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EVERYDAY SCIENCE
BY
WILLIAM H. SNYDER, Sc.D.
PRINCIPAL OF THE HOLLYWOOD HIGH SCHOOL
LOS ANGELES
ALLYN AND BACON
BOSTON NEW YORK CHICAGO
ATLANTA SAN FRANCISCO
COPYRIGHT, 1919, BY
\ WILLIAM H. SNYDER
NortnootJ Jprrsa
J. S. Gushing Co. —Berwick & Smith Co.
Norwood, Mass., U.S.A.
PREFACE
EVERYDAY SCIENCE was written primarily for eighth and
ninth grade pupils who will never have any further training
in science. The book, therefore, covers a wide field, and
does not unduly emphasize any of the special sciences. The
subject matter is chosen not for the purpose of appealing
to any group of special science teachers, but rather with a
view to making pupils as intelligent and useful citizens as
possible.
The book is, first of all, both interesting and simple, and
aims not only to furnish a fund of valuable scientific infor-
mation, but also to arouse scientific curiosity and to en-
courage further study both in and out of school. It will
inculcate scientific habits of thought, and will substitute
the beginnings of knowledge and confidence for misappre-
hension and superstition.
The usefulness of science is brought out in innumerable
applications of its principles to the household, the yard and
garden, the farm, the city street, industries, and transpor-
tation. Good citizenship is fostered by the' interesting
treatment of such subjects as personal hygiene, community
health and sanitation, reclamation of lowlands, irrigation,
forestry, coastal navigation, canals, and inland waterways.
But the pupil's scientific studies are not hemmed in by
the four walls of the home, by the garden fence, or 'even by
the nation's boundaries. Breadth of vision, imagination,
and reverence are cultivated by a knowledge of the earth
as a planet, of the main outlines of its physical history, of
459964
IV PREFACE
its neighbors in limitless space, and of the changeless laws
that govern its relations with the heavenly bodies.
The pupil is never plunged into discussions that are beyond
his depth. Long, intimate experience with young students
has shown how futile it is to presume any background of
scientific information on the part of eighth and ninth grade
pupils. From the very beginning the book proceeds from
the known to the unknown, from the more simple to the less
simple. It may be taught in its entirety to immature
pupils.
To make the various subjects more vivid and more in-
teresting, practically every topic is illustrated either by a
photograph or by a drawing or by both. The many ex-
periments help to fix the principles and to inculcate scien-
tific habits of thought.
The present edition contains sixty simple projects which
will appeal to boys and girls, and which can easily be
worked out without the use of expensive material.
Thanks are due to the many teachers, especially in Los
Angeles, whose suggestions have helped to make the book
both teachable and learnable.
JULY 4, 1919. \y f J S.
CONTENTS
The two opening
chapters orient the
pupil in the universe.
Figuratively speaking,
the author takes him
up on a high mountain,
lets him survey the field,
and helps him get his
bearings in the world.
CHAPTER I. THE OPEN SKY
The Sun — Stars and Planets — Constellations
— Our Solar Family — The Moon — Eclipses
— Comets . . . . . . 1
Interesting facts about the heavens. The vast-
ness of solar distances.
CHAPTER II. OUR OWN WORLD
The Size and Shape of the Earth — Movements
of the Earth — Causes of Seasons — Standard
Time — International Date Line — Daylight
Saving — Terrestrial Magnetism . . 20
Peculiarities of the earth. Ancient and medieval
ideas.
Following the chap-
ters on the universe and
the world, this chapter
on the properties and
make-up of matter an-
swers the question,
" What is it all made
S/f"
CHAPTER III.
OF MATTER
PROPERTIES AND MAKE-UP
Forms of Matter — Properties of Matter : Ex-
tension, Inertia, Gravitation — Composition
of Matter — Physical and Chemical Changes —
Acids — Bases — Salts — Neutralization . 42
The composition of water. Iron rust. Uses of
familiar acids, bases, and salts in the household.
Manufacture of soap.
VI
CONTENTS
This chapter on the
sun's gift of heat an-
swers the question,
" What makes it go?"
and deals with the most
common form of en-
ergy, heat.
This chapter has to
do with air, the com-
monest thing in our
natural environment.
CHAPTER IV. THE SUN'S GIFT OF HEAT
Potential and Kinetic Energy — Forms of En-
ergy— "Loss of Energy" — Conservation of
Energy — Some Effects of Heat — Mass, Vol-
ume, Density, Weight — Nature of Heat —
Production of Heat — Combustion — Kindling
Temperature — Saving Fuel — Control of Fire
— Measurement of Temperature — Measure-
ment of Heat — Specific Heat — Latent Heat
— Transference of Heat : Conduction, Con-
vection, Radiation — Conserving Heat . 60
Expansion and contraction of bridge-spans, con-
crete sidewalks, table glassware, ice, water,
steam. Use of kindling. Tending a furnace fire.
Abating tbe smoke nuisance. Fire extinguishers.
Thermometers. Blankets and sheets as con-
ductors of heat. Heat insulation: revolving
doors, fireless cookers, thermos bottles, refriger-
ators, and snow.
CHAPTER V. THE ATMOSPHERE AND ITS
SERVICE TO MAN
Origin of the Atmosphere — Composition of
Air — Need of Air — Moisture in the Air —
Evaporation — Boiling — Effect of Heat on Air
— Humidity — Humidity and Comfort— Hu-
midity and Health — Weight of Air— Expan-
sion of Air — Ventilation — Atmospheric Pres-
sure— Measuring Atmospheric Pressure —
Air Pressure Machines — Air Pressure and
Heat — Ice Manufacture and Cold Storage —
The Barometer — Determination of Height by
Air Pressure ...... 96
Perspiration, fever, transpiration, humidity in
living-rooms and assemblies, humidifiers. Circu-
lation in a refrigerator, hot-air furnace. Use of
electric fan in summer and winter, home-made
ventilating devices. Lift-pumps. Vacuum clean-
ers, street-sweeping machines. Compressed air
to operate air-brakes, whistles, ventilating sys-
tems, force-pumps. Pressure cooker. Ice manu-
facture. Cold storage.
CONTENTS
Vll
As water is next to
air in importance in
our environment, its
treatment naturally fol-
lows the chapter on air.
The chapter on water
in general is followed
by a chapter on running
water, showing its geo-
graphic and economic
importance.
The study of the
chapters on the earth1 s
relation to the sun, and
on heat, air, and water,
has paved the way for
the introduction of this
chapter on weather and
climate.
CHAPTER VI. THE WATERS OF THE EARTH
Composition of Water — Effects of Varying
Temperatures on Water — Ability of Water to
Absorb Heat — Water as a Solvent — Freezing
Mixtures — Suspension and Solution — Emul-
sions— Pressure in Water — Buoyancy, of
Water — Water Reservoirs of the Earth —
Animal Life in Water — Waves — Currents —
Tides .135
Water, ice, and steam in everyday life. Hot-
water bags. Irrigation to prevent freezing. A
" sticky " salt cellar. Salt on ice in a freezer, or
on steps, sidewalks, or car track switches in
freezing weather. Settling basins, filtration.
Emulsifying action of soap. Pressure in water
mains and reservoirs, hydraulic press. Sub-
marines.
CHAPTER VII. THE WORK OF RUNNING
WATER
Power of Running Water — River Develop-
ment — Inland Waterways and History — Sup-
plying Water to Populous Communities —
Pure Water and Health . . . .170
Fertility of "bottom-lands." Natural and arti-
ficial levees. Harbors. Beginnings of great
cities. Canals, extension of inland navigation.
Ancient and modern city water supplies, reser-
voirs, pumping stations, water intakes. Water
purification, the St. Louis water system.
CHAPTER VIII. WEATHER AND CLIMATE
The Atmosphere as both Blanket and Sun-
Shield — Circulation of Air — Winds — Cy-
clones and Anti-cyclones — Storm-paths —
Sudden Weather Changes — Thunderstorms —
Tornadoes — Rainfall — Climate — Mountain,
Seaside, and Island Climates — Summer and
Winter Resorts . . . . .209
Cold-frame. Blizzards and "hot winds." Fore-
casting the weather. Absorption of heat. Fruit-
raising districts.
vm
CONTENTS
The study of heat,
air, oxygen, carbon di-
oxide, running water,
freezing water, solu-
tions, atmospheric mois-
ture, evaporation, and
condensation in previ-
ous chapters now en-
ables the pupil to un-
derstand how the earth
has been shaped and
how its rocky surface
was gradually pulver-
ized into soil.
The chapter on the
origin of soil is logi-
cally followed by a
study of man's use and
conservation of soils.
Since light is neces-
sary to life, this chapter
on light supplements
the preceding chapter,
and prepares for the
study of life in the next
chapter.
CHAPTER IX. THE EARTH'S CRUST
Changes in the Earth's Condition — Materials
Composing the Land — Upward and Down-
ward Movements of the Earth's Crust — Hills
— Mountains — Plateaus — Plains . . 247
Continental shelf. Newfoundland banks. Reefs
and dunes. Buttes and mesas. Erosion.
CHAPTER X. PREPARATION OF THE EARTH'S
SURFACE FOR PLANT LIFE
Natural Forces — Weathering — The Work of
Wind, Ice, and Snow — Glaciers and Icebergs
— The Glacial Period — Glacial Formations
and Lakes — Prairies of the United States —
Production of Soils . . . . .277
Soils produced by weathering. Ice as a soil-
builder. Parts of our country once covered by ice.
CHAFIER XI. MAN'S USE AND CONSERVA-
TION OF SOILS
Importance of the Soil — Composition of the
Soil — Water Film on Soil Particles — Fertile
Soil — Fertilizers — New Sources of Potash —
Fertilizing Agents : Gophers, Moles, Angle-
worms, Bacteria — Agricultural Soils — Soil
Water — Water-plants — Dry Farming — Irri-
gation—Alkali Soils — Value of Soils— Rec-
lamation Projects — Forestry . . . 307
Soil air. Humus. The work of moles, angle-
worms, and bacteria. Sand, silt, and clay.
Drainage and'seepage.
CHAPTER XII. THE SUN'S GIFT OF LIGHT
Light Necessary to Life — Direction, Intensity,
Reflection, and Speed of Light — Refraction
of Light : Telescope, Color — Light aiid Com-
fort . . . . • . . .347
.Lenses and cameras. Microscope, telescope, arid
spectroscope. Light and health. Natural and
artificial lighting.
CONTENTS
IX
Out of the soil with
the aid of light comes
plant life, on which
animal life is ultimately
dependent.
CHAPTER XIII. LIFE ON THE EARTH
Plants — Plant Roots — Cells — Stems — Graft-
ing and Budding — Leaves — Flowers — Seeds
and Germination — Dependent Plants , 366
Needs of plants. Functions of parts. Leaves as
factories. Peculiar plants. Pollen. Bacteria,
molds, and rusts.
Animals — Invertebrates: Protozoa, Worms,
Insects — Vertebrates : Man : Structure,
Breathing, Circulation, Senses, Sight, Sound,
and Hearing, Food and Digestion . .399
Health hints. Adenoids. Deep breathiug. Work
of white corpuscles.
The treatment of life
in the preceding chapter
leads to the study of
man's control of the
means of maintaining
We —food.
CHAPTER XIV. MAN'S EXISTENCE AS RE-
LATED TO PLANT AND ANIMAL LIFE
Fundamental Foods — Necessary Foods — Bev-
erages — Alcohol — Tobacco — Cooking of
Foods — Bacteria — Preservatives — Infectious
and Contagious Diseases — Antitoxins — How
to Disinfect — Dangers from Infected Food and
Water — Pasteurization — Sewage Disposal —
Cleanliness — Dangers from Mosquitoes, Rats,
Flies— Health Hints . . . .425
Carbohydrates, fats, proteins. Minerals, vita-
mins, relishes. Bacteria in bread, cheese, and
vinegar. Disinfection and sanitation.
This chapter concerns
itself with man's con-
trol of his physical en-
vironment by means of
machines.
CHAPTER XV. MAN'S INVENTIONS FOR
TRANSFERRING AND TRANSFORMING ENERGY
Primitive Tools — Friction — The Lever —
Wheel and Axle — The Pulley — The Inclined
Plane — The Wedge — The Screw — Man's
Most Important Energy Transformers — Con-
servation of Water-power . . . 459
Work, energy, and power. Water-power, tur-
bines. Steam and gas engines.
Through machines
man has developed elec-
tricity, thus furthering
his control of his en-
vironment.
CONTENTS
CHAPTER XVI. Two^ RELATED FORCES
THAT MAN HAS HARNESSED — MAGNETISAT AND
ELECTRICITY
Magnetism — Magnetic Field of Force — Mar-
iner's Compass — Theory of Magnetism —
Electricity by Friction — Current Electricity :
Electric Lighting, Electroplating — The Elec-
tromagnet : Electric Bell, Telegraph, Wireless
Telegraph, Telephone — The Dynamo — The
Electric Motor — Theory of Electricity . 475
Magnets. Dipping needle. Positive and negative
poles. Conductors and non-conductors. Cells.
Flatirons and toasters. Welding. Electrotyping.
Magnetic crane.
This chapter is de-
voted to the mysteries of
the sub-surface earth,
following naturally
after the treatment of
various aspects of sci-
ence on the earth.
This final chapter
contains a general dis-
cussion of .the relation
of life to physical en-
vironment.
The projects develop
practical knowledge by
personal investigation.
CHAPTER
CRUST
XVII. WITHIN THE EARTH'S
Volcanoes — Earthquakes — Geysers — Mining
— The Story of Coal and Oil . . .502
Craters. Lava and volcanic dust. Vesuvius and
Mt. Pelee. The Yellowstone. Mining districts of
the United States.
CHAPTER XVIII. LIFE
PHYSICAL CONDITIONS
AS RELATED TO
Ancient Life History — Distribution of Life —
Effect of Glacial Period on Plants and Animals
— Adaptability of Life — Plant and Animal
Life in the Sea — Life on the Land — Distri-
bution of Animals — Life on Islands — Man
Affected by Physical Features . . 522
Fossils. Petrified trees. Barriers to distribution.
Inland and seashore life. Strange plants and
animals. Effect of mountains on history. Ad-
vantages of harbors.
APPENDIX 555
PROJECTS 563
INDEX . 1
MAPS AND ILLUSTRATIONS
PAGE
The Climax of Scientific Achievement — Conquest of the Air Frontispiece
Mt Wilson Solar Observatory, the 150-foot Tower Telescope . . 1
Surface Explosions on the Sun . . 3
Sun Spots 4
Part of the Milky Way . . . . . . . . , . 5
A Star Cluster . .-._'"..„ ... 6
A Continuous Picture of the Northern Heavens . ... 7
Medieval Idea of the Universe 9
A Large Meteorite , , 12
Mars . . . . . , - 13
Three Views of Saturn 14
Surface of the Moon • . 14
Phases of the Moon . 15
Total Eclipse of the Sun ..16
Halley's Comet 17
The WTorld According to Hecataeus (500 B.C.) . . . . . 20
Partial Eclipse of the Moon 22
A Hut in the Tropics 30
A Laplander's Hut . . 31
Map showing Standard Time Belts 34
Map showing International Date Line 36
Region around the North Magnetic Pole 38
Airplanes . . .'.... !.'-,... v * . . . • 45
Three Forces in Play . >,. • . ,48
^Rusting of Iron ' . \ . . . . 54
Rock Salt . . . . ' . ,. . . i . . . 55
Kettle Used in Manufacture of Soap . . ..-.,. . . 56
A Pile Driver in Action . . . . * . . .61
Molten Steel Flowing from a Blast Furnace . ,_, . ... 69
Tinder Box and Flint and Steel v . . / .
Before Installing an Underfeed Furnace ....*. 76
After Installing an Underfeed Furnace . . . , . ..77
Fire out of Control . .: ... ,". »• -,.• ... 78
Revolving Doors . . .';... . . . • .91
xi
xii MAPS AND ILLUSTRATIONS
PAGE
Blue Hill Observatory, Milton, Massachusetts . . . .96
Strato-Cumulus Clouds 103
Fog 105
A Great Siphon in the Los Angeles Aqueduct . . . . . 119
A Modern Street Sweeper 121
Pressure Cooker 126
Mercurial Barometer 129
Aneroid Barometer 130
Barograph 130
Observation War Balloons 132
Bomb Burst by Freezing Water . 138
Montezuma's Well 140
Settling Basins of the St. Louis Water Plant 143
A Limestone Cave 144
An American Submarine 150
A Submarine Submerging 151
Corals . 152
" Airing " an Aquarium . . 153
Mount Everest 154
Crinoid . . . 155
Ocean Waves 158
Fingal's Cave • . . . . 159
A Lake Beach, Formed by a Stream and Wave Action . . . 160
A Sand Spit, Formed by Waves and Currents ..... 161
Ocean Currents of the World ' . . 163
High Tide in Nova Scotia ....'..... 164
Low Tide at the Same Place . . . . . . . 165
Mining Salt in the Dried up Salton Lake, California . . . 173
Lake Drummond 174
Gullies Being Cut by Running Water 175
Divides between Streams 176
Niagara Falls . .177
Stream Working Back into an Undissected Area .... 178
Yellowstone River 179'
Platte River 180
River Erosion 181
Bottom Lands 182
Stream Meandering on its Flood Plain 183
Oxbow Lakes .184
Levee along Lower Mississippi ........ 184
An Old River 185
River Terraces, Norway . . 187
Intrenched Meander 188
MAPS AND ILLUSTRATIONS xiii
PAGE
Intrenched Meanders, Map facing 188
Lake Brienz from above Interlaken, Switzerland . . .. 189
Old Fort Dearborn . . . . . . 191
Singel Canal, Amsterdam 193
Panama Canal . 194-195
Hot Springs in the Yellowstone National Park, U. S. A. . . . 197
Flowing Artesian Well . 198
Stretch of a Roman Aqueduct near Nimes, France .... 199
A Primitive Water Carrier in Mexico / . 200
A Standpipe ... 201
Fire-tug in Action . . 202
Wilson Avenue Water Tunnel, Chicago 203
One of the Chicago Intake Cribs 204
St. Louis Filter Plant . 205
Picture Taken at Midnight on North Cape 211
Winter Scene, in Venice . f* . 212
Winter Scene in Montreal 212
A Sailing Vessel ... 215
Hot Water Tank . •» . . . . . . < ... .217
Effect of Prevailing Wind on Growing Trees 218
Wind Map for January and February 222
Wind Map for July and August . 223
Cyclones and Anti-cyclones 225
Mean Storm Tracks and Average Daily Movements . . . 227
A Tornado . . . . ...... , . . — . . • .231
Effects of a Tornado . . . ••*.. •• ••:„• -.'. .,.; . . . .232
Waterspout Seen off the Coast of New England . 233
Magnified Snow Crystals .... . . . . . 234
Average Rainfall of the United States ...... 235
Salmon River Dam, Idaho . * . . ... . . . 236
Top of Pike's Peak in Summer . . . ,< v . > . . . . 239
Popocatepetl . . ... . - -., : « T- • • • • 240
Mid-ocean • . ,= . . - -241
Palm Trees on Tropical Island of Tahiti .... . .242
Spiral Nebula ... --. -, . • •*. , . -\ . •* - * . , . >- . . .247
Folded Strata . ...... .*,.«:•.. . . .249
Temple of Jupiter near Naples ,-jV ,. . ,. * / .... 250
Old Sea Beaches, San Pedro, California . ,<; . . . .250
Old Rock Beach, Imperial Valley, California .
Granite . . . .' . . .'-;,. ••' -. -:•,} '. . . .253
Fossil-bearing Limestone . . • 253
Conglomerate . . ...;.;• 254
Gneiss . . • • 255
xiv MAPS AND ILLUSTRATIONS
PAGE
Stratified Rock 256
Inland Sea Cave and Beach ; . . 258
Coast near Atlantic City 259
A Norway Fiord 261
A Submerged Coastal Plain . 262
A Norway Fiord ' \ 263
A Norway Village at the Head of a Fiord 264
Lofty Mountains . . . 265
The Matterhorn . 266
The Teton Range, Idaho, U. S. A 267
Colorado Plateau 269
The Enchanted Mesa, New Mexico ....... 270
A Butte ... 271
An Indian Hogan . . 272
Cliff Dwellings, Arizona 273
Indian Hieroglyphics Cut on the Steep Wall of a Mesa . « . . 274
A High, Dry Plain in Central Nevada 274
A Recently Cooled Lava Surface 277
Rock Split by Roots of Tree 278
Rocks Weathering and Forming Steep Slopes ..... 280
Cleopatra's Needle, Central Park, New York 281
Wind-Cut Rocks, Garden of the Gods, Colorado .... 282
A Tree Being Dug up by the WTind 282
A Forest on Cape Cod, Massachusetts, Being Buried in Wind-blown
Sand 283
Mount Hood, Cascade Range, Oregon ...... 286
Snow Fields at the Head of a Glacier 287
Corner Glacier 288
Crevasses in a Glacier .289
The Fiesch Glacier . . . . 290
A Stone Scratched by a Glacier .291
The Dana Glacier in the High Sierras 292
A View of the Jungfrau, Swiss Alps 293
An Iceberg 294
A Bowlder Borne along on Top of a Glacier 295
Area in North America Covered by the Ice of the Glacial Period . 296
Bowlders and Sand Left. by a Retreating Glacier .... 298
A Valley in Norway Rounded out by Glaciers . . . . . 299
Marjelen Lake 300
Alfalfa Cutting on the Fertile Prairies .... . 302
Local Soil 308
Relative Sizes of Soil Particles 310
Soil in Good Tilth , 314
MAPS AND ILLUSTRATIONS XV
PAGE
Soil Bacteria * 315
Southern Cotton Field 316
Bacterial Nodules on Bean Roots 318
Anthill. 319
Molehills . - . . 319
Lumpy Soil 320
Adobe Soil . . . . 321
Mud Cracks . .'..... . . . . .322
Prairie Scene . ...... 322
Alfalfa Root . . .; .."..' ./ 323
Rice Swamp . . v . 324
A Natural Spring 326
An Artesian Spring . ., 327
Dry Farming in Egypt . . 328
Kaffir Corn . . . , . . 329
Irrigation in Squares .•••.' , 330
Irrigation in Furrows . 331
Alkali Soil .v 332
Reclaiming Alkali Soil in the Sahara 333
Roman Plowing . . .,.-.• . . . ... . . 333
Labor-saving Machinery 334
Good Soil, a Truck Farm . , 335
East End of the Assuan Dam across the Nile 336
Results of a Sudden Flood 337
A Cypress Swamp in Louisiana before Drainage .... 337
Cypress Swamp Reclaimed ;••<;.. . . . . . . 338
Bad Lands of Dakota . . . . ... . . .339
Bad Forestry ... ... .'.'•. . .340
Bad Forestry . . » ... • ' • . . . . . 341
Bad Forestry ./. . . . . . ... . .342
Good Forestry . . . .
Good Forestry . . . • . . . . . . . - 344
A Lake Mirror , . . v;.. . . - . : . :; , . . 348
A Reflection Engine '•'••• • • • 351
Telescope Equipped with a Spectroscope . . . . . . 359
Lick Observatory . ... . . . , . . . . 360
Hospital Ward . . . • > .'•.'. . . - 362
An Old Whale Oil Lamp .... V ^- .: . i . . 363
The Grizzly Giant . . ...... . '. . -367
A Typical Plant • • ' ' • • • • -368
Roots Securely Holding the Tree Erect . . . . . • 369
A Pine Tree 374
A Splendid Tree Developed under Ideal Conditions . . .376
xvi MAPS AND ILLUSTRATIONS
PAGE
Banyan Tree '..... 377
Different Forms which Leaves Assume . . . . . . ' 379
A Pine Forest 384
A Sunflower Plant 386
Eucalyptus Leaves . . . . , . . . . 387
Flower showing Different Parts 387
Pink Gentian 388
Mint Flower 388
Ear of Corn 339
Yucca or Spanish Bayonet . . 392
Scrub Oak Branch . . 393
Mistletoe Growing on an Oak 397
Globigerina 400
Earthworm 401
Butterfly on Alfalfa • . . . . 402
Beehives . . . 404
A Human Skeleton . 405
The Nervous System of Man . 406
The Lungs 409
A White Corpuscle Digesting a Germ . ' . . . • . 411
The Circulatory System . 412
Cross Section of the Human Heart 413
Cross Section of the Human Eye ....... 414
Tloving Picture of a High Jump ........ 415
Cross Section of the Human Ear . . . . . . . 418
Proportions of Elements in Composition of Living Things . . 425
A Date Palm .......... t 427 .
A Bunch of Dates 428
Sugar Cane Cutting . 429
Banana Plants 430
Coffee Plant 432
Ancient Cooking Utensils ......... 434
One Day's Balanced Ration for Five Persons 434
Bread Mold ....'.-.... 435
Yeast Plants • 435
Bread Making in Mexico 437
Preparing Smoked Fish at Gloucester 440
Sterilizing Catsup and Chili Sauce 441
First Aid Kit ......... 442
Milk Delivery in Belgium 445
A Simple Pasteurizing Outfit 447
A Well with Contaminated Water Supply . ..... 448
Paper Drinking Cup 449
MAPS AND ILLUSTRATIONS xvii
PAGE
Sewage Disposal Bed, Solids 449
Sewage Disposal, Liquids 450
A Primitive Washing Scene in Mexico 451
A Disease-bearing Mosquito ........ 452
Amoeba Dividing 453
A " Malarial " Swamp . «... 453
House Fly . . . 454
Bacteria Colonies . . . . 455
Man's First War Machine 459
Hand Grenade Throwing 460
Battle "Tank" . . ........ . . .460
Spinning Wheel 461
Indian Weaving . . ••'_ 462
Familiar Applications of the Lever . 463
Grinding Corn, Scotch Highlands . . 464
The Lever, as Used by the Romans for Weighing . . . . 465
Combination of Pulleys Used to Lift Heavy Burden . . . 467
Inclined Railv/ay, Switzerland 468
Use of the Wedge 'v ,. , . . ..... 469
An Ancient Sail Boat ,. 470
A Simple Water Wheel Used for Grinding Corn .... 471
Electric Power Plant at Niagara 473
A Flash of Lightning 482
A Tree Completely Shattered by a Stroke of Lightning . . . 483
Electric Iron Showing Heating Element . . . . . . 486
Tungsten Lamp . .• . . 487
Simple Apparatus for Electroplating • . 488
An Electrotype 489
Electromagnetic Crane • . . . • 491
Wireless Telegraph Station, Los Angeles 494
Telephone Station in the Trenches during the World War . . 496
Dynamo . . • . . • 497
Power Plant and Dam of the Montana Power Company . . . 498
Electric Locomotive \ t . . . . . • • ' • 499
San Miguel Harbor in the Azpres 502
An Hawaiian Crater ; .».'.... . . 503
Vesuvius and Naples . . * . • - .... 505
Mount Pelee and the Ruins of St. Pierre 507
Lava Flow in the Hawaiian Islands 508
Mount Lassen in Eruption . . . . . ... . . • 509
The City of St. Helena .. .' . • . . . . • • 510
Giant Geyser in Eruption ......••• 511
Fault Line of an Earthquake . . . . .... 513
xviii MAPS AND ILLUSTRATIONS
PAGE
Fence Broken by the Slipping of the Earth along a Fault Line . 514
San Francisco Fire .......... 515
Placer Mining in the Sierras 516
Digging Peat in Ireland 517
Coal Mining in Southern Illinois . 518
Oil Wells 520
Petrified Trees 522
Skeleton of an Ancient American Elephant 523
Gila Monsters 524
Canada Thistle 525
Yosemite Falls 527
Cacti 528
Rattlesnake Coiled Ready to Spring . 529
A Herd of Reindeer ' . . . .529
California Rabbit Drive 530
Different Kinds of Seaweed 531
A Small Shark 532
Flying Fish : 534
Seals . . . . . . 534
Prickly Phlox 535
Bird's Nest 536
Double Beaver Dam and Beaver House 537
Ostriches 538
Opossum 538
Kangaroo Feeding .......... 539
The Dodo . . 540
A Cottage in the Scotch Highlands ....... 541
Cripple Creek 542
A Herd of Cattle on the Great Plains 544
A Herd of Bison 545
A Part of the Plain of Waterloo, Belgium 546
Crude Turpentine Still . . . . . . . . . . 547
Pineapples 548
Minot's Ledge Lighthouse 549
San Francisco Harbor, California, U. S. A. 550-551
EVERYDAY SCIENCE
CHAPTER I
THE OPEN SKY
Go forth under the open sky and list
To Nature's teachings. — BRYANT.
The Sun. — Our earth seems so large to us, when we
think of the time required for a trip around it, that we meas-
ure smaller things by com-
parison with it. But the
sun is so tremendous that
the earth is little more
than a dot compared with
it. To make a trip by
fast express from San
Francisco to New York
requires about four days,
and the average rate of
travel is about thirty
miles an hour. If such a
train could follow the line
of the earth's equator at
this steady rate, it could
complete the circuit of the
earth in a little less than
thirty-five days. But if
MT. WILSON SOLAR OBSERVATORY, THE
150-FooT TOWER TELESCOPE
Probably the most effective instrument
there is for studying the sun.
it were possible to make
a similar trip around the surface of the sun, more than
ten years would be required for the journey.
TUB OPEN SKY
To get an idea of the relative sizes of the earth and sun,
draw a circle an eighth of an inch in diameter to represent
the earth and alongside of it a circle of a little more than
thirteen and one-half inches in diameter to represent the sun.
The diameter of the earth is about 8000 miles, and the di-
ameter of the sun is approximately 866,000 miles. Imagine
that the sun were hollow and that the earth could be placed
at the center of this hollow sphere, with the moon just as far
away from us as it now is — about 240,000 miles. The moon
would also be inside the hollow sphere and almost as far away
from its surface as from the earth. The sun is made up of
more than 300,000 times as much matter as there is in the
earth, and it occupies more than 1,300,000 times as much
space.
Astronomers see the surface of the sun as a wild tumult of
raging flame. The outside layers are made up wholly of
incandescent gases ; but the interior, because of the enormous
pressure upon it, must be in a molten or solid condition. Stu-
pendous eruptions and tempests of flame constantly rend its
surface, causing incandescent gases to shoot up for hundreds
of thousands of miles. Sometimes furious whirling storms of
vast diameter occur. These often continue for long periods
of time, and appear to observers on the earth as sun spots.
On account of the enormous amount of heat and light
given out by the sun, it is well for us that the earth keeps
at an average distance of about 93,000,000 miles from the
sun. This distance is so great that we can have no ad-
equate appreciation of it. If an express train which could
travel the distance of the earth's circumference in about
thirty-five days, could start off into space and travel day and
night at the same steady speed in a straight line to the sun,
it would require more than 350 years to reach its destination.
THE STARS AT NIGHT 3
Of the total amount of heat radiated by the sun, the earth
receives only about one two-billionth. Yet this tiny frac-
tion of the sun's total heat furnishes practically all the energy
of the earth. It has stored the earth's crust with coal,
petroleum, and gas, from which we obtain heat, light, and
power. It lifts the waters to the hills and covers the hills
with verdure. It furnishes our food, the material for our
SURFACE EXPLOSIONS ON THE SUN
These gas flames shoot thousands of miles out from the surface of the sun.
They were photographed during an eclipse.
clothing, and the very trees that shelter us from the mid-
day sun.
The Evening Sky. — As the light of the sun fades in the
evening, we see the stars coming out one by one until at
last the sky is studded with them. We notice, too, that the
brighter the star is, the sooner it appears. In the morning
just the reverse of this takes place : the stars begin gradually
to fade, and the brightest stars are the last to disappear.
4: . THE OPEN SKY
We know how brilliant the light of a match appears in a
dark room, and how a light of this kind seems to fade out
when it is brought into the presence of a strong electric light.
It would seem quite probable that the vast light of the sun
might have the same effect upon the light of the stars. This
supposition is also supported by the fact that when the sun
is covered in an eclipse the stars begin to appear as in the
SUN SPOTS
The furiously whirling areas shown in this picture are thousands of
miles in diameter.
evening. Astronomers all agree that if it were not for the
greater brilliancy of the sun we should see the heavens full
of stars all the time.
If we carefully observe these myriads of bright points
which dot the sky at night, we shall see that almost all
of them shine with a twinkling light. There are, how-
ever, three of the brightest of them which give a steady light
like that of the moon. When the positions of these three
bodies are carefully observed for weeks or months, it will be
THE SOLAR SYSTEM 5
seen that they are continually changing their places among;
the stars, whereas the positions of the stars do not appear
to change relatively to one another.
These bright, steady-shining points are called planets,
from the Greek word meaning wanderer, and they belong to
PART OF THE MILKY WAY
There are hundreds of millions of stars in the Milky Way, so thickly strewn
that they appear to the eye as an irregular stream of light across the
sky. The plate for this photograph was exposed ten hours and a
quarter.
a family of heavenly bodies, of which the earth is one, that
make regular circuits about the sun. This family of the
sun is called the solar system. The planets are by far the
nearest of all star like bodies, although the earth's nearest
neighbor, the planet Venus, never comes nearer than 23
millions of miles. The most distant planet, Neptune, is
6 THE OPEN SKY
2700 millions of miles farther away from the sun than the
earth.
Each of the twinkling points in the heavens is a sun, shin-
ing by its own light. Our sun, if seen from the distance of
one of the nearer stars, would appear like a twinkling star.
Many of the distant stars are much larger than our sun.
A STAR CLUSTER
This cluster appears as a single star to the eye.
There is reason to believe that some of them have their
families of planets, and that our own solar system is only
one of many similar systems that exist throughout space.
The distances to these suns are so great, however, that
their brilliant lights appear little brighter in the evening
sky than the flickers of so many candles. The nearest of
these stars is probably about 25 thousand billion miles
THE DISTANT STARS 7
away, or nearly 270,000 times as far away as the sun. This
distance is so great that it takes light, which travels at
the inconceivable rate of 186,000 miles in a second of time,
A CONTINUOUS PICTURE OF THE NORTHERN HEAVENS
The telescope was held pointed at the pole of the heavens
for two hours and twenty minutes. The rotation of the
earth caused the stars to appear as white lines, as if
moving in circles.
over four and a half years to come to us from this nearest
star.
From Arcturus, another of the stars, it takes light about
180 years to reach us. In other words, the light from Arc-
8 THE OPEN SKY
turus which reaches the eye to-night left that star more
than thirty-five years before the battle of Lexington and has
been traveling toward us ever since at the rate of about
16 billion miles a day. Other stars are so much farther
away that it is impossible to measure their distances. No
wonder the lights of the stars are so. dim to us that they fade
away at the brilliant rising of the morning sun.
Experiment 1. — Early on a clear evening when the stars are
shining brightly locate the Big Dipper. (See page 10.) Carefully
determine its position by standing in a definite place and sighting
along the side of a high building or lofty tree. Make a sketch of
the position of the Dipper and some of the stars near it. Several
hours later in the evening stand in the same place and determine
in a similar way the position. Make a sketch. Has the position
of the Dipper changed in relation to your line of sight? What
caused the change? Has its position changed in relation to the
other stars? Locate some other constellations and make similar
determinations.
All the stars appear to be fixed in their relative places.
In the northern hemisphere the stars at the north appear
to go around in a circle. The other stars appear to rise in
the east and to set in the west just as the sun does. If
we observe the stars that rise to the northeast, east, and
southeast we shall find that they are above the horizon for
different lengths of time.
The ancients noticed these facts and explained them by
saying that the earth was at the center of a hollow sphere,
upon the inner surface of which were the stars, and that
this sphere was continually revolving about the earth,
and also slightly changing its position with respect to the
earth. We of the present day know that it is the earth that
is turning on an imaginary axis and also gradually changing
THE CONSTELLATIONS
its position in relation to the stars. The points on the
surface of the earth through which this imaginary axis
passes are called the poles'. If this axis were extended far
enough into space it would, at the present time, nearly
strike a star in the center of the northern heavens which we
call Polaris, or the North Star.
Due to certain causes, the
direction of the earth's axis
slowly changes so that it has
not always pointed so near to
Polaris as it now does. A
writer on astronomy reports
having visited an observatory
in China which was said to
be 4000 years old. In it were
placed originally two bronze
eye-holes on a slanting granite
wall for the purpose of sight-
ing the pole star of that era.
At the time of the astronomer's
visit in 1874, the line of sight
through these holes pointed to
a starless area in the sky.
Polaris has, however, been the guiding-star of mariners
for a thousand years, and will remain so for thousands of
years to come.
The Constellations. — Probably the first careful watchers
of the sky were the shepherds of Asia. Just as we some-
times idly try to distinguish pictures in the glowing coals
of a fire, so they by stretches of imagination grouped the
stars into constellations that very roughly resembled animals
MEDIEVAL IDEA OF THE
UNIVERSE
From a fourteenth century manu-
script. Above the earth are the
clouds and the moon ; then the
rays of the sun ; next the' vari-
ous planets; above them the
stars; and finally the signs of
the zodiac.
10
THE OPEN SKY
with which they were familiar. And so we have the con-
stellations of the Great Bear, the Little Bear, the Great
Dog, the Little Dog, the Bull, the Lion, the Eagle, etc.
The Greeks named other constellations after their heroes.
It is disappointing to see how little these star-groups resemble
the objects after which they are named, but we still retain
the groupings and
their names for con-
venience in locating
individual stars.
The Great Bear and
the Little Bear-
or, as they are more
commonly called,
the Big Dipper and
the Little Dipper —
are probably the
best known of all
the constellations
because they are al-
ways in view in the
northern heavens.
The two stars on
the edge of the Big
Dipper away from the handle are called the pointers
because they form a line that points toward the North
Star. (Figure 1.)
Our Solar Family. — We have seen that our mighty sun
and its family of planets form but a tiny fraction of crea-
tion, and that our little earth is comparatively only a speck
in the universe. Four of the eight planets that revolve
FIGURE 1. — CONSTELLATIONS IN THE
NORTHERN SKY
A , Polaris, or North Star ; 1 , Big Dipper ; B and
C, pointers; 2, Little Dipper; 3, Dragon;
4, Cassiopeia's Chair ; 5, Cepheus.
OUR SOLAR FAMILY
11
about the sun are larger than the earth, and two are nearer
to the sun than the earth. (Figure 2.) The planets in the
order of their distances from the sun are Mercury, Venus,
Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. In
the space between Mars and Jupiter there has been found
a group of small bodies which are called planetoids or
asteroids. The brightest of these is Vesta, which has a
diameter of not more
than 250 miles.
"Shooting-stars "
(meteors) are small solid
bodies flying rapidly
through space. Some-
times they enter our at-
mosphere and become
heated by friction while
passing through it. Be-
cause they are thus
heated they give off light.
Sometimes they fall to
thp parth as m pf write* Showing roughly the positions of the
various planets and their moons.
but more frequently they
simply pass through the upper part of the atmosphere.
They are in no sense true stars.
Size and nearness to the sun are not the only respects
in which the planets differ from each other. The surfaces
of the planets Jupiter and Saturn, for example, are not solid
like the surface of the earth. Saturn has ten moons to the
earth's one. Venus and Mercury have none. The planet
Mercury, nearest neighbor to .the sun, must receive a with-
ering heat; while the temperature of Neptune, the most
distant planet, is probably colder than we can imagine.
FIGURE 2. — DIAGRAM OF THE SOLAR
SYSTEM
12
THE OPEN SKY
The speed of the planets in their orbits and the length of
their paths about the sun vary widely. Mercury travels
through space about eight times as fast as Neptune, and
completes its comparatively short trip around the sun in
about 88 days. Neptune requires 164 years to traverse
its vast orbit once.
Astronomers have never satisfactorily determined what
the length of day is on Mercury, Venus, Uranus, or Nep-
tune— the two
planets closest to
the sun, and the
two most distant.
A day on Mars dif-
fers but little in
length from the 24-
hour day of the
earth, but Jupiter
and Saturn whirl
completely around
on their axes once
in about every ten
hours. The change
of place of planets
A LARGE METEORITE . . .
in their relations to
A shooting-star which fell to the earth.
each other and to
the stars is owing to their respective motions about the
sun.
The three planets which shine most brightly for us are
Venus, Jupiter, and Mars. To the naked eye Venus is the
most magnificent planet in the solar system, exceeding in
light and beauty the brightest sfcar. It is therefore called
by the name of the Roman goddess of beauty. Jupiter,
OUR SOLAR FAMILY
13
the largest of the planets (317 times as heavy as the earth)
takes its name from the king of the Roman gods. Mars
shines with a reddish brown color, and on this account
bears the name of the Roman god of war. Saturn is plainly
visible at times, but the bright concentric rings, composed
of little moonlike bodies that surround it and revolve about
it, can be seen only
with a telescope.
When once in about
every fifteen years
Saturn is so situated
that we have a view
of the broad side of
these rings, the tele-
scope reveals what
is probably the most
beautiful sight in
the solar system.
Mercury is so close
to the sun that it
can be seen by the
naked eye very
rarely; Uranus can
be singled out only
by very sharp eyes; and Neptune is so far away that it
cannot possibly be seen without the aid of a telescope.
The planets have no light of their own, as do the true
stars, but the light which comes to us from them is a re-
flection of the light of the sun. When the astronomer turns
his telescope on Neptune and .its moons, he sees it by rays
of light which, in making the trip from the sun to Neptune
and, by reflection, back to the earth, have traveled five
MARS
Most like the earth of all the planets. It is
supposed to have a polar ice cap. The noted
astronomer Lowell argues that Mars may
be inhabited.
14
THE OPEN SKY
THREE VIEWS OF SATURN
The planet with the beautiful rings.
and a half billion miles — the longest reflected rays of light
known to man. If we could stand upon any one of the
nearer planets, our earth, reflecting the rays of the sun,
would also appear as a point of steady light in the heavens.
SURFACE OF THE MOON
Showing the great crater-like depressions.
THE MOON
15
The Moon. — We have learned that certain of the planets
are accompanied by smaller bodies which are called satel-
lites or moons. These moons revolve about their planets
just as the planets revolve around the sun. Our own
moon revolves
around the earth at
an average distance
of about 240,000
miles and makes the
circuit of its orbit in
a little less than a
month. Primitive
people measured time
by "moons." This
is the origin of the
word month.
The moon turns
only once on its axis
during a revolution
around the earth,
and so it always
keeps the same side
toward us. Its
periods of daylight
and darkness are,
therefore, about 14
of our days long.
The moon has a diameter of about 2000 miles and its
weight is about one-eightieth of that of the earth. It has
no air or water on its surface. Since it has not the leveling
influence of wind and rain and freezing water, the surface
is very jagged. It is covered with great crater like
PHASES OF THE MOON
Showing roughly the varying positions of the
sun, moon, and earth.
16
THE OPEN SKY
depressions, some of which are more than 100 miles in
diameter.
Although we see the moon as a very bright object at night
for a part of every month, yet it has no light of itself, and
all the light it gives us is reflected from the sun. Astronomers
tell us that we receive more heat and light from the sun in a
quarter of a minute
than from the moon in
a whole year.
As the earth goes
around the sun and
the moon around the
earth, the position of
these three in relation
to each other is con-
stantly changing. It is
profitable to try to
picture to oneself the
changing phases of the
moon. Study the dia-
gram of the moon's
phases, and see what
the relative positions of the sun, earth, and moon are from
the new moon to the dark of the moon.
It must sometimes happen that >the moon comes directly
between the earth and the sun. The moon is so much
smaller than the earth, however, that it does not cut off
the face of the sun from the whole surface of the earth, but
merely from a comparatively narrow path. For hundreds
of miles on each side of this path of total eclipse of the sun,
observers see a partial eclipse. It is during a total eclipse
that the pictures of eruptions of incandescent gases on the
TOTAL ECLIPSE OF THE SUN
From a photograph taken June 8, 1918.
THE MOON
17
sun's surface are taken. These form a corona, or crown of
light, on the surface of the sun that surrounds the black
outline of the moon. It must also happen at times that
the earth comes between the moon and the face of the sun.
If the earth's path lies directly between the two bodies, its
shadow wholly obscures the face of the moon for a short
time. This is called a total eclipse of the moon.
HALLEY'S COMET
One of the most famous visitors from outer space. The small white
dots are stars seen through the comet's tail.
If it were not for the moon, the beauty and variety of
our nights would be largely lacking. Moreover, as we shall
see later, we should have no tides strong enough to help
vessels over the bars into some of our harbors, and to
sweep clean our bays, removing the sewage. If the
distance of the moon were changed, the height of the
tides would be changed, and this would greatly affect our
coast towns.
18 THE OPEN SKY
Comets. — Sometimes comets appear in the sky and
excite the greatest wonder. They usually have a very bright
spot as the nucleus of a head, which shades gradually into
a less luminous tail that streams across the sky for millions
of miles. Some of the comets travel in great orbits around
the sun and appear at regular intervals. They may be
considered as part of the solar system. Others have ap-
peared once and then have disappeared, never to return.
Halley's comet is probably the best known of all the comets.
It takes about 75 years to make a trip around its orbit
and was last seen in 1910. It was named after the English
astronomer Halley because, by mathematical calculations,
he traced its history to almost the beginning of the Chris-
tian era, and prophesied correctly the year of its next
return.
SUMMARY
The sun is more than 100 times greater than the earth in
diameter and in circumference, and more than a million times
greater in volume. It appears as a tremendous ball of flame,
and is the source of the earth's heat and light.
The few steady-shining points of light in the evening sky
which are constantly changing their positions among the
stars are planets. These, like the earth, revolve in regular
orbits about the sun as a center. Each of the myriads of
twinkling stars is a sun, shining by its own light. There is
reason to believe that many of these suns have planets re-
volving about them. The nearest of the stars is thousands
of billions of miles away, and the distances of remote stars
from the earth are immeasurable. The ancients thought
that the earth was the center of the universe and that the
heavenly bodies revolved about it, but we know that the
QUESTIONS 19
apparent motions of the stars are owing to the earth's move-
ments on its axis and around the sun.
The ancients grouped the stars into • constellations which
vaguely represented animals or ancient heroes. Modern
astronomers retain these groupings for convenience in study-
ing the heavens.
The sun's family consists of eight planets and their satel-
lites or moons, the asteroids, and occasional solar visitors
called comets. The planets differ from each other in size,
nearness to the sun, temperature, number of satellites, length
of orbit, rate of speed, time of rotation, time of revolution,
and in many other ways. They shine only by the reflected
light of the sun.
All satellites revolve about the planets they accompany.
Our own moon revolves about the earth at an average dis-
tance of 240,000 miles. It rotates once on its axis and travels
once around the earth in a little less than a month. The
moon's revolution about the earth accounts for its changing
phases, for eclipses both of the sun and of the moon, and for
our ocean tides.
QUESTIONS
What are the most impressive facts about the sun ?
Why do we not see the stars in daytime ?
How do the planets differ from stars ?
Why are the lights of the stars so dim to us ?
Do the stars appear to change their relative positions in the sky
from time to time ? What makes them appear to revolve around
the earth?
In what respects do the planets differ from each other ?
What are the most interesting facts about the moon? What
accounts for its changes of appearance ?
What causes an eclipse of the sun? Of the moon?
What is a meteorite ? a comet ? a constellation ?
CHAPTER II
OUR OWN WORLD
The Development of Earth-Science. — From earliest
times men have earnestly sought to increase their knowledge
AMALCHIUM MARE
THE WORLD ACCORDING TO HECAT^EUS (500 B.C.)
about the earth. The ancient Assyrians and Babylonians
early determined the definite directions which we call north,
20
THE SHAPE OF THE EARTH 21
east, south, and west; and carefully built the sides of their
temples and palaces to correspond with these directions.
The Egyptians developed the science of geometry (earth-
measuring) primarily for the purpose of measuring land areas.
The great poet Homer shows that the Greeks of his time
had made many careful observations of the earth's surface,
as well as many ingenious guesses about it. He conceived
the earth as a circular plane surrounded by the Ocean, a
broad and deep river, which was the source of all waters.
Homer's idea of the shape of the earth
held sway for hundreds of years. As
time went on, however, more and more
was learned about the earth, until to-day
a great amount of accurate knowledge
has been acquired, which is of the ut- FIQURE 3. —
value to mankind. i' GRAM SHOWING
THE SHAPE OF THE
EARTH
The Shape of the Earth. — Men who Any drawing which
have in different ways made careful
measurements of the shape of the earth poles and the buig-
. 7-7 ing a* the equator
tell us that it is an oblate spheroid is Of necessity tre-
(Figure 3); that is, a sphere which is ^dously exagger~
somewhat flattened at two opposite points.
An ordinary orange has this shape. The earth has been so
little flattened, however, that its shape is very much nearer
that of a perfect sphere than is that of an orange. Its
polar diameter is only 27 miles shorter than its equatorial
diameter; and so when we consider that each of its diame-
ters is nearly 8000 miles, a shortening of only 27 miles in
one of these would not change its shape from that of a
sphere enough to be noticed e&£ept by the, mpst careful
measurements.
22
OUR OWN WORLD
Experiment 2. — Attach a centrifugal hoop to a rotator apparatus
and revolve. The hoop bulges at the center or point of greatest
motion and flattens at the top and bottom or points of least motion.
The earth revolves in a way similar to the hoop and is very slightly
flattened at the poles.
Although some of the mountains of the earth rise above
sea level to a height of over five miles, and there are depths
in the sea which are somewhat greater than this below sea
level, yet these distances are so little in comparison to the
size of the earth that the surface
is comparatively less irregular
than that of an orange.
In these days many men have
sailed around the earth; but
valiant indeed was that little
company which in 1522 first
proved that it was possible to
sail continually in one 'direction
and yet reach the home port,
thus demonstrating that the earth
was probably round. Long be-
fore, wise men had come to
believe that the earth was a sphere, for it had been noted
as far back as the time of Aristotle, the famous Greek
philosopher, that when the shadow of the earth fell upon
the moon, causing an eclipse of the moon, the boundaries
of the shadow were curved lines. It was also later noticed
that when ships are seen approaching at sea the masts ap-
pear first and then gradually the lower parts of the ship ;
and when ships sail away, the lower parts disappear first.
PARTIAL ECLIPSE OF THE
MOON
Showing the curved outline
of the earth's shadow.
Experiment 3. — Add alcohol to water until a solution is obtained
in which common lubricating oil will float at any depth. Insert with
THE EARTH'S ROTATION 23
a glass tube a large drop of oil below the surface of the solution.
The oil will float in the solution in the shape of a sphere. This illus-
trates the fact that if a liquid is relieved from the action of outside
forces, it will take the form of a perfect sphere.
A spherical surface is the smallest surface by which a
solid can be bounded, and so the maximum distance which
can separate places located on a given solid will be least
when its surface is spherical. Thus the inhabitants of
the earth, considering the surface over which they may
scatter themselves, are brought into the closest possible
relation to one another.
The Size of the Earth. — It is easy to say that the polar
diameter of the earth is 7900 miles, its equatorial diameter
BOSTC.fr ?TO CHICAGO lOOO MILES
DIAMETER OF EARTH 8OOO MILES
CIRCUMFERENCE OF EARTH 25OOO MILES
FIGURE 4. — LINES TO INDICATE COMPARATIVE DISTANCES
7927 miles, and its equatorial circumference 24,902 miles,
but a true conception of these distances is not so easy.
Using as our standard any distance with which we are
really acquainted, we shall find that the lines representing the
different dimensions of the earth are very long. (Figure 4.)
How vastly greater, then, must be the distances which were
mentioned when treating of the sun and the stars !
The Earth's Rotation. — As has already been stated, the
ancients considered the earth as the center of the universe
and thought that the sun and stars revolved around it.
We of the present day, however, know that it is the rotation
of the earth from west to east that causes the appearance of
the rising and setting sun and thus makes day and night.
24 OUR OWN WORLD
Of course it makes no difference to the eye whether a
light is brought toward the observer or the observer goes
toward the light. We are turned into and out of the
sunlight by the rotation of the earth. We speak of the
sun as rising high in the sky, but what really happens is
that we are turned so that the center of the earth, our
heads, and the sun come nearer and nearer toward a straight
line.
When we say down we mean toward the center of the
earth, and when we say up we mean in the opposite direc-
tion. These are the only two directions that we could be
easily sure of, if it were not for the rotation of the earth.
This rotation gives the direction of the rising sun, which we
call east, and of the setting, which we call west. A line which
runs at right angles to the one joining east and west, i.e.
one running parallel to the axis of the earth, is said to run
north and south. Thus the points of the compass, as well
as day and night, are determined for us by the earth's rota-
tion. The north star, which is so important to the sailor
in determining his direction, is simply a star which is almost
in line with the axis of the earth.
The rotation of ; the earth gives us also our means of measur-
ing time.
Days and Nights of Varying Length. — Experiment 4. — (A) In
a darkened room place a globe a short distance from a small but strong
light. Rotate the globe with its axis at right angles to the line
which joins the centers of the globe and light. (Figure 5, A.)
How much of the globe is illuminated by the light ? Is the same
part of the globe illuminated all the time ? Does any place receive
light for a longer time during a rotation than any other place?
Remove the globe to the opposite side of the light without chang-
ing the direction of its axis. When rotated, is there any change
in the globe's illumination?
THE EARTH'S ROTATION 25
(B) Now make the axis on which the globe rotates parallel to the
line joining the centers of the globe and light. (Figure 5, B.)
Rotate the globe. How much of the globe is illuminated by the
light? Is the same part illuminated all the time? Does any
place receive light for a longer time during a rotation than any
other place on the globe ? Remove the globe to the opposite side
of the light without changing the direction of its axis. When
the globe is rotated, is there any
change in its illumination? If
so, what ?
(C) Place the globe so that
its axis is inclined about 25
degrees from the perpendicular
to the line joining the centers
of the globe and light. (Figure
5, C.) Rotate the globe. How
much of it is illuminated? Is
the same part illuminated all
the time? Do any places in
the illuminated part receive
light for a longer time during
a rotation than other places ? FlGURE 5.- RELATIVE POSITIONS OP
Remove the globe to the op- GLOBE AND LIGHT
posite Side of the light with- Corresponding to A, B, and C of
out changing the direction of Experiment 4.
its axis. When the globe is
rotated, is there any change in the length of time of illumination
of the places before noted? If so, what?
As was seen in the previous experiment, the direction of the
axis of a rotating globe has much to do with the light which
different parts of it will receive from a luminous object.
When the axis of the revolving globe was at right angles
to the line joining the globe and the light, no place on the
surface of the globe received light for a longer time than any
other place. This was not true when the axis was at any
other angle.
26 OUR OWN WORLD
As the axis of the earth is inclined to a line drawn from
the earth to the sun, the light the earth receives is similar
to that received by the globe in the last part of the experi-
ment. Thus the days and nights vary in length during
the year, because in summer the northern hemisphere is
inclined toward the sun and in winter away from it.
The Movement of the Earth around the Sun. — The earth
not only turns on its axis every day, but it travels around
the sun, continually changing its position in relation to
the stars. It moves with the
tremendous average velocity
of about 19 miles a second.
It is this revolution around
the sun which gives us our
measure of time which we
call a year. It takes 365
days and a fraction to com-
FIGURE 6. — DRAWING AN ELLIPSE Plete this revolution; and so
we consider 365 days to be a
year, and add a day practically every fourth year to
account for the fractions.
In the journey around the sun, the earth does not move
in a circle but in an ellipse. To draw this figure, stick
two pins into a piece of cardboard, a short distance apart.
Place over the two pins a loop of string, and with the
point of a pencil draw the loop taut as in Figure 6. If the
loop is kept taut as the pencil point moves around the two
pins, the .resulting curve will be an ellipse.
The points where the pins pierce the cardboard are called
the foci. Draw a straight line to join the foci, and extend
the line to cut the ellipse at two points. Now place a small
THE CAUSE OF THE SEASONS
27
object at one of the foci, and move another small object
around the ellipse. The two objects will be closest together
when the moving object reaches one of the two points where
9I,5OO,OOQMILES
SUMMER WINTER
FIGURE 7. — THE EARTH'S VARIATION OF DISTANCE FROM THE SUN
the straight line cuts the curve, and farthest apart when it
reaches the other point of intersection.
Now the sun is at one of the foci of the ellipse in which
the earth moves, and so the distance between the sun and
the earth varies during the year. This variation is about
three millions of miles, the average distance of the earth
from the sun being about 93,000,000 miles. Strange as it
may seem, we are nearest
the sun in January and
farthest away in July.
(Figure 7.)
MAH.CH [QUINQX
The Cause of the Sea-
sons. — Since the earth
moves around the sun
with its' axis inclined 23^°
from the perpendicular to
the plane of its orbit, the
northern and the southern
hemisphere will at different times be inclined toward and away
from the sun. (Figure 8.) In July the earth is farthest away
from the sun, but the northern hemisphere is then pointed
toward the sun, and the rays of heat from the sun fall more
nearly vertically upon this hemisphere than during the rest
SEPTEMBER CQUINOX
FIGURE 8. — THE PATH OF THE EARTH
AROUND THE SUN
Showing roughly the four positions men-
tioned in the text.
28
OUR OWN WORLD
of the year. The more nearly vertical the rays, the greater
the number that fall upon a given area, and the greater the
amount of heat received by that area. In January we
are closest to the sun, but its rays strike our hemisphere
more aslant and therefore fewer heat rays fall upon a given
area than in July.
Experiment 5. — Cut a hole 4 in. square in the center of a board 12
in. square. Fit tightly into this hole one end of a wooden tube 4 in.
square and 1 ft. long. Paint the inside and outside of the tube a dull
black. Hinge the opposite end of this tube 10 in. from the end of a
baseboard 2 ft. long
and 16 in. wide,
having 6 in. of the
board on either side
of the tube. (Fig-
ure 9.)
On a clear day
place this appara-
tus out of doors on
a • table freely ex-
posed to the sun,
with a piece of
paper on the baseboard under the end of the tube. Point the tube
directly at the sun in the early morning, in the middle of the fore-
noon, at noon, in the middle of the afternoon and about sunset.
Mark on the paper the amount of surface illuminated by the sun-
light passing through the tube at each of these different times. Why
are different amounts of surface covered at these different times ?
Place a thermometer in the centers of the surfaces covered by
the sunlight passing through the tube at these different times. Note
the different readings of the thermometer. Can you suggest a reason
why they are not alike ? The opening exposed to the rays has been
the same throughout the experiment. Draw diagrams illustrating
the action of the sun's rays in the different positions.
The number of rays of the sun which fall upon a given
area depends upon the angle at which they strike the sur-
FIGURE 9. — APPARATUS FOR SHOWING THE
HEATING EFFECTS OF SUN'S RAYS
THE CAUSE OF THE SEASONS • 29
face. Figure 10 shows that the same number of rays fall
upon a much smaller surface when the direction of the sun
is vertical than wh,en it is nearly horizontal. In the 30-
degree arcs there are 2^-, 7, and 9^ ray spaces respectively.
The sun is here considered to be vertical at the equator,
as it is on March 21, and September 23. Thus on these
days, other conditions being the same, about one fourth
FIGURE 10. — HEATING EFFECTS OF SUN'S RAYS
Heating effects depend upon the angle at which the sun's rays strike
the earth's surface.
as much heat from the sun falls upon the 30° about the
pole as upon the 30° north of the equator.
When the northern hemisphere is inclined toward the
sun, the rays of the sun cover the north pole continuously
for six months, so that at this point there is no night for all
that time. The days are longer and the nights shorter
throughout all the northern hemisphere. More heat is,
therefore, received in the northern hemisphere during these
six months, not only because the rays of the sun fall more
nearly vertically but also because the length of the day is
increased.
30 • OUR OWN WORLD
The amount of heat received from the sun continues to
increase as long as the sun appears to move north. The
rays of the sun strike vertically the farthest point north on
the 22d of June. This is called the summer solstice. At
this time our days are the longest and our nights are the
shortest. But the days are not the hottest, as the heat
A HUT IN THE TROPICS
Having thin walls, but a heavy thatched roof to keep out the rain.
gradually accumulates for some time, more being received
each day than is given off.
As the earth proceeds in its orbit from this point, the
inclination of the north pole toward the sun becomes less
and less, until on the 23d of September the sun is directly
over the equator. The north pole now begins to point
away from the sun. On December 22, the direct rays of
the sun fall upon the farthest point south, our days being
THE CAUSE OF THE SEASONS
31
then the shortest and the days in the southern hemisphere
the longest. From this point until March 21, when the sun
is again vertical over the equator, the inclination of the north
pole away from the sun decreases. The days when the
sun is over the equator are called the autumnal (Sept. 23)
and vernal (March 21) equinoxes, since the days and nights
are then of equal length all over the earth.
The greater heat-
ing of the hemisphere
at one part of the
year than at another
gives us the changes
which we call the
Since the
A LAPLANDER'S HUT
Made of thick sod to retain heat in
the frigid zone.
seasons.
change in the length
of the day and in the
direction of the sun's
rays is very small
within the tropics, the
change in the amount
of heat received is
very slight, so that
in this region there
is almost no change of seasons. But at the poles, where for
six months there is continuous night and for six months
continuous day, the change of seasons is exceedingly great.
At middle latitudes the changes, though marked, are not
excessive.
There are then two causes which combine to give us our
change of seasons : the revolution of the earth around the
sun. and the inclination of the earth's axis to the plane of
its orbit.
32
OUR OWN WORLD
Meridians and Parallels of Latitude. — For purposes
of measurement, circles of any size are divided into 360
equal parts called degrees. Thus the equatorial circle of
the earth is divided into 360 parts. Through each of these
divisions there is a semicircle drawn from pole to pole. These
semicircles are called meridians. Each meridian is divided
into 180 parts called degrees of latitude, and through these
points of division are passed circles parallel to the equator.
These circles gradually decrease in size from 25,000 miles at
the equator to points at the poles. They are called parallels
of latitude and are numbered
from 0 at the equator to 90 at
the poles. (Figure 11.)
A certain one of the meridians,
usually the one passing through
Greenwich, England, is called
the prime meridian and num-
bered 0. East and west of this
the meridians are numbered
from 1 to 180. The degrees
thus numbered are called degrees
of longitude. Thus we have a skeleton outline by means
of which we are easily able to locate the position of any
place upon the earth. To secure greater accuracy than
could be obtained by giving merely the degrees of latitude
and longitude, each of these degrees is divided into 60
equal parts called minutes, and each minute can be divided
into 60 parts called seconds.
The Measurement of Time. — Experiment 6. — On a fair day
place a sundial in an exposed position, and after carefully adjust-
ing it, compare its readings with those of an accurate watch. Unless
you are on the time meridian, the readings are not alike.
FIGURE 11. — MERIDIANS AND
PARALLELS OF LATITUDE
MERIDIANS AND PARALLELS OF LATITUDE 33
Although the exact determination of time is a difficult
task and requires great skill and very accurate instru-
ments, yet it is not very hard to determine quite satis-
factorily the length of a solar day. Before there were any
clocks, people told the time of day by sundial (Figure 12),
which consisted of a vertical " pointer " the shadow of which
fell upon a horizontal plane. From local noon, or the
time the sun cast the shortest shadow on a certain day,
until it cast the shortest shadow the next day, was con-
sidered a day's time, or
a solar day, and was
divided into twenty-four
equal parts called hours.
The direction of the
shortest shadow is a
north and south line,
since the sun must then
be halfway between the
eastern and western ho-
rizon. As the lengths of
these solar days vary
slightly, for reasons which cannot be explained here, we
now divide the mean length of the solar days for the year
into twenty-four parts to get the hours.
The civil or conventional day begins at midnight, not noon.
The determination of the exact time is very important;
for the United States it is done at the Naval Observatories
at Washington and at Mare Island, San Francisco, and
telegraphed each day to different parts of the country.
Experiment 7. — On a day when there appear to be indications of
settled fair weather place a table covered with blank paper in an
open space where the sun can shine upon it. Make the top of the
FIGURE 12. — A SUNDIAL
34
OUR OWN WORLD
table level and fix it firmly so that it cannot be moved. Fix ver-
tically upon the table a knitting needle or a slender stick. Mark
the line of the sun's shadow and note accurately the time the
shadow falls on this line. On the next day note the time the shadow
falls upon the same line. If your watch is right, the difference in
tune it shows between the falling of the shadows the first and the
second day is the difference between this particular solar day and
the mean solar day. This may be nearly a minute. The shortest
shadow of the day marks noon. It extends north and south.
(Your watch keeps mean solar time. But twelve o'clock by your
watch will probably not be midday or high noon, as your watch
is set to Standard Time.)
Standard Time. — When railways extending east and
west became numerous in the United States and there
MAP SHOWING STANDARD TIME BELTS
were many through trains and numerous passengers, it
became very inconvenient to use local time, since no two
places had the same time. Each railway therefore adopted
a time of its own, and when several railways entered the
INTERNATIONAL DATE LINE 35
same city, these different times became very confusing.
Therefore in 1883 the American Railway Association per-
suaded the Government to adopt Standard Time.
A certain meridian was adopted as the time meridian
for a definite belt of country. The meridians adopted
were 75° for Eastern, 90° for Central, 105° for Mountain,
120° for Pacific Time. These meridians run through the
centers of the time belts and for 7J° on either side the time
used is the local time of the central meridian. When a
person crosses from one belt to another he finds that the
time makes an abrupt change of an hour. This system has
been extended to all the United States possessions, and is
coming into general use over a large part of the world.
In actual practice the changes of time are not made where
the boundaries of the time belts are crossed, but at im-
portant places near these.
International Date Line. — If a person should start at
noon and travel around the earth from east to west as fast
as the sun does, the sun would be overhead all the time and
no solar day would pass for the traveler, even though 24
hours would be required for the trip. But when he reached
home he would find that a calendar day had passed. This
shows the necessity of having some generally accepted north
and south line on the earth's circumference from which
to reckon the beginning and the ending of a day.
Since the earth rotates once on its axis (the full 360 de-
grees of its circumference) in 24 hours, it turns in one hour
A- of its circumference, or 15 degrees. Places on the earth's
surface that are 15 degrees apart in an easterly-westerly line
may, therefore, be regarded as an hour apart in time. Since
the meridian of Greenwich is usually considered the 0 Meri-
36
OUR OWN WORLD
dian, let us suppose it is high noon of Sunday at Greenwich.
For every 15 degrees west of that point it will be an hour
earlier, until at the 180th meridian it will be midnight of
Saturday. For every 15 degrees east of Greenwich it will
MAP SHOWING INTERNA.TIONAL DATE LINE (Dotted line)
In the northern hemisphere, the Date Line varies from the 180th meridian
so as to divide Asia from North America ; in the southern hemisphere,
so as to include certain English dependencies with Australia and New
Zealand.
be an hour later, until at the 180th meridian it will be mid-
night of Sunday.
Thus, on one side of this line it would be Saturday mid-
night, and on the other side Sunday midnight. This repre-
sents the actual state of affairs. The 180th meridian, which
MAGNETISM OF THE EARTH 37
extends through the Pacific Ocean, is the accepted line
which separates one day from the next. Thus any one
traveling around the earth must drop a day from his
calendar if crossing this line toward the west, and repeat a
calendar day if crossing the line toward the east.
In practice, the International Date Line, where this
arbitrary change of day occurs, does not quite coincide with
the 180th meridian. A glance at the accompanying map
will show why it is convenient to vary the Date Line from
the meridian line.
Daylight Saving. — In midsummer the sun rises between
4 and 5 o'clock in middle latitudes. Thus it is well up in
the heavens before the average citizen is astir. On the first
of April, 1918, the United States Government decided to
set the clock ahead one hour. This gave more daylight in
the ordinary waking hours, and thus effected a saving in
the cost of lighting. On the 27th of October, when the
long days were past, the clock was set back one hour, and
normal time was resumed. Many countries did this during
the War.
Magnetism of the Earth. — There is a peculiar prop-
erty of the earth which has been of the greatest assistance
to geographical explorers and without which it would be
very difficult to find a way over the sea. This property
is called terrestrial magnetism. In very ancient times
pieces of iron ore were found which had the property of
attracting iron. Such pieces of ore are called loadstones.
Artificial loadstones are called magnets.
Experiment 8. — Having pushed a long cambric needle through
a small disk of cork so that it will float horizontally, carefully
place the disk and needle upon the quiet surface of a large dish
38
OUR OWN WORLD
of water. Does the needle assume any definite direction? Taking
the needle from the water stroke one end of the needle from the
cork out with the north end of a magnet and the opposite end
with the south end of a magnet. When the
needle is again floated on the water is it in-
different about the direction in which it points ?
FIGURE 13. e discovery that a bar of loadstone
or a magnetic needle, if floated or freely
suspended, will invariably assume a definite position was
made in the Far East at a very early date, but it was put
to no particular use in the sailing of ships until about the
middle of the thirteenth century. Since then it has
enabled sailors to go far out from the sight of land and
yet always to know the direction in which they are going.
It was supposed even up to the time of the first voyage of
Columbus that
the magnetic
needle always
pointed toward
the north star or
perhaps at some
place a little to
the east of it.
The sailors of
Columbus were
greatly alarmed
when they found
as they sailed
REGION AROUND THE NORTH MAGNETIC POLE
The + marks the position of the pole.
west that the needle swung off to the west of the true north.
This difference in the direction of the needle from a true
north and south line is called the declination. The west-
ward declination was one of the great discoveries of Colum-
MAGNETISM OF THE EARTH 39
bus. We know now that the reason for the declination
of the needle is that the north end of it does not point
toward the north geographical pole as was at first supposed,
but toward a point in the southwestern part of Boothia
Felix which is called the north magnetic pole. The south
magnetic pole as recently determined is a little to the east
of Victoria Land.
