down. It is tilted a little, so that it is always inclined about 23i degrees from the upright position. Draw an upright line on the black-board; draw another line inclined to it so that the angle between them is 23 1/2 degrees—a little larger than one quarter of a right angle. As the earth moves round the sun, this inclination makes the axis always point toward the North Star. (See diagram, page 11, Text-book.)
VARIATION IN THE LENGTH OF DAY AND NIGHT
Take a small globe on which are represented the poles, the equator, and a few circles parallel to the equator. Do not forget that the earth's axis always points to that part of the heavens where the North Star is, and that the earth turns on its axis always from west to east, the direction indicated by the equator and the circles that are parallel to it. Hold the globe in front of a lighted candle. How much of its surface is lighted up? How much of it is in shadow?
Cut a hole, the size of the globe, in a piece of card-board, insert the globe, and hold it in such a way that the lighted half of its surface is on one side of the cardboard and the shadowed half on the other side. The line where the cardboard and globe meet will represent the circle of illumination. (See diagram, page 13, Text-book.) Place the globe so that its poles are equally distant from the candle. Note that when the globe is in this position the circle of illumination passes through the poles. Why is this?
Examine the circles on the globe that are parallel to the equator. What part of each of these circles is in candle-light? In shadow? One half of each circle is in candle-light and the other half is in shadow. Locate on the globe a circle-about half-way between the equator and the north pole. This circle will indicate, approximately, the distance that we are north of the equator. Mark a point on this circle; keeping the globe in the cardboard, rotate it once at a uniform rate before the lighted candle. How long a time is this point in candle-light? How long is it in shadow? Why is the time the same in each case?
This illustration should give us the explanation why day and night are equal in length when the poles are equally distant from the sun. Every twenty-four hours the earth turns on its axis once and carries us round with it in a circle. If the sun shines directly upon us for half of our daily circle-journey, and if we are in the shadow of the earth for the other half, it follows that there must be twelve hours of day followed by twelve hours of night. This happens twice every year—at the Spring and the Autumn equinoxes.
Next, place the globe in the cardboard so that the north pole is tilted toward the candle. How much of the circle is now exposed to the candle-light? How much of it is on the shadowed side? Measure accurately. If, say, five eighths of the circle is in candle-light and three eighths of it in shadow, and if the globe is rotated once at a uniform rate, it follows that the marked point on the circle will be in the light five eighths of the time and in shadow three eighths of the time.
If these conditions apply to the earth and sun, then, during one circle-journey around the earth, we shall be in direct sunlight for fifteen hours (that is, five eighths of twenty-four hours) and in the shadow of the earth for nine hours. This happens on or about June 21st every year.
Similarly, when the north pole is turned away from the sun, we have short days and long nights. Of course all the above changes take place gradually as the earth revolves about the sun. We referred to this, if you remember, in our observations in connection with " The Seasons ", (see page 71).
We have here the explanation of the facts learned in connection with the observation lesson on the " Variation in the Length of Day and Night" (see page 75). The sun appears to us to move in a great circle around the earth. The arc traced by the sun in the sky in the day-time on or about June 21st forms more than half of this imaginary sun-circle, and the day is therefore longer than the night. On or about December 21st the arc is less than half the sun-circle and the day is therefore shorter than the night. On or about March 21st and September 21st the arc is half of the sun-circle and therefore the day and night are equal in length.
We know that the sun does not really move round the earth. The observations referred to above, as well as those made in connection with the lesson on " The Earth's Rotation" (see page 92), show us that it is we who are journeying every day, while the sun is shining upon us, from the place from which we see the sun rise to the place from which we see it set. It is the rotating earth that is carrying us round in a circle once every twenty-four hours past the stationary sun. The moving of the sun across the sky is only an illusion, like that of the moving fence and trees seen from the window of a fast railway train.
THE CAUSE OF THE SEASONS
If the earth always moved round the sun with its axis straight up and down, the sun's rays would always shine upon the earth with exactly the same degree of slant ; that is, the shadows cast by the sun would always be exactly the same in length. There would be no lengthening of shadows as winter approaches, and no shortening of them as summer draws near.
Again, if the earth's axis were straight up and down, there would be no variation in the length of day and night. Every place would always have twelve hours day and twelve hours night, and the amount of heat that any particular place would receive would be practically the same all the year round. In other words, there would be but one season, not four, during the year.
You will thus see that the real cause of the seasons must be the inclination of the axis of the earth. Since the axis always points toward the North Star, it follows that, as the earth journeys round the sun, each pole is in the sunlight for six months, and then in the shadow of the earth for the remaining six months of the year. Illustrate this by means of a hat-pin and an apple.
