Book V -- Physiography

The Science of the Land and of the Sea

Contents

The Oceans . . . . . . . . . . . . . . .185
Depth of the Sea . . . . . . . . . . .186
Soundings . . . . . . . . . . . . . . . .186
The Sea Bottom . . . . . . . . . . .187
Dredging . . . . . . . . . . . . . . . . .187
Ooze . . . . . . . . . . . . . . . . . . . . 187
Fish . . . . . . . . . . . . . . . . . . .  . 188
Phosphorescent Fish . . . . . . . .188
Deep-Sea Fish . . . . . . . . . . . . .189
Icebergs . . . . . . . . . . . . . .. . . .189
Glaciers . . . . . . . . . . . . . . . . . 191
Bowlders . . . . . . . . . . . . . . . . . 191
Pack-Ice . . . . . . . . . . . . . . .. . 191
Ice-Worn Rocks . . . . . . . . . . .192
Rivers and Streams . . . . . . . . . 193
Underground Water . . . . . . . .193
Meandering Streams . . . . . . . 194
Habits of Rivers . . . . . . . . . . . 195
Canyons . . . . . . . . . . . . . . . . . 196
Flood Plains . . . . . . . . . . . . . . 197
Waterfalls . . . . . . . . . . . . . . . .198
The Land . . . . . . . . . . . . . . . . 199
Changes in the Land . . . . . . . .199
Mountains sculptured by Rains .  . 200
Sand Dunes . . . . . . . . . . . . . . .200
Waste of the Land . . . . . . . . . 201
Slow Motions of the Con-
tinents . . . . . . . . . . . . . . . . 202
Fossils . . . . . . . . . . . . . . . . . . 203
Sandstones . . . . . . . . . . . . . . .204
The Interior of the Earth . . . . 205
Stratified Rocks . . . . . . . . . . 205
Formation of Mountain Ranges .. . . . .205
The Oldest Mountains in America . . . .208
The Age of the Earth . . . . . . . . . . . . .209
Age of Different Parts of America . .. 209
Age of Man on the Earth . . . . 211
Flint Weapons . . . . . . . . . . . . 211
The Earliest Drawing . . . . . . . 211
The First Plaything . . . . . . . . .212
A Geyser . . . . . . . . . . . . . . . . .213
The Internal Heat of the Earth 214
Volcanoes . . . . . . . . . . . . . . .  . 214
Teneriffe . . . . . . . . . . . . . . . . . 214
Kilauea . . . . . . . . . . . . . . . . . . 215
Vesuvius . . . . . . . . . . . . . . . . . 215
Herculaneum and Pompeii . . . 215
Volcanoes in the United States 218
Old Lava Fields in Idaho, Oregon, and Washington . . .218
Earthquakes . . . . . . . . . . . . . . . . . . . . 218
Cause of Earthquakes . . . . . . . 219
The Charleston Earthquake (1886). . . . . . . .  . . 219
The Mississippi Valley Earthquake (1811). . . . . 222
What to do during an Earthquake . . . . . . . . . . 222
Earthquake Detectors--how to make them . .  . . 222
The Lisbon Earthquake (1755)  . . . . . . . 223
Sea Waves . . . . . . . . . . . . . . . . . . . . . . 224
The United States Ship Wateree At Iquique (1868) . . . .224


Fig 162 The Grand Canyon of the Colorado River

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The Oceans.--The children were looking at a large globe and talking about it. First they turned it so as to show the water hemisphere, then so as to show the land hemisphere, and then so as to show the two poles--arctic and Antarctic. (See the pictures, Figs. 6 and 7.)

Mary. I never quite understood before how much sea there was and how very little land.

Tom. The books say that three quarters of the surface of the earth are water, and this globe makes you believe it.

"You'd believe it, if you ever made a long voyage by sea," said Tom's father. "Once I sailed straight west for a whole month in the Pacific, from Peru to Tahiti, and at the end of the month I was only halfway across to Australia. I knew all about maps and globes, but I never realized how large the Pacific was until that time. I've had a respect for the mere size of it ever since."

Tom. The Atlantic is large, too, but we don't think of it as so very large because the streamers to England are so very swift. They cross from New York to Liverpool in six days.

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Jack. There's another thing. The Atlantic has cables across it in many places and we read the telegrams from Europe in the newspapers every day. That makes England seem near.

Mary. How deep is the sea, Jack?

Jack. Oh, it is of very different depths in different places. The Atlantic Ocean, on the average, is a little over two miles, and the Pacific is deeper--about three miles. But you know there are places where the sea is much deeper--nearly six miles. Near our new island of Guam in the Pacific there is a spot 31,600 feet deep.


Fig 163 A Deep-Sea Dredge--It is a large bag or scoop bringing up parts of the ocean floor. Little shells and so forth are caught by the tassels.

Fred. The highest mountains are about five miles; the sea is as deep as the mountains are high. That is a way to remember.

Jack. Yes; but you must remember too, that there is very much more area of deep sea than of mountain regions, so you could not fill up the sea by putting the mountains in it. You would have to borrow some land from another planet to fill it up.