These magnetic poles do not remain in the same place all
of the time but swing slowly back and forth, so that the
declination changes for the same place. On account of
this it is necessary for surveyors, who use the compass, to
find out the declination each year. The annual change in
the United States varies from 0 to 5 seconds.
SUMMARY
The ancients thought that the earth was flat ; but modern
scientists have proved in many ways that it is an oblate sphe-
roid, slightly flattened at the poles and bulging at the equator
— somewhat resembling an orange in shape. Its polar diam-
eter is 7900 miles ; its equatorial diameter is 7927 miles, and
its equatorial circumference is 24,902 miles.
The rotation of the earth on its axis gives us our days, the
points of the compass, and our means of measuring time.
The earth revolves about the sun once a year, not in a
circular, but in an elliptical, orbit. Its average distance
from the sun is 93,000,000 miles, but it is 3,000,000 miles
closer to the sun in our winter than in our summer. Since
the axis of the earth is inclined 231 degrees from the perpen-
dicular to the plane of its orbit, the northern hemisphere in
summer is pointed toward the sun and in winter away from
it. It is not closeness to the sun but directness of its ray
that gives us our summer heat. The inclination of the earth
40 OUR OWN WORLD
on its axis as it moves around the sun, therefore, accounts for
our changing seasons. This inclination also accounts for the
varying length of our days and nights.
We locate places on the earth's surface by means of imagi-
nary circles drawn around the earth, which are called merid-
ians and parallels of latitude. From the equator in either
direction to the poles is a quarter of a circle or 90°. From
a zero meridian we measure a half circle, or 180°, east, and
180° west.
From the time the sun casts the shortest shadow one day
until it casts the shortest shadow the next is a solar day.
Solar days differ slightly in length ; and so, for convenience,
a calendar day is the average of the solar days of the year.
To avoid the endless confusion that would be caused by each
community having its own local time, the United States is
divided into belts 15° wide. Throughout one of these belts,
standard time is the same, and each belt differs by one hour
in time from a neighboring belt. The International Date
Line (about the 180th meridian) is the line which for con-
venience marks the beginning and ending of a calendar day.
Setting the clock ahead one hour during the summer months
gives more daylight during working hours. This is called
daylight saving.
The earth has a north and a south magnetic pole. These
do not correspond with the poles of the earth's axis, nor do
they remain stationary. The attraction of these poles for
the magnetic needle or compass enables mariners always to
determine direction.
QUESTIONS
What simple reasons are there for believing that the earth is
round?
Draw circles illustrative of the size of the earth, moon, and sun.
QUESTIONS 41
What was discovered in the experiment with the globe and the
light?
How have the movements of the earth around the sun, its rota-
tion on its axis, and the direction of its axis, affected the conditions
of your life?
Why do we have winter in the northern hemisphere when the
earth is nearest the sun ?
If a man should leave Cairo, Egypt, on June 21 and travel slowly
to Cape Town, reaching there on Dec. 21, what changes of season
would he experience?
How is the length of the day determined? If it were noon
Thursday, Sept. 30, with you, what would be the day and date at
Yokohama ?
What are the advantages of Standard Time ?
What are the reasons for the establishment of an International
Date Line?
If it is twelve o'clock local time at your home, wThat time is it at
Paris? At Honolulu?
Why is the magnetism of the earth of so much use to man?
CHAPTER III
PKOPERTIES AND MAKE-UP OF MATTEK
Forms of Matter. — The earth and the heavenly bodies
are composed of a very great number of different substances.
With some of these, such as iron, water, air, soil, plants,
etc., we are all familiar. These, as well as all other sub-
stances, are called matter. In short, as scientists say, any-
thing that occupies space — takes up room — is matter.
Matter is known to us in three forms : solids, liquids,
and gases. All substances exist in one of these three forms.
The forms of water are the most familiar illustrations of this
truth : the most common form in which water is found is
liquid ; but as ice it is a solid, and as steam it is a gas. Met-
als such as iron, copper, tin, etc., may easily be changed
by heat from a solid to a liquid form. Many metals found
on the earth have been proved to exist as gases in the sun.
Properties of Matter. — Man is unable to comprehend
how matter came into being, or how it can ever be utterly
destroyed; but he does know many of the properties of
matter.
Experiment 9. — Pull out the handle of a compression air-pump
or bicycle pump. Close the exit valve or stop up the end of the
bicycle pump. Now try to push in the handle. What keeps it
from moving easily ?
Try to shove an inverted drinking glass into a pail of water.
(Figure 14.) Why does not the water fill the glass?
42
PROPERTIES OF MATTER
43
FIGURE 14
In the experiment with the air compressor we found that
the space occupied by the air could be reduced only to a
limited extent. Greater force might have compressed the air
into smaller space, but no amount
of force could reduce the air to a
point where it did not occupy at
least some space. When we pump
up a bicycle tire, we see again that
air demands room for itself. These
examples illustrate the truth that
all matter occupies room or space. This property of matter
we call extension.
Experiment 10. — Place a coin on a smooth card extending
slightly beyond the edge of a table. (Figure 15.) Suddenly snap
the card horizontally. Does the coin move?
When the card was snapped from under the coin, the coin
moved very slightly, if at all. The force of the finger was
applied only to the card, and
the card was so smooth that it
did not convey any appreciable
motion to the coin. If the coin
had been glued to the card, both
coin and card would have moved.
This illustrates the truth that a body at rest does not
begin to move unless some force acts upon it.
Experiment 11. — Revolve around the hand a small weight at-
tached to a strong rubber band. Suddenly let go the band. Does
the weight keep on moving in the circular path in which it was
revolving?
When we let go the band, the weight started off in a
straight line. (Figure 16.) It did not continue in a straight
FIGURE 15
44
PROPERTIES AND MAKE-UP OF MATTER
FIGURE 16
line because a force called gravity pulled it down toward the
earth. When a train is moving along a straight level track,
we do not expect it to stop until the friction of the track or
some other force stops it. A bullet fired
from a gun will continue to move until
it hits some unyielding object or is
pulled to the earth by gravity. Thus
we see that a moving body does not stop
unless some force compels it to stop.
We may sum up these observations in
the following words : A body at rest
remains at rest unless acted upon by some force; a body
in motion continues to move in a straight line at the same
speed unless acted upon by an outside force. This property
of matter is called inertia. Sir Isaac
Newton first stated these facts, and so
they are sometimes called Newton 's First
Law. We see this law frequently illus-
trated when standing passengers are
jostled off their feet by the sudden
starting or stopping of a car, or the
swinging of the car around a sharp curve.
Experiment 12. — Suspend a heavy ball by
a string not much too strong to hold it.
(Place a pad beneath it to catch it if it
drops.) Attach a similar string to the
bottom of the ball. (Figure 17.) Attempt
to lift the ball suddenly by the upper string.
What happens? Suspend the ball again and FIGURE 17
lift it very gradually by the upper string.
What happens? Now pull down suddenly on the lower string.
What happens? Suspend the ball again and pull down gradually
on the lower string. What happens?
PROPERTIES OF MATTER
45
When we tried suddenly to lift the suspended ball, the
light string snapped because it could not withstand the
sudden additional strain of overcoming the ball's inertia.
When we exerted a very gradual pull on the upper string,
AIRPLANES
we overcame the inertia of the ball slowly and without sudden
strain to the string.
When the lower string was suddenly pulled, it broke
because the ball, through its inertia, withstood the sudden
effort to change its position. But when the string attached
to the bottom of the ball was pulled gradually, the upper
string broke. In this case, the inertia of the ball was over-
come without sudden strain to the lower string, and so this
string had to withstand practically nothing but the pull of
the hand. The upper string, on the other hand, had to
46 PROPERTIES AND MAKE-UP OF MATTER
bear the double strain of the weight of the ball and the
steady pull of the hand.
'It is the inertia of the water which enables the small,
rapidly revolving propeller to move the big ship. The re-
sistance which the particles of air offer to being thrown
suddenly into motion, their inertia, enables the propeller
to pull the airplane along, and keeps the craft from falling
to the ground as long .as it is moving rapidly. It is owing
FIGURE 18
to inertia that the heavenly bodies keep on moving in space.
Once in motion they must keep on forever unless some force
stops them.
Experiment 13. — Place a glass globe partly filled with water and
a small amount of mercury on a rotating apparatus. (Figure 18.)
Rotate the globe rapidly. What do the water and mercury tend
to do?
In Experiments 11 and 13 it was seen that revolving
bodies tend to move away from the center around which
they are revolving. This is a manifestation of inertia
which is sometimes called centrifugal force. The weight
PROPERTIES OF MATTER 47
and the liquids tended to move away in a straight line, but
they were kept from it by the band and by the globe.
What happens when there is not sufficient restraining force
is seen when the mud flies from the tires of a rapidly moving
vehicle.
Newton many years ago discovered that all bodies of
matter have an attraction for one another. What causes
this no one knows, but the name given to this force of at-
traction is gravitation. Gravitation is always acting upon all
bodies, and their conduct is constantly affected by it. It
keeps the heavenly bodies from wandering away from one
another, as the rubber band kept the weight from flying
away from the hand.
Newton also discovered that the force of attraction be-
tween two bodies varies as the masses of the bodies; that
is, the more matter two bodies contain, the more they attract
each other. But this attraction becomes less as the dis-
tance between the bodies increases. The lessening of the
force of gravitation on account of the increase of distance
is proportional not to the distance but to the square of the
distance. This means that if the distance between two
bodies is doubled, the attraction between them is only one-
fourth as great. Moved three times as far apart, the bodies
have only one-ninth the attraction for each other; and so
on.
When this attraction is considered in relation to the earth
and bodies near its surface the term gravity is used. We are
constantly measuring the pull of gravity and calling it
weight. It is the force which causes us to lie down when we
wish to sleep comfortably, and which makes all unsupported
bodies fall to the earth.
If two forces act upon a body free to move, each will in-
48 PROPERTIES AND MAKE-UP OF MATTER
fluence the direction of its motion, and it will go in the
direction of neither force but in a direction between the two.
If there are more than two forces, the path of the object
acted upon will be the result of the action of all the forces.
In the case of the weight and the rubber band we found
that the moving weight when not held by the force of
the band flew away from the hand. The rubber band con-
tinually pulled in toward the hand, while owing to inertia
the weight tended to go off in a, straight line. The result
, , was that the weight
neither went in toward
the hand nor off in a
straight line, but in a
curved path.
Planetary Movements.
— We have seen that
the sun is the great
THREE FORCES IN PLAT
See the accompanying diagram.
FIGURE 19
center around which the earth and the other members of the
solar system revolve. The mass of the sun is so great that
the attraction of gravitation between it and the planets holds
these with their satellites in their paths and keeps them from
flying off into space. In fact the laws of inertia and gravita-
tion explain the entire mode of action of the heavenly bodies.
COMPOSITION OF MATTER 49
So thoroughly have mathematicians mastered these un-
varying laws that they can tell just where in their orbits
the earth or any of the planets will be at any future time,
or were at any past time. The exact date of any eclipse
in the future or in the past can be determined, and even the
path of the moon's shadow across the earth. Disputed
dates of events in ancient history which occurred during
eclipses of the moon have been determined to the exact
hour in this way.
One hundred years ago Uranus was thought to be the
farthest planet in the solar system. But years of patient
observation revealed the fact that its movement was not
in exact accord with the schedule astronomers had mapped
out for it. Two mathematicians, one in France and the
other in England, working separately without each other's
knowledge, concluded that this must be owing to the at-
traction of a more distant planet, as yet undiscovered. They
calculated what must be the exact position of this planet.
When on the night of September 23, 1846, a telescope was
directed to this point, a half hour's search revealed the
planet Neptune.
Composition of Matter. — It is the work of chemists to
find out of what matter is composed. They tell us that all
matter consists of minute particles, called molecules. These
molecules are constantly moving about in the spaces that
exist between them, hitting and bumping against one
another.
The fact that minute invisible particles may be given off by
a substance is readily shown by opening a bottle of ammonia
or exposing a piece of musk in a room. Soon in every part
of the room the presence of these substances may be recog-
50 PROPERTIES AND MAKE-UP OF MATTER
nized by the odor. Yet nothing can in any possible way be
seen to have been added to the air.
Experiment 14. — Dip a glass rod in strong hydrochloric acid
and hold it a few inches above the open mouth of a bottle of strong
ammonia water. Nothing can be seen to be emitted from either
the rod or the bottle, but when they are brought near together a
cloud of little white particles is formed. This must be due to the
action of an invisible something which came from the ammonia
upon an invisible something which came
from the hydrochloric acid, resulting in the
formation of something that is visible.
Molecules are too small to be seen
by the most powerful microscope.
There are millions of them in a par-
ticle of matter as big as the head of a
pin. Some one has said that if a drop
FIGURE 20 °f water could be magnified to the size
of the earth, the molecules would
probably appear no larger than a baseball.
It has been found possible by chemical and electrical
means to divide molecules into smaller particles called
atoms, and very recently to find out something about the
composition of the atoms themselves. For example, the
smallest particle in which water can exist and still be water
is a molecule. By means of an electric current these mole-
cules can be broken up. But when we thus divide the
molecules of water we no longer have water; we have two
gases, hydrogen and oxygen.
Experiment 15. — (Teacher's Experiment). — Procure from the
chemical laboratory an electrolysis apparatus or arrange an ap-
paratus as shown in Figure 21. This consists of a glass dish partly
filled with water to which a little sulphuric acid has been added.
(The sulphuric acid is needed only to aid in carrying the electricity
COMPOSITION OF MATTER
51
between the platinum foils.) Two copper wires each having a
small piece of platinum foil attached to one end are so arranged that
the platinum foils extend up vertically in the water.
Fill two test tubes with the water in the dish and invert them
over the platinum foils. To the ends of the copper wires attach
a battery consisting of several dry cells. Bubbles of gas will
begin to rise in the test tubes as soon as the battery is connected.
One of the tubes will fill twice as fast as the other. When this
tube is full quickly invert it and apply a lighted match to its mouth.
FIGURE 21
There will be a sharp explosion. This gas is hydrogen. Invert
the other tube and insert a splinter with a glowing spark at its
end. The spark will burst into flame. This gas is oxygen.
Chemists have learned that every molecule of water
contains two particles of hydrogen and one particle of oxy-
gen. These particles are called atoms. An atom of hydro-
gen is hydrogen ; an atom of oxygen is oxygen — no other
substance. For that reason, hydrogen and oxygen are
known as simple substances and are called elements. But
since the smallest particle of water — a molecule — is com-
posed of hydrogen and oxygen, water is not a simple sub-
stance but a compound of two other substances. Chemists
therefore call water a compound.
Every kind of matter known to man is classified as either
an element or a compound. So far there have been dis-
covered only about eighty elements — eighty substances that
cannot be reduced to simpler substances. Among these are
52 PROPERTIES AND MAKE-UP OF MATTER
iron, copper, tin, aluminum, lead, zinc, mercury, gold,
silver, nickel. The gases hydrogen, oxygen, and nitrogen
are also elements.
Most substances are compounds. The number of com-
pounds as compared with the number of elements in nature
may be illustrated in this rough way. There are only 26
letters in the English alphabet, but these may be combined
in so many different ways that we have thousands of English
words. Just so there are to our knowledge only about
eighty different elements in the world. But these elements
unite in so many different ways and in so many different
proportions that we have innumerable compounds.
But the comparison of letters and words with elements
and compounds must go no farther than to show how many
more compounds there are than elements. The eye can
pick out all the different letters that compose every word.
But when the atoms of different kinds of elements combine
into molecules, the resulting compound substance is so
different from the elements composing it that there is no
apparent relationship.
Water furnishes a good illustration. Oxygen is a gas
that must be present wherever there is burning. Hy-
drogen burns very readily in the presence of oxygen. But
water, every molecule of which is made up of atoms of these
two gases and is the result of the burning of hydrogen in
oxygen, is our main dependence for putting out fires.
Physical and Chemical Changes. Experiment 16. — Mix a
little powdered sulphur with about half as much powdered iron or
very fine iron filings. Examine the mixture with a magnifying glass.
You can easily distinguish between the particles of iron and sulphur.
Put the mixture into a test tube and heat it over a Bunsen burner.
(Figure 22.) The mixture will glow and become a solid mass.
PHYSICAL AND CHEMICAL CHANGES 53
Break the test tube and examine the solid with a magnifying glass.
Can you now distinguish the iron from the sulphur? The solid is a
chemical compound called iron sulphide. ,
When water freezes it does not become a different sub-
stance ; it is still water, but water in a solid state. When
water is " boiled away " or evaporated by the heat of the
sun, it is still water, but water in a gaseous state. When
the iron used in Experiment 16 was pulverized it still re-
mained iron. Such changes as these, which do not affect the
nature of a substance, are called physical
changes. . • ' , .
But when molecules break up into
their atoms, or atoms unite to form
molecules, a chemical change is said to
occur. Such is the change that occurs
when hydrogen and oxygen unite to
form water ; or when the electrical cur-
FIGURE 22
rent breaks up the molecules of water
into the two kinds of atoms composing them; or when
sufficient heat is applied to an iron and sulphur mixture.
One of the most common examples of chemical change
is the rusting of iron exposed to air. The atoms of oxygen
in the air and in the water of the air combine with the iron
to produce rust. A chemical change takes place and a
compound of the two elements is formed which is entirely
different in its nature from either.
A chemical compound such as iron rust, made up of oxygen
and some other element, is called an oxide.
Mixtures must be carefully distinguished from chemical
compounds. If we mix milk and water, neither the water
nor the milk is really changed in nature as the result of put-
ting them together in the same vessel. If we try to mix
54 PROPERTIES AND MAKE-UP OF MATTER
oil and water their failure to combine into a third substance
is even more noticeable. After a little while the water will
be found at the bottom of the vessel and the oil, which is
lighter, will float on top. A chemical compound is very
different from such mixtures, as we
learned in the case of water and of
iron sulphide.
Acids, Bases, and Salts. The
most important chemical compounds
for us to consider are acids, bases,
and salts. Acids of various kinds
exist in apples, grapes, rhubarb,
buttermilk, vinegar, lemons, oranges,
and other familiar substances.
A small amount of very dilute
RUSTING OF IRON hydrochloric acid is formed in the
stomach of man and of some other
animals and helps in the process of digestion. Hydrochloric
acid, sulphuric acid, and nitric acid are much used in the
laboratories and in various industries.
Many acids are liquid; and dilute solutions (little acid
in much water) of all common acids taste sour. Acids
turn blue litmus paper to red. Litmus paper is paper which
has been especially prepared by treating it with a vegetable
substance called litmus, obtained from a low order of plants
called lichens. Strong acids may cause great injury to
cloth, paper, wood, or the flesh of animals'.
It is important that we should become acquainted with
another class of compounds called bases that are in some
ways just the opposites of acids. Most bases are in the
form of solids; and dilute solutions of almost all the bases
ACIDS, BASES, AND SALTS
55
taste bitter. Litmus paper that has been turned red by
acids will be changed back to blue by a base. Some of the
most common bases of the household are ammonia water,
baking soda, limewater, caustic potash (lye), and caustic
soda. Certain strong bases are usually called alkalies.
Caustic potash and caustic soda are two of the commonest
and strongest alkalies.
Experiment 17. — Into a clean test tube containing pure water
put a small piece of blue litmus paper. Pour into the test tube a
little hydrochloric acid. What happens to the litmus paper?
Now add a solution of caustic soda, drop by drop, until the litmus
paper takes on a pale
bluish red shade. Taste
a drop of the solution in
the test tube. The test
tube will be found to
contain water with com-
mon salt dissolved in it.
By evaporating the
water, crystals of 'salt
may be obtained.
This process of com-
bining an acid and a ROCK SALT
base in right propor-
tions, by which a substance is produced that is neither
an acid nor a base, is called neutralization. The result of
such a chemical combination is water and a salt. There
are many different kinds of salts; but the salt with
which we are most familiar is sodium chloride, or
common table salt, which resulted from the preceding
experiment.
Strong acids and bases will corrode metals, discolor
clothing, or even " eat " holes in it, and cause ugly flesh
56 PROPERTIES AND MAKE-UP OF MATTER
wounds. But
neutral substances
will do none of
these things.
A strong base
like lye is just as
dangerous to
handle as a power-
ful acid. It is
well to bear in
mind then that
bases and acids
counteract or
neutralize the de-
structive effects
of each other. If
lye is spilled on
the hands or
clothing, vinegar
or lemon juice
should immedi-
ately be applied
to neutralize the
base. If acid is
spilled, ammonia
water is the safest
base to counter-
act it since it will
do the least harm
Courtesy of The Procter and Gamble Company if tOO much is USed .
KETTLE USED IN MANUFACTURE OF SOAP E verv housewif e
This kettle is 16 feet in diameter, three stories high,
and it holds about 375,000 pounds of soap. KUOWS that am-
ACIDS, BASES, AND SALTS 57
monia water may be used in a number of different ways to
help remove grease from various kinds of fabrics, and that
lye will act upon grease in such a way that water will dis-
solve it. Lye is therefore used for " cutting " the grease
in drain pipes leading from sinks. But since lye and other
strong bases which " cut " grease will also ruin most fabrics
and will do harm to the skin, a milder cleansing agent must
be found for laundry and personal use. Soap is one of
those substances which chemists call salts, and is made by
mixing or boiling fats with lye.
The neutralizing of acids by means of some mild base is
a part of the daily experience of many people, even though
they may not realize what the chemical action is. We put
ammonia or damp baking soda on a bee-sting to neutralize
the acid that the bee has injected into the flesh. Baking
soda is used by housewives to sweeten sour milk. Frugal
cooks sprinkle baking soda lightly over rhubarb, gooseberry,
or cherry pie in order partly to neutralize the acids and
thus to save sugar.
The farmer uses lime to " sweeten "a " sour " or acid
soil. Physicians often prescribe limewater or a solution of
baking soda to neutralize acidity (sourness) of the stomach.
Fruit stains are caused by fruit acids. For that reason,
the stains may usually be removed by soaking the linen in a
weak solution of ammonia or borax.
The wonderful progress that man has made in the last
century in manufacturing, transportation, agriculture, build-
ing, sanitation, and comfortable living conditions, has come
out of his greatly increased scientific knowledge, and out
of his increasing ability to control forms of energy which
produce desired chemical and physical changes.
58 PROPERTIES AND MAKE-UP OF MATTER
SUMMARY
Anything that occupies space is matter. Matter is known
to us in three forms — solids, liquids, and gases. Matter
has certain properties, such as extension, inertia, and gravi-
tation. The laws of inertia and gravitation explain so per-
fectly the movements of the heavenly bodies that their
courses may be accurately foretold.
All matter consists of particles called molecules, too small
to be seen with the most powerful microscope. Molecules
may be divided into smaller particles called atoms. If the
molecules of a substance may be broken up into two or more
kinds of atoms, the substance is called a compound ; if not,
it is called an element. There are about eighty elements
known to scientists. All other substances are compounds.
When molecules of a substance gain atoms, lose atoms, or
exchange atoms with molecules of other substances, a chem-
ical change is said to occur. Any other kind of change in
matter is a physical change. If when we combine two sub-
stances, the molecules remain unchanged, we have a mixture ;
if atoms of different kinds unite into molecules, we have a
chemical compound.
Acids, bases, and salts are most important chemical com-
pounds. Acids exist in many familiar substances. Many
acids are liquid. Dilute solutions of common acids taste
sour. Acids turn blue litmus paper red. Bases are in some
ways just the opposite of acids. Most bases are solid and
dilute solutions of them taste bitter. They turn red litmus
paper blue.
Strong acids and bases are injurious to flesh or to common
substances. The process of combining an acid and a base is
called neutralization, and the result is water and a salt. A
QUESTIONS 59
salt has none of the caustic or corroding properties of bases
and acids. Using some base to neutralize an acid is a com-
mon household experience. Strong bases like lye are used to
"cut" grease from wood or metal. For milder cleansing
purposes we use soap, which is neither an acid or a base,
but a salt.
QUESTIONS
In what three forms does matter exist?
Name and illustrate three universal properties of matter.
What daily experiences of yours are explained by these three
properties?
Why does a motorman slow up his car at a sharp curve?
What keeps the planets moving around the sun and in their
orbits?
Of what do chemists regard all substances to be composed?
Why?
What is the difference between a physical and a chemical change?
Give an example of each.
In what respects do acids, bases, and salts differ from one another ?
Illustrate.
For what purpose have you ever used an acid, a base, or a salt?
CHAPTER IV
THE SUN'S GIPT OF HEAT
The sun is not only the ruler of the solar system in that
it holds the planets in their orbits as they revolve about it ;
it also controls the activities upon the planets since it fur-
nishes them with their heat and light. Without the heat
of the sun the earth would be a cold, barren, lifeless, inert
ball of matter and nothing more. The sun's gift of heat is
all important.
Everybody has observed many of the effects of heat. It
melts ice. It converts water into steam. It cooks food.
Thus we see that heat has the ability to cause change. The
capacity for causing change, for overcoming resistance, for
doing work, is called energy. Heat is therefore a form of
energy.
A body may have through its position or its composition
the ability to do work without actually being at work. It
is then said to have potential energy. The moment a body
begins to do work, its energy is called kinetic energy. Either
kind of energy may be transformed into the other.
A brick on a chimney top has potential energy owing to
its position. If some force pushes it off, its potential energy
is transformed into kinetic energy. When you wind a
clock, the energy you expend is transmitted to the spring,
and the spring is wound into such a position that it possesses
potential energy. Thus your kinetic energy is stored up
60
POTENTIAL AND KINETIC ENERGY
61
in the spring as potential energy. Slowly the change of
position of the spring transforms its potential energy back
into kinetic energy.
When a gun is loaded with powder it has potential energy
due to the composi- __
tion of the powder.
When the powder is
exploded, the poten-
tial energy changes
into kinetic energy
which is imparted to
the bullet. The
smallest possible
amount of nitroglyc-
erine has potential
energy on account of
the arrangement of
the atoms in its mol-
ecules. When that
arrangement is dis-
turbed, potential
energy becomes ki-
netic and an explosion
results.
The sun through-
out its existence has
been sending vast
quantities of energy
to the earth. This
energy has been
mostly in the forms
of heat and light.
Courtesy of Illinois Central Railroad
A PILE DRIVER IN ACTION
The weight or "rain" is lifted to the top of
the machine, where it has great potential
energy. As it falls, it changes its potential
energy into kinetic energy and drives the
pile.
62 THE SUN'S GIFT OF HEAT
The ability of the earth to support plant or animal life or
to furnish man the power necessary to carry on his industries
is due to the energy furnished by the sun. Plants cannot
grow without the energy furnished by the sunlight, and
animals could not live were it not for the energy furnished^
them by the plants.
We often think that there are many different sources of
energy such as waterpower, wood, coal, oil, and others ; but
when these are traced back, their energy is found to have
come from one source, the sun. The water which the sun
has evaporated and carried by cloud and shower to the
mountain lake is stored there and has potential energy. It
is ready to run down the valleys changing its potential
energy into kinetic and doing work. Without the heat of
the sun there would be no life upon the earth, no flowing
streams, no changing winds, none of the restless energy
which makes the world as we know it.
For untold ages plants utilized the sun's energy and stored
it up. It was preserved in the remains of plants in the form
of coal. This coal is now being burned to furnish power to
carry on man's industries. Thus nature has run a savings
bank. The sun's kinetic energy was transformed and stored
for ages in the earth's vaults as potential energy, and now
issues from the burning coal as kinetic energy to do our
bidding.
The motion of the falling brick was a manifestation of
energy due to gravitation. The explosion of the gunpowder
was due to chemical energy. The ordinary 'street car runs
by virtue of electrical energy. Thus we see that there are
other forms of energy besides heat and light. But one form
of energy may be readily changed into another form, as
when the steam engine transforms the energy in coal into
CONSERVATION OF ENERGY
63
mechanical energy, or when this mechanical energy is changed
by the dynamo into electrical energy. (Figure 23.)
If you have ever bored a hole in hard wood, you have
noticed how hot the point of the drill becomes. A portion
of the energy you expended went to displace the particles
of wood, and a portion of your energy was transformed
by friction into heat. The portion of your energy which was
transformed into heat is usually referred to as lost energy,
because it did not help to accomplish the work you set out
FIGURE 23. — TRANSFORMATION OP ENERGY
to do. Whenever man undertakes to change one form of
energy into another, there is always this " loss of energy."
In a factory, for example, a great deal of the heat from
the burning fuel goes up the chimney and is also lost in
other ways. Even that part of the heat which is transformed
into mechanical energy cannot all be utilized. Much of it
is transformed back into heat by the friction of the moving
parts of the machinery.
In reality, however, no energy is ever lost or destroyed.
It may be lost in the sense that it does not serve man's
immediate purpose, but it has not gone out of existence.
The same thing may be said of energy that was said of
64
THE SUN'S GIFT OF HEAT
matter. Man can neither create it nor destroy it. He
may only transform it. This great truth has been deter-
mined by a vast amount of most careful investigation, and
is called the law of conservation of energy.
Some Effects of Heat. — The following experiments illus-
trate a common effect of heat.
Heat. — Experiment 18. — Fit a glass flask with a one-hole rubber
stopper through which passes a glass tube about 20 cm. long.
Place this on a ringstand so that the end of the
tube extends down into a bottle nearly filled with
water. (Figure 24.) Gently heat the flask. The
air expands and bubbles rise in the water. When
/ the flask cools, the air contracts and water rises in
the tube.
Experiment 19. — Fill the flask used in the last
experiment with colored water. See that the end
of the glass tube passing through the rubber
stopper is just even with the bottom of the stopper.
Smear the lower part of the stopper with vaseline
and insert it in the flask, being careful that the
flask and a few centimeters of the tube are filled
with the colored water and that there are no air
bubbles in the flask. Mark, by slipping over a
rubber band, the end of the water
column in the tube. (Figure 25.)
Heat the flask. The water expands.
Experiment 20. — Pass the ball
of a ball-and-ring apparatus through
the ring. (Figure 26.) Notice how
closely it fits. Heat the ball in a
Bunsen flame for several minutes.
See if the ball will now go through the ring.
FIGUBE 26 Explain why it does not.
We saw in these experiments that heat caused the gas,
the liquid, and the solid to expand. Cooling had the reverse
FIGURE 24
FIGURE 25
SOME EFFECTS OF HEAT 65
effect. On every hand expansion and contraction due to
changes in temperature must be taken into account. The
ends of steam pipes are allowed to be free and are never
attached firmly. The ends of the spans of long iron bridges
are placed on rollers. In places where there are considerable
ranges of temperature concrete sidewalks are cut into squares
instead of being laid as continuous solid surfaces. When
iron tires are fitted to wagon wheels they are first heated
and then placed on the wheels and allowed to cool. Tele-
phone wires are tighter in winter than
in summer. For this reason they are not
stretched taut when put up.
Experiment 21. — Heat a metal compound FIGURE 27
bar. It bends over on one side. The more
•the bar is heated the more it bends. (Figure 27.) The two
metals do not expand at the same rate.
Various solids and liquids expand and contract at different
rates. Platinum expands and contracts at almost the same
rate as glass. When platinum and glass are fused together
they expand and contract almost as one substance. For
this reason, in the manufacture of incandescent lamps, plati-
num is the only substance that can be used to pass through
glass to carry the electrical current to the filament within.
Other metals contract either more rapidly than the glass
and thus let air into the bulb, or more slowly and thus
break the glass. One reason why mercury is used in ther-
mometers is that it changes rapidly in volume with changes
in temperature.
Different parts of the same substance will expand at
different rates according to the amount of heat applied.
When experienced housewives wash glasses in hot water,
they do not dip them slowly ; they plunge them in quickly
66 THE SUN'S GIFT OF HEAT
so as to allow them to expand at the same rate throughout
and thus to prevent their breaking. This explains why it
is unwise to pour boiling water slowly into a cold glass, or
cold water slowly into a hot glass.
The experiment with the ball-and-ring apparatus easily
makes clear the meaning of the terms mass, volume, density,
and weight, which we shall have occasion to use from time
to time. After the iron ball was heated, it contained no
more iron than before it was heated. The amount of matter
in it, its mass, remained the same. But under heat the iron
expanded and occupied more space; that is, its volume
was greater. Heat increased the volume,
but not the mass, of each of the sub-
stances we experimented upon.
We all know that some substances are
heavier than others. A cubic inch of
CORK
LEAD
FIGURE 28. — EQUAL lead, for example, is heavier than a
MASSES OF CORK cubjc jnch Qf CQrk We that th
AND LEAD , . ,
lead has greater density than the cork ;
that is, a piece of lead has more matter in it than a piece of
cork of the same volume. (Figure 28.)
Weight is simply the measure of attraction between the
earth and the body weighed. The greater the amount
of matter, the greater is the attraction between it and the
earth; that is, the greater its weight. Weight, however,
must not be confused with density. The farther away a
substance is from the center of the earth, the less it weighs.
(Page 47.) A cubic inch of lead would weigh appreciably
less at the top of a high mountain than at the level of the
sea. But the density of the lead would not be affected by
its distance from the earth's center.
When the iron ball was heated, its volume was increased,
NATURE OF HEAT 67
its density was decreased, but its mass remained the same.
Since the mass remained the same as before heating, and its
distance from the earth's center was unchanged, it weighed
the same as before.
When heat was first studied it was thought to be an
invisible fluid without weight which worked itself into
bodies and caused them to expand in the same way that
water affects a sponge or a piece of wood. This fluid was
supposed to be driven out by pounding or rubbing. Even
the primitive savages knew that fire could be obtained by
rubbing two dry sticks together.
About the close of the eighteenth century an American,
Count Rumford, who was boring some cannon for the
Bavarian government, showed that the amount of heat
developed seemed to be entirely dependent upon the amount
of grinding or mechanical energy expended. The old theory
of a fluid prevailed, however, until about the middle of the
nineteenth century, when a great English experimenter
by the name of Joule showed conclusively that the amount
of heat developed was due entirely to the amount of energy
which apparently disappeared into the heated body.
We learned in Chapter III that all matter consists of
constantly moving particles, or molecules, with spaces be-
tween them. When a substance is heated the molecules
move more rapidly and strike each other harder. This
drives the molecules farther apart and causes the substance
to expand. Heat is a form of energy which manifests itself
in the motion of these molecules of matter. If a condition
could be reached where there was no molecular motion, there
would be no heat.
If we apply sufficient heat to ice, the molecules hit against
one another so rapidly and so hard that the ice loses its defi-
68 THE SUN'S GIFT OF HEAT
nite shape and melts down into water. If now we apply suffi-
cient heat to the water, the motion of the molecules becomes
so violent that they fly off from one another in steam. But
while this effect of heat in changing ice to water and water to
steam is familiar to us all, it is not so generally known that
the application of sufficient heat will change other substances
from a solid to a liquid and from a liquid to a gaseous state.
Iron, for instance, may be solid as we ordinarily see it,
or liquid as it comes from the blast furnace, or gas as it
exists in the indescribably hot atmosphere of the sun.
When heat is withdrawn, the processes are reversed, from
gas to liquid and then to solid.
Some substances, such as camphor, pass from a solid state
directly to a gaseous state. Even ice may do this under
certain conditions. Housewives in cold climates know,
for example, that clothes on the line will " freeze dry "
in zero weather.
Substances usually expand as they change from the solid
state to the liquid state, and contract when the process is
reversed. Ice is a notable exception to this general rule,
since when water freezes its volume increases. If it were
not for this, ice would not float. Certain metals such as
cast iron also have the property of expanding at the moment
of solidifying. Type metal is a mixture of metals that
possesses this property. It is poured into the molds in
a molten condition. When it solidifies it expands and
forces itself into every available crevice, thus taking on
the sharp outlines that type must have.
Substances always increase in volume as they change
from a liquid to a gaseous state. Engineers roughly esti-
mate, for example, that a cubic inch of water makes a
cubic foot of steam.
PRODUCTION OF HEAT
69
Courtesy of American Steel Foundries
:•:.! MOLTEN STEEL FLOWING FROM A BLAST FURNACE
The liquid steel is here conducted by a duplex spout into two 20-ton
ladles, ready for casting in the molds.
Production of Heat. — Heat may be produced in several
different ways, but the most common way is by burning.
Our houses are usually heated by burning wood or coal.
If we wish the fire in the stove to burn more brightly we
open the draft ; if more slowly, we close it. Apparently
70
THE SUN'S GIFT OF HEAT
the supply of air has much to do with the fierceness of
the fire.
Experiment 22. — Wind a short piece of wire around a small
piece of candle and after lighting the candle lower it into a wide-
mouthed bottle. Insert a stopper into the
mouth of the .bottle. The candle will begin
to smoke and will soon go out.
From the foregoing experiment it
appears that a supply of air is necessary
for the burning of the candle. Experi-
ence shows that this is true in all the
forms of combustion familiar to us.
Experiment 23. — (Teacher's Experiment.)
— Obtain four bottles of oxygen from the
chemical laboratory. If not obtainable, place
a piece of sodium peroxide (oxone) about as
large as the end of a finger in a side-necked
test tube provided with a medicine dropper
filled with water, as shown in Figure 29. Put
the end of the delivery tube under the mouth
of an inverted bottle filled with water arranged
on the shelf of a pneumatic trough. Drop
FIGURE 29 water slowly on to the sodium peroxide and
collect the gas generated. Fill several bottles.
Oxygen can also be prepared by heating a mixture of about one
part manganese dioxide and two parts potassium chlorate in a
test tube and collecting the gas over water. (Figure 30.) Does
the appearance of this
gas differ in any way
from air? Smell of it.
Has it any odor? Into
one .of the bottles of
oxygen insert a splinter
of wood having a spark -^
at the end. It bursts FIGURE 30
COMBUSTION 71
into flame. Does the same thing take place when the stick with
the spark upon it is held in a bottle of air?
Hold a lighted match at the mouth of another of the bottles
containing oxygen. Does the gas itself burn as illuminating gas
does when a match is applied to it ? If the oxygen in the air were
increased or decreased, it would have a great effect upon combus-
tion. Attach a piece of sulphur to a short piece of picture wire.
Ignite it and place the wire in a bottle of oxygen.
(Figure 31.) Does the sulphur burn strongly?
How about the wire ? Does it burn too ? fr ' v
In the experiment just performed, we found
that substances burn in oxygen much more
fiercely than in air, and that substances FIGURE 31
which do not burn in air readily burn in
oxygen. Experiments have shown that oxygen, a gas which
is in the air about us, must be present where burning
occurs. In fact burning is the result of the chemical union
of atoms of oxygen with atoms of other substances.
The paraffin in the candle is a compound that contains
both hydrogen and carbon. These two elements are found
in all common fuels and are sometimes called fuel elements.
Both of them readily unite under proper conditions with
oxygen, and the chemical action produces heat. When
wood or coal burns, the atoms of the fuel elements in these
substances unite with atoms of oxygen.
Experiment 24. — (Teacher's Experiment.) — Put a few zinc
scraps in a test tube and pour a little hydrochloric acid upon them.
Feel the test tube near the zinc.
Put half an inch of water into another test tube and carefully
pour a little strong sulphuric acid down the sides of the tube into
the water. Feel the tube.
Burning is not the only way in which chemical action
produces heat. In the preceding experiments, both test
72
THE SUN'S GIFT OF HEAT
tubes were found to have been heated by the chemical ac-
tion which took place, but no combustion occurred.
But chemical action is only one of the sources of heat.
Every Boy Scout is taught to make a fire by rubbing two
pieces of dry wood together.
(Figure 32.) He knows that
friction is a method of produc-
ing heat; or to state it another
way, the mechanical energy of
rubbing is transformed into heat
ment 157 that electrical energy
can be changed into heat energy. The change of chemical,
mechanical, and electrical energy into heat energy are the
three ways in which we produce heat.
Kindling Temperature. — We have found by experience
that a certain amount of heat is necessary to get things to
burn. Two sticks have to be rubbed until they are very
hot before they take fire. We use kindling to get large
pieces of wood and coal hot enough to burn. Everything
has to be brought to a certain temperature before it will
take fire. This temperature is called the kindling tempera-
lure.
The kindling temperatures of different substances vary
greatly. The kindling temperature of phosphorus is a
little below the temperature of the human body, and phos-
phorus is therefore a dangerous thing to handle. The
kindling temperature of iron is many hundreds of degrees.
Certain substances very readily unite with the oxygen of
the air at ordinary temperatures and, by so doing, of course
produce -heat. If the heat thus produced does not escape,
KINDLING TEMPERATURE
73
the substances will in time be raised to their kindling tem-
perature and will take fire. This is called spontaneous com-
bustion.
Linseed oil used by painters is a substance which readily
oxidizes. Accumulations of rags saturated with such oil
will gather heat of oxidation (if in a place where there is
no great movement of air) until the kindling temperature
is reached, and a fire is started. Sometimes the dust in
the center of a great pile of coal produces heat enough by
its oxidation to
start a fire in the
coal. Some-
times the heat
produced by the
" souring " of
hay is sufficient
to set the hay
on fire.
A means by
which substances
can be readily
brought to their kindling temperature is very essential if
fires are to be easily built. Our forefathers used to strike
a flint and steel together so as to make a spark fall upon
some fine, dry material (tinder). With this they patiently
started the larger fires they needed.
In frontier days, smoldering tinder was kept in a tinder
box," and this served the pioneers instead of matches.
Until less than a hundred years ago the use of flint and steel
was the prevailing method of obtaining fire.
This method of starting fire was difficult and uncertain.
The invention of the friction match has changed all this and
TINDER Box AND FLINT AND STEEL
74 THE SUN'S GIFT OF HEAT
made the production of fire easy and certain. It has been
one of the great factors in making life comfortable. The
earlier matches consisted of a splinter of wood tipped with
a mixture of sulphur, yellow phosphorus, potassium chlorate
or red lead, held together by glue. When struck on a rough
surface the heat of friction was sufficient to ignite the phos-
phorus, thus causing the other materials to burn and the
splinter of wood to catch fire.
It was soon found that the use of ordinary phosphorus
was very dangerous to the matchmakers, causing a dread-
ful bone disease. For that reason, the use of ordinary
phosphorus in the making of matches has now been prac-
tically abolished, and a harmless compound containing
phosphorus is usually substituted in its place. But since
friction against any rough surface will ignite the ordinary
match, nibbling mice and busy-fingered children have
often started disastrous fires with them. Because of that
the safety match was invented, which will not ignite by
friction on any ordinary rough surface.
On the tip of the safety match there is no phosphorus nor
phosphorus compound, but only substances that burn
readily and contain a great deal of oxygen. The side of the
.match box is used for a striking surface. It is coated with
several substances, among which is red phosphorus. The
only way red phosphorus can easily be ignited by friction is
to rub it with some substance that is rich in oxygen. The
oxygen-bearing materials on the tip of the safety match
strike a spark out of the red phosphorus, which in turn
ignites the match head.
Saving Fuel. — Experiment 26. — (a) After closing the holes at
the bottom of a Bunsen burner, turn on the gas and light it. The
flame is smoky. Heat a piece of wire in it. It heats slowly.
SAVING FUEL 75
Open the holes. The flame ceases to smoke. Place a wire in it.
It heats quickly. Regulate the sizes of the openings until the
greatest possible heat is obtained.
(6) By means of a ringstand hold a wire gauze two or three
inches above a Bunsen burner. Turn on the gas and apply a
lighted match above the gauze. The gas above the gauze will
take fire, but that below will not. (Figure 33.) Turn off the gas and
then turn it on again. Now light the gas below the gauze. The
gas above the gauze does not ignite. The gauze conducted the heat
off so rapidly into the surrounding air that the gas
on the side of the gauze away from the flame was
not raised to its kindling temperature and so did
not burn.
In Experiment 25 it was found that if the
holes at the bottom of a Bunsen burner are
closed so that an abundant supply of air
(that is, of oxygen in the air) is not mixed FIGURE 33
with the gas, the burner smokes. When
these holes are regulated so that the right amount of air is
supplied, there is a hot flame and no smoke. It was found
in the second part of the experiment that gas would not
burn unless it was raised to its kindling temperature. This
illustrates what happens, to a greater or less extent, in all
stoves and furnaces — especially where soft coal is burned.
Every one knows that when a fresh supply of soft coal is
thrown upon a fire, it smokes. This is because the fresh
coal acts as a blanket. It decreases the supply of fresh
air from below, and lowers the temperature in the upper
part of the stove or furnace. Not all the gases from the
coal that are driven off by the heat below are burned where
they are formed, because the blanket of coal has cut down'
the draft and thus lowered the supply of oxygen.
These light gases rise, therefore, into the upper part of
76 THE SUN'S GIFT OF HEAT
the stove or furnace, where the supply of oxygen is even more
scant and the temperature is below the kindling point of the
gases. The result of this incomplete .combustion is that
part of the carbon in the gases is set free and floats away in
the form of smoke.
This not only results in the formation of the smoke nuisance
in cities but also in a great loss of available heat. It is
estimated that in Pittsburgh alone the loss of heat due to
Courtesy of Underfeed Stoker Company of America
BEFORE INSTALLING AN UNDERFEED FURNACE
When a blanket of fresh fuel is thrown on the glowing coals, great quan-
tities of carbon and fuel gases escape as smoke. This may be likened
to burning a candle upside down.
non-combustion of smoke has been fully $10,000,000 in
a single year. This is aside from the tremendous total
damage to clothing, house furnishings, and stocks of mer-
chandise, and from its menace to health.
In order to burn the gases that rise to the upper part of
the stove or furnace, there must be a supply of fresh air
above the burning coal. When a furnace has too heavy a
draft from below, and no supply of fresh air through the
feed door, unburned fuel gases are driven up the chimney.
ABATING THE SMOKE NUISANCE 77
With proper arrangements for putting the coal upon the
fire in small quantities so as not to cut off the draft suddenly
or lower the temperature of the upper part of the stove too
greatly, a great saving of heat can be realized and one of
the worst nuisances of a modern city largely avoided.
Many cities require the use of smoke-consuming furnaces
in all large buildings. Most of these are so arranged that
the gases formed where the fresh supply of coal meets the
Courtesy of Stoter Underfeed Company of America
AFTER INSTALLING AN UNDERFEED FURNACE
In this furnace the fire is constantly above the fresh fuel, and the volatile
gases and carbon are consumed as they pass up through the fire.
This acts like a burning candle right side up.
glowing coals are conducted through the fire and largely
consumed. Contrivances known as smoke consumers are
sometimes attached to small furnaces. Abating the smoke
nuisance is a problem that deserves the most careful con-
sideration by the authorities of all cities. It involves the
conservation of both health and wealth.
Control of Fire. — Fire under control is man's best friend.
Fire makes our homes comfortable in winter, cooks our
food, lights many of our houses, is used somewhere in the
78 THE SUN'S GIFT OF HEAT
manufacturing of practically everything we use, fur-
nishes power for most of our transportation, and in fact
makes life livable. But when fire gets out of control it
ruthlessly destroys almost everything it can touch. The
control of fire is, therefore, exceedingly important. We
have seen (page 70) that fire cannot exist unless oxygen is
FIRE OUT OF CONTROL
Fighting the great conflagration at the Chicago stockyards in 1910.
present. Therefore to control fire it is only necessary to
shut off the oxygen. Closing the draft of a stove cuts down
the supply of oxygen.
When water is put on a fire it not only shuts off the supply
of oxygen but it also cools the burning material below its
kindling temperature. Water, however, is not serviceable
for extinguishing such substances as burning oils, since the
CONTROL OF FIRE
79
burning oil floats on the water and the expansion of any
generated steam throws the flaming oil about and thus
spreads the fire. In a case of this kind, sand or a woolen
blanket serves the purpose better.
Wool does not readily burn, and when the blanket is
thrown over the burning oil, the air is shut off and the
fire put out. If one's clothing takes fire by accident, one
should never run. A rug or a blanket rolled about the
body is the most effective means of putting
out the fire. If one is outdoors, rolling in
the dust, or heaping dust on the flames,
will cut off the oxygen supply. The chief
thing to remember is to cut off the air
supply immediately.
Experiment 26. — (Teacher's Experiment.) —
Get two or three bottles of carbon dioxide from
the chemical laboratory, or prepare it by pouring
dilute hydrochloric acid upon pieces of limestone
in a bottle and collecting the gas over water.
Does the appearance of this gas differ in any
way from that of air? Smell of one of the
bottles that has stood over water for some time. FIQURE 34. — DIA-
rrn T ™ T T , i GRAM OF A FlRE
The gas has no odor. Plunge a lighted match EXTINGUISHER
into one of the bottles containing the carbon
dioxide. What happens? Does the gas burn or support combus-
tion? Slowly overturn a bottle of the gas above a lighted candle.
The candle is extinguished. The gas falls out when the bottle
is overturned, thus showing that it is heavier than air. If the
amount of carbon dioxide in the air were largely increased, what
effect would it have upon combustion ?
The ordinary chemical fire extinguisher (Figure 34) con-
sists of a strong metal cylinder nearly filled with a solution
of baking soda. Held firmly in the top of the cylinder is a
80 THE SUN'S GIFT OF HEAT
bottle of sulphuric acid. There is an opening in the top of
the cylinder which is connected with the nozzle by means
of a short strong rubber tube. When the extinguisher is
to be operated, it must first be inverted. The acid falls out
of the bottle, and mingling with the solution of baking soda
rapidly generates carbon dioxide. The pressure of this
generating gas forces the solution mixed with the gas out
of the nozzle. Since carbon dioxide will not burn and is
considerably heavier than air, it helps the water to smother
the fire. Chemical fire-engines make use of this same gas.
Measurement of Temperature. — It has been seen (pages
64 and 65) that gases, liquids, and solids expand when
heated and contract when cooled. It has been
found that most substances expand uniformly
through ordinary ranges of temperature, so that
if this expansion or contraction is measured, we
are able to determine the change of temperature.
Experiment 27. — Slightly warm the bulb of an air
FIGURE 35 thermometer tube and place the open end in a beaker
half filled with inky water. (Figure 35.) Allow the
bulb to cool. The tube will become partly filled with the water.
When the bulb has become cooled to the temperature of its
surroundings, mark the end of the water column with a rubber
band. Grasp the bulb with the hand, thus warming the air in it.
The water column will run partially out of the tube back into the
beaker. Cool the bulb with a piece of ice or a damp cloth. The
water will come farther up in the tube than it did when simply
exposed to the air. We have here an apparatus for telling the
relative temperatures of bodies.
Instruments arranged to show changes in temperature
by the amount of the expansion or contraction of certain
materials, are called thermometers. These may be gas,
MEASUREMENT OF TEMPERATURE 81
liquid, or metal thermometers. There must be some
uniform temperatures between which the expansion shall
be measured if we are to have a basis of comparison. These
definite points have been taken as the freezing and boiling
points of water at sea level.
Experiment 28. — (Teacher's Experiment.) — Fill a four-inch
ignition tube with mercury and insert a one-hole rubber stopper
having a straight glass tube extending through it and about 20
cm, above it. (Figure 36.) It may be necessary
to cover the stopper with vaseline to keep out
air bubbles. When the stopper was inserted the
mercury should have risen a few centimeters in
the tube. Mark with a rubber band the end of
the mercury column. Gently warm the ignition
tube. The mercury column rises. Gool the
tube and the column falls. We have here a
crude thermometer.
The substance whose expansion is most
commonly used to measure the degree of
temperature is mercury. This expands
noticeably for an increase in temperature FIGURE 36
and the amount of its expansion can be very
readily determined. The ordinary thermometer consists of
a glass tube of uniform bore which has a bulb at one end.
The bulb and part of the tube are filled with mercury. The
remaining part of the tube is empty, so that the mercury
can freely rise or fall. When the temperature rises, the
mercury expands and rises, when the temperature falls, the
mercury contracts and sinks.
There are two kinds of thermometer scales commonly
used. The one which is used almost exclusively in scientific
work and in those countries where the metric system of
weights and measures has been adopted, is called the Cen-
82
THE SUN'S GIFT OF HEAT
tigrade. In this scale the point to which the mercury
column sinks when submerged in melting ice is marked 0°,
and the point to which it rises at sea level when immersed
in unconfined steam (the boiling point of water) is 100°. A
degree Centigrade, then, is -^^ the distance the column
expands when heated from freezing to boiling.
The common household thermometer
of this country and England is the
Fahrenheit thermometer. It is named
after its inventor, who about two hun-
dred years ago began the making of
thermometers. He found that by mix-
ing ice and water and salt he obtained
a temperature much lower than that of
freezing water. This temperature he
took as his zero point. In this scale the
point at which ice and snow melt is
marked 32°, and the point at which
water boils at sea level is marked 212°.
The distance between the boiling point
and freezing points is divided into 180
equal parts, or degrees. A degree
o- r, Fahrenheit, then, is -rJ-o- the distance the
JbiGURE o7. L/ENTI-
QRADE AND FAH- column expands when heated from freez-
RENHEIT SCALES . i «v • i p i xi
COMPARED ing to boiling, instead of Tiro as in the
Centigrade scale. (Figure 37.)
There are a number of different designs of thermometers.
Some are for measuring very high, others for measuring very
low, temperatures. Thermometers are also constructed so
as to be self-recording. (Figure 38.)
The Measurement of Heat. — Experiment 29. — In each of
two beakers or tin cups weigh out 100 g. of water. Carefully heat
THE MEASUREMENT OF HEAT
83
one of the beakers until the water when thoroughly stirred shows
a temperature of 90° C. Cool the other beaker till the tempera-
ture of the water is 10° C. Pour the water from one beaker into
the other, and after thoroughly stirring note the resulting tempera-
ture. Use a chemical thermometer to determine the temperatures.
Weigh out 100 g. of fine No. 10 shot in a tin cup and 100 g. of
water in another. Place the cup containing the shot in boiling
water and allow it to re-
main, stirring the shot occa-
sionally, until its tempera-
ture is 90° C. Cool the
water in the other beaker
until its temperature is
10° C. Determine the tem-
peratures exactly and then
pour the shot into the
water. After thoroughly
stirring determine the tem-
perature of the mixture.
Which has the highest
temperature, the mixture of water and water or the mixture of shot
and water?
Since heat plays such an important part in the activities
of the earth, we need to know how to measure it. There
is a great difference between temperature and the amount
of heat. The amount of heat in a spoonful of water at
100° would be very much less than in a pailful of water
at 10°. It would require more heat to raise a pond of
water a small part of a degree than to raise a kettleful
many degrees. That is why large bodies of water, although
their temperatures never greatly change, are able to absorb
and to give out great amounts of heat.
Not only does the amount of heat necessary to raise the
temperature of different quantities of the same substance
vary, but the amount of heat necessary to raise the tem-
FIQURE 38. — A SELF-RECORDING
THERMOMETER
84 THE SUN'S GIFT OF HEAT
perature of equal quantities of different substances also
varies. If a pound of water and a pound of olive oil are
placed side by side in similar dishes on a stove, it will be
found that the olive oil increases in temperature about
twice as fast as the water, i.e. it takes about twice as much
heat to raise water as it does to raise the same weight of
olive oil one degree. In fact, it takes more heat to raise
a given weight of water one degree than it does to raise
the same weight of almost any other known substance.
In Experiment 29, the resulting temperature from the
water mixture was much higher than from the water and
shot mixture. The shot has much less capacity for heat.
The quantity of heat required to raise the temperature of a
certain mass of a substance one degree compared to the
quantity of heat required to raise the same mass of water
one degree is called the specific heat of that substance.
The specific heat of olive oil is .47, of shot .03. That is,
it takes .47 as much heat to raise a given mass of olive oil
and .03 as much heat to raise a given mass of shot one
degree as it does to raise a corresponding mass of water
one degree. In order to compare different quantities of heat,
physicists have taken as the unit of measure the quantity
of heat required to raise the temperature of one gram of
water through one degree C. This unit is called a calorie.
The Effect of Heat upon the Condition of a Substance. —
Experiment 30. — Having filled two tin cups or beakers of the same
size to an equal height, one with water and the other with a mix-
ture of water and ice, place them side by side on a stove or over
Bunsen burners so adjusted as to give approximately the same
amount of heat. (Figure 39.) Stir each with a chemical thermom-
eter, and make a note of its temperature.
After heating a few minutes, stir again and note the tempera-
ture. Have there been like changes in the temperatures of the
LATENT HEAT
85
two cups? Continue to stir and note the changes until the ice is
melted. Do your notes show that like amounts of heat have pro-
duced like changes of temperature in the two cups? Continue to
heat, stirring and noting the temperatures occasionally. Is there
now an approximately equal rise of the temperatures of the water
in the cups?
When the water in one cup begins to boil, does its temperature
continue to rise as fast as that of the water in the other cup? What
apparently became of the
heat delivered to the ice-
water before the ice melted ?
What apparently became
of the heat delivered -to
the water while it is boil-
ing?
The preceding experi- A
ment shows that heat is
absorbed in melting ice,
and that the heat so
absorbed does not raise
the temperature of the
ice. It also shows that heat changes water into steam, and
that although very much heat was applied none of it was
used in raising the temperature of the boiling water but all
of it in changing the condition of the water.
Carefully performed experiments show that it takes 80
times as much heat to change a gram of ice at 0° C. into
water at 0° C. ; and about 536 times as much to change
a gram of water at 100° C. into steam at 100° C. as it does to
raise the temperature of the same mass of water one degree
C. The heat absorbed in changes of this kind is called
latent heat. It is all given out again when the water freezes
or the steam condenses.
This explains why ice melting in a refrigerator takes so
FIGURE 39
86
THE SUN'S GIFT OF HEAT
much heat from the air and food about it and keeps them
cool. It also explains why so much heat is given out when
the steam in a steam radiator condenses into water, and
why steam heating is the most effective way of heating
houses in cold climates.
Many of us have noticed that when we have a quiet
snowfall the temperature usually rises. This is because the
heat given out by the changing of the vapor in the air into
^^___^_ snow is not carried by the air currents
to another region but warms the local
atmosphere. Many similar phenomena
are explained by this experiment.
FIGURE 40. — COMPAR-
ATIVE EFFECTS OF
HEAT
The amount of heat re-
quired to change the
smaller mass of water
into steam without
altering its tempera-
ture would raise the
temperature of the
larger volume one
degree.
The Transference of Heat. — Some
one has stated a truth playfully in
saying that " no substance is ever
selfish with the heat it possesses."
Any hot object left for a long enough
time in cooler surroundings will yield
up its heat until it is of the same tem-
perature as its surroundings. Any cold
object placed in warm surroundings
will receive heat until it is eventually
of the same temperature as its surroundings.
If water is placed on a hot stove it will absorb heat until
it passes away in steam. If hot water is allowed to stand
in a room, it will give off its heat until its temperature falls
to that of the room. When ice is placed in a refrigerator
the heat of the contents of the refrigerator is yielded up to
the ice and melts it. If a refrigerator could be so con-
structed that no warmth could reach its interior, the contents
would eventually become as cold as the ice.
THE TRANSFERENCE OF HEAT 87
Experiment 31. — Cut off 15 cm. of No. 10 copper and No. 10
iron wire and the same length of glass rod of about the same di-
ameter. Holding each of these by one end place the opposite end
in the flame of a Bunsen burner. Which of the three conducts the
heat to the hand first ?
Experiment 32. — Fill a test tube about f full of cold water. Hold-
ing the tube by the bottom carefully heat the top part of the water
until it boils. Be sure that the flame does not strike
the tube above the water, else the tube will break.
(Figure 41.) A little piece of ice in the bottom of
the test tube makes the action more apparent. A
bit of wire gauze or a wire stuffed into the test tube
will prevent the ice from coming to the surface.
Water conducts heat poorly. The hot water does
not sink. Do you conclude that the warm water is heavier or
lighter than the colder water ?
Through solid substances, such as metals, heat travels
quite readily ; through others, such as glass, less rapidly.
In Experiment 31, we found that heat traveled along some
rods faster than it did along others. In no case, however,
was there any indication that there was a transference of the
particles composing the rods. In the boiling of the water
at the top of the test tube, there was no indication that
the water particles moved to the bottom of the tube. In
these cases, the heat is simply transferred from molecule
to molecule.
This kind of heat transference is called conduction. In
transference by conduction each molecule acts as a mes-
senger, passing the heat energy on to another that it touches.
If two different substances touch each other, the molecules
of one substance may conduct heat to the molecules of the
other ; but the two substances must be touching each .other
or the method of transference cannot be called conduction.
Conductors may be good or bad, as was shown by the
88 THE SUN'S GIFT OF HEAT
different materials used in the experiments. One of the
reasons why we use iron for our radiators is that the heat
of the steam may readily pass from the inside to the out-
side of the radiator. , We cover our steam pipes with as-
bestos when we wish to retain the heat, because asbestos
is a poor conductor and will keep the heat in the pipes.
On a cold day good conductors of heat feel colder than
other objects because they quickly conduct the heat away
from the hand. For that reason, a metal door knob seems
much colder than the door in winter. On a very warm day
good conductors feel hotter than other objects because they
conduct their heat to the hand rapidly. The metal knob,
therefore, seems much warmer than the door when the bright
sun is shining on them both in summer.
This explains why tile and concrete floors feel cold, and
why we cover them with rugs, which are poor conductors
of heat. A woolen blanket feels warm, and a cotton sheet
cold, for the same reason. There is really no difference
between the warmth of these objects if they
are in surroundings of the same temperature.
Experiment 33. — Hold a piece of burning paper
under a bell jar held mouth downward. (Figure
42.) Notice the air currents as indicated by the
smoke. Paper soaked in a moderately strong
solution of saltpeter and dried burns with a very
FIGURE 42 smoky flame.
Experiment 34. — Fill a 500 cc. round-bottomed
flask half full of water and place on a ringstand above a Bunsen
burner, (figure 43.) Stir in a little sawdust. Some of it should
fall to the bottom of the flask. Gently heat the bottom of the
flask. Notice the currents.
When the burning paper was held under the bell glass, and
when the water was heated at the bottom of the flask, cur-
THE TRANSFERENCE OF HEAT
89
FIGURE 43
rents were seen to be developed. The heated and expanded
air and water rose. Here again the heat was transferred
by conduction, but it was helped by the
upward movement of the heated water
and air. These upward movements of
the water and the air are known as con-
vection currents. The efficiency of the hot
water and hot air furnaces which heat our
houses is
due to the
convection
currents.
We shall
find later
that if it were not for con-
vection currents there would
be no winds nor ocean cur-
rents.
Whether we heat a test
tube of water from above or
from below, the heat is car-
ried by conduction from one
molecule to another. But
when we heat it from below,
the process is hastened by
convection currents.
If an incandescent lamp
(Figure 45) is turned on and
the hand held a little dis-
tance from the glass bulb,
the hand will be warmed,
although the glass bulb itself
FIGUEE 44. — HOT WATER
FURNACE
As the water in the boiler begins to
heat, convection currents are set
up. Cold water, which is heavier,
flows from the radiators down into
the boiler and forces warmer water
up into the radiators. As long as
fire is maintained in the furnace,
there is constant circulation. Since
water expands under heat, an over-
flow tank must be provided to
prevent explosion of the pipes or
boiler.
90
THE SUN'S GIFT OF HEAT
(a poor conductor of heat) remains cool for a time. When
the lamp was made, air was taken from the bulb, and so
the white-hot filament is surrounded by almost empty space
(vacuum). The heat, therefore, cannot travel to the hand
by convection currents, because there is no air nor other
substance in contact with the filament. The hand is not
warmed by convection currents from the glass, because the
bulb is still cool. The sensation of heat can-
not be due to conduction, because the air which
surrounds the bulb is not in contact with the
hot filament. Besides, air is an even poorer
conductor of heat than glass, and the glass
itself does not become hot for some little time.
There must, therefore, be another mode of
transferring heat besides conduction and con-
vection. It also appears that in this method
of transferring no material substance is neces-
sary. This is shown by the fact that the hot
filament is surrounded by an almost perfect
vacuum. Astronomers tell us that there is
no material medium between our atmosphere
and the sun.
The heat of the sun travels to us with the tremendous
speed of light, 186,000 miles a second, but does not warm
the intervening space because there is no matter in it to
be warmed. Radiation is the name given to this method of
heat transference. If heat did not travel in this way, the
earth would be uninhabitable. The conduction process is
very slow when compared with radiation.
FIGURE 45
Conserving Heat. — Heat is so essential to life and
happiness that it is often necessary to provide means for
CONSERVING HEAT
91
Jrc
preventing its escape. We build thick walls to our houses
in order that the heat from our stoves and furnaces may not
escape. We put on clothing in order that the heat of the
body may be retained. Ovens of cookstoves are surrounded
by air spaces and non-conducting materials so that the heat
will not be lost. In fact there are scores of arrangements
in every home for conserving heat.
Dark surfaces absorb heat more readily than light surfaces,
and thus increase more rapidly in temperature. Light
surfaces reflect heat, and absorb
it very slowly. This is why we
wear dark clothing in winter
and light-colored clothing in
summer. Dark surfaces not
only absorb heat more readily
but they radiate it more rapidly.
Light surfaces are slow to heat
up, and when they are heated
up they are just as slow to
radiate their heat. There is
the same difference in these
respects between smooth surfaces and rough surfaces as
between light and dark surfaces.
The fireless cooker (Figure 46) is a device to save heat in
cooking. It consists of two boxes, one within the other and
separated from each other on all sides by a space of several
inches. This space is filled with sawdust, ground cork, as-
bestos, or any other substance that is a poor conductor of
heat. A tightly fitting cover is provided, containing similar
non-conducting material. The food to be cooked is heated
on the stove in a covered vessel, and this is placed within
the cooker. Since the heat can escape only very slowly, the
REVOLVING DOORS
An arrangement to conserve heat.
92
THE SUN'S GIFT OF HEAT
FIGURE 46. — DIAGRAM OF A
FIRELESS COOKER
food remains at nearly the boiling point for hours, and is
thus cooked. In most cookers, heated pieces of soap-
J . __ stone are placed above and
below the dish containing the
food. Soapstone has a large
capacity for heat. (Page 84.)
The fireless cooker can also
be used as a refrigerator if
the food is cooled before being
placed in it or if ice is placed
in it with the food. When
the cooker is used as a refrigerator, the insulated walls are
very slow to conduct the heat of the atmosphere to the
cold food, just as they were slow to con-
duct the inside heat to the cooler sur-
rounding atmosphere. The non-conducting
character of the walls protects either way.
For that reason the walls of a fireless
cooker are similar to those of a refrigerator.
Snow on the ground in winter prevents
the heat from leaving the ground and the
ground from being deeply frozen, just as
the sawdust and other materials in the
walls of the cooker prevent the heat from
being conducted rapidly away from the
cooker. That is one reason why farmers
like a snowy winter.
The thermos bottle (Figure 47) is similar
to the fireless cooker in principle. It
consists of two glass bottles, one placed
inside the other, sealed together at the neck. Before the
bottles are sealed together the air between them is re-
FIGURE 47. — DIA-
GRAM OF A THER-
MOS BOTTLE
SUMMARY 93
moved. Heat, therefore, cannot pass from the inner bottle
by conduction or convection. To retard the passage of
radiant heat, the inner walls of the vacuum space are finished
with bright reflecting surfaces.
Note to Students. — Both the Centigrade and the Fahrenheit
scale are used in later discussions in this book. The student has
been accustomed to the English or Fahrenheit scale in everyday
life, and so occasionally the use of this scale prevents unnecessary
confusion. On the other hand, the Centigrade scale is preferred in
scientific work, and, like all the metric scales, is the rational system.
It is, therefore, used frequently hereafter in order to familiarize
students with it. In occasional discussions where one scale is used,
approximate equivalents in the other scale are added in parentheses.
The following rules will be found useful in changing readings
from one scale to the other :
To change Fahrenheit to Centigrade, subtract 32 from the number
of degrees and multiply the remainder by f .
70° F. = (70 - 32) X * = 211° C.
To change Centigrade to Fahrenheit, divide the number of degrees
by f and add 32.
_ 10° C. = (- 10 ^ $) + 32 = 14° F.
SUMMARY
The sun is the source of the heat and light of the earth.
Heat has the capacity to do work, and is therefore a form of
energy. The sun is the source of the energy on the earth.
If a body has the ability to do work without actually being
at work, it is said to have potential energy ; the energy of a
body at work is called kinetic. There are different forms
of energy, such as heat, light, electricity, gravitation, chemi-
cal energy, and mechanical energy. Energy can neither be
created nor destroyed, but one form of energy may readily
be changed into another. Heat causes most substances to
94 THE SUN'S GIFT OF HEAT
expand; withdrawal of heat causes most substances to
contract.
Mass is the amount of matter in a body. Volume is the
amount of space a body occupies. Density depends on the
amount of matter in a given volume. Weight is the measure
of the earth's attraction, or gravity, for any mass.
Heat is molecular energy. Sufficient heat will change
solids to liquids and liquids to gases. The most common
way of producing heat is by burning. Burning is a chemical
process in which atoms of oxygen unite with atoms of fuel
elements, such as carbon and hydrogen. Heat may also
be produced by chemical, mechanical, or electrical action.
The temperature to which a substance must be brought be-
fore it will burn is called its kindling temperature. Keep-
ing fuel elements in a furnace at their kindling temperature
and providing just the right oxygen supply are the two
problems to be solved in saving fuel and abating the smoke
nuisance. Fire can always be extinguished if the supply of
air that reaches it can be shut off.
In gas, metal, and liquid thermometers, substances that
expand and contract uniformily through ordinary tempera-
tures are employed. The two most commonly used ther-
mometer scales are the Centigrade and the Fahrenheit. Some
substances require more heat than others to raise their
temperatures. Water absorbs more heat than almost any
other known substance. When a solid changes to a liquid
or a liquid to a gas, a tremendous amount of heat is ab-
sorbed which does not raise the temperature. When the
changes are reversed, this heat is given out.