Show that, when the earth's axis has its greatest inclination toward the sun, the latter's vertical rays will reach their farthest point north, namely, on the Tropic of Cancer; this takes place on or about June 21st, and gives us the longest day in the year. Show also that, when the axis has its greatest inclination away from the sun, the latter's vertical rays will reach their farthest point south, namely, on the Tropic of Capricorn; this takes place on or about December 21st and gives us the shortest day in the year.
When the sun is over the Tropic of Cancer, it is high up in the sky and its rays give us summer's heat; but when the sun is over the Tropic of Capricorn, it is low down in the sky and its rays contain so little heat that we have winter's cold.
The tilting of the earth to, and away from, the sun, will explain why the sun appears to change its position in the sky to the south of us, being high up in summer and low down in winter. (See page 73.) Why have we winter when the sun's rays are most slanting, and summer when they are nearly vertical? It is because the sun's rays not only pass through the thicker layer of air, but also because they spread themselves over a greater area of surface than the more vertical rays do. Illustrate both of these factors by diagrams on the black-board.
Note that the most slanting rays are accompanied by the shortest days of sunlight, and that the nearly vertical rays are accompanied by the longest days of sunlight.
Note, too, that twice during the year, as the earth is revolving round the sun, the two poles are equally distant from the sun. It is at these times we have the equinoxes equal day and night. Make further use of the apple and hat-pin and of black-board diagrams until the succession of the seasons is clearly understood. (See diagrams, pages 14-15, Text-book.)
Thus we find that the causes of the seasons, which were deduced from observations that were made of the sun's shadows throughout the year (see pages 69-75), are now explained.
LATITUDE AND LONGITUDE
MEASUREMENT OF CIRCLES
Draw a circle on the black-board. What is a circle? In geographical language, a circle is an endless line drawn around a point, and always the same distance from that point. That point is called its centre.
Every circle, whatever its size, is supposed to be divided into 360 equal parts which are called degrees. Each degree is again divided into 60 minutes; and each minute into 60 seconds.
The earth's equator is a great circle. What is its centre? What is the length of the equator? How many miles long is a degree at the equator? 25000 miles - 360 = 69i miles, nearly. How many miles are there in one minute? What name is given to a straight line drawn from one part of the equator through the centre of the earth to the equator on the opposite side of the earth? How long is this diameter? What name is given to a straight line from the surface of the earth to its centre? How- long is it?
How many degrees are there in the circumference of the earth? Why? How many degrees are there between the two poles? Why? How many degrees are there between the equator and either pole? Why?
Repeat the table for circular measure.
There are 60 seconds (") in 1 minute ("),
60 minutes in 1 degree ("), and 360 degrees in 1 circle.
Illustrate by circles drawn on the blackboard.
HOW TO LOCATE A POINT
Mark a point on a blank black-board. How can the location of this particular point be determined? Can it be located by saying that it is a certain distance from the top of the black-board? Why not? This does not locate it definitely, because each of a whole series of points extending across the black-board from end to end may have its location thus described. What other factor is necessary in order to locate exactly the given point? It will be necessary to state its distance from the end of the blackboard. If, for example, we say that it is two feet five inches from the top of the board and four feet ten inches from its end (left), we know the exact location of it and that no other point on the black-board can have this location. Note that the top and the end of the board are really two lines at right angles to each other and that the given point lies between them.
Locate definitely a point marked at random on a blank page of your scribbling book. Note that the two edges of the page, from which the measurements are made, form two lines at right angles to each other and that the given point whose location is sought lies between them.
Similarly, it may be shown that any point on a surface can be readily located provided that it lies between two lines that are at right angles to each other. Illustrate this by one or two examples on the black-board.
An application of this principle is seen in the location of farms in a township. (See lesson on " The Township ", page 79). Locate, for example, the farm known as "Lot 12, Con. 7 ". Why are you sure that you have correctly located it? It is situated on the seventh concession numbered from the town line at one side of the township, and it is on the twelfth lot numbered from the town line at one end of the township. These town lines are really two lines at right angles to each other, and the farm located lies between them.
LATITUDE AND PARALLELS OF LATITUDE
How are places located upon the earth? Place a chalk mark upon the surface of the school globe. Can you describe accurately its location? Why is it difficult to do this? Let us look for two lines at right angles to each other between which is the point marked.
In measuring distance north and south on the earth, it has been agreed to take the equator as the starting-place. On which side of the equator is the point that was ,marked? How far is it from the equator? The distance north or south of the equator is measured, not by miles, but by degrees, each of which is, as we have seen, almost seventy miles. How many degrees are there between the equator and the poles? To make the measuring easy, circles are drawn around the earth parallel to the equator; the distance between these circles depends upon the scale on which the map is drawn. (See diagrams, page 17, Text-book.) What is the distance in degrees between these circles on your globe? On the map of the world? On the map of North America? On the map of Canada? On the map of Ontario? With the help of these circles, calculate, in degrees, how far London (England), Mont-real, New York, Calcutta, etc., are north of the equator. Practise exercises like this on the globe and on the maps of the continents.