Depth of the Sea.--"I suppose they find the depth of the sea by sounding with a weight on the end of a rope, don't they?--just as we do in a pond," said Fred.

Tom. They do not use rope; they use piano wire; the rope would float--or at least it would not sink as quickly as wire does.

Jack. Yes, they use miles of fine piano wire and a heavy weight that drops off when it strikes the bottom. That makes it easy to reel the wire in again.

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Agnes. What is at the bottom of the sea, Jack?

Jack. Anywhere near the land the sea bottom is covered with mud. The rivers and the rains carry the soil of the land far out to sea and the ocean floor is covered with it.

Little pieces of the rocks of the land are carried out to sea, and you find the same rocks in this mud that we have on the land. The Mississippi or the Amazon river carries its mud out to sea for hundreds of miles. When you get very far from land the dredge brings up a different kind of rock. The little pieces of rock in the sea bottom very far from land have sharp angles. They have not been rolled about by surf and their corners are sharp like crystals.

Besides these rocks the dredge brings up the shells of little creatures that live near the surface of the sea. When they die their shells sink to the bottom, and there are millions and millions of them, so that a good part of the ocean floor is covered with a kind of ooze--they call it--mostly made of these shells. Then we find the bones of fishes, the teeth


Fig 164 A bit of ocean floor from a region
within a few hundred miles of the land.
Notice that the fragments of rock are rounded,
which shows that they have been washed by waves.




Fig 165 A bit of the red clay of the floor of the deep ocean far from shore.
Notice that the fragments of the rock have sharp angles,
which proves that they have not been rolled about by surf
and do not come from the washings of the continents.


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of sharks, and things of that kind imbedded in the clay; and small pieces of ivory, too, with pieces of meteors which have fallen into the sea. You see the ocean floor is made up of at least three different things--the washings of the continents, the red clay, and the ooze of shells and the like.

Tom. Then, of course, the ocean is full of fish.

Jack. There are plenty of fish near the surface. They live where their food is, and most of it is near the surface. There are some fish in the greatest depths, too, but the living things there are mostly crabs, starfish, shellfish, and so forth. You know the surface of the water is crowded with jellyfish of all kinds.

The jellyfish are phosphorescent. They glow when they are disturbed just as a sulphur match glows when you rub it with your fingers in the dark. All the light at the bottom of the sea comes from jellyfish. The sunlight does not go very deep down.

Tom. How do you know there is any light at the bottom of the sea, then?

Jack. Because the deep-sea fish have eyes. If there were no light whatever, all the fish would, in time, lose their eyes, just as the fish in the Mammoth Cave have; but many of the deep-sea fish have eyes.


Fig 166 A floating jellyfish


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Fred. There are fish--whales and so forth--near the surface of the sea; and there are starfish and crabs and shellfish at the bottom. What is in between?


Fig 167 A deep-sea fish with eyes


Fig 168 A deep-sea spirula, a king of cuttlefish.
The real fish is just twice the size of the picture.


Jack. Almost nothing, Fred; just dark, quiet, cold water, with no seaweed, no plants, no animals, and no fish. There is no life there to speak of; no light and no motion, for the waves that we see on the surface do not go down very deep either. The middle depths of the ocean are the most dreary and the most monotonous places you can conceive of. The arctic regions are gay compared to them!

Icebergs.--"How do you children suppose an iceberg is formed?" said Jack.

Mary. I suppose the sea water freezes and makes it.

Fred. That will not do, Mary. Don't you see that water could not freeze high up in the air like that?

Jack. Do any of you know?

Tom. Icebergs break off from the ends of glaciers, they say.

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Fig 169 A floating iceberg--Ice is a little lighter than water, and it floats therefore.
About one-seventh of an iceberg shows above the surface; six sevenths are below.



Fig 170 Icebergs breaking off from the end of Muir Glacier in Alaska

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Glaciers.--"And glaciers are rivers of ice flowing slowly down from the mountains," said Jack.

Agnes. Do they flow like rivers?

Jack. They flow somewhat as rivers do; yes, only very much slower--a few hundred feet a year, for instance; but they often keep on till they reach the sea (see Fig. 170), and there huge pieces break off and form bergs.


Fig 171 A bowlder of rock that was once on the top of a glacier--The glacier brought it from far away, and the rock was left here when the glacier melted.

Tom. Then the water of icebergs is not salt; it is fresh.

Jack. Yes, it is rain water that has fallen as snow, you see.

Mary. But the sea water does freeze, Jack, doesn't it?

Jack. Certainly; and makes the great ice fields that you have read about.

Some of these fields are very thick, especially when they have been packed together by tides and currents. When the ice first freezes it is smooth, of course, but after it has been packed it is horribly rough. It is often entirely too rough to travel over, and that is the reason why it is so hard to get to the north pole.

Tom. You go as far as you can in your ship, and then you take dog sledges, and finally you come to ice too rough to travel over. Is that it?

Jack. Yes; the ice blocks are as big as houses and are all piled together every which way, and a day's journey is often only three or four miles.