Heat may be transferred by conduction, convection cur-
rents, and radiation. The principle of heat transference
accounts for the efficiency of stoves and furnaces, as well as
QUESTIONS 95
of refrigerators. Fireless cookers, thermos bottles, revolving
doors, refrigerators, etc., are devices to prevent rapid trans-
ference of heat.
QUESTIONS
When we say a body possesses energy, what do we mean ? Give
an example of each of the two kinds of energy.
You have used a great deal of energy to-day. Where did this
energy come from ?
What is the Law of the Conservation of Energy? What do we
mean when we speak of "lost energy"?
Where have you seen the effects of expansion due to heat?
Explain the difference between mass, volume, density, and
weight.
What is meant by saying that a substance is hot?
Why are iron and type-metal better suited for casting than
copper and zinc?
Describe three ways of producing heat.
How are fires started?
What are the conditions necessary for obtaining all the heat
possible from fuel ?
Describe the different means you would employ in putting out
fire.
France uses the Centigrade thermometer scale. If the tempera-
ture of Paris is reported as 25° C., what would the corresponding
temperature be in the thermometer scale generally used in the
United States?
Ponds near the Great Lakes freeze entirely over. Why do not
the Great Lakes freeze ?
Why would it not be as well to put ten pounds of ice-cold water
into the refrigerator as ten pounds of ice?
In what ways is heat transferred?
Describe how you would prepare from the ordinary materials
you have at hand a crude, inexpensive, fireless cooker.
CHAPTER V
THE ATMOSPHEEE AND ITS SEEVIOE TO MAN
The Origin of the Atmosphere. — When the earth cooled
from its original intensely hot condition, the substances
BLUE HILL OBSERVATORY, MILTON, MASSACHUSETTS
One of the first places in America where conditions of the upper
atmosphere were studied.
which did not chemically combine to form liquids and solids,
or which required a very low temperature for their consoli-
dation, were left still in the gaseous state around the solid
96
THE COMPOSITION OF THE AIR 97
core. This gaseous envelope, composed of these substances
surrounding the earth, we call the atmosphere. Some of these
gases are inert; that is, they do not readily form chemical
combinations with other, substances. Others have formed
extensive combinations, but they exist in such large quanti-
ties that they were not thereby exhausted.
The Composition of the Air. — Experiment 35. — (Teacher's
Experiment.) — Having rounded out a cavity in a small flat cork,
cover the cavity and surface around it with a thin layer of plaster
of Paris. After the plaster has set and become thoroughly dry,
float the cork on a dish of water with the cavity side up. Place
a piece of phosphorus as large as a pea in the
cavity and carefully light it. (Figure 48.) (Great
care must be taken in handling phosphorus, as it
ignites at a low temperature and burns with
great fierceness. It must always be cut and
handled under water.)
As soon as the phosphorus is lighted, cover
it with a wide-mouthed bottle. Be sure that FIGURE 48
the mouth of the bottle is kept slightly under
water. The water will be found to rise in the bottle. The phos-
phorus soon ceases to burn. White fumes are formed, but these
soon clear up. A clear gas is left in the bottle, but this cannot
be air; for if it were, the phosphorus would have continued to
burn in it, since it burns in air. If it were not for this property
of not permitting phosphorus to burn, the gas left in the bottle
could not be distinguished by ordinary means from air.
The gas fills more than three fourths of the bottle, so that more
than three fourths of the air is composed of a gas which does not
support combustion. This gas is called nitrogen. The other constitu-
ents of the air must also be transparent colorless gases, since the air
is transparent and colorless. The most important of these is called
oxygen. The phosphorus united with this and formed the white
fumes. These fumes dissolved in the water, leaving the nitrogen.
Be careful to put the cork on which the phosphorus was burned
in a place where it cannot cause a fire.
98 THE ATMOSPHERE AND ITS SERVICE TO MAN
Although the air appears to be a simple gas and was so
considered until the end of the eighteenth century, it has
been shown to be a* mixture of several different colorless gases.
One of these, oxygen, supports combustion, as we have
already learned; another, nitrogen, neither burns nor sup-
ports combustion. These two gases make up by far the
greater part of the air about us, and occur in the proportion
of about one part of oxygen to four parts of nitrogen. Car-
bon dioxide is also found in the air in the proportion of about
3 parts to 10,000. There are in addition very small quan-
tities of several other gases, but these are not of suffi-
cient importance to be studied here. Besides the gases,
the air contains other matter, such as water vapor, dust
particles, and microbes.
Almost all of us have had occasion to observe that if there
is a slight leak of gas from the gas stove in the kitchen, the
" smell of gas " will permeate the whole house. It makes
no difference whether there are currents of air to carry the
gas or not. Gases, whether heavy or light, mix readily
with each other, or diffuse. As a rule, therefore, the propor-
tion of oxygen, nitrogen, carbon dioxide, and other gases
is the same for all places on the surface of the earth.
Oxygen is the most important part of the air to animals,
for without it they could not live. They breathe in oxygen,
and breathe out carbon dioxide. All the heat and energy
animals have is due to their power of combining oxygen with
carbon. Plants also have need of oxygen, but to a smaller
degree than animals.
The nitrogen is needed to dilute the oxygen. If oxygen
were undiluted, animals could not live; and a fire once
started would burn up iron as readily as it now does wood.
Plants and animals need nitrogen too, but it is of no use to
THE COMPOSITION OF THE AIR 99
them as it occurs free in the air. Certain very low and
minute forms of life known as bacteria have the power to
take nitrogen from the air and to prepare it for the use of
plants. The nitrogen must be chemically compounded with
other substances before it can be used either by animals or
plants as food.
Plants need carbon dioxide as much as animals need
oxygen. The growth of a plant is due to the power it has
of tearing apart the carbon dioxide by the help of the sun
and of building the carbon into its structure. It returns
the oxygen to the air to be used again by the animals and
the plants. By far the greater part of plants is made from
the carbon which they get from carbon dioxide.
Animals have not the bodily power of breaking down
carbon dioxide to obtain oxygen from it ; consequently they
smother in this gas. Since men and other animals are con-
stantly using up the oxygen in the surrounding atmosphere
and are breathing out carbon dioxide, the rooms where they
stay must be properly ventilated.
Carbon dioxide is heavier than air and has a tendency to
accumulate in wells and unventilated mines. Workmen
caught in this gas are smothered exactly as if by drowning.
Frequently in coal-mine explosions so much carbon dioxide
is formed that but little free oxygen remains ; and so miners
often escape an explosion only to be smothered by the carbon
dioxide (choke damp, as they call it). Before going down
into a well or cistern, careful workmen always lower a lighted
candle to test for the presence of carbon dioxide. If this is
present in large quantities the candle is extinguished.
In some places, such as Dog Grotto near Naples, Italy,
and Death Gulch in Yellowstone Park, carbon dioxide is
being steadily emitted from the ground. Since these places
100 THE ATMOSPHERE AND ITS SERVICE TO MAN
are low and sheltered from the wind, the heavy gas accumu-
lates in sufficient quantities to be fatal to animals that at-
tempt to pass through them.
Moisture in the Air : Evaporation. — The atmosphere
at all times and under all conditions contains some mois-
ture. In the air of even the driest desert there is some
water vapor. Plants and animals both need it. Were
it not for the moisture in the air there would be no rain ;
and without rain no land life could exist. Thus the air,
which contains oxygen and water vapor for both plants
and animals, carbon dioxide for plants, and nitrogen to
dilute the oxygen, is one of the most important life factors
of the earth.
Experiment 36. — Carefully weigh a dish of water and put it in
a convenient place where there is free access of air. After some
hours weigh it again. What causes the change of weight ? Try
this experiment with a test tube, a watch crystal, and a wide-
mouthed beaker, under various conditions and in various places.
When water is exposed to the air, it gradually disappears
into the surrounding atmosphere. This process is called
evaporation. Evaporation takes place only from the sur-
face of a body of water. It may occur at any temperature ;
but since heat is absorbed in the process of evaporation
(page 85), the more heat there is available, the more
rapid will be the evaporation.
Evaporation must not be confused with boiling. Heat
is absorbed in both processes; but boiling takes place only
at a definite temperature and goes on inside the liquid.
If the water surface is large and the temperature high,
there is a large amount of evaporation and the water rapidly
rises into the air. In the tropics the evaporation from the
MOISTURE IN THE AIR
101
water surface amounts to perhaps eight feet per year. This
means that the energy of the sun evaporates about five hundred
pounds of water from every square foot of the surface every
year. In the polar latitudes the amount
of evaporation is perhaps a tenth of that
in the tropics.
From every water surface on the globe,
however, a large amount of water is
evaporated each year.
Effect of Temperature on the Capacity
of the Air to Hold Moisture. — Experi-
ment 37. — Take a liter flask and put into it
just sufficient water to make a thin film on the
inside of the flask when shaken around. Now
warm the flask gently, never bringing its tem-
perature near to the boiling-point, until the
water disappears from the inside and the flask
appears to be perfectly dry. Having tightly
corked the flask, allow it to cool. The flask
appears dry when warm and on account of having been corked
tightly no moisture could have entered it. The air in the flask
was perfectly transparent both before and after heating. The film
of water around the inside of the flask was taken up by the air
when it was warmed but the moisture reappeared when the flask
was cooled.
Experiment 38. — Fill a bright tin dish or glass beaker with ice
water and after carefully wiping the outside allow it to stand for
some time in a warm room. Can water go through the sides of
the dish? Does the outside of the dish remain dry? If water
collects upon it, from where does the water come ? See if the same
results will follow if the water within the dish is as warm as or
warmer than the air in the room.
Experiment 39. — Partially fill a dish or beaker like that in the
previous experiment with water having a temperature a little
warmer than that of the room. Gradually add pieces of ice, con-
BY RAPID EVAPO-
RATION
102 THE ATMOSPHERE AND ITS SERVICE TO MAN
tinually stirring with a chemical thermometer. Note the tem-
perature at which a mist begins to appear upon the outside of the
dish. When the mist has appeared, add no more ice but stir until
the mist begins to disappear. Note this temperature. Take the
average of these two temperatures. This average is probably
the temperature at which the mist really began to form. This
temperature is called the dew point.
When we wish to dry clothes, we place them in a warm
room or in the sunshine. Soon we find that the water has
left the clothes. It must have gone into the air. It would
thus appear that when the temperature of the air is raised,
it has the capacity of taking up more moisture than when it
is cold. This was seen in Experiment 37. Both Experi-
ments 38 and 39 showed that when air is sufficiently cooled,
it begins to deposit moisture. Experiment 39 showed the
temperature at which the deposition began. This was
the dew point for that time and place.
This property that air has of taking up a large amount
of moisture when heated and of giving it out when cooled
is the cause of our clouds and rain.
Humidity. — The condition of the air as regards the
moisture it holds is called its humidity. The amount of
vapor present in the air is spoken of as its absolute humidity.
The amount of vapor in the air as compared with the amount
the air would contain if it had all it could hold is known as
its relative humidity. For example, air at 80° F. is capable
of holding almost 11 grains of water vapor per cubic foot.
Suppose it actually contains 6 grains of water vapor per
cubic foot. It will be loaded then with about TT, or a little
more than | of the moisture it would contain if it were
saturated (that is, had all the moisture it could hold). This
fraction represents the relative humidity of the atmosphere.
HUMIDITY 103
By determining the dew point as was done in Experiment 39
and comparing this with tables which have been prepared
by meteorologists from many observations, relative humidity
can always be approximately determined. An instrument
STRATO-CUMULUS CLOUDS
Typical low level clouds, indicating showers.
for determining the relative humidity of the air is called a
hygrometer (Figure 50).
To be considered moist, air must contain at least more
than half the amount of moisture it is capable of carrying.
If air contains much more than half the moisture it can carry,
its humidity is said to be high. When air which has a high
humidity is cooled it soon reaches a point of temperature
where it is saturated (the dew point). If the temperature
falls below this point, the air must deposit some of its mois-
104 THE ATMOSPHERE AND ITS SERVICE TO MAN
ture. It is important not to think of the dew point as a
fixed point of temperature, like that of freezing or boiling.
The dew point depends not only upon
the temperature of the air but also
upon the amount of vapor in the air.
Condensation of Moisture of the Air.
— Moisture of the air may condense
into little droplets high above the
earth's surface, making clouds. If
these droplets form near the surface of
the earth, the cloud of moisture is
called fog. If it collects on objects on
or near the ground, it is called dew.
When droplets in the clouds become so
large that they are too heavy to remain
suspended in the air, they fall as rain.
Rain and dew can form only when the
dew point is higher than the freezing
point. When the dew point falls below
the freezing point, moisture of the
atmosphere condenses as snow, sleet, or
frost. Thus a fall of snow on a moun-
tain is sometimes accompanied by rain
FIGURE 50.— AN HY- in the valley.
GEOMETER
Cooling by Evaporation. — Experi-
ment 40. — Mark with a rubber band the height of the water col-
umn in an air thermometer (Figure 51). Let fall a few drops of
ether or alcohol on the bulb, and notice the change in the height
of the column. Place a little ether on the back of the hand. What
kind of sensation does it give ? (Be careful to use only a few drops
of ether, as it is bad to breathe it too freely.)
COOLING BY EVAPORATION
105
When the ether was dropped on the air thermometer
bulb it evaporated and the water column rose just as it did
FOG
A low cloud formed near the surface of the earth.
in Experiment 27. Ether is one of a number of liquids,
such as gasoline and alcohol, that evaporate more rapidly
than water. The more rapidly a liquid evaporates, the
more rapidly it takes up heat from its
surroundings. That is why ether feels
colder to the hand than water. In many
places, at the present time, advantage is
taken of rapid evaporation in the con-
struction of ice and cold-storage plants.
The canvas desert water-bag (Figure
52) illustrates a simple application of the
principle of cooling by evaporation. The
water seeps very slowly through the bag, FIGURE 51
and the evaporation of this seeping water
absorbs the heat from the water in the bag and keeps
it cool enough to refresh the thirsty traveler. Nature
106 THE ATMOSPHERE AND ITS SERVICE TO MAN
FIGURE 52. — DESERT
WATER BAG
provides for keeping the human body and the bodies
of some other animals at the right temperature by this
process of evaporation. The
warmer the healthy body gets
the more it perspires, and the
evaporation of the perspiration
keeps down the temperature. In
case of fever, the pores of the
body close up, perspiration ceases,
and the temperature immediately
rises. The physician often has to
use ice packs to do the work of
normal evaporation until perspira-
tion resumes.
Plants are also kept cool by the
evaporation of water which exudes from their leaves. This
is called transpiration.
Humidity and Comfort. — The humidity of the air has
much to do with our bodily comfort. In quiet warm air,
nearly saturated with moisture, the perspiration cannot
readily evaporate and cool the body. Thus a temperature
of 80° F. with a high relative humidity may be more un-
comfortable than a temperature of 95° F. with a low relative
humidity. On a humid day the perspiration that evap-
orates brings the air that is near the body closer to the
saturation point, and we fan ourselves to move it away
and.to allow the less moist air to take its place. Any breeze
gives relief because it keeps changing the air around the
body. An electric fan, although it in no way cools the air,
helps evaporate the perspiration by keeping the air in mo-
tion. Crowded rooms often become " close " because of a
HUMIDITY AND COMFORT
107
layer of densely humid air around the crowd that results
from the moisture of the breath and the evaporation of
perspiration. Such rooms may often be rendered quite
comfortable by opening more windows or by starting an
electric fan, even when there is no way of lowering the
temperature of the atmosphere.
In cold weather when the temperature of the body is
considerably higher than that of the surrounding atmos-
phere, moist air chills us. This is because moist air is a
better conductor of heat than dry air and readily absorbs
heat from the body.
The air in most living rooms in winter is too dry. Since
the air in the room has been heated it is capable of holding
more moisture than the
outdoor air . Unless water
is supplied to it, its rela-
tive humidity is much
lower than that of the
air outside. In some
heated rooms in winter
the air is really drier
than the air over the
deserts. In this dry air
the perspiration evapo-
rates very rapidly and FIGURE 53. — HOMEMADE HUMIDIFIEB
makes us cold even
though the temperature of the room is high. This hot,
dry air is injurious to the eyes, irritating to the nerves,
harmful to the membranes of the nose and throat, and con-
ducive to colds. Such air dries the moisture out of the glue
in the furniture, often warps woodwork, and tends to shrivel
up everything in the room.
108 THE ATMOSPHERE AND ITS SERVICE TO MAN
In the interest, therefore, of the conservation of health,
as well as of fuel and of furniture, open vessels of water
(humidifiers) should be kept on stoves, radiators, or regis-
ters, in order to keep the air of living rooms moist. Hang-
ing up cloths, the ends of which are in pails of water, will
serve the purpose even better, because they increase the
surface from which evaporation takes place and thus furnish
more water to the air in less time. (Figure 53.) There are
many patented devices for humidifying, but the principle on
which all of them are constructed is the same as that of the
homemade humidifier. A temperature of between 65° F.
and 70° F. will make a room comfortable if there is sufficient
moisture in the air.
Weight of Air. — Experiment 41. — Into a five-pint bottle insert
a tightly fitting rubber stopper through which a glass tube extends.
To the outer end of the glass tube tightly fit a thick-
r— • flf— walled rubber tube of sufficient length for the attach-
ment of an air pump. Put a Hoffman's screw upon the
rubber tube. (Figure 54.) See that all connections are
air-tight. Weigh carefully the apparatus as thus
arranged. Now attach the rubber tube to an air pump
and extract the air from the bottle. When all the air
FIGURE 54 ^at can be exhausted has been removed, close the
rubber tube tightly with the Hoffman's screw and weigh
again. Unclamp the Hoffman's screw and allow the air to enter
the bottle. The weight should be now the same as at first. Or,
instead of weighing a bottle of air, weigh an incandescent light bulb.
Make a hole in it with a blowpipe and weigh again. Is the weight
now the same as before ?
We have found by the previous experiment that air has
weight. With the apparatus used it was impossible to
tell exactly the weight of the air extracted or to determine
the weight of a definite volume of the air. If we had been
AIR AS AFFECTED BY HEAT AND COLD 109
able to do this, we should have found that on an average day,
at sea level, the weight of a liter, a little more than a quart,
of air, is about 1.2 grams. Twelve cu. ft. weigh about one
pound. The air extends to so great a height that although
very light, the weight of so great a mass of it is enormous.
Expansion of Air when Heated. — Air expands very
much when heated, as was seen in Experiment 18. It is
found that if air at freezing is heated to the temperature
of boiling water, it will expand about TV of its volume. The
force with which air expands is so great that sometimes
when buildings are on fire and there is no opening for the
confined air to escape, the walls are blown out or the roof
blown off by the expansion of the hot air, and great injury
is done to those fighting the fire. That air expands upon
being heated is readily seen when an air-filled toy balloon
is brought frorn the cold outer air
into a hot room, — the covering
begins at once to tighten and the
balloon to swell.
Weight of Air as Affected by
Heat and Cold. — Experiment 42. — FIGURE 55
Take two open flasks of nearly the
same weight and capacity and balance in as nearly a vertical
position as possible at the ends of the arms of a beam balance.
Bring the flame of a Bunsen burner to the upper side of the bulb
of one of the flasks so that the hot air currents that are generated
will have no upward push on the flask. (Figure 55.) Do not
allow the hot air to get under the flask. What is the effect?
As the previous experiment shows, and as we should
expect from the fact that air has been found to expand
when heated, hot air is lighter than cold air. A liter of
air at freezing under ordinary pressure weighs about 1.293
110 THE ATMOSPHERE AND ITS SERVICE TO MAN
grams, but at the temperature of boiling water it weighs
only about .946 grams. So a volume of cold air, being
heavier, will exert more pressure at the surface of the
earth than an equal volume of hot air.
As air is a gas whose particles can move freely among
themselves we should expect that a heavier column of cold
air would sink down and
distribute itself along
the surface under sur-
rounding lighter air,
just as a column of
water falls when its
supports are withdrawn
and forces up the lighter
air which surrounds it.
A similar action is
seen when water is
poured upon oil : the
water sinks to the bot-
tom and forces the oil
FIGURE 56. — HOT-AIR FURNACE to rise. Thus if air is
Cold air presses in from the outside and heated at any place, WC
causes the hot air to rise through the h }d t ^ there
pipes and registers.
would be a rising current
of hot air and a current of colder air creeping in to take
its place. The winds of the earth are due to this property
of air. It is this tendency of heated air to rise that makes
hot-air furnaces useful for heating houses (Figure 56).
Valleys are generally colder than the surrounding hill-
sides, so that delicate crops can be grown successfully
on the hillsides although those in the valley may be frost-
bitten.
AIR AS AFFECTED BY HEAT AND COLD 111
FIGURE 57
Experiment 43. — Use a convection apparatus or take a tight chalk
box and in two places on the top punch holes in a circle not quite
as large as the bottom of a lamp chimney. Place a small lighted
candle at the center of one of the circles of holes
and a lamp chimney, tightly sealed to the box,
about each circle. Hold a smoking piece of paper
above the chimney which does not inclose the
candle. (If a pane of glass is put into one of the
vertical sides of the box, better observations can
be made.) (Fijgure 57.) What happens? Put
out the candle and carefully heat the chimney
with a Bunsen burner. Is there the same action
as before ? Why is it that sparks rise from a fire ?
What is meant by the draft of a stove ? Why in
order to ventilate a room is it best to open a window at the top and
bottom?
The refrigerator illustrates the effect of temperature upon
the circulation of air (Figure 58). The coldest air in the re-
frigerator is nearest the ice. This being heaviest naturally
falls. The farther away from the ice it gets the warmer and
therefore the lighter it be-
comes. The falling current
of cold air pushes the
warmer air up through the
compartments on the op-
posite side and back to
the ice again, thus making
a continuous circulation.
It is not generally recog-
nized that an electric fan
J
FIGURE 58. — REFRIGERATOR
Diagram illustrating circulation of air
when the doors are closed.
may be made just as use-
ful in winter as in summer.
The warm air in a room
tends to rise to the upper
112 THE ATMOSPHERE AND ITS SERVICE TO MAN
part of the room. A fan placed as near the ceiling as
possible will force this warm air down to a lower level, and
in this way make all parts of the room more nearly uniform
in temperature. This often proves an effective remedy for
cold floors. In winter the air near windowpanes is often
reduced below its dew point and films of ice form inside
the panes. This can be prevented by using a fan to keep
a fresh supply .of warm air moving across the glass. Most
merchants have learned to apply this principle in keeping
their display windows clear in severe weather.
Ventilation. — The movement of air caused by its heat-
ing and cooling provides a means for ventilating rooms and
buildings in winter. In warm weather we do not have to
be persuaded to keep our windows open; but when winter
comes, many people become careless about ventilating their
houses. Health requires that a person have pure, normally
moist air to breathe. Sleeping rooms as well as living
rooms must be constantly supplied with outdoor air. The
old notion that night air was harmful is contrary to the
truth. Fresh air day and night is essential to the main-
tenance of health.
Several ways have been devised for ventilating large
buildings and for maintaining proper air conditions, but
these require mechanical means for driving or for draw-
ing the air into the building, and are not suitable for
dwellings.
Houses heated by hot-air furnaces in which the cold air
flue is properly cared for (Figure 56) need only a provision
for the exit of hot, stale air. An open grate or fireplace in
which there is a fire, or a window in each room opened slightly
at the top will accomplish this.
VENTILATION
113
Houses heated by steam or by hot water sometimes have
special arrangements for ventilating (Figure 44). In some
houses the radiators are placed in open air ducts beneath the
floor. The fresh air enters these ducts from outdoors, is
warmed as it passes the radiators, and rises through registers
in the floor to warm the rooms. The cold air from the out-
side keeps pushing the warmed air up out of the ducts and
flowing in to take its place. Thus a continuous circulation
is maintained over the radiators into the rooms. The same
arrangements must be made for the exit of stale, hot air as
are made when the hot air furnace is used.
Many houses, however, cannot be ventilated except
through the windows and doors. It is most important
to learn how this may be done effectively. One simple
method is to cut a narrow board into a length that exactly
equals the width of the window sash.
Raise the lower sash, fit the board into
the running groove, and close the sash
down on it. This leaves an open space
between the upper and the lower sash
through which fresh air may enter. If
the upper sash be pulled down to leave
an opening of an inch or so at the top,
an exit for the stale air is provided.
According to another method, a board
ten or twelve inches wide is cut just long
. , ,1 • •! * ,1 FIGURE 59. — ADJUST-
enough to reach across the inside or the ABLE VENTILATOR
casement. This board is placed length-
wise on the inside sill with its ends fastened to the sides of
the casement. When the lower sash is raised, the board de-
flects the current of cold air upward so as to prevent a direct
draft. In this case the opening between the sashes serves
114 THE ATMOSPHERE AND ITS SERVICE TO MAN
as an exit for the stale air, and the upper sash does not have
to be lowered. In severe weather this is more successful
than the first method. An adjustable ventilator of this
kind is shown in Figure 59.
But the cloth screen is probably the most successful
means of steady ventilation in severe weather. For houses
that have only casement windows it is about the only method.
Make a screen frame that fits snugly into the casement.
Cut a piece of muslin to fit the frame and tack it on just as
you would wire screening, being sure to stretch the muslin
tight as you put it on the frame. With this in place, the
casement window may be opened wide in the most severe
weather without any danger of direct drafts but with assur-
ance of fresh air supply. The cloth screen may be adapted
to the sash window, and it is especially useful on stormy
nights because it makes it possible to keep a sleeping room
window wide open all night.
Whatever method of ventilation is used, the windows and
doors should be opened once or twice every day so that cold
fresh air may blow in and flush out the stale air of the rooms.
Fresh air and sunlight are man's cheapest doctors.
Pressure of the Atmosphere. — Experiment 44. — If a tin can
with a tightly fitting screw cap can be easily procured, boil a little
water in it, having the screw cap open so that the steam can readily
escape. While the water is still strongly boiling, quickly re-
move the can from the heat and tighten the cap. Be sure not to
tighten the cap before removing the can entirely from the heat.
Set the tin thus closed upon the desk and observe. What hap-
pens as the steam condenses ? Why ?
Experiment 46. — By means of an
air pump exhaust the air from a pair of
Magdeburg hemispheres. (Figure 60.)
Now try to pull the hemispheres apart. FIGURE 60
PRESSURE OF THE ATMOSPHERE
115
FIGURE 61
FIGURE 62
It cannot be done as easily as before the air was exhausted.
Why?
Experiment 46. — Fill a glass tumbler even full of water and
press upon it a piece of writing paper. (Figure 61.) Be sure that
the paper fits smoothly to the rim of the tumbler.
Take the tumbler by its base and carefully invert
it over a pan. Does the water fall out ? If not,
why not? While the tumbler is in the inverted
position, insert the point of a pencil between the
paper and the rim of the tumbler. What happens ?
Experiment 47. — Fill a bottle with clean water
and fit it tightly with a rubber stopper having two
holes in it. Plug one of the holes tightly with a glass
tube one end of which has been closed by heating in
a Bunsen burner. Through the other hole put an
open glass tube 10 to 15 cm. long. See that both
tubes fit tightly in the stopper and that the stopper
fits tightly in the bottle. (Figure 62.) Now attempt
to " suck " the water out of the bottle through the
open tube. Does it come out freely? Pull out the glass plug.
Does it come out any better ? If so, why ?
Anything that has weight must exert pressure upon the
surface upon which it rests. The air has been found to have
weight, and therefore it must exert pressure at the surface
of the earth. It is a gas; and since the particles of a gas
easily move over one another, this pressure must be exerted
equally in all directions.
We do not feel the pressure of the atmosphere because the
pressure inside us balances the pressure from without. If
two eggshells, with their contents removed — one of them
with the holes left in it, and the other completely sealed -
should be sunk to a considerable depth in water, which one
would be crushed by the pressure of the water, and which
would not ? This illustrates why objects on the surface of
the earth are not crushed by the pressure of the air.
116 THE ATMOSPHERE AND ITS SERVICE TO MAN
In the preceding experiments atmospheric pressure ac-
counted for the various things that happened. When the
steam in the can cooled, it condensed and occupied less
space. The pressure of the atmosphere from the outside,
therefore, pushed the sides inward. With the atmospheric
pressure lessened inside the Magdeburg hemispheres, the
full atmospheric pressure on the outside held them together.
The inverted glass kept the atmosphere from pressing down
on the surface of the water immediately under it. The up-
ward pressure of the atmosphere on the paper was greater
than the downward pressure of the water. When you
withdrew air from the glass tube, the pressure of the at-
mosphere on the surface of the water forced the water up
into the tube to take the place of the air that had escaped.
Variation in pressure due to heating and cooling of air
explains circulation and drafts. A column of cold air is
denser and therefore heavier than a corresponding column
of warm air. The cold air, therefore, presses the warm
air up, and takes its place below. ^
Measuring Atmospheric Pressure. — Experiment 48. —
(Teacher's Experiment.) — Take a thick-walled glass tube of about
\ cm. bore and 80 cm. length. Close it at one end. Fill the tube
with mercury. (Be sure to place the closed end of the tube in a
large vessel so as not to waste the mercury if you spill it.) Place
the thumb tightly over the open end of the tube and invert it in
a vessel of mercury. If you are at or near sea level, the mercury
column will drop to a height of about 75 cm. (about 30 inches)
and will stand there. This is known as Torricelli's Experiment,
because Torricelli first performed it and explained it.
The space above the mercury is without air, and there-
fore no atmospheric pressure is exerted at the top of the
column of mercury. The column of mercury is pressing
MACHINES THAT MAKE USE OF AIR PRESSURE 117
down on the surface of the mercury in the vessel. The
atmosphere is also pressing down on the surface of the mer-
cury in the vessel. The one pressure balances the other.
It makes no difference what the diameter of the column of
mercury is, it will stand at just the same height. If then we
weigh a column of mercury an inch square at the base and
thirty inches tall, we can find what the approximate pressure
of the earth's atmosphere is on every square inch of the earth's
surface at sea level. Such a column weighs about fifteen
pounds. Therefore the pressure of the atmosphere is about
fifteen pounds to the square inch at sea level.
Experiment 49. — (Teacher's Experiment.) — Take a thick-walled
glass tube of about £ cm. bore and about 80 cm. length and slip
tightly over the end of it about 10 cm. of a thick-
walled flexible rubber tube 30 cm. in length.
Firmly secure the rubber tube to the glass tube
by winding tightly around them many turns of
string, making it impossible for the rubber tube
to slip or admit air. Completely close the rubber
tube with a Hoffman's screw just beyond the FIGURE 63
place where it leaves the glass tube. Placing this
closed end in a large dish so as not to waste any mercury, fill the
glass tube with mercury. Place the thumb over the open end of
the tube and invert it in a cup of mercury. If the connections
were made tight, the mercury will not fall far below the end of the
glass tube. The air pressure keeps the mercury up. This is a
simple form of barometer.
While the tube is still standing in the mercury cup take another
glass tube similar to the first and attach it to the open end of the
rubber tube in the same way as the first was attached. Place
the free end of this tube in a dish of colored water and gradually
open the Hoffman's screw. (Figure 63.) The water rises in the tube.
Why ? What is meant by sucking water up a tube ?
Machines that Make Use of Air Pressure. — Lift Pump.
— The ordinary lift pump (Figure 64) is a machine which
118 THE ATMOSPHERE AND ITS SERVICE TO MAN
utilizes air pressure for " lifting " water. When the piston
of the pump is raised from the bottom of the cylinder a
partial vacuum is created in the cylinder. The air pressure
on the water in the cistern forces the water up the pipe and
through the valve B into the cylinder. When the piston
descends the valve B in the bottom of the cylinder is closed
by the weight of the water and the valve A in the piston
opens allowing the water to flow through
to the upper side of the piston. As the
piston is once more raised the valve A
closes and the water above the piston is
lifted and flows out the spout. Air pres-
sure again forces more water up the pipe
and through the valve B into the
cylinder. The water continues to rise
into the cylinder and to be lifted out as
long as the pump is worked.
Lift pumps were in use for 2000 years
before any one successfully explained
their operation. Galileo observed that
in the best lift pumps the water could
not be made to rise higher than 32 feet,
but he died without being able to ex-
plain why. When Torricelli, his pupil and friend, performed
the experiment with the mercury tube, and found that atmos-
pheric pressure would support a column of mercury about
30 inches high in a vacuum, he explained what had puzzled
Galileo. Since mercury is about thirteen and one-half
times as heavy as water, the pressure of the atmosphere
would support a column of water thirteen and one-half
times as high as the column of mercury. In a perfect
vacuum, therefore, the pressure of the atmosphere would
64. — DIA-
OF A LIFT
THE SIPHON
119
FIGURE 65
support a column of water about 34 feet high. But since it
is impossible to create a perfect vacuum with the piston and
valves, water never rises as high as this in
a lift pump. In practice the average limit is
about 27 feet.
The Siphon. — Experiment 60. — Fill an eight-
ounce bottle with clean water and fit it tightly
with a two-holed rubber stopper. Through one of
the holes in the stopper insert a tightly fitting
glass tube, which reaches nearly to the bottom of
the bottle and extends an incji or two above the stopper. Attach
to this glass tube a clean rubber tube which is long enough to reach
below the bottom of the bottle. Fit a sealed glass tube so that it
can be readily in-
serted in the open
hole of the stopper.
(Figure 65.)
" Suck " water
out of the end of
the rubber tube
hanging below the
bottom of the
bottle. As soon as
the water begins to
flow, withdraw the
mouth without rais-
ing the tube. The
water will still con-
tinue to flow. In-
sert the sealed glass
tube in the open
hole of the stopper.
The water stops
flowing. Pull out
A GREAT SIPHON IN THE Los ANGELES tne Slass Plu§- The
AQUEDUCT water begins to
120 THE ATMOSPHERE AND ITS SERVICE TO MAN
flow again. If the water, once started, is allowed to flow, it will
empty the bottle to the end of the glass tube. Any bent tube
arranged in this way, with one arm longer than the other, is called
a siphon.
In Experiment 50, the water in the siphon was pressed
outward from the bottle by atmospheric pressure minus the
weight of the column of water in the short arm. It was
pressed toward the inside of the bottle by atmospheric pres-
sure minus the weight of the column of water in the long
arm. The atmospheric pressure was practically the same in
both cases, but the weight of the, water column in the short
arm was less than that of the water column in the long
arm. The pressure acting outward was therefore greater
than that acting inward and the water flowed out of the
bottle. The siphon continued to flow as long as the in-
equality of pressure was maintained. When the atmospheric
pressure was shut off by the insertion of the sealed glass
tube, the water of course stopped flowing.
Vacuum Cleaners. — Experiment 61. — Allow a beam of light
to enter a darkened room through a small hole in a curtain. Note
as carefully as you can the different things in the air that the
beam of light reveals.
In the preceding experiment we observed that the air
contained something more than the gases and moisture
which we have learned are in it. There are many solid
particles floating in the air. There were little shreds of
cloth and paper, pieces of dust and soot, and many other
things. The beam of light, however, did not reveal every-
thing that was floating in the air. There were many living
organisms, tiny plants (bacteria) , too small to be seen except
by the aid of a high-power microscope.
These minute living things are scattered all through the
VACUUM CLEANERS
121
air, sometimes living on dust particles and sometimes un-
attached to anything. Only a few of the bacteria are harm-
ful, and they are usually not very abundant. Sunlight
kills most of them in a short time, but moisture and dark-
ness furnish conditions favorable for them. They are
Courtesy of Elgin Sales Corporation
A MODERN STREET SWEEPER
The left end is the forward end. This machine sprinkles, sweeps, and
collects the sweepings. The operator is working the lever which
empties the machine.
particularly abundant in the dust of the street and wherever
foul refuse accumulates. When they get into a house they
settle and multiply rapidly if they happen to light upon a
warm, moist place where the sunshine is not too bright.
Ordinary dusting and sweeping simply scatter them about
and keep them floating 'in the air for hours, for us to
122 THE ATMOSPHERE AND ITS SERVICE TO MAN
breathe. Carpet sweepers and oiled dust cloths do much
to prevent stirring up the dust and bacteria, but vacuum
cleaners are even more effective.
The vacuum cleaner is a device to utilize air pressure for
cleaning. By means of a pump or a rapidly rotating fan,
the air in the machine is exhausted. Atmospheric pres-
sure forces the air up through the mouth of the machine,
driving the dust and dirt particles with it. This dust-
laden air passes into a closely woven bag, which sifts out and
collects most of the dust. By using this machine no dust is
scattered through the air of the room.
Vacuum cleaners have also been invented for street
cleaning, but outdoor conditions make them less satisfactory
than vacuum cleaners for the household. Most cities de-
pend upon washing or sweeping to keep the streets clean.
Where sweepers are used, they should always be preceded
by sprinklers in order to keep down as much of
the dust as possible.
Decrease of Volume Due to Pressure. — Experi-
ment 52. — In a Mariotte's tube (Figure 66) cause
about a centimeter of mercury in the short arm to
balance the same amount in the long arm. The
pressure inside the short tube will then be equal to
that outside the long tube and will be that of the air
upon the day of the experiment. The short arm will
now be sealed with mercury so that no air can get in
or out. Pour mercury into the long arm. The air
in the short arm will be gradually compressed and will
occupy less and less space. If we remember that the
pressure upon the air in the short arm is the air pres-
FlQUBE 66 . ,, , 1,1 f , i
sure of the day plus the pressure of the mercury
column in the long arm that rises above the mercury level in the
short arm, we can show by careful measurement that the volume of
the air decreases just as the pressure increases.
VOLUME AND PRESSURE 123
As was seen in Experiment 9, the volume of air can be
very much decreased by pressure. It cannot be told from
this experiment whether the volume of the gas decreases
as the pressure increases or whether it decreases much more
rapidly when first pressed upon than afterward. This
can be best shown by the use of the Mariotte's tube as
in Experiment 52. But if the bicycle pump is a good one,
it will answer the question of the rate of decrease quite ac-
curately. It is found that the volume decreases directly as
the pressure increases.
Increase of Pressure Due to Decrease of Volume. — When
a given volume of air is compressed it exerts more pressure.
If air is compressed to one third its original space, it will exert
three times as much pressure as it did before. When the
pressure is removed it regains its original volume. A
puncture in an inflated automobile tire shows how rapidly
and forcibly air will expand from its greater density under
pressure to the density of the surrounding atmosphere.
These properties of compressibility and expansion which air
has, in common with other gases, have many practical ap-
plications. One of the most familiar applications is in the
air pumps of garages. Compressed air is also used to apply
brakes on street cars, steam engines, and railway coaches.
It is used to blow whistles, to ventilate mines and large
buildings, and to* operate heavy hammers, rock drills, and
riveting machines.
The force pump illustrates a use of compressed air. An
" air cushion " is used to deliver a steady stream of water
to a point higher than the mouth of the pump. In the force
pump, the water rises into the cylinder when the piston is
raised, exactly as in the ordinary lifting pump. The piston
124 THE ATMOSPHERE AND ITS SERVICE TO MAN
has no valve, and so when it descends it forces the water
out through the pipe (E) (Figure 67) into the air chamber
(D), thus compressing the air
in it. The valve (C) keeps
the water from running back
when the piston is lifted.
While the piston is ascend-
ing, the pressure of the air
cushion (D) forces a steady
stream through the pipe (^4)
to the tank above.
The force pump is some-
times used to fill tanks in
attics of farmhouses so as
to provide private water-
systems. The principle of
the force pump is used in
the more complicated pumps for water-works, fire engines,
and mines.
Heat Produced by Compression and Cooling Produced by
Expansion. — Experiment 63.— Have a five-pint glass bottle fitted
with a two-hole rubber stopper. Pass through the
holes in the stopper a chemical or air thermometer and
a short glass tube. The lower end of the glass tube
which extends into the bottle should be kept as far as
possible away from the bulb of the thermometer, so
that when the air is exhausted or allowed to enter the
bottle there will be no movement of the air near the
bulb of the thermometer. The end of the column of
the thermometer must be visible above the stopper. pIQUBE
(Figure 68.)
Attach the glass tube to an air pump by means of a thick-walled
rubber tube. Note the temperature of the thermometer within
the bottle and also of the air outside. Quickly exhaust the air
FIGURE 67. — DIAGRAM OF A
FORCE PUMP
PRESSURE AND THE BOILING POINT 125
from the bottle, carefully noting the action of the thermometer.
See that the temperature of the air in the room does not change
during the experiment. Allow the air quickly to enter the bottle
and note the action of the thermometer. The temperature inside
the bottle changes as the air is quickly exhausted, or as it is allowed
to enter the bottle again and thus to increase the density of the
air in the bottle.
It has been found that when air or any other gas expands,
it absorbs heat and cools its surroundings ; and when it is
compressed, it yields heat and warms its surroundings.
This heating and cooling by changes in the density of gas
is called adiabatic heating or cooling. It is taken advantage
of in the manufacture of liquid air and is the same principle
which is utilized in cold-storage plants. This property of
air has. much to do with developing our wind circulation and
storms.
The heating effect of compressing air can be well seen
when an automobile tire is filled. No matter how well the
piston of the pump may be oiled, as the density of the air
in the tire begins to increase, the pump will grow warm
rapidly. This rapid heating cannot be due to friction, as
the pump is not being worked any more swiftly than at
first. It is due to the greater compression of the air. As
this compression increases, the heating increases, the effect
of friction in a well-oiled pump being of small value.
Pressure and the Boiling Point. — Experiment 64. — (Teach-
er's Experiment.) — Fill a strong 500 cc. round-bottomed flask
about one third full of water. Boil the water. While the
water is briskly boiling, remove the flask from the heat, quickly
close its mouth with a rubber stopper, and invert it in a ringstand.
(Figure 69.) (Be sure not to insert the stopper until the flask is
fully removed from the heat.) Pour cold water upon the flask.
The water will again begin to boil.
126 THE ATMOSPHERE AND ITS SERVICE TO MAN
FIGURE 69
In this experiment the steam was condensed by the sud-
den lowering, of the temperature. The condensation of the
steam relieved the pressure on
the surface of the water, and
the water in the flask began to
boil again although it had be-
come considerably cooler than
when it was first boiled. Thus
it appears that if the pressure
on the surface of water is de-
creased, the water will boil at
a lower temperature. Advan-
tage is taken of this in condens-
ing milks and sirups. The
liquids are heated under hoods
from which air is continuously
exhausted. The water is thus "boiled away" at so low
a temperature that there is no danger of scorching the
sirup or the milk.
On high mountains
where the air pressure is
considerably less than at
sea level, water boils at
less than 100° C. In
Denver it boils at 95°
C.; in the City of
Mexico, at 92° C.; in
Quito, Ecuador, at 90°
C. Because water boils
in such places at a lower
temperature, it takes
longer to boil food Until PRESSURE COOKER
THE MANUFACTURE OF ICE 127
it is " done." To hasten the process of cooking by boiling
in high altitudes, pressure cookers are often used. The
high pressure developed by keeping the steam imprisoned
raises the boiling point of the water within. The contents
of the cooker may thus be brought to a temperature of
170° C. or even more. This intense heat reduces the time
of cooking and thus saves fuel.
The Manufacture of Ice ; Cold Storage. — We saw hi
Experiment 53 that when air was compressed it gave up
heat and warmed its surroundings. When pressure was
removed, the air absorbed heat and cooled its surround-
ings. Other gases act in the same way. Water vapor, for
example, may be compressed until it gives up so much heat
that it returns to the liquid state.
Ammonia is a gas that at ordinary temperatures is easily
condensed by pressure into a liquid. (This liquid must
not be confused with the aqua ammonia of our kitchens,
which is simply water that has absorbed ammonia gas.)
When the pressure is removed, the liquid ammonia quickly
returns to the gaseous state, and in so doing it absorbs
much heat.
Figure 70 shows the essential construction of an ice
plant. The pump (A) compresses the ammonia gas into
the pipes at (B). The pressure condenses the gas into
liquid, and the cold running water absorbs the heat given
out in the process. The liquid thus cooled is allowed to
run very slowly through the valve (C), into the pipes at
(D). The valves in the pump (A) are so arranged that
while the pump increases the pressure in the pipes at (B)
it decreases the pressure in the pipes at (D). Because of
the low pressure in the pipes (D), the liquid ammonia evapo-
128 THE ATMOSPHERE AND ITS SERVICE TO MAN
rates ; that is, returns to the gaseous state. In so doing it
absorbs heat very rapidly from its surroundings (page 105).
The gaseous ammonia returns to (A) from the pipes (D)
because of the exhaust action of the pump. It is again
compressed into the pipes at (B). Thus the action con-
tinues without loss of ammonia.
The ammonia pipes pass through the brine into which
cans of water have been lowered. Brine is used to sur-
round the ice cans because it does not freeze unless its
FIGURE 70. — DIAGRAM SHOWING ESSENTIAL, CONSTRUCTION OF
AN ICE PLANT
temperature is reduced many degrees below the tempera-
ture at which pure water freezes. The evaporation of the
ammonia in the pipes reduces the temperature of the brine
so low that the water in the cans is frozen, but the brine re-
mains liquid, so that the cans may be easily removed.
In cold storage plants the pipes (D) are placed in the cold
storage rooms to reduce the temperature of the air in the
rooms, just as they reduce the temperature of the brine in
the ice plant.
The Barometer. — On account of the movements of the
air due to heating and cooling and to other causes, the
THE BAROMETER 129
pressure of the atmosphere at any place on the earth's
surface is liable to change. Since measurement of atmos-
pheric pressure is of great importance in the
study of atmospheric conditions, it is necessary
to have an instrument by which changes in pres-
sure can be readily measured. An instrument
designed for this purpose is called a barometer.
There are two kinds of barometers in common
use, the mercurial and the aneroid.
If the tube used in Torricelli's Experiment
(page 116) is fixed in an upright position, and the 1C
height of the mercury marked from time to time,
it will be found that the height of the mercury
column changes slightly, thus indicating greater
or less atmospheric pressure. In Torricelli's Ex-
periment, therefore, we had a mercurial barometer
in rough form.
The best form of this instrument consists of
a glass tube of uniform bore about eighty centi-
meters long and closed at one end. After being
carefully filled with pure mercury, it is inverted
in a cistern of mercury. The cistern of mercury
has a sliding bottom easily moved up and down
by means of a set screw. At the top of the
cistern there is a short ivory peg. The lower
end of the ivory peg is at an exactly measured
distance from the bottom of a scale. The scale
is placed beside a slit near the top of a metallic
tube which is firmly fastened to the cistern and
surrounds and protects the glass tube.
When it is desired to read the barometer, the ,
MERCURIAL
sliding bottom of the cistern is raised or lowered BAROMETER
130 THE ATMOSPHERE AND ITS SERVICE TO MAN
ANEROID BAROMETER
until the top of the mercury in the cistern just touches the
bottom of the ivory peg. The height of the top of the
mercury column is then
read from the scale. In
order to determine the
height with great preci-
sion there is generally
attached to the metallic
tube a sliding vernier
which moves in a slit.
The aneroid barometer
consists in general of a
corrugated metallic box
from which the air has
been partially exhausted.
Within the box is a stiff spring so that the pressure of the
air will not cause it to collapse. Attached to the box are
levers by which any
change in the volume of
the box will be multi-
plied and indicated by
a pointer arranged to
move over a dial with a
scale upon it.
Instruments called
barographs are con-
structed in which a long
lever provided with a
pen point is attached to
the aneroid and made to
record on a cylinder revolved by clockwork. Thus a con-
tinual record is made of barometric readings.
BAROGRAPH
This is arranged so as to record the air
pressure automatically for a week at a
time.
DETERMINATION OF HEIGHT BY BAROMETER 131
Determination of Height by a Barometer. — Experiment 65.
— Carry an aneroid barometer from the bottom of a high building
to the top. Note the reading of the barometer at the bottom
and again at the top. Why is the barometer lower at the top of
the building?
As the pressure of air at any surface is due to the weight
of the air above that surface, it happens that as we go up
the pressure decreases, since there is a continually de-
creasing weight of air above. If the rate of this decrease
is determined, then it is possible to determine the elevation
by ascertaining the pressure.
Although the height of the barometer is continually vary-
ing with the changing air conditions, yet if these conditions
remain about the same, it may roughly be estimated that
the fall of re of an inch in the height of the mercury column
indicates a rise of about 57 feet, and that the fall of a milli-
meter indicates a rise of about 11 meters. These values
are fairly reliable for elevations less than a thousand feet,
under ordinary temperatures and pressures.
At the height of 25 miles the barometric column would
probably not be more than ^ of an inch high. Several
measurements made in different ways indicate that the air
is at least 100 miles in depth, probably more. Nearly
three fourths of the atmosphere, however, is below the top
of the highest mountain. The highest altitude ever reached
by man was about 7 miles.
To study air conditions small balloons to which meteoro-
logical instruments are attached have been sent to a height
of 21 miles. It is found that the minimum temperatures
occur at a height of from 6 to 10 miles. Conditions affect-
ing weather, however, seem to extend to a height of not
much over 3 miles.
132 THE ATMOSPHERE AND ITS SERVICE TO MAN
The atmosphere, of course, must be densest at its lowest
level since the pressure due to the weight of the air is greatest
there. The farther we ascend the less dense the air becomes.
This is the chief reason why people from a lower altitude
" get out of breath " easily when they go to a higher alti-
tude. It is also the reason why balloons and airplanes
OBSERVATION WAR BALLOONS
can ascend only to a limited distance. Since the gas in the
balloon is less dense than the lower atmosphere, it rises to
a point where the density of the air just balances the aver-
age density of the balloon and its burden.
SUMMARY
The gaseous envelope of the earth is called its atmosphere.
The chief gases of the atmosphere are oxygen, which is
SUMMARY 133
necessary for animal life; nitrogen, which dilutes the oxy-
gen; and carbon dioxide, which is indispensable to plant
life.
Water exposed to air evaporates. Through this process,,
the atmosphere always contains moisture. Warm air has
a greater capacity for moisture than cold air. The property
that air has of taking up a large amount of moisture when
heated and of depositing it when cooled is the cause of dew,
fog, clouds, rain, frost, snow, and sleet. When a liquid
evaporates it takes up heat from its surroundings. This
principle is employed by man in ice and cold storage plants
and by nature in evaporation of moisture from the surfaces
of animals and plants. Care should be taken in winter to
keep the air in houses supplied with sufficient moisture.
Air, like every other substance, has weight. Air expands
as it is heated, and so warm air is lighter than cold air. Since
the particles of air or any other gas move freely over one
another, cold air will sink and force up warmer air that sur-
rounds it. Hot air furnaces, circulation in a refrigerator,
and ventilation of houses depend on this principle.
Since anything that has weight exerts pressure on the
surface on which it rests, air exerts pressure at the surface
of the earth, which amounts to about 15 pounds to the
square inch. Lift pumps, siphons, and vacuum cleaners
are among the mechanical devices that make use of air
pressure.
The volume of air decreases directly as the pressure in-
creases. When a given volume of air is compressed, it
exerts corresponding outward pressure. This principle is
applied in operating brakes, steam whistles, ventilating
systems, heavy hammers, and force pumps.
When air or any other gas is compressed it gives out heat
134 THE ATMOSPHERE AND ITS SERVICE TO MAN
and increases the temperature of its surroundings; when
it expands it absorbs heat and lowers the temperature of its
surroundings.
The greater the pressure on a liquid surface, the higher
is the boiling point ; the lower the pressure, the lower the
boiling point. This principle, along with the principle that
a substance absorbs heat as it changes from a liquid to a
gaseous state, underlies the operation of cold storage and
ice-manufacturing plants.
The barometer is an instrument for measuring atmos-
pheric pressure. Since atmospheric pressure decreases with
altitude, a barometer may be used to measure altitude.
QUESTIONS
What are the characteristics and principal uses of the three most
abundant gases in the atmosphere ?
What experiences have you ever had which show that hot air
will hold more moisture than cold air?
How have you ever seen cooling by evaporation used ?
In what ways does the moisture in the atmosphere affect bodily
comfort ?
How can it be shown that the air has weight and exerts pressure ?
What effect has heat upon the weight and volume of the atmos-
phere ?
Suggest several methods for properly ventilating a house.
What effect has pressure upon the weight and volume of air?
Explain the construction of three machines which make use of
atmospheric pressure.
In what way do compression and expansion affect the tempera-
ture of a gas ?
How are the boiling points of liquids affected by pressure?
What practical uses are made of this principle ?
How is ice manufactured?
How do the two kinds of barometers ordinarily used differ in
construction ?
CHAPTER VI
THE WATERS OF THE EAETH
Importance of Water. — Water is found to some extent
everywhere on the earth's surface. It is necessary to the
life of all plants and animals and makes up a large part of
their weight. Man may live without food for a few weeks
but cannot live more than a few days without water. The
earth has been likened by some writers to a water engine,
since water has played such an important part in its history.
Composition of Water. — Experiment 56.— (Teacher's Experi-
ment.)— Place a small handful of zinc scraps in a strong wide-
mouthed bottle. Fit the
bottle with a two-holed rub-
ber stopper having a thistle
tube extending through one
hole and a bent delivery
tube through the other.
The thistle tube should
reach nearly to the bottom
of the bottle. Connect the
delivery tube with the shelf
of a pneumatic trough by a FIQUBE 71
rubber tube. Have several
inverted 8-oz., wide-mouthed bottles filled with water on the shelf
of the trough. (Figure 71.) Pour enough water through the
thistle tube to partly cover the zinc and then pour on commercial
hydrochloric acid or sulphuric acid diluted 1 to 10.
Chemical action will take place between the zinc and the acid
135
136 THE WATERS OF THE EARTH
and hydrogen will be freed. Allow the gas to escape for several
minutes, so as to rid the generating bottle of the air in it. Collect
several bottles full of the hydrogen. Keep the bottles inverted.
Examine the hydrogen in one of the bottles. Has it color or odor ?
Holding the mouth downward thrust a lighted splinter into an-
other bottle. The splinter does not continue to burn in this gas
but the gas itself burns. Place another bottle mouth up on the
table and allow it to stand for several minutes. Insert a lighted
splinter. Why is not the hydrogen still present ?
Draw out a glass tube so that the bore will be about as large as
the point of a pencil and insert it in the rubber delivery tube. Pour
more acid into the bottle and after this has been working for several
minutes touch a lighted match to the glass tip of the rubber delivery
tube. A jet of burning hydrogen will be formed. Hold a cold, dry
beaker over this burning jet. Water drops will collect in the beaker.
The hydrogen is combining with the oxygen of the air and water is
being formed.
Pure water is a colorless, odorless, tasteless liquid. In
Experiment 15 we decomposed water by the electric current
and found it to be composed of two gases, hydrogen and
oxygen. In Experiment 56 we burned hydrogen, thus
uniting it chemically with the oxygen of the air and forming
water. Oxygen we have studied. Hydrogen is a colorless,
odorless, transparent gas, the lightest of all known sub-
stances. It must be handled carefully, because if it is mixed
with oxygen and the mixture is ignited, a violent explosion
results.
Effects of Varying Temperatures on Water. — We have
learned that water evaporates at any temperature and in so
doing always absorbs heat from its surroundings. When it
condenses it gives out the heat absorbed during evaporation.
When water at ordinary temperatures is heated it expands
until it reaches the boiling point. At this temperature,
the change of water from liquid to vapor goes on most
EFFECT OF VARYING TEMPERATURES ON WATER 137
rapidly, and the change of state increases its volume more
than 1700 times. It is this stupendous pressure of rapidly
generating water- vapor that is " harnessed " in the steam
engine. This is one of the most marvelous manifestations
of the energy of heat.
Experiment 57. — Fill a flask of about 500 cc. with water. Press
into the mouth of the flask a rubber stopper through which a glass
tube about 30 cm. long extends. The tube should be open at both
ends and should not extend into the flask below the bottom of the
cork. When the cork is pressed in, the water will be forced up
into the tube for several centimeters. See that the
cork is tight and that there are no bubbles of air in the
flask or tube.
Now place the flask for fifteen or twenty minutes in
a mixture of ice and water (Figure 72) and carefully
mark with a rubber band the point at which the water
in the tube comes to rest. Take the flask out of the
freezing mixture and notice immediately whether the
water in the tube rises or falls. Continue for five or FIGURE 72
ten minutes to notice the action of the water in the
tube. The volume of the water is not the least when it is at the
temperature of melting ice, 32° F., but when it is a little above
this temperature.
Experiment 58. — Put a piece of ice in water. What part of its
volume sinks below the surface of the water ? Is it heavier or lighter
than water? From Experiment 32 do you conclude that cold
water is heavier or lighter than warm water?
When water at ordinary temperatures is cooled it contracts
and grows denser. It continues to do this until the whole
body of water reaches a temperature of about 4° C. Here
a remarkable change takes place ; for as water is cooled below
this point it expands. This expansion goes on until the
liquid turns to solid at 0° C.
At the moment water solidifies into ice, it expands with
138 THE WATERS OF THE EARTH
such tremendous force that it exerts a pressure of more than
100 tons to the square foot. No wonder it bursts water
pipes, splits rocks and concrete sidewalks, and heaves the
foundations of buildings that have not been laid below
" frost line." After ice has once formed, it again begins
to contract as the temperature is lowered, but it never
reaches the density of water. i
It can easily be seen why any river or lake or other
body of water freezes from the top down. Since water at
the freezing point is less dense and therefore
lighter than slightly warmer water, it remains
at the surface, where it freezes. Ice is even
BOMB BURST lighter than water at the freezing point, and
BY FREEZING so ft floats. As soon as ice has formed over
the surface, it acts as a blanket, allowing the
heat to escape only very slowly from the water underneath.
Thus the ice increases in thickness so slowly that spring
comes before a deep body of water can freeze to the bottom ;
and so fish and other forms of water life never become
chilled below freezing nor suffer serious inconvenience.
Ability of Water to Absorb Heat. — We have already
learned that it takes more heat to raise a given mass of
water one degree of temperature than to cause a like in-
crease in temperature in an equal mass of almost any other
substance. This was shown in Experiment 29. When
water cools, it gives out the heat it took up when its tempera-
ture was raised. A pound of water in cooling one degree
gives out about as much heat as a pound of iron in cooling
nine degrees. It is for this reason that hot-water furnaces
are so efficient, that hot-water bags are used to keep people
warm, and that farmers sometimes in winter carry down
WATER AS A SOLVENT 139
tubs of water to keep their cellars above the freezing point.
For the same reason orange groves are often irrigated when
a heavy frost threatens.
This capacity for holding heat makes bodies of water warm
up slowly in the summer and cool off slowly as winter
approaches. If we bear in mind that practically the
entire mass of a body of water must reach a uniform tem-
perature of 4° C. before it begins to freeze at the surface,
this slowness of water to change temperature will explain
why large bodies of water so seldom freeze except
around the shallow edges.
Water as a Solvent. — Experiment 59. — Put a
little salt into water in a clean beaker or drinking glass,
and stir. The solid entirely disappears. Taste the
water. Has the salt affected the water in any way?
Pour out three fourths of the water and taste again.
Is there any difference between the saltiness of the
upper portion and the lower portion of the water?
Experiment 60. — (Teacher's Experiment.) — Fill a
tall bottle with water colored with blue litmus. By JPIQURE 73
means of a long thistle tube, slowly pour a little
sulphuric acid into the bottom of the bottle. (Figure 73.) Allow
the bottle to stand undisturbed and note the gradual change in
color of the litmus, showing that the heavier acid is mixing, or
diffusing, upward through the water.
Experiments 59 and 60 show that when substances are
dissolved in water they tend to mix thoroughly with the
water and to form a uniform solution. When we mix
water, lemon juice, and sugar together to make lemonade,
the solution has a uniform taste throughout. Neither the
solid nor the liquid tend to separate out of the solution
nor to accumulate in any one part of it. As a result
of this characteristic of solutions, the water of the whole
140 THE WATERS OF THE EARTH
ocean from top to bottom is practically uniform in
composition.
Water is the greatest of all solvents. It dissolves to a
greater or less extent almost all substances with which it
comes in contact. There are, however, substances which it
dissolves but slightly if at all. When it is necessary to get
these substances into solution, other solvents must be used.
MONTEZUMA'S WELL
A famous water hole due to the dissolving power of water on rock-
forming substances.
Gasoline, for example, dissolves grease ; turpentine dissolves
fresh paint, and alcohol dissolves grass stain.
Experiment 61. — Fill a small beaker with fresh water. Heat it
slowly. Bubbles collect on the bottom and sides. When the
water becomes cold these bubbles do not disappear immediately.
If these were bubbles of water vapor, they would condense to water
when the temperature was lowered. What are they? Where
did they come from ?
We have learned that all air has water vapor diffused
through it. Experiment 61 showed that there was also
FREEZING MIXTURES 141
air in water. All water exposed to air has air dissolved in
it. It is upon this air in solution that fishes depend for the
oxygen they need. But while air may hold moisture, and
water may hold air, Experiments 37 and 61 show an impor-
tant point of difference between the capacity of air for water
and of water for air. We learned that when air is heated
it is capable of holding more water vapor. But when
water is heated, it is capable of holding less air.
Experiment 62. — Stir salt, a little at a time, into a test tube of
water which is no warmer than the temperature of the room.
Gradually increase the salt until the water will absorb no more,
and a little of the salt settles at the bottom of the test tube. Now
heat the solution. What happens to the salt at the bottom of
the test tube? Set the test tube containing the solution aside
to cool. Does any of the salt reappear in solid form ?
If we put as much of a solid substance into a liquid as the
liquid will dissolve, we have a saturated solution. If any
more of the solid is added, it will remain undissolved.
As the temperature of water increases, it can hold more
solid matter in solution. If a liquid at a certain tempera-
ture is saturated with a solid and then is reduced to a
lower temperature, it will, under ordinary circumstances,
deposit some of the solid. What similar thing happens in
the atmosphere ?
Freezing Mixtures.— Experiment 63. — Place some chopped
ice in a beaker, and test the temperature. Add a generous amount
of salt and test the temperature again. Has there been a fall of
temperature ?
Salt and some other substances tend to absorb water and
to form a solution whenever it is possible. On a damp day
salt sticks in the salt-shaker. This simply indicates that
salt has absorbed moisture from the atmosphere.
142 THE WATERS OF THE EARTH
It is found that when salt or any other solid is in solution
in water, more heat is required to boil the solution and a
lower temperature to freeze it than are required by pure
water. A saturated salt solution freezes only at -22°C.
(-7°F.) although pure water freezes at 0° C. The freezing
point of a salt solution may, therefore, be anywhere from
slightly below 0° C. to - 22° C., dependent upon the strength
of the solution. Salt placed directly upon ice will cause the
ice to melt and form a solution if the temperature is above
-22° C. This explains why salt may be used successfully
to melt ice on porch steps, sidewalks, and car-track switches.
When ice is placed in salt water it takes from its surround-
ings the heat necessary to change it from the solid to the
liquid state and continues to do this until the freezing point
of the solution is reached. It thus happens that the tem-
perature of such a solution may become much lower than the
freezing point of water and yet the solution remain unfrozen.
Most substances placed in such a solution become quickly
frozen. A solution of this kind is used -in freezing ice-cream.
About three parts of snow or ice to one part of salt are the
best proportions to use.
Substances in Suspension and in Solution in Water. —
Experiment 64.— Into a glass of clear water stir a half teaspoonful
of sand and fine dust. Cover the glass and set it aside. After
an hour or so examine the glass and see if any of the sand and
dust has settled to the bottom. If so, stir it up again. What
happens?
It was found in Experiment 64 that water is able to hold
solids in suspension and that the finer the solid particles
the longer they stay suspended. It was also found that
when the water was in motion (stirred) it held more and
iarger particles.
SUSPENSION AND SOLUTION
143
SETTLING BASINS OF THE ST. Louis WATER PLANT
Muddy river water is pumped into these basins and is allowed to stand
until it loses its heavier sediment (Experiment 64). The combined
capacity of these basins is 245,000,000 gallons.
Experiment 66. — Add some salt to the contents of the glass
used in the preceding experiment. Arrange a glass funnel with a
filter paper in it, as shown in Figure 74. Pour the contents of the
glass into the funnel and collect the water
that runs through the filter paper. Do the
sand and dust run through? Put a little of
the filtered water in a watch crystal or in a
shallow vessel and allow it to evaporate. Did
the salt in solution come through the filter
paper?
Filters of all kinds are used to remove
suspended materials from water ; but as
was shown in Experiment 65, the sub- FIGURE 74
144
THE WATERS OF THE EARTH
stances in solution cannot be removed in this way. When
dirty surface water seeps down through thick enough beds
of sand and porous rock, it is cleansed of its dirt; but it
does not lose by this filtering process any of the substances
it held in solution. On the contrary, it may have dissolved
substances from the rocks through which it filtered. In
this way " soft "
rain water may be-
come hard water or
mineral water before
it reaches the surface
again in springs or
wells.
When water has
absorbed carbon di-
oxide it is able to
dissolve limestone
and it then becomes
hard. When water
of this kind is boiled
or evaporated the
carbon dioxide
escapes and the lime
deposits, thus ren-
dering the water soft. Such water is called temporarily
hard water. Boiler and teakettle scale are deposits from
temporarily hard water. Permanently fyard water cannot
be softened by boiling.
Emulsions. — Experiment 66. — Put a few drops of kerosene or
other oil into a test tube half full of water. Since the oil is lighter
than the water it rises to the surface. Shake the test tube vig-
orously. Does the oil mix with the water? Set the test tube
A LIMESTONE CAVE
A cavern dissolved out by water. Hard water
trickling in and evaporating has formed the
columns.
EMULSIONS 145
aside and allow it to stand for a short time. Does the oil remain
mixed with the water?
Put oil and water into another test tube and add finely shaved
soap or a little soap solution Shake the test tube vigorously and
set it aside for a while. Does the oil now rise to the surface ?
When the oil was shaken with the water, it divided into
minute globules scattered through the water, giving the
mixture a milky appearance. The oil soon separated from the
water and floated on top of the water just as it did before
the test tube was shaken. When soap was added and
shaken with the oil and water, the globules remained in
suspension and did not separate from the water when it
was set aside for a while. A suspension of this kind is
called an emulsion.
It is the power of emulsifying oil and grease that makes
soap so useful as a cleansing agent. Water will not dis-
solve grease; but when soap solution is rubbed on oily or
greasy materials, the oil or grease is converted into little
droplets, each surrounded by a film of soap solution. These,
with the little particles of dust and dirt which they contain,
are easily removed by rinsing with water. The natural
oils of the skin accumulate impurities from various sources.
Since water will not dissolve this oil, soap is an essential in
bathing.
If soap is used in hard water, a sticky white substance is
formed which will not dissolve in water. This gummy
substance is a chemical combination of soap with the mineral
salts dissolved in the water. The soap combines chemically
with these mineral salts until all the salts are broken up and
the water is softened. Until enough soap is dissolved to
soften the water, an emulsion will not form. This results in
such a great waste of soap that cheaper substances such
146
THE WATERS OF THE EARTH
as borax or washing soda are often used to soften water for
laundry work. These substances combine chemically with
the mineral salts in solution and leave the water free to
form an emulsion with soap.
Pressure in Water. — Experiment 67.— Tie a piece of thin sheet
rubber (dentist's rubber) tightly over the mouth of a small, short
thistle tube. Attach tightly to the neck of the thistle tube a
flexible rubber tube about two feet long. Bend a glass tube into
the shape of a U, making one arm slightly longer than the other.
Put colored water into the U-tube until it stands about two inches
high in each arm of the tube. Fasten a meter
stick in a perpendicular position and tie the
U-tube to it so that the long arm lies along the
scale. Attach the open end of the rubber tube
to the short arm of the U-tube. When you
press on the rubber sheet at the mouth of the
thistle tube, the water rises in the long arm of
the U-tube. You have made a simple pressure
gauge. (Figure 75.)
Nearly fill a battery jar with water. Slowly
push the thistle tube down into the water and
notice the action of the column of water in the
U-tube. How does increasing depth affect pres-
sure? Being careful to keep the center of the
rubber diaphragm at the same depth, face it up, down, and side-
ways. Does the pressure in different directions vary at the same
depth? Hold the thistle tube at equal depth in the battery jar
and in a pail or tub of water. Does the greater volume of water in
the pail make any difference in the pressure at the same depth?
Pressure in water varies directly as the depth, and at the
same depth pressure is equal in all directions. At a given
depth the volume of the water makes no difference with the
pressure. The pressure would be no greater in a lake six
inches below the surface than at the same depth in the
battery jar. For that reason, the pressure on a water main
FIGURE 75
PRESSURE IN WATER
147
issuing from the bottom of a standpipe would be just as
great as from a reservoir of great area, provided the depth
of water in each is the same. It follows, therefore, that the
bottom of a standpipe supporting a fifty-foot column of
water would have to be just as strong as the bottom of a
dam holding back the waters of a lake fifty feet deep. Of
course in a heavier liquid than water, pressure would in-
crease more rapidly with the depth ; and in a lighter liquid,
less rapidly.
Another important property of water and of all other
liquids is that they transmit pressure equally in all direc-
tions. If a bottle be com-
pletely filled with water and
pressure be suddenly applied
to the stopper, the trans-
mitted pressure may break
the sides of the bottle. If
the area of the face of the
cork that pressed upon the
surface of the water in the
bottle were one square inch FIGURE 76. — HYDRAULIC PRESS
and the pressure applied to
the cork were twenty-five pounds, then the twenty-five
pounds of pressure on the square inch of water surface
would be conveyed to every square inch of the inner
surface of the bottle.
This property liquids have of transmitting pressure
equally in all directions has many practical applications.
One of the most common is the hydraulic press (Figure 76) .