The distance of any place from the equator in degrees is called its latitude. The degrees in latitude never vary in length. Why not? The circles that help in marking the latitude are called parallels of latitude. What is meant by north latitude (N. Lat.) ? By south latitude (S. Lat.) ? What is meant by saying that Petrograd is in sixty degrees N. Lat.? That London (Ontario) is in forty-three degrees N. Lat.? That Rio de Janeiro (Brazil) is in S. Lat. twenty-three degrees? Drill thoroughly on various maps until you can readily determine the latitude of places in any part of the world.
MERIDIANS AND LONGITUDE
Just as it is necessary to have a line (the equator) as a starting-place for measuring distance north and south, so it is necessary to have a line for a starting-place when measuring distance east and west on the earth. In what direction must this line run? Why must it run north and south?
When measuring east and west, it has been agreed to take a meridian line for the starting-place. What is a meridian line? It is a line upon which the sun's shadow falls when it is noon. Where is our meridian or noon line? It is the line drawn north and south through the noon shadow cast by the stake in the school yard. (See lesson on " Seasons ", page 70.) How long is this meridian line of ours? We may imagine it to extend north to the North Pole and south to the South Pole; in other words, our meridian is a north-and-south noon line that is supposed to run from pole to pole passing through here on its way. Since the sun crosses this line every day at noon, it follows that every place on it will have noon at exactly the same time that we do. What other places have meridians? Every place must have its own meridian. Why? What is Toronto's meridian? Keep in mind that meridians are north-and-south noon lines ; and note that they cross the equator at right angles (what does this mean?), and that they are really semicircles meeting at the poles. (See diagram, page 317, Ontario High School Physical Geography.) Why are they semicircles?
It is the meridian that passes through London (England) that has been agreed upon as the starting-place for measuring distances east and west on the earth. It is for this reason that it is called the First Meridian. Find it on the globe and on the map; you will find it marked.
Distance east or west of the First Meridian is called longitude; it is always expressed in degrees. What does west longitude (W. Long.) mean? East longitude (E. Long.) ? If two persons leave Greenwich at exactly the same time and travel at exactly the same rate, one going east, the other west, where will they meet? They will meet half-way round the globe—at 180 degrees of longitude, that being half of 360 degrees. Find the 180th meridian on the map or globe.
Now, just as parallels of latitude were drawn at certain intervals to help in measuring distance north or south of the equator, so meridians are drawn at certain intervals to the east and west of the First Meridian to help in measuring distances east or west, the intervals depending upon the scale on which the map is drawn. The measurements in degrees are made along the equator. (See diagram, page 13, Text-book.)
What names are given to the different meridians? The one that crosses the equator 5 degrees west of the First Meridian is called the 5th meridian W. Long. What is the name of the one that crosses the equator 30 degrees east of the First Meridian? Is the 180th meridian in W. Long. or in E. Long.? As it is the same distance to the east or to the west of the First Meridian, it is simply called the 180th meridian. What group of islands in the Pacific Ocean is crossed by this meridian? If meridians cross the equator at intervals of one degree, how many of them are there between the First Meridian and the 180th? Note that these meridians are farthest apart at the equator and that they meet at the poles. The length of a longitude degree therefore varies. It is greatest at the equator (almost 70 miles) ; at the poles its length is 0. Except in a few cases which need not be considered here, the latitude degree, as already noticed, never varies in length; it is always approximately 70 miles. Drill thoroughly on various maps until the pupils can readily determine the longitude of places in all parts of the world. (See diagram, page 13, Text-book.)
LATITUDE AND LONGITUDE
Where do East Longitude and West Longitude meet? They meet, as already noted, at the 180th meridian. Into how many sections, therefore, is the earth's surface divided by the equator and the First Meridian? What are they? They are: (a) That part of the earth north of the equator and west of the First Meridian as far as the 180th meridian. (b) That part north of the equator and east of the First Meridian as far as the 180th meridian. (c) That part south of the equator and west of the First Meridian as far as the 180th meridian.
(d) That part south of the equator and east of the First Meridian as far as the 180th meridian.
Locate these sections on the globe and note that each forms one quarter of the earth's surface. Name and locate on a map of the world important countries, cities, etc., in each section. Note that any place in any of these sections lies between two lines that are at right angles to each other. What are these lines in each of the four sections? They are the equator and the First Meridian.
Find, for example, the situation of Winnipeg. Measure in degrees how far it is north of the equator. It is 50 degrees. Next, measure in degrees how far it is west of the First Meridian. It is about 97° degrees. What, then, is the location of Winnipeg? It is approximately in N. Lat. 50° and W. Long. 97°.
Note that this method of locating Winnipeg is the same as that used in locating a point on the blackboard or on the blank page of an exercise book. It is also the same method as that used in locating farms in a township.