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Fig 172 A rock on the coast of Maine that was once under a glacier and has been worn smooth by the ice.



Fig 173 The beginning of a glacier high up in the mountains. 
The snow of the peaks slides into and down the valleys and
becomes ice by the pressure of the tightly packed mass.
If you pack a snowball very tight, it becomes nearly pure ice.

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Rivers and Streams.--"Did you children ever think of how a drop of rain water gets from the mountains into the sea?" said Jack. "It is worth while. Suppose you begin by thinking of what happens when the rain falls on a plowed field. The next time there is a rain you must look carefully and see exactly what takes place."


Fig 174 A ship frozen in an ice field

Underground Water.--"Part of the water soaks into the ground, but most of it urns off in little streams," said Tom.

Jack. What becomes of the water that soaks into the ground, Agnes?

Agnes. Why, a good deal of it stays there. If you dig down, the ground is always moist.

Jack. And when corn is planted in the field it gets a good part of its water from the earth. You know there is a great deal of water in Indian corn--in the ears and in the stalks; so some of last month's rain will be in the sweet corn you will eat

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next August. Now, what becomes of the water that does not get into the ground but runs off?

Fred. Some of it gets into the air as moisture and makes fog and clouds.

Agnes. Yes, and those clouds may bring rain again.

Mary. But not on our field; they will be far away the next time it rains.

Fred. And most of the water runs off in little streams and by and by gets into the brook.

Mary. And the brook carries it off to the river, and the river to another river, and so on, till it gets to the sea.


Fig 175 Little streamlets of rain water running off plowed ground.

Jack. Does the water ever flow uphill?

Agnes. No, of course not.

Jack. Then it is downhill all the way from our field to the sea. If you followed a drop of water in the brook, it would always be traveling downhill, but it would not go straight.

Fred. I should think not! No rivers are straight.

Jack. A river in Asia Minor, called the Maeander, was so full of bends that it gave a name to that habit of rivers; we call them meandering rivers, and the bends meanders.

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Agnes. Can you say that rivers have habits, Jack?

Jack. Why certainly, Agnes; a habit is a custom, that is all.

It is a habit of rivers to flow downhill, to be crooked, to carry little particles of sand and soil in their streams, to roll pebbles and stones along their beds, and so on; it is a habit of rivers to work--they are industrious.


Fig 176 A meandering brook

Agnes. Oh, Jack--industrious!

Tom. Well, they are. They carry no end of soil and rocks along in their course, and they work day and night, too.

Jack. You might almost think a river was alive if you counted up all the different things it did, and you might almost say a river had a purpose in life, just as a man has.

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Take the Colorado River, for instance; its purpose is to get to the sea in the best way possible, and it has industriously cut a way through rocks till its canyon is nearly a mile deep. (See the picture on page 184.) Some rivers actually steal.

Agnes. Oh, Jack! What do they steal?

Jack. Well, for one thing, they steal water from other rivers and carry it away themselves. For instance, the Savannah River has stolen a lot of branches from the Chattahoochee. (See Fig. 177.) Then rivers are young and middle aged and old, too; torrents first, and then steady-going, and by and by very mild and gentle; and you might say they are angry when they are in flood. The Yellow River in China has drowned a million persons in a year (1887); the Ganges is nearly as bad; and our own Mississippi has terrible floods.


Fig 177 The Chattahoochee River Formerly owned the waters quite up to the border of North Carolina that now flow in the Chateuga and Tugaloo basins into the Savannah River and so to the sea. It is quite likely that the Oconee River will capture more of the Chatahoochee waters in times to come.

Fred. Anyhow they don't mean any harm, and they are industrious; they do the best they know how.

Jack. Industrious they certainly are. In the first place, the water dissolves a great deal of rocky soil (just as water dissolves sugar) and carries it along to a new place. Then a river carries a great deal of sand and mud in its stream and drops that, too, when it can carry it no longer.

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Agnes. When does it drop the mud, Jack; when it gets tired?

Jack. You might say so. While the river is flowing fast it can carry a great deal of mud and sand; as soon as it begins to move slower some of this mud falls to the bottom.

Tom. If you want to get dirt out of a wash basin, you have to make the water move quickly. If it moves slowly, the dirt begins to settle.


Fig 178 The town of Ems (Prussia) built on the narrow flood plain of the Lahn River

Jack. They say that the Mississippi carries mud enough every year to make a range of hills a mile long, half a mile wide at the bottom, and five hundred feet high; and the Nile brings huge quantities of soil into lower Egypt. The flood plains of such rivers are the most fertile parts of the world.

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Fig 179 Niagara Falls--The falls are 165 feet high, and the river is nearly a mile wide just above the falls.

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The Land.--"When people talk about the sea," said Jack, "they speak about it as if it were always changing--they call it 'the restless sea'; and when they talk about the land they speak as if the land never changed at all--'the everlasting hills,' they say. Of course it is true that the hills and mountains do not change much in your lifetime or in mine, and of course it's true that if you are at the seashore the waves are never still for a moment; but really and truly the land changes more than the sea does, if you take the whole history of it. The surface of the land is changing all the time."