In this machine a relatively small amount of pressure on
the small piston achieves tremendous results at the large
piston. Suppose, for example, the area of the face of the
148 THE WATERS OF THE EARTH
small piston is one square inch and the area of the face
of the large piston is 100 square inches. If a pressure of 25
pounds were exerted downward on the small piston, an
equal pressure would be exerted upward on every square
inch of the face of the large piston. Thus 25 pounds pres-
sure on the small piston would cause an upward pressure of
2500 pounds on the large piston.
In the operation of this press, the large piston would
rise only one hundredth as far as the small piston descended.
If the small piston descended a foot, the large piston would
rise one hundredth of a foot. In other words, the pressure
on either piston times the distance it travels equals the
pressure on the other piston multiplied by the distance it
travels.
The enormous force that can be exerted by the hydraulic
press is used in baling cotton and paper, in punching holes
through steel plates, in extracting oil from seeds, in lifting
huge machines, and in many other devices where immense
pressure is needed.
Buoyancy of Water. — Experiment 68. — Prepare a block of
wood having dimensions of 6x4x4 cm. Bore a hole in one
end of the block and fill it with sufficient lead so that it will
readily sink in water. Tightly close the hole containing the lead
and dip the block in melted paraffin to make it entirely waterproof.
Carefully measure the block and compute its volume in cubic
centimeters.
Drive a small tack into the center of one of the smaller faces
of the block. Attach a thread to the tack and lower the block
into a cylinder graduated to cubic centimeters. Pour into the
cylinder more- than enough water to cover the block. Read on
the cylinder scale the combined volume of the block and the water.
Pull the block out of the water. Read on the scale the volume of
the water left in the cylinder. Does the difference between the
two readings equal the computed volume of the block?
BUOYANCY OF WATER 149
From this experiment we learn that a body submerged in
water displaces a volume of water equal to its own volume.
A cubic block measuring exactly 96 cubic centimeters
would displace 96 cubic centimeters of water.
Experiment 69. — Attach the block prepared for the previous
experiment to a spring balance with a scale reading in grams, and
weigh it. Lower the block suspended from the scale by a thread
into a vessel of water until it is entirely submerged. Does the
block appear to weigh as much now as when out of water ?
Compare the difference between the weight of the block in air
and its apparent weight in water, with the weight of the water
which the block displaced in the preceding experiment. One cubic
centimeter of water weighs a gram.
From this experiment we learn that a body appears to
lose weight when it is submerged in water and the amount
of weight it loses is exactly equal to the weight of the vol-
ume of water it displaces. If a cubic centimeter of lead is
weighed in water it will be found to weigh one gram less than
in air. In other words the lead is pushed upward, or buoyed
up, by a force exactly equal to the weight
of a like volume of water.
Experiment 70. — If convenient use an " over-
flow can." If not punch a hole near the top of
a, IflVrfffi tin nan. CDrivft thft nnnp.h frrvm the
\
a large tin can. (Drive the punch from the
inside so that the flange will be on the out-
side.) Smear a little vaseline around the inside
and the outside of the hole so that water will
not cling to the tin. Place the can on a box on FIGURE 77
the table and fill with water until the water
begins to run out of the hole. (Figure 77.) Accurately weigh a
block similar to the block used in Experiment 68, but containing
no lead. Weigh also a dry beaker. Place the beaker so that it
will catch all the water overflowing from the hole in the tin can.
Place the block in the can. As soon as water has ceased to run
150
THE WATERS OF THE EARTH
into the beaker, weigh the beaker with the water in it. Subtract the
weight of the dry beaker from the weight of the beaker containing
water, and you will have the weight of the water displaced by the
block of wood. Compare this weight with the weight of the block.
Mark on the block the depth to which it sinks. About how
much of the block was submerged ?
A body floating in water displaces its own weight of water.
Thus if a body is half as dense as water, it will sink half
AN AMERICAN SUBMARINE
U. S. official
its volume ; if one third as dense, it will sink one third its
volume. Representing the density of water by 1, what deci-
mal fraction would represent the approximate density of the
wood in the experiment? The density of any substance as
compared with the density of water is known as the specific
density of the substance. A solid piece of iron is much
denser than water and when submerged displaces much less
than its own weight of water. It therefore sinks. But an
iron dish will float because its volume is so great that it
displaces a weight of water equal to its own weight. If a
hole is made in the dish and water is allowed to enter the
ANIMAL LIFE IN WATER
151
hollow space, the dish begins to sink. The depth to which
it sinks may be regulated by the amount of water admitted.
Submarines are boats so constructed as to be water-tight
even when submerged. Special compartments are provided
to which water can be admitted and from which it can be
driven out. When the commander of a submarine wishes to
submerge his vessel, he gives the order to admit sufficient
water to the compartments to make the submarine heavier
U. S. official
A SUBMARINE SUBMERGING
than an equal volume of water. It therefore sinks. In order
to make the submarine rise, the operators must force water
out of the tanks until the submarine displaces a weight of
water greater than its own weight. It will then rise and
float partly submerged. If just enough water is admitted to
the tanks to make the weight of the submarine equal to the
weight of the water displaced, the submarine can be made to
float at varying depths.
Animal Life in Water. — From previous experiments we
152
THE WATERS OF THE EARTH
have learned some of the chief physical properties of water,
and so perhaps we can understand the different effects that
water has had upon the development and activities of
living things. Some water animals move about easily to
get their food, but others have it brought to them in solution
and so obtain it without muscular effort. The air that they
breathe is in solution and they cannot as easily obtain a
large quantity of it as
can the land animals.
Since the energy of all
animals depends upon
the amount of oxygen
they use in their bodies,
the water animals are
generally less energetic
than the land animals.
Since they also have
such an easy time in
moving or floating about
to get the things they need they have not developed as
high organisms as the land animals.
Ocean Waters. — The oceans which cover almost three
fourths of the earth's surface are the inexhaustible reser-
voirs from which come, directly or indirectly, the waters of
rivers and lakes, of wells and springs, and the moisture of
atmosphere and soil.
Experiment 71. — If ocean water can be obtained, boil down
about a pint of it in an open dish. Taste the residue. What is
the principal constituent of this residue ?
There is probably no water on the surface of the earth
which is absolutely pure. All ordinary water has come in
contact with some substances which it could dissolve.
CORALS
Fixed animals whose food is brought to
them in solution by the ocean currents.
OCEAN WATERS
153
When the river waters run into the sea, they carry with them
whatever they have dissolved from the land. When the
water of the sea evaporates and is borne away, to fall upon
the land again, the dissolved
material is left behind in
the ocean.
Thus the sea has for all
time been receiving soluble
contributions from the land.
It is easy to prove that it
contains salt, for we can
taste it. It must contain "AIRING" AN AQUARIUM
Fishes may die in the still water of an
aquarium for lack of fresh air. The
small stream from the tube stirs up
the tank-water and causes it to
absorb air.
lime, since coral and shell
animals of the sea depend
upon it for the hard parts
of their bodies. There must
be organic food material in it, or else fixed animals like
corals could not get their food. It contains air, for with-
out air fishes could not breathe. These are the principal
substances which we need consider in the study of ocean
water, but the chemist can find many other substances
dissolved in it. There is so much dissolved
material of different kinds in it that the density
of the solution is sufficient to keep ocean water
from freezing until it reaches 28° F., instead of
32° F., the temperature at which fresh water
freezes.
Experiment 72. — Place in a deep dish of fresh
FIGURE 78 water a density hydrometer (Figure 78), or stick
loaded with lead at one end so that it will float up-
right. Mark with a rubber band the depth to which the hydrom-
eter sinks in the water. Now place the hydrometer in sea
154
THE WATERS OF THE EARTH
water and mark the depth to which it sinks. If sea water cannot
be obtained, dissolve in a pint of fresh water about 15 g., or half
an ounce, of salt. This will give the water about the same amount
of dissolved solid material as sea water has. About how much
more of its length does the hydrometer sink in fresh water than
in sea water? Will a piece of ice project more out of salt water
than it would out of fresh water ?
On account of the materials dissolved, sea water weighs
more than fresh water, or has a greater specific density.
Floating bodies therefore have less of their volumes sub-
merged in sea water than in fresh water. A cubic foot of
sea water weighs over 64.25 pounds, whereas a cubic foot
of fresh water weighs only about 62.5 pounds. The specific
densitv of sea water is about 1.03.
Ocean Depths. — The greatest depth thus far found in
the ocean is over six miles. This was found in the Pacific
Ocean near the Philippine
Islands,
depth
3W4 Ft -SEA LEVEL.
The greatest
in the Atlantic
Ocean thus far discov-
ered is a little over five
miles at a point north
of Porto Rico. The
average depth of the sea
is probably about two
and one half miles.
Although the pressure
at the bottom of the
ocean must be tremendous, yet so incompressible is water
that a cubic foot of it weighs but little more at the bottom
of the sea than it does at the top. Thus a body which
readilv sinks will in time reach the bottom, no matter what
MOUNT EVEREST
As it would appear if placed in the
deepest part of the sea.
CONDITIONS 'OF THE OCEAN FLOOR 155
the depth may be. At a depth of two miles the pressure
is over 300 times as much as at the surface of the water;
and here, as we have already found, it is about 15 pounds
to the square inch.
If a bag of air which had a volume of 300 cubic inches
at the surface were sunk in the ocean to a depth of two
miles, it would have a
volume of less than a
cubic inch, and the pres-
sure upon it would be
several tons. It thus
happens that deep sea
fishes when brought to
the surface have the air
in their swimming blad-
ders so expanded that the
bladders are often blown
out of their mouths.
Conditions of the Ocean
Floor. — The ocean floor
is a vast, monotonous,
nearly level expanse whose CRINOID
dreary, slimy, and almost A ^a animal once abundant but now
* f found only in deep oceans.
lifeless surface is enveloped
in never-ending night and is pressed upon by a vast weight
of almost stagnant frigid water. Here and there volcanoes
rise upon it with gradually sloping, featureless cones, and
sometimes a broad, wavelike swell reaches within a mile or
so of the surface. Such a swell extends along the center of
the Atlantic Ocean through Ascension Island and the
Azores.
156 THE WATERS OF THE EARTH
There are no hills and vales, no mountain ranges having
sharp peaks and deep valleys. Gradually rising ridges
and volcanoes, sometimes topped with coral islands, alone
vary the monotony. It is the nether world of gloom and
unaltering sameness. Here the derelicts of ages past, after
their fierce buffeting with wind and wave, have found a quiet,
changeless haven where they may lie undisturbed until
absorbed into the substance4 of the all-enfolding water.
The Carpet of the Ocean Floor. — Near the shore, the
floor of the ocean is covered with sand and mud derived
from the waste of the land. In the deeper sea the cover-
ing is a fine-textured material of animal origin called ooze.
It is composed of the shells of minute animals that live
near the surface.
At a depth of about 3000 fathoms (18,000 feet) these
shells disappear and a reddish clay appears. This clay is
believed to be due to meteoric and volcanic dust and to
the insoluble parts that remain after the calcareous (lime-
like) material of the minute shells has been dissolved in
sinking through the deep water. No layers of this kind
have ever been found on the land, and this is one of the
reasons for believing that the depths of the sea have never
been elevated into dry land, but that what is now deep
ocean has throughout all time been deep ocean.
Temperature of Ocean Waters. — Sea water continues
to contract as it cools until it is of about the freezing tem-
perature of fresh water. Hence cold water near the poles
gradually sinks and creeps under the warmer water of
lower latitudes, maintaining a temperature of 32° to 35°
on the bottom, even at the equator. This steady creep of
cooled surface water along the bottom supplies the animals
WAVES 157
of the deep ocean floor with the air which they must have.
Without it the water at great depths would have its air
exhausted and all life would be destroyed.
At the surface of the ocean the temperature of the water
varies in a general way with the latitude; it is over 80°
at the tropics and about the freezing point at the poles.
Near the poles and near the equator there is very little
variation in the temperature of the surface water during
the year, but in the intermediate latitudes the annual
variation is considerable. Below the surface the effect
of solar heat rapidly diminishes and at a depth of 300 ft.
it is probable that the annual variation in temperature is
nowhere more than 2° F. Below 600 ft. there is probably
no annual change in temperature.
Waves. — Experiment 73. — Take a long, flexible rubber band
or tube and having fastened one end, stretch it somewhat. Now
strike down on it near one end with a small stick. A wavelike
motion will be seen to travel from end to end of the band. It is
evident that the particles of rubber do not enter into the lateral
movement, but that they simply move up and down, whereas the
wave movement proceeds along the band. A piece of paper folded
and placed lightly upon the band will move up and down but not
along the band. Thus, wave motion does not necessitate lateral
movement of the particles taking part in the wave.
When the wind blows over water, it throws the surface
into motion and produces waves. The highest part of the
wave is called the crest and the lowest part the trough.
Trough and crest move along rapidly over the surface of
the water. The particles of the water themselves, how-
ever, move somewhat like those in the rubber band. That
the water itself does not move with the wave can be seen
when a floating bottle is observed. It moves up and down
158 ,THE WATERS OF THE EARTH
but does not move forward. If the water moved along
with the waves, it would be next to impossible to propel a
boat against the direction of the wave movement.
That it is possible to generate wave movement without
the particles themselves moving along with the wave is
seen when a field of grain is bending before a gentle wind.
The troughs and crests move one after the other across the
OCEAN WAVES
field but the heads of grain simply vibrate back and forth.
The crest of a water wave, however, is often blown forward
by the wind and thus a drift in the direction of the wind is
established at the surface.
When great waves are raised by the wind at sea, there
is danger that the mighty crests may be blown forward
and engulf a ship. To calm the waves ships sometimes
pour " oil on the troubled waters." The oil spreads out
in a thin film over the water and forms a " slick " which
WAVES AS DESTROYERS AND BUILDERS 159
prevents the wind from getting sufficient hold upon the
water to topple over the crests, and thus the danger of being
swamped is averted. It has been found that oil will spread
out even in the direction of the severest wind.
Although sometimes waves are spoken of as " mountain
high," it rarely happens that the height from trough to
crest is over 50 ft. The movement of the waves stirs up
the water and enables it more freely to absorb the air which
is so necessary for the existence of water animals.
FINGAL'S CAVE
Waves as Destroyers and Builders. — Wherever the
waves strike on an unprotected shore, they wear it away.
The rapidity of the cutting and the forms carved depend upon
the strength of the waves and the kind of shore. Wherever
there is a point of weakness along the shore, there the waves
cut back more rapidly. The harder parts stand out sharply
160
THE WATERS OF THE EARTH
as points and promontories. In some cases the waves cut
back so rapidly on lofty coasts that high cliffs are formed.
If the material of the coast does not readily break off
when undercut by the waves, a sea cave may be formed.
Such is the well-known Fingal's Cave on an island off the
coast of Scotland
where the structure
of one of the igneous
rock layers allows the
waves to quarry it
comparatively easily.
If a coast stays at
the same elevation
long enough, or if its
material is easily
eroded, large areas
of what was for-
merly dry land may
be cut away and
brought under the
sea.
In 1399 Henry of
A LAKE BEACH FORMED BY A STREAM AND
WAVE ACTION
A year after this picture was taken a landslide
caused a wave which swept away the entire
beach and village.
Lancaster, afterward
Henry IV of Eng-
land, returned from
his exile and landed
at Ravenspur, an important town in Yorkshire, to begin
his fight for the crown. A person disembarking at the
same place to-day would be so far from shore that
he would need to be a sturdy swimmer to reach the
beach. The entire area of the ancient town has been
cut away by the waves and now lies under the sea. This
WAVES AS DESTROYERS AND BUILDERS 161
is an example of what has occurred in many seacoast
regions.
Unless the material pillaged from the land by the waves
falls into too deep water, it is buffeted about by them and
broken and worn into small pieces. These are then borne
along by the shore currents until they find lodgment in
some protected place where they can accumulate. When
sufficient material has been accumulated, the storm waves
A SAND SPIT, FORMED BY WAVES AND CURRENTS
and the wind sweep some of it above sea level and fringe
the water's edge with a border of water- worn sand and
pebbles. These accumulations of shore drift are called
beaches.
Currents moving loose material with them sometimes
form it injto bars which tie islands to the mainland or extend
into the sea free ends, forming what are called spits. A
famous example of a land-tied island is that of the great Eng-
lish fortress at Gibraltar. Although now a promontory, it
162 THE WATERS OF THE EARTH
was once an island detached from the coast of Spain. Shift-
ing sand bars, especially if covered with water, are exceed-
ingly dangerous to vessels, and coasts where these are abun-
dant need especial protection by lighthouses and life-saving
stations. The greatest Mediterranean port of France during
the thirteenth century, Aigues-Mortes, has been closed in
by sand bars so that there is no longer access to the sea and
only the relics of the former great city now exist. Thus
have the moving sea-sands overthrown the plans of men.
Ocean Currents. — The ocean is a region of never-ceasing
motion. At considerable depths its motion is very slow,
but near the surface, where the prevailing winds can affect
it, the movement is considerable. Circulating around each
ocean there is a continuous drift of surface water extending
to a depth of from 300 to 600 feet and varying in rate from
a few miles up to fifty or more miles a day. In fact these
rotating currents are the chief natural basis for the divi-
sion of the oceanic area into six oceans, as our geographies
generally divide them.
These currents circulate in the northern hemisphere in
the direction in which the hands of a watch move and in
the .southern hemisphere in the opposite direction. In
the centers of these rotating areas the water is nearly motion-
less and here are often found great masses of floating sea-
weed filled with a great variety of small animals. These
accumulations of seaweed are called sargasso seas.
The temperature of winds blowing from the sea is modi-
fied by these currents and greatly affects the habitability
of the earth for man. The editor of the National Geographic
Magazine makes the striking statement that " the Gulf
Stream carries enough heat toward Europe every twenty-
164
THE WATERS OF THE EARTH
four hours to melt a mass of iron as large as Mount Wash-
ington. Hammerfest at 71° north is a flourishing seaport,
but there are no important settlements above 50° on the
western side of the Atlantic. Alaska, the prevailing winds
of which are warmed by blowing over the warm ocean,
is a region which promises much for human habitation,
while the region on the opposite side of the Pacific must
remain almost destitute of human inhabitants. It should
be noted that the
effect of the warm
ocean waters would
be slight, except
along the coast, were
it not for the air
movements.
Tides. — Prob-
ably the first thing
that impresses us
on visiting the sea-
shore is the regular
rising and falling of
the water each day.
These movements of the water are called tides. If we
observe the tides for a few days, we find that there are two
high and two low tides each day. As the tidal current
comes in from the open ocean and the water rises, it is
called flood tide, a"nd as it runs out or falls, ebb tide. When
the tides change from flood to ebb or ebb to flood, there is
a brief period of " slack water/'
If we observe closely, we shall see that the corresponding
tides are nearly an hour later each day than they were
HIGH TIDE IN NOVA SCOTIA
TIDES
165
the day before, and that the time required for the comple-
tion of two high and two low tides is nearly 25 hours. Con-
tinued observation will show, as Julius Csesar stated many
centuries ago, that there is apparently a relation between
the phases of the moon and the height of the tides. The
greatest rise and fall of the water will be found to occur
about the time of full and new moon.
It has been found that the position of the sun, as well as
that of the moon,
affects the height of
the tide. If the
earth, moon, and
sun lie in nearly
the same line, the
tidal range is great-
est. This is called
spring tide. When
the sun and moon
act at right angles
upon the earth, the
tidal range is least
and this is called
neap tide. The tidal
undulations have been proved by astronomers to be due to
the rotation of the earth and the gravitational attraction of
the sun and moon upon its water envelope. The moon is
much more effective because it is nearer.
The tidal current as it sweeps between islands often
forms eddies and whirlpools which make navigation very
dangerous. An example of this is found at Hell Gate,
New York, and at the famous Maelstrom off the coast of
Norway. On the other hand, in flat countries where the
Low TIDE AT THE SAME PLACE
166 THE WATERS OF THE EARTH
rivers are shallow, ports which could not otherwise be
reached are made accessible to ships of considerable burden
at the time of high tide. At these places the time of leav-
ing or making port changes each day with the time of high
tide. A striking example of this is the port of Antwerp.
The tidal currents are also continually changing the water
in bays and harbors and thus keeping them from becoming
stagnant and foul. They also bring food to many forms of
inshore life which have but little or no power of movement,
such, as clams and other shellfish. The ebb of the tide
exposes some of these and gives man a chance to acquire
them readily for food.
Man and the Ocean. — At first thought it would seem
better for the life of the world if the proportion of land and
water were reversed. Yet when we consider that almost
barren wastes constitute many continental interiors and that
plenty of rainfall is necessary to make land habitable,
the utility of the great water surfaces becomes apparent.
From the evaporation of the ocean surface comes nearly
all the water which supplies man, land animals, and plants.
It is not only true that all streams eventually run to the
sea but it is also true that all their water comes from the
sea.- Other things being equal, the smaller the surface for
evaporation the less the water supplied to the land. Be-
sides supplying the land with water, the ocean has a great
effect on its climate.
The animals of the sea also furnish food for thousands.
The value of the world's fishery products is nearly one half
billion dollars a year. A large part of the earth's population
is now, and always has been, located not far from the shore
of the ocean.
SUMMARY 167
In early times before the advent of railways almost all
commerce was carried on over the sea. Even now this is
the cheaper way of transportation. Modern methods of
conveyance have enabled man to live with comfort at a
considerable distance from the ocean, but the dry interiors
of continents still remain sparsely inhabited. All com-
mercial nations must have an outlet to the sea and to ob-
tain it much blood and treasure have often been spent.
SUMMARY
The earth has been called a water engine since water has
played such an important part in its history. Pure water
is a colorless, odorless, tasteless liquid, composed of two
gases, hydrogen and oxygen. Water may evaporate at
any temperature, but evaporation goes on most rapidly at
the boiling point. As water above 4° C. increases in
temperature, it increases in volume. When water changes
from a liquid to a gas, its volume increases more than 1700
times. Water in cooling grows denser until it reaches about
4° C. It then begins to expand and continues to do so until
it freezes at 0° C. When it freezes it exerts a pressure of
more than 100 tons to the square foot. The entire mass of
a body of water must reach a temperature of about 4° C.
before it begins to freeze at the surface.
Water is the greatest of all solvents but it does not dissolve
every substance. The higher the temperature of water, the
less air but the more solid matter it will hold in solution. A
mixture of ice, salt and water is called a freezing mixture be-
cause the solution attains a temperature lower than that of
melting ice. All solutions freeze at a lower temperature than
that at which pure water freezes. Water may also hold sub-
stances in suspension. The greater the 'movement of water
168 THE WATERS OF THE EARTH
the more it will hold suspended in it. Oils and fats, which do
not dissolve in water, may be suspended in water by emulsion.
Water, like air, exerts pressure, the amount of which de-
pends on the depth of the water. The pressure at any given
depth is equal in all directions. Water also transmits
pressure equally in all directions.
A submerged body displaces a volume of water equal to
its own volume, and loses weight exactly equal to the weight
of the water displaced. If a body weighs less than an equal
volume of water it floats ; if more, it sinks.
Animals that live in water obtain the oxygen they need
from air in solution. Since an animal's energy depends
largely on the amount of oxygen it consumes, water animals
are generally less energetic than land animals.
The oceans are the earth's water reservoirs. The seas have
for all time been receiving soluble contributions from the land.
When water evaporates, the dissolved substances are left
behind. Thus sea water is denser than fresh water and
freezes at a lower temperature. The greatest depth thus
far found in the ocean is more than six miles. At the depth
of two miles, the pressure is more than 300 times as much
as at the surface. The ocean floor is an almost level expanse
with only occasional volcanoes or gradually sloping swells.
Near the shore mud and sand washed from the land cover
the ocean floor. In deeper water the ocean floor is covered
with ooze, and below 18,000 feet with a peculiar reddish
clay, not found elsewhere. At the surface, the temperature
of ocean waters varies in general with the latitude. Below
the surface, the effect of solar heat diminishes rapidly.
Below 600 feet there is probably no annual change in tem-
perature, and at the bottom a steady temperature of 32°
to 35° F. is maintained.
QUESTIONS 169
Waves are caused by up and down, not by lateral, move-
ment of the water affected. The power of waves and tides
to cause erosion results in their acting as destroyers of
unprotected shores. The solid matter eroded and carried in
suspension is often deposited at quieter places along shore.
Thus waves and tides may also act as builders. Ocean
currents are drifts of surface water, some of which, due to
the winds blowing over them, have very important effects
on the climate of adjoining lands. Tides are movements of
the water envelope of the earth caused by the rotation of
the earth and the gravitational attraction of the sun and the
moon — chiefly the latter. Oceans furnish the water which
supports land life, food for thousands of people, and path-
ways of commerce for all nations.
QUESTIONS
What is the composition and what are the most striking charac-
teristics of water?
Why does a freezing mixture freeze substances placed in it and
yet itself remain unfrozen?
What is the difference between an emulsion and a solution?
Why is soap used in cleaning?
Explain the principle of the hydraulic press.
How could a piece of lead be made to float in water? Why?
Mention some ways in which ocean water differs from distilled
water.
Waves and currents are both primarily due to winds. How
do they differ in action and effect?
What are tides and their cause?
Of what advantage is the ocean to man ?
CHAPTER VII
THE WOKK OP SUNNING WATER
The Sphere of Activity of Rain. — When rain falls upon
the ground, it may do one of three things. It may evapo-
rate immediately from the surface and return to the air ;
or it may run rapidly off the surface and quickly join
the streams and rivers which bear it to its final goal, the
sea; or it may sink into the ground. In this last case
part of it returns gradually through capillary action to
the surface, where it is again evaporated; part finds its
way into springs; and part sinks deep into the soil and
rock.
Experiment 74. — (Teacher's Experiment.) — Attaclvone end of a
rubber tube to a faucet in a sink. In the other end of the rubber
tube insert a glass tube
drawn out to a point, so
that when the faucet is
opened the water will issue
from the glass tube in a fine
FIGURE 79 stream. Arrange to play
this stream into the concave
surface of a spoon so that the reflected and widened spray will fall
over about a square foot of surface. (Figure 79.)
Take a long, shallow, flat-bottomed pan and punch a row of holes
in one end of it, a little above the bottom. At the other end, and
covering about two thirds of the bottom of the dish, arrange several
thin, irregular layers of fine sand, salt, fine clay, coal dust, or
other fine materials. Tilt the pan slightly so that the fine materials
170
LAKES 171
may occupy the upper two thirds of a gentle slope and the bare
surface of the pan with the drainage holes, the lower one third.
Allow the spray from
the spoon to play over the
layers in the dish for some
time. Tiny rivulets will
grow in the layered sur-
face, gradually deepening
and extending their valleys, FIGURE 80
and more and more thor-
oughly dissecting the surface. Deltas will be formed in the still
water in the lower part of the pan, and many of the erosion
phenomena of a stratified, slightly elevated region will appear.
(Figure 80.)
Run-off. — The rain that falls upon the land and neither
evaporates nor sinks into the surface runs off as fast as it
can toward the sea. It is joined sooner or later by the
water from the springs and by the rest of the underground
drainage. Sometimes the journey is long and there are many
stops and delays in lakes and pools; sometimes the course
is quite direct and quickly traveled. The run-off most
profoundly affects the earth's surface. Gullies and valleys
are cut, depressions are filled ; in fact, running water is the
chief tool which has carved the features of the earth. It has
had a long time to act and it has kept unremittingly busy,
so that the results of its action appear now in our varied
landscape.
Lakes. — The water which runs off the surface first fills
the depressions. As soon as these are filled, it runs over the
lowest part of their rims and starts again on its course to
the greatest of all depressions, the sea. If depressions of
considerable size become filled with water, we call them
lakes.
172 THE WORK OF RUNNING WATER
The streams that flow into lakes are continually bring-
ing down the sand and mud they have gathered in their
course, and are thus filling up the lakes.
The outlet to a lake tends to wear away its bed, but it
does this slowly, as it has little sediment with which to scour.
Thus lakes are being constantly filled and drained, and so
are comparatively short-lived features of the earth.
Lakes are very important features to man. They filter
river water so that rivers emerging from lakes are clear.
Where the Rhone enters Lake Geneva, it is turbid and full
of silt, but when it emerges, it is clear and without sedi-
ment. Lakes also act as reservoirs for the water that pours
into them at the time of freshets. Rivers emerging from
lakes of considerable size vary little in the height of their
water at different seasons of the year. They are without
floods. The St. Lawrence illustrates this. On the other
hand the Ohio, with its frequent and terribly destructive
floods, shows the effect of unrestrained run-off.
In some regions the rainfall is so small that the depres-
sions never fill up sufficiently to overflow their rims. The
water is evaporated from the surface as fast as it runs
into the lake. Thus all the salt and other soluble sub-
stances which have been extracted from the land and brought
into the lake by the rivers remain there, since only pure
water is evaporated. In this way lakes without outlet
become salt. Great Salt Lake in Utah is an example of
this. Some salt lakes, like the Caspian Sea, were probably
once a part of the ocean, so that they have always been
salt.
As time goes on, more salt is brought to these lakes with-
out outlets, and they become more and more salty. Great
Salt Lake has something like 14 or 15 per cent of solid
LAKES
173
material in its water, the Caspian Sea about 13 per cent,
and the Dead Sea about 25 per cent. An effort to swim
in these waters gives one an exceedingly queer sensation.
The buoyancy is so great that a large part of the body is
out of water, and one finds oneself bobbing around like a
cork. When boats pass from the fresh water of the Volga
MINING SALT IN THE DRIED UP SALTON LAKE, CALIFORNIA
River to the salt water of the Caspian Sea, their hulls grad-
ually rise perceptibly higher.
Where bodies of water like these have dried up, their old
beds are exposed as almost level plains. These become
exceedingly fertile under irrigation as soon as the salts are
dissolved and drained out of the soil. Fine examples of this
are the fruitful plains near Salt Lake City and in Imperial
Valley, California.
174 THE WORK OF RUNNING WATER
Depressions that are very shallow and are largely filled
with vegetable growths are called swamps.
The Power of Running Water. — Eunning water has the
power of carrying solid materials. If it is moving slowly,
this power is not great; if moving swiftly and in great
volume, it is tremendous. The carrying power of a stream
LAKE DRUMMOND
A lake in Dismal Swamp, Virginia, which is being filled by vegetable
growth.
increases very rapidly if its velocity is increased. A stream
having its velocity doubled will carry several times as
much material as before. Thus it happens that water
running over a surface sweeps loose material with it, the
amount varying with the rapidity and volume of the flow-
ing water.
As this loose material sweeps over solid surfaces, it cuts
them down. Thus flowing water is continually wearing
DIVIDES 175
down and sweeping away the surface over which it moves.
This sort of work is called water erosion.
When running water is concentrated into a stream, the
work of erosion is also concentrated and the wearing down
of the stream bed becomes comparatively rapid. This
cutting down goes on irregularly, being greatest at time of
flood and least when the flow is slight.
GULLIES BEING CUT BY RUNNING WATER
Divides. — If we carefully observe the drainage of a
region, we find that the areas from which different streams
gather their water are usually so distinctly separated from
one another that a line could be drawn so that wherever
water falls the rivulets on one side would flow into one
stream and on the other side into another. Such a line of
the highest land between the drainage areas of neighboring
streams is called a divide. The line may be very distinctly
marked, as on mountain ridges, or it may be difficult to
determine, as in a flat country, but if the drainage is well
established, it will be apparent.
176 THE WORK OF RUNNING WATER
If the drainage is not well established, areas may be
found which at one time drain in one direction and at an-
other time in another.
Thousands of years ago, during the Glacial Period,
Lake Michigan drained into the Mississippi system. In
recent geological times it has drained into the St. Lawrence
system. Chicago, by dredging a drainage canal along an
DIVIDES BETWEEN STREAMS
The ridge in the center of the picture separates two streams flowing in
opposite directions.
ancient outlet, has restored part of the drainage of the lake
to the Mississippi system.
Divides are irregular in their height, so that roads and
railways in passing from one drainage basin to another
usually seek out the lowest part of the divide. In mountain
regions these low places are called passes.
River Development. — The rain which falls upon a
flat country runs off very slowly, a large part of it soaking
RIVER DEVELOPMENT
177
into the ground. Pools and lakes are formed in the in-
closed basins? and sluggish streams with irregular little
crooks, which show that the streams have hardly decided
where they want to go, wander in the slight depressions
NIAGARA FALLS
down the gentle slopes and unite with other streams
here and there until a river of ever increasing size is
formed.
In some places the streams flow through lakes where
they deposit their sediment, thus filling the lake basins.
Here and there they pass over hard layers of rock which
178 THE WORK OF RUNNING WATER
hold them up in falls and rapids. These they at once
begin to smooth down. Rivers of this kind may well be
called young, as their life work is just beginning. The
Red River of the North, with its shallow, narrow valley
and tortuous course, and the Niagara River, with its lakes
and falls, are examples of young rivers.
STREAM WORKING BACK INTO AN UNDISSECTED AREA
Where the slope of the newly exposed surface is consid-
erable, the streams flow much more rapidly and develop
their courses more quickly. The small irregularities are
sooner straightened and the trough deepened, thus form-
ing side slopes down which run little rivulets which in
time form side streams. The heads of these, like the heads
of the larger streams, are constantly working back into the
undissected area. Gradually the side streams develop side
RIVER DEVELOPMENT
179
streams of their own, and almost the whole surface is covered
with a network of streams.
As the work of erosion goes on and the streams deepen
their valleys, only a few imperfectly drained remnants of
the former flat surface are left here and there. These lie
YELLOWSTONE RIVER
A river flowing in a deep narrow trough.
between the larger streams in places which the side streams
have not as yet been able to reach. Almost the entire
surface is so intricately carved into drainage lines that
wherever water falls it immediately finds a downward slop-
ing surface. The main stream by this time has probably
smoothed out most of its falls and rapids and has developed
long, smooth stretches.
180
THE WORK OF RUNNING WATER
Here it is no longer cutting down its trough, but has
only sufficient slope to enable it to bear along its load of
waste. It here deposits upon its valley floor about as
much as it takes away. In this part of its course a river
is said to be graded. The longer a river flows undisturbed
by any deformation of its valley, the fewer falls and rapids
it will leave and the longer will be its graded stretches.
The Missouri River near Marshall, Missouri, is an excellent
example of a graded river.
Sometimes a stream becomes so overloaded with detritus,
which it has acquired in a steeper part of its extent, or
PLATTE RIVER
which has been brought to it by tributaries, that it is con-
tinually being forced to deposit some of its load. Thus it
silts up its course and flows in a network of interlacing
shallow channels. The Platte as it crosses the plains of
Nebraska is an example of such an overloaded river.
When a stream swings around a curve, the swiftest part
of the current is on the outside of the curve and the slowest
on the inside. A river that is carrying about all the load
that it can, on passing around a curve, is able in its outer
part to carry more than before and cuts into the bank,
while on its inner part it flows less rapidly and is able to
RIVER DEVELOPMENT* 181
carry less, thus being forced to drop some of its load. As
a river flows along its graded stretches, eroding in some
places and filling in others, it broadens its valley floor,
leaving at the border of its channel a low plain which in
time of flood may be covered with water.
These plains are very fertile and are usually called
" bottom lands " by the farmers. They are often unhealthy
RIVER EROSION
Cutting down the outer side of the curve and depositing on the inner.
because of floods and poor drainage. Where the water in
the river rises rapidly and to a considerable height, it is
dangerous to inhabit these plains. But sometimes these
plains are so fertile that they are densely populated, as
the plain of the Ganges. Such a river-made plain is called
a flood plain.
If a river once begins to swing on its valley floor, it con-
tinues to do so, since whenever it strikes the bank, it is
deflected toward the other side, and is made to move in
the direction of the opposite bank as well as downstream.
182
THE WORK OF RUNNING WATER
The windings that it thus assumes on a flat valley floor are
roughly S-shaped and are called meanders, from the name
of a river in Asia Minor which was, in very ancient time,
noted for having such swinging curves. The size of these
curves will be proportional to .the size of the river.
Great rivers like the Mississippi have a swing of several
miles, while a small stream may have a swing of only a
BOTTOM LANDS
few feet or rods. These meanders are continually chang-
ing their shape, owing to the cutting and filling.
The meanders sometimes become so tortuous that thej
downstream side of one curve approaches the upstream
side of another and even cuts into it, thus causing the
river to desert its curved path and straighten itself at this
point. The old deserted winding looks something like an
oxbow, and when filled with water, is called an oxbow lake.
RIVER DEVELOPMENT 183
Sometimes the meanders are artificially straightened, as
has been done in the lower Rhine valley, and much arable
land reclaimed.
In time of flood, when a river spreads over its flood plain,
the velocity of the water is checked outside the channel
and some of the sediment it carries is deposited. The most
STREAM MEANDEBING ON ITS FLOOD PLAIN
sudden check in velocity occurs where it leaves the channel,
so more material will be deposited here than elsewhere on
the flood plain. The banks of the channel will thus be
built up more rapidly, and the flood plain near the river will
slope away from the channel instead of toward it.
This is well shown in the lower Mississippi, where the
river is found to be flowing on a natural embankment, the
side streams running away from the river instead of into
184
THE WORK OF RUNNING WATER
it. In some places the embankment
is fifteen or twenty feet above the
rest of the flood plain. These natural
levees, as they are called, often force
the tributary streams to flow for long
distances upon the flood plain before
they can enter the main river. The
Yazoo River is forced to flow along
the flood plain some 200 miles before
it can enter the Mississippi.
These natural levees form the only
available sites where the lower river towns and cities, such
as New Orleans, can be built.
OXBOW LAKES
A stretch of the Missis-
sippi and some of its
abandoned meanders.
LEVEE ALONG LOWER MISSISSIPPI
Artificial levees are often built to keep rivers from over-
flowing their flood plains. Such are the high levees along
the Lower Mississippi and*Sacramento Rivers.
RIVER DEVELOPMENT
185
Sometimes the flood plain of the main river is built up
more rapidly than the tributaries can build theirs, so that
they are dammed up as they enter the flood plain of the
main stream and form a series of fringing lakes along its
border. A fine example of this is found in the lower course
of the Red River of Louisiana.
AN OLD RIVER
This river has done its work and has completed its activities.
When a river has graded itself and built its flood plain,
its own active work consists largely in carrying off the
materials brought to it by its side streams. Although
these are now able to appropriate no new territory they
continue to wear down the country and round off the divides
till the whole region, unless reelevated, is reduced to an
almost level plain with its entire drainage system nearly
186 THE WORK OF RUNNING WATER
at grade. Most of the material now carried by the river
is in solution, and there is but little erosion. The river
has accomplished its life work, it has borne to the sea all
the burden it has to bear, its labors are ended, it has reached
old age.
Rivers in Dry Climates. — In a region where the climate
is very dry, rivers are often intermittent in their flow.
They contain water only after rains. Such rivers may
dry up before they reach any other body of water, their
water entirely evaporating or sinking into the dry soil.
Their development is therefore somewhat irregular.
If the slopes are steep and there is little vegetation to
protect them and hinder the quick run-off of the water,
rivers flood very rapidly, eroding their channels and wash-
ing away their banks. Where they • descend upon level
ground they silt up their old courses and acquire new
channels. Thus a river which for the larger part of the
year is a mere brook may after a rain become a devastat-
ing torrent, bursting its banks and carrying destruction
to settlements and farm lands along its course. It may
even change its entire lower course.
Accidents in River Development. — A river may by some
accident, such as the melting of ice during the Glacial
Period, have had its supply of sediment greatly increased,
causing it for a time to build up its valley floor instead
of eroding it, thus forming a filled river valley. When
the supply of sediment failed the river began cutting down
the filled valley, leaving terraces along the sides to mark
the successive levels at which it flowed. Such terraces are
often very prominent along our northern rivers.
The region in which a river is situated may be elevated,
ACCIDENTS IN RIVER DEVELOPMENT
187
thus affecting its normal development and beginning a
new cycle in its history. The elevating may take place
over its whole drainage area or only over a part of it. It
may take place at any time during the history of the
river. If it takes place after the river has become old
and is meandering on its flood plain, the river will begin
afresh to cut down its valley. But as its meandering
RIVER TERRACES, NORWAY
The river is now cutting down its former plains, leaving terraces.
course has been established, the trench that it now
cuts is not like that of a young river, but is a meandering
trench, and what are called intrenched meanders are formed.
This region will have the steep V-shaped valleys charac-
teristic of a young region and the well-developed drain-
age and meandering rivers characteristic of a mature
region.
It was the intrenched meandering valley of the Meuse
River at Verdun which furnished the upland spur forti-
188
THE WORK OF RUNNING WATER
fications so successfully used by the French in repelling the
German march up the valley.
Not only may a river be elevated, but it may be depressed.
In this case its rate of erosion is diminished, and the river
becomes marshy where the grade is low. Where the river
valleys approach the sea they will be submerged or drowned.
These drowned river valleys form some of the finest
harbors on the coast. San Francisco Bay, Narragansett
INTRENCHED MEANDER
Bay and New York harbor are examples of protected harbors
due to the submergence of rivers. The mouth of the Hudson
was formerly some seventy miles to the east of Long Island,
that of the St. Lawrence to the east of Nova Scotia. In
fact the Atlantic coast north of the Hudson furnishes in-
numerable examples of submerged river valleys.
Delaware and Chesapeake bays, where the early settlers
each had a nice little sea inlet instead of a rough wagon
I.NTBFNCHED MEANDERS.
DELTAS ' 189
road as his means of communication with his neighbors,
are fine examples of submerged river systems. These
drowned river valleys enabled the early settlers to penetrate
easily into the country, and determined many of the early
settlements, like Philadelphia, New York, and Providence.
Deltas. — When a river enters a body of quiet water,
its current is gradually checked and it deposits its material
LAKE BRIENZ FROM ABOVE INTERLAKEN, SWITZERLAND
A rapidly eroding stream at the right has built a great delta dividing
the ancient lake into two parts.
in somewhat the same way as on emerging upon a flat
country. But here the deposition is more gradual and
the slope of the deposited material less steep.- The sedi-
190 THE WORK OF RUNNING WATER
ment, too, is sorted by the water, and the finer material is
carried far out from the river mouth. Formations of this
kind are called deltas, from the Greek capital letter Delta
(A), which has the shape of a triangle. Few deltas have
this ideal shape, but there is a general correspondence to it.
Deltas have rich, fine-textured soils and are very fertile.
The Nile delta during all history has been noted for its
fertility. But they are treacherous places, as they are liable
to inundations by the overflowing of the river at time of
flood. Because they are pushed out into the sea, they
are peculiarly exposed to the sweep of the waves in great
storms. The delta of the Mississippi is more than 200 miles
long and has an area of more than 12,000 square miles. The
Po in historic time has built a delta more than 14 miles
beyond Adria, a former port which gave its name to the
Adriatic Sea.
Inland Waterways and History. — From earliest times
rivers have played a most important part in the world's
history. At first almost all human movement was along
river valleys, as they offered the easiest routes of travel.
Here, too, men found the fertile and easily worked land so
necessary in their primitive agriculture. Thus their settle-
ments were usually placed upon the banks of rivers. In war
the river offered a means of defense, as the Tiber so often
did to Rome.
Before the time of railways, rivers and lakes supplied
almost the only means of inland commerce. In our own
country the hundred and fifty miles of unobstructed river-
way stretching from New York to the north was the great
road from Canada and the Lakes to the sea, fought for
persistently in French and Indian Wars as well as in the
INLAND WATERWAYS AND HISTORY
191
Revolution. If in the Revolution the British could have
obtained control of the Hudson, they would have effectu-
ally separated the colonists in the north from those in the
OLD FORT DEARBORN
Photographed from a model owned-by the Chicago Historical Society.
This fort on the Chicago River fostered the trading post that developed
into the city of Chicago.
south and would probably have been able to crush each
separately.
The Mississippi River served for years as the only artery
of transportation from the interior of the country to the
sea. When Spain held the mouth of this river and Con-
gress was unable or unwilling to exert itself to obtain the
privilege for American boats to pass to the sea, it seemed
for a time that the sturdy colonists along the Ohio and
Mississippi would either form an independent country
192 THE WORK OF RUNNING WATER
and fight for the privilege or else in some way ally them-
selves with Spain, so vital to them was the need of this
waterway. In the Civil War vast amounts of blood and
treasure were spent in fighting for the control of this river.
The majority of the great cities of this country owe their
beginnings to facilities for water transportation. Many
of them were first established as forts to control lines of
water communication. Some of the most important of them
were situated near portages from one water system to an-
other. These naturally became trading posts ; and as the
white population increased, they developed into important
settlements.
It was reasonable that these places should be among the
first to enjoy railway facilities. If it happened they were
situated on navigable systems that tapped regions of great
natural resources, they became great trading cities. If
they had the additional good fortune to be in the midst of
great coal fields, manufacturing eventually added to their
prosperity. If in addition to all these advantages, they lay
in the natural lines of " long hauls " of developing railway
systems, they grew with astonishing rapidity. Railways
have also mada possible the building of great " inland
cities," but seldom is the growth of such cities discussed
without the expression of wonder that such great results
should be achieved in spite of the lack of water trans-
portation.
The Improvement of Waterways. — Two thousand years
before Christ the Babylonians connected the Tigris and
Euphrates, thus showing that they realized the commercial
advantages of improved waterways. More than a thousand
years ago China began the extending of her waterways by
THE IMPROVEMENT OF WATERWAYS
193
building a canal several hundred miles long. Since then
almost every civilized nation has discovered for itself the
need of increasing the usefulness of its natural waterways
and has built artificial channels in order to extend cheap
and easy facilities for transportation.
SINGEL CANAL, AMSTERDAM
A canal taking the place of the usual city street.
America has been slower to awake to the importance of
this work than have the nations of western Europe with
their denser populations. Many European countries are
veritable networks of improved river channels and canals.
The Seine carries the greater part of the ocean freight to and
from Paris. The Rhine is used to the very limit of its navi-
194 THE WORK OF RUNNING WATER
gable course. More than ninety-five per cent of the Thames
is open to navigation. A canal thirty-five miles long and
twenty-eight feet deep conducts ocean-going vessels to and
from Manchester. England alone has over two thousand
miles of canals.
At first canals were built entirely for inland carriage, but
later canals of international importance have been con-
PANAMA
An example of man's domination over nature.
structed to shorten the routes of ocean-going steamers.
The Suez Canal reduced the distance by boat from England
to India by about one third. The Kiel Canal, which con-
nects the Baltic with the North Sea, has been of tremen-
dous commercial and naval importance to Germany. The
Panama Canal is a monument to American efficiency. It
gives easy water transportation from the manufacturing
THE IMPROVEMENT OF WATERWAYS
195
cities in the eastern and the central part of the United States
to the Orient and to the western coasts of North and
South America. It also allows the easy concentration of the
United States Navy on either the eastern or the western
coast.
It is to be hoped that the Erie Canal, connecting the
Hudson River and the Great Lakes, will in the near future
CANAL
Two great oceans artificially united.
be made deep enough for ocean-going vessels. Another
project of great importance is the proposed establishment,
by canals and dredging, of a protected waterway from
New England to southern ports. A network of inland
waterways connecting Houston and New Orleans is (Feb-
ruary, 1919) almost completed. By extending the Chicago
Drainage Canal and dredging the Illinois River the Great
196 THE WORK OF RUNNING WATER
Lakes could be connected by navigable channels with the
great Mississippi system. The dredging of portions of the
Mississippi channel, the straightening of its course, and the
building of additional permanent levees must some day be
accomplished. Such improvements would render many cities
along its banks veritable inland seaports.
Waterways such as these would relieve the great freight
congestions that now so frequently occur on railroads and
that will become more frequent with the increase of popula-
tion. While water transportation is slower, it has the great
advantage of being much less expensive. Many such
improvements as have been mentioned have been strongly
recommended by a Commission appointed by the Federal
Government.
Sub-surface Water or Ground Water. — The rain that
sinks into the ground descends slowly along the little cracks
or between the particles of soil until it reaches a point
where it can sink no further, or until it finds an opening
through which it can flow out to the surface at a point
lower than where it entered. Here it may ooze slowly out,
or it may be concentrated in a spring.
If the water which comes to the spring has penetrated
below the surface far enough to get away from the heating
effect of the sun, it will be comparatively cool when it again
emerges, and it will form a cold spring. If, however, in
the region where the spring occurs the rocks are hot at the
depth to which the water penetrated before it found a crack
through which it could come to the surface of the land,
then it will become heated and will form a hot spring.
As the crust of the earth is in many places composed of
rocks in layers, the rain often falls upon the top of a folded
SUB-SURFACE WATER OR GROUND WATER 197
porous rock layer below which is a rock through which
it cannot penetrate. The water will then accumulate
HOT SPRINGS IN THE YELLOWSTONE NATIONAL PARK, U. S. A.
throughout the porous rock. If this rock layer in another
part of its extent is overlaid by an impermeable layer, its
water is held in by the impermeable rocks above and below,
and so is under hydraulic pressure. When a hole is made
FIGURE 81
in the upper rock layer (Figure 81), the water will flow to
the surface, and if the pressure is sufficient it may gush out
of the hole.
THE WORK OF RUNNING WATER
Borings of this kind form what are called artesian welh.
These are of great importance in many regions where it is
difficult to obtain sufficient surface water. In some of our
western states the water from artesian wells has been ob-
tained in sufficient quantity for extensive irrigation. Al-
though this water often contains minerals in solution, it
is free from surface con-
tamination and is there-
fore usually healthful for
drinking.
In some places the sur-
face water penetrates into
layers of rock which it
can dissolve, such as salt
or limestone. Here it
forms caves and caverns,
the solid material which
occupied the place of the
cave having been carried
away in solution by the
water. There are thou-
sands of caves of this
kind, but perhaps the
most noted in this coun-
try is Mammoth Cave
with its nearly 200 miles of underground avenues and
grotesquely sculptured halls.
Sometimes the top of one of these caves is nearly eroded
away, leaving a part of its old roof standing as a natural
bridge, such as the natural bridge of Virginia or of Utah.
Supplying Water to Populous Communities. — The supply-
ing of water to large communities has always been one of
FLOWING ARTESIAN WELL
SUPPLYING WATER TO POPULOUS COMMUNITIES 199
man's great problems. Rome received its water supply by
aqueducts from nineteen different sources, and some of
these aqueducts were in use for fifteen centuries. The
ruins of aqueducts built by the Romans are to-day among
the most picturesque sights of the Italian and Spanish land-
scapes. Eighteen great water cisterns, remarkably well
preserved, are the only remains of the once thriving city of
STRETCH OF A ROMAN AQUEDUCT NEAR N!MES, FRANCE
Carthage on the North African coast. Near Tunis may be
seen a stretch of the ancient aqueduct that brought water
to these cisterns from the mountains thirty-five or forty
miles to the south.
Springs and shallow wells have always furnished water
to favorably situated rural districts and sometimes to small
cities. Only in recent times have deep wells been sunk
and water lifted from great depths. Modern large cities
have seldom found supplies of water from underground
sources adequate to the demands of manufacturing and
200
THE WORK OF RUNNING WATER
sanitation, although for many years London and Paris
obtained a considerable part of their water supply from these
sources.
Most of the great cities of the world are largely if not
wholly dependent on near-by rivers and lakes for the water
they use. Others have
gone to the head-
waters of streams in
the hills or mountains,
have conserved these
uncontaminated
waters in huge reser-
voirs, and have con-
structed great pipe
lines to conduct the
water to the cities'
mains. The Los An-
1^^^_imfc_ ^»^^^_ geles aqueduct brings
Ifelfitofe water for a distance
of 250 miles down
over the foothills and
through the desert.
It is capable of sup-
plying a population of
2,000,000. Such an
engineering feat makes
the ancient aqueducts look almost insignificant.
How Water is Delivered through Cities. — Ancient cities
had not the advantages of modern pressure pumps. They
were, therefore, dependent upon gravity to bring water to
them from sources higher than the community served.
Whenever possible, modern cities obtain their water sup-
A PRIMITIVE WATER CARRIER IN MEXICO
HOW WATER IS DELIVERED THROUGH CITIES 201
plies by the same method. But the modern city must do
more than merely obtain water; it must deliver the water
to every part of the city and to the top floors of the tallest
buildings. Where cities obtain water from low levels they
are compelled to use pumps, or pumps combined with stand-
pipes or elevated reservoirs. The pressure of the water in
these standpipes or reser-
voirs forces the water to
faucets throughout the
city. The higher the sur-
face of the water is above
the outlets, the greater
will be the pressure (page
146). Largely on this
account water from a
standpipe or elevated
reservoir has a weaker
flow from faucets on upper
floors than from those on
lower floors of the same
building.
Friction of running
water against the pipes
slows it up, and lowers
the pressure. For this reason a reservoir can serve only
a limited district. Large cities must provide many such
reservoirs. The necessity of furnishing water to the top
floors of very tall buildings and of fighting fire in these struc-
tures has compelled large cities to provide high-pressure
pumps in addition, to reservoirs. These pumps sometimes
keep the water in the mains of the business sections at a
pressure of 300 pounds, or even more, to the square inch.
A STANDPIPE
This furnishes water under high pressure
for the use of a community.
202
THE WORK OF RUNNING WATER
Almost every one has noticed how the opening of a faucet
in a home will reduce the force of the stream from a garden
hose. This illustrates what may happen on a larger scale
throughout a city system. The larger the number of faucets
running at one time, the lower the pressure. For this
reason, most cities try to prevent unnecessary use of water
FIRE-TUG IN ACTION
The "Graeme Stewart" on the Chicago River, throwing streams of
water under tremendous pressure.
in homes during hours when business districts must be
served and protected against possible fires. This is why
many cities forbid the sprinkling of lawns during the busy
hours of the day.
The Vital Importance of Pure Water. — Roman and Greek
writers more than two thousand years ago emphasized the
advantages of a pure water supply to a city. It is now
THE VITAL IMPORTANCE OF PURE WATER 203
generally recognized that a modern city has no task more
vital than that of guarding against contaminated water.
WILSON AVENUE WATER TUNNEL, CHICAGO
Photographed during construction. This tunnel is 12 feet in diameter, is
hollowed out of solid rock 110 feet below the surface of the water,
and extends eight miles from the pumping station on the north shore
to the crib.
Those communities that use polluted water generally have
a very high death rate from typhoid fever and from other
intestinal diseases. Moreover the industrial efficiency of
204 THE WORK OF RUNNING WATER
a population is greatly reduced by sickness. Cities that
receive their water supplies from uncontaminated up-
lands have a tremendous advantage.
Cities along the Great Lakes have run pipes out for miles
to intakes, or cribs, in order to avoid shore contamination.
ONE OF THE CHICAGO INTAKE CRIBS
In time of heavy storms, the sewage from a city sometimes
contaminates the water even at these distant intakes; but
on the whole the supply of water to Great Lakes cities is
good. Those cities which receive water from rivers that are
constantly being polluted by the sewage of communities
farther upstream have a most serious problem, even though
running water tends somewhat to purify itself. In many
cases this problem has been admirably solved.
A TYPICAL FILTER PLANT
205
St. Louis, for example, is typical of many cities that per-
form marvels in transforming muddy river water into clear,
healthful drinking water. The Missouri-Mississippi water
as it enters the St. Louis intake contains mud and sand in
suspension; coloring matter from decaying leaves, as well
ST. Louis FILTER PLANT
This building of reinforced concrete is 750 feet long by 135 feet wide.
as mineral matter, in solution; and disease bacteria. As
the water passes slowly through settling tanks the heavier
sediment falls to the bottom of the tanks. Chemicals are
added. Some of these unite with the coloring matter, and
others with some of the mineral matter, forming chemical
compounds that are not soluble in water. These compounds
may fall to the bottom of settling tanks or may be removed
206
THE WORK OF RUNNING WATER
by filtering through thick beds of sand and gravel. Finally
small amounts of chemicals are added to kill the harmful
SSTSS
FIG. 82. — DIAGRAM SHOWING ST. Louis WATER PURIFYING PROCESS
The arrows show the course of the water through the plant.
bacteria, and the pure water is aerated and forced through
the mains. None of the chemicals used makes the water
harmful to drink or unpalatable to the taste
SUMMARY
When rain falls, some of it evaporates ; some flows away
on the surface of the land; some sinks into the ground, to
return as springs or wells. The water which flows along the
surface has a great effect upon the land. It forms the
little streams which remove the surface water, the huge
rivers which drain the country and form great arteries of
trade, and the beautiful lake-reservoirs which hold back
floods and offer easy transportation to ships.
SUMMARY 207
But most important of all is the erosion caused by flowing
water. It wears down the land's surface, bears away and
deposits the eroded materials, cuts deep trenches, and forms
broad valleys ; it fills lakes and builds great deltas. Falls
and rapids furnish water power for manufactures.
Rivers that have not yet widened their valleys and still
have falls and rapids are called young; an old river is one
whose bed has been worn smooth, and which has built for
itself a broad level valley, through which it wanders, doing
little if any erosive work. Rivers sometimes develop flood
plains through which they wander in S-shaped meanders.
If the region of a river becomes elevated, the river may be
revived, and if it is a meandering river, intrenched mean-
ders will be formed. If a river region becomes depressed,
the river will be drowned. These drowned river valleys
form some of the finest harbors in the world. Many
rivers build deltas when they empty into bodies of quiet
water.
Rivers have always played a most important part in
history, because river valleys offer the easiest routes of
travel and furnish most fertile soils. Even in this day of
railways, the largest cities of the world owe their great size
to combined railway and water transportation facilities.
So important is adequate water transportation that the
countries of Europe have developed a wonderful network of
artificial waterways and the United States contemplates
spending millions of dollars in similar enterprises.
Springs and shallow wells furnish water to favorably
situated rural districts and to some small communities.
Most great cities must depend on surface water. Supplying
water to populous communities is a most difficult under-
taking. Water must be piped to homes and office buildings,
208 THE WORK OF RUNNING WATER
and forced to high levels. If the water is liable to con-
tamination, expensive processes of purification and clarifi-
cation are installed in the interest of public health.
QUESTIONS
Trace the probable journey of the water that fell near your
home during the last heavy rain until it reached its journey's end.
Describe some of the effects of running water that you have
seen.
Give the history of a river's development in a moist climate.
How do rivers in dry climates differ from those in moist climates ?
Describe some of the accidents that are liable to happen during
a river's development.
How have rivers affected history?
What has been man's part in the development of waterways?
What becomes of the water which sinks into the ground ?
How is water supplied to the cities and towns near your home?
Why is a pure water supply so important ?
CHAPTER VIII
WEATHEK AND CLIMATE
The Warming of the Atmosphere. — The sun trans-
mits both light and heat to the surface of the earth through
the atmosphere. On the top of a high mountain the tem-
perature is found to be colder than on the lower levels.
The amount of sun radiation, technically called insolation,
that falls upon a given surface on the mountain is about
the same as that which falls upon an equal surface in the
valley. If the heating effect is
less it must be due to something
besides the number of heat rays
intercepted. FIGURE 83
In the spring when gardeners
wish to hurry the growth of their plants, they cover them
with boxes, the tops of which are made of glass (Figure 83).
It is found that the temperature within the boxes is higher
than that outside.
The high temperature heat rays coming from the sun
pass readily through the glass and are absorbed by the
ground within the box, raising its temperature. The ground
continues to keep warm after the sun ceases to shine because
the heat given off by the soil under the box cannot readily
pass out through the glass. Thus the heat of the sun is in
a certain sense entrapped in the box or cold frame.
209
210 WEATHER AND CLIMATE
Now the atmosphere does for the earth what the glass
does for the cold frame. The rays of the sun pass through
the transparent atmosphere and warm the earth. When
the earth reflects the sun's raysior gives up the heat it has
absorbed, the atmosphere keeps this heat from immediately
passing off into space and leaving the surface cold. Where
the atmosphere is thin as on mountains, not so much of
heat is retained and therefore their surfaces are cold and
often covered with snow. Thus the atmosphere acts as a
blanket and keeps in the heat from the sun, as blankets on
a bed keep in the heat of the body.
Clouds help to hold in the heat. Farmers know that
early frosts are likely to come on clear nights, but not on
cloudy ones. On nights when there is likely to be frost,
plants are covered with pieces of paper, smoky fires are
built around cranberry bogs, and orchards are smudged,
in order to blanket in the heat.
The atmosphere also acts as a sun-shield and protects the
surface of the earth from the consuming heat of the sun. If
there were no atmosphere, the earth's surface would become
intensely hot during the day, when the sun shines directly
upon it, and intensely cold at night; so that life could not
possibly exist. t It has been estimated that if there were
no atmosphere, the mean temperature of the earth's surface
during the day would be 350° F., and during the night — 123°
F. On the moon, where there is no atmosphere, there can
be no life as we know it.
If a column of air is heated it becomes lighter and the
atmospheric pressure at that point is lessened. The cooler
air flows in below and forces the heated air to rise. Thus
with the unequal heating of different places on the earth's
surface, there is a constant tendency of air to move from
THE WARMING OF THE ATMOSPHERE 211
places of high pressure to places of low pressure ; and so
the air is constantly in motion, tending to transfer its
heat and to equalize the atmospheric pressure. The
greater the difference in pressure between places, the
faster the movement of the atmosphere to overcome the
difference.
The latitude of a place has much to do with the amount of
heat it receives. As the sun becomes .vertical to places
north of the equator, the length of the day in the northern
hemisphere increases,
and the time that a
place is in the sun-
shine is greater, so
that it receives more
heat from the sun.
On the 21st of June
PICTURE TAKEN AT MIDNIGHT ON NORTH
CAPE
The sun had not set even at midnight.
all points within
of the north pole, as
at North Cape, have
twenty-four hours of
sunshine ; and the
amount of heat received at the pole during these twenty-
four hours is greater than that received at the equator,
where the day is only about half as long. But so much of
the heat is absorbed by the melting of ice and .the heating
of the seas that have grown frigid during the six months of
night that the sun's heating effect on the atmosphere is rela-
tively small.
Although the latitude of a place has much to do with the
amount of heat received, there are also many other things
which affect its temperature. This will appear when we
consider that Venice, Italy, with its mild and equable
212
WEATHER AND CLIMATE
WINTER SCENE IN VENICE
climate, is in almost
the same latitude as
Montreal, Canada.
As has been seen,
the height above the
sea makes a differ-
ence with the tem-
perature, since there
is less thickness of
air above and there-
fore a thinner blanket
to hold the heat.
Then, too, the kind
of soil affects the
temperature. If the
soil is sandy and there is little or no vegetation, it becomes
rapidly heated in the daytime and radiates back the heat
into the air very
rapidly, thus making
the temperature of
the air near the sur-
face very hot during
the day; while at
night, when the sun
is not adding heat, it
rapidly loses the heat
acquired during the
day, and so the tem-
perature of the air
becomes low. In the
, WINTER SCENE IN MONTREAL,
The famous Ice Palace, built entirely of
sandy deserts the blocks of ice.
RECORDS OF WEATHER CONDITIONS
213
heat is almost unbearable, but at night it is so cold that
heavy blankets are needed to keep the traveler warm.
The nearness to the sea and the direction of the wind
also greatly affect the temperature of a place. In some
parts of the earth these are the principal causes in deter-
mining the temperature. Thus the temperature of the
atmosphere at any place is not due to a single cause, but
is the result of many and complex causes such as latitude,
height, direction of prevailing winds, ocean currents, near-
ness to the sea, and kind of soil.
Graphic Method of Showing the Temperature of a Region.
— It is often quite essential that the temperature over a
considerable region should be
known and a record of it made
and preserved. This might be
done by taking a map and writ-
ing their temperatures above the
different places marked on the
map. This would make a map
full of small figures and very
difficult to read.
A much better method has
been developed and is now almost
universally used. In making this map the temperatures
are first written on the map and then lines are drawn
through places which have the same temperature. These
lines are called isotherms and the map is called an isothermal
map. By the use of such a map it is possible at a glance
to determine the temperature prevailing at any place
and to see the relation which this has to the tempera-
ture of other places on the map. As a rule the isotherms
\1> IS- „.
FIGURE 84
214
WEATHER AND CLIMATE
FIGURE 85
are not drawn for each degree, but only for each ten
degrees.
When the map has been constructed, copies are made in
which the figures are left off and only the isotherms are
preserved. In Figure 84 we have
a plan before the isotherms are
drawn, and in Figure 85 after
the isotherms are drawn. Figure
86 is a typical isothermal dia-
gram. If the map itself were
sketched, it would be an iso-
thermal map.
Maps recording barometric
conditions are made in the same
way as the isothermal maps, only their lines pass through
places of equal barometric pressure instead of places of
equal temperature. These lines are called isobars.
Weather maps are prepared by
the United States Weather Bureau
every day, on which are both the
isotherms and isobars for that
day. The data for these maps
are telegraphed each morning
from stations scattered all over
the settled part of North America.
FIGURE 86
Weather Maps. — Expensive
weather bureaus are maintained not only by the United
States, but by all the other highly civilized countries of
the world. Records are kept also by sea captains and by
other observers throughout the world, and these are
gathered together by scientific men and from them are
CIRCULATION OF AIR
215
made charts of the weather conditions over the entire
surface of the earth. Every year more and more data are
being collected and these charts are becoming more and
more reliable.
These charts are of great value, since they aid in the
explanation of climatic conditions in different parts of the
world. The results
of the data thus
gathered together
have been of untold
service to commerce
and each year have
saved many lives and
a vast amount of
wealth.
Circulation of Air.
— The atmosphere is
the circulatory medi-
um of the earth, as
blood is for the ani-
mal and sap for the
plant. Without it
the activities of the earth would stagnate. It scatters the
seeds of plant life over the face of the earth. It carries
water evaporated from the sea to the land, replenishes the
underground reservoirs for man's use, and transports
reserve supplies to the mountains for the use of cities,
for power, and for irrigation. It cools the hot regions
with the invigorating breath from the mountains and from
the uniformly tempered sea. It warms the cold places by
bearing to them the heat taken from the warmer ocean
A SAILING VESSEL
Both the sailing vessel and the steamship are
dependent for power on movements of the
air — winds and drafts.
216
WEATHER AND CLIMATE
FIGURE 87
waters and from the parched places of the earth. By its
movements, it keeps the very fires of man's factories and
engines burning, sweeps the smoke and foul air away from
his cities, and bears his commerce across the sea.
Wind. — Experiment 75. — On a day when the temperature in
the room is considerably higher than that outside, open a window
at the top and bottom and hold a
strip of tissue paper in front of the
opening. Is there an air current,
and if so, in what direction does it
move at the top and at the bottom
of the window ? What causes
"drafts "in a room?
Experiment 76. — Procure two
similar dishes about 15 cm. high and 5 or 6 cm. in diameter with
short tubes of about 1 cm. in diameter opening out from near the
top and bottom. Connect the bottom tubes of the two dishes
with a tightly fitting rubber tube. Do the same with the top
tubes. Place a Hoffman's screw upon each of the rubber tubes
and screw it tight so that no liquid can flow through either tube.
(If part of each rubber tube is replaced by a glass tube,
the action hi the experiment can be seen to better
advantage.) Fill one of the dishes with colored water
and the other with kerosene or some light oil.
Release the Hoffman's screw upon the top tube and
then the one at the bottom. Notice carefully what
happens as the lower tube is allowed to open. The
dishes are not now filled with oil and water respec-
tively. In the transfer of the liquids, through which
tube did each pass ? FIGURE 88
Experiment 77. — Fill a convection apparatus with
water, putting in a little sawdust and mixing it well with the
water. Heat one side of the tube and observe the convection
currents set up.
In Experiment 76 the interflow from one dish to the other
is due to the fact that the water is heavier than the oil and
WIND
217
runs under it and pushes it up so that the oil overflows
into the dish that the water has left. The same thing
happens in the atmosphere when from any cause the column
of air above one place becomes heavier than that above
another place. There will be under
these conditions a transfer of air,
along the surface, from the place
where the pressure is greater to that
where it is less great, and this move-
ment of the air we call wind.
The wind on the surface of the
earth is not usually in the same
direction as that high up. The
strength of the wind depends upon
differences in air pressures. As the
air pressure is measured by the
barometer, the wind is commonly .
/ In this common appliance
spoken of as due to a difference in the heat of the stove
barometric pressure or to the baro-
metric gradient. Winds are named
from the direction from which they
come. A west wind is a wind that
blows from the west.
If there were no other forces that
affected the movement of the air,
except the high and low pressures,
the transfer would be in a straight line from one place to
the other, and it could always be told in what direction the
high and low pressures were, by direction of the wind.
But obstacles like mountains and hills deflect the air
currents. Chief among other causes which influence the
direction of air movements is the rotation of the earth.
HOT WATER TANK
causes the water to circu-
late in a way similar to
that in which the air is
caused to circulate by
the heated surface of the
earth. The hot water
rises to the top of the
tank from where the
pressure 01 the cold
water in the supply
cistern will cause it to
flow.
218
WEATHER AND CLIMATE
The Effect of the Earth's Rotation on Winds. — Experiment
78. — Revolve a globe from left to right and while it is revolving draw
a piece of chalk from the pole toward the equator. Does the line
as marked on the globe follow a meridian? What is its genera!
direction in lower latitudes? While the globe is revolving, allow
a drop of water to run from one pole to the other. Note the path
it takes.
The rotation of the earth affects the direction of move-
ment of all bodies free to move over its surface. Thus if
EFFECT OF PREVAILING WIND ON GROWING TREES
a current of air starts from the north pole to flow south, it
will, as it goes along, tend to move toward the right, and so
when it reaches middle latitude it is no longer moving
south but southwest. Why this is so can be fairly well
understood if the conditions of this moving body of air
are considered.
EFFECT OF EARTH'S ROTATION ON WINDS 219
As the earth is about 25,000 miles in circumference and
turns on its axis once in 24 hours, a body situated at the
equator is carried from west to east at the rate of about
1000 miles per hour, whereas a body at the poles simply
turns around during a revolution. Thus as we go on the
surface from the poles toward the equator, each point has
an Increasing west to east velocity.