A ship is reported by wireless telegraphy to be in distress in N. Lat. 36° 25' and W. Long. 48° 40'. Locate this point on the map as nearly as you can. Practise exercises such as this until you can, by using the map, determine the latitude and longitude of any place that may be named; or can locate approximately any point whose latitude and longitude is known.
LONGITUDE AND TIME
In what part of the sky do we see the sun at noon? Where do the people of Halifax see it when it is noon with them? When it is noon in Toronto, can it be noon at Vancouver at the same time? Why not? It is because the sun cannot be directly over the noon line at Toronto and at Vancouver at the same time. Different meridians have their noon at different times.
In what direction is the earth rotating? If it is rotating from west to east, which city will have sunrise earlier, Toronto or Halifax? Toronto or Vancouver? Why? Which of these will have noon first? Why?
Through how many degrees does a place pass while the earth makes one rotation? Explain this. How many hours does it take a place to pass through these 360 degrees? Through how many degrees does it pass every hour? How does this affect the time of places that have different noon lines, or meridians? There will be a difference in time of one hour for every 15 degrees east or west. If Halifax is 63° W. Long. and Peterborough 78° W. Long., what is the difference in their time? Which sees the sun rise first? When it is noon at Halifax, what time is it at Peterborough? When it is noon at London (England) what time is it at 15° W. Long.? At 15° E. Long.? At 30° W. Long.? At 45° E. Long.? At the 180th meridian? When it is noon at London (England), what is the time, respectively, at Naples, Petrograd, Manilla, Philadelphia, Denver, Fort William, and New Orleans? Consult the map. (See diagram, page- 13, Text-book.)
If you started at London (England) at noon and travelled westward, what change would you have to make in your time for every 15 degrees? Does the traveller going west gain or lose time? If he kept on travelling westward until he got back to his starting-place, how much time would he gain? Explain how he would gain a whole day of twenty-four hours. If he circled the earth, going eastward, how much time would he lose?
Suppose there are three men, A, B, and C : A stayed at home; B travelled around the earth, going westward all the way; C also travelled around the earth, going east-ward all the way. B and C started their journey from the same place and at the same time, and both returned at the same time. A says that they were away ninety days ; B maintains that he has been away ninety-one days ; while C maintains that he was eighty-nine days away. Not one of the three agree as to the intervening time. How would you explain their difficulty?
How do sea-captains and sailors overcome this difficulty and keep their time right? When they are crossing the Pacific Ocean and reach a line called the International Date Line, which is in the neighbourhood of the 180th meridian, they change their time reckoning exactly one day. For example, if they reach this line on their west-ward voyage on Saturday noon, they call it Sunday noon; but if they reach it on Saturday noon when east-bound they call it Friday noon. If B and C, in the illustration used above, had done this, their time would have agreed with that of A who stayed at home.
The greater part of Canada is situated between the 60th and the 135th meridians—a width of approximately 75 degrees. If there is a difference in sun time of one hour for every 15 degrees, what is the approximate difference in time between the Atlantic and Pacific coasts of Canada? Why does this make it difficult for transcontinental railways to arrange their time-tables. Travellers, too, would find a. difference in sun time of five hours rather inconvenient. Why?
To overcome this difficulty, Canada has been divided into five belts or districts whose width from east to west is, approximately, 15 degrees each. These belts are associated, respectively, with the 60th, the 75th, the 90th, the 105th, and the 120th meridians.
What is the difference in sun time between the First Meridian at Greenwich and the 60th meridian? The time at the 60th meridian is four hours slower than Greenwich time. Similarly, the time at the 75th, at the 90th, at the 105th, and at the 120th meridians is, respectively, five hours, six hours, seven hours, and eight hours slower than Greenwich time.
Note that the time belts are so arranged that their boundaries are largely provincial. (See Text-book.) The Maritime Provinces are associated with the 60th meridian; Ontario and Quebec to the Great Lakes, with the 75th; Western Ontario and Manitoba, with the 90th; Saskatchewan- - and Alberta, with the 105th; and British Columbia with the 120th. By this arrangement the time in Ontario is one hour slower than that of the Maritime Provinces; Manitoba's time one hour slower than that of Ontario; etc.
When it is 12 o'clock noon at London (England) what time is it in the Maritime Provinces? In Ontario? When it is noon in Ontario what time is it at Halifax, Winnipeg, Regina, Calgary, and Vancouver, respectively? When the Ontario schools are being dismissed at 12 o'clock noon, what is probably taking place in the schools of British Columbia? Why?
CONTINENT STRUCTURE ORIGIN OF CONTINENTS
The story of the origin and growth of continents is a very interesting one. The secret was discovered by men called geologists, who have made a very careful study of the rocks; and, although they have not yet been able to learn many of the details, enough is now known to make the story a probable one.