Fig 180 A mountain range in California--The summits are covered with snow which, melting, forms the brooks and rivers; rains model the ravines. Every feature of this landscape has been formed by running water.

Mary. I don't quite see how, Jack. I have been here all summer. What changes have there been?

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Jack. You have seen the brook to-day. What color was the water, Mary?

Mary. Why, it was clear.

Jack. And yesterday, when it was raining so hard, what color was it?

Mary. It was muddy. Yes, I see; the rain from the ground carried off some of the soil to the brook. It was not much, though.

Jack. No, not much. But suppose you have a hundred showers every year; in a hundred years there will be ten thousand showers, and every shower will do some work and will carry away some soil. In a hundred centuries there will be a million showers; every one of them will do some work, and all of them together will do a great deal. They will sculpture mountains and level continents.


Fig 181 Sand mountains (dunes) in the rainless desert of the Sahara.--They are modeled by the wind. Along many seacoasts such dunes are to be found.

Mountains.--"Nearly all the mountains of the globe are modeled by water. Wherever there is frost, too, great pieces of rock break off and fall. The shapes of mountains in arid countries like Arizona are modeled by the winds; and then,

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you know, there are volcanoes, and they change their shape, too. Everywhere the form of the land is changing."

Tom. If all this went on long enough, the earth would be flat.

Agnes. You might say more than that, Tom. You might say that the rains would make all the mountains flat, and that the rivers would carry everything to the sea. Why doesn't that happen, Jack? Why isn't all the land carried into the ocean? Why isn't the whole world flat?


Fig 182 A cliff of hard rock--The sloping bank at its foot is made up of rock that has fallen from the cliff.

Jack. If you gave it time enough, it would be, Agnes; but it would take a great deal of time! The books say that the surface of a whole continent might be lowered an inch or so in a century. North America is, on the average, about 2000 feet (that is 24,000 inches) above the ocean, so you see that it would take at least 24,000 centuries to level it--at least 2,400,000 years. But long before that time other things would happen to prevent. Some of the continents are slowly rising out of the sea all the time, and it is the elevation of whole countries that makes up for the washing away of the land.

Tom. I never heard of that before, and I don't understand it. What countries are rising now, for instance?

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Jack. Well--Sweden is rising, slowly rising, two or three feet in a century. And the northern coast of California is rising, and many other coasts and regions, too. They say the coasts of Alaska and of Peru have been raised more than thousand feet.

Agnes. Aren't some regions sinking?

Jack. Yes, of course. If one region rises, others will sink. They say the coasts of Massachusetts and of New Jersey are now sinking about two feet in a hundred years; and there are plenty of other places, too, but I don't remember them now.

Agnes. But, Jack, how can people possibly know that a country is sinking, if it move as slowly as that? Two feet in a hundred years--why, how can they tell?


Fig 183 Fossil shells inbedded in limestone

Jack. Well, it is not easy, but there are ways to do it. If the sinking keeps on long enough, it is not hard to observe it. For instance, there is a part of the German Ocean not far from the mouth of the Thames where the whole coast has sunk. They say you can even see the remains of buildings at the bottom f the sea when the water is clear. Those were English cities, and the land has sunk within a few hundred years. We know the history of it, I believe. There is a very good way to tell, though, what land has risen out of the ocean.

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Tom. What way, Jack?

Jack. By seashells--fossil seashells--found on land, even on mountain tops. Suppose you should find, not one, but thousands and thousands of seashells on the very top of a hill; suppose that the whole rock should be made of them. Well, wouldn't that prove that that particular hill had once been under the sea?

Tom. Yes, you could prove it that way.

Jack. Now suppose that all the hills for hundreds of miles around were made of shells--of shells of animals that we know cannot live on land, but absolutely must live in salt water--would not that prove that the region had been under salt water long ago?


Fig 184 The upland of New England with Mount Monadnock in the distance

Tom. Yes, of course. Are there many regions like that?

Jack. Hundreds of them. And in some of them every bit of the rock is filled with seashells. You know what sandstone is, of course?

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Tom. Yes, there is a lot of its here. Some of our hills are all sandstone.


Fig 185 A mountain in Utah filled with ravines, every one of which has been modeled by running water.

Jack. Well, sandstone is nothing but little grains of sand cemented together to make rock; and many sandstones have been formed under water--under salt water. A large river, let us say, brings sand from the shore, and drops the sand grains on the sea bottom. In time the grains are cemented together, and then you have layers of sandstone. By and by something like a great slow earthquake happens, and the sandstone is lifted above the sea. It may be lifted, in time, very high. Then you have layers of sandstone on land. The rains come and wear it into ravines, and parts of it crack and fall, and some of it is covered with soil by the washings of other rivers.

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and by and by trees and grass grow there, and you have a country like the one we live in.