A body of air, not being attached to the surface, will
have this west to east velocity imparted to it very slowly
by friction. Thus as it goes from higher to lower lati-
tudes, it will lag behind particles on the surface which have
this west to east velocity, and so will appear to have an east
to west motion ; just as to a person riding in a rapidly mov-
ing open car on a calm day there seems to be a strong
" breeze." (That the " breeze " is produced by the motion
of the car and not by movements of the atmosphere is
shown when the car comes to a standstill.) The north to
south movement of the air combined with its apparent east
to west movement will give a northeast-southwest direction
to the air current.
On the other hand, suppose an air current is moving from
the direction of the equator toward the north pole. It has
greater velocity toward the east than the part of the earth's
surface it is approaching, and so instead of blowing due
north it takes a northeast course. It can be seen then that
whether an air current moves from the north pole toward
the equator or from the equator toward the north pole, it
will be deflected toward the right.
It can be proved mathematically that all freely moving
bodies on the earth's surface are deflected toward the right
in the northern hemisphere and toward the left in the
southern hemisphere. This statement is called Ferrel's law.
220
WEATHER AND CLIMATE
Planetary Wind Belts. — As the air at the equator re-
ceives a large amount of heat, it becomes warm and light,
while that near the poles is cold and heavy. The air would
thus have a constant tendency to move along the surface
of the earth toward the equator and in an upper current
from the equator toward the poles, just as in the dishes
where water and oil were connected. But this direct
movement is affected by the rotation of the earth and by
certain atmospheric con-
ditions, so that between
25° and 35° both north
and south of the equator
there is an area of high
pressure.
From these areas of
high pressure the surface
currents move both to-
ward the equator and
toward the poles. On
account of the earth's
rotation the directions of
these movements are not
north and south but in the northern hemisphere northeast
and southwest. Winds of this kind must occur on every
revolving planet having an atmosphere ; hence these winds
are called planetary winds.
As the rotation of the earth and the heating of the air
near the equator are conditions that do not change, among
the most permanent things about our planet are the belts
into which the wind circulation is divided. The change
in the position of the heat equator, — the belt of highest
temperature, — due to the apparent movement of the sun
FIGURE 89. — WIND BELTS OP THE
EARTH
WIND BELTS OF THE EARTH 221
north and south, modifies the conditions in these wind
belts during the year. The planetary winds thus modified
are sometimes called terrestrial winds.
Wind Belts of the Earth. — Near the heat equator where
the air is rising there is a belt of calms and light breezes called
the doldrums. As the air here is rising and cooling (page
125), thus losing capacity to hold moisture, this is a cloudy,
rainy belt of high temperature in which much of the land
is marshy and the vegetation so rank and luxuriant that
agriculture is exceedingly difficult.
Extending north and south of the doldrums to about 28°
of latitude are belts in which constant winds blow toward
the doldrum belt and supply the air for the upward current
there. In the northern hemisphere these winds have a
northeast to southwest direction and in the southern hemi-
sphere a southeast to northwest direction. They are the
most constant winds on the globe in their intensity and direc-
tion, and are called trade winds. Since they blow from a
cold region to a warmer region, their power to hold mois-
ture is constantly increasing and clouds and rains are not
usual. The places where they blow are dry belts and in
them are found the great deserts of the world.
On the poleward sides of the trade-wind belts lie the areas
of high pressure already referred to. These are called
the horse latitudes or belts of tropical calms and are rather
ill-defined. The air is here descending and the surface
movements are light and irregular. These, like the dol-
drums, are regions of calms. But unlike the doldrums,
they are dry belts; since the descending air is increasing
in temperature, owing to adiabatic heating (page 125), and
thus its power to hold moisture is increasing. Therefore
224 WEATHER AND CLIMATE
the tendency of the atmosphere in these belts is to take up
moisture rather than to deposit it.
In the middle latitudes there is a belt of irregular winds
which have a prevailing tendency to move from west to east
or northeast. This general eastward drift of the air is
constantly being interrupted by great rotary air movements
having a diameter of from 500 to 1000 miles. These are
called cyclones and anti-cyclones. In this region of the
" westerlies," since the air tends to move from lower to
higher latitudes, an abundance of moisture is usually sup-
plied.
Cyclones and Anti-cyclones. — In the center of the large
storm areas called cyclones, the barometric pressure is
lower than that of the surrounding region, and so they are
marked " Low " on the weather maps. Into these low
pressure areas the air from all directions is moving. But
the winds from high pressure areas do not blow directly into
the center of a cyclone. On account of the rotation of the
earth, any wind that starts toward the center of the cyclone
area is deflected, in the northern hemisphere toward the
right ; in the southern hemisphere toward the left (page 219).
For example, in the northern hemisphere the wind from a
point north of the cyclone center will be deflected to the
west ; the wind from the south will be deflected to the east.
Since all winds blowing toward the cyclone area veer to
the right of the cyclone center, they produce a great whirl
in a direction opposite to the movement of the hands of a
clock. (Figure 90.) In the southern hemisphere the cyclone
rotates in a direction with the hands of a clock.
The rate at which the wind blows varies in different parts
of the whirl, but is never very great. As these are areas
fe
S^^tri
Si
226 WEATHER AND CLIMATE
of ascending and cooling air they are storm areas. The
extent of the precipitation varies in different parts of a
cyclone according to the direction from which the ascending
air has come. Note the direction of the wind and the rain-
fall area as shown on the map (page 225) . Air which comes
from continental interiors is dry, while that from great water
areas contains much moisture, much of which it deposits
when it cools by ascending (page 125). To these cyclones
is due the larger part of
the rain which falls in
middle latitudes.
The anti-cyclone is just
the opposite of, a cyclone.
The center of an anti-
cyclone is a place of clear
FIGURE 90. — DIRECTIONS OF WINDS IN , , , . ,
AN ANTICYCLONE AND IN A CYCLONE sky and high pressure.
The air movement is
slowly downward and outward from the center. (Figure
90.) These winds are dry, cool, and gentle.
Paths of Cyclonic Storms across the United States. — If
you will watch the weather maps for several days in succes-
sion, you will find that cyclones or " Lows " move in a general
eastward direction. The accompanying map shows the
paths of a large number of cyclonic storms across the United
States. It will be seen from this that although these paths
vary considerably, yet the general direction is a little north
of east. The movement of cyclones is in the general direc-
tion of the prevailing winds of the middle latitudes.
In winter time the average rate of motion of the cyclone
across the continent is about 800 miles a day, while in summer
it is only about 500. The velocity of the wind in the cyclone
PATHS OF CYCLONIC STORMS
227
itself is also much greater in winter than in summer, since
the difference in pressure between the high and the low
areas is much greater. The changes in temperature as the
storms pass are greater in winter than in summer since the
regions from which the northerly and the southerly winds
flow in toward the center of low pressure vary more in their
temperatures.
During the summer months people who live in the Missis-
sippi Valley usually look to the south or southwest for the
SOUTHERN
HIGH
clouds which bring rainstorms. From this direction come
the moist northerly blowing winds (deflecting toward the
east) from the Gulf of Mexico. The heaviest rain is always
in the fore part of the eastward moving cyclone. The mois-
ture laden winds coming from a warmer to a colder region
and ' being forced upward in the cyclone deposit some of
their moisture. In the western part of the cyclone are the
winds blowing from northerly points. These come from
228 WEATHER AND CLIMATE
cooler into warmer regions and their capacity for moisture
is increasing. As the center of the cyclone passes, therefore,
the clouds generally begin to clear and the atmosphere begins
to cool.
Sudden Weather Changes. — In middle latitudes there
often occur, particularly in winter, sudden changes in the
temperature of 20° or more in a few hours. In our own
country, if the temperature falls 20° or more in twenty-four
hours, reaching a point lower than 32° F. in the north or lower
than 40° in the south it is known technically as a cold wave,
and there is a special flag (Figure 91) displayed by the
Weather Bureau to indicate the approach of
such a change.
When these waves extend over the southern
part of the country, they are very destructive
to the orange groves and delicate crops and are
FIGURE 91 known as " freezes." A notable freeze of this
kind occurred in 1886 and did tremendous
damage to the orange groves of Florida. So great was the
effect upon this important industry throughout the orange
belt that for years afterward the " freeze " was the date
from which events were reckoned.
If the northwesterly wind which brings on the cold wave
is .accompanied by snow, it is called a blizzard, and on the
plains and prairies, where the wind has a clear sweep, it
is much dreaded. Cattle and men, when caught in it, fre-
quently perish. In southern Europe the coldest winds
are from the Siberian plains and are therefore northeasters.
In the United States the cold area is at the southwest and
rear of the cyclone, whereas in Europe it is at the north
and front.
THUNDERSTORMS 229
When, instead of the strong, cold, northwest winds which
blow into the rear of a cyclonic area and in the colder seasons
may produce a cold wave, there is a prolonged movement
of highly heated air from the south into the front of the
low pressure, as sometimes occurs during the warm months,
the " hot spells of summer " are caused. The air is sultry,
exceedingly hot and oppressive. Sunstrokes and prostra-
tions from heat are common. The " hot winds " of Texas
and Kansas, the Santa Ana of lower California and the
siroccos of southern Italy are intensified examples of these
winds. All sudden weather changes of this kind are due to
atmospheric conditions related to areas of low pressure.
Thunderstorms. — Often on a hot, sultry summer after-
noon large cumulus clouds are seen to rise and spread out
till they cover the sky. The wind soon begins to blow
quite strongly toward the cloud-covered area, the clouds
moving in a direction opposite to the surface wind. As
the storm clouds approach, a violent blast of wind, often
called the thundersquall, blows out from the front of the
storm. Soon flashes of lightning appear and thunder is
heard. As the storm comes nearer, the rain begins to descend
and for a short time, usually about half an hour, it rains
heavily. Then the clouds roll away and the sky becomes
clear with perhaps a rainbow to heighten the' beauty of the
clearing landscape.
Thunderstorms are caused by hot moist air rising over
certain areas and causing an updraft, which is increased
by the inflow and upward movement of air from the sur-
rounding regions. The condensation of the moisture in the
rising air quickly forms clouds, and these become charged
with electricity. As the electrical charge increases, dis-
230 WEATHER AND CLIMATE
charges take place which cause lightning flashes. These
discharges occur along the lines of least resistance and are
often very irregular and forked. As tall objects are likely
to offer good paths for the discharge, it is safest to keep away
from trees and walls during a thunder-storm.
The air becomes greatly agitated by the lightning dis-
charges and makes us aware of this by the noise of the
thunder, just as the agitation of the air caused by the dis-
charge of a gun is made apparent to us by what we call
the noise of the report. The flash of lightning reaches the
eye almost instantly after the electrical discharge; but
since sound travels at the rate of about a mile in five seconds,
there is often a noticeable lapse of time between the ap-
pearance of the flash and the sound of the thunder. The
noise from different parts of the discharge will reach us at
different times, and to this and the echoing from clouds or
hills is due the roll of the thunder. To tell in miles the
approximate distance of the flash, one has only to divide by
five the number of seconds that elapse between the appear-
ance of the flash and the noise of the thunder.
Frequently in the evening flashes called heat lightning
are seen near the horizon. These are due to the reflection
on clouds of flashes of lightning in a storm which is below
the horizon. Thunder-storms occur sometimes in winter.
They are very prevalent in the tropics.
Tornadoes and Waterspouts. — Sometimes causes like
those which produce a thunder-storm are so strongly de-
veloped that the indraft is exceedingly violent and a furious
whirling motion is produced. Such storms are called
tornadoes. The warm, moist air rises rapidly and spreads
out into a funnel-shaped cloud with the vertex hanging
RAINFALL AND ITS MEASUREMENT
231
toward the earth. In the center of the whirl the air pres-
sure is much diminished and the velocity of the inrushing
whirling wind is tremendous, being often sufficient to de-
molish all obstacles
in its path.
The length of the
path swept over by
a tornado is rarely
over thirty or forty
miles and the width
generally less than
a quarter of a mile.
The rate of progress
in the Mississippi
valley is from twenty
to fifty miles an
hour, usually in a
northeasterly direc-
tion. These storms
are often wrongly
called cyclones.
When storms of this
kind occur at sea, a
water column is formed in the funnel-shaped part of the
storm and they then receive the name of waterspouts.
Rainfall and Its Measurement.— Experiment 79. —Place a
dish with vertical sides in a large open space so that the rim is hori-
zontal and at a height of about one foot above the ground. Fasten
the dish so that it cannot be overturned by the wind. After a
rain, measure the water that has collected in the dish to the smallest
fraction of an inch possible. This will be the amount of rainfall
for this storm.
A TORNADO
Notice the funnel-shaped cloud.
232
WEATHER AND CLIMATE
The amount of rainfall during the year varies greatly
in different places. It amounts to nothing or only a few
inches over some regions, as in parts of Peru where rain
falls only on an average of once in five years. But in the
Khasi Hills region of India it has been known to be over
600 inches ; and over 40 inches, or about the average yearly
EFFECTS OF A TORNADO
The iron windmill was blown across the cellar and protected the people
who had fled there for safety.
rainfall for the eastern United States, has been known to
fall in 24 hours.
The rainfall in different parts of the earth has been care-
fully measured and maps showing its average amount
prepared. As agriculture is largely dependent upon the
amount of rain and the season of the year in which it
falls, these maps tell much about the relative produc-
tivity of different regions of the earth: An annual total
of eighteen or more inches is necessary for agriculture;
RAINFALL AND ITS MEASUREMENT
233
and this must be properly distributed throughout the
year.
On examining a map of the mean annual rainfall (page
235), we see that there are large areas where it is not sufficient
for agriculture with-
out irrigation. Such
areas are within the
belts of dry winds
or in continental in-
teriors far from large
bodies of water. The
rain-bearing winds
coming from the wa-
ter are forced to rise
and cool so that their
moisture is deposited
before reaching these
interior regions.
The rainfall of a
place depend s
largely : (1) upon its
elevation, since most
of the rain-bearing
clouds lie at low alti-
tudes; (2) upon the
direction and kind of
winds that blow over it ; and (3) upon the elevation of the
land about it. The sides of mountains toward the direction
from which the rain-bearing winds approach will be well
watered, while the opposite side may be a barren desert.
A cylindrical vessel having vertical sides, called a rain
gauge, is used to determine the amount of rain. It is placed
WATERSPOUT SEEN OFF THE COAST OF
NEW ENGLAND
234 WEATHER AND CLIMATE
in an open space away from all trees and buildings and
after each rain the amount collected is measured. Snow
is melted before it is measured. As a rule eight or ten
inches of snow make an inch of rain.
If the temperature is below the freezing point, 32° F.,
when condensation takes place, the moisture of the air
will form into a wonderful variety of beautiful six-rayed
crystals. These gather into feathery snowflakes, which
float downward through the air and often cover the ground
with thick layers of snow. Although snow is itself cold, yet
it keeps in the heat of the ground which it covers, so that
in cold regions soil
which is snow-covered
does not freeze as deeply
as that without snow.
Therefore, to keep water
pipes from freezing, it is
MAGNIFIED SNOW CRYSTALS
not necessary to bury
them as deeply in localities where snow is abundant as in
places equally cold where snow seldom falls.
If raindrops become frozen into little balls in their passage
through the air, they fall as hail. Hail usually occurs in
summer and is probably caused by ascending currents of
air carrying the raindrops to such a height that they are
frozen and often mixed with snow before they fall. Some-
times hailstones are more than a half inch in diameter.
They occasionally do great damage to crops and to the glass
in buildings.
Sleet is a mixture of snow and rain.
Rainfall of the United States. — An examination of a
rainfall map of the United States will show that the
RAINFALL OF THE UNITED STATES
235
236
WEATHER AND CLIMATE
distribution of rainfall can readily be divided into four
belts which, although gradually shading the one into the
other, are yet quite distinct. These belts may be called
the north Pacific slope, the south Pacific slope, the western
interior region, and the eastern region.
In the north Pacific coast region the storms of the " wester-
lies " are common, particularly in winter, when the westerly
winds are strong and
stormy. The yearly
rainfall here amounts
to about seventy
inches.
From central Cali-
fornia south the rain-
fall of the Pacific
slope decreases until,
in southern Califor-
nia, there is almost
no rain in summer
and the entire rain-
fall for the year aver-
ages about 15 inches.
The high-pressure
area of the dry tropi-
cal calm belt moves
sufficiently far north
in summer to take this region out of the influence of the
wet westerlies and into that of the drier belt.
The western interior region, extending from the Cas-
cade and Sierra Nevada mountains to about the 100th
meridian, is dry over the larger part of its surface, since
the winds have deposited most of their moisture in pass-
SALMON RIVER DAM, IDAHO
A typical irrigation dam in the United States.
WEATHER FORECASTING 237
ing over the mountains to the west. On the mountains
and high plateaus, however, there is a considerable fall of
rain, as the winds are cooled sufficiently in passing over
these to deposit their remaining moisture. In most of
this region, as also in southern California, irrigation must be
resorted to if agriculture is to succeed. The fall of rain
on the mountains and high plateaus supplies rivers of
sufficient size to furnish water for extensive irrigation,
and so a considerable part of the area which is now prac-
tically a desert will in the future be reclaimed for the use
of man. The government is at present engaged in extensive
irrigation work in this territory.
From about the 100th meridian to the Atlantic Ocean
there is a varying rainfall, but it is as a rule sufficient for
the needs of agriculture. It gradually increases toward
the east, moisture being supplied plentifully from the Gulf
of Mexico and the Atlantic Ocean by the southerly and
easterly winds. The rainfall is well distributed through-
out the year and averages from thirty to sixty inches.
Weather Forecasting. — The data necessary for fore-
casting the weather are telegraphed to the Weather Bureau
stations every day, and a record of them placed on the
weather map. The observations recorded on these maps
furnish the forecasters with all the information obtainable
as to what the weather of the future is to be. It has al-
ready been stated that the dominant cause of our weather
conditions, in middle latitudes, is the eastward movement of
cyclones and anti-cyclones.
If the direction and rate of motion of these can be deter-
mined the weather of those places which are likely to come
under their influence can be foretold with a good deal of
238 WEATHER AND CLIMATE
accuracy. If a cyclone were central over the lower Mis-
sissippi valley with an anti-cyclone to the west of it, we
should expect that the southerly and southeasterly winds
and rains to the east and southeast of the Mississippi would
gradually change to fair weather and westerly winds with
increasing cold, as the cyclonic area was replaced by the
anti-cyclonic.
The rate at which the change would take place would
depend upon the rapidity of the movements of the two
areas of high and low pressure, and the order of change in
the direction of the winds would depend, for any place,
upon the directions taken by the centers of these areas.
The direction of movement and the rapidity of movement
of the cyclonic areas are, therefore, two of the chief factors
which enter into the prediction of the weather. There is
usually an increase in the intensity of the storm as the
Atlantic coast is approached.
Climate. — The average succession of weather changes
throughout the year, considered for a long period of years,
constitutes the climate. Thus, if the average temperature
of a place throughout the year has for a long period been
found to be high, and the rainfall large and uniformly
distributed, the place is said to have a hot and humid climate.
The climate is a generalized statement of the weather.
Two places may have the same average temperature through-
out the year without having the same climate, as in one the
temperature may be quite uniform and in the other very high
at one season and very low at another. Many factors enter
into the making up of a comprehensive statement of climate.
Effect of Mountains on Climate. — All over the world
where people have the money and the leisure they are
EFFECT OF MOUNTAINS ON CLIMATE 239
accustomed to go either to the mountains or the seashore
in summer in order to get where it is cooler. They might
for the same purpose travel northward in the northern
hemisphere, but they would need to go many times as far
to get the same fall of temperature.
In summer one must ascend a mountain on an average
about 300 feet vertically to get a mean fall of 1° F., whereas
TOP OF PIKE'S PEA.K IN SUMMER
Notice the snow and the rocks broken up by freezing water.
one must travel over 60 miles north to get the same change.
In winter one must ascend farther on the mountain and travel
not so far north, to get a change of a degree. As one ascends
a mountain it grows colder and colder. In ascending a
high mountain in the tropics one passes through all the
changes in climate which one would pass in going from the
equator toward the poles.
As already stated, high mountains also affect the climate
of the country near them. The windward side of moun-
240
WEATHER AND CLIMATE
tains is moist, since the moisture in the air is condensed in
rising over them. On the lee side the country is dry, as
the air which moves over it has already been deprived of
its moisture.
The country on the lee side will also be subject to hot,
dry winds like the chinook winds of the eastern Rockies
and the foehn in Switzerland. As the moist winds pass
POPOCATEPETL
A snow-covered mountain in the tropics.
over the mountains their moisture is condensed. This
raises their temperature so that it is above what it would
normally be at the altitude reached. As these winds come
down on the lee side of the mountain, the air is compressed
and thus heated (page 125) so that on this side it is consid-
erably warmer at the same altitude than on the windward
side. Thus high mountains affect not only the rainfall,
but the temperature changes of the region round about.
CLIMATE OF LAKE AND OCEAN SHORES 241
Effects of Large Bodies of Water on Climate. — We have
learned that dark, rough surfaces absorb heat more rapidly
than smooth, light, highly reflecting surfaces. We have
also learned that a great deal of heat is required to raise
MID-OCEAN
Showing the constant motion of the water.
the temperature of water one degree — nine times as much
as is required to accomplish the same result with an equal
mass of iron. It is not surprising then that land surfaces
heat up much more rapidly than water surfaces. How
242
WEATHER AND CLIMATE
much more rapidly cannot be stated with certainty, because
soils differ greatly from one another. The darker or the
coarser the soils, the more rapidly they absorb heat.
There is another very important difference between the
heating of land and of water by the sun. The rays of the
sun penetrate to a
greater depth in
water — especially
clear water — than
in soil. In addition
to this, the water is
constantly in motion
and is communicat-
ing the heat from
the surface to the
cooler waters below.
Thus the summer's
heat affects the water
many feet below the
surface. This makes
a lake or sea a veri-
table storage tank
for summer's heat,
yet the distribution
of heat keeps the
surface waters rela-
tively cool in sum-
mer.
The land, on the other hand, receives all of the sun's
heat upon its surface. The top few inches of soil heat up
very rapidly every summer's day, but soil immediately
below this shallow crust never becomes very warm, and
PALM TREES ON TROPICAL ISLAND OF
TAHITI
There is almost no range in the temperature
of this island throughout the year.
SUMMER AND WINTER EFFECTS ALONG A SHORE 243
does not show appreciable changes of temperature except
with the changing seasons. At a very few feet below the
surface the soil maintains a steady temperature summer and
winter.
Surfaces that absorb heat rapidly also radiate it rapidly.
A large percentage of the heat that the soil has absorbed
during the day is given out to the atmosphere at night.
But the water, slowly storing heat during the warm months
and just as slowly giving it out during the cold months,
has a steadying effect upon the climate of the land adjoining.
On some islands of the sea, the range of temperature through-
out the year is almost imperceptible, whereas in the interior
of continents the average temperature of some of the summer
months is more than a hundred degrees higher than that
of some of the winter months.
Day and Night Effects along a Shore. — In the summer,
the morning sun heats the soil increasingly until, by reflec-
tion and radiation from the land surface, the atmosphere
above it is highly heated and expanded. The cooler air
flows in from the lake or sea and displaces the lighter warm
air. If the sun continues to shine, this landward breeze
persists until late in the afternoon ; but its effect is never
felt many miles inland. At night when the rapidly cooling
soil reaches a temperature below that of the water, the
direction of the breeze is reversed.
Summer and Winter Effects along a Shore. — During
the summer in warm climates, water is heated much less
rapidly than the moist air above it and so it absorbs heat
from the air day and night. This cools the atmosphere,
and cooled air currents from above the water temper the heat
of the adjoining land.
244 WEATHER AND CLIMATE
During the winter the water gives up its heat more slowly
than the atmosphere. As it gradually yields the heat it
absorbed during the summer, the air above it is warmed,
and currents of this warmed air modify the . temperature
of the adjoining land. For these reasons a large body of
water slows up the approach of warm weather in spring
and of frosty weather in autumn.
In middle latitudes where the prevailing winds are westerly,
these effects are naturally much more marked and de-
pendable on the east shore of a body of water than on the
west shore. In many places on the east shores of large
lakes, delicate fruits can be raised because the steadying
effect of these bodies of water prevents early " warm spells "
alternating with frosts in spring, and delays the autumn
frosts until the fruits have ripened. The tempering effects
of warm ocean currents, combined with prevailing westerly
winds, account for the mildness of climate even in high lati-
tudes along the west coasts of North America and Europe,
which are the east shores respectively of the Pacific and
Atlantic oceans.
SUMMARY
The earth's atmosphere acts both as a blanket and as a
sunshield to the earth's surface. In addition to this, it is
the circulatory medium of the earth, without which there
could be no life.
Winds and all movements of air are caused by unequal
heating and consequently unequal atmospheric pressure at
different places on the earth's surface. The prevailing
directions of winds are also affected by the rotation of the
earth. Certain winds common to all planets are called
planetary winds; when modified by certain peculiarities of
SUMMARY 245
the earth they are called terrestrial winds. Because of
their constancy and their aid to traffic, some of these winds
are called trade winds.
In middle latitudes there is a belt of irregular winds that
have a prevailing tendency to move from west to east. This
constant eastward drift of air is frequently interrupted by
great rotary air movements having a diameter of from 500
to 1000 miles. These are called cyclones and anti-cyclones.
The cyclone is an area of storm, and the anti-cyclone is an
area of clear sky. These eastward-moving cyclones are
responsible for most of the various changes in our weather.
The two chief factors that enter into the forecasting of
weather in middle latitudes are the direction of movement
and the rapidity of movement of cyclonic areas.
Brief rainstorms accompanied by lightning are called
thunderstorms. They are caused by local updrafts of air
over hot, moist areas. When these local updrafts become
exceedingly violent and of small diameter, tornadoes and
waterspouts result.
{ When moist air cools, it cannot hold as much moisture
as when it is warm, and so the excess falls as rain, hail,
snow, or sleet. The rainfall varies from nothing at all in
some places to over fifty feet a year in others. In the
United States the north Pacific slope has a rainfall of about
seventy inches a year ; the south Pacific slope about fifteen
inches; the eastern slope of the Rockies is very dry; and
the Mississippi valley and the country to the east of it have
a rainfall of from thirty to sixty inches.
The average succession of weather changes throughout
the year considered for a long period of years, constitutes
the climate. The climate of any section depends not only
on latitude, but also upon altitude, nearness to large bodies
246 WEATHER AND CLIMATE
of water, kind of soil, direction of prevailing winds, and
many other causes.
QUESTIONS
How does the atmosphere affect the temperature of the earth's
surface?
How are weather maps constructed?
What is the cause of winds ?
How are the winds of the earth influenced by its rotation?
In going from Boston to Cape Horn through what wind belts
would a sailing vessel pass and how would her progress be affected
by the winds in these belts ?
Describe the wind directions and cloud conditions before, dur-
ing, and after a rainstorm which you have experienced.
Describe the wind and cloud conditions of a thunderstorm.
Upon what does the rainfall of a place largely depend ?
How is the rainfall of the United States distributed ?
What is the effect of mountains upon climate?
How do large bodies of water affect the climate along their
shores?
CHAPTER IX
THE EAETH'S CRUST
Changes in the Earth's Condition. — Several theories
have been offered concerning the original conditions of the
SPIRAL NEBULA
The condition of one of the faint stars as revealed by the tele-
scope. It is millions of miles in extent. Most scientists
believe that the solar system was in such a nebular state as
this ages ago.
earth, but as yet no one of them has been fully accepted.
Almost all scientists agree, however, that the matter of
the earth was once in a nebular, or gaseous, state. Uncounted
ages afterward it came into a molten, or exceedingly hot
liquid, condition ; and it has been gradually cooling ever since.
247
248 THE EARTH'S CRUST
Whenever borings have been made into the interior of the
earth it has been found, after a depth has been reached where
there is no effect from the heat of the sun, that the tempera-
ture rises as the depth 'increases. From this gradual in-
crease in temperature, it must be that far down within the
earth the temperature is very high. The pressure within
the earth is so great, however, that rocks at great depths
are probably not in a molten condition. If the earth had
a liquid interior, the attraction of the other bodies of the
solar system would cause changes in its shape ; but it is as
rigid as steel.
The outside cold part of the earth is called its crust. How
thick this is, no one knows. This is the part of the earth
that is of particular interest to us, for it is the only part
that we are able to observe and study. It is impossible
for us to conceive the eons of time that passed while the
earth's exterior was cooling and changing, and coming into
the condition in which we know it. Geologists think in
tens and hundreds of thousands of years. The mountains
that we see and even the continents we live on are the
product of very recent changes, as geologists measure time,
in the unimaginably long ages that reach back to the first
gathering together of matter forming the earth.
Experiment 80. — When at home measure the greatest and least
circumference of a large, smooth apple by winding a string around
it and then unwinding and measuring the length of the string.
Bake the apple. Measure its circumferences again. Are they
greater or less than before? Is the skin of the apple as smooth as
it was before?
There is every reason to believe that the interior of the
earth is still cooling and contracting. Since the crust is
already cooled, it has ceased to contract. Thus as the
INTERCHANGE OF SEA AND LAND' 249
interior shrinks, the crust must fold up in order still to rest
upon the shrinking interior. The wrinkling of the skin of
the baked apple as the interior of the apple cooled gives
a faint notion of what has been happening to the crust of
the earth through the ages. The cooling of the earth is so
slow that the folding usually disturbs the surface but little
FOLDED STRATA
at a time. In recent hundreds of thousands of years, there-
fore, geological changes have usually taken place very
gradually. These slow changes are still continuing, and
the surface of the earth is being constantly modified.
Interchange of Sea and Land. — In many places at
considerable distances from the ocean, sea shells have been
found in the crust of the earth. Tree trunks are sometimes
found at considerable depths in the sea, standing with
250
THE EARTH'S CRUST
TEMPLE OF JUPITER NEAR NAPLES
Although it can be proved that this coast has been elevated and depressed
several tunes, so gradual has been the movement, that the pillars have
not been overturned.
OLD SEA BEACHES, SAN PEDRO, CALIFORNIA
Three old sea beaches can be distinctly seen on the promontory.
INTERCHANGE OF SEA AND LAND
251
their roots penetrating the ocean floor just -as they stood
on dry land. It can be proved that an old temple near
Naples, Italy, has stood above and then in the sea more
than once since it was built.
Sometimes old sea beaches are found high above the
shore and even at a considerable distance inland. Old
OLD ROCK BEACH, IMPERIAL VALLEY, CALIFORNIA
This is many miles inland, but it was once a part of the coast of
California.
river valleys are located by soundings under the sea, well
out from the present mouths of rivers. From some markings
on the coast of northern Sweden, it appears that the coast
has risen about seven feet during the last 150 years. Obser-
vations along the coast of Massachusetts give reason to
believe that this coast is sinking very slowly.
Facts like these show that the seacoast is not stable but
is subject to upward and downward movements, some of
which are slight, and others great.
252 THE EARTH'S CRUST
Characteristics of Land Surfaces. — The surface of the
land differs from that of the sea in being at least com-
paratively immovable. It is rough and irregular, and is
composed of many different kinds of rocks and soils. For
the larger part of its area it rises above the level of the sea,
but in a few places it sinks below, as in the Salton Sea,
a part of Imperial Valley, California, and near the Dead
Sea in Palestine. Its surface is eroded by wind and water
and is thus constantly but slowly changing its features.
Materials Composing the Land. — Experiment 81. — Obtain
specimens of the igneous rocks, lava, obsidian, basalt, granite ; of the
sedimentary rocks, sandstone, fossiliferous limestone, conglom-
erate, peat; of the metamorphic rocks, gneiss, schist, marble,
anthracite coal. Examine these carefully with the eye and with
a lens, noting whether they have a uniform composition or are
made up of different particles. Are the particles composing the
rocks crystalline? Are they scattered irregularly or arranged in
layers? Test with a file or knife-blade the hardness of the rock as
a whole and of its different constituents. Try a drop of hydro-
chloric acid on the different rocks to see whether they are
affected by it. Describe in a general way the characteristics of
each specimen.
The composition of different land areas varies greatly.
Many different kinds of rocks are often found crowded to-
gether, or it may happen that the same kind of rock covers
a large area. There is no uniformity. The soil on top of
the rock is also variable. In some places it contains the
minerals which are in the rock below and in other places
its composition is not at all dependent upon the bed rock.
The great variety of rocks of which the crust of the earth
is composed has been divided into three great groups in
accordance with the manner in which they were formed.
These groups are igneous, sedimentary, and metamorphic.
MATERIALS COMPOSING THE LAND
253
GRANITE
Igneous rock formed deep below the
surface of the earth.
The igneow rocks are
those which have solidi-
fied from a melted con-
dition. They may have
solidified deep down
within the crust, or on
the surface, or some-
where between the
depths and the surface.
If these rocks cooled
slowly, they will have a
crystalline structure, as
in granite, and if very rapidly, a glassy structure, as in
obsidian. Their structure can vary anywhere between
these two extremes.
A common dark
colored variety of
this kind of rock is
called basalt. There
are many varieties
of igneous rocks, but
they need not be
considered here.
The sedimentary
rocks are those that
are made by deposi-
tion in water. When
rocks are worn away
into fragments and
these fragments are
FOSSIL-BEARING LIMESTONE deposited in water
A sedimentary rock formed from sea shells. they will, under cer-
254
THE EARTH'S CRUST
tain conditions, harden into rocks. The shells and remains
of sea animals also accumulate, and after a time consolidate
into rock.
About four fifths of the land surface of the earth is com-
posed of sedimentary rocks. They vary greatly in color,
durability, and use-
fulness to man.
The sandstones,
which are composed
of little grains of
sand cemented to-
gether, are used for
buildings and for
many other pur-
poses. The lime-
stones, which are
mostly made up of
the remains of sea
animals, are the
source of our lime
and are also used
A sedimentary rock formed from old gravel
beds.
CONGLOMERATE
and are
for building and for
other purposes. The
shales are finely stratified mud deposits often having many
layers in an inch of thickness. These rocks are not crystal-
line. They are composed of fragments of other rocks or
remains of plants or animals and usually occur in layers
or strata.
Bituminous coal is sedimentary rock, formed from plants
of ages ago which have been compressed and solidified by
enormous and long-continued pressure.
The metamorphic rocks have a crystalline structure,
STRUCTURE OF LAND AREAS
255
GNEISS
Probably metamorphosed granite.
often contain well-formed
crystals embedded % in
them and often bands of
crystalline substances ex-
tending through them.
These rocks are modified
forms of either the igne-
ous or sedimentary rocks.
The original, igneous or
sedimentary rocks have
been subjected to forces,
such as heat and pressure, that have produced physical and
sometimes chemical changes in them.
Marble is crystallized limestone, and gneiss is generally
a metamorphosed granite. Slate and mica-schist are
greatly changed clay rocks, and anthracite coal is a metamor-
phosed form of bituminous coal. The rocks of this group
are often hard to distinguish from igneous rocks.
Structure of Land Areas. — Not only do the land areas
differ greatly in the kind of rocks of which they are com-
posed, but also in the way in which these rocks are placed.
Some of the rocks lie nearly in the condition in which they
were originally formed, while others have been folded and
warped and twisted. Vast layers of rocks have been worn
away by the forces which are continually wearing away and
removing the rocks at the surface of the earth, and thus
rocks which were once at great depths below the surface
have been exposed. Even granite rocks which were origi-
nally formed at a depth of thousands of feet below the sur-
face now appear at the surface and are being quarried in
many places.
256
THE EARTH'S CRUST
The folding and warping of the rock layers, as shown by
the picture on page 249, has brought some of the stratified
beds which were originally horizontal into an almost verti-
cal position, so that we now find at the surface the worn-off
edges of these beds. The different kinds of rocks and the
different positions in
which the rock layers
are presented to the
forces which are active
lite in wearing them away
Ek Hj cause great variety in
the forms of the sur-
face features.
STRATIFIED ROCK
These layers have remained horizontal as
originally formed.
Continental Shelf.
— Around the border
of the continents and
of those islands which
are near the conti-
nents, there extends,
in some cases to a distance of two or three hundred miles,
a gradually deepening ocean floor. This gradually deep-
ening border is* called the continental shelf. When this
floor has reached the depth of about 600 feet, the gradual
slant suddenly changes into a quick descent to the depths
of the ocean, two or three miles.
Upon such shelves lie the great continental islands, like
the British Isles and the East Indies. Continental shelves
furnish the great fishing banks of the earth, such as the
Grand Banks of Newfoundland and those around Iceland
and the Lofoten Islands, where fishermen for ages have
obtained vast supplies of fish. There is no equal area of
CONTINENTAL SHELF 257
the earth where the life is so varied and the struggle for
existence so great as on these shallow continental borders.
Here the mud and sand brought down by the rivers is
spread out and the sedimentary rocks formed. It is the
elevation of this shelf which has formed the low-lying
coastal plains which border many of the continents. There
is good reason to believe that the deep floors of the sea
have never been raised into dry land, and that the vast
extent of sedimentary rocks which make up the larger por-
tion of the land has almost all been laid down in regions
which were at the time continental shelves.
Coast Effects Resulting from Upward Movement of the
Earth's Crust. — Experiment 82. — Tack enough sheet lead to a
very rough board so that it will remain submerged when placed in
water. Place the board in a shallow dish of water, lead side down.
Taking the board by one edge, gradually lift this edge above the
water surface. What kind of line does the water form where it
meets the board? In what way would this line be changed if the
board were smoother? If it were rougher? If the edge of the
board is lifted higher, does the position of the water line change?
Does its form materially alter?
Soundings show that a continental shelf has a compara-
tively smooth surface and a gentle slope. If the shelf is
elevated, a strip of level sea bottom is added to the dry
land, and the water will meet this new shore in almost a
straight line. The material forming the shore, both above
and below the water line, will be easily eroded since it has
been recently deposited and has not had time to be consoli-
dated into solid rock.
Waves rolling in from shore will strike the bottom of this
gently sloping shelf at a considerable distance off shore.
The water thus loses velocity, and deposits much of the solid
258
THE EARTH'S CRUST
material it is carrying, forming a sand reef at some distance
from the shore.
The waterways inclosed between sand reefs and main-
land are often of sufficient depth to form protected routes
for coastwise traffic. It is proposed artificially to extend
and to develop certain of these water areas along the eastern
coast of the United States so as to form a protected waterway
INLAND SEA CAVE AND BEACH
This coast has been recently elevated.
from New England to the southern ports. At present the
low, almost featureless shore of this region, with its shifting
sand bars and capes, makes coastwise navigation dangerous,
although it is protected by many lighthouses and life-
saving stations. The general set of the shore currents may
singularly modify the outlines of the reefs, as is shown in the
formation of the three much dreaded capes off the coast of
North Carolina.
Sand hills, " dunes," form upon these reefs, building them
COASTAL PLAINS
259
up and widening them. The sand reefs along the southern
Atlantic and Gulf coasts have in some places sufficient
width and height to accommodate large settlements. In
time the sand blowing landward from these reefs, together
COAST NEAR ATLANTIC CITY
Showing marshes, lagoons, and sand reefs.
with the silt brought by the streams from the mainland, may
fill up the water area (lagoon) between the reef and the main-
land. The filling of these lagoons, both naturally and arti-
ficially, has greatly increased the habitable land of the earth.
Coastal Plains. — A coastal plain is a gradually emerged
sea bottom, and so has shallow water extending out for a
260 THE EARTH'S CRUST
considerable distance from its edge. Along the shore are
marshes and lagoons bordered on their seaward side by sand
reefs, where the winds have piled up the sand brought in by
waves. In some places these sand reefs are so situated that
they are valuable for habitation, as at Atlantic City, New
Jersey, where a large summer resort has grown up, or along
the coast farther south, where a sparse population finds
its home on the broader reef.
A coastal plain increasing in width toward the south
extends from New York to the Gulf. The western coast
of Europe has a considerable plain of this kind. The
Netherlands are situated on land which has been either
reclaimed from the sea naturally in recent geological time
or artificially by man in recent historical time. In the
southern part this reclamation is largely due to the sedi-
ment brought down by the Rhine.
In the western part of the United States the coastal
plain is not as well developed as on the Atlantic border.
But the region about Los Angeles is a coastal plain, and
almost all the characteristics of the broad eastern plain can
be seen in traveling from the ocean to the coast mountains.
Coast Effects Due to Downward Movement of the Earth's
Crust. — Experiment 83. — Cover a small board with a piece of thin
oilcloth which has been most irregularly crumpled. Take the
board by one edge and inclining it slightly gradually submerge it
in a dish of water. What kind of a line does the water form where
it meets the oilcloth? In what way would this line change if the
oilcloth were more crumpled ? If it were less crumpled ? If the
board is more submerged, does the position of the water Ijne change ?
Why does its form materially alter?
Along a coast which has been depressed, the shore line
has moved landward, and a surface rendered irregular by
DEPRESSED COASTS 261
erosion is lapped by the inflowing water. All the irregu-
larities which lie below the water level are filled with water
and the shore line bends seaward around the projecting
elevations, and landward into the gullies and valleys. The
tops of isolated hills now stand out from the shore as islands.
The river valleys which crossed the region now sub-
merged reveal themselves only to the sounding line. Their
A NORWAY FIORD
A result of downward movement of the earth's crust.
landward extensions form estuaries up which the tide sweeps
far into the land. The unsubmerged portions of these
valleys contain fresh-water streams, the size of which seems
insignificant when compared to the size of the estuary.
Sheltered coves and harbors abound, affording protection
to all kinds of craft and fitting these coasts to be of great
commercial importance.
The harvest of the sea replaces what might have been
262
THE EARTH'S CRUST
the harvest of the land. Since the distance along the coast
between two points is much longer than the straight line
distance over the sea, the boat, not the wagon, becomes the
important vehicle of travel.
The effect of a submerged and eroded coastal plain is
seen in the Delaware and Chesapeake Bay region. Here
A SUBMERGED COASTAL PLAIN
the old river courses have been submerged, and the land be-
tween the rivers extends into the ocean in narrow, rather
flat strips with many little inlets along the sides. Easy
water communication is here possible to a considerable
DEPRESSED COASTS
263
distance inland and to almost every part of the land surface
near the coast.
When the country was first settled, these water courses
were most advantageous to the settlers, as the produce of
the farms could be transported to sea-going ships with
comparatively little difficulty, much more easily than would
have been the case if
it had been necessary
to carry it by land.
There was little need
of building roads, as
each farmer had a
protected water high-
way to his door.
Thus a part of this
region was known as
"Tide-water Vir-
ginia."
In Norway the
deep fiords conduct
the sea from the is-
land-studded coast
far into the interior. Their sides rise steeply, sometimes
for several thousand feet from the water's edge, and
descend so steeply below it that large vessels can be moored
close to the shore. Generally there is not sufficient level
land along the sides of the fiord for building roads. The
villages are usually situated where a side stream has built
a little delta, or at the heads of the fiords where the un-
submerged portion of the valley begins.
It was such a coast as this which bred the ancient North-
men, to whom the Sea of Darkness, as they called the
A NORWAY FIORD
Showing large vessels anchored in the deep
water close to the shore.
264 THE EARTH'S CRUST
Atlantic, was terrorless. While less favored and hardy
sailors were dodging from bay to bay along the shore always
in sight of land, they were pushing boldly west, guided
A NORWAY VILLAGE AT THE HEAD OF A FIORD
only by the beacons of the sky, and discovering Iceland,
Greenland, and the American continent.
Hills and Mountains. — Irregular elevations of the
earth's surface are called hills, or mountains when they are
of considerable height. In the general use of these terms
there is no exact line of separation. Elevations which in
mountain regions would be called hills would in a flat region
be called mountains. As a rule, elevations are not termed
mountains unless they are at least 2000 feet high. But if
the general elevation of the country is great, as in the lofty
STRUCTURE OF MOUNTAINS
265
regions of the Rockies, an elevation to be termed a moun-
tain must rise to a striking height above the generally
elevated surface, which is itself nearly everywhere more
than 4000 feet above the sea.
Structure of Mountains. — Mountains are the results
of deformations in the earth's crust, due to causes not
LOFTY MOUNTAINS
The high Sierras.
fully understood. The crust of the earth has been folded,
pushed up, crumpled and in many ways distorted so that
some portions have been elevated to great heights above
sea level.
All lofty mountains have been elevated in comparatively
recent geological time, but this of course means millions
of years ago. If mountains now lofty were geologically
old, they would long ago have been worn down, or eroded,
by winds, rain, streams, avalanches, and glaciers. The
266
THE EARTH'S CRUST
older mountains of the earth are all comparatively low, not
necessarily because they were never elevated as high as the
lofty mountains of to-day, but because their greater age has
longer subjected them to erosion and thus reduced their
height.
The central part of lofty mountains is composed of igne-
ous rocks, but on the sides overlying these, sedimentary
rocks are found. The Rockies, the Alps, and the Himalaya
Mountains are of this kind.
THE MATTE RHORN
A famous peak in the Alps.
Mountain Peaks. — In mountain regions the features
which are often most impressive are the serrated peaks
which rise above the main mass of the mountains. The
shapes of these peaks vary greatly in different mountain
MOUNTAIN RANGES 267
regions and tend to give individuality to the mountains.
The peaks have been formed by erosion, and their pecu-
liarities are due to the different kinds and positions of the
rocks from which they have been carved.
The younger mountains which have not long been sub-
jected to erosion do not show the peak and ridge structure.
All these peaks are the result, not only of original uplift,
but of subsequent carving.
THE TETON RANGE, IDAHO, U. S. A.
Mountains that have been eroded into sharp peaks.
Mountain Ranges. — As a rule mountains are found
in ranges. The mountains in the range are by no means
all the same elevation, nor is the range necessarily contin-
uous, there being often gaps along its course. Neither were
all ranges in a mountain region elevated at the same time.
Those which make up the mountain region of the western
United States differ much in the time of their elevation.
268 THE EARTH'S CRUST
Young Plateaus. — Sometimes large areas of horizontal
rock are elevated high above the sea, forming lofty plains
whose surfaces are often irregular, owing to previous erosion.
Such areas are called plateam. The descent from a plateau
to the lower land is usually steep. Areas of this kind,
where streams are present, suffer rapid and deep erosion,
since the grades of the streams are steep because of the
elevation.
If there is not much rain there will be few streams, and
these will have deep and steep-sided troughs. Such troughs
render the area very difficult to cross. The valleys are too
narrow for habitation or for building roads, and the deep
troughs of the streams are too wide to bridge. Thus the
uplands are isolated.
If these high areas are in a warm latitude, they are desir-
able for habitation on account of their cool climate, due to
the elevation; but if in temperate latitudes, their bleak
surfaces are too cold.
As the river troughs wear back, the harder rocks stand
out like huge benches winding along the course of the rivers.
From the different benches slopes formed from the crum-
bling of the softer strata slant backward. Thus the general
outline of the stream sides will be something like that of a
flight of stairs upon which a carpet has been loosely laid.
An excellent example of a region of this kind which has
been eroded by a strong river gaining its water from a
distant region is that of the Colorado Canon Plateau. Here
is found the grandest example of erosion on the face of
the earth. The rocks are of various colors ; the gorge is
nearly a mile deep and in places some fifteen miles in width.
Words are inadequate to express the grandeur of the pan-
orama spread out before one who is permitted to see this
YOUNG PLATEAUS
269
gigantic exhibition of the results of erosion. Wonderful,
grand, ' sublime, are mere sounds which lose themselves in
the ears of one who looks out upon this overpowering dis-
play of Nature's handiwork.
The region is very dry, and the river receives few and
short branches for many miles of its course. The valley
COLORADO PLATEAU
The Colorado River has cut a deep canon through this high plateau.
is widening much more slowly than it would if this were
a land of considerable rainfall, and as yet the river fills
the entire bottom of the gorge. The valley is in the early
stages of its development and the erosive forces have just
begun the vast work of wearing down the region. The side
streams are small and the interstream spaces broad.
270
THE EARTH'S CRUST
Dissected Plateaus. — If a plateau has been elevated
for considerable time in a region of abundant rainfall, the
streams extend their courses in networks, thoroughly dis-
secting the area and leaving between their courses only
narrow remnants of the upland. The valleys are still
deep, but the intervening uplands are of small extent.
Traveling over the region in any direction except along
THE ENCHANTED MESA, NKW MEXICO
With old Indian village in foreground.
the stream courses is a continual process of climbing out
of and into valleys.
There is very little level space that can be used for cul-
tivation, and on account of the steepness of the slop*- if
is very hard to build roads. The river valleys an; so narrow
that unless the roads are perched high up on the sides,
they are liable to be swept away at the time of flood. Fann-
ing in these regions is very discouraging because of the dim'-
DISSECTED PLATEAUS 271
culty of transporting crops and of finding anything but a
steep side hill on which to grow them.
Railroads can get through only by following the princi-
pal valleys, and here, on account of the narrowness, the
A Burro
engineering of the roads is difficult. Unless the region is rich
in minerals, it can support only a small population, and that
will of necessity be poor. If the forests are cut off, the soil
rapidly washes down the hillsides and leaves naught but bare
surfaces. Regions of this kind are found in the Allegheny and
Cumberland plateaus, extending from New York to Alabama.
272
THE EARTH'S CRUST
Old Plateaus. — If a plateau remains elevated for a
great length of time, the rivers are able to widen their valleys
and wear away all the interstream spaces, except where
these are very broad. Thus the rivers bring the whole
surface down to a comparatively low level, with here and
there a remnant which has not been worn away, but which
shows in its steep sides the edges of the rock layers which
AN INDIAN HOGAN
formerly spread over the whole region. If these residual
masses are large, they are called by the Spanish name
mesas, meaning tables, and if small, buttes, from the French
word which means landmarks.
Some of these mesas are so high and so steep that it is
impossible to climb them, and others are simply low, flat-
topped hills. A traveler in New Mexico and Arizona
will see many of these mesas, which, like the lonely Indian
THE GREAT PLAINS OF THE UNITED STATES 273
huts or hogans, are but scattered remnants of what were
formerly widespread.
On old plateaus travel is easy. There are no deep valleys,
and one can easily pass around the mesas, which only add
charm to what would otherwise be a most monotonous
CLIFF DWELLINGS, ARIZONA
A protected retreat in a mesa.
landscape. When these mesas are high, they are some-
times occupied by a few Indian tribes who have fled to
them for protection, as the medieval barons when hard
pressed fled to their isolated castles.
The Great Plains of the United States. — No exact dis-
tinctions may be made between plains and plateaus. Some
surfaces partake of the nature of both. West of the Mis-
274
THE EARTH'S CRUST
INDIAN HIEROGLYPHICS CUT ON THE
STEEP WALL OF A MESA
sissippi River the open
prairies of the north and
the coastal plain of the
south gradually merge
into a broad extent of
territory that slopes up-
ward until it meets the
eastern Rocky Mountain
plateau five or six thou-
sand feet above sea
level. The slope of this
area is so gradual that
the change of elevation
is hardly noticeable, and
so it is called the Great
Plains. It is probable
that this vast expanse
A HIGH DRY PLAIN IN CENTRAL NEVADA
THE GREAT PLAINS OF THE UNITED STATES 275
of land was tilted upward when the crust of the earth was
folded upward along the great continental divide.
The elevations are either flat-topped hills, the strata of
which are slightly inclined and correspond in position to
those found in the plain beneath, or they are masses of ig-
neous material which appear to have been thrust up through
the rock surrounding them. In the former case the ele-
vations are simply remnants of the layers of rocks which
once extended over the country, but which have now been
eroded away over the larger part of it; in the latter case
they are the igneous masses which have withstood erosion.
SUMMARY
Almost all scientists agree that the matter of the earth
was once in a nebulous state. From this it came into an
exceedingly hot liquid condition and then into a solid state.
The interior of the earth is still hot, but the outside part,
or crust, is cold. As the interior of the earth is still cooling
and contracting, the crust must fold in order still to rest
on the shrinking interior. Thus the surface of the earth
has been slowly changing through the ages, and it continues
to be modified. For example, the sea coast is not stable
but is subject to upward and downward movements. The
surface of the land is rough and irregular and different land
areas vary greatly in composition, in the warping and fold-
ing of rock layers and in the positions of these layers. The
rocks of the earth's crust are divided into three groups :
igneous, which have solidified from a melted condition;
sedimentary, which are made by deposition in water; and
metamorphic, which are forms of igneous or sedimentary
rocks that have been modified by natural forces.
276 THE EARTH'S CRUST
The ocean floor near continents slopes off gradually until
it reaches a depth of about 600 feet, when it suddenly changes
to a sheer depth of two or three miles. This gradually
deepening border is called the continental shelf. Upon
such shelves lie the great continental islands and fishing
banks. The upward movement of these continental shelves
gives us our coastal plains and has greatly increased the
habitable land of the earth. The depression of continental
borders has given us our estuaries, deep harbors, and con-
veniently navigable coasts.
Mountains are the result of folding, pushing up, crumpling,
and other distortions of 'the earth's crust that have occurred
during ages of change. Mountains are usually found in
ranges and the peaks are the results of erosion. Large
areas of horizontal rock that have been elevated high above
the sea level are called plateaus. If subject to great erosion,
plateaus eventually become dissected and finally worn down
to a comparatively low level, with only occasional mesas
and buttes rising here and there. The Great Plains are a
vast sloping surface that was probably tilted upward when
the crust of the earth was folded along the great continental
divide.
QUESTIONS
What changes have taken place in the earth's condition?
To what great classes do the rocks in your neighborhood belong ?
For what would you look if endeavoring to determine whether
a coast had been elevated or depressed.
What advantages does an elevated coast furnish its inhabitants ?
A depressed coast?
To what is the height of mountains due ?
Describe the characteristics of a young plateau.
Why do not dissected plateaus attract a dense population?
What are the characteristic features of an old plateau ?
CHAPTER X
PREPARATION OF THE EARTH'S SUEFAOE FOR PLANT
LIFE
Changes in the Earth's Surface. — The surface of the
earth is constantly changing. In fact change is the funda-
TC A RECENTLY COOLED LAVA SURFACE
A surface probably somewhat like the original surface of the earth.
mental law of life. There are forces constantly building up
and other forces just as steadily tearing down. Sometimes
277
278 THE EARTH'S SURFACE AND PLANT LIFE
the same forces are doing both. It is impossible to tell
which set of forces is of the greatest service to man; be-
cause without either, life could not continue.
It is believed that the whole surface of the earth originally
hardened from a molten condition, just as lava from a volcano
hardens when it cools. We have seen that the waters of the
sea and the waters that run over the land are wearing away
ROCK SPLIT BY ROOTS OF TREE
the rocks, grinding them together, pulverizing them, and
carrying the wreckage to other places. This eroding must
have begun as soon as the earth's crust became cool enough
for the waters of the atmosphere to condense.
It is necessary, however, to take into account not only the
power of water " to wear away the stones," but also its
ability to hold many substances in solution and to carry them
away to places where the water is evaporated and the dis-
ROCK WEATHERING 279
solved substances deposited. The tremendous power of
freezing water, the weathering power of the atmosphere,
the wearing and transporting power of the wind, the scour-
ing and pulverizing power of moving ice, and the never-
ending processes of growth and decay have also greatly
affected the earth's surface.
Experiment 84. — Allow a test tube filled with water and tightly
corked to freeze. What happens? If the temperature of the air
is not cold enough, place the test tube in a mixture of chopped ice
and salt, or better, chopped ice and ammonium chloride (sal am-
moniac), arid allow it to remain for some time.
Water getting into the cracks of rocks and expanding
when it freezes splits them apart and aids much in their
destruction. Plant roots penetrate into the crevices of
rocks and by their growth split off pieces of the rock. Water,
especially when it has passed through decaying vegetable
matter, has the power of dissolving some rock minerals.
Certain minerals of which rocks are composed change when
exposed to the air somewhat as iron does when it rusts.
Rock 'Weathering. — Experiment 85. —Weigh carefully a piece
of dry coarse sandstone or coquina. Allow this to remain in water
for several days. Wipe dry and weigh again. Why has there
been a change in weight?
Experiment 86. — Fill a test tube or small glass dish about half
full of limewater, made by putting about 2 ounces of quicklime into
a pint of water. Blow from the mouth through a glass tube into
the limewater. There is formed in the limewater a white sub-
stance which chemists tell us is of the same composition as lime-
stone.
Experiment 87. — Continue to blow from the mouth for a con-
siderable time through a tube into a dish of limewater. The
white substance disappears. The carbon dioxide of your breath
dissolved in the water, forming a weak acid, and caused the change.
280 THE EARTH'S SURFACE AND PLANT LIFE
Now if we heat the water, thus decomposing the acid and driving
out the gas, the white substance again appears.
Oxygen, carbon dioxide, and moisture are the chief weath-
ering agents of the atmosphere. Rocks which are exposed
to the atmosphere, especially in moist climates, undergo de-
composition. If the climate is warm and dry, rocks may
ROCKS WEATHERING AND FORMING STEEP SLOPES
stand for hundreds of years without apparent change, whereas
the same rock in another locality, where the weather condi-
tions are different, will crumble rapidly. A striking example
of this is found in the great stone obelisk, called Cleopatra's
Needle, which was brought from Egypt to Central Park, New
York, some time ago. Although it had stood for 3000 years
in Egypt without losing the distinctness of the carving upon
WIND EROSION
281
it, yet in the moist and changeable climate of New York
it was found necessary within a year to cover its surface with
a preservative substance.
Not only do different climates affect differently the
wearing away of rocks, but different kinds of rocks them-
selves vary much in
the rate at which
they crumble. It
has been found that
while marble in-
scriptions, in a large
town where there is
much coal smoke
and considerable
rain, will become
illegible in fifty
years, that after a
hundred years in-
scriptions cut in
slate are sharp and
distinct.
Where the tem-
perature varies
greatly during the
day the expansion
and contraction due to the heating and cooling sometimes
cause a chipping off of the rock surfaces.
Wind Erosion. — The artificial sand blast is in common
use. In it a stream of sand is driven with great velocity
upon an object which it is desired to etch. In nature the
same kind of etching is done by the wind-blown sand.
CLEOPATRA'S NEEDLE, CENTRAL PARK,
NEW YORK
282 THE EARTH'S SURFACE AND PLANT LIFE
WIND-CUT ROCKS, GARDEN OF THE GODS,
COLORADO
These rocks have been fantastically cut by
wind-blown sand.
The glasses in the
windows of light-
houses along sandy
coasts are sometimes
so etched as to lose
their transparency.
Rocks exposed to the
winds are carved and
polished; the softer
parts are worn away
more rapidly than
the harder parts, just
as in all other forms
of erosion. In cer-
tain regions where
the prevailing winds
are in one direction, one side of exposed rocks is found to
be polished, while the other sides remain rough.
Wind Burying and Exhuming. — In exposed sandy regions
where there are
strong winds, ob-
jects which obstruct
the movement of the
air cause deposition
of the transported
sand just as obstruc-
tions in flowing
water cause sedi-
ment to be de-
posited. And just
as sand bars may be
deposited by a river A TREE BEING Duo UP BY THE WIND
SAND DUNES
283
and then carried away again, owing to a change in the
condition of the river's load, so forests and houses in sandy
regions are sometimes buried, to be uncovered again
perhaps by a change in the load carried by the wind.
Sand Dunes. — Sand-laden wind generally deposits its
burden in mounds and ridges called sand dunes (page 258).
A FOREST ON CAPE COD, MASSACHUSETTS, BEING BURIED IN
WIND-BLOWN SAND
When once a deposition pile begins, it acts as a barrier to
the wind and thus causes its own further growth. In great
deserts where the wind is generally from one direction, these
sand dunes sometimes grow to a height of several hundred
feet, but' usually they are not more than 20 or 30 feet high.
They generally have a gentle slope on the windward
side and a steep slope on the leeward side. The sand is
continually being swept up the windward side over the
crest, thus causing the dune to move forward in the direc-
tion in which the prevailing wind blows. (Figure 92.)
284 THE EARTH'S SURFACE AND PLANT LIFE
Almost no plant life can find lodgment in these shifting
sand piles, and so the wind continually finds loose sand on
which to act, and a dune country is always a region of
shifting sands. As the dunes move in the direction of
the prevailing wind they sometimes invade a fertile coun-
try, so that it becomes necessary if possible to find a way
to check their movement. This has been done in some
places by planting certain
kinds of grasses capable
of growing in the sand
and thus protecting the
FIGURE 92 sand particles from the
action of the wind.
Sand dunes are found along almost all low sandy coasts,
and they render difficult the building and maintenance of
roads and railroads to many beach towns.
Wind-borne Soils. — Whenever the wind blows over
dry land, particles of dust and sand are blown away and
deposited elsewhere. The interiors of our houses often
become covered with dust blown from the dry streets. Even
on ships at sea, thousands of miles from land, dust has been
collected.
In volcanic eruptions great quantities of dust are thrown
into the air and spread broadcast over the earth. On the
highest and most remote snow fields particles of this dust
have been found. In the great eruption of Krakatoa, dust
particles made the complete circuit of the earth, remaining
in the air and causing a continuance of red sunsets for
months.
Sand is not carried so far as dust, but at times of strong
wind it is often borne for long distances. Even houses,
SNOW IN WINTER 285
trees, and stones of considerable size may be lifted and
moved by a fierce wind storm. The wind-swept detritus
has been known even to obstruct and modify the course of
streams. Where the wind blows dust constantly in one
direction, deposits of great thickness are sometimes made.
In Kansas and Nebraska there are beds of volcanic dust,
reaching in some places to a thickness of more than a score
of feet, and yet there are no known volcanoes either past
or present within hundreds of miles. In China there is a
deposit of fine, dustlike material, in some places a thousand
feet thick, which is thought by some to be wind blown.
This forms a very fertile and fine-textured soil and supports
a great population. Many of the inhabitants of the region
live in caves dug in the steep banks of the streams, so firm
and fine textured is the material. Wind deposits of this
kind are called loess beds.
Ice as a Soil-builder. — The agent that has had most to
do with preparing the soils of the great grain-bearing regions
of Russia, northern Europe, Canada, and the United States
is ice. It has worn down and pulverized the rocks into
soils, has mixed and transported the soils from regions
farther north, and has laid them down in the irregular
surfaces which form the fertile agricultural fields of these
regions at the present day. Ice has been the master soil-
builder of much of the tillable land of the world, and deserves
careful consideration.
Snow in Winter. — When the temperature of the air
falls below the freezing point, its moisture congeals into
little flake-like crystals and falls as snow. Where the
cold is continuous for a considerable time, the snow may
accumulate in deep layers over the ground. If the heat of
286 THE EARTH'S SURFACE AND PLANT LIFE
the summer is not sufficient to melt all the snow which
falls in the winter, then the layers of snow will increase
from year .to year.
To have this occur the temperature for the whole year
need not be below the freezing point, but the heat of the
summer must not be sufficient to melt all the snow which
MOUNT HOOD, CASCADE RANGE, OREGON
A beautiful old volcanic cone which is continually covered with snow.
fell in the colder season. Lofty mountains, even in the trop-
ics, have their upper parts snow-covered. In the far north
and the far south the line of perpetual snow falls to sea
level, inclosing the mighty expanse of the Arctic and the
Antarctic snow fields.
Glaciers. — Wherever there is not enough heat in the
warm season to melt the snow which accumulates during
GLACIERS 287
the cold season, a thick covering of snow and ice will in
time be formed. The ice is due to the pressure exerted
on the lower layers by the weight of the snow above and
to the freezing of the percolating water which comes from
the summer melting of the upper snow layers.
Although ice in small pieces is brittle, in great masses
it acts somewhat like a thick and viscid liquid. It con-
forms itself to the surface upon which it lies, and under
SNOW FIELDS AT THE HEAD OF A GLACIER
the pull of gravity or pressure from an accumulating mass
behind, slowly moves forward, resembling in some ways
thick tar creeping down an incline or spreading out when
heaped into a pile. Such a moving mass of ice is called a
glacier. The exact manner of glacial movement, however,
is not fully understood.
In mountain regions where the snow holds over through
the summer, the wind-drifts and the snow-slides carry
great quantities of snow into the upper valleys, until ever
288 THE EARTH'S SURFACE AND PLANT LIFE
accumulating masses of snow and ice, hundreds of feet
thick, are formed. The ice then slowly flows down a val-
ley till a point is reached where the melting at the end is
equal to the forward movement. An ice stream of this
CORNER GLACIER
A typical Alpine glacier.
kind is called a valley glacier or an Alpine glacier, because
first studied in the Alps.
Although the moving ice conforms to the bed over which
it passes, it does not yield itself to the irregularities as
easily as does water. When it passes through a narrows
or over a steep and rough descent, it is broken into long,
GLACIERS 289
deep cracks called crevasses. These make travel along glaciers
sometimes very dangerous. The travelers are usually tied
together with ropes, so that if one of the party slips into a
crevasse, the others will be able to hold him up and pull
him out.
A glacier, like a river, is found to flow fastest near the
middle and on top, and slowest at the bottom and on the
CREVASSES IN A GLACIER
Danger points in travel over glaciers.
sides. The rate of motion in the Alpine glaciers varies
generally somewhere between 50 feet and one third of a
mile in a year, being greatest in the summer and least in
the winter.
Alpine glaciers are found not only, as the name would
indicate, in the Alps, but also in Norway, in the Himalayas,
290 THE EARTH'S SURFACE AND PLANT LIFE
among the higher mountains in the western United States,
and in fact wherever the snow accumulates in the mountain
valleys year after
year.
As glaciers creep
down the valleys,
dirt and rocks fall
upon their edges
from the upper val-
ley sides and are
borne along upon
the ice. If two
glaciers unite to form
a larger one, the
debris upon the two
sides which come
together forms a
layer of dirt and
rocks along the
middle of the larger
glacier. At the end
of the glacier this
material which it has
borne along is de-
posited in irregular
piles of rock and
dirt.
The accumulations
of debris along the sides are called lateral moraines, those
in the middle, medial moraines, and those at the end,
terminal moraines. Great bowlders may be carried along
on the ice for long distances without the edges being
THE FIESCH GLACIER
A winding " river" of ice, bearing a medial
moraine.
GLACIERS
291
worn, since they are carried bodily and not rolled as in
streams.
On the under surface of, the glacier, rocks are dragged
along firmly frozen into the ice. The weight of the gla-
cier above presses them with tremendous force upon the sur-
face over which the glacier passes. In this way scratches
or grooves are made in the bed rock underlying the gla-
cier, as well as upon the bowlders themselves. Scratches
A STONE SCRATCHED BY A GLACIER
of this kind are called glacial scratches. The rubbing of
the rocks upon each other wears them away and grinds
them into fine powder called glacial flour, which gives a
milky color to the streams flowing from glaciers.
If a glacier extends over a region where the surface has
been weathered into soil, this fine material may be shoved
along under the ice for great distances.
Wherever glaciers are easily approached they form a
great attraction for the summer tourist. The glistening
white snow fields circled by the green foliage of the lower
292 THE EARTH'S SURFACE AND PLANT LIFE
•slopes, with the glaciers descending in long, white arms down
the valleys, pouring out turbulent, milky-colored streams
from their lower ends, and here and there covered with
bowlders and long, dark lines of medial moraines, form a
picture which once seen is never forgotten, and the entice-
ment of which lures the traveler again and again to revisit
the fascinating scene. The exhilaration of a climb over the
THE DANA GLACIER IN THK HIGH SIERRAS
pathless ice with the bright summer sun shining upon it,
the bracing air, and the ever-changing novelty of the sur-
roundings make a summer among the glaciers almost like
a visit to a land of enchantment.
For this reason Switzerland has become the summer
playground of Europe and America. There the tourist
crop is the best crop that the natives raise, and the scenery
is more productive than the soil.
Norway, with the additional beauty of its fiords, is fast
GREENLAND AND THE ANTARCTIC ICE FIELDS 293
becoming another Mecca of the tourist, and this region,
denuded and made barren by the ancient glaciers, is now
becoming rich and prosperous because of the glacial remnants
still left. The high Sierras, too, are each year enticing greater
A VIEW OF THE JlTNGFRAU, SWISS ALPS
Showing the snowy mountains and verdant valleys, which make
Switzerland the delight of the tourist.
and greater numbers of travelers to enjoy their wonderful
beauties and invigorating climate.
Greenland and the Antarctic Ice Fields. — The whole
of the island of Greenland is covered with a deep sheet of
ice except a narrow border along a portion of the coast
and the part of the island north of 82°, which has little
precipitation. The extent of the ice sheet is nearly equal
to the combined area of the states of the United States east
of the Mississippi and north of the Ohio. The depth of the
294 THE EARTH'S SURFACE AND PLANT LIFE
ice is not known, but probably in some places is at least
several thousand feet. Although along the coast moun-
tains rising from 5000 to 8000 feet are not uncommon,
yet in the interior the thickness of the ice is so great that
no peaks rise above it.
The surface of the inland ice is a smooth snow plain.
Extending from this ice field are huge glaciers having at
their ends a thickness of from 1000 to 2000 feet.
In the Antarctic region an area vastly greater than
Greenland is covered with ice probably of a greater thick-
ness. Although little is known about this ice cap, it is
thought by some ex-
plorers to be nearly
as large as Europe
and to rest partly on
an Antarctic conti-
nent and partly on
the sea bottom.
Icebergs. — When
a glacier extends out
into the sea, the
water tends to float
the ice. If it ex-
tends out into deep
enough water, the buoyancy of the water will be sufficient
to crack the ice, and the end of the glacier will float off as
an iceberg. Glacial ice is about eight ninths under water
when it floats.