These geologists tell us that ages and ages ago the earth mass was much warmer than it is now and that it has been gradually cooling off. They also tell us that its rock surface was much more uniform ; that, comparatively speaking, its ridges were not so high nor its depressions so deep as at present. Hence the oceans at that time were probably more extensive in area but not so great in depth as our oceans are. As the earth gradually cooled, it gradually shrunk in size, just as most substances do when cooling. As this shrinking process continued, the rock surface of the earth became more and more folded into higher ridges and lower depressions, in much the same way that the skin of a hot, baked apple does when cooling.
In course of time the folds, or ridges, gradually rose higher and higher above the surface of the shallow ocean, carrying up with them broad ocean-bottom plains that were lying at or near the surface. These ridges, with the low adjoining plains, formed the beginning of the continents, as we now know them. In the meantime the waters of the shallow ocean gradually withdrew into the deeper depressions that were being formed in the underwater rock surface. In this way the oceans, as we now know them, began to form.
It is believed that the land surface of the earth is not yet stationary; that it is still rising in places and sinking in others; and that this rising and sinking is taking place so gradually that centuries may pass before the results are noticeable. It is believed too, that the general out-lines of the continents as well as their characteristic surface features are, in the main, the direct result of this undulatory movement of the earth's crust.
Not only have the surface features of the continents been greatly changed by the earth's contraction forces, but they have been further modified by the erosion work of rivers and other agencies that have cut deeply into the rock surface; depressions thus formed vary in character from the steep-sided gorge to the deep, broad valley. The sea bottoms, on the other hand, not being subject to such erosion-forces, are likely to have surfaces much more uniform in character. This is probably why a sinking coast region is likely to produce a broken shore-line; and a rising coast region, a comparatively unbroken shore-line.
The above theory will account for the broken shore-lines of the northern half, as well as for the comparatively unbroken shore-lines of the southern half of the North American continent. (See " Shore Forms of North America ", page 103.)
According to geologists, the northern coast regions of North America have been gradually sinking, until the sea has at length entered the river mouths and valleys, forming many harbours, bays, etc. ; while the higher land forms still remain above water, forming peninsulas, capes, islands, etc. Thus Newfoundland Island, the Gulf of St. Lawrence, the wide mouth of the St. Lawrence River, Belle Isle Strait, the Nova Scotian Peninsula, the Bay -of Fundy, as well as the many other shore forms found along the coasts of Canada—east, west, north—have been caused or have been greatly modified in this way.
On the other hand, the theory suggests that the rising of the more or less uniform sea bottoms contiguous to the original shore-line will explain the almost unbroken shore-lines of the southern half of the continent. If the south-eastern, southern, and western coasts of the United States and the coasts of Mexico and Central America are care-fully examined on a wall map of North America, comparatively few harbours and other shore forms will be found.
Experiment : In a deep tray make a plasticfne model of North America; surround the model with an evenly-sloping margin to represent the sea bed contiguous to the shore-line; pour sufficient water around the model to reach the shore-line; and then tilt the tray slightly so that the end representing the north is lowered and the other end raised. What is the result? How does this experiment help to explain the character of the North American coast-lines?
The pupils of this Grade have already studied the general features of North America and should, therefore, be familiar with its highlands, slopes, plains, and river basins. If North America has been well taught, the knowledge obtained and the method followed should serve as a guide in the teaching of the other continents.
Review the three highlands of South America, the continental axis, the chief river basins, and the regular coast-line. (See Relief Map, page 225, The Story of the Earth and Its Peoples.) The South American coast regions have been rising and are unbroken because the level sea bottoms are being raised. There is, consequently, a general absence of good, natural harbours. This is particularly true of the Pacific coast. What effect must this have upon the development of the continent ?
Physically Europe and Asia form a single continent, called Eurasia; but as Europe has so long been considered a continent by itself and has been so long regarded as the home of the civilized races it is usual to consider it separately.
What is its area? It has the longest coast-line in proportion to its area of any of the continents. Verify this statement. Why is the coast-line so much broken? Its shores, especially in the north and west, have been sinking thus forming many inlets. The Baltic Sea and its gulfs are old land valleys that have been submerged. Name a few of the other inlets on these coasts. In Southern Europe the rising and sinking of the land areas, while the mountains were forming, has made many peninsulas, seas, etc. The Mediterranean Sea occupies a deep depression formed by the sinking of the earth's crust. Locate on the map of Europe the chief coast features of the Mediterranean. What effect has Europe's much broken coast-line had upon its development as a continent?