The earth is not solid down to its center, you know. We live on the outside crust of it. That is solid, of course, and it is about a hundred miles thick. Inside of the crust great parts of the globe are red-hot rocks, like melted lava. It is as if the continents and the oceans were resting on an inside globe of melted rock. The heaviest parts are always pressing down, and the crust is always being strained and bent and cracked. Some parts of the earth are sinking very slowly, and other parts are slowly rising. Wherever the crust moves you have cracks and when the cracks are large you have long valleys and mountain ridges. (See the picture, Fig. 188.)


Fig 186 The earth's solid crust is about 100 miles thick; the narrow line in the picture would be more than 100 miles thick if the diameter of the circle were 8000 miles. Within the crust the rocks are very hot--melted. The pressures in the interior are so great that the rocks, though melted, do not flow like a liquid, but are almost rigid, like a solid.

Stratified Rocks.--"Are all mountains made in that way, Jack?" said Tom.

Jack. Not exactly in that way, Tom. You see it is like this: The crust of the earth sometimes breaks one way, and you have mountains like those in the picture (Fig. 188); and sometimes it does not break at all, but bends; it may be pressed or crumpled so slowly that it can yield without much breaking. There is a way to prove this. Do you know what stratified rock is?

Tom. It is rock layers--in strata.

Jack. Yes. Now we know that those layers were, in the first place, horizontal. They were layers of sand on the bottom of the

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Fig 187 Model to show how mountains are made by the cracking of the earth's crust


Fig 188 View of the mountains formed by the cracking of the earth's crust. (see Fig 187.)--They are in southern Oregon and northern Nevada and California. The long lakes and the streams lie in the direction of the cracks.


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sea, or perhaps they were layers of limestone with fossil shells scattered through them. In the pictures (Figs. 182 and 189) they have been lifted up so as to keep the layers level; but there are places, many places, where the layers have been crumpled like this:
(See also Fig. 190.)



Fig 189 A column of stratified rock--The rock is made up of nearly horizontal layers. The softer rock between the column and the cliff has been worn away by the waves in the course of thousands of years. Fig 182, preceding, shows a cliff of stratified rock--of rock arranged in layers.

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The crumpling makes the crust into mountains and valleys, and you must always remember that just as soon as a mountain is lifted up, it begins to be torn down again by the frosts, the rains, the earthquakes. The older the mountain is, the more its first shape has been altered, and you can tell its age in that way. (See Fig. 180 and 185.)


Fig 190 Strata once horizontal are sometimes elevated and folded so as to make mountain ranges, as in the picture, which shows such a case in Maryland. The Appalachian ridges in Pennsylvania (and the Jura Mountains in Switzerland) were made in this way.

The oldest mountains in America are the Laurentian Hills, near the St. Lawrence River, and the Green and Adirondack mountains. The Green Mountains are about forty or fifty million years old, the geologists say.

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Fred. What are the youngest mountains, Jack?

Jack. The youngest in America are the Coast Ranges of the Pacific slope. The books say they are about two or three millions years old. Two million years is young for a mountain. The Wasatch Mountains in Utah are middle aged.

The Age of the Earth.--"Do they know how old the earth is?" said Tom.

Jack. It is not known in the way you can say you know how old a tree is after you have counted the number of rings in its sawed-off stump; but it is known in a way. Take these very stratified rocks, for instance. They were formed under water by sand which settled down on the ocean floor and slowly cemented into rock. A layer a foot thick will be formed in about 10,000 years, the geologists say. Then a layer 100 feet thick might be formed in about a million years, and a layer ten miles thick in about 500,000,000 years. There is good reason to believe that the earth is at least as old as that, and maybe older. (1)

Agnes. Five hundred million years! I shall never be able to realize that! Why, I can't even understand what a million years is.

Jack. You remember how you children made a model of the solar system? (2) It helped you to understand large numbers, didn't it? Well, you can do something of the same sort here. Suppose that the next time you walk to the village you play that every one of your steps counts for a year. When you

(1) There is no part of the earth where we can see horizontal layers, one upon another, ten miles thick; but there are places where the layers, once horizontal (---), have been tilted up (////), so that we can now see their ends and be sure that the original layers were at least ten miles in thickness.
(2) See Book I (Astronomy), page 20.

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have taken 125 steps you have gone back 125 years, and that will take you back to the time of the Revolutionary War (1901 – 1776 = 125); and when you have taken 1900 steps you have gone back to the time of Christ. When you have walked three miles you have gone back to the time when the first pyramids were built. You would have to walk about twenty miles, each step counting for a year, before you got back to the time when human beings first came on the earth; and you would have to walk two or three times round the earth before you got back to the time when the first life appeared on the earth, and much farther yet to get to the time when the earth was first formed.

Mary. It is puzzling, but I think I understand it a little better than I did before.

Jack. Well, my dear, suppose you remember what we have said and think about it by and by. Recollect--a step stands for a year; you were born twelve years ago--twelve steps just takes you out of to the lawn. The Pilgrims landed 281 years ago--281 steps down the road. You can put a peg here to stand for the coming of the Pilgrims. Eight hundred and thirty-five steps will take you to the landing of William the Conqueror in England; put in a peg for him. A mile will take you back to 600 years before Christ; the city of Rome was founded about that time. Two miles farther will represent the time when the pyramids were built in Egypt; and when you have gone about twenty miles--a year to each step--you will be get back to the time that men first appeared on the earth. That is far enough for now. The world was a very old world when Man appeared on it; it had a long history before he came. There had been life long before his time, as we know by the fossils,--shells, fishes, and animals; and there was a long time,

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nobody knows how long, before that when the earth had no life on it at all--no men, no animals, not even a plant.