Icebergs may float for long distances before they melt.
In the North Atlantic the steamer routes are changed in
the summer months for fear of running into floating bergs.
AN ICEBERG
GLACIAL PERIOD
295
Some of the most appalling disasters of the sea have been
due to ships colliding with icebergs.
Glacial Period. — Careful examination of all the surface
formations over large areas of what are now the most thickly
populated regions of North America and Europe has led
geologists to believe that at a former period in the earth's
history, perhaps not more than a few thousand years ago,
the northern part
of both continents
was covered with a
thick layer of ice.
Evidences of this
ancient ice covering
are seen in North
America as far south
as the Ohio River
and extending over
a vast region which
now enjoys a tem-
perate climate. This
mantle of ice after
several advances and retreats finally disappeared, leaving
the country as we now find it.
Although the border to which the ice extended and many
of the changes which the ice made in the surface of the
country have been carefully studied and mapped, yet
the cause of this extension of the ice and the exact time
at which it occurred have not yet been determined. Many
theories have -been brought forward to account for it, but
none of them explains all the facts.
That the ice was here seems to be sure, but exactly when
A BOWLDER BORNE ALONG ON TOP OF A
GLACIER
Notice the size as compared with the umbrella.
296 THE EARTH'S SURFACE AND PLANT LIFE
or why is unknown. This period when the ice was of great
extent is called the Glacial Period. Probably during the
earth's history there have been several of these periods, but
AREA IN NORTH AMERICA COVERED BY THE ICE OF THE GLACIAL.
PERIOD
to the last is due the great change wrought upon the present
surface of the country and upon plant and animal life.
The greatest ice invasion during this period extended
from northern Canada across New England into the sea,
GLACIAL FORMATIONS 297
across the basins of the Great Lakes and the upper
Mississippi valley and across a part of the Missouri
valley. It wrapped in its icy mantle almost the entire
region between the Ohio and Missouri rivers and the
Atlantic Ocean.
Another great ice invasion spread out from the high-
lands of Scandinavia. As in later days the Norsemen, so
at that time the glacial ice, overspread northern Europe,
carrying Scandinavian bowlders across the Baltic and what
is now the basin of the North Sea, forerunners of the Scan-
dinavian sword which in later ages carried devastation to
these regions.
Prehistoric man probably saw the great ice mantle; he
may even have been driven from his hunting grounds by
its slow encroachment. His rude stone implements are
found mingled with the glacial gravels. But like the spread-
ing ice he has left no record from which the time or cause of
the Glacial Period can be determined.
The thickness of the ice over these central areas was very
great, probably approaching a mile. The pressure on the
ground below must have been tremendous and the scouring
and erosive effect vast indeed. The soil which previously
covered the surface was swept away and borne toward the
ice margin, leaving the rocks smoothed and bare.
Glacial Formations. — The traces left by these ancient
glaciers are unmistakable. When a glacier melts, all the
material which it has moved along under it as well as that
which it has carried on its surface or frozen in its mass is
deposited, forming what is called ground moraine. This
is the formation which constitutes the soil of many of our
northern states. The soil throughout the glaciated region
298 THE EARTH'S SURFACE AND PLANT LIFE
is not of the same composition as that of the underlying
rock ; it must have been transported.
Sometimes the end of a glacier remains comparatively
stationary over an area for a long time, owing to the fact
that the advance of the ice is just about balanced by the
melting. In this case the morainic material which has
collected on the top of the glacier is deposited, forming
irregular heaps of bowlders, gravel, and sand, with inclosed
BOWLDERS AND SAND LEFT BY A RETREATING GLACIER
hollows between. When the glacier has retreated, ponds
and lakes are formed in the depressions, and streams wander
about in the low places between the morainic heaps, receiv-
ing the overflow of some of the lakes and ponds. The
arrangement of the streams is unsymmetrical and without
order. The whole surface is a hodge-podge of glacially
dumped material — a terminal moraine country. It was
this sort of country that made the East Prussian campaign
of the World War so difficult for both Russians and Germans,
and rendered the final defeat of the Russians so disastrous.
GLACIAL FORMATIONS
299
A VALLEY IN NORWAY ROUNDED OUT BY GLACIERS
The moisture in the atmosphere in this region makes it necessary to
hang the hay up to dry, as seen in this picture.
Where a glacier has little load, as near its source, the bed
rock is stripped bare, smoothed, polished, and scratched by
300 THE EARTH'S SURFACE AND PLANT LIFE
the material which the ice has scraped over it and borne
along. Here the soil that is left when the ice has retreated
is very thin. Such is much of the country of New England
and of eastern Canada.
The valleys through which glaciers have gone are left
rounded out and shaped like a U.
MARJELEN LAKE
Glacial Lakes. — The advancing or retreating ice may
happen to make a barrier to the escape of the drainage,
and thus may form a lake with an ice dam at one end.
The lake will continue to exist only so long as the ice ob-
structs the drainage. The Marjelen Lake in Switzerland
is a well-known example of this.
Toward the close of the Glacial Period a vast lake of this
kind was formed in the northern part of the United States.
PRAIRIES OF THE UNITED STATES 301
It extended over the eastern part of North Dakota and about
half of the province of Manitoba. The slope of the land is
here toward the north. As the ice retreated northward it
formed a barrier to the drainage and dammed back a great
sheet of water in front of it. When the ice melted, the lake
was drained, leaving the flat fertile plain through which the
Red River of the North now flows. Glacial lake plains
of this kind form fertile areas of great agricultural value.
The North Dakota-Manitoba area is now one of the most
productive wheat regions in the world.
Prairies of the United States. — North of the Ohio
River and extending westward beyond the Mississippi is a
region of rolling land with a deep, rich soil. Early in the
last century it began to be rapidly populated on account
of its great agricultural advantages. Owing partly to the
fineness of the soil, but mostly to the frequent burning over
of the region by the Indians, the area was destitute of trees
except in some places along the river courses.
Thus the immigrant did not need to go to the trouble and
delay of clearing the forests before beginning to farm. Culti-
vation could begin in earnest with the first spring, and,
as a rule, rich harvests could be obtained. The soil here
is transported soil ; it is deep and unlike that of the under-
lying rock. In some places it is rather stony and in others
very fine and without stones. It is so deep that the under-
lying local rock is seen only in deep cuts.
This soil was probably deposited by the great conti-
nental glaciers which once covered the region and was
spread out either by the action of the slowly moving ice
or by the water from the melting ice. This water flowed
over the surface in shallow, debris-laden streams, bearing
302 THE EARTH'S SURFACE AND PLANT LIFE
their silt into the still waters of transient ice-dammed
lakes. Whatever the original surface of the region, at
present it is an irregularly filled plain due to the ancient
ice sheet. As the soil is composed of pulverized rock not
previously exhausted by vegetable growth, it is strong and
ALFALFA CUTTING ON THE FERTILE PRAIRIES
enduring, so that this country has, since its settlement,
been noted for its productivity.
Soils Produced by Decay. — All the agencies we have
discussed and still others have contributed to breaking down
the rocky crust of the earth into soil, thus preparing the way
for plant life. The very plants themselves and the animal
life which they support must die and return to the soil from
which they came. If it were not for this the earth would
eventually be encumbered with the dead forms of plants and
animals; and the substances of which these bodies are
composed would eventually be exhausted from the soil.
CYCLES OF CHANGE 303
Thus even decay may be looked upon as a process friendly
to man.
Decay is a very complex process. It is produced by forms
of life so small that they can be seen only with a microscope.
There is good reason to believe that there are forms so
small that even the most powerful microscopes will not re-
veal them. The most important of these minute forms of
life are called bacteria. They exist in uncountable millions
almost everywhere. Scientists are acquainted with over 1500
different kinds of bacteria, and each kind has its own peculiar
characteristics. Molds and yeasts are other low forms of life
that help in the processes of breaking down, or disintegration.
All these minute forms of life must have considerable
moisture and some of them, at least, must have free oxygen
in order to thrive and to accomplish their work. Almost
every one who has walked through the woods has noticed
how much more rapidly damp wood decays than dry wood.
It is to keep moisture and air from wood that we paint it,
so that bacteria may not have in it living quarters favorable
to their work of destruction.
Cycles of Change. — Sometimes areas where soils have
accumulated for centuries and centuries have been grad-
ually submerged below the waters of the sea. There these
soils, and even undecayed plant growths, have been consoli-
dated into sedimentary rocks. Ages afterward these areas
have again emerged and the whole process of tearing down
has begun anew. And so the cycles of building up and tear-
ing down continue. Sun, water, ice, bacteria, the move-
ments of the atmosphere, and the slow movements of
the earth's crust are constantly working in league with one
another to tear down what many of the same agencies
have worked steadily to build up.
304 SUMMARY
SUMMARY
The surface of the earth is constantly changing; in fact,
change is the fundamental law of life. There are forces
constantly building up, and other forces just as steadily
tearing down. Among those forces which produce change
are running water, with its power to erode and dissolve;
freezing water, with its tremendous expansion ; the moisture
of the air; the gases of the atmosphere; heat; and the
winds.
But the agent that has had most to do with preparing the
soils of the great grain-bearing regions of the northern
hemisphere is ice in the form of glaciers. Glaciers have their
origin in upper latitudes or altitudes, where the snow accumu-
lates from season to season and is gradually transformed by
pressure into ice. This may spread out and creep down the
valleys like slow flowing rivers. As glaciers creep down the
valleys, the dirt and rocks fall upon their edges from the
upper valley sides and are borne along upon the ice. These
are called lateral moraines. If two glaciers unite to form a
larger one, the debris upon the two sides which come to-
gether forms a layer of dirt and rocks which is called a medial
moraine. The pressure of the glacier on its bed also wears
away the rocks and pulverizes them into soil. When
the end of a glacier melts, the debris that is deposited
is known as a terminal moraine.
Almost the whole of the island of Greenland is covered
with a deep sheet of ice. The depth of this ice sheet is not
known, but probably in some places it is at least several
thousand feet. In the antarctic region an area vastly
greater than Greenland is covered with ice, probably of a
greater thickness. When a glacier extends out into deep
QUESTIONS 305
water, especially in the sea, the buoyancy of the water is
sufficient to crack the ice, and the end of the glacier floats
off as an iceberg.
There are many evidences that large areas of what are now
the most thickly populated regions of North* America and
Europe were once covered with thick layers of ice. This
mantle of ice after several advances and retreats finally dis-
appeared. The period of the last of these several advances
of glacial ice to southerly latitudes is called the glacial
period. These ancient glaciers have left unmistakable
traces, They scoured out depressions in the earth, some of
which now form small lakes and ponds. They pulverized
the rocks in their course and transported the soil thus formed
to latitudes where it now serves agricultural purposes. They
changed the direction of flow of many rivers and dammed
back great sheets of water into lakes which disappeared
when the glaciers melted, leaving flat, fertile plains.
The very plants themselves and the animal life which they
support must die and return by decay to the soil from which
they came. Thus even decay must be looked upon as a
soil-forming process which is friendly to man. Decay is
produced by bacteria and other minute forms of life which
must have considerable moisture in order to thrive and
accomplish their work.
Sun, water, ice, bacteria, the movements of the atmosphere,
and the slow movements of the earth's crust are constantly
working in league with one another to tear down what many
of the same agencies have worked steadily to build up.
QUESTIONS
What examples of rock weathering have you ever seen ?
In what ways has wind acted as a soil builder?
In what ways has ice acted as a soil builder?
306 THE EARTH'S SURFACE AND PLANT LIFE
How are glaciers formed ? How have they modified the surface
of the region where they are found?
What was the extent of the North American ice sheet during the
Glacial Period?
How has the Glacial Period affected the present agricultural and
industrial conditions -of the country over which the ice spread?
In what ways does the process of decay affect the soil ?
CHAPTER XI
MAN'S USE AND CONSERVATION OF SOILS
Importance of the Soil. — The World War has awakened
most people to the dignity and importance of tilling the
soil. For once, it has been brought home to us that we are
dependent upon the nation's farms for our very > existence.
From the soil, either directly or indirectly, come all the
necessaries of life, our food, our clothing, and most of the
building-materials and furnishings of our homes.
Soil. — Experiment 88. — Into a 16-oz. bottle nearly full of water
put a small handful of sand, and into another bottle about the
same amount of pulverized clay. Shake each bottle thoroughly
and allow the water to settle. Which settles the more rapidly?
Which would settle first if washed by a stream whose current was
gradually checked ?
Wherever the inclination is not too steep, we find the
surface of the bed rocks covered for varying depths with
soil. It is upon and in this that plants grow. In it lies
the wealth of our agricultural communities. On examining
this soil, it will be found that in some places it grows coarser
and coarser the farther down we dig. The coarser the pieces
become, the more they resemble the bed rock, until finally
they pass by imperceptible stages into it. This kind of
soil is called local or sedentary soil.
In other localities the coarseness of the soil does not
materially change as we dig into it, but suddenly we come
307
308 MAN'S USE AND CONSERVATION OF SOILS
upon the surface of the bed rock, which may contain few,
if any, of the constituents which were in the soil. This
soil, which in no way
resembles the under-
lying rock, is called
transported soil. We
have already learned
how most of it reached
its present position.
The first kind of
soil has evidently been
formed in some way
from the rock below,
since it gradually
shades into this rock.
This kind of soil
changes with the
change of the bed
rock. A striking il-
lustration occurs in
Kentucky, where the
rich and fertile "Blue
Grass " region is
bounded by the poor
and sandy " Barrens."
The one is underlaid
by limestone and the
other by sandstone.
The soil at the surface is usually finer than the soil a
foot or so below the surface. Sometimes it has a great
deal of decayed vegetable matter mixed with the decom-
posed rock and to this its fertility is often largely due. Some
LOCAL SOIL
This soil has been weathered from the under-
lying rock.
COMPOSITION OF SOILS
309
soils are made up almost entirely of decayed vegetable matter,
peat, and muck. The underlying coarser and lighter colored
soil, which contains little if any vegetable matter, is usually
called the subsoil.
Composition of Soils. — Experiment 89. — Examine under a
strong magnifying glass samples of sand, loam, clay, peat, and other
kinds of soil. Notice the differ-
ent kinds of particles composing
the different soils and the shapes
of these particles.
Experiment 90. — Put a hand-
ful of ordinary loamy soil into a
fruit jar nearly full of water and
allow it to stand for a day or two,
shaking occasionally. At the end
of this time shake very thoroughly
and after allowing it to settle for
a minute, pour off the muddy
water into another jar. Allow
this to stand for about an hour
and then pour off the roily water
and evaporate it slowly, being
careful not to burn the material
left. Examine with the eye, by
rubbing between the thumb and
fingers, and with a magnifying glass, the three substances thus
separated. These three separates will be composed largely of
sand, silt, and clay.
If a compound microscope (Figure 93) is available, mix a bit of
the silt and of the clay in drops of water and put these drops on
glass slides. Examine the drops under the low power of the micro-
scope. Notice the little black particles of decayed vegetable mat-
ter, also the little bunches of particles that may still cling together.
Why was it necessary to soak the soil so long? Draw the shapes
of a few of the particles. Describe the composition of the soil you
have examined.
FIGURE 93
310 MAN'S USE AND CONSERVATION OF SOILS
If we examine most soils with a microscope, we shall
find that they are composed, as was seen in Experiment 90,
of many different kinds of material. Some of these mate-
rials dissolve slowly in water and thus furnish food for
plants; others are insoluble.
In different soils the particles vary greatly in size as
well as in composition. In gravel the particles are large
and in a gram's weight there would be but few ; in sands
RELATIVE SIZES OF SOIL PARTICLES
From left to right : clay, silt, sand, gravel.
there are many more, dependent upon the fineness ; in silt
particles are still smaller ; and in a gram of clay there are
several billion particles. Agricultural soils, intermediate be-
tween sand and clay, are usually called loams. There are
sandy loams and clayey loams, with many intermediate
varieties. As the mineral part of the soil is derived en-
tirely from the rocks, only those minerals which were present
in the underlying rock can IDC present in sedentary soils,
whereas in transported soils the, underlying rock has had
no influence upon the soil.
The minerals composing the soil must furnish certain
WATER FILM ON SOIL PARTICLES 311
substances for the support of plant life. Many of these
minerals are needed in such small quantities that most
soils have an abundance of them. Nitrogen, phosphorus,
and potassium are the soil elements that are used most
freely by the growing plant.
Plants also require a great deal of water. Yet few plants
thrive if they are submerged in it, or even if their roots are
submerged. Air is also necessary to the growth of plants.
Air must reach not only the part of the plant growing above
ground but the underground portion as well.
But if a soil had all necessary substances for plant growth
in it, it would still lack fertility if it were not for the micro-
scopic life of the soil. Some germs increase the fertility
of the soil and some decrease it. If those which increase
fertility are to thrive, certain conditions must be main-
tained. It is the skill of the agriculturist in maintaining
and increasing these favorable conditions which largely de-
termines his success or failure.
Water Film on Soil Particles. — Experiment 91. — Take
about a quart of soil from a few inches below the surface of the
ground and after sifting out the large chunks, put it in a sheet iron
pan and carefully weigh it to the fraction of a centigram. Place the
pan containing the soil in a drying oven or ordinary oven, the tem-
perature of which is but little above 100° C. The soil should be
spread out as thin as possible. Allow it to remain in the oven for
some time, until it is perfectly dry throughout. Weigh again. The
loss of weight will be the weight of water contained in the soil.
As there was no free water in the soil how was this water held ?
Dip your hand into water and notice how the water clings to it
after it is withdrawn. Examine with the eye and the lens several
particles of the original soil as taken from the ground and see if
there is a water film on each of these as there was on the wet hand.
Experiment 92. — Take the soil that has been dried and weighed
in the previous experiment and heat it throughout to a red heat
312 MAN'S USE AND CONSERVATION OF SOILS
over a Bunsen burner or in a very hot oven. Weigh again. If
there is still a loss of weight this must be due to the burning of the
organic matter — rotten twigs, roots, leaves, etc. — which was in
the soil. Soils differ greatly in the amount of water they contain
and in the amount of organic substance present.
We have seen from Experiment 91 how the soil takes
up water, and how each little particle has a film of water
around it. Little hairs on the plant roots are prepared
to take up these little films of water which surround the
soil particles. These water films have probably dissolved
a minute amount of material from the soil particles, and
this material enters into the plant and can be used for
food.
Experiment 93. — Compute the area of a cubical block of wood
four inches on a side. Cut the block in two. Compute the com-
bined area of the two pieces. Cut each of these two pieces in two.
Compute the combined area of the four pieces. Cut each of the
four pieces in two. Compute the combined area of the eight pieces.
What effect does dividing the block into smaller and smaller pieces
have upon the total surface area? Has the mass or volume of
the wood been increased ?
We found in Experiment 93 that the more we subdivided
the block the greater was the combined area of the pieces.
This makes clear an important difference between coarse
and fine soils. The smaller the particles are in a given volume
of soil, the greater is the total surface to be covered by film
water. Then too, the smaller the particles, the more readily
are they dissolved and the greater is the amount of food
within reach of the root hairs of plants.
Soil air. — Experiment 94. — Fill an 8-oz. bottle with soil taken
from a few inches below the surface. Fit the bottle with a two-
holed rubber stopper having the long neck of a three or four-inch
funnel pushed as far as possible through one hole and a bent de-
FERTILE SOILS 313
livery tube just passing through the other hole. See that there is
no air space between the soil and the stopper. The soil in the bottle
should be as hard packed -as it was originally in the ground. If
necessary, push a wire down through the neck of the funnel so as
to free all hard-packed particles of soil in it.
Connect the delivery tube with a bottle full of water standing
inverted on the shelf of a pneumatic trough. Pour water into
the funnel until it is full, and keep
it full during the rest of the experi-
ment. Allow the apparatus thus
arranged (Figure 94) to stand for
some hours. Air will collect in the
bottle over the pneumatic trough.
Where did it come from? When the
soil in the bottle has become entirely FIGUBE 94
saturated with water, roughly com-
pare the amount of air collected with the volume of the bottle
containing the soil. What part of this soil's volume is the collected
air?
We have seen by this experiment that soil contains air
as well as water. Air is needed if plants are to flourish;
and it is necessary that soil air be changed frequently, just
as it is necessary that air in living rooms be changed if
people are to flourish. The soil must be ventilated. Plant
roots must have air to breathe.
Fertile Soils. — Rock disintegration does not furnish
all the complex materials needed for the growth of agricul-
tural plants. Only the lower orders of plants, such as
lichens, can grow on soil as at first formed.
A fertile soil is the product of ages of plant and animal
life, labor, and decay. One of the most important plant-
foods that is furnished by these means is nitrogen. It is
an element that enters into the structure of every living thing.
Practically all the nitrogen compounds in the earth's soil
314 MAN'S USE AND CONSERVATION OF SOILS
have been put there either by the decay of plant and animal
matter — organic matter — or by the direct efforts of cer-
tain kinds of bacteria.
Nitrogen is a gas that constitutes about four fifths of the
atmosphere. Yet the higher forms of plant and animal
life can no more use the free nitrogen of the atmosphere
SOIL IN GOOD TILTH
than a human being can digest carbon. The nitrogen must
be chemically united with other elements into compounds
that are soluble in water before the plant can make use
of it for food. Directly or indirectly, plants furnish the
entire nitrogen supply of animals. Partially decayed organic
matter in the soil is called humus.
We have learned that decay is caused by minute living
things, germs, the most important of which are the numerous
kinds of bacteria. The soil teems with this germ life.
It has been estimated that there are fifty thousand
germs of various kinds in a gram of fertile soil. Certain
kinds of bacteria work the humus over and over, each
SOIL FERTILIZERS 315
kind doing a different work, until the proper nitrogen
compounds are formed. When these are dissolved in
soil water, they are ready to be taken up for food by the
plant.
The bacteria of decay do not add to the nitrogen of the soil ;
they simply work over the nitrogen compounds that they
encounter. Without their activities, the growing plant would
die for want of properly prepared food. In the course of
decay, various acids and gases
are formed. The acids help to
decompose certain minerals into
soluble forms that the plant
can use.
If the acids become too abun-
dant, they make the soil " sour,"
thus preventing the growth of
needful bacteria. Such soil can
be readily "sweetened" by the
17 > f J SOIL BACTERIA
addition of sufficient lime. It is
very easy to test whether a soil is sour or not, by placing
a piece of blue litmus paper in a hole in the ground a few
inches deep, and allowing it to remain there for several
hours. If the blue litmus paper turns red, the soil is sour.
When lime, which is a base, is mixed with sour soil, it
unites with the acids of the soil to form salts that are not
injurious to the needed bacteria.
Soil Fertilizers. — So rapidly do the growing plants use
up soluble compounds of nitrogen that the nitrogen would
soon be removed from most soils if it were not in some way
replaced. There are two other substances that are much
needed by plants and that are soon exhausted from the soil
316 MAN'S USE AND CONSERVATION OF SOILS
by the growing and harvesting of crops. These are phos-
phorus and potassium. Wheat crops, for example, rapidly
exhaust soluble phosphorus compounds from the soil; and
generous supplies of potassium compounds are necessary
for the successful raising of cotton.
Substances that contain elements needed for the life and
growth of plants are called fertilizers. The most common
SOUTHERN COTTON FIELD
fertilizers are manures. They contain nitrogen, potassium,
and phosphorus, in about the proportions needed for the
raising of ordinary crops.
Commercial fertilizers generally contain one or more of
the three elements mentioned, in proportions adapted to
the needs of varying crops. Saltpeter is a compound rich
in nitrogen, and is therefore a good fertilizer. The most
common way in which phosphorus is obtained for fertilizing
is in the form of phosphoric acid. Much of this is prepared
at stockyards from by-products, formerly wasted. Phos-
FERTILIZING AGENTS 317
phate rocks, which are derived from the deposits of
bones of prehistoric animals, are abundant in many
places and furnish tons of phosphorus compounds for
fertilizing.
Wood ashes enrich soil because they contain potash.
Up to the beginning of the recent World War, the great
potash beds of Germany supplied most of the potash used
in agriculture. After the war started the United States
began making efforts to locate potash beds and to produce
potassium compounds in various ways.
In October, 1918, Secretary Lane of the United States De-
partment of the Interior announced that within two years
the United States would be independent of the German
supply. Chemists have discovered practical processes by
which to produce potash from the brine and from the de-
posits of old salt lakes in certain western states. They have
also found ways of extracting potash from seaweeds, which
have never before been of direct service to man; from minerals
that have heretofore been considered worthless; from the
fumes of smelters and from the dust of cement plants, which
have hitherto been considered not only useless but even
injurious. Thus chemistry turns waste into wealth.
Fertilizing Agents. — Among the most important fer-
tilizing agents are the nitrogen-fixing bacteria. These differ
from the other kinds of soil bacteria mentioned, in that they
are able to take nitrogen directly from the soil air and to
combine it into compounds. Farmers know that if a field
is sowed to clover or to soy-beans, for example, it becomes
more fertile. This is owing to the fact that the nitrogen-
fixing bacteria live and multiply in great numbers in knots,
or nodules, on the roots of these plants. When the clover
318 MAN'S USE AND CONSERVATION OF SOILS
or bean crop is harvested, the roots are plowed under to
enrich the soil.
Animals like moles and gophers plow their holes through
the soil, mixing up the particles and making the soil porous,
so that the water can readily get in to aid in breaking up and
decomposing the soil
particles. These
holes also provide
openings through
which plant roots
and soil organisms
can obtain the oxy-
gen and dissolved
food they need.
Ants each year move
vast quantities of
fine material to the
surface, and in some
places change the
surface soil in a few
years.
Angleworms, the
most important ani-
mal soil builders,
BACTERIAL NODULES ON BEAN ROOTS chaimel the Soil wlth
their burrows, thus
providing ready-made openings for the growing roots and
by increasing the porosity of the soil aid in its ventilation
and drainage. They swallow the soil as they make their
burrows, in order to get the decaying vegetable matter for
food, and they grind it fine as it passes through their
bodies. Every year they bring to the surface great quan-
AGRICULTURAL SOILS
319
titles of this finely ground soil mixed with the undigested
vegetable matter. Darwin estimated that the angleworms
in English soil deposited
one fifth of an inch of
these castings each year
over some parts of the
surface. This is the
finest kind of fertilizer.
It is a common saying
that the more angle-
worms the better the
soil.
ANTHILL
., . OM This soil has been brought from below
Agricultural Soils. - and piled up by the ants>
As has already been
shown, soils differ greatly in fineness, mineral composition,
and waterholding capacity. They also differ greatly in the
amount of decayed vegetable material or humus in them.
The humus is a most im-
portant soil ingredient.
It not only furnishes
plant food, but it also
increases the capacity of
the soil for holding mois-
ture and prevents the
soil particles from pack-
ing together too closely.
In sandy soils, since
there is usually little hu-
mus, the water soon
drains out and plants be-
come parched. Such soils
MOLEHILLS
Showing how these animals burrow up
the soil and make it porous.
320 MAN'S USE AND CONSERVATION OF SOILS
warm up quickly in the spring and dry out rapidly after
long wet spells. When humus and plant food in the form
of manure are added, these soils are especially adapted
for growing early crops and crops that do not require a
great deal of moisture, such as grapes. The " Fresno
Sand " of California and the sandy coast plains of the east-
ern United States are soils of this kind.
LUMPY SOIL
The result of cultivating at the wrong time.
In clay soil the particles are extremely small, as are also
the spaces between the particles. Water is therefore taken
up very slowly. It is, however, held tenaciously. Because
so much heat is absorbed in raising the temperature of the
soil water and in evaporating the water that slowly rises
to the surface, clay soils are cold.
When clays become wet, they are very sticky and cannot
be worked. When they dry, they become very hard and
crack. If cultivated at the wrong time they break into
hard lumps and render further cultivation difficult. The
SOIL WATER
321
adobe soil of the West is of this character. If the soil is
nearly pure clay, it is useless for farming. If sufficient
sand or humus can be added, clay soils become valuable,
since they usually contain the elements needed by plants.
A soil having grains about midway in size between sand
and clay is called a silt. This is usually a most fertile soil.
It is the soil of the
western prairies and
the great grain-pro-
ducing states of our
country. It holds
water well, contains
an abundance of
plant food, and is
easily cultivated.
Between these three
types — sand, silt,
and clay — there are
all grades of soils,
presenting problems
of various degrees.
The problem of the
farmer, however, is
to maintain a soil
which holds water
but is well drained,
which contains the elements plants need, and which is
mellow enough to be well aired and to let the plant roots
grow.
Soil Water. — Although many soils contain everything
needful for the production of agricultural plants, yet the
ADOBE SOIL
A heavy clay soil, very fertile but hard to
cultivate.
322 MAN'S USE AND CONSERVATION OF SOILS
rainfall is insufficient
or so unevenly dis-
tributed that these
plants are unable to
grow. This is true
over a large area of
the United States,
and the same condi-
tions often prevail
over the usually well-
watered part of the
country in times of
drought. The ques-
tion of increasing
MUD CRACKS the water-holding
Showing the way clay cracks when it dries. Capacity and of pre-
venting the loss of
water by evaporation or in other ways is a very important one.
PRAIRIE SCENE
Showing modern methods of harvesting the crop from fertile silt soil.
SOIL WATER
323
Experiment 96. — Weigh out equal amounts (about 100 g. each)
of dried gravel, coarse sand, and very fine sand. Put each of these
into a four-inch funnel which has been fitted with a filter paper.
Pour water upon each until all that can be absorbed has been
absorbed. Allow each
to stand until water
ceases to drop from
the funnel. Weigh
again, balancing the
weight of the wet filter
paper retainer by a
similar wet filter paper
placed on the weight
side of the scales.
Which of these sub-
stances is capable of
holding the most water ?
Since water does not
penetrate into the
grains composing these
different substances the
difference in water-
holding capacity must
be due to the different
sizes of the grains.
If we dig deep
enough into almost
any soil we shall find
water. Wells show
this. Certain trees
and plants have such long roots that they can reach the
underlying water and flourish where other plants will die.
When wet lands are so drained by tiling that the plants
can send their long roots down to this constant water
supply or water table, as it is called, they stand a drought
ALFALFA PLANT
The alfalfa roots go deep to seek water.
324 MAN'S USE AND CONSERVATION OF SOILS
much better than plants grown on undrained land where
the water table has not so uniform a depth. The too fre-
quent surface watering of plants is bad for them, as it keeps
RICE SWAMP
A valuable plant growing in water.
their roots so near the surface that the plants are unable to
withstand slight drought.
Certain kinds of plants need more water than others.
Water lilies, reeds, rice, and other plants grow with their
roots submerged in water. Other plants, such as the cactus,.
SOIL WATER
325
sagebrush, and mesquite, can grow only where the supply
of moisture is very scant. Most cultivated crops cannot
live in a soil that holds too much free water ; that is, water
that lies between the particles of the soil instead of in a film
around them. Too much free water excludes the air from
the ground and the plant literally drowns. Even where
there is not sufficient free water to drown the plant, in-
sufficient under-drainage keeps the soil cold and prevents
the injurious substances in solution from being washed out
of the soil. This explains why flowerpots always have a
drainage-hole and why farmers are some-
times compelled to tile their farms.
Experiment 96. — Place small glass tubes
of several different bores in a dish of colored
water. In which is the surface of the water
higher, in the tubes or in the dish ? In which
tubes is it the higher, those of large or small
bore?
Experiment 97. — Place two wide-mouth 4-oz. bottles side by side
and fill one partly full of water. Put a coarse piece of cloth, or
better, a lamp wick, into the water bottle and allow the other end
to hang over into the empty bottle. (Figure 95.) Allow the bot-
tles to stand thus for an hour.
What happens? The force that
causes the rising of water up tubes
and wicks is called capillarity.
Experiment 98. — Tie pieces of
cloth over the ends of four lamp
chimneys. Fill one of the chimneys
with coarse sand, another with fine
sand, another with clay, and the
fourth with a deep black loam. Stand each chimney in a shallow pan
of water. (Figure 96.) Allow them to remain for a week, keeping
water in the pan all the time. Note how high the water has risen
in the different chimneys at the end of an hour ; two days ; a week.
FIGURE 95
FIGURE 96
326 MAN'S USE AND CONSERVATION OF SOILS
It was found in Experiment 91 that each little particle
of soil was surrounded by a film of water, even though there
was apparently no water in the soil. This film will be re-
placed, if removed, just as the water in the top of the wick
(Experiment 97) was replaced by water flowing up the wick.
Roots get a large
part of their water
by absorbing the
water films of the
soil particles.
Gravity is con-
tinually pulling the
soil water deeper
and deeper into the
ground. This deep
soil water is fre-
quently diverted to
lower ground by
impervious layers of
soil or rock and
A NATURAL SPRING COmeS. to the SUrf ace
Coining to the surface between rock layers. as Springs, Or it may
come gradually to
the surface over a broad area a long distance away from
where it fell and make a region, otherwise barren, fertile by
subirrigating it.
Although land must be properly drained, the loss of water
by drainage may in some cases be too rapid. It is often
very essential to stop as far as possible downward passage
of water, or seepage, as it is called. The water in seeping
through the soil dissolves plant food and if allowed to drain
off would decrease the fertility of the soil. Whatever de-
EVAPORATION OF SOIL WATER
327
creases the porosity of the soil will decrease the seepage and
thus help to retain the plant food. This may be done by
adding humus, and sometimes, where the soil is very porous,
by rolling. At the time rain is likely to fall, however, the
soil must be kept loose and mellow so that the water can
sink into it.
Evaporation is, however, the cause of soil's losing the
greatest amount of water. Soil water is constantly mov-
AN ARTESIAN SPRING
A deep water layer has been pierced and the water diverted to the surface.
ing toward the surface on account of capillary action, and
is being evaporated. This loss by evaporation must be
counteracted, if in arid countries or during dry spells agricul-
tural plants are to be provided with sufficient moisture.
Experiment 99. — Fill full of soil four tin cans having small holes
punched in the sides and bottom. Water each with the same
amount of water. Cover the first with about an inch of grass and
the second with about an inch of sawdust, and weigh carefully.
Weigh the third and fourth. Record the weight of each.
Thoroughly stir the surface of the third, as soon as it is dry enough,
about an inch deep. Keep this stirred. Let the fourth stand
undisturbed. Weigh all four every school day for two weeks.
328 MAN'S USE AND CONSERVATION OF SOILS
Keep a record of the loss of weight of each. Why have they lost
weight? How do the grass, the sawdust, and stirring of the earth
affect the loss? Suggest ways to keep soils from losing their
moisture.
In Experiment 99, it was seen that if a layer of grass
or sawdust was put on the top of the soil, the moisture did
DRY FARMING IN EGYPT
not evaporate so rapidly as it did when the soil was not
covered. The grass could have been replaced by shav-
ings, manure, or any substance which would protect the
ground from the sun and wind. Protections -of this kind
are called mulches. They are most frequently used around
trees, vines, and shrubs. It is impracticable to use them
extensively on growing crops.
It was also found that soil water was not readily evapo-
rated where the top of the soil was kept stirred, so that
SOIL WATER
329
the little capillary tubes by which the soil water reaches
the surface were broken and the sunshine and air were kept
from the under part of the soil by a layer of finely divided
soil mulch. When the
surface of the soil is
thoroughly stirred or
cultivated the particles
are separated so far
apart that the water
cannot pass from one
grain to another, and so
is retained in the under
layer ready for the plant
roots. Thorough tillage
of agricultural crops is
perhaps the best way to
assure the plants suffi-
cient moisture in regions
subject to droughts.
In some parts of the
arid region of the United
States dry farming is
practiced. The soil is
deeply plowed and the
plow often followed by
a bevel wheel roller called
a soil packer, in order to pack the under soil or subsoil so that
the air cannot circulate through it and dry out the upper
soil. The surface soil is then most thoroughly cultivated
so as to make as perfect a soil mulch as possible. Thus,
whatever moisture falls is kept from seeping below the reach
of the plant roots and from evaporating from the surface.
KAFFIR CORN
A plant suitable for dry farming.
330 MAN'S USE AND CONSERVATION OF SOILS
In this kind of farming the aim is to use more than one
year's moisture in growing a crop.
Crops are usually planted only every other year, two
years' moisture being retained for one crop. The soil is,
however, kept thoroughly cultivated all the time. Of
course plants requiring the least amount of moisture are
best adapted to dry farming.
IRRIGATION IN SQUARES
Irrigation is the most efficient means of raising crops in
regions of insufficient rainfall or of droughts. Water is
brought to the land from distant sources, or from flowing
artesian wells, or is pumped from wells which have been
sunk to an available water table. In this way water can
be supplied to plants whenever needed. Where the ground
is quite level it is often flooded, sometimes in larger or smaller
squares, with little ridges separating the squares. A great
deal of water is lost in this way by evaporation.
SOIL WATER 331
Another way is to plow furrows eight to ten inches deep
in the direction of the surface slope and run the water into
these from the irrigation ditch. In either case the water
is allowed to soak in until the soil is thoroughly wet. The
surface is then cultivated so as to check surface evaporation.
It has been found that if the soil in certain irrigation regions
IRRIGATION IN FURROWS
does not have adequate under-drainage, it will become water-
logged. Injurious substances from the soil that should be
carried away by downward seepage and drainage are dis-
solved, carried to the surface, and left there by evaporation.
In such cases, artificial under-drainage has proved a neces-
sity.
In the last few years the government and many private
332 MAN'S USE AND CONSERVATION OF SOILS
companies have spent millions of dollars in putting in irriga-
tion plants. By this means thousands of acres of land which
would otherwise have been valueless for agriculture have
been made exceedingly productive.
Alkali Soils. — In dry regions where the rainfall all
sinks into the ground and after remaining for a time rises
to the surface and is evaporated, large areas are found
upon which almost nothing can be made to grow even
ALKALI SOIL
Few plants can grow here because of the excess of alkaline salts.
when sufficient water is provided. Often in the dry sea-
son white or brown crusts appear scattered over the sur-
face in large patches. The white crust usually tastes like
Epsom salts and the brown like sal soda. The salts form-
ing these patches have been dissolved out of the soil by the
soil water and left on the surface when it evaporated.
Such substances are not found in wet regions because
they are carried away by the water which runs into the
streams. About the only way soil of this kind can be treated
to make it productive is to irrigate and drain it, thus washing
the salts out of the soil. This is just what is done by nature
SOIL AND MAN
333
in well-watered re-
gions. Sometimes if
there is not much
alkali, deep plowing
or the planting and
removal of certain
plants such as sugar
beets, which are ca-
pable of growing in
such soils, will
sweeten it.
Soil and Man. -
Although nature
through countless
ages has been preparing the soil, and generation after genera-
tion of plants and animals has been contributing to its
RECLAIMING ALKALI SOIL IN THE SAHARA
ROMAN PLOWING
Showing primitive methods.
334 MAN'S USE AND CONSERVATION OF SOILS
fertility, yet it will not continue profitably to produce
agricultural crops unless carefully handled by man. The
materials taken from it must be replaced by fertilizers. It
must also be thoroughly tilled in order (1) to keep in the
moisture, (2) to prepare a mellow place where the roots of
the plants may spread, (3) to provide air and water and
LABOR-SAVING MACHINERY
Two men with a tractor operate two binders and two shockers. The
shocker is a new invention which receives the bundles of wheat, auto-
matically assembles from 8 to 11 of them into a shock, and deposits
the shock right side up. Each shocker saves the labor of at least two
men.
humus needed by the bacteria which build up the solu-
ble nitrogen compounds, and (4) to kill the weeds which
would use the space and plant foods needed by the grow-
ing crops and would choke them out. Proper tillage prob-
ably has more to do with thrifty and productive farm-
ing than any other one thing. By careful tillage much
expense for fertilizers can be saved and the value of the
crop produced greatly increased.
VALUE OF SOILS
335
Value of Soils. — Many different factors enter into
the determination of the value of a soil. Soils which in
one locality would be of great value are almost valueless in
other localities. Light sandy soil far from a market, un-
less transportation facilities are exceptionally good, is
almost worthless, while the same soil near a city where
GOOD SOIL, A TRUCK FARM
fertilizers can be easily procured and where early vege-
tables find a ready market is of great value.
Different soils are adapted to different crops, and where
a soil, although not good for many crops, is adapted for
raising a crop which in its locality is valuable, the soil is
called good. Thus the soil in many parts of Florida,
although unsuited for raising most crops, is suited for
orange trees and early vegetables, and so is a good
soil. The stony soil in certain of the orange regions
of California would be an exceedingly poor soil for most
crops, but it is good for oranges and therefore it is most
valuable.
336 MAN'S USE AND CONSERVATION OF SOILS
Reclamation of Arid Lands and Low Lands. — Four
thousand years ago the Assyrians made a veritable garden
of the Tigris and Euphrates valleys by dredging lakes for
the conservation of river flood waters and canals for distri-
bution. Tanks, reservoirs, and irrigation canals were in exist-
ence in India centuries before Christ. There are evidences
EAST END OF THE ASSUAN DAM ACROSS THE NILE
The greatest irrigation dam in the world.
that a prehistoric race had extensive irrigation works cen-
turies ago in New Mexico and Arizona.
Modern methods of irrigation make it possible to reclaim
large tracts of land that must have remained waste lands in
ancient days. The building of great dams, the construc-
tion of permanent ditches, and even the boring of water
courses through the sides of great mountains, are among
the great tasks performed by the United States Govern-
ment and by private companies in reclaiming large areas
of land in arid sections of the West.
RESULTS OF A SUDDEN FLOOD
Soil and even buildings have been swept away.
A CYPRESS SWAMP IN LOUISIANA BEFORE DRAINAGE
A floating dredge is used to cut a canal around the area to be reclaimed.
The earth excavated from the canal is piled into an embankment inclos-
ing the tract. In this tract a network of drainage canals and ditches is
dredged from which the surface water is pumped out.
337
338 MAN'S USE AND CONSERVATION OF SOILS
But there are other sections where by another sort of work
millions of acres of exceptionally fertile soil may be re-
claimed. Rich flood plains must be protected against
periodic overflows that often ruin crops and sometimes
ruin even the soil itself. The building of systems of levees
CYPRESS SWAMP RECLAIMED
This is the same section that was shown in the preceding illustration, after
the land had been drained, cleared, and staked out for cultivation.
would prevent this, and the establishment of flood basins
to catch the overflows from the rivers would furnish farmers
in these sections with water for irrigation during the dry
months that often succeed floods. The United States may
well profit by the examples of ancient peoples in reclaiming
such lowlands. Undrained areas of the Great Lakes region
and of the coastal plains may also be reclaimed, as Holland
FORESTRY
339
and Belgium have reclaimed so much of the surface of those
fertile countries.
Forestry. — When rain drops upon the foliage of trees,
its force is broken and it falls to the ground in fine spray.
If the ground beneath is carpeted with leaves and humus,
the soil is further protected from erosion. The water readily
BAD LANDS OF DAKOTA
Running water has so dissected this land as to render it valueless.
soaks into the soil made spongy by leaves and roots. When
the rain is over, evaporation does not take place rapidly
because of the double protection afforded by the shade of
the trees and by the leafy carpet. If the trees are cut away
the rain splashes down on the unprotected soil. Most of
the water runs off the surface, often carrying fertile soil
with it. Even the water which soaks into the ground is
usually quickly evaporated from the unshaded surface.
340 MAN'S USE AND CONSERVATION OF SOILS
In North America before the coming of the white man,
there were probably extensive areas where the growth of
forests had been checked by fires set by the Indians. The
prairie regions were probably much enlarged by the annual
grass fires. All this was done in order to make hunting
less difficult. It is believed that the Bad Lands of Dakota
were once a fertile region which the destruction of the forests
BAD FORESTRY
The hillside was stripped, leaving it a prey to erosion.
left a prey to running water. Erosion has left these lands
valueless for agriculture. It is exceedingly difficult even to
travel over them. It was in these natural fastnesses that the
Sioux Indians made their last ineffective stand against the
white man's civilization. But the white man has outdone
the Indian in reckless destruction of the forests.
If a region is well supplied with forests so that the rain
as it falls is held by the moss, leaves, and roots and pro-
FORESTRY
341
tected from evaporation by the foliage, soil water will
continue to be supplied to the surrounding open land long
after it would have become dry had the forests been removed.
Mountain soils have been found which hold back five times
their own weight of water.
Slopes from which the forests have been removed become
an easy prey to the forces of erosion, and the soil which
BAD FORESTRY
The forest was razed, leaving no small trees for future growth.
for thousands of years has been accumulating may be
swept away by the rainfall of a few seasons, leaving the
slopes bare of soil and devoid of vegetable life. Thus the
sites of valuable forests, which by proper care might have
been continual wealth producers, are rendered nearly
profitless deserts.
The harmfulness, however, does not stop here. The
rain that falls upon these slopes, and which was formerly
retained by the roots and vegetation, so that it slowly
342 MAN'S USE AND CONSERVATION OF SOILS
crept downward into the valleys and streams, now runs
off quickly, flooding the rivers and doing damage to regions
at a distance. Streams which formerly varied but little
in their volume during the entire year now become subject
to great extremes of high and low water. This renders
them less useful for manufacturing, commerce, and water
BAD FORESTRY
The debris was left to feed the forest fires and all the standing
timber was ruined.
supply, to say nothing of the frightful damage done each
year by floods.
Not only is the destruction of our forests a menace to
agriculture and to river navigation, but it actually threatens
our future lumber supply. The ruthless destruction of
vast forests in Europe during the World War has made more
imperative than ever the conservation of what forests we
have left in America.
In recent years the demand for lumber and wood pulp
and the careless and wasteful way in which the forests
have been handled by the lumbermen has greatly reduced
FORESTRY 343
the forests of the United States. It has been authorita-
tively stated that if the present waste of our forest land
continues, the timber supply of the country will be ex-
hausted before 1940. Not only are the forests being reck-
lessly cut down, but forest fires are each year destroying
millions of dollars' worth of timber. When the impor-
tance of lumber to all kinds of industries is considered,
GOOD FORESTRY
Notice how the underbrush and small timber has been cleaned up.
the rapid exhausting of our forest supplies becomes al-
most appalling.
When the native forests are destroyed, trees of other
kinds may in time replace those removed, but frequently
these are of less commercial value. Thus, when the coni-
fer forests of the northern states are cut off, birches and
poplars replace them. If only the larger trees had been
cut, leaving the smaller and younger trees to hold the
344 MAN'S USE AND CONSERVATION OF SOILS
ground, the more valuable forests might have been re-
tained.
The destruction of the forests tends also to extermi-
nate the wild animals and deprives man of a chance to
get away from his
artificial surround-
ings and obtain a
knowledge and an
enjoyment of life and
nature which has
been unaffected by
his own dominant in-
fluence.
In many European
countries the forests
have become a na-
tional care and not
only is the cutting of
trees, except under
certain restrictions,
prohibited, but the
greatest care is main-
tained to guard
against fires. In our
own country the gov-
ernment has recently
established a number of forest preserves which are carefully
patrolled, and here the destruction from forest fires is
rigidly guarded against. Great care of all forests should
be taken by hunters, campers, and all others who visit
them, and also by the railways passing through them.
Loggers and lumbermen should see that it is to their
GOOD FORESTRY
Notice how carefully the underbrush has
been removed to guard against fire.
SUMMARY 345
interest to maintain growing forests and not wantonly to
destroy them.
SUMMARY
The soils which have been produced in one way or another,
as described in Chapter X, are classified as local or sedentary
soil, which is formed from the rocks directly beneath it ; and
transported soil, which is generally brought from other
localities and deposited by water, ice, or wind. Soils are
also classified according to the size of their particles, as
gravel, sand, silt, and clay. The best agricultural soils are
generally of the consistency of silt, and are called loams.
Nitrogen, phosphorus, and potassium are the soil elements
that are used most freely by the growing plant, but these
elements must be in chemical compounds with other sub-
stances before they are available as plant food. Plants also
require air and water, and are dependent on the activities
of soil bacteria. These bacteria cause such changes in
organic matter of the soil that it may be used by the plant
as food. Partially decayed organic matter in the soil is
called humus. Humus is not only a source of plant food,
but also serves to mellow the soil and to conserve soil water.
The most common fertilizers are manures. They contain
nitrogen, potassium, and phosphorus in about the proportions
needed for ordinary crops. Commercial fertilizers contain
one or more of the elements mentioned, in varying pro-
portions. The United States is now developing its supplies
of commercial fertilizers and bids fair to be independent of
foreign supplies. The most common fertilizing agents are
the nitrogen-fixing bacteria, moles, gophers, and angleworms.
Some plants grow with their roots submerged in water,
while others can grow only where the moisture supply is
346 MAN'S USE AND CONSERVATION OF SOILS
scant. But most cultivated crops cannot live in a soil that
holds too much free water. Land must, therefore, be prop-
erly drained. If, on the other hand, drainage is too free,
it may wash the plant food out of the soil. Much more
moisture is lost by evaporation than by under-drainage or
seepage. In dry climates or during droughts, therefore,
mulches and frequent stirring of the top-soil must be
resorted to in order to conserve moisture.
Great areas in dry climates are frequently reclaimed by
irrigation, while swampy lands are rendered useful by drain-
age. In the conservation of soils, nothing is more important
than wise forestry. Forests retard evaporation of soil water,
increase the underground supplies of water, and tend to
prevent great extremes of high and low water in our rivers.
The ruthless destruction of our forests also threatens our
future lumber supply. Our own government has been taking
steps in recent years to care for our forests scientifically.
It deserves the cooperation in this of every good citizen.
QUESTIONS
Is the soil in your neighborhood local or transported? Does
its character vary much in different places ? Does its fertility vary ?
Are the soil particles large or small?
What would you suggest as the cause of any soil variations found
in your neighborhood?
What conditions are necessary to produce a fertile soil?
What are the best farmers doing to increase the fertility of their
soils?
How can the right amount of soil water usually be maintained ?
What steps should be taken to guard our forests ?
CHAPTER XII
THE SUN'S (HPT OP LIGHT
Light. — The sun is not only the source of almost all
the heat of the earth but also of its light. We have devel-
oped artificial self-luminous bodies such as candles, lamps,
electric lights, but none of these compares with the light
given by the sun. The stars also furnish a little light.
Light is just as essential to life as heat is. If plants or
animals are where light is entirely excluded, they begin
to sicken and die. If they are placed where it is very cold,
they freeze and die. Although the sun gives both heat and
light, yet these two are not inseparable. We feel the heat
given out by boiling water but there is no light, and we
see the light of the moon but there is no appreciable heat.
We usually say that we feel heat but cannot see it and see
light but cannot feel it.
Direction of Light Movement. — Experiment 100. — Point
the pinhole end of a camera obscura or pinhole camera (this con-
sists of two telescoping boxes, the
larger having a pinhole at the end
and the smaller a ground glass plate
(Figure 97)) at some object and move
the ground glass plate back and forth
until a sharp image of the object is FIGURE 97
formed. Sketch on a piece of paper
the object and the image, showing the direction in which you think
the rays of light must have traveled through the pinhole to form
the image.
347
348
THE SUN'S GIFT OF LIGHT
A photographic camera is constructed in the same way as this
little camera, only a lens is placed behind the pinhole to intensify
the image, and it is
possible to exchange
the ground glass plate
for a photographic
plate.
There are certain
properties of light
which seem readily
apparent from our
daily experiences.
We cannot see ob-
jects in the dark,
but if a light is
brought into the
room so that it can
shine upon them,
they become visible.
We see them be-
cause the light is
reflected to us from
them. All objects
except self-luminous
bodies are seen by reflected light. Most of the bodies that
we know are dark and non-luminous. Sometimes some of
these which have polished surfaces reflect the light from
a luminous body and thus appear themselves to be furnish-
ing light.
An example of this is often seen about sundown when
the sunlight is reflected from the windows of a house, mak-
ing them look as if there were a source of light behind them.
A LAKE MIRROR
THE INTENSITY OF LIGHT
349
Any dark body whose surface reflects light appears itself
to be luminous as long as the source of light remains, but
grows dark again when the source is removed. This is
the case of the moon. At new moon, the moon is so situated
with respect to the sun that light is not reflected to the earth
and we cannot see it. At full moon, half of the moon's
entire surface reflects the sunlight, and it appears very
bright.
If a candle is held in front of a mirror and we look into
the mirror, we see the candle behind it. We know that
the candle is not there but that its light is reflected by the
mirror in such a way as to make it appear to come from
behind the mirror. We see the candle by the light the mirror
reflects.
If we wish to see whether the edge of a board is straight,
we sight along it. If we wish to hit an object with a bullet,
we bring the rifle barrel into our line of sight. We there-
fore feel, confident that if light is traveling through a uniform
medium, such as air usually is, it goes in a straight line.
The Intensity of Light. — Experiment 101. — Take two square
pieces of paraffin about an inch thick, or better two squares of paro-
wax, and place back to back
with a piece of cardboard
or tinfoil between them.
When a light is placed on
either side of this apparatus
the wax toward the light
will be illuminated, but not
that on the other side of
the cardboard. (Figure 98.)
If lights are placed on each side, it is easy to see when both pieces
of wax are equally illuminated, or receive the same amount of
light. In this way the strengths of lights can be compared.
Place a candle about 25 cm. in front of one side of this apparatus,
FIGURE 98
350
THE SUN'S GIFT OF LIGHT
and 4 candles, placed close together on a piece of cardboard so that
they can be readily moved, about 90 cm. away on the other side.
Move these candles back and forth till a position is found where
both pieces of wax are illuminated alike. Measure the distance
of the four candles from the wax. How many times as far away
are they as the one candle ?
The brightness of the sun's light is so great that even an
arc light placed in direct sunlight appears as a dark spot.
So great, however, is the sun's distance that the earth re-
ceives only a minute portion, less than one two-billionth, of
the light and heat it gives out.
The standard measure for intensities of light is the candle
power. This is the light given out by a standard candle,
FIGURE 99
which is practically our ordinary No. 12 paraffin candle.
The ordinary incandescent electric light is sixteen candle
power. No comprehensible figures will express the intensity
of the sun, using the candle power as a measure.
The intensity of light, like that of heat and electricity,
and all forms of energy which spread out uniformly from their
point of origin, varies inversely as the square of the distance
from the source. This rapid decrease in the brightness of
light as the distance increases is the reason why so small a
change in the distance of a lamp makes so great a differ-
ence in the ease with which we can read a book. If we
make the distance to the lamp half as great, we increase
REFLECTION OF HEAT AND LIGHT
351
the amount of light on the book four times ; if one third
as great, nine times. (Figure 99.)
Reflection of Heat and Light. — Experiment 102. — In a dark-
ened room reflect by means of a mirror a beam of light from a small
hole in the curtain, or from some artificial source of light, on to
a plane mirror lying flat upon a table. If there is not sufficient
dust in the air to make the paths of the rays apparent, strike two
blackboard erasers together near the mirror. Hold a pencil ver-
tical to the mirror at the point where the rays strike it. Compare
with each other the angle formed by each ray with the pencil.
Raise the edge of the mirror, and notice the effect on the reflected
ray. Place the pencil
at right angles to this
new position of the
mirror, and compare
the angles in each case.
How do the sizes of the
angles on either side of
the pencil compare ?
It has already been
stated that the moon
shines by reflected
light. It is a matter
of common observa-
tion that objects on
the earth reflect both
heat and light. In
the summer, the
walls of the houses
and the pavements
of the streets sometimes reflect the heat to such an extent
that it becomes almost unbearable. In countries where
the sun shines brightly nearly all of the time, as in the
Desert of Sahara, reflectors have been so arranged as
A REFLECTION ENGINE
This engine uses the rays of the sun instead
of coal in heating its boiler.
352 THE SUN'S GIFT OF LIGHT
to reflect the heat of the sun on to boilers to run steam
engines.
The smooth surfaces of houses often reflect so much of
the light falling upon them that the glare is thrown into
the windows of surrounding houses into which the sun
itself cannot shine. If one stands in the right position, the
reflection of trees and other objects can be seen in a smooth
lake. But the reflection cannot be seen if the position of
the spectator is much changed. The reflected ray must
therefore maintain a certain relation to the ray that strikes
the surface from the object.
In Experiment 102, when the pencil was held perpen-
dicular to the mirror at the point where the rays touched the
mirror, it was seen that both
the ray from the window and
the reflected ray made about the
same angle with it. These two
FIGURE 100 angles are respectively called the
angle of incidence and the angle
of reflection. By most careful experimentation it has been
found that the angles between each of these two rays, and
the line drawn perpendicularly to the reflecting surface
are always equal, or in other words the angle of reflection
is always equal to the angle of incidence. (Figure 100.)
This explains why, if you are standing in a room at
one side of a mirror, you can see in the mirror only the
opposite side of the room. We are accustomed to a
similar law of reflection when we bounce a ball on the floor
for some one on the opposite side of the room to catch.
The Speed of Light. — In the latter part of the seven-
teenth century a Danish astronomer by the name of Roemer,
REFRACTION OF LIGHT 353
after carefully watching the brightest of Jupiter's satellites
or moons as it revolved around the planet, noticed that the
time of occurrence of its eclipses or passages behind the
planet showed a peculiar variation. He accurately deter-
mined the interval between two eclipses or the time it took
for a complete revolution of the satellite around the planet.
Using this interval he computed the time at which other
eclipses should take place and found that as the earth
in its revolution around the sun moved away from Jupiter
the eclipses appeared to take place more and more behind
time. Determining the exact time at which an eclipse
took place when the earth was
nearest to Jupiter, and comput-
ing the time an eclipse should
take place six months later when
the earth was farthest from Jupiter,
he found that the actual time of
the eclipse was 22 minutes behind FIGURE 101
the computed time. This slow-
ness he said must be due to the time required by the light
in crossing the earth's orbit. (Figure 101.)
Many determinations of this kind have been made since
those of Roemer, and it has been found that he was some-
what in error, as the time required by light in traveling
across the earth's orbit is about 16 minutes and 40 seconds,
or 1000 seconds. Since the diameter of the earth's orbit
is about 186,000,000 miles the speed of light must be about
186,000 miles per second. Determinations of the speed
of light have been made in several other ways with almost
like results.
Refraction of Light. — Experiment 103. — Place a penny in the
center of a five-pint tin pan resting on a table. Stand just far
354 THE SUN'S GIFT OF LIGHT
enough away so that the farther edge of the penny can be seen over
the edge of the pan. Have some one slowly fill the pan with water.
How is the visibility of the penny affected ?
(Figure 102.)
Experiment 104. — Fill a tall jar about
two thirds full of water. Place a glass rod
or stick in the jar. Does the rod appear
straight ? Pour two or three inches of kero-
sene on the top of the water. What effect
does this have on the appearance of the rod ?
FIGURE 102 Experiment 105. — Hold an ordinary spec-
tacle lens such as is used by an elderly
person, or any convex lens, between the sun and a piece of paper.
Vary the distances of the lens from the paper. The heat and
light rays from the sun are bent so that they converge to a point.
Try the same experiment with a lens used by a short-sighted
person, or a concave lens. This lens does not have the same effect
as the convex lens. The rays are made to diverge. Why cannot
long-sighted and short-sighted persons use the same glasses ?
In the experiment of the penny in the dish, the water
in some way bent the ray of light and made the penny
come into the line of sight when it could not be seen before
the water was there. The penny was apparently lifted up.
This illustrates why ponds and streams look shallower
than they really are. This experiment shows that when
light is passing from one medium to another it does not
always travel in the. same straight line. Certain media
offer more resistance to the passage of light than others and
are called denser media. It is this difference of resistance
which causes the bending of the ray.
Suppose that a column of soldiers marching in company
front are passing though a corn field and come obliquely
upon a smooth open field. (Figure 103.) The men as they
come on to the open field are unencumbered by the corn-
LENSES
355
FIGURE 103
stalks and will move faster, and thus the line of march will
swing in toward the edge of the corn field. It can easily be
seen that the bending of the line would be in the opposite
direction if the soldiers were
marching from the smooth field
into the corn field. If the com-
pany front were parallel to the
edge of the corn field, then the
men would reach the open field
at the same time and there
would be no swinging of the line.
The above illustration roughly explains what happens
when light passes from one medium to another. Refrac-
tion is the name given to this bending of light in passing
through different media or through a medium of changing
density. Twilight, mirage, the flattening of the sun's
disk at the horizon, and other appearances, we shall find
later, are due to this property of light.
Lenses. — The bending of light in passing from one
medium to another has been turned to great advantage in
the use of lenses. In the
making of lenses, trans-
parent substances are so
shaped that when the rays
of light strike them, they
are bent into any desired
direction. Experiment 105
shows that the rays may be brought nearer together
(converged or focused) or spread farther apart (diverged).
If the illustration of the line of march of the soldiers is
kept in mind, it will be seen that the rays must always
356
THE SUN'S GIFT OF LIGHT
FIGURE 105
be bent toward the thicker part of the lens. (See Figures
104 and 105.)
If in Experiment 100 a convex lens is placed behind the
small hole, the rays of light from a large area will be focused
on the ground glass. If the
plate is adjusted to the right
- position, a small, distinct picture
will be formed. If a plate cov-
ered with chemicals that undergo
change when exposed to light
replaces the ground glass, a
copy of the picture is left upon the plate. When this is
developed by chemical process, permanent pictures may be
printed from it. This is what is done in photography.
In the magnifying glass (Figure 106) the eye is placed near
the lens and the rays from a small object are so bent that
they appear to be
spread apart and to
come from a much
larger object. The re-
fracting telescope and
the compound micro- FIGURE IOG
scope (Figure 93) are
combinations of magnifying lenses so adjusted as to produce
the largest possible clear image of the object examined.
Light and Color. — Experiment 106. — Darken the room except
for a small hole in the curtain where sunlight may enter. Allow
the sunlight to pass through a glass prism and to fall upon a white
wall or a piece of white paper. How has the white sunlight been
affected? Where did the colors come from? In what order are
the colors arranged ?
Hold a piece of red glass close to the prism and between the prism
LIGHT AND COLOR
357
and the wall or paper. Do all the colors of the spectrum still
appear ? Repeat the experiment with glasses of other colors. What
happens?
It was seen in Experiment 106 that when white light is
passed through a prism it not only suffers a change in direc-
tion (is refracted), but it is also separated into different
colors. White light must then be made up of lights of
different colors, and the prism must have affected these
colors so that each was bent to a different extent in passing
through the glass. (Figure 107.) Careful experiments show
\
FIGURE 107
that light is a form of wave motion, and that the infinitesi-
mally small wave-lengths of the various colors differ from
one another. The colors are refracted differently in passing
through the prism and are therefore separated from one
another. The band of colors into which white light is
separated by the prism is called the spectrum.
It was also seen that if the light from the prism was passed
through red glass, all the colors except the red were cut off,
or absorbed. If we could have made a careful test of the
glass we should have found that it had been warmed by the
absorption of these colors; that is, the energy of light had
been transformed into the energy of heat. When light is
358 THE SUN'S GIFT OF LIGHT
absorbed its energy is changed into heat energy or chemical
energy.
Experiment 107. — Obtain pieces of cloth of a number of different
colors. Darken the room and light a Bunsen burner. Adjust
the holes at the bottom so that it will give but little light. Dip a
glass rod in a solution of common salt and place it in the flame of
the burner. The flame will be colored a brilliant yellow. Now
examine the colors of the different pieces of cloth. Do they appear
as they did in sunlight?
The color of a non-luminous substance is due to the kind
of light it transmits or reflects. If a colored object is looked
at by lamplight it will not appear of the same color as by
sunlight because the lamplight is deficient in some of the
colors of sunlight. Therefore the object cannot reflect the
same combination of colors when exposed to lamplight
that it reflects when exposed to sunlight.
If, for example, an artificial light lacks red rays, then
a red surface exposed to it would absorb all the colors of
the light and would appear black because there are no red
rays to be reflected.
By combining the prism with the telescope, scientists
have an instrument for examining the spectrum of the sun.
With this instrument the spectrum is found to be crossed
by hundreds of fine black lines scattered along the band of
color. By bringing known elements to a white hot vapor
and comparing their spectra with the spectrum of the sun,
scientists have determined many substances that are in the
sun.
Sunlight is affected by the air through which it comes.
When the sun sets at night and the rays come to us through
a great thickness of murky air which is near the surface of
the earth, the light often appears red or yellow. The heavy
LIGHT AND COLOR 359
dust and smoke in the air has absorbed the other colors
and has transmitted one of these two. On the top of a
high mountain or on a clear day, or when the sun is high
overhead, the sky appears blue. When the particles of
matter in the atmosphere through which light is coming are
TELESCOPE EQUIPPED WITH A SPECTROSCOPE
It is with instruments like this that astronomers have been able to
determine the composition of the sun.
very minute, blue is the color reflected. A blue sky in-
dicates a clearer atmosphere.
Sometimes after a shower an arch appears in the heavens,
composed of beautiful colors; we call this a rainbow. In
this case the sunlight is broken into different colors by the
drops of water which still fall in the distance, just as it is
when passing through a prism.
360 THE SUN'S GIFT OF LIGHT
Sometimes the sun or moon is surrounded by bright
rings called, when of small diameter, coronas, and when of
great diameter, halos. These rings are due to the effect
of water or ice particles on the light coming from the sun
or the moon.
Under certain conditions it may happen that light com-
ing from objects at a distance is so refracted and reflected by
the layers of air of different density, through which it comes
LICK OBSERVATORY
As light is affected by the atmosphere, observatories must be placed
where atmospheric conditions are the best. This famous observatory
is on a mountain in the clear air of California.
to the eye of the observer, that objects appear to be where
they are not, like the image of a person seen in a mirror.
This phenomenon is called mirage or looming. It occurs
most frequently on deserts and over the sea near the coast.
Sometimes in high latitudes arches and streamers of
colored light are seen illuminating the northern sky. The
brilliancy and colors of the illumination vary. Sometimes
it is bright enough to be seen even in the daytime. This
display is called the aurora borealis or " northern lights "
LIGHT AND COMFORT 361
and is believed to be an electrical phenomenon in thin air.
The heights of the streamers have been calculated to be more
than a hundred, perhaps several hundred miles, so that it is
probable that air in a rare condition extends to this elevation.
Theories Concerning Light. — Although it is very easy
to perceive light and to examine many of its properties,
yet to determine just what it is that produces the light
sensation has been found vastly difficult. Sir Isaac New-
ton thought that light consisted of streams of very mi-
nute particles, or corpuscles, thrown off by the luminous
body. Since about 1800, it has been considered a form
of wave motion which is transmitted through the ether
which fills all space.
Light and Comfort. — In early days when few people were
able to get glass for windows, houses were dark and gloomy.
At present, however, glass is cheap and there is no reason
why houses should not be well lighted. Few houses are
built nowadays without making generous allowance for
window space. All modern manufacturing buildings have
the major part of their outside walls devoted to windows.
Hospitals are so planned that every possible room may have
direct sunshine for at least a part of every day. We are
beginning to appreciate the value of abundant sunlight.
Dampness and darkness are the two conditions favorable
to the growth and activity of bacteria. Few disease germs
can live if exposed to the direct light of the sun. No house
can have too much sunlight. There should be no dark
corners to harbor germs. Kitchen cupboards and sinks
should be so located, if possible, that they may receive direct
sunshine. Bedclothes, rugs, hangings, clothing, should all
be exposed to the bright sunlight as often as possible. Sun-
362
THE SUN'S GIFT OF LIGHT
light not only kills disease germs; it also banishes gloom
and stimulates cheerfulness. Cheerfulness itself is a genuine
health tonic.
Up to about fifty years ago whale oil and candles furnished
the best artificial lights obtainable. It is difficult for us to
appreciate how numerous are the advantages and how much
HOSPITAL WARD
Showing the great care taken to secure light, air, and cleanliness.
greater the power of illumination when kerosene, gasoline,
acetylene, illuminating gas, and electricity are used. In
many sections of our large cities artificial lighting almost
turns night into day. So enormous is the amount of fuel
used for the brilliant lighting of our cities that the United
States Government was compelled to combine " lightless
nights " with " daylight saving " in the interest of fuel
economy during the World War.
LIGHT AND COMFORT
363
Because of the brilliancy of many modern artificial lights,
their inferiority to sunlight is often overlooked. It is very
difficult to arrange artificial lights in libraries, schools,
and public halls so that work may be carried on with as
great ease in one section of the room as in another. Un-
shaded high-power lights may furnish sufficient illumina-
tion, but the effect is too dazzling. Scattered low-power
lights give a more uniform and less trying illumination.
Where central lights are to be used,
translucent bowls which diffuse some of
the light to the room and reflect some
to the ceiling probably give the best
results for general purposes.
It must be remembered that if the
walls and furnishings of a room are dark
in color much of the light will be ab-
sorbed and little reflected, and even
bright lights will illuminate the room
only in their immediate vicinity. Deco-
rators have this fact in mind when they
recommend lighter walls and hangings for north rooms than
for south rooms.
Whatever kind of illumination is provided, the person
using it must be careful not only that his work shall be
properly lighted but also that his eyes shall be protected
against direct glare. Too much care cannot be taken of the
eyes. No arrangement of artificial light is as easy on the
eyes or as reliable as daylight, where colors are to be worked
with or where careful measurements or minute adjustments
are to be made. In work of this kind, rooms with windows
on the north side, through which only diffused light will
come, are preferable to rooms lighted by south windows.
AN OLD WHALE
OIL LAMP
364 THE SUN'S GIFT OF LIGHT
SUMMARY
The sun is the source not only of almost all the heat of the
earth but also of practically all its light. Light is just as
essential to life as heat is. No comprehensible figures will
express the intensity of the sun's light, using the candle
power as a measure. The intensity of light varies inversely
as the square of distance from its source.
All objects except self-luminous bodies are seen by re-
flected light. Objects on the earth reflect both heat and
light. The angle at which a ray of light is reflected is equal
to the angle at which the ray strikes the reflecting surface.