What is the primary highland of Europe? The Alps and associated mountains. Note that the Alps Mountains form a hub, as it were, from which radiate minor -ranges in all directions. Name and locate them. This system of mountain ranges has more or less isolated many areas of Europe from one another. What results have such physical barriers had upon race and language development? Give instances. Trace the continental axis of Europe from Cape Finisterre ("End of the Land") over the Cantabrian, the Pyrenees, Alps, Dinaric Alps, and Balkan Ranges to the Dardanelles. The Caucasus Range seems to be a continuation eastward of the Carpathian Mountains, from which it is separated by a depression (Black Sea). The Alps and associated highlands form the great plateau region of Central Europe. What important rivers flow from this plateau? What branch of the Alps extend south into Italy? (Study Relief Map, page 297, The Story of the Earth and Its Peoples.)
What mountains form a secondary highland? The Scandinavian Mountains. What great lowland plain' lies between the primary and secondary highlands? Note its great extent—from the Atlantic to the Ural Mountains. Trace the drainage divide that separates it into two slopes; one, sloping north-west to the Arctic and Atlantic; and the other, south-east to the Caspian and Black Seas. What are the chief rivers in each slope? Note that the waters of the Black Sea Basin force their way through the continental axis at the Bosphorus (Ox-ford) and the Dardanelles.
Owing to its inaccessibility, comparatively little is known of the mountain system of Central Asia. - We know that there is a great mass or knot of mountains north-west of India called the Pamirs ("Roof of the World ") from which, like the Alps in Europe, radiate ranges in various directions. The Himalayas, Kuen-lun, and Tian-Shan extend eastward ; the Hindu Kush westward ; and the Sulaiman southward. Locate these ranges.
The Himalayas (" Abode of Snow") separate India from Tibet. They contain forty peaks that rise more than 24,000 feet above the sea-level, one of which is the highest in the world. What is its name? How high is it?
The Kuen-lun Mountains separate Tibet from Chinese Turkestan and Mongolia. Though its crests are not so high as those of the Himalayas, this range surpasses them all in average altitude and is, on the whole, the most elevated on the earth. Between the Himalayas and the Kuen-luns is Tibet, the greatest plateau in the world; its average elevation is almost as high as the highest peak (Mount Blanc) in the Alps.
The Tian Shan (" Sky-Mountains ") separate Turkestan from Chinese Turkestan, and are continued eastward as the Altai Mountains. Inclosed between the Kuen-luns on the south, the Altai on the north, and the Great Khingan Range on the east, lies the vast Gobi Plateau, (lower than the Tibet Plateau) the most of it a desert of sand and mountains. North-east of the Altai are the Yablonoi and beyond these the Stanovoi range extending to Bering Strait. These mountains are in detached masses and must not be considered a continuous range.
The continental axis of Asia extends from the Dardanelles to Bering Strait, and is believed to lie along the following mountain ranges ; Taurus, Elburz, Hindu Kush, Pamir, Kuen-lun, Great Khingan, Yablonoi, and Stanovoi. At the Dardanelles it connects with the continental axis of Europe—making an almost continuous axis of 10,000 miles, extending from Cape Finisterre to Bering Strait; this is nearly as long as the continental axis of North and South America taken together. (Consult Relief Map, page 349, The Story of the Earth and Its Peoples.)
Asia presents many striking surface contrasts. It has, as we have learned, the greatest heights in the world; it has also the most deep-sunk depressions. It has the most elevated table-lands and the lowest plains. The deepest depression in the world is the valley of the Dead Sea, which is 1,312 feet below the sea-level.
The Arctic coasts of Asia are similar to those of North America and have had a similar origin. How were they formed? They are inhabited only by fur-bearing animals and sea-birds. The east, south, and west coasts of the continent' are much broken by peninsulas, seas, gulfs, etc. The peninsulas are formed by mountain spurs or high-lands extending oceanward. While these peninsular high-lands were rising, corresponding depressions were forming beside them. Why should we expect this? These depressions have become seas, gulfs, etc. What is the relation of the capes of Asia to these peninsulas? Note that Arabia is the, largest peninsula in the world.
What islands of Asia are continental in their origin? What evidence have we that the Japan Islands are formed by a range of mountains rising from the bed of the ocean? Why are earthquakes so frequent in Japan? Is it be-cause, the mountains are still growing? Why should this cause earthquakes? When we hear of earthquakes taking place in various parts of the world—some of them very destructive, others scarcely perceptible—is it a sign that the earth mass is still contracting in bulk? Why do you think so?
The plains of Asia are all on the outer borders of the continent? How would you account for this? All the great rivers of Asia have their source in the table-lands and mountains of the interior. Locate the chief plains and the rivers that flow through them. What rivers have formed great alluvial plains that are supporting dense populations? So extensive are the alluvial plains formed by the rivers of India (Ganges, Brahmaputra, Indus), that it is said that one may travel from the mouth of the Ganges in a north-westerly direction to the Punjab without seeing a pebble as large as a small marble. The " stone-mills" in the mountains seem to be doing their work well. Explain. It is said that " Asia is the home of the twin-streams ". Locate the Hwang-Ho and Yangtsekiang, Ganges and Brahmaputra, Tigris and Euphrates, Sir and Amu. Locate the Mekong River. This river is 2,600 miles long and is said to have the largest volume of any river in Asia. How would you account for this? (Consult the Rainfall Map on page 40 of Text-book.)