Age of Different Parts of the Earth.--"I understand how you can tell when the oldest seashells came," said Tom, "because you would find their fossils in the oldest rocks--in the rocks lowest down; and if you find a fossil rhinoceros higher up in the rocks than a fossil whale, you would say the whale came first. But how about men? Do they find fossil skeletons of men?"

Jack. Sometimes; but more often they find arrowheads that men have chipped out of flint, along with the fossils of animals. For instance, there are caves where arrowheads and lanceheads have been found along with remains of animals, and where it is plain that the caves were filled up by some accident soon after the men had died; those men and those animals lived at the same time. Sometimes they find the bones of the animals split open, so as to get the marrow out, and blackened with fire.

Age of Man on the Earth.--"Well, that would prove that the men used those very animals for food, wouldn't it?" said Fred.

Jack. Yes, and there is a more wonderful thing still. In one of the very old caves they found bones carved with pictures of reindeer. The man first killed the reindeer with his arrows, and dragged him to his cave and cooked him with fire. Then there was plenty of food in the house. The man felt secure and happy; he had leisure to think and to enjoy himself. And this drawing of a reindeer on a bone made by a half-naked savage is the beginning of all the beautiful pictures in the world. The man was, you may say, our ancestor; and the drawing is the ancestor of all the paintings of modern times.

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Tom. Some one ought to put up a monument to that man! He was the first artist--long before Pheidias and the Greeks.

Agnes. How long before, Jack?

Jack. I knew you were going to ask me that, Agnes. I was sure of it! Well, at a guess, 10,000 years or, it may be, 15,000. It is not certain, like the date of the last eclipse, or the time when Rome was founded. It is twenty miles, Agnes--a year to a step--don't you remember?

Agnes. Yes, I remember; but I don't see how you can tell, though.

Tom. Why, Agnes, if a man eats reindeer in order to live, he must be at least as old as the reindeer, mustn't he?

Agnes. Of course.

Tom. And if the fossil reindeer are found in rocks that it took 5000 years at least to make, then the man must have lived at least 5000 years ago. That is the way they find out.


Fig 191

Jack. That is the way they find out,--yes, Tom; but you must remember that just about 5000 years ago, in Egypt, men were building palaces and temples and pyramids, writing letters to each other, keeping accounts, spinning and weaving, painting and making statues. You have to go back at least 100,000 years to find the earliest men. Agnes, there is a place in the West--Idaho or California, I forget which--where they lately found something very like a doll; it might have been

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an idol, but it looked like a doll. Now this doll was buried in gravel that had been brought down by an old-time river. No one knows exactly how long it took for the river to bring down all the gravel that covered the place where the doll was dropped by the man who had it, but it must have taken thousands of years. Then, long afterwards, the volcanoes near by sent out rivers of lava, and thick sheets of the lava poured out and covered the old gravels and dried up the old river. No one knows exactly how many thousands of years it took for the many sheets of lava to form one above another; but they were more than half a mile thick--that we know. Then came a new river flowing across the lava, and it flowed for so many thousand years that it cut a deep groove for its bed in the hard lava. Scientific men can make a pretty good guess how long each of these different things took. Some men were sinking a deep well in the valley of the new river the other day, and in the well, deep down, they found the doll. You see that we can make a pretty good guess how long ago the doll was made by adding up all the years that were required to deposit the gravel, and to make the lava sheet, and for the river to cut its way in the lava.


Fig 192 A geyser spouting boiling water which comes from deep down in the earth

Agnes. Yes, I see. I suppose that is certainly the oldest doll in the whole world, though.

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The Internal Heat of the Earth.--"You were saying," said Tom, "that the interior of the earth is made of melted rock. I suppose you know that by the melted lava which comes from volcanoes. Lava is melted rock."

Jack. Yes, it is known in that way: volcanoes pour out melted rock. And then geysers send out hot water--boiling water sometimes; and in regions where there are no volcanoes we find that the deep wells always send out hot water--the deeper the well, the hotter the water.


Fig 193 The peak of the Teneriffe in the Canary Islands--The mountain is 12,000 feet high, and its beautiful form has been shaped by the lava streams flowing down from the crater. Notice that the rocks in the foreground form part of a very much larger crater that was active in ancient times and is now extinct.

Fred. How deep are the deepest wells, Jack?

Jack. There are some in Europe nearly a mile deep. They are not dug, you know, but are sunk by boring. There are deep wells in America, too; one in St. Louis is 3800 feet deep--more than two thirds of a mile. The water from it has a temperature of 105 degrees. Boiling water is 212 degrees, you know.