Light travels at the rate of about 186,000 miles per second.
When it travels through a uniform medium, it goes in a
straight line; but when it travels through media of
varying densities the rays are bent or refracted. The
bending of light rays in passing from one medium to
another is turned to great advantage in the use of lenses
which may be so constructed as to bend rays of light in any
desired direction.
When a ray of white light is passed through a prism, it is
not only refracted but is also separated into different colors.
Light is a form of wave-motion, and the infinitesimally
small wave-lengths of the various colors differ from one
another. This accounts for the different degrees of bending
of the various color rays when passed through a prism. The
band of colors into which white light is separated is called
the spectrum. The color of a non-luminous substance
depends on the kind of light it transmits or reflects. When
a substance is brought to a white-hot vapor, it has a char-
acteristic spectrum. By combining the prism with the
"telescope, scientists have an instrument called a spectroscope,
QUESTIONS 365
by means of which many of the substances in the sun have
been detected.
Changing conditions of the atmosphere affect the colors
of sunlight in various ways. Rainbows, halos, coronas,
and mirages are owing to peculiar conditions of the atmos-
phere, through which light is coming to the eye.
Natural and artificial lighting of houses deserves the most
careful consideration, for the sake of convenience, comfort,
and health.
QUESTIONS
What experiences have you had which cause you to think that
light travels in a straight line?
If a boy is reading two feet from a light and moves to a distance
of eight feet, how much ought the strength of the light to be in-
creased to enable him to read with the same ease?
How long does it take light to come from the sun to the earth ?
What experiences have you ever had which illustrate refraction ?
Why do not colors look the same in artificial light as they do in
sunlight ?
How would you arrange the windows, hangings, and artificial
lights of a room to make it most healthful and cheerful?
CHAPTER XIII
LIFE ON THE EAETH
Plants and Animals. — Plants and animals are com-
binations of the earth's elements endowed with life. By
means of the sun's energy they are able, the plants directly
and the animals indirectly, to do both internal and external
work which results in growth, reproduction, and other ac-
tivities. Since plants and animals are entirely dependent
upon the earth and sun for their existence, they, like other
earth and sun phenomena, should be studied in this course.
Plants. — Although in their lower microscopical forms it
is very difficult to distinguish between plants and animals,
yet the forms ordinarily seen differ greatly. Most plants
are fixed and consist of root, stem, and leaves, while most
animals are movable and possess a variety of different parts.
But some plants, like the seaweeds, appear to have no roots ;
some, like the dandelion, no plant stem, and some, like the
cactus, no leaves.
If we dig around the base of a tree, we find in the soil a
network of roots holding firmly erect a pillar-like stem with
branches bearing a profusion 6f leaves. If we examine these
divisions carefully, we shall find that each has a distinct part
to play in the life work of the tree. We shall also find (1) that
plants as well as animals need air, water, and other kinds of
food, (2) that plants and animals take in, digest, and assimi-
late food, and (3) that each in the higher forms has parts
366
PLANT ROOTS
367
which are particularly
adapted for doing these
different kinds of work.
Plant Roots. — Plant
roots usually secure the
plant to the ground so
that the stem may be
supported. They also
take up food from the
soil and pass it on to
the rest of the plant.
In most plants all the
foods except carbon and
a part of the needed
oxygen are taken in by
the roots. The soil ele-
ments that the plants
must have are nitrogen,
potassium, calcium, mag-
nesium, phosphorus, sul-
phur, and iron. Water
supplies hydrogen and
oxygen ; while carbon,
another necessary ele-
ment, is taken from
carbon dioxide of the
air. The soil elements
must be in soluble chemical combinations, such as nitrates,
phosphates, sulphates, and so on.
Experiment 108. — Fill three 2-quart fruit jars each about half
full of distilled water. Add to the water in the first of these
THE GRIZZLY GIANT
The monarch of all plants, 93 feet around
the base. Notice the cavalry at the foot.
368
LIFE ON THE EARTH
gram of potassium nitrate, \ gram iron phosphate, ^ gram cal-
cium sulphate, and -£fo gram magnesium sulphate. Add to the
water in the second jar the same ingredients with the exception
of the potassium nitrate. Replace this by
potassium chloride. Add nothing to the
water of the third jar. Put the three jars
where they will receive plenty of sunlight
and warmth and place in each a slip of
Wandering Jew about 10 inches long. Note
which slip grows the most thriftily. In the
third jar there is no mineral food, in the
first all of this food which is necessary, and
in the second all the necessary food except
nitrogen.
In Experiment 108, it was found that
in the distilled water the plant made
but little growth. Water and air
alone are not sufficient. It did not
thrive when the nitrogen was lacking,
but grew very well when all the neces-
sary elements were present. All plant
foods, however, must be in dilute solu-
tion before plants can appropriate
them.
Experiment 109. — In another fruit jar
make a very strong solution of potassium
nitrate or, as it is commonly called, salt-
peter. Place in this a slip of Wandering
Jew as was done in the previous experiment.
Does the slip grow well? It has a great
abundance of nitrogen, which was found so important. Place in a
similar strong solution a growing beet or radish freshly removed
from the ground. Notice how it shrivels up. Place a similar
beet or radish in water. It is not similarly affected. What is the
effect of strong solutions on plants?
A TYPICAL PLANT
Showing root, stem, leaf,
and flower.
PLANT ROOTS
369
ROOTS SECURELY HOLDING THE TREE ERECT
If the solution is too strong, as seen in Experiment 109,
the plant cannot use it. This is the reason many alkali
soils will not support
plants. The alkali
salts are so readily
soluble that the soil
water becomes a solu-
tion stronger than the
plants can use.
Experiment 110. —
Place three or four
thicknesses of colored
blotting paper on the
bottom of a beaker.
Thoroughly wet the
paper and scatter upon
it several radish or other seeds. Cover the beaker with a piece of
window glass and put in a warm place. Allow it to stand for
several days, being sure to keep the blotting paper moist all the
time. When the seeds have sprouted, examine the rootlets, with
a magnifying glass or low power microscope, for the
root hairs which look like fuzzy white threads. Touch
the root hairs with the point of a pencil. They can-
not, like the rest of the root, stand being disturbed.
On what part of the plant root do the root hairs grow?
As the blotting paper dries, what happens to the root
hairs?
Plant roots are enabled particularly by the
little root hairs (Figure 108), which were ex-
amined in Experiment 110, to take the film of
FIGURE 108 water which surrounds the soil particles and carry
this water to the stem and, through it, to the
leaves. The water which the roots take from the soil is a
dilute solution containing the plant food substances. Not
370 LIFE ON THE EARTH
only do roots absorb the water from the soil, but they se-
crete weak acids which aid in dissolving the mineral sub-
stances which the plants need. This can be seen where
plant roots have grown in contact with polished surfaces,
such as marble. These surfaces are found to be etched.
Experiment 111. — Cut a potato in two. Dig out one of the
halves into the shape of a cup and scrape off the outside skin.
Fill the potato cup about f full of a strong solution of sugar. Mark
the height of the sugar solution by sticking a pin into the inside of
the cup. Place the cup in a dish of water. The water should
stand a bit lower than the sugar solution in the potato
cup. After the cup has stood in the water for some
time, notice the change in the height of the denser
sugar solution.
Experiment 112. — Bore a f-inch hole 3 or 4 inches
deep in the top of a carrot. Scrape off the outside
skin and bind several strips of cloth around to keep
the carrot from splitting open. Fit the hole with a
one-hole rubber stopper having a glass tube about 1
meter long extending through it. (Figure 109.) Fill
the hole in the carrot with a strong sugar solution
colored with a little eosin and strongly press and tie
in the stopper. The sugar solution will be forced a
short distance up the tube by the insertion of the stopper. Mark
with a rubber band the height at which it stands. Submerge the
carrot in water and allow it to stand for a few hours. Mark
occasionally the height of the column in the tube. Taste the
water in which the carrot was submerged. There has been an
interchange of liquids within and without the carrot.
The plant root takes up its water in the same way the
water was taken into the sugar solution of the potato cup
or of the carrot. The water or sap within the substance
of the root is denser than the soil water, just as the sugar
solution was denser than the water outside. It has been
found that whenever two liquids or gases are separated
PLANT ROOTS
371
by an animal or plant membrane, there is an interchange
of the liquids or gases, the less dense liquid or gas passing
through more rapidly. This is called osmosis and is of
the greatest importance to both plants and animals.
All animals and plants are made up of exceedingly minute
parts, called cells. Figure 110 shows the cells in a leaf and the
leaf hairs greatly magnified. The higher plants and animals
are composed of vast numbers of these cells. The cell
usually has a thin cell
wall, which in living and
growing cells incloses a
colorless semi-fluid sub-
stance called protoplasm.
This protoplasm is the
living part of the plant.
It is found in all the cells
where growth is taking
place, where plant sub-
stances are being made,
or where energy is being
transformed. It has the power of dividing and forming
new cells, and it is in this way that the plants grow.
The little root hairs are one kind of plant cells. They
consist of a thin cell wall within which is protoplasm and
cell sap, a solution of different plant foods. Since the pro-
toplasm and cell sap are denser than the soil water, more
liquid moves into the cell than from it. A little of the
cell solution does move out, however, and it is this which
helps to dissolve the soil particles. The protoplasm in the
cell regulates to some extent the interchange of liquids.
Experiment 113. — Cut off the stem of a thrifty geranium, be-
gonia, or other plant an inch or two above the soil. Join the plant
FIGURE 110
372
LIFE ON THE EARTH
stem by a rubber tube to a glass tube a meter long, of about the
same diameter as the stem. See that the rubber tube clings
strongly to both glass tube and stem. It may be best to tie it
tightly to these. Support the glass tube in a vertical position
above the stem and pour into it sufficient water to rise above the
rubber tube. (Figure 111.) Note the position of the
water column. Thoroughly water the soil about the
plant. Watch the height of the water column, marking
it every few hours.
The water taken in by the roots passes on
from cell to cell by osmotic action and rises in
the stem in the same way that the water rose
in the tube attached to the stem of the growing
FIGURE in plant m Experiment 113. The root pressure,
together with capillarity, as seen in Experiment 97, will
account for the rise of the sap in lowly plants, but the cause
of the rise of the sap to
the top of lofty trees is
difficult to understand.
Roots extend them-
selves through the soil
by growing at the tips.
Here the cells are rapidly
dividing, forming new
cells, and building root
tissue. As water is so
essential, they are always
seeking it and extending themselves in the direction where
it is to be found. This causes them to extend broadly and
to sink deeply (Figure 112). A single oat plant has been
found to have an entire root extension of over 150 feet.
This seeking of the roots for water sometimes causes the
roots of trees to grow into drain pipes and stop them up.
FIGURE 112
STEMS 373
For this reason the planting of certain. trees near sewer pipes
is often prohibited.
Experiment 114. — Boil some water so as to drive out the air and
after it has become cool fill a 2-quart fruit jar half full. Dissolve
in this all the necessary plant food as was done in Experiment
108, making the solution the same strength. Place in this a slip
of Wandering Jew. Pour over the surface of the water a layer
of castor oil or sweet oil. Place this jar alongside the slip in the
other complete food solution, Experiment 108. Both slips have
the same conditions except that the oil keeps out the air from the
roots of one of them. Does the absence of air affect the growth of
the slip?
As the tips of the roots are delicate, it can be readily seen
that if they are to grow readily the soil around them must
be mellow. It was seen in Experiment 114 that if roots
are to grow they must have air, another reason for keep-
ing the soil mellow.
Roots are, however, not simply absorbers of water and
dissolved food. Some of them act as storehouses for the
food that the plant has prepared for future use. Beets,
carrots, parsnips, turnips, and sweet potatoes are examples
of roots which store food ready for the rapid growth of
the next year's plant.
Stems. — Experiment 115. — Examine a corn stalk. Notice how
and where the leaves are attached to the stem. Do the alternate
leaves come from the same side of the stem? Cut a cross section
of the stalk. Notice the outside hard rind, the soft pithy material,
and the small firmer points scattered about in the pith. Cut a
section lengthwise of the stalk and notice how these small firmer
points are related to the lengthwise structure of the stem.
Cut off a young growing corn stalk and place the cut end in
water colored by eosin or red ink. Allow it to stand for some time
and then cut the stalk off an inch or two above the surf ace of the
water. How have " the firmer points " been affected? If possible,
374
LIFE ON THE EARTH
make the same observations
and experiments on the stem
of a small seedling palm tree.
Experiment 116. — Ex-
amine a piece of the growing
young stem of a willow, apple
tree or other woody stem
that shows several leaf scars.
Is the arrangement of the
leaves the same as in the corn
stalk? Cut a cross section
of this stem and examine it.
Does it resemble the cross
section of the corn stalk?
Strip off a piece of the bark
and compare it with the rind
of the corn stalk. Examine
carefully the smooth, slippery
surface of the wood just be-
neath the bark. This is the
cambium layer.
Examine the firm wood
beneath this layer. Where is
the pith in this stem? With
a lens you may be able to
see lines radiating from the
pith to the circumference of
the stem. These are called
the pith rays. Cut a length-
wise section of the stem and
examine it. Are there any
fiberlike bundles as in the
corn stalk? Cut off a piece
of the stem already examined
having the bark on it, or a piece of sunflower stem, and place the
end of it in colored water. Allow it to remain for some time and
.then cut a cross section above the point where it was in the water.
A PINE TREE
Notice the erect position of the stem.
STEMS 375
Has the water risen and colored this cross section as it did the cross
section of the corn stalk?
Stems vary greatly in the positions they assume. Some
rise firmly erect from the root, like the oak and the pine;
some cling to supports, like the grape and the ivy ; some
twine around supports, like the bean; some creep upon
the ground, like the strawberry; some grow in
the form of a thickened bulb like the onion
(Figure 113) ; some, like the cacti, assume a
fleshy, leaflike, though leafless form; some, like
the nut grass, Johnson grass, and witchgrass, FlGURE 113
grow underground and send up shoots, and some
stems store up food underground in tubers, like the potato
(Figure 114), from which the next year's
plant may grow.
Notwithstanding all the diversity shown
by the stem, its principal functions are
to support the leaves, so that they will
best be exposed to the light, and to con-
duct the food solutions from the root to the leaves. The
part of the stem through which the cell sap flows was seen
in Experiments 115 and 116.
There are two great types of stems, one represented by
the corn stalk and palm and the other by the willow, sun-
flower, and bean. On account of the structure of the seeds
these are called, respectively, monocotyledonous (one seed
leaf) and dicotyledonous (two seed leaves). That these
differ greatly in their appearance was seen in Experiments
115 and 116, where the two kinds of stems were com-
pared. It was also found in these experiments that, in
the first, the red colored water that took the place of
the sap rose in the fibrous bundles scattered through the
376
LIFE ON THE EARTH
pith, while in the second it rose through the woody tissue
within the bark.
Experiment 117. — Examine a cross section of a hardwood tree
several years old, -and if possible of a palm. Notice the ringlike
arrangement of the layers in one and the absence of all such arrange-
ment in the other.
In Experiment 117, when the cross section of a dicoty-
ledonous tree was examined, it was found to be composed
of circular rings, but no such rings are found in the cross
A SPLENDID TREE DEVELOPED UNDER IDEAL CONDITIONS
section of the monocotyledonous tree. When later we
examine the seeds of beans and corn, we shall find that
they also differ very much.
When the bark is removed from a stem, like the willow
or apple, the soft, smooth layer underneath is found to be
STEMS
377
BANYAN TREE
Some of the branches descend and take root in the ground and so appear
like stems.
composed of living cells. This is called the cambium layer.
During the season of growth, these cells are continually
subdividing and forming new cells, thus adding a ring to the
thickness of the stem.
The age of a tree can be
determined by counting
these rings. No such
layers are found in the ^>F^P \ ff IM FT
monocotyledonous stems.
Grafting (Figure 115) and
budding (Figures 116 and
117) are processes of bringing the cambium layers of two
trees of similar kinds in contact and keeping them pro-
tected so that they will grow together. In this way,
many of our finest species of fruit are propagated. In
FlGURE 115
378
LIFE ON THE EARTH
fact, fruit trees raised from seed are not exactly like the
parent tree, and if trees are to be true to variety they must
be propagated in this way.
Experiment 118. — Examine several growing stems or twigs which
have buds upon them and notice how the buds are arranged. Is the
arrangement the same in all? If these buds grew into twigs or
leaves, would they shade one another ? Is there a bud at the end
of the twig or stem ?
If we examine the tip of a growing stem or twig, we
shall find a bud. In most of the trees and shrubs of tem-
perate regions a terminal bud is formed at the close of
FIGURE 116
the growing season, and from this the shoot continues to
grow the following season. Buds are also found along
the length of the stem and branches, as was seen in Ex-
periment 118. These are lateral buds and, since they are
usually found in the axis of the leaf, at the angle formed
by the leaf and stem, they are called axillary. In some
trees the terminal buds die at the end of the growing season,
LEAVES
379
and the next year's growth is due to one of the axillary
buds.
Leaves. — If we examine the arrangement of the leaves
on a plant or tree, we shall see that ,they do not lie one
directly above the other, but that they are so arranged as
not to shade one another. Their position generally is such
that the broad upper surface of the leaf receives the strong
light rays perpendicu-
larly upon it. To ac-
complish this, the leaves
in many trees are ar-
ranged spirally around
the stem.
The stem of the leaf
itself, in some parts of
the tree, often grows
long and twists about,
in order to push the leaf
out to the light and yet
not let it be wrenched
away by the wind. The
horse-chestnut is such a
leaf. In some plants,
like the sunflower, the younger leaves follow the sun all
day. In other plants the rays of the sun seem to be too
bright in the middle of the day and the leaves are then held
edgewise to the light.
A striking example of this is the compass plant, the
leaves of which arrange themselves so that the sun's rays
strike the broad surface of the leaves in the evening and
morning when the rays are not very strong, but at noon the
DIFFERENT FORMS WHICH LEAVES
ASSUME
380
LIFE ON THE EARTH
FIGURE 118
edge of the leaf is toward the sun, the leaf thus maintaining
a nearly vertical position all day, with its greatest length
extending in a nearly north and south line.
It is the effort to regulate the amount of
light falling on the leaf, and not any mag-
netic influence, which causes the leaf to
point in the direction of the compass needle.
The shapes of the leaves vary greatly in
different plants. Sometimes they assume
very singular forms, as in the pitcher plant
(Figure 118) and Jack-in-the-pulpit. Some-
times they even become carnivorous, as in
the sundew and Venus flytrap.
Around the margin of the sun-
dew leaf and on the inner sur-
face are a number of short
bristles, each having at the end
a knob which secretes a sticky
liquid. As soon as an insect
touches one of these knobs, it
sticks to the knob and the other
bristles begin to close in upon
the insect and hold it fast. Soon
the insect dies and the leaf se-
cretes a juice which digests the
soluble parts of the insect.
In the Venus flytrap (Figure
119) the leaf terminates in a
portion which is hinged at the
middle and has on the inside
of each half three short hairs, while the outside is fringed
by stiff bristles. As soon as an insect touches the hairs,
FIGURE 119
LEAVES
381
FIGURE 120
the trap closes rapidly upon it and stays closed until
as much as possible of the insect is digested, when the
trap again opens. Carnivorous plants of this kind usually
grow in places where it is difficult to get nitrog-
enous foods. As nitrogen is absolutely neces-.
sary for the growth of protoplasm (page 371)
these plants may have had to adopt this way
to supply the need.
Some leaves extend themselves into spiny
points, like those of the thistle (Figure 120), in
order to keep animals from destroying the plant,
or they may develop a sharp cutting edge, like
some grasses, or emit a bad odor, or have a repugnant,
bitter taste.
The veins or little ridges extending through the leaf from the
leaf stem vary (Figure 121). Sometimes these veins extend
parallel to one another
through the leaf, as in
the corn and palm. This
is generally characteris-
tic of monocotyledonous
leaves. In other leaves,
the veins form a network,
as in the maple and apple.
This is characteristic of
dicotyledonous plants.
Experiment 119. — Place
the freshly cut stem of a
white rose, white carnation, variegated geranium leaf, or any thrifty
leaf which is somewhat transparent, in a beaker containing slightly
warmed water strongly colored with eosin. Allow it to remain for
some time. The coloring matter can be seen to have passed up
the stem and spread through the leaf or flower.
FIGURE 121
382 LIFE ON THE EARTH
The great function of the leaf is to manufacture plant
foods. The leaf is so constructed that air can enter it
and come in contact with its living cells, as does the water
coming up from its roots. The circulation of water in
the leaf was seen in Experiment 119. There is in the living
cell of the leaf a green substance called chlorophyll. This
has the power to utilize the energy of sunlight and to com-
bine the carbon and the oxygen of carbon dioxide taken
from the air with the hydrogen and the oxygen of water
taken from the soil, thus forming a substance which prob-
ably at first is grape sugar, but which in many leaves is
changed at once into starch.
Experiment 120. — Boil a few fresh bean or geranium leaves for a
few minutes in a beaker of water. Pour off the water and pour on
enough alcohol to cover the leaves. Warm the alcohol by putting
the beaker in a dish of hot water. When the leaves have become
colorless, remove from the alcohol and wash. Place the leaves
in another beaker and pour on a solution of iodine. (This solution
can be made by dissolving in 500 cc. of water 2 grams of potassium
iodide and | gram of iodine. The solution should be bottled and
kept.) If the leaves turn dark blue or blackish, starch is present.
Experiment 121. — Place a thrifty geranium or other green plant
in darkness for two or three days and then treat the leaves as was
done in Experiment 120. Do they show the presence of starch?
The direct presence of the sun's energy in the form of light is neces-
sary for the formation of starch in the leaves.
It was found in Experiment 120 that leaves exposed to
the sun contained starch, and in Experiment 121 that
leaves which had been deprived of sunlight did not have
starch. The starch disappeared while the plant was in
darkness. Not all of the oxygen from the carbon dioxide
and the water is used in the manufacture of starch by the
chlorophyll, and so some of the oxygen becomes a waste
LEAVES 383
product which the leaves throw off. This will be seen in
Experiment 122.
Experiment 122. — Under an inverted funnel in a battery jar,
place some pond scum or horn wort. Fill the jar with fresh water
and over the neck of the funnel place an inverted test tube filled
with water. (Figure 122.) When placed in the sunlight, bubbles
of oxygen will rise into the test tube and collect. The
oxygen can be tested by turning the test tube right
side up and quickly inserting a glowing splinter. If
the splinter bursts into a flame, oxygen is present. (A
freshly picked leaf covered with water and put in the
sunlight will be seen to give off these bubbles.) After
a small amount of gas has been collected in the test
tube, mark the height of the water column and place
the battery jar in the dark, allowing it to remain there
for ten or twelve hours. No oxygen is given off in the dark.
Place the jar in the light again. Oxygen is given off. Is the sun's
energy needed to enable the plant to give off oxygen ?
The starch manufactured is insoluble in water and is
stored in the leaf during the day. But at night, when
the leaf is not manufacturing starch, it is able to digest
the starch by means of a special substance, leaf diastase,
which it forms. This changes the starch into sugar, which
is soluble and which is carried in solution to other parts of
the plant. Compounds such as starch and sugar, in which
there are only carbon, hydrogen, and oxygen, are called
carbohydrates.
The cells in the leaf and in other parts of the plant have
the power to change the sugar and combine it with- other
substances contained in the sap, thus forming more complex
chemical compounds. These contain nitrogen and sulphur,
besides the elements of the sugar. Such compounds are
called proteins. They are essential to the formation of
plant protoplasm and are very important as animal foods.
384
LIFE ON THE EARTH
The digested and soluble substances which are prepared
by the leaves are transported to other parts of the plant,
where they are combined by the protoplasm of the living
cell with other substances contained in the cell sap. Thus
the protoplasm itself is able to increase and form new cells
as well as other substances, such as woody tissue and oils
and resins. In forming these substances the plant requires
A PINE FOREST
From the pitch in these trees turpentine and tar are made.
oxygen just as animals do. If air is kept from the roots
of certain plants, as was seen in Experiment 114, the plants
cannot live.
These food substances which plants make by using the
energy supplied by the sun are the bases of all plant and
animal life. The sun's energy stored up in the green leaf
is the source of all plant and animal energy. If it were
LEAVES
385
not for the leaf manufactory run by the sun's power, life,
as we know it, would cease. Even plants that lack chloro-
phyll, like the mushroom, must live on the food manu-
factured by the chlorophyll of the green plants.
Experiment 123. — Procure a small, thrifty plant growing in a
flower-pot. Take two straight-edged pieces of cardboard sufficiently
large to cover the top of the flowerpot and notch the centers of
the edges so that they can be slipped over the stem of the plant
and thus entirely cover the top of the flowerpot. Fasten the edges
of the cardboard together by pasting on a strip of paper. The
top of the pot will now be entirely covered by the cardboard but
the stem of the plant will extend up
through the notches of the edges.
Cover the plant with a bell jar.
(Figure 123.) No moisture can get
into the bell jar from the soil in the
pot, as it is entirely covered. Set the
plant thus arranged in a warm, sunny
place. Moisture will collect on the
inside of the bell jar. This must
have been given out by the plant
leaves.
Since all the processes of form-
ing new material by the plant
require large amounts of water,
it can readily be seen why water is so essential to plant
development. The water from which the food materials
have been taken is thrown off by the leaves, as seen in
Experiment 123. The amount of water thus thrown off by
plants is very great. A single sunflower plant about six
feet tall gives from its leaves about a quart of water in a
day, and an acre of lawn in dry, hot weather gives off prob-
ably six tons of water every twenty-four hours.
If the water passes out of a plant too rapidly so that
FIGURE 123
386
LIFE ON THE EARTH
there is not enough left to provide for the making and
transporting of the food, the work of the plant cannot be
carried on, and the plant dies. It is on account of this
that many plants are especially prepared to retain their
water supply. In almost all plants the stomata, or little
pores in the leaf through which the water passes out, close
up when too much water is being lost.
In some plants, like the corn, when the root cannot
supply sufficient moisture, the leaves curl up and thus
present less surface for
evaporation. In trees
like the eucalyptus the
leaves hang vertically
when the sun gets too
bright and present their
edges to the sun's rays.
Some leaves, like the
sage, are especially pre-
pared to conserve their
moisture by having their
surfaces covered with
hairs. Others have a
waxy covering, as the
cabbage and the rubber
tree. In some plants the leaves are very small and have
few pores, as the greasewood of the desert, and some have
done away with leaves altogether, as the cactus. It is
because the roots cannot supply sufficient moisture where
the ground freezes in the winter that trees having large
leaves shed them. Only trees like the pine, whose needle-
like, waxy leaves give off almost no moisture, can retain
their leaves.
A SUNFLOWER PLANT
FLOWERS
387
Flowers. — The stem not only bears leaves but, in the
higher kinds of plants, it bears flowers. The function
of the flower is to
produce seeds and
provide for the con-
tinued existence of its
kind. If the flower
of a buttercup, quince,
cassia, or geranium is
examined, it will be
found to be made up
of four distinct kinds
of structures.
Around the outside
is a cluster of greenish
leaves. This is called
the calyx. Within the
calyx is the corolla,
a cluster of leaves
which in many plants are colored. Within the corolla are
a number of parts consisting of a rather slender stalk with
an enlarged tip. This tip is called the
anther, and the stalk and anther together,
the stamen.
In the center of the flower are the pistils.
At the top of a pistil is generally a some-
what enlarged portion, the stigma, which is
sticky or rough; and at the bottom there
is an enlarged hollow portion, the seed-
bearing part, called the ovary. These two
parts are connected by the stalklike style. The stamens
and pistils are the essential parts of the flower, the calyx
EUCALYPTUS LEAVES
FLOWER SHOW-
ING DIFFERENT
PARTS
388
LIFE ON THE EARTH
PINK GENTIAN
Showing the anthers, which are covered with
pollen.
and corolla being simply for protection or assistance. All
flowers do not have these four parts, but every flower has
either stamen or pis-
tils or both.
The anther pro-
duces a large num-
ber of little granular
bodies, called pollen
grains, each of which
consists of a free
cell containing proto-
plasm. When the
pollen grains are ripe,
the anther opens and
exposes them. If a
pollen grain of the right kind falls upon a stigma it grows and
sends down a tiny tube through the style into the ovary,
where a little proto-
plasmic cell, called the
egg cell, has been pro-
duced. The essential
parts of these two differ-
ent kinds of protoplasms
unite and a new cell is
formed.
This new cell grows
and divides into more
cells, thus forming the
young embryo of a new
plant. This embryo is
the living part of the
seed and around it usu- MINT
FLOWERS
389
all\ a great deal of plant food is stored, so that when it
begins to grow it will have plenty of nourishment until it is
able to develop the roots
and leaves necessary to
prepare its own food.
Embryos cann(3t be
produced unless pollen
grains and egg cells unite,
so it is absolutely essen-
tial that the right kind of
pollen grains be brought
to the stigma. Some
stigmas are able to use
the pollen grains pro-
duced by the anthers of
their own flowers, but
others can only use pollen
from other flowers and
other plants. It is there-
fore necessary that these
pollen grains be carried
about from flower to
flower if fertile seeds are
to be produced.
In some cases the pol-
len is borne about by the
wind, as in the case of
EAR OF CORN
Each kernel is the result of a wind-blown
pollen grain falling upon a corn-silk.
corn. In this way an exceedingly large number of pollen
grains are wasted, as can be seen by the great amount of
yellow pollen scattered over the ground of a cornfield when
the corn is in bloom. In the corn each one of the corn
silks is a pistil and a seed is produced at its base if a pollen
390 LIFE ON THE EARTH
grain lights upon the stigma at its upper extremity. The
flowers of walnut and apple trees are fertilized by wind-
blown pollen.
The pollen of very many plants, however, is carried
about by humming birds, bees, and other insects. As
the bee crawls into the flower to get the nectar at the
bottom, it brushes against the anther and
some of the pollen grains become at-
tached to it. These, later, are rubbed off
by the rough or sticky stigma of another
flower which the bee enters and thus the
flower is fertilized. The humming bird,
by reaching its long, slender beak down
into the long, narrow tube formed by the
corolla of the " wild honeysuckle " (Figure
124), brushes upon the stigma the pollen
grains it has obtained from another flower
and thus distributes pollen from flower to
flower. In no other way could these
FIGURE 124 J
plants be fertilized.
The beautiful colors of flowers and the sweet nectars
that many of them secrete are the adaptations of the plant
for enticing insects to enter them and bring to
their stigma the pollen from other flowers, or
take from their anthers pollen needed to
fertilize another similar plant.
FIGURE 125
Some flowers are so constructed that only
certain insects can fertilize them ; the wild honeysuckle
requires the humming bird, the red clover the bumblebee
(Figure 125), and other plants, other kinds of insects.
Flowers of some varieties of plants cannot be fertilized by
flowers of a like variety. Certain varieties of strawberries,
FLOWERS 391
for example, need to have other varieties planted near them,
if they are to prosper. Some plants need not only to have
other varieties planted near, but they also require the pres-
ence of special insects.
One of the most striking examples of this is the Smyrna
fig. For many years attempts were made to introduce
this fig into California. The trees grew but the fruit did
not mature. It was then observed that in the regions where
this fig was successfully grown a species of wild fig was
abundant and that the natives were accustomed to hang
branches of the wild fig in the Smyrna fig trees at the time
they were in flower. These wild fig trees were brought to
California and grown near the Smyrna fig trees, but still
figs did not mature. Upon further examination it was
observed that at the time of flowering a small insect issued
from the wild figs and visited the flowers of the Smyrna figs.
This insect was brought to California and now it is possible
to grow figs. The flower of the Smyrna fig has no stamen and
it is necessary for the wild fig to furnish the pollen which
is only successfully carried to the stigmas of the edible fig
by the small fig-fertilizing insect.
A somewhat similar case is that of the yucca found in
the dry region of southwestern United States. This flower
can be fertilized only by the aid of a small moth which flies
about at night from flower to flower. It enters the flower,
descends to the bottom, stings one of the ovaries, deposits
an egg, then ascends and crowds some pollen on the stigma.
The grub, when it hatches from the egg, feeds on the seeds
in the ovary, but as there are many seeds in the flower
which have been fertilized and the grub eats only a few of
these, the moth has made it possible for the yucca to pro-
duce seeds sufficient for its continued propagation, which
392
LIFE ON THE EARTH
would be impossible if it
were not for the moth.
These are only a few of
the vast number of cases
which show the close re-
lationship existing between
plants and animals and
the dependence of the one
upon the other.
Seed Dispersal. — Not
only must flowers produce
fertile seeds, if the plants
are to continue to exist,
but these seeds must be
scattered. To do this the
seed pods of some plants
suddenly snap open and
spread their seeds. The
touch-me-not and pea are
examples of this. In some
plants, like the maple, the seeds are winged (Figure 126) and
float for some distance in the air. Others, like the thistle
and the dandelion, have light, hairlike
appendages which enable them to float
away. In the case of the tumbleweed
(Figure 127) the plant itself is blown
about, scattering the seeds over the fields
as it bumps along from place to place.
Some seeds are provided with hooks or barbs, like the
beggar 's-ticks (Figure 126), which attach the seeds to animals
so that they are carried to a distance. Seeds having an
YUCCA OK SPANISH BAYONET
FIGURE 126
SEEDS AND THEIR GERMINATION
393
FIGURE 127
edible fruit cover, such as the cherry, blackberry, and plum,
are eaten by birds and animals and the undigested seed
deposited far away from the place
where the seed grew. Seeds like
the acorn are carried about by
squirrels and other animals. Many
seeds are able to float in water for
a considerable time without being
injured and are borne about by
currents. Shores of streams and islands receive many of
their plant seeds in this way. The cocoanut palm is a no-
table seed of this kind and is found widely scattered over
tropical islands.
Seeds and Their Germination. — Experiment 124. — Take
two common dinner plates and place in the bottom of one of them two
or three layers of blotting paper and thoroughly wet it. Place some
wheat or other kinds of
seeds upon this. Now in-
vert the other plate over the
^HK Jj t first, being careful to have
the edges touch evenly.
This makes a moist chamber
and gives the most favor-
able conditions for ger-
mination. Do all the seeds
germinate at the same time ?
Does the position of the
seed make any difference?
What takes place first in
the process of germination?
What appears first, the leaf
or the root ? Why does the
seed shrivel up?
SCRUB OAK BRANCH Experiment 125. — Cut
Showing the acorns. open several seeds, such as
394 LIFE ON THE EARTH
pumpkin, squash, bean, corn, and drop on to the inside of each a few
drops of the iodine solution made in Experiment 120. Do the
seeds show the presence of starch ?
Experiment 126. — Soak some beans for about twenty-four hours.
Rub off the skin from two or three and examine their different parts
carefully. Plant the beans in a box of damp sawdust. Put the
box in a warm place. Plant some corn that has been soaked for
two or three days in the same box. After the seeds have been
planted several days, carefully remove a bean and a grain of corn
and examine. Make a sketch of each of the seeds.
After a few days more remove another seed of each and examine
and sketch. Continue to do this until the little plants have be-
come quite well grown. Do the two seeds
develop alike? Which of the seeds has two
similar parts? These two parts are called
cotyledons. What appears to be the use of these
parts to the sprout? Consult the results of
Experiment 124. Note the root development
in each seed and the stem development. The
sprouts get their food from the seed.
When we examined the different seeds
in Experiment 125, we found that they
each contained starch. When the seeds
were soaked and planted, we found that
a part of the seeds began to grow, form-
FlGURE 128
ing a sprout. Inis part is the embryo
already described. We also saw that the bean seed divided
into two like parts which gradually withered and shrank,
as the sprout grew, while the corn had only one such part.
These parts are called cotyledons, or seed leaves. The
bean seed (Figure 128) is a dicotyledon (two seed leaves)
and the corn a monocotyledon (one seed leaf). These coty-
ledons are the food storehouses for the germinating seed.
As the sprout grew, the root, with its root hairs, developed,
SEEDS AND THEIR GERMINATION 395
and the stem with its leaves. When these had grown strong
enough, the cotyledons, having performed their part, dropped
off. The plant was now ready to prepare its own food by
the aid of the sunlight.
Experiment 127. — Place several beans in a tumbler of damp saw-
dust and put it in a warm, light place. Keep the sawdust moistened.
After the beans are well sprouted, with a sharp knife cut one of the
half beans or cotyledons off from a sprout. Cut both cotyledons
off another sprout. Put the sprouts back on the sawdust. Do
the sprouts grow as well as those of the other beans ?
Experiment 128. — Fill a 16-ounce, wide-mouth bottle about one
third full of peas or beans. Pour in more than enough water to
cover them. Tightly cork the bottle and put in a warm, sunny
place. Put another similar corked empty bottle beside it. Allow
the bottles to stand for several days until the peas have sprouted.
Remove the cork from the bottle containing the peas and insert
a burning splinter. Do the same to the empty bottle. Why does
not the splinter burn as well in each ? If on being placed in either
bottle the splinter is smothered out, it shows the presence of carbon
dioxide.
Experiment 129. — Fill two 8-ounce, wide-mouth bottles each
about one third full of coarse sawdust and fill the remaining part
with peas which have been soaked for a day. Pour in sufficient
water to cover the sawdust. Cork one of the bottles tightly, leaving
the other open. Put the two bottles in a warm, sunny place.
Whenever necessary, pour on sufficient water to keep the sawdust
in the open bottle wet. In which bottle do the seeds sprout the
better? Does air appear to be necessary for the growth of seeds?
As determined by the previous experiment, what part of the air
is used?
We found in Experiment 127 that if the cotyledons
were cut off before the sprout had become sufficiently
mature, it could not continue its growth. In Experiment
128 we found that the sprouting seeds took up oxygen
from the air and gave out carbon dioxide just as animals
396 LIFE ON THE EARTH
do. Energy was needed and this energy was obtained by
combining the carbon in the seed with the oxygen in the
air, as it is when wood is burned. We found in Experi-
ment 129 that the seeds could not sprout well unless suffi-
cient air was supplied. That was because there was not
enough oxygen supplied to furnish the necessary energy.
Experiment 130. — Place several sprouted seeds in each of two
tumblers nearly filled with damp sawdust. Put these tumblers
side by side in a warm, light place. Cover one of the tumblers
with a box painted black so as to exclude the light. In which do
the seeds grow the better?
After the seeds were sprouted and had begun to pre-
pare their own food, it was found in Experiment 130 that
they were not able to do this unless exposed to the light
of the sun. The parent plant had stored, in a latent form
in the seed, energy which it had received from the sun.
This potential energy the sprout was able to change into
the kinetic form by the aid of oxygen, and to use in the
work of growing. After this latent energy had been ex-
pended, it had to fall back upon the direct energy of the
sun which came to it in the form of sunlight.
Dependent Plants. — Experiment 131. — Expose a piece of
moist bread to the air for a short time and then put it into a covered
dish so as to retain the moisture. Does any change take place in
the bread ? Examine with a magnifying glass the mold which ap-
pears.
Experiment 132. — (1) Bruise a sound apple and place the bruised
part in contact with a thoroughly rotten apple. Wrap the two up
together in a wet cloth and put in a fruit jar. Seal the jar to prevent
the water from evaporating. (2) Plunge a pin repeatedly first
into a rotten apple and then into a sound one. Wrap the sound
apple in a wet cloth and seal in a fruit jar. (3) Place a lemon
which has developed a green, spongy, rotten place in it in contact
DEPENDENT PLANTS
397
with a perfect lemon and keep them where they will be moist.
What happens to the sound fruits?
The plants that we have so far studied are green plants
and contain chlorophyll. They are able to prepare their
food from the air and soil by the aid of the sun's energy.
There is, however, another great group of plants which
may be called dependent plants. They have no chlorophyll
MISTLETOE GROWING ON AN OAK
An interesting parasitic plant.
and are obliged to live upon the food that green plants have
prepared. They find this food either in the living or in the
dead parts of plants or animals, the animals having digested
it from plants or other animals, who originally obtained it
from plants. If plants live upon living plants or animals,
they are called parasites, if upon dead ones, saprophytes.
We are most of us familiar with some of the larger de-
398
LIFE ON THE EARTH
FIGURE 129
pendent plants, or fungi, such as the mushrooms (Figure
129) and toadstools. Mushrooms are widely used as a deli-
cacy and their growth is an important industry in some
sections. They are grown in soils very rich in humus and
generally in dark, cellarlike places. The
mushrooms that grow wild in the woods
are abundant in some localities but
should not be used for food unless most
carefully examined by some one who
is expert in determining the different
species. There are several species of
mushrooms which are exceedingly poison-
ous. For one of these there is no known antidote. The
general structure of these larger fungi can be seen by
examining a mushroom obtained from the market.
The bacterium is a single-celled de-
pendent plant, probably the simplest
of all plants ; it can be seen only with
a high-power microscope. Bacteria
are rod-shaped, thread-shaped, screw-
shaped, or have various other forms
(Figure 130). The protoplasm in the
cell of bacteria has the power to as-
similate food and build more proto-
plasm. When the cell has grown
sufficiently, it divides into two cells.
A healthy bacterium grows fast
enough to be ready to divide about
once an hour. If it divided once an hour and each division
continued to divide once an hour, in the course of twenty-
four hours there would be nearly seventeen million bacteria
produced. If this were kept up for some weeks, the mass
'
> ~"
A^
FIGURE 130
ANIMALS 399
of bacteria would be as large as the earth. Of course, this
would mean that each bacterium had plenty of room to
live in and plenty of food to live on and nothing to injure
it. These conditions are not found, and each bacterium has
to struggle for existence just as every other plant does.
As it is, however, bacteria are numberless.
Some of the activities of soil bacteria we have already
studied. There are many other kinds of bacteria, and the
relations of many of them to man are of such importance
that they will be given further attention in another chapter.
Molds are made up of many cells, and reproduce them-
selves by producing spores. If the mold on bread is allowed
to grow for a long enough time under favorable circumstances,
you will note a fine black powder that forms. The par-
ticles of this powder are spores (seedlike bodies) which will
themselves grow into molds if favorable conditions are
offered. Mushrooms reproduce by means of spores.
Yeasts are single-celled plants, as are bacteria, but they
do not increase as bacteria do. A little bud forms on the
side of the yeast cell, which grows until it finally separates
from the parent cell. In this way a single yeast cell
may produce several other yeast cells, whereas a single
bacterium may only divide into two.
Animals. — Animals do not take -their energy directly
from .the sunlight, but indirectly from the latent energy
stored up in the foods prepared by green plants. These
foods may be eaten as stored by the plants, or they may
have passed through the medium of other plants and an-
imals. The energy thus stored up is liberated by com-
bining the carbon with oxygen. Carbon dioxide is freed.
The green plants use this carbon dioxide again and, by
400
LIFE ON THE EARTH
the aid of the sun's energy, free the oxygen and store up
the carbon. Thus the cycle goes on, over and over, the
plants freeing oxygen and taking up carbon dioxide, and
the animals freeing carbon dioxide and taking up oxygen.
The cells of plants which feed upon the food prepared by
the chlorophyll of the leaves use oxygen and give out carbon
dioxide just as the animal cells do ; so also do other plants
to some extent.
Classification of Animals. — For convenience of study
the animal kingdom has been divided into two great classes
— the invertebrates (without backbone) and the vertebrates
(with backbone). The invertebrate is the much more
numerous class as it contains the worms, shellfish, insects,
and those almost countless
forms of animal life which
have no internal bony skele-
ton and backbone. The
higher animals, like fishes,
amphibia, reptiles, birds, and
mammals, belong to the
class of vertebrates. Man
himself is the highest of the
vertebrates, and his struc-
ture will be studied later.
GLOBIGERINA (Greatly magnified)
Invertebrates : Protozoa.
The shells of these minute animals _ The very lowest f orms of
cover much of the ocean floor.
animal life, the protozoa,
are single-celled animals. In some species they are very
difficult to distinguish from plants of the lowest orders.
They are microscopic in size and most of them live in water.
Some of these tiny protozoa living in the sea are covered
WORMS 401
by an extremely thin shell of lime. When they die, their
shells sink to the bottom of the sea. So rapidly do these
animals multiply that their minute shells have made thick
layers of chalk like the famous chalk cliffs of the south
of England.
Our chief interest in protozoa in the present study is that
certain of them are the cause of several kinds of disease which
can readily be prevented with proper care. Malaria and
the terrible African disease called sleeping sickness, and
probably yellow fever, are caused by these little animals.
We shall study them more fully later in connection with
harmful bacteria.
Worms. — Another class of invertebrates is the worms.
One of these, the earthworm, was found in the study of
soil making to be very important and should be considered
EARTHWORM
A great helper to the farmer.
in this place. If an earthworm is examined, it will be
seen that the body is made up of segments or rings, and
that it moves by successively shortening and elongating
its body. Extending through the middle of the body is
402
LIFE ON THE EARTH
an alimentary canal consisting of a mouth, gizzard for
grinding food, stomach, and intestines.
Near the head is a little nerve center. The whole an-
imal may be regarded as built up by the joining of a number
of essentially similar segments. A more minute examina-
tion will show that
these segments have
been materially
modified in some
portions of the ani-
mal, but they have
not been in any re-
spect organized, as
have the different
parts of higher ani-
mals. This simple
animal, as has al-
ready been seen, is
an untiring worker in
preparing and ferti-
lizing soil for plants,
and thus is a most
efficient helper to
man.
Insects. — Experi-
ment 133. — Procure a
grasshopper or honey-bee, as a type insect, and inclose it in a small,
glass-covered box. Into how many parts is the body divided?
Describe these parts. To which part are the legs attached? The
wings? How many legs are there? How many wings? Notice
the largest part into which the body is divided. Notice the eyes
and the feelers, or antennae, on the head. Write a short descrip-
tion of the general characteristics of the bee's body.
BUTTERFLY ON ALFALFA
INSECTS
403
The insects are among the most important of animals.
This class contains more than half the known animal species.
They are spread widely over all parts of the earth.
Both good and bad insects abound. Economically, they
furnish millions upon millions of dollars' worth of produce
every year and on the other hand destroy hundreds of
millions of dollars' worth of crops and trees. It has been
estimated that in the United States insects destroy every
year crops and trees which have a
value of $50,000,000, to say nothing
of the countless losses due to dis-
eases spread by flies and mosquitoes.
(Page 452.) Not many years ago
grasshoppers nearly devastated sev-
eral of the middle western states.
The most productive insects are
the silkworms and the bees. With-
out the silkworm (Figure 131) there
would be no silk produced, and with-
out the bee, no honey. These two
products each year run into hundreds
of millions of dollars. We have already seen that bees and
other insects are needed also for the fertilization of flowers.
Among the most interesting of the insects and perhaps,
everything considered, the most valuable, is the honey-bee.
This is the great flower fertilizer ; it would fertilize about all
the plants man really needs except the red clover. In the
United States alone there is produced by it about twenty-
five million dollars' worth of honey and wax each year.
In Experiment 133, it was found that the body of the
bee, like other insects, is divided into three parts. These
parts are called head, thorax, and abdomen. The eyes
FIGURE 131
404
LIFE ON THE EARTH
and the feelers, or antennae, are on the head. The mouth
is a very complex organ, fitted both for biting and for suck-
ing. The six legs and four wings are on the thorax. The
hind leg of each working bee is so shaped and fringed with
hairs that it forms a pollen basket.
Honey-bees live in large colonies and in the colony there
are three kinds of bees, the male bees, or drones, the workers,
BEEHIVES
Hundreds of dollars' worth of honey are produced here each year.
and the queen or female bee. The workers are the ones
that make all of the honey and wax, do all the work of the
hive and feed the grubs on rich food formed in their own
stomachs, as well as on pollen mixed with honey. The
grubs are the first stage in the development of the bee
from the egg. The queen lays all the eggs, sometimes as
many as a million. There is but one queen in each swarm.
Whenever another queen is ready to be hatched, the old
VERTEBRATES
405
queen takes about half the colony and goes off to form
another swarm.
The wax is secreted from glands in the abdomens of the
workers and with this the bees build the comb. Each cell
is hexagonal in cross section and
the comb is so constructed that
the least possible amount of wax
will inclose the greatest possible
amount of honey. The nectar
at the bases of flowers supplies
the bee with the material from
which it makes the honey. It is
in seeking for this that the bee
visits so many flowers and scrapes
the pollen on to the different
parts of its body, to be borne
away to fertilize other flowers
which it enters. Such an inter-
esting animal and so exceedingly
useful is the bee that hundreds
of books have been written about
it, more than about any other
domestic animal. Some of these
should be read for further in-
formation concerning this most
instructive animal.
Vertebrates. — Experiment 134.
— If possible, secure the skeleton of
some vertebrate animal; preferably A HuMAN SKELETON
man. Notice how the bones are
_ . . . . . Notice how the bones are ar-
fitted to each other and how the ranged to protect the delicate
joints are arranged to allow move- organs. ;
406
LIFE ON THE EARTH
ment. Observe how carefully the brain and the spinal cord are
protected, and also the thorax, which contains the heart and lungs.
If a human skeleton is
procured, notice the curv-
ing of the spine which en-
ables the body to stand
erect.
We have just studied
briefly some of the in-
vertebrates most closely
related to the welfare or
injury of man. Man
himself belongs to the
other great class, verte-
brates. The higher ani-
mals which furnish him
with the greater part of
his animal food also be-
long to this class. Al-
though there are great
variations in the struc-
ture of vertebrate ani-
mals, yet they are alike
in having a backbone
and an inner supporting
skeleton.
The bony skeleton in
the higher forms of ani-
mal life consists of a
vertebral column, skull,
ribs, and appendages.
The main skeleton pro-
THE NERVOUS SYSTEM or MAN
Notice how the nerves are distributed
to all parts of the body.
BREATHING 407
tects the most delicate organs and acts as a support for the
attachment of the muscles. The appendages, like the legs
and arms in man, are jointed to the central part of the
skeleton, and it is the action of the muscles in moving these
about the joints that makes movement from place to place
possible.
In the skull is situated the great nerve center of the
animal, the brain, and from this through the vertebral
column passes the great nerve distributor, the spinal cord.
From the brain, nerves are sent to all the muscles of the
body, to the skin and to those organs, like the eye and
the ear, which transmit to the brain impressions received
from without the body. These nerves give the stimuli
which cause the muscles to thicken, or contract. In fact,
all the voluntary movements of animals are controlled from
the brain, as the movements of trains on a railroad are con-
trolled from the dispatcher's office.
Breathing. — All animals must have a way to breathe,
or energy cannot be supplied to carry on the activities of
the body. Different animals breathe in different ways,
but in the higher vertebrates and in man it is the same.
Breathing in man will, therefore, be taken as the type.
Air enters the body through the nose or mouth, and
passes down through the windpipe into the lungs. In order
to keep out dust and germs, the opening of the nose is
supplied with a large number of hairs projecting from the
mucous membrane which lines the whole nasal chamber.
These hairs and the secretion from the membrane catch and
hold most of the harmful particles.
It is most important that air should be breathed through
the nose and not through the mouth. Air which enters
408 LIFE ON THE EARTH
the lungs through the mouth is not sifted as it is when it
passes through the nose; moreover it is not sufficiently
warmed because the mouth passage is much shorter than
the nasal passages. Thus the throat and lungs are irritated
by mouth-breathing and are more liable to disease.
Sometimes abnormal spongy growths called adenoids
partly fill the upper part of the throat. They not only
obstruct nose breathing but also furnish a breeding place
for disease germs. It is a simple matter for a surgeon to
remove them; and unless they are removed, they may
result in disordered stomach, quarrelsome disposition,
stunted growth, and even stupidity. Most of the cases
of adenoids are found in children. Children may or may
not outgrow adenoids, but some or all of the evil effects
remain if the trouble is long neglected. In the interest
of mental and physical vigor as well as of attractiveness
of countenance, the removal of adenoids ought never to
be unduly postponed.
At the back of the mouth the windpipe and the throat
come together.
When food is being swallowed, the passage into the wind-
pipe must be closed, and this is done by the little valvelike
epiglottis. If, in swallowing, the epiglottis is not able to
close quickly enough, something may pass into the wind-
pipe and cause choking. The windpipe, at the upper part
of the chest, branches into two parts, one branch going to
each of the lungs.
The lungs fill the upper part of the chest and infold
the heart. In them the air tubes divide again and again,
forming a vast network of tubes which grow smaller and
smaller until they end in little air sacks. Interlacing with
these air tubes are veins and arteries which carrv the blood.
BREATHING
409
The tiniest parts into which the blood vessels are divided,
the capillaries, form close networks within the linings of
the air sacks. The air and blood are thus separated by an
exceedingly thin animal tissue, which allows an exchange
of soluble materials. Thus the blood is able to take up the
oxygen needed and to rid itself of the carbon dioxide and
other waste products which it has accumulated.
The air-tight thoracic cavity in which the heart and
lungs are situated is inclosed and protected by the ribs
and at the lower part by
a dome-shaped muscle
called the diaphragm .
Air enters the lungs
because the muscles of
the chest pull the ribs
so that they move up-
ward and outward and
the muscles of the dome-
shaped diaphragm cause
it to move downward.
These two actions en-
large the thoracic cav-
ity. The air enters in
the same way that it enters a hollow rubber ball that has
been compressed and then set free. When the ribs move
downward and the diaphragm upward, the air is expelled as
in the rubber ball when compressed.
There are then two ways in which air can be made to
enter the lungs, the " raising of the chest " and. the move-
ment of the diaphragm. In the proper kind of breathing
these two movements go on together. The lungs are filled
throughout and not simply at either the top or bottom.
THE LUNGS
They are here pulled aside to show
the heart.
410 LIFE ON THE EARTH
If this is to be accomplished, the body must be free and
not restricted by tight clothing about the chest or the lower
part of the trunk of the body, the abdomen. Not only is
the right kind of breathing necessary for properly supplying
the blood with oxygen, but also that the lung tissues them-
selves may be properly nourished and cared for. We
should be particularly careful about this now that infec-
tious diseases of the lungs are so prevalent.
Circulation. — Experiment 135. — If a compound microscope
can be procured, tie a string tightly around the end of a clean finger,
and when it has become full of blood, prick it quickly with a steri-
lized needle. Rub the drop of blood that comes out on a glass
slide and quickly examine under the microscope. Notice the great
number of round, disklike bodies, red corpuscles. Try to find an
irregular-shaped body which, while the blood remains fresh, slowly
changes its shape, *a white corpuscle. These are rather difficult
to find, but can be seen if the drop of blood is thoroughly examined
quickly enough.
In order that all parts of the body may be provided
with the materials used in building their cells and in doing
oc the work necessary for continued
00<& OQ o$ existence there must be a dis-
o? o °£*>o00 o°°o o goQ tributory system. Thisisneces-
0°° 0°0^QP° oSoO & O T -o i
30 o o °8 sary wherever diversified work
is to be carried on. This neces-
sity'has brought into effect the
railway and canal systems of the
world. The body is a little world
FIGURE 132 , ., ,» -, ., ,
by itself, and it has a most com-
plete and wonderfully adapted system for supplying the
material needed and for removing the waste. The center
and motive power of this system is the heart. The medium
of circulation is the blood.
CIRCULATION 411
When the blood is examined, it is found to consist of a
watery liquid, called the plasma, a great number of little
disk-shaped bodies, the red corpuscles, and some irregular
whitish bodies, the white corpuscles (Figure 132).
The white corpuscles are protoplasmic cells possessing
the power of movement and even of working their way out
of the blood vessels. They are the soldiers of defense of
the human body. When a white corpuscle comes in contact
with a disease germ, the body of the corpuscle takes the
germ into it and tries to digest it. The germ in turn tries
to multiply inside the corpuscle and to feed on it. Unless
the germs increase in number too rapidly,
the white corpuscles come off victorious.
The blood also provides other substances
that are probably even more important than
white corpuscles in fighting disease. Some
of these substances kill disease germs and A WHITE CORPUS-
others counteract germ poisons. CLE DIGESTING A
_, . , / - GERM (Greatly
The mam function of the red corpuscles magnified.)
is to carry oxygen from the lungs to the
different living cells of the body. They contain a pigment,
hcemoglobin, which carries the oxygen and gives the blood
its color. The plasma, an exceedingly complex fluid, is
composed largely of water, but contains the nutrient and
waste materials supplied by the different organs of the body.
The blood passes through different kinds of vessels.
Those leading from the heart are called arteries, and those
returning to the heart are called wins. As the arteries
proceed from the heart they divide continually, becoming
smaller and smaller until they terminate in very small,
thin- walled vessels called capillaries. These capillaries
unite and form veins. Thus the blood is continually flow-
412
LIFE ON THE EARTH
ing from the heart -through the arteries and capillaries into
the veins and back to the heart.
As a rule the arteries are below the surface of the body,
where they are protected, but if the finger is placed on
the wrist or the side of
the face near the ear,
an artery can be felt
through which the blood
is pulsing. The veins
can be seen in the back
of the hand and a pin
piercing the body any-
where will break open
some of the capillaries
and cause blood to ooze
out. The capillaries
spread throughout the
entire tissue of the body
and supply with food
and oxygen the different
living cells of which the
body is composed.
The heart is a muscu-
lar force pump composed
of four chambers, two
auricles and two ven-
tricles. It is shaped
somewhat like a pear and is situated almost directly be-
hind the breastbone. The blood coming back from the
veins flows into the right auricle, a chamber with rather
flabby walls. From here, it passes through a valve into
the right ventricle, which is a chamber with verv thick
THE CIRCULATORY SYSTEM
Notice the veins (white) are nearer the
surface than the arteries (black) .
THE SENSES 413
muscular walls. From the right ventricle, the blood is
driven out through the arteries, capillaries, and veins of
the lungs, where carbon dioxide is given off and oxygen
absorbed by the red corpuscles.
Returning from the lungs, the blood enters the left auricle
and when this becomes full, passes through a valve into
the left ventricle. This has such powerfully muscular walls
that it is able to force the blood through-
out the body and back again to the
right auricle. As the blood leaves either
ventricle, there are valves that close and
prevent its return. If the hand is placed
a little to the left of the breastbone, the
strong contraction of the ventricle can
be felt.
CROSS SECTION OF
THE HUMAN HEART
The Senses. — In order that the brain Showing aliricle ven.
may communicate with the outside world tricle, and ventricle
and so be able to protect the animal
from destruction and to provide for its well-being, animals
are provided with a number of sense organs which com-
municate with the brain by the nerves. The most con-
spicuous sensations of the human body are taste, smell,
touch, sight, and hearing.
On the tongue and in the nose are cells which transmit to
the brain the impressions produced upon them by different
qualities, the one of solutions and the other of gases. The
sensations thus produced are called taste and smell.
The sensation of touch originates in the skin and is much
more acute in some portions than in others. The tips of
the fingers in the blind are often trained to such delicate
perception that they, in a great degree, take the place of
414 LIFE ON THE EARTH
the lacking sense organ. These sensations, like all others,
are carried to the brain by the nerves and there interpreted
into the sensation of touch.
Sight. — The organ of sight, the eye, is an exceedingly
sensitive, automatically adjustable camera that records
through the nerves. The camera box is the hard, bony
socket in which the eye is placed, the eyelid is the shutter,
and the iris, the diaphragm. The iris is the membrane in
the front of the eye which
opens or contracts to let
in more or less light. In
the center of it is a hole,
the pupil.
Back of the diaphragm,
or iris, is a small adjust-
able lens and beyond this
the sensitive plate, the
CROSS SECTION OF THE HUMAN EYE retina. Between the iris
The pupil is the opening surrounded and the front of the eye
by the iris. . 1M . -t
is a wateryhke material,
the aqueous humor, which keeps the front of the eye ex-
tended into its rounded form. Back of the lens is a thick,
transparent, jellylike material, the vitreous humor, which
holds the retina extended and keeps the eye from collapsing.
Instead of moving the retina back and forth to focus a
picture, as is done with the ground-glass plate in a camera,
the eye lens is capable of adjusting itself so as to focus objects
which are at different distances. Leading back to the brain
from the retina is the optic nerve, which carries the impres-
sions made on the retina to the brain, where they are inter-
preted into the sensation of sight.
OPTlfc
NERVE
SIGHT
415
MOVING PICTURE OF A HIGH JUMP
416 LIFE ON THE EARTH
This rough comparison is by no means a description of
the eye, for it is a most complex and wonderful organ, vastly
superior in construction to a camera. A technical descrip-
tion would, however, be out of place here. The impres-
sion made on the retina remains for an instant; and so if
successive pictures (about twelve a second) are taken of a
moving object and projected on a screen at the same rate
the eye will not distinguish the intervals between the pic-
tures and the object will appear to be in motion. This is
the way in which moving pictures are produced.
Sometimes the lens is not able to focus a picture distinctly
on the retina, and then it is necessary to aid the lens of the
eye with artificial lenses, or glasses. Silly notions about
one's personal appearance in glasses should never stand in
the way of wearing glasses when they are necessary. If
there is a strained feeling when the eyes are used, or if
headaches result from continued use of the eyes, reliable
advice should be sought.
The eye is so important for our usefulness and happiness
that the greatest care should be taken of it. One should
not read when he is lying on his back, when the light is
either poor or glaring, or when the book cannot
be held steadily. The eye may be infected from
public washbowls, public towels, or even by
rubbing with one's own fingers. Any infection
of the eye demands skillful treatment and should
not be trifled with.
FIGURE 133 Sound and Hearing. — Experiment 136. — Arrange
a large, wide-mouthed bottle with a small bell sus-
pended in it from the stopper and a delivery tube extending through
the stopper. (Figure 133.) Attach the delivery tube by a thick-
walled rubber tube to an air pump and exhaust the air from the
SOUND AND HEARING 417
bottle. Shake the bottle so that the bell can be seen to ring but,
does not strike the sides of the bottle. Can the sound be heard
distinctly ?
Experiment 137. — Suspend a pith ball by a light thread so that
it may swing freely. Strike a tuning fork and quickly place it in
very light contact with the pith ball. The ball will be set in mo-
tion by the vibrations of the tuning fork.
In Experiment 136 it was found that if the air was ex-
hausted and the bell did not touch the sides of the bottle,
almost no sound was heard when the clapper of the bell
showed that the bell was ringing. This shows that the sounds
we usually hear are transmitted in some way by the aid of
the air. In Experiment 137 the sounding
body was seen to be vibrating. Since
these vibrations set the pith ball moving,
we may understand that the air surround-
ing the tuning fork must also have been
set in motion.
Sound has been found to be a wave
motion in a material medium. If a
scratch is made on the end of a long log,
it can be heard if the ear is placed at the other end of the
log, when it cannot be heard if the ear is away from the log.
In this case the medium is the wood.
If a stone is dropped into a quiet pond, the rippling waves
developed will extend often to the farthest shore of the pond,
but a chip floating near where the stone fell will not be moved
from its position except up and down. Thus the waves
traveled outward from the point of origin, but there was no
outward movement of the water. If a long rope, attached
at one end and held in a horizontal position, is suddenly
struck with a stick, a wave motion will travel along the
418
LIFE ON THE EARTH
rope from end to end, but the particles of the rope will
simply move up and down. It is in a similar way to this
that the sound waves travel, but the particles which trans-
mit the sound only move back and forth through small
distances. (Figure 134.) An echo is simply a reflection of
sound waves from some obstruction they meet.
The ear, which is the sound transmitter of the body, con-
sists of the outer ear, which is so arranged as to catch the
sound waves and converge
them upon the ear drum.
The ear drum is a thin
membrane stretched tightly
across a bony opening and
vibrates when the air waves,
strike it, as a drum does
when struck by the drum-
stick. On its inner side
the drum is attached to the
inner ear by a chain of
three bones. The sensitive
cells of the inner ear trans-
mit the impressions made by the sound vibrations through
the auditory nerve to the brain, where they are interpreted
into the sensation of sound.
The drum head of the ear is easily broken, and therefore
no hard instrument should ever be thrust into the ear.
There is an old saying that one should never pick his ear
with any kind of hard instrument having a smaller point
than one's elbow. Immediate and skillful attention should
be given to any inflammation of the ear. If neglected it
may lead to deafness or even to an exceedingly dangerous
abscess in the bone back of the ear.
CROSS SECTION OF THE HUMAN EAR
FOOD 419
Food. — Experiment 138. — Chop a piece of the white of a hard-
boiled egg into pieces about as large as the head of a pin and place
in a test tube. Chop up another piece much finer than this and
place it in a second test tube. Make a mixture of 100 cc. of water,
5 cc. of essence of pepsin, and 2 cc. of hydrochloric acid. Pour into
each test tube enough of this mixture to cover the white of egg to
a considerable depth. Shake thoroughly and put in a place where
the temperature can be maintained at 37° C. or 98° F. A fireless
cooker or a bucket of warm water is good for this. Allow to stand
for several hours, keeping the temperature constant. The white
of egg is dissolved, the action being more rapid in the second tube.
Try the same experiment using water; using dilute hydrochloric
acid. Do these have the same effect as when used with the pepsin?
The pepsin solution is an artificial gastric juice.
In order that the work of the body may be carried on,
food is required. This food may be supplied by either
animals or plants. The original source of all animal and
plant food, as has been seen, is in the chlorophyll manu-
factory of the leaf and green stem. After this leaf food
has been manufactured, it is simply modified by the plants
and animals through which it passes. The food is used
(1) in growing new cells, (2) in repairing cells that have
been used up or destroyed, (3) in providing energy to carry
on the activities of the body and maintain its heat, or (4) in
doing external work, such as moving the body itself from
place to place or moving other bodies.
To furnish any of this energy, the cells must be able to
combine food with oxygen. To do this the food must be
digested or prepared so that it can pass through animal
tissue. In the higher animals, a complicated apparatus is
provided to accomplish this. In man it is briefly as follows :
a long, continuous tube, the food-tract or the alimentary
canal (Figure 135) extends through the body. Different
420
LIFE ON THE EARTH
Salivary
Gl&nds X
portions of this tube are adapted to different processes. In
the mouth, the teeth grind the food into small bits and mix
it with the saliva. This is an exceedingly important part
of the process, because if the food is not ground fine, the
digestive juices cannot readily get at it, and the whole process
of digestion is greatly retarded. Thus much more energy is
expended than otherwise
would be. The saliva is
necessary to digest some of
the starch and to aid in the
further digestion.
The food passes from
the mouth down the throat
and through an orifice to
the stomach. This is a
large pouch which will hold
usually from three to four
pints. It has muscular
walls which enable it to
contract and expand, thus
keeping the food mov-
ing about so that it is
thoroughly mixed with the
gastric juice. The gastric
juice is secreted by little
glands thickly embedded
in the lining of the stomach. Artificial gastric juice was
made in Experiment 138. Some of the proteins (foods con-
taining nitrogen) are digested in the stomach, although the
larger part of digestion takes place in the small intestine.
From the stomach the food passes through a valve into
the small intestine. This is a complexly coiled tube which
FIGURE 135
SUMMARY 421
fills the larger part of the abdomen. The inner wall of
the tube is lined with glands which secrete digestive juices,
and into the intestine are poured the secretions from two
large glands, the pancreas and the liver. The small intes-
tine is the great digestive organ of the body. Here the fats
and oils are digested, and the digestion of the starches and
proteins is completed. The small intestine opens through a
valve into the large intestine, a tube five or six feet long
decreasing in size toward the exit from the body. There
is little digestion in the large intestine.
The changes that take place in the food as it passes
through the alimentary canal are very complex, but dur-
ing its progress the valuable part of the food is so changed
and prepared that it can be absorbed by the blood and
transported by it to the different parts of the body where
its energy is needed. Absorption takes place all along
the alimentary canal wherever the food has been suffi-
ciently prepared.
In the entire process of digestion of food the only part
that can be controlled by the individual is the chewing of
the food. It is necessary that the food be ground fine in
order that the digestive juices may readily act upon it and
not leave any undigested fragments as abiding places for
germs. Decayed and unbrushed teeth furnish unlimited
breeding places for germs. Careful experiments have shown
that the health of the body and the mental vigor are greatly
increased by properly caring for the teeth. The teeth must
be kept clean and all cavities must be properly filled if health
is to be maintained.
SUMMARY
Plants and animals make up the live part of the earth.
Most green plants consist of root, stem, and leaves. The root
422 LIFE ON THE EARTH
anchors the plant to the ground and takes in from the soil
all the plant's food except carbon. This is supplied from
the, carbon dioxide of the air, which enters the plant through
the leaves. Leaves are the original food manufactories for
all plants and animals. Stems vary greatly in the positions
they assume, but their chief functions are to support the
leaves and to conduct food solutions from the root to the
upper-structure of the plant. The two great classes of
stems are monocotyledonous and dicotyledonous.
The stem also usually supports the flower, which consists
in the main of calyx, corolla, stamen, and pistils. The chief
function of the flower is to produce the seeds from which
succeeding generations of plants grow. The enlarged tip of
the stamen is called the anther. This produces pollen
grains. When a pollen grain of the right sort falls on the
head of the pistil, called the stigma, it fertilizes an egg cell
in the ovary, which is at the base of the pistil, thus produc-
ing the embryo of a new plant, which is the living part of a
seed. Pollen grains are carried and spread by the wind and
by insects and birds. The seeds are also scattered by the
wind, by animals, and by flowing streams.
Besides these green plants which prepare their own foods,
there is another great group of plants that may be called
dependent. Instead of preparing their own food by the
help of the sun, they live upon food that has been prepared
by green plants.
Among the familiar dependent plants are mushrooms and
toadstools. Bacteria and yeasts are single-celled dependent
plants. A bacterium reproduces by dividing in two. A
yeast reproduces by budding. Molds are dependent plants
which are\made up of many cells and which reproduce by
spores.