Why is Africa called the "Dark Continent"? Give two reasons. Africa has no continental "backbone ". What does this mean? It has no great mountain ranges in the interior. Africa is a great plateau continent. Why? It is walled in by a rim of mountains or high-lands round the edge and parallel with the coast. Trace this rim on the map, noting the following mountains : Atlas, Kong, Kamerun, Drakenberg, and the Abyssinian Plateau culminating in the south in Mounts Kalimanjaro and Kenia. (Consult Relief Map on page 440, The Story of the Earth and Its Peoples.) On the map on page 237 of the Text-book, trace the drainage divide from the Mediterranean Sea to the Cape of Good Hope. From this divide trace the drainage divide to Cape Guardafui, inclosing the headwaters of the Nile. A great part of Africa requires no drainage. Why not? Note particularly the Sahara and Kalahari Deserts. Locate on the map the following river basins : Nile, Niger, Congo, Orange, Limpopo, Zambesi.
What natural obstructions to navigation are found on these rivers? Where are these obstructions situated? Why are they situated there? What effect have these obstructions upon the development of the interior of the continent? Why has the absence of good harbours on the coast a similar effect?
This continent, like Africa, is a plateau surrounded by a rim of mountains and highlands with short slopes to the ocean. Its surface suggests a plate in form, since the low interior rises gradually to plateaus and mountains at the coast. The highest mountains are in the east and south-east near the coast. Tasmania is a continuation of the eastern highlands. What effect has each of the following factors upon the development of Australia :
1. The regularity of coast-line and the comparative
absence of good harbours?
2. The proximity of the mountains to the coast?
3. The absence of navigable rivers leading into the interior?
4. Its isolation from the rest of the world?
Give a reason for your answer in each case. (See Relief Map, page 416, The Story of the Earth and Its Peoples.)
After the pupils have mastered the preceding work on the continents, they should be ready to form a mental picture of the earth as a unit-body. Their minds, after a study of the parts comprising the whole, should now be prepared for a synthetic concept of the whole earth.
The questions that follow are intended merely as types. The teacher will, of course, supplement them to suit the needs of the class. A good device to increase the interest and at the same time to secure the necessary review drill is to encourage competition among the pupils by having geography matches either written or oral. Try it.
What lands slope to the Pacific Ocean? To the Indian Ocean? To the Atlantic Ocean ? To the Arctic Ocean?' To the Mediterranean Sea? To what oceans do the short continental slopes incline? Nearest to what ocean is the continental axis of North America? Of South America? Of Eurasia? How many outlets has the Arctic Ocean? How wide is Bering Strait? What effect has this narrow outlet upon the climate of the North Pacific Ocean? Why? At what points do the Atlantic and Pacific Oceans join? What ocean is widest from east to west? What indentation extends farthest into the land?
What highlands protect the continents from being worn away by the waves and tides of the ocean? What coast-lines have no such protection? What islands seem to have once been parts of Europe? Of Asia? Of North America? From what highlands were they broken off? What islands partially inclose seas or large gulfs and bays in Asia? In Europe? In North America? What continental slope is most broken by large inlets? What peninsulas extend in a northerly direction?
What ocean receives most water from the land? What continental slope furnishes most water to the Pacifie? What is the longest river in the world? The largest? Into what ocean do both these rivers flow? What is the longest river flowing into the Pacific Ocean? Into the Mediterranean Sea? Into the Indian Ocean? Into the Arctic Ocean? (Consult the Reference Tables in the Text-book.) What navigation difficulties are met with in the rivers flowing into the Arctic Ocean? In African rivers? With the exception of the Darling River, why is there an absence of great rivers in Australia?
What area of North America is not drained into the ocean? (The Salt Lake Basin) Of Eurasia? Locate these on the map. How is the greater part of the interior of Australia drained? What regions in Africa do not require drainage? Why not? What is the largest river in the world whose waters do not reach the ocean? Note that this river depends less upon mountains for its waters than any other great river in the world. What becomes of the waters that flow into the Caspian and Dead Seas? Why do they not fill up and overflow their banks? Are they likely to have underground connection with the Mediterranean Sea? Why not? They occupy depressions that are below sea-level.
Name in order all the mountains over which the continental axes pass from Cape Finisterre to Cape Horn, via Bering Strait. What mountains form the primary, or main; highland region in North America? In South America? In Europe? In Asia? In Australia? What is the highest mountain peak in North America? In South America? In Europe? In Asia? In Africa? In what continents do the continental axes extend north and south? East and west? What relation has the direction of the continental axes to the general direction in which the continents extend? What are the two secondary high-land regions of North America? The two secondary high-lands of South America ? What is the secondary highland region of Europe? In North America, South America, and Europe, locate definitely the broad plains between the primary and secondary highlands. What continents have broken coast-lines? Unbroken coast-lines? Which continents have been developed most? Which the least?