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Volcanoes.--"You know there are some splendid volcanoes in Hawaii," said Jack; "papa has seen them. One of them especially is easy to visit--Kilauea, (1) they call it. It is a great lake filled with red-hot boiling lava that comes up from some reservoir of lava deep in the ground. The lava is liquid rock. Usually it does not flow over the rim of the crater, but sometimes it overflows and sends great streams of red-hot lava all over the country round about and even as far as the sea--fifty miles off.

"Vesuvius, near Naples, is the most famous volcano. You know it buried two whole cities once--Herculaneum and Pompeii." (2)


Fig 194 A volcano is built up somewhat as in the picture. Underneath it are old rocks in layers. There is a reservior of lava somewhere underneath them, and a pipe filled with lava leading to the surface. (The lava is colored black in the picture.) When the lava overflows it moves down the side of the mountain like a great river and covers up everything that comes in its way. The upper end of the pipe is the vent, and the lake at the top is the crater. There is often more than one vent. (See the little black lines in the picture leading to different cones.)

Agnes. Tell us, Jack.

Jack. Pompeii was a kind of summer resort where the Romans used to go for pleasure. It was a pretty little town full of fine houses, temples, shops, and so forth, not far from

(1) Pronounced kee lah WAY ah
(2) Pronounced pom PAY yee.

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the volcano of Vesuvius. Seventy-nine years after Christ (A.D. 79) there was a great eruption, and the ashes began to fall on the city. At first the people were not very much frightened, but pretty soon things got worse and worse, and they began to gather up their movables and to leave the city. A great many of them got away, but hundreds and hundreds were buried in the ashes and died there. The ashes kept on falling for days, and the whole city was covered up. Almost the same thing happened in Martinique in May, 1902. Just imagine what might happen if there were a volcano near New York, and if the city were to be covered up with a thick layer of ashes and not even found again for more than a thousand years!

Agnes. Not found for a thousand years!

Jack. Well, Pompeii was buried in A.D. 79, and it was not until 1748 that people began to dig there and found the whole city complete, just as it had been left a good deal more than a thousand years before.

In a baker's shop, for instance, they found loaves of bread all shriveled up, and perfumes and oil and jewelry in other shops. The houses were filled with things that the people used every day; everything was just as before.

Agnes. But the people, Jack--were they found? Were their bodies found?

Jack. Their bodies had mostly wasted away, Agnes; they found their skeletons. One man had come back after his money, and other people after their jewels. The money and jewels were found, and the bones of the persons near them. In one place they found a picture of a watchdog with the sign, Cave canem; that means--what does it mean, Tom, in English?

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Tom. It means "Beware of the dog!"

Jack. Yes; as we should say "Look out for the dog!" A very great deal of what we know about ancient pictures and statues we learned from Pompeii.

Fred. If New York were buried and dug up a thousand years from now, the people of that time would know how we lived.


Fig 195 The picture shows the volcano of Vesuvius as it appears today, and in the foreground a part of the city of Herculaneum after the layer of lava has been taken off. Herculaneum was covered with thick ashy mud and even better preserved than Pompeii, which was buried in showers of ashes. Everything in it was found exactly as it was left--shops, houses, temples, jewelry, tools.

Tom. If you went into a house, you would know just what each room had been used for--the kitchen and the dining

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room and the bedrooms--and just what pictures we had liked and hung on our walls, and what books we read, and everything of that sort.

Mary. And they would know what games we played--tennis and golf; and they might find Agnes' dolls and mine.

Agnes. Just as we found the doll Jack told us about that was buried under the lava in California.

Fred. Are there any volcanoes in the United States?

Jack. There are plenty of mountains that are old worn-out volcanoes, and a few that are still active. Mount Shasta, for instance, in California, is an old volcano, and there are active volcanoes in Alaska, Hawaii, and the Philippines. You children ought to recollect, every time you look at a map, that a very large part of three great states--Washington, Oregon, and Idaho--is nothing but an old lava field. A good part of the lava is 3000, even 4000 feet thick, and it covers thousands and thousands of square miles. All that lava flowed from ancient volcanoes, though it did not flow all at one time; for they find the lava in layers with ashes and soil between, and in some of the soil they find petrified tree trunks.

Tom. That shows the trees had time to grow between one lava flow and the next one, doesn't it?

Jack. Yes, and it gives you an idea how long it took to deposit all that thickness of lava. The doll I told Agnes about was found in this very lava field.

Earthquakes.--"Do earthquakes come from volcanoes?" said Fred.

Jack. There are always earthquakes wherever there are active volcanoes, Fred. You can see that a volcano in eruption which has energy enough to throw huge stones thousands of feet into the air must shake all the ground near it by its

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explosions. All volcanoes make earthquakes, but very many earthquakes are not caused by volcanoes.

Mary. What does cause them then, Jack?

Jack. Suppose you lay a book flat on its side, Mary, and imagine that the book is part of a layer of rock that was once deposited at the bottom of the sea. Now take another book and lay it flat on the first one. That stands for a second layer of rock--perhaps a different kind of rock--lying over the first layer. Now you know the crust of the earth is moving slowly all the time, sometimes up, sometimes down. Suppose both those layers of rock were lifted so that one end of them was higher than the other. Tilt the books, Mary, and keep tilting them, and see what happens.

Mary. Why, one book slides off the other. (1)

Jack. That is exactly what sometimes happens to great beds of rock. They lie flat in the first place. Then they are slowly tilted, and by and by one of them slides a little--a very little--on the other. Ten million tons sliding only a little way--an inch perhaps--will make a terrible shock that can be felt for hundreds of miles around. The Charleston earthquake was caused in just that way.

The geologists say that the layers of rock underneath South Carolina lie one on another like the two books, and the earthquake was caused by the sliding of the layers. The rocks I am talking about were deep underground, you know. When they moved, the rest of the rocks moved, too, just as a pile of bricks will slide when you move some of the bottom ones; all of them moved. A good part of Charleston was wrecked, you know, and all the eastern part of the United States was shaken

(1) The simple experiment should be tried in the schoolroom, choosing two books with smooth covers.

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more or less. Why, they even felt the shock at Boston, at Toronto in Canada, at Chicago, at St. Louis, and at New Orleans. The shock was not severe there, but it was felt.


Fig 196 The church of Saint Augustine in Manila, Philippine Islands, after the earthquake of July, 1880.

Tom. Of course an earthquake is weaker and weaker the farther you go away from the center of it.

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Fig 197 View of part of Charleston, S.C., wrecked by the earthquake of August, 1886

Jack. Yes; like the little water waves in a pond when you throw in a stone. That is a "waterquake," you might say. You know the waves are larger and higher at the center, and become smaller as they move out. All of South Carolina was badly shaken, so that chimneys fell. The shocks were strong enough to frighten people in Georgia, in Ohio, and in

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Pennsylvania, and they were felt as far as the Mississippi River, and farther.

Mary. Were many people killed, Jack?

Jack. Only a few, Mary. They ran out of their houses, and lived in the parks for several days till the shocks were over.

Agnes. Oh, did the earthquake last for days?

Jack. There were shocks every now and then for several days, but only a few really severe ones. You see it took several days for all those rocks underground to settle down and be quiet. There was an earthquake in the Mississippi Valley once (1811) that lasted nearly a year. The people camped out of doors for months and months.

Agnes. Might we have an earthquake here, Jack?

Jack. Certainly, we might; no one can tell. There are not many earthquakes in the eastern part of the country, and those that we have are usually light; you need not be afraid of them. If an earthquake comes, go out of doors and keep away from houses--that is all. But there are earthquakes everywhere--light ones. You boys can prove it if you want to.

Fred. How can we prove it?

Jack. Get some pieces of nice wood--red cedar, for instance--and make two or three pyramids. (See Fig. 198.) Then cut off a little of the top of each one of them, and stand them upside down in a steady place--on the mantelpiece of a room that is not used much, for example. When a slight earthquake comes--one too slight for you to feel perhaps--the house will be shaken and the mantelpiece, too, and the pyramid will fall on one of its sides. Try it.

The boys did try it. They made half a dozen pyramids and cut off a little of the top of each one, and stood them about in different places in the house and in the barn. They

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often would find one of them fallen on its side, and they usually discovered that the housemaid, in dusting, had caused that particular earthquake. But every few months they found all the little pyramids thrown down, and most of them lying in one direction; and then they knew that there had been a light shock--too light for them to feel, but strong enough to overturn their "earthquake detectors," as they called them. The direction in which the detectors lay on their sides showed the direction in which the earthquake wave was moving--north and south, for instance.


Fig 198 Pyramid

The Lisbon Earthquake.--"They say the Lisbon earthquake was one of the very worst," said Tom; "do you know about that, Jack?"

Jack. It was one of the worst certainly because there was not only an earthquake, but a great sea wave too. The people ran out of their houses to take refuge in the churches, and then the churches fell and crushed them. Many went to the wharves

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so as to be away from falling walls, and a huge wave from the sea--eighty feet high, they say--rolled in and drowned thousands of people.

Fred. A wave eighty feet high! What made it, Jack? Was it a part of the earthquake?

Jack. No doubt the level of the sea bottom was changed somehow, and the water rolled in like a great wall. That often occurs in South American earthquakes. A strange thing happened to one of our war vessels once. It was the Wateree, and she was at anchor in the bay of Iquique (1) in Peru (1868). All of a sudden came a great wave from the sea and tossed the ships about like boats, and it carried the Wateree far inland and left her there high and dry. Think of it--one of our war ships with all her guns and men (no one was hurt) high and dry on land!

Fred. What did they do? Could they get her off?

Jack. No; and so the government took away all her cannon and everything that was valuable, and sold her to a Spanish gentleman for a summer house!

Agnes. I think that's funny. A man-of-war for a summer house!

Jack. That is not the funniest part of it, Agnes. A few years later there came another great sea wave, and it lifted up the Wateree and carried her a long way farther inland, and there she is now, a summer house for a different family.

(1) Pronounced ee--KEE--kay.



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