What relation is there between the character of the coast-line and the development of the continent? Explain.
INFLUENCE OF TOPOGRAPHY UPON CIVILIZATION
What effect has the structure of a country upon its civilization? A people can never become civilized unless they have homes. In ancient times permanent homes were possible only where fertile areas of the earth were walled in by natural barriers, such as mountains, deserts, etc.
In Palestine, for example, the land was fertile—a " land flowing with milk and honey ". It was a country with many natural defences—bounded on the west by an almost inaccessible sea-coast; on the south by a great desert through which the wandering Israelites had passed: on the east by the Sea of Galilee, the deep valley of the River Jordan, and the Dead Sea. In the north was a plain, the one weak spot in this great natural fortress.
The Israelites had many enemies in the surrounding countries, many of them being wandering nomads whose trade was war. They were able to defend themselves successfully against these enemies for centuries and thus became the founders of the highest civilization of their time.
Other races in other regions had similar opportunities to develop a distinctive civilization. What natural conditions made possible the civilization of India, Japan, Egypt, Greece, Rome, respectively?
What modern forces and tendencies have made impossible the conditions upon which ancient civilizations were based? For some of the factors in the development of the British type of civilization see " The Evolution of the British Empire " (Chap. XV) .
For what purpose are jails, or prisons, used? Of what use are the barred doors and windows? The bars or "barriers" prevent prisoners getting outside or beyond them. Is the high jail wall a barrier too? Why?
How are lots, farms, etc., separated from one another? Are these "line" fences barriers? What purpose do they serve?
Are swamps, muskegs, rivers, lakes, etc., barriers? Why? Do animals, such as the horse, fox, dog, etc., find them barriers? Why? Do birds find them barriers? Why not? Does man? Why not? Are they barriers to the spread of trees, weeds, ay.? Explain. What name do we give to barriers found in nature, that is, not made by man? Name other "natural" barriers. Which of these may be called "world" barriers? Why?
Name the greatest mountain ranges of the Old World. Which of these forms the greatest bar or barrier to travel? The Himalayas. Why?
Is man able to cross them? Are animals? Are birds? Are plants? Which of these would find the least difficulty in crossing the Himalayas? Why? What races of people are separated by the Himalayas? What general influence has this range of mountains had upon the development of the people of China and India? Why? What are some of the characteristic animals of India? Why are these animals not found to any great extent north of the Himalayas?
How are plants able to cross mountain ranges? What special difficulties do they meet with in crossing? Show that. these difficulties are not met with in spreading over a level country. Europe is a comparatively small continent. How would you account for its having so many races of people and languages? Name other mountain barriers and explain how man overcomes them.
Name the oceans. Are they barriers? Why? Why may we call them world barriers? Does, man find the oceans as great barriers as formerly? Why not? What living things besides man, have found the oceans to be great barriers? What kind of oceans form the greatest barriers? (Wide oceans and the frozen oceans) Name the widest ocean. What continents are separated by it? What continents are separated by the frozen Arctic Ocean? Why is the Arctic Ocean so impassable a barrier? What ocean barriers separate America from the Old World?
What race of people lived in America at the time of its discovery by Columbus? Why were no white people found in America at that time? Were there any Indians living in Europe before Columbus discovered America? Why not ?
What general effect did the ocean barriers of America have upon the development of its people during the long centuries before the white man came? In what respects are the Indians physically unlike the whites? (See Text-book.) After its discovery many white people settled in America. A large number of the descendants of the former are still to be found in various parts of the continent.
Did the early explorers of America find types of animals different from those found in the Old World? Name some of them. Why were these not found in the Old World? Name some important animals of Europe not found in the New World. Why were they not found there?
Name some native American birds. Name a European bird that has become so common in America as to be a nuisance. Do birds find the ocean as great a barrier as the other lower animals? Why not? Did birds cross from Europe to America, and vice versa, before the latter was discovered? Name a few.
Do plants travel from one part of the earth to other parts? What proof have we of this? How do plants travel? Give an example. What effect has the ocean upon the dispersal of seeds? Why? Name plants found only in America previous to its discovery. Name plants, useful and injurious, which have since found their way to America.
NOTE. The ocean barriers in relation to the other continents may be treated in a similar manner.
Name the greatest desert in the world. What great race of people live south of the Sahara? North of the Sahara? What conditions for the independent development of these races were made possible by the Sahara desert?
Name typical wild animals found south of the Sahara. Why are these not found to any great extent north of the Sahara? Is the Sahara a total hindrance to the migration of birds? Why not?
Does it hinder the dispersal of seeds? Explain. How does man cross the Sahara? Name other desert barriers.