QUESTIONS 423
Animals take their energy indirectly from the foods pre-
pared by green plants or by other animals. They are
usually classed as invertebrate and vertebrate. The lowest
form of invertebrate is the protozoon. Worms and insects
are other forms of invertebrates, the importance of which is
seldom realized.
The bony skeleton in the higher forms of vertebrates
consists of a backbone, skull, ribs, and appendages. In the
skull is the brain, connected with the various parts of the
body by nerves. Vertebrates breathe by receiving air
through the windpipe into the lungs. This is done by the
muscles of the chest and the diaphragm. The lungs purify
the blood, which circulates from the heart through the
arteries and capillaries and returns through the veins.
The five senses are taste, smell, touch, sight, and hearing.
These sensations are carried to the brain by the nerves,
which come from the nose, the mouth, the skin, the eye, and
the ear, respectively. Sound is a wave motion in a material
medium. The ear is a sound transmitter, which conveys
sound vibrations by way of the auditory nerve to the brain.
For all the activities of body and brain food is required.
As the food passes through the alimentary canal, various
juices are mixed with it and certain parts of it are digested
and absorbed into the circulatory system of the body.
QUESTIONS
What are the three parts into which many plants can be readily
separated ?
In what three respects are plants and animals alike?
Of what use to the plant are the roots ? Why are roots necessary
to the higher plants ?
Describe some different kinds of stems that you have seen and
explain their adaptability or lack of adaptability for making
the best of the conditions where they were.
424 LIFE ON THE EARTH
What do the leaves do for the plant ? How do they do it ?
What is the value to the plant of the flower ? How are the flowers
prepared to carry out their part in the life struggle of the plant?
Describe any way in which you know that animals have been of
assistance to plants.
How do plants provide for the dispersal of their seeds?
How does the seed develop into a plant?
With what useful or what harmful chlorophyll-lacking plants
have you ever had experience?
Name and describe some of the invertebrate animals you know.
What is the general structure of the worm ?
What insects have you known that are beneficial ? WThat that
are harmful?
What is the use to the vertebrate of the skeleton and the nervous
system ?.
Describe how vertebrate animals breathe. Why is it vitally
necessary for them to breathe freely?
What is the use of the blood ? How does it get around to where
it is needed?
Describe the ways in which man becomes aware of what is
outside his body.
Why is food needed? How and where is it digested?
CHAPTER XIV
Nitrogen
MAN'S EXISTENCE AS RELATED TO PLANT AND
ANIMAL LIFE, FOODS,
Fundamental Foods. — The elements which enter into
the structure of the human body, such as oxygen, hydrogen,
nitrogen, carbon, etc., are comparatively few and are abun-
dant in the world about us, either separately or in compounds.
But with all of man's ingenuity, he has never learned to
manufacture these ele-
ments into compounds Sulphur
that will serve as food for
the human body.
The leaves of plants
are the fundamental food
factories of the world.
Here carbon, hydrogen,
and oxygen are united by
the aid of the sun into
plant foods called carbohy-
»r I
horusl
tm\
0»ygen
PROPORTIONS OF ELEMENTS IN COMPOSI-
TION OF LIVING THINGS
j 4 , T? 4 A 4 '
drates. Fate and proteins
are two other kinds of
foods that are also manufactured in the bodies of both
plants arid animals, but the carbohydrates are the original
material out of which the living organism, whether plant
or animal, first produces fats and proteins.
Air, water, and salt are necessary to the processes of life,
425
426 FOODS
but they are not generally classed as foods. In leaves
then and in leaves only are the lifeless (inorganic) sub-
stances of the earth combined into substances that will
support life (organic compounds) . The factories of nature
are open to man, and he knows fairly well what these fac-
tories produce. But how the compounds are produced
either in the plant or in the animal and how the active
material of the living cells called protoplasm does its work
are mysteries to him. By careful study, however, man
has learned a great deal as to foods necessary to the growth
and health of the human body.
Necessary Foods. — Experiment 139. — Place in different test
tubes small amounts of (1) corn starch, (2) grape sugar, (3) scrap-
ings from a raw potato, (4) flour, and (5) the white of an egg.
Pour in a little water and shake thoroughly. Drop into each
tube a few drops of the iodine solution prepared in Experiment 120.
Experiment 140. — Place in test tubes small quantities of (1) the
white of a hard-boiled egg, (2) tallow or lard, (3) grape sugar, and
(4) any other food which may be handy. Pour a little concen-
trated nitric acid into each tube and allow to stand for a minute.
Be careful not to get the nitric acid on the clothes or hands. Pour
the acid out into a slop jar and wash the substances with a little
water. Pour off the wash water and pour on a little strong am-
monia. If the substances turn a yellow or orange color, proteins
are present. Which substances contain proteins?
Experiment 141. — Gasoline vapor is very inflammable ; be sure
in this experiment that there is no flame in the room. Place about
a spoonful of (1) both the white and the yellow of an egg, (2) flax-
seed meal, (3) yellow corn meal, (4) white flour, and (5) other
foods it is desired to test in separate evaporating dishes or beakers
near an open window. Pour on these more than enough gasoline
to cover them, and stir thoroughly. Cover the evaporating
dishes and allow to stand for ten or fifteen minutes. Pour the
gasoline off into a beaker and set the beaker outside the window
until the gasoline has evaporated. If there is anything left it
NECESSARY FOODS
427
must have been dissolved from the food. If a substance remains,
place a drop of it on a piece of paper. Smell of it. Try to mix it
with water. Rub it between the fingers. Try any other fat or
oil test of which you can think.
Experiment 142. — In a place where there is a good draft so that
odors will not penetrate the room, burn in an iron spoon over a
Bunsen burner (1) small
pieces of meat, (2) a
little condensed milk or
milk powder, (3) part of
an egg, and (4) any other
food. Is there a residue
left after burning? If
so, this is mineral matter.
In the preceding
experiments we have
dealt with the three
great groups of organic
compounds, carbohy-
drates (starches and
sugars), fats and oils,
and proteins (foods
containing nitrogen) .
The foods that con-
tain large percentages
of carbohydrates are
vegetables, fruits, and
most cereals. The fats
are most abundant in butter, cream, fat meats, nuts, choco-
late, and vegetable oils such as olive and cottonseed oils.
The common foods that are rich in proteins are lean meats,
eggs, beans, peas, and certain cereals, especially oatmeal.
Milk contains all three of these compounds in approximately
the proportions needed by the body.
A DATE PALM
428
FOODS
Careful experiment has shown that the average, full-
grown American needs each day two to three ounces of
proteins, about four ounces of fats, and a pound of carbo-
hydrates. The weight of food eaten, however, is very
much greater than this, as all foods are composed largely of
water, and contain other substances which the body throws
off as waste. The pro-
teins are needed for
growth and repair, since
the living part of the
cells, the protoplasm, is
composed of proteins.
All foods furnish
energy when they are
oxidized in the body.
Until recently it was
thought that a great deal
of meat was necessary to
furnish the energy re-
quired for hard muscular
work. But investigation
has shown that this
energy can better be sup-
plied by carbohydrates
and fats. When carbo-
hydrates and fats are
oxidized in the body to produce energy, the waste is largely
water and carbon dioxide, which the body readily throws off.
But when for lack of carbohydrates the body is compelled to
oxidize proteins to produce energy, certain nitrogen wastes
are produced which the body does not throw off so easily.
Continued strain of throwing off these poisonous wastes in
A BUNCH OF DATES
An excellent food for hot climates.
NECESSARY FOODS
429
large amounts may lead to serious disease. The wide-
spread custom in America of eating meat three times a
day is not only expensive but also unhealthful. A small
amount of meat once a day is all that even a hard-working
man needs.
Where men live in cold regions or are much exposed to
cold, the body requires great. energy to keep up its heat.
SUGAR CANE CUTTING
Fats are the substances that oxidize most readily in the
human body, and these are needed in great abundance by
men who have to withstand exposure to cold. " Fats are
fuels for fighters " was a slogan of literal truth which the
United States Food Commission used on its posters during
the World War. The body readily converts sugars into
energy, and so sugars are also a valuable cold weather food.
The staple food of northern Africa is the date, which is
430
FOODS
admirable for hot climates because it is practically a com-
plete food with a minimum of fats.
Mineral matter such as iron for the red corpuscles, lime
for the bones and teeth, and phosphorus for the protoplasm
must also be included in our food. Eggs furnish all three
of these; milk is rich in lime; but vegetables and the
outer layers of grains contain the main supplies of these
BANANA PLANTS
The bananas grow from the top of the plant in great clusters.
minerals, since vegetable foods are more abundant elements
of diet with most people than either milk or eggs.
Recently other substances called vitamins have been
found necessary to the maintenance of a healthy body.
They are found in fresh (not salt) meats, fresh milk, raw
vegetables and fruits, and in the outer layers of grains.
Since heat drives off these vitamins, we must rely mainly
NECESSARY FOODS 431
upon raw fruits and raw vegetables for our supply of these
substances. Even the slight heat necessary to pasteurize
milk drives off the vitamins.
A study of the few facts that have been presented
here will indicate that vegetables and fruit should form a
much larger proportion of the American diet than they now
do. Men who live almost exclusively on white bread and
meat are starving their bodies for certain very necessary
substances, and are overworking their systems to throw
off poisonous wastes. When the Food Commission asked
during the World War that we eat less meat and more of
the dark breads containing the outer layers, or brans, of the
cereals, they were asking us to do ourselves as well as our
soldiers and the Allied peoples a favor.
Besides the necessary foods, most individuals desire
especial additions for relishes and beverages. These com-
monly consist of spices, tea .and coffee, and other like ma-
terials. When used in moderation, they are usually harm-
less. But they should be avoided by children and not used
to excess by adults.
Alcohol, except possibly in exceedingly small quantities,
cannot be considered a food, and as a stimulator for the
appetite it should not be used. Many careful experiments
have shown that while it may stimulate the body tempo-
rarily, it does not enable it to do more work. Instead,
those using it cannot do as much work, or withstand as
great physical or mental strain, as those not using it.
Even if it were not for the ungovernable appetite which
its use almost invariably engenders, and for the degrading
influences with which its use is usually surrounded, its
physiological action is such as to lessen the body's vitality,
decrease its resistance to disease, and dull its nervous and
432
FOODS
mental efficiency. So surely do deteriorating results follow
its steady use that insurance companies regard men who
use alcohol as bad risks. Railroads and many great in-
dustries refuse to employ users of alcohol.
COFFEE PLANT
Showing the clusters of beans from which coffee is produced.
Whatever scientists may conclude as to the food value of
minute quantities of alcohol, they agree that as a steadv
" stimulating " beverage, it must be classed as a poison.
Careful scientific experiments have also been made upon
the effect of tobacco. Although there are differences of
PREPARATION OF FOODS 433
opinion about its effect upon fully matured adults, there
is no such difference of opinion in regard to its effect upon
those who have not stopped growing and are not yet fully
matured.
Measurements and comparisons made in regard to the
physical development, endurance, and mental ability of
a large number of college men have shown conclusively that
those who have not used tobacco, as a rule, have better
physiques, are better students, and can stand more physical
exercise than those who have used it. In the competition
for athletic teams it is found that only about half as many
of those who have used tobacco make good, as of those who
have not used it.
Preparation of Foods. — When foods are appetizing,
look good, smell good, and taste good, both the saliva and
the gastric juice are secreted in larger quantities, so that
this sort of food, when taken into the system, is more read-
ily digested than food which is not attractive. One of the
reasons for cooking food is to render it appetizing, and
this should never be lost sight of by the cook. Cooking
also softens and loosens the fibers of meats and causes the
cell walls of the starch granules to burst, thus rendering
it possible for the digestive juices to attack the food more
readily. In addition, cooking kills the germs and other
parasites that are sometimes found in foods.
To cook food properly is a fine art and requires most
careful study and great skill. The science of providing
economically the kinds of food necessary and of cooking
these properly so that they will be attractive, easily digested
and will lose none of their nutritive value, is one that is at
present in its infancy. Human beings, like other animals,
434
FOODS
ANCIENT COOKING UTENSILS
must have a balanced ration or diet if they are to be most
productive economically. They differ from other animals
in having a much greater range of food possibilities and in
being much more sensitive as to the appearance and taste
of food.
ONE DAY'S BALANCED RATION FOB FIVE PERSONS
PLANTS THAT CHANGE FOOD
435
Plants That Change Food. — If it were not for microscopic
plants (page 398), food would keep indefinitely without
change. These little plants are, however, present every-
where and if conditions are suitable for their growth they
begin at once to change or to " spoil " all foods they can
reach. Some of the bacterial changes make food more
BREAD MOLD. (Greatly magnified.)
palatable, for it is bacteria that give the fine flavors to' the
best butter and cheeses and the gamy flavor to certain kinds
of meat. Bacteria also change cider into vinegar.
Experiment 143 (Teacher's Experiment). — Make a solution of
molasses and water. Place some yeast in it and put the mixture
away in a warm place. Watch it for a few days, and after gas
bubbles have been coming off for some time put the solution in a
flask connected with a distilling apparatus, as shown in Figure 136.
Gently heat the solution and collect the distillate. Smell of the
distillate. What does it smell like? Dip a piece of cotton cloth
in it and touch a lighted match to it. If the experiment has been
successful, the distillate will burn. If not, distill some of the
distillate again. Alcohol and carbon dioxide are produced by the
action of the yeast on the molasses and the alcohol is evaporated
by low heat and condensed in the still.
436
FOODS
The ancient Egyptians knew that if flour was mixed with
water and left in a warm place it would soon become
porous ; and that if pieces of this porous dough were put into
FIGURE 136
other dough, they would make this dough become porous
more quickly. These pieces of dough were called leaven,
and the leavened bread of the ancients was made in this
way. Even to-day in some countries this method is fol-
lowed. The Romans
sometimes used a leaven
made out of grape juice
and millet. In these
methods, the wild yeast
plants which exist al-
most everywhere in the
air found a favorable
lodging in the prepared substance, and by their growth
and activities " raised " the bread. Later, methods were
devised for cultivating the yeast plants, and the making
of " raised " bread became common.
YEAST PLANTS
PLANTS THAT CHANGE FOOD
437
In modern bread making, yeast, which contains the
minute yeast plants, is mixed thoroughly into the material
which is to compose the bread; and the bread is then put
into a warm place to rise — or, more exactly, to allow the
yeast plants to multiply. If the materials and the tem-
perature are right, the yeast plants multiply very rapidly,
feeding upon the material of the dough, and changing sugar
into carbon dioxide and alcohol. Little bubbles of carbon
dioxide gas are developed throughout the dough, making
it slightly porous.
The dough is then kneaded to develop the elasticity of
the gluten and to mix the greatly increased number of yeast
BREAD MAKING IN MEXICO
plants uniformly through the mass. It is then set aside
again so that the uniformly scattered yeast plants may con-
tinue their activities. Bubbles of carbon dioxide form
throughout the whole mass, and a light spongy dough
results. When this is heated in the oven, the tiny bubbles
of gas expand, making a more porous sponge, the alcohol
evaporates, and the dough bakes, thus forming light bread.
438 FOODS
Sometimes other substances besides yeast are used to
generate the carbon dioxide necessary to raise the dough.
In Experiment 26, it was found that the action of an acid
on certain substances liberated carbon dioxide. Often in
making biscuits and cake, soda and sour milk are used.
The gas is liberated by the action of the acid in the sour
milk upon the baking soda. Baking powder, which usually
consists of baking soda and cream of tartar mixed with corn-
starch, is also used. When the baking powder is mixed
with flour and moistened, the cream of tartar acts like an
acid upon the soda, liberating carbon dioxide and thus
causing the dough to rise. As in bread, the gas is expanded
by the heat of the oven, making the cake or the biscuits
more porous.
Most of the minute plants which cause changes in food
render it unfit for man's use. We have found that decay,
which is caused by bacteria, is on the whole a friendly pro-
cess. But we look upon it as an unfriendly process when
it results in the souring of milk, the tainting of meat, the
spoiling of eggs, and the rotting of vegetables — all of
which are due to the activities of bacteria.
The decay in fruit, the mold on bread, the corn smut,
the smut on oats and barley, the potato blight, the scabs
of apples and potatoes, the rusts on grains, and many other
common plant diseases are simply fungous plant growths.
The wheat rust alone costs the United States many millions
of dollars each year. Thousands of feet of timber are de-
stroyed yearly by the wood-destroying fungi. Dry rot of
timber, as it is called, is due to a fungous growth. The fight
against these harmful fungi costs millions of dollars each year.
Experiment 144. — Place a slice of freshly boiled potato in each
of six clean, 4-ounce, wide-mouthed bottles. Close the mouths of
PLANTS THAT CHANGE FOOD 439
the bottles with loose wads of absorbent cotton. Place five of
these bottles in a sterilizer and sterilize for half an hour. Allow
the sixth bottle to remain unsterilized. (A sterilizer can be made
by taking a covered tin pail and putting into the bottom of it a
bent piece of tin with holes punched in it to act as a shelf on which
to put the bottles. A shallow tin dish with holes in it is good for
the shelf. There must be holes so that the steam will not get under
the shelf and upset it. Fill the sterilizer with water to the top of
the shelf and place the bottles on the shelf. Keep the water boil-
ing.) A reliable, inexpensive sterilizer is the pressure cooker shown
on page 126.
Take the bottles out and allow them to cool. Remove the cotton
from one of them for several minutes and then replace. Run a
hat pin two or three times through the flame of a Bunsen burner to
sterilize it and place it in the water of a vase which has had flowers
in it for some time. Carefully pulling aside the edge of the absorb-
ent-cotton stopper in the second bottle, insert the pin and place
a drop of the vase water on the surface of the piece of potato.
After having sterilized the pin again, rub it several times over the
moistened palm of the hand and then, using the same precautions
as before, scratch the potato in the third bottle. Put a fly in the
fourth bottle, using the same precautions. Keep the fifth bottle
just as it wTas taken from the sterilizer as an indicator, that is,
to see whether the bottles were thoroughly sterilized. Put all
of the bottles away in a warm place and observe them each day for
several days. The spots appearing on the pieces of potato are
bacteria colonies.
Since bacteria and fungi cause the " spoiling " of food,
and since certain bacteria develop poisons called
ptomaines which make the eating of the food infected very
dangerous, it is necessary that food be protected as far as
possible from bacteria and that their growth be checked.
Food should never be handled except with clean hands;
it should be most carefully protected from dust and flies
and kept in a clean, cool place. Most bacteria do not thrive
where it is cold.
440
FOODS
Preserving Food. — When it is desired to preserve food
for a long time, especial care must be taken. It has been
found that thoroughly drying food will protect it against
bacteria ; that freezing or smoking fish and meat preserves
them ; that salt and vinegar and spices act as preservatives ;
that if fruits and vegetables are heated for some time at a
boiling temperature and tightly sealed in cans they will
keep ; that fruits do
not spoil if placed in
strong sugar sirups;
that fruits and vege-
tables and eggs can be
kept without spoiling
where the tempera-
ture is maintained
at a little above the
freezing point.
In all these cases
the bacteria in the
food are either en-
tirely destroyed and
the food is absolutely
protected from other
bacteria, or else the growth of the bacteria is completely
checked. Sometimes eggs are preserved for a considerable
time by placing them in a waterglass solution. In this
case the waterglass fills up the tiny pores in the shell of the
egg and keeps out the bacteria just as paint keeps them
out of wood. In the case of the egg, however, there is plenty
of moisture within the egg for the growth of whatever bac-
teria may be present, whereas in painted dry wood the
moisture is kept out and the bacteria are unable to grow.
PREPARING SMOKED FISH AT GLOUCESTER
BACTERIAL DISEASES
441
In order to keep bacteria from spoiling meat, borax is
sometimes used. Formalin is sometimes put into milk
to keep it from souring, and benzoate of soda into catsups
Courtesy of Beech-Nut Packing Co.
STERILIZING CATSUP AND CHILI SAUCE
The metal baskets filled with bottles of chili sauce and catsup are lowered
into the sterilizing tanks, which are constructed on the principle of the
pressure cooker (page 126). Notice the abundant lighting and scrupu-
lous cleanliness of the room.
for the same reason. These three substances act as preserv-
atives, but they also make the food unwholesome and so we
have pure food laws prohibiting the use of such preserva-
tives for foods.
Bacterial Diseases. — Out of the fifteen hundred or more
kinds of bacteria that are known, only about seventy may
grow in our bodies and make us ill. Most of the others are
442 FOODS
man's efficient helpers. These disease-causing bacteria, how-
ever, may cause a vast amount of trouble. The microscopic
plants and animals that cause disease are commonly called
germs.
Almost all disease germs get into the body through a
break in the skin Or through the mouth or nose. The skin
when unbroken is a splendid germ armor. When it is
broken, the bacteria have a chance to enter. In the ma-
jority of cases there are not enough hostile bacteria at hand
to make serious trouble; but
there is always a chance of their
being present, and so all wounds
ought to be cleansed, disinfected
and dressed with absorbent
cotton, or some similar sub-
stance. We found in Experi-
ment 144 that absorbent cotton
kept the bacteria out. If wounds
are not given careful attention,
blood-poisoning, which is a bac-
FIRST AID KIT -IT . • o
tenal disease, may set in. Some-
times when a rusty nail or other dirty substance breaks
through the skin, bacteria are carried into the flesh. If
such a wound is not properly disinfected and cared for,
lockjaw, another bacterial disease, may be developed.
By getting into the body through the mouth or nose,
bacteria cause many other diseases. Among these are
influenza (grippe), diphtheria, pneumonia, whooping-cough,
typhoid fever, and tuberculosis. People having diseases of
these kinds throw off a great number of bacteria. If such
germs get into the bodies of other people, they may cause
the same diseases there. Disease germs usually do not
BACTERIAL DISEASES 443
float in the air for any great distance from the diseased person.
But danger lurks in handling articles infected by germs,
from eating infected food, or from drinking infected water.
All dishes and utensils used by persons having contagious
or infectious diseases should be kept by themselves, washed
in boiling water, and not used by other people. All their
bedding and clothing should be thoroughly washed in some
disinfectant, boiled if possible, and hung for some time in
direct sunlight. Rooms should be disinfected before they
are used by other persons. In very contagious diseases
mattresses and materials which cannot be disinfected should
be burned. As all germ diseases are spread by sick people,
epidemics can be prevented if sufficient care is taken.
So closely are people brought together in our towns and
cities that carelessness on the part of one may endanger
many, and it is particularly necessary that regulations be
enforced which shall protect society from the careless spread-
ing of disease. In some very virulent diseases, such as
smallpox or diphtheria, the patients ought to be kept to
themselves, quarantined, their rooms and everything about
them disinfected, and every precaution taken to prevent
people susceptible to the diseases from being exposed to the
germs.
This cannot and ought not to be done in all cases of bac-
terial disease, since adequate protection can be given if
sufficient care is taken by the person affected. If tubercular
patients will carefully cover their mouths with cloths when
coughing or sneezing and see that the cloths are burned,
tubercular germs will cease to be a menace to society. Al-
though thousands are afflicted each year with tuberculosis,
largely through the carelessness of those having it, the disease
is readily preventable and curable. If the same precautions
444 FOODS
are taken in whooping cough or grippe, or ordinary " cold/5
the infection will not be spread.
As we said before, the fight put up by the white cor-
puscles is not the only fight the body makes against bac-
teria and their activities. When disease bacteria get es-
tablished in the system, they secrete a poison called toxin,
which is absorbed by the blood and carried throughout
the body, thus poisoning many other parts beside those im-
mediately attacked by the bacteria. The cells of the body
at once begin to secrete a substance to counteract this
poison, an antitoxin. If the vitality of the patient is great
enough, sufficient antitoxin will be secreted to neutralize
the effect of the toxin and the disease will be overcome.
Of late years it has been found that these antitoxins
can be artificially supplied or caused to develop. Thus
the system may be aided in neutralizing the effect of the
toxin, and in warding off the disease. By injecting these
antitoxins or stimulating their development, people are now
protected against smallpox, diphtheria, and other diseases.
So carefully are these preparations made at present that
if proper care is taken in their injection, there is almost
never any ill effect from their use.
How to Disinfect. — Most bacteria thrive best at a mod-
erate temperature (70° to 95° F.). Almost all of them are
killed if kept at a boiling temperature for a short time.
They cannot grow where there is no moisture, and all but
a few kinds are killed by complete drying. Direct sunlight
is soon fatal to them.
For disinfecting wounds, iodine or a dilute solution of
carbolic acid or lysol serves well. (These must not be taken
internally.) Hydrogen peroxide is a good external cleanser
DANGERS FROM INFECTED FOOD AND WATER 445
and has some disinfecting qualities. Cinders may often be
washed out of the eye and the eye disinfected with a dilute
solution of boracic acid. Strong disinfectants should never
be used in the eyes or nose. A solution of listerine is a
safe mouth wash.
For disinfecting sinks or washbowls a generous quantity
of boiling water containing a small amount of carbolic acid
or lysol is very effective. Chloride of lime is the most com-
mon disinfectant for sewage pipes leading from bathrooms.
Woodwork and wall fixtures may be wiped
with a dilute solution of carbolic acid or
formalin. It must be remembered that
some of these household disinfectants are
deadly poisons if taken internally.
Rooms are disinfected by burning sul-
phur in them. The sulphur gas will not be
effective, however, unless the atmosphere
of the room is very moist. Moisture
can be supplied to the atmosphere by
thoroughly spraying the room with a fine
atomizer or by boiling water in it for some
time. Formaldehyde candles (Figure 137) are also burned
in rooms to disinfect them. These have proved quite
satisfactory. Soap and water, sunlight and air, are the
only disinfectants needed for rooms except in case of con-
tagious or infectious diseases.
Dangers from Infected Food and Water. — If foods are
handled by diseased persons or by. those whose dirty hands
have acquired disease bacteria, or if the foods are allowed to
stand exposed to dust and dirt, they collect germs. If the
food is afterward thoroughly cooked, the germs are gener-
FlGTJRE 137
446
FOODS
ally killed. If, however, as in the case of bread, fruit,
and some vegetables, no cooking is done before the foods
are eaten, the foods may often carry disease.
Milk is particularly liable to be infected with disease
germs because they readily grow in it and increase rapidly.
Many epidemics of
typhoid fever, scarlet
fever, diphtheria, and
other germ diseases
have been directly
traced to polluted
milk. Either the
milk came directly
from dairies where
these diseases existed,
or had been put into
bottles taken from in-
fected homes and not
afterward sterilized.
The older such milk
becomes the greater
is the danger of using
it since bacteria mul-
tiply in it with such
tremendous rapidity.
Infants are particularly liable to contract diseases from
impure milk because this is their main diet. Statistics
show that a large percentage of infant deaths are caused by
infected milk. If milk is scalded the germs are killed, but
scalding makes milk less palatable and less digestible.
When milk is thoroughly heated to a temperature of 160°
F. for fifteen or twenty minutes, the disease germs are
MILK DELIVERY IN BELGIUM
DANGERS FROM INFECTED FOOD AND WATER 447
A SIMPLE PASTEUR-
IZING OUTFIT
killed but the milk itself is not made less digestible nor is
its taste affected. This is called pasteurization. The
milk should be cooled quickly after it is heated, covered with
absorbent cotton, and kept in a refrigerator so that fresh
germs cannot infect it. Pasteurized milk
is the only safe milk to use unless it is
absolutely known that great care has been
taken to keep the milk at all times clean
and cold enough to be safe from infec-
tion. Certain cities require that all milk
sold shall either come from healthy cows in
dairies of " certified " cleanliness or else
shall be pasteurized. Refrigerators and
places where milk and food are kept must
be washed and thoroughly scalded with hot water frequently
if they are to be kept free from bacterial infection.
Water is also a dangerous carrier of bacteria. Water
from deep artesian wells is usually safe, but streams that
flow over the surface of the ground continually have washed
into them materials which contain germs. Unless great
care is taken to keep surface water out of springs or
wells and to keep the drainage from stables and out-
buildings from seeping into them, they become dangerous
as sources of water supply. Impure water is an ever active
source of disease and one that cannot be too carefully
watched.
Many of our large cities have in recent years expended
vast sums of money upon their water supplies in order that
citizens may be protected as far as possible from disease.
The drainage canal which Chicago built at great expense to
divert its sewage from Lake Michigan greatly lowered the
death rate from typhoid fever in that city. Further de-
448 FOODS
crease in typhoid and intestinal diseases in Chicago is due to
the fact that a large part of the milk which is now used there
is pasteurized. Care concerning these two most important
supplies, water and milk, has greatly decreased the death
rate in many American cities during the present century.
It is estimated that the actual money loss each year in the
A WELL WITH CONTAMINATED WATER SUPPLY
United States because of the ravages of preventable diseases
is between one and two billion dollars.
When there is any doubt about the purity of water it
should be boiled. This will kill the dangerous bacteria.
Ordinary house filters are useless and often worse than use-
less, as they simply become breeding places for bacteria.
They may make the water look clearer but they do not
destroy the bacteria; and it is the bacteria, not the solid
matter, that constitute the real danger.
SEWAGE DISPOSAL
449
Bacteria can live and grow in such minute cracks that
to use dishes washed in impure water is about as dangerous
as to drink the water. All public towels
and drinking cups should be abolished.
Experiments have shown that even drinking
fountains unless most carefully constructed
are liable to retain in the pipes germs left
by other users. The use of the individual
cup is the one safe method for drinking.
o TV- i rr<i_ j- i PAPER DRINKING
Sewage Disposal. — 1 he proper disposal QUP
of human waste is a vital problem. Ex-
posure to wind and flies allows the germs in it to be spread
about. The waste must therefore be disposed of in some
way or disinfected. On the farm or in small towns where
Courtesy of Department of Public Works, Columbus, Ohio
SEWAGE DISPOSAL BED, SOLIDS
450
FOODS
running water can be supplied, cesspools and septic tanks
answer the purpose. In cities, however, most complicated
systems of sewage disposal must be employed. In the
most healthful cities the sewage is gathered from all parts
of the city by means of water flowing in underground sewers.
In seaboard cities the sewers usually empty into the sea and
the tides and currents dispose of the sewage.
Courtesy of Department of Public Works, Columbvs, Ohio
SEWAGE DISPOSAL, LIQUIDS
Cities upon large rivers frequently empty their sewage
into the rivers, but this pollutes the water far downstream.
A very much better way than this has of late years been
devised and is being used by many inland cities. Sewage
disposal plants are built, where the sewage is run into large
tanks and the solid matter is decomposed by the action
of certain kinds of bacteria. The liquid is then slowly
CLEANLINESS
451
filtered through beds of sand and gravel, and the .sewage is
thus freed of organic impurities.
Cleanliness. — Every year we are learning more and more
about disease. The World War has demonstrated in a
wonderful manner the advances which have been made in
A PRIMITIVE WASHING SCENE IN MEXICO
life saving as well as in life destruction. Diseases like small-
pox, typhoid fever, and bubonic plague, which were for-
merly dreaded so greatly by armies, have been practically
eradicated. Wounds which only a few years ago were al-
ways fatal are now easily healed. All of this has come about
because of our increased knowledge of disease germs and
how to combat them.
452
FOODS
Prominent, however, above everything else stands out
the fact that cleanliness is the great protector of health.
Those communities that have well-built sewers, clean streets,
clean milk, and clean water are healthy. The community
through its boards of health must protect the individual
from the germs of contagious and infectious diseases, for
he cannot do this by himself. Persons that eat pure food,
drink pure water, breathe pure air, and keep their bodies
pure are usually healthy.
The Americans were able to build the Panama Canal
because they were able to protect the workmen from disease
germs. Disease had defeated previous attempts. They
were able to make Havana, Cuba, a healthy and healthful
city — although for years it had been one of the plague
spots of the world
- by cleaning it up
and destroying the
breeding places of
disease germs.
Animal Life that
Causes or Spreads
Disease. — Certain
low forms of animal
life, the protozoa,
have already been
mentioned as disease producers. Unlike bacteria, the pro-
tozoa do not cause disease by passing directly from one
person to another. Instead, they need to live in some insect
between whiles. In malaria and yellow fever the insect
in which they live is the mosquito, and in the sleeping sick-
ness they live in a fly called the tsetse. If a mosquito of
A DISEASE-BEARING MOSQUITO
The mosquito is greatly magnified.
ANIMAL LIFE THAT SPREADS DISEASE
453
the right species bites a person afflicted with malaria or
yellow fever, some of these little animals, the protozoa, are
sucked up with the blood and enter
the mosquito. They grow in its body,
undergoing several changes, until the
animal germs are ready to be injected
into their victim, when they pass into
the salivary glands of the mosquito.
In biting, the mosquito always injects
a little saliva into the wound and with
this go the germs. These enter the
blood, multiply rapidly, and cause the
disease.
If mosquitoes can be kept from biting
people who have these diseases or if
infected mosquitoes can be kept from biting other people,
such diseases will not spread. The best way to keep
AMOEBA DIVIDING
A "MALARIAL" SWAMP
A breeding place for mosquitoes.
454
FOODS
mosquitoes from biting is to exterminate them. Since
mosquitoes breed in stagnant water, all old ditches or
small pools where water accumulates should be emptied and
drained. Larger stagnant pools should be drained or have
a film of kerosene spread over their surface by frequently
pouring a little of the oil on the water. This will keep the
mosquitoes from breeding and prevent the diseases.
The Texas fever, which has caused such great financial
losses to the cattlemen of the United States, is caused by a
protozoan injected into the cattle by the bite of a tick.
Bubonic plague, the " Black Death " that swept Europe
during the Middle Ages, is spread by the bite of a flea that
lives on plague-infested rats. Hundreds of thousands of
dollars have been spent by the Government in killing rats
in some of the ports of the United States where the plague
has succeeded in landing. Many seaports are now rat-
proofing their wharves in an effort to exterminate these pests.
The cables holding ships to the
docks are often passed through
holes in the centers of metal
sheets in order to prevent rats
from entering a ship by walking
along the cables. Sailors have
learned that if the rats are kept
out, the plague is kept out.
HOUSE FLY (Magnified)
Flies. — The words fly and
filth are almost synonymous.
Flies breed in any kind of de-
caying vegetable or animal matter. The eggs hatch in
about a day and the little white maggots after absorbing
filth for about ten days change into adult flies with their
HEALTH HINTS
455
hairy bodies and sticky feet, especially adapted for carrying
all kinds of germs and for spreading them over everything
they touch. The fly delights to feed on all kinds of foul or
diseased objects, and the waste it deposits is often full of
dangerous germs.
" Swat the fly " is indeed a proper slogan. But a still
better plan would be to destroy all filth or to dispose of it
so as to prevent flies from breeding. Flies never travel far
and their presence indicates filth in the neighborhood. If
manure and other decaying matter
is kept in covered pits until it is
used for fertilizing, and if garbage
cans are kept covered, much
mere will be done to exterminate
the fly than by swatting. Houses
should be carefully screened and
all food kept covered from these
carriers of disease, but along with
all precautions to avoid the fly
must go consistent efforts to
exterminate the fly.
BACTERIA COLONIES
These were developed from the
tracks of a fly on a gelatine
plate.
Health Hints. — Good health is man's greatest asset.
If he is to attain his highest power he must maintain his
health. His muscles must be exercised so as to stimulate
the cells to grow and to throw off their waste products.
The skin must be frequently bathed so as to remove the dirt
and waste materials that clog the pores. The body must
have sufficient rest and sleep so that the cells will not be
worn out faster than they can be reproduced.
One must have plenty of food but not too much, or the
stomach and other organs will suffer from overwork. The
456 FOODS
use of stimulants, such as tobacco, alcohol, and all other
harmful drugs must be avoided since all of these interfere
with the proper growth, development, and work of the
various cells of the body. The cure-all patent medicines,
which do not cure at all but which simply dope the sen-
sibilities of the individual, should be shunned as poison.
Fresh air and sunshine are the best and surest preventives
of disease ; and when these are combined with proper rest,
food, clothing, exercise, and bodily cleanliness, there is little
danger of sickness except from highly contagious diseases.
Every day each person probably receives into his system
thousands of disease germs. Usually it is only when the
vitality of the body is low that these germs are able to es-
tablish themselves. Right living is the great disease pre-
venter.
SUMMARY
The elements which enter into the composition of the
human body, such as hydrogen, oxygen, nitrogen, carbon,
etc., are comparatively few and are abundant in the world
about us. As foods they are found in three classes of
compounds, carbohydrates, fats, and proteins. All foods
furnish energy when they are oxidized in the human body.
Proteins are especially needed for growth and repair of
tissues ; but since it is easier for the body to throw off wastes
from oxidized carbohydrates and fats, these should constitute
the largest part of our energy-producing diet. Men exposed
to cold need sugar and fats in greater abundance than
those who live much indoors or in warm climates. Foods
containing iron, phosphorus, lime, and vitamins are also
essential in the diet of all persons. Spices, tea, and coffee
should be used in moderation by adults and avoided by
SUMMARY 457
children. Tobacco is positively harmful to immature
persons, and alcohol as a beverage or common stimulant
must be classed as a poison. Proper cooking renders most
food both more palatable and more digestible.
Microscopic dependent plants cause changes in food. The
yeast plant is employed in bread making ; certain bacteria
change cider to vinegar; and others are responsible for the
fine flavors of the best butter, cheeses, and certain kinds
of meat. Still other bacteria cause foods to spoil. To
preserve food against such bacteria, we dry it, freeze it,
smoke it, boil it, and seal it in air-tight receptacles ; or employ
sugar, salt, spices, or vinegar as preservatives.
Some bacteria enter the body and cause diseases. This
explains why we disinfect wounds, quarantine persons suf-
fering from infectious diseases, and cleanse thoroughly or
destroy all household articles with which such people come
in contact. The body fights disease germs by means of the
white corpuscles of the blood and by means of antitoxin
secreted by the cells of the body. Every household should be
supplied with certain common disinfectants; and every
household and community should guard against infected
food and water, and attend to the proper disposal of waste
and sewage. One of the most effective means of combating
or preventing disease is to maintain cleanliness.
Flies are great carriers of disease bacteria, and certain
kinds of mosquitoes, fleas, and other insects cause diseases
by injecting disease-producing protozoa into the blood of
victims.
Exercise, bathing, nutritious food, proper clothing, fresh
air, sunshine, sufficient rest and sleep, avoidance of harmful
stimulants and drugs, shunning of cure-all patent medicines,
and cheerfulness are among the essentials to health.
458 FOODS
QUESTIONS
What are the three great groups into which foods are4 divided?
Why are fruits and vegetables so necessary ?
Why should not alcohol and tobacco be used ?
What are the advantages derived from proper cooking ?
What is the value of yeast in bread making? Describe and
give reasons for the process usually employed in bread making.
Why are some bacteria and other minute plants so harmful ?
How can food be preserved and kept wholesome ?
What should one do to protect himself from bacterial diseases ?
How should milk and water be cared for? Why?
Why is cleanliness so essential to health?
Why should people take especial care to protect themselves from
mosquitoes and flies ?
CHAPTER XV
MAN'S INVENTIONS FOR TRANSFERRING AND TRANS-
FORMING ENERGY
Tools. — Primitive man early found that it was to his
advantage to use something besides his own hands and feet
to apply his energy. Probably the first tool that he used
was a stone which he threw at some animal he wished to
kill for food. Soon he found *
that if he put the stone in
a strip of hide and swung
it around his head, he could
send it with greater force.
Thus he invented the sling,
probably the first device
for transferring energy and
the first war machine.
Since then he has not
only invented many ma-
chines that have enabled
him to exert his own physi-
cal energy to greater advantage, but he has also devised
machines which make it possible for him to use the energy
that exists in the world about him. This ability to utilize
the energy of nature has made the life of modern man very
different from that of his 'savage ancestors. Without ma-
chines there could be no large cities, no manufacturing,
459
MAN'S FIRST WAR MACHINE
460 TRANSFERRING AND TRANSFORMING ENERGY
HAND GRENADE THROWING
The utilization of hand throwing in modern warfare.
U. S. Official
no transportation facilities, none of the conveniences that
make mocfern life comfortable.
More and more man is relying upon machines driven by
nature's energy to
do the work he has
heretofore done by
his own physical
exertion. The mow-
\
ing-machine, the sew-
ing-machine, and the
automobile are recent
examples of such in-
ventions. All these
intricate devices,
however, have a few
simple machines as
U. S. Official
BATTLE "TANK"
A modern complex war machine.
FRICTION
461
SPINNING WHEEL
A most useful application of simple machines. Spinning is now done
by much more complex machinery.
their basis. These basic machines are the lever, the wheel
and axle, the pulley, the inclined plane, the wedge, and
the screw.
Friction. — If we attempt to slide a box along a level
floor, we find that we have to overcome resistance or do
462 TRANSFERRING AND TRANSFORMING ENERGY
work. If we put rollers under the box there is less resist-
ance, but some resistance always develops when two sur-
faces are moved over each other. This resistance is
called friction. The rougher the two surfaces, the more
the friction ; and the
smoother they are,
the less the friction.
To lessen friction
we make surfaces
that slide over each
other very smoothly
and oil them. Roll-
ing surfaces are found
to have less friction
than flat surfaces,
and so we use ball
or cylinder bearings
BBI in bicycles, automo-
biles, and many other
machines. But no
matter what we do,
some of the work
exerted on a machine
is always used up in
overcoming friction.
In an efficient machine the friction is reduced in every
possible way in order to avoid as far as possible " loss of
energy." In some of the simple machines, especially the
wedge and the screw, friction is always so great that the
machines are not very efficient.
The Lever. — Experiment 145. — (a) Bore a small hole through
a meter-stick at each of the decimeter divisions. Place on the table
INDIAN WEAVING
A form of skilled manual labor which modern
machinery has almost done away with.
THE LEVER
463
a small board so that its edge shall be even with the edge of the
table. Weight or clamp the board to the table. Into the edge of
the board drive a round-finish, small-headed nail so that it will
FIGURE 138
project horizontally over the edge of the table. Slip the nail
through the center hole of the meter stick. (Figure 138.)
Hang a weight of 400 g. from the first decimeter hole. Find
out how much weight will be required at each of several holes on
the other side of the nail in order to
balance the 400 g. weight. In each case,
multiply the weight on each side of the
nail by its distance from the nail and
compare the results. Lift one end of the
meter-stick 10 cm. above the edge of the
table, and note how far each weight
moves. Multiply each weight by the
distance it moved up or down, and com-
pare the results.
(6) Attach a small spring balance by a
short string to one of the end holes of the
meter-stick. Slip the nail through the
hole next to it. Hang a weight of 400 g.
from any one of the other holes. Pull
down on the spring balance until the
meter-stick is in a horizontal position.
Note the pull on the spring balance and
make the same computations as in (a). Repeat the experiment and
computations by hanging the weight from several different holes.
(Exact accuracy in these experiments would require a considera-
tion of the weight of the meter-stick itself, but for the purposes of
this experiment, results will be nearly enough accurate without this.)
FAMILIAR APPLICATIONS
OF THE LEVER
464 TRANSFERRING AND TRANSFORMING ENERGY
The lever was probably one of the first machines used
by primitive man. He pried up rocks and pried open
logs to get the roots and small animals he needed. It
was to him simply a convenient way of using a stick. But
— when Archimedes,
the greatest mathe-
matician of ancient
times, worked out
the principle of this
simple machine, he
was so much im-
pressed with the
mechanical advan-
tage to be derived
from its use that he
said, " Give me a
fulcrum on which to
rest and I will move
the earth."
He found, as was
indicated in Experi-
ment 145, that the
longer the power arm
is than the weight
arm, the greater is
the weight a given
force can lift, but
the smaller the dis-
tance it can lift it. If the experiment could have been accu-
rately conducted, it would also have proved that the power
multiplied by the distance the power moves is equal to the
weight multiplied by the distance the weight moves.
GRINDING CORN, SCOTCH HIGHLANDS
A simple application of the lever.
WHEEL AND AXLE
465
Careful experiment
has shown that this
last statement is true
for all machines, and
so it is sometimes
called the law of ma-
chines. It can be
stated in another
way : What is gained
in power is lost in
speed and what is
gained in speed is
lost in power. Notice
the machines you are
familiar with and ob-
serve how this law
holds good. All of
us are using different
kinds of levers every
day. Balances, scissors, nutcrackers, wheelbarrows, for-
ceps, and the treadle of a sewing-machine are all ex-
amples of levers.
Wheel and Axle. — The windlass used
to lift water out of a well and the cap-
stan of a boat are the most familiar
examples of this form of
machine. (Figure 139.) The
wheel and axle is simply a
modification of the lever.
(Figure 140.) The power
travels through the distance
FIGURE 139 of the circumference of one FIGURE 140
THE LEVER AS USED BY THE ROMANS FOR
WEIGHING
These scales were dug up at Pompeii and are
about 2000 years old.
466 TRANSFERRING AND TRANSFORMING ENERGY
wheel (A) while the weight travels through the distance
of the circumference of the other wheel, or axle (C). If
the circumference of the power wheel is three times the
circumference of the weight wheel, a force of 5 pounds
exerted on the power wheel
will lift a weight of 15
pounds on the weight wheel.
The Pulley. — Experiment
146. — (a) After well oiling
some small pulleys arrange one
of them as in Figure 141, hav-
ing a weight of about 500 g.
^ ^*r on one end of the cord and a
i~i . r~i r"S spring balance on the other.
§ Hfrl |gr I iff" Slowly pull down on the spring
FIGURE 141 ' FIGURE 142 FIGURE 143 balance and note the reading
on the scale. Allow the balance
to rise and note the reading. Friction accounts for the difference
between the first and the second reading of the scale. Average
the two readings and see how nearly the average equals the weight
on the other end of the cord. May we say that the force exerted
by the hand is equal to the weight? Does the hand
move through the same distance as the weight ?
(6) Arrange the pulleys as in Figure 142. Allow the
balance to descend, noting the force recorded on the
scale. Pull up on the balance, noting again the reading
on the scale. Find the average between the two forces,
which may be called the true force. Is the force now
^exerted by the hand equal to the weight? If not,
what are the relations of these two forces?
Note the distance moved by the hand and also the distance
moved by the weight. How do they compare?
(c) Arrange the pulleys as in Figure 143. Make determinations
similar to those in (a) and (6) . How does the force exerted by the
hand now compare with the weight ? How does the distance moved
by the hand compare with that moved by the weight ?
FIGURE 144
THE PULLEY
467
It is sometimes exceedingly convenient to change the
direction of a force even if no other advantage is gained.
To do this, a rope may be passed over a wheel, and thus
one may by pulling down lift up the weight. Such an ar-
rangement is called a fixed pulley. (Figure 141.) The cord
COMBINATION OF PULLEYS USED TO LIFT HEAVY BURDEN
Because of the mechanical advantage of the pulleys, relatively small power
is needed to lift this electromagnet, with tons of scrap iron clinging to it.
in passing around the wheel simply has its direction changed,
but there is no gain for the user of the machine either in
power or in distance.
If now the pulley is arranged as in Figure 142, it is no
longer a fixed pulley but is movable. It is evident in this
case that the weight is supported not by a single cord as in
the fixed pulley but by two cords, the part of the cord at-
468 TRANSFERRING AND TRANSFORMING ENERGY
tached to the beam
and the part of the
cord held by the
hand. The hand will
need to move twice
as far as the weight
is lifted.
A number of pul-
leys may be arranged
as in Figure 143 so
that the movable pul-
ley with the weight
attached is supported
by several cords. In
this case each sec-
tion of the cord sup-
porting the movable
pulley sustains its
proportion of the
weight, and the power
is as many times less
than the weight as
there are cords sup-
porting the movable
pulley. But the gain
in power means a loss in distance. The power will have to
travel as many times farther than the weight as there are
cords supporting the movable pulley. An arrangement like
this enables a small power slowly to lift a large weight.
The Inclined Plane. — When the ancient Egyptians built
the great pyramids, it was necessary for them to raise huge
INCLINED RAILWAY, SWITZERLAND
A gigantic inclined plane.
THE SCREW
469
USE OF THE WEDGE
blocks of stone to great heights. It would have been next
to impossible for them to do this simply by using brute
force . Some simple machine
was necessary. They prob-
ably used the same kind of
machine that is used to-day
in rolling a barrel into a
wagon or in grading wagon
roads- or railroads .over
mountain passes — an in-
clined plane. The more
gradual the inclination up
which the weight travels, the smaller the power required to
lift the weight. Again, what is gained in
A power is sacrificed in distance.
M
The Wedge. — The wedge consists
simply of two inclined planes placed back
to back. It is principally used in forcing
substances apart, as when wedges are
used to split wood and stones, or as
needles and pins are used in pushing
apart the fibers of cloth.
Axes and chisels and most
cutting tools except saws act on the principle
of the wedge.
FIGURE 145
The Screw. — The screw is simply an in-
clined plane ascending around a central axis.
(Figure 145.) The projection of the plane
from the axis is called the thread. The
plane moves the distance between the threads in making
one turn around the axis. A spiral staircase is a machine
FIGURE 146
470 TRANSFERRING AND TRANSFORMING ENERGY
of this kind. The screw is another example of a gain in
power with a corresponding loss in distance. The screw,
generally combined with the lever, is used in many ordinary
machines. The jackscrew (Figure 146), copy-press, and vise
are examples of combinations of these two simple machines.
Man's Most Important Energy Transformers. — Perhaps
the first of nature's forces that man made use of was the
wind. He hoisted a sail for the wind to strike upon and to
push him from place
to place. In about
the twelfth century
A.D. he discovered a
way of arranging
sails upon a wheel,
thus constructing a
windmill to help him
in his work. The
windmill is still used
in some places where
small power is needed, but the wind is no longer one of
man's main sources of energy.
Running water early impressed man with its power. He
finally harnessed this power for grinding his grain and for
doing other kinds of work by means of the water wheel.
Many shapes of wheels were tried before the mighty tur-
bine, such as is used at Niagara Falls, was invented. It is
probable that more power is now developed at these Falls
than was developed by all the earlier water wheels ever
used.
About the middle of the eighteenth century, a young
Scotchman, James Watt, invented a machine to utilize the
AN ANCIENT SAILBOAT
MAN'S IMPORTANT ENERGY TRANSFORMERS 471
power of expanding steam. He arranged a cylinder con-
taining a piston so that the steam would be admitted alter-
nately on one side and then on the other side of the piston.
As the expanding steam forces the piston in one direction,
the used steam in front of the advancing piston escapes
through an open valve. When the piston reaches the end
A SIMPLE WATER WHEEL USED FOR GRINDING CORN
of its stroke, the moving valves cut off the steam from the
one side and allow it to enter the other, thus driving the
piston back again and forcing the used steam out through
the escape. This continuous back and forth movement of
the piston can best be understood by an examination of the
accompanying diagram. (Figure 147.)
In recent years inventors have made it possible to apply
472 TRANSFERRING AND TRANSFORMING ENERGY
steam under great pressure to a wheel somewhat similar
in construction to a water turbine. Thus steam is made to
give a rotary motion, instead of the back and forth motion
of the ordinary steam engine, which must be converted into
rotary motion by the connecting rod and crank. These
steam turbines, as they are called, have been used to great
advantage in ocean ves-
sels where there is little
space available for ma-
chinery and where great
power and high speed
are desired.
In the gas engine the
energy of gas exploding
in a cylinder behind a
piston takes the place of
expanding steam in driv-
FIGUBE 147 ing the piston. Usually
two or more cylinders
are. used, and the explosions are so timed that a very steady
motion is given to the shaft. These engines were first
made about fifty years ago but have been greatly improved
recently, and are now used very extensively for automobiles,
motorboats, and airplanes.
The electric dynamo and the electric motor, which will
be discussed later, are other energy transformers which man
has developed and now constantly uses.
Power Available to Man. — When combustion is used as
a source of energy, man is drawing upon his bank account
with nature, and is using up the stored energy of the earth.
But in utilizing the energy of blowing wind and running
POWER AVAILABLE TO MAN
473
water, he is conserving energy that would otherwise be
wasted. " The mill can never grind again with water that
is past." There is, however, only so much water power in
the country and it is exceedingly important that these
ELECTRIC POWER PLANT AT NIAGARA
Conserving the energy of running water by transforming it into usable
electrical energy.
sources of power should remain in the possession of all the
people as represented by their Government and not be
monopolized for the commercial gain of a few people. In
recent years the United States Government has arranged to
retain control of power sites on public land, and to lease
rather than sell water power to individuals and corpora-
tions. Running water is a never-stopping, sun-power
engine, and its use should be the birthright of mankind.
474 TRANSFERRING AND TRANSFORMING ENERGY
SUMMARY
Man has invented many simple and complex machines
for transferring and transforming energy, and has thus
simplified the doing of work. Among the machines which
are used simply or in complex combinations are the lever,
the wheel and axle, the pulley, the inclined plane, the wedge,
and the screw. He has invented complex machines for
transforming the energy of running water, of burning fuel,
and expanding steam, and of exploding gases into forms of
energy that may be utilized at will. The natural sources of
power should never be monopolized for the commercial
gain of a few people; they should remain the birthright of
mankind.
QUESTIONS
Which of the six basic machines have you used? What ma-
chines have you seen that combined several of these basic ma-
chines? Explain how they were combined.
In what ways have you ever observed energy transformed by
machines so as to do useful work ?
What forces of Nature have you ever seen used for man's ad-
vantage ? How ?
CHAPTER XVI
TWO BELATED FORCES MAN HAS HARNESSED—
MAGNETISM AND ELECTRICITY
Magnetism. — So much were some of the ancients im-
pressed with the property of loadstones (page 37) for attract-
ing iron that one of them suggested building a great arch
of this material in a temple so that the iron statue of the
goddess would remain suspended in the air without resting
upon any support. There is an old legend that the iron
coffin of Mahomet rose and remained near the ceiling of the
mosque in which it was buried.
Experiment 147. — Touch with each end of a bar magnet small
pieces of paper, copper, zinc, iron, sawdust, and any other materials
that may be handy. Which substances are attracted by the
magnet ? Does it make any difference which end is
used ? Take a knife blade that has no such attrac-
tive power and rub it several times along one end
of the magnet ; then touch the different substances
with it. Has it acquired any new power?
Experiment 148. — Suspend a bar magnet hori-
zontally in a sling made from a bent piece of wire
(Figure 148). Bring one of the ends of another bar
magnet toward it. What is the effect ? Reverse the
, , , . , , . , , FIGURE 148
ends of the magnet ; is there any change in the posi-
tion of the suspended magnet? Bring a large, soft iron nail toward
either end of the suspended magnet. What is the effect? Reverse
the ends of the nail. (Be careful that the nail has not become
permanently affected by the magnet.) Is the effect the same as
when the ends of the magnet were reversed ?
475
476 MAGNETISM AND ELECTRICITY
Bring pieces of copper, zinc, and other substances toward the
magnet. Do these affect it? Notice that the ends of the bar
magnet are marked. What can you state about the attraction or
repulsion of similar ends of magnets? Of opposite ends? Does
it make any difference in its effect on the suspended magnet
toward which end the nail is brought ? What substances do you
find attracted by the magnet?
To the end of a small nail hanging by attraction to a magnet
bring another nail. How does the first nail act in respect to the
second ?
Experiment 149. — Suspend by a string a short bar magnet in a
sling, as in Experiment 148. Turn it around in several different
directions. After each change allow it to come to rest in whatever
position it will. Does it prefer any one position to all others?
It was early discovered that when pieces of steel were
rubbed on a loadstone they took on the properties of the
loadstone and became magnets. In the experiments with
magnets, it was found that like poles repelled and unlike
poles attracted, and that iron or steel in contact with a
magnet becomes magnetized. Iron and steel are practi-
cally the only substances attracted by a magnet, although
nickel and cobalt and a few other substances have a
little attraction. Thus steel and iron are always used
for magnets.
The Magnetic Field of Force. — Experiment 150. — Place a
plate of window glass about 8x10 inches above a bar magnet and
carefully sprinkle iron filings over it. Describe the behavior of the
filings. Sketch on a piece of paper their arrangement. Move a
small compass about above the glass plate and note the directions
the needle assumes. How do the actions of the needle and of the
filings compare? If feasible make a blue print of the filings.
Holding the small compass two or three inches above the magnet
move it parallel with the magnet from end to end. Gently tap the
compass occasionally so that the needle will move freely. How does
THE MAGNETIC FIELD OF FORCE
477
the needle act when it is over the ends of the magnet ? How does
the direction of the compass needle compare with the direction of
the bar magnet ?
In the experiment just performed we found that when
iron filings were sprinkled above the magnet they arranged
themselves in definite lines. The small compass needle also
arranged itself along these lines when brought under the
influence of the magnet. There
is, then, around a magnet a mag-
netic field of force which affects
magnets and magnetic substances
brought within it. It is found
that magnetic intensity, like the
intensity of sound and light, varies
inversely as the square of the
distance.
When the compass was placed
above the ends of the bar magnet
one of the ends of the needle was
pulled down toward the magnet,
or it might be said to dip toward
the magnet. When moved near
the middle of the magnet it as-
sumed a horizontal position, and
when it approached the opposite end of the magnet the
opposite end of the needle dipped. This same action is
found when a magnetic needle is carried from north to
south upon the earth. If a needle is carefully balanced and
then magnetized, it will be found no longer to assume a
horizontal position.
In the northern hemisphere the north end will dip and in
the southern hemisphere the south end. In the northern
FIGURE 149
478 MAGNETISM AND ELECTRICITY
hemisphere it is customary to make the south end of the
needle a little heavier so that it will stay in a horizontal
position. At the magnetic pole the needle would stand
vertical. If a needle is accurately balanced on a horizontal
axis and then magnetized, it will show the angle of dip in
any locality. Such a needle is called a dipping needle
(Figure 149).
The Mariner's Compass. — In the ordinary mariner's
compass (Figure 150) a magnetic needle is arranged so that
it will swing freely in a horizontal plane. A circular card is
divided into four equal parts, the divid-
ing lines of which are marked with the
cardinal points of the compass, the inter-
vening spaces being divided into eight
equal divisions. The card is attached to
the needle and inclosed in a box called
the binnacle. This box is arranged so
FIGURE 150 that ^ wn"l always remain horizontal.
A fixed line on the binnacle shows the
direction of the keel of the ship. The card being attached
to the needle always has its " north " pointing toward the
north. To determine the direction of the ship it is only
necessary to notice on the card in what direction the keel
line is pointing. The mariner of course must know the
declination at the place where he is and make the proper
corrections. The different governments furnish tables and
charts showing these corrections.
Theory of Magnetism. — Experiment 161.— Heat a No. 20
knitting needle red hot and plunge it quickly intp cold water. This
tempers the needle so that it will break readily. Magnetize the
needle as was done in Experiment 8. When it has become well
magnetized, break it in the middle. Test each half with a sus-
THEORY OF MAGNETISM 479
pended magnet, as was done in Experiment 148. Is each half a
full magnet or only half a magnet ? Break these halves again and
test. .What effect does breaking a magnet have upon the magnet?
In Experiment 151 it was found that if a magnet is broken
in two, each half is a perfect magnet. If these halves are
broken, each piece is a perfect magnet, and so on as long
as the division is kept up. It is also found that if a magnet
is heated or suddenly jarred or pounded it loses its magnet-
ism. If a magnet is filed into filings and these filings are
put into a glass tube, the tube will have no magnetic prop-
erties but will act to a magnet like an ordinary
iron bar.
If now the tube is held vertically and tapped
several times on a strong magnet, the tube will
be found to have acquired the properties of a
magnet. The tapping joggled the particles so
that they could arrange themselves under the
influence of the magnetic pole and when they be-
came so arranged a magnet was the result. If the
filings are now poured out of the tube and then
put back again, there will be no magnetization. I
It was the arrangement of the tiny magnetized particles
which must have caused the contents of the tube to be-
come magnetic. It would therefore seem probable that
magnetism must be a property of the exceedingly small
particles or molecules of which the iron or steel as well as
all other substances are supposed to be composed.
It is supposed that when a bar of steel becomes magnet-
ized the molecules arrange themselves in definite directions,
as do the filings in the tube. The molecules of magnetic
substances are supposed to be separate little magnets. In
the unmagnetized bar (Figure 151) their poles point in all
m
on KB
480 MAGNETISM AND ELECTRICITY
directions, dependent upon their mutual attraction ; and thus
they neutralize one another. When the bar becomes mag-
netized the molecules tend to arrange themselves so that
like poles lie in the same direction (Figure
152). When the magnet is heated or jarred the
molecules are moved out of this alignment and
the magnetism is weakened.
BBBG
BBBB
§BB-B
HBHG
HBHH
BHBB
BBiB
BBBB
BBBB
BBBB
BBBB
BBBB
BBBB
Electricity by Friction. — It was known by the
ancient Greeks that when certain substances,
one of which was amber, were rubbed, they
had the power of attracting light objects. This
property was afterward called electricity, from
FIGURE 152 the Greek word for amber.
Experiment 152. — Place some small pieces of paper or pith balls
on a table and after rubbing a glass rod with silk bring it near the
pieces. Do the same with a stick of sealing wax or a hard rubber
rod rubbed with flannel or a cat's skin. Note the action of the
pieces.
Experiment 163. — Rub a glass rod briskly with silk and place in
a wire sling such as was used in Experiment 148. Bring toward one
end of the glass rod another glass rod which has been rubbed with
silk. Do the rods attract or repel each other? Bring toward the
suspended rod a piece of sealing wax or a vulcanite rod which has
been rubbed with flannel or a cat's skin. Does this repel or at-
tract the glass rod?
Experiment 154. — Suspend a pith ball by a silk thread from the
ring of a ringstand. Rub a glass rod with a piece of silk and bring
it near the pith ball but do not allow the two to touch. Note the
action of the ball. Touch the pith ball with the rod. Does it
behave now as it did before? Rub a vulcanite rod with a piece of
flannel or cat's skin and bring it near a suspended pith ball. Does
the pith ball act as it did with the glass rod? Touch the pith ball
with the rod. How does it act? Bring a glass rod rubbed with
silk near a pith ball which has been in contact with a vulcanite rod
ELECTRICITY BY FRICTION
481
after it was rubbed with flannel or a cat's skin. Does the glass rod
repel or attract the ball?
Experiment 155. — Suspend a pith ball from the ring of a ring-
stand by a very fine piece of copper wire no larger than a thread.
Wrap the wire around the pith ball in several directions. Bring a
rubbed glass rod toward the pith ball. Does it act as it did when
suspended by silk? Allow the ball to touch the rod. Does the
ball now act as it did when suspended by silk? Try these same
experiments, using the vulcanite rod.
From the previous experiments it has been seen that
when glass is rubbed with silk, and vulcanite with flannel
FIGURE 153
or a cat's skin, they seem to have two different kinds of
electrical charges. The like kinds repel each other and the
opposite kinds attract. These two kinds are called posi-
tive and negative respectively.
Whether there are really two kinds of electricity has not
yet been fully determined, but electricity acts exactly as it
would if there were two kinds, and it has become customary
482 MAGNETISM AND ELECTRICITY
to speak as if there were. In Experiment 154 it was found
that pith balls suspended by a silk thread could be charged
with electricity if brought in contact with a charged body.
Experiment 155 showed that this was not possible when
they were suspended by a copper wire. The wire conducted
the electricity away. Substances like copper that conduct
electricity are called conductors, and those substances like
silk which will not conduct it, non-conductors.
A FLASH OF LIGHTNING
Experiment 156. — Having started the electrical action in a static
electrical machine (Figure 153), pull the knobs as far apart as the
spark will jump and notice the course taken by the spark. Does it
travel in a straight line? Hold a piece of cardboard between the
knobs so that its edge is just within the line joining them. What ef-
fect does the cardboard have upon the direction taken by the spark ?
Place the cardboard so that it entirely covers one of the knobs.
Is the spark able to pass through the card ? Attach a wire with a
sharp point to each of the knobs and extend it vertically two or
three inches above the knob. Start the machine. Do sparks
ELECTRICITY BY FRICTION
483
now jump across between the knobs? Why are houses provided
with lightning rods ?
About the middle of the eighteenth century, Benjamin
Franklin proved by his notable kite experiment that light-
ning was simply an electrical discharge between the clouds
and the earth, or be-
tween different clouds.
This discharge is simi-
lar to that which takes
place on an electrical
machine. The elec-
tricity in the clouds
attracts as close as
possible the opposite
kind of electricity on
the earth's surface and
tends to hold it ac-
cumulated on high
objects. If the attrac-
tion is sufficient, the
electricity discharges
between the cloud and
the object, and we say
the object was struck
by lightning.
If a sharp point,
such as a lightning
rod, is present on the object where the electricity tends
to accumulate, it allows the electricity to pass off gradually
before enough accumulates to cause damage. Lightning
rods, however, must be continuous conductors and properly
terminated in the ground.
A TREE COMPLETELY SHATTERED BY A
STROKE OF LIGHTNING
484 MAGNETISM AND ELECTRICITY
Serviceable Electrical Energy. — In Experiments 152 to
156, muscular energy was transformed into electrical energy.
In none of these cases, however, could the electrical energy
have been made of practical service to man. Methods
of producing electrical energy under different conditions had
to be found before this form of energy could be made to do
work. Within recent years man has done this and has thus
added electricity to the forms of energy he is able to con-
trol for his service.
Current Electricity. — In Experiment 155 it was found
that it was impossible to charge the pith ball when it was
suspended by the copper wire. The electricity passed off,
was conducted away, through the wire.
We had here a current of electricity
through the wire, but it was only for
an instant. At the opening of the
nineteenth century, an Italian by the
name of Volta discovered how a con-
tinuous electric current could be pro-
duced. If a strip of zinc and a strip of
copper or carbon are placed in dilute
sulphuric acid and connected with a wire (Figure 154), a
current of electricity will flow through the wire from the
copper or carbon to the zinc. The current is due to the
chemical action of the sulphuric acid on the zinc. Chemical
energy has been transformed into electrical energy.
An arrangement such as that shown in Figure 154 is
called a voltaic cell, after its discoverer. In a cell of this kind,
hydrogen bubbles formed by the action of the acid on the
zinc (see Experiment 56) soon collect on the copper strip,
and the current weakens and finally stops. The cell is
CURRENT ELECTRICITY 485
then said to be polarized. If cells are to be of practical
value, they must not quickly polarize ; that is, a way must
be found to get rid of the hydrogen bubbles. This is gen-
erally done by putting some substance into the cell that will
unite with the hydrogen and thus keep the copper strip free
of hydrogen bubbles. Many kinds of cells have been in-
vented which do not readily polarize.
The so-called dry cell (Figure 155) is most used at the
present time. It consists of a zinc can lined on the inside
with porous paper. In the center is a carbon rod. Packed
around the carbon and filling the can is usually
a moist mixture of sal ammoniac, manganese
dioxide, granulated carbon, plaster of Paris, and
generally small quantities of other materials. In
this cell the sal ammoniac acts upon the zinc
somewhat as the sulphuric acid did in the simple
.. . , FIGURE 155
cell first mentioned, and the manganese dioxide
unites chemically with the hydrogen bubbles and thus re-
moves them from the carbon rod. The plaster of Paris
keeps the cell in rigid shape and the granulated carbon
helps to keep the contents porous so that action may go on
freely within the cell.
In voltaic cells the copper or carbon strip is called the
positive electrode or pole, and the zinc is called the negative
electrode or pole.
Experiment 157. — Connect a positive and a negative pole of two
dry cells by a fairly heavy copper wire. Attach a similar piece of
wire to each of the other poles and connect these pieces by means
of a short, very fine, iron wire. (Figure 156.) The iron wire will
become red hot. Now remove the fine iron wire and connect the
loose ends of the copper wires to the socket of a small one or two
candle power electric light, such as is often used to illuminate the
486
MAGNETISM AND ELECTRICITY
speedometer of an automobile. (Figure 157.) The light is made
to glow.
In the preceding experiment we found that electrical
energy, in overcoming the resistance of the iron wire, was
changed into heat. When a
current of electricity passes
through any substance, the sub-
stance offers resistance to it.
The amount of resistance offered
by a conductor varies with the
kind of material, its length and
FIGURE 156 its thickness. Heating due to
resistance of an electric current is utilized in
the construction of electric flatirons, toasters,
stoves, and other devices. The electricity is
generally conducted to the utensils through a
wire made up of a number of small copper wires,
covered with non-conducting materials. The
resistance of the connecting cord is very low.
From this cord, the current
passes through coils in the
utensil that offer high re-
sistance. These are so ar-
ranged that the resulting
heat is delivered with al-
most no loss to the surface
which is to be heated. Al-
though it costs more to
produce the same amount
of heat by electricity than
it does by the other methods usually employed in the home,
yet for many purposes this heat can be applied with so
FIGURE 157
ELECTRIC IRON SHOWING HEATING
ELEMENT (E)
ELECTRIC LIGHTING
487
FIGURE 158
little loss that the use of electricity in some kinds of heating
becomes not only convenient but also really economical.
Heat generated by electricity is also
used for welding (Figure 158), and is
beginning to replace the forge. If metal
rods are pressed together end to end and
a sufficiently great current of electricity
is sent through them, the heat generated
at the point of contact, where the resist-
ance is greatest, will be sufficient to weld
them together. The rails of car tracks
are often welded together in this way.
Wherever electricity is received from wires in which the
strength of the current may vary considerably
from time to time, it is necessary to protect
electrical appliances from the heat caused by
too great a current. This is done by inserting
in the circuit a wire which will melt if too
much current passes through it, and will thus
instantly break the circuit. Such a safety de-
vice is called &fme. (Figure 159.)
Electric Lighting. — The little electric lamp
used in Experiment 157, like most other in-
candescent lamps, consists of a thread or fila-
ment of carbon inclosed in a glass bulb from
which the air has been exhausted. When this
lamp is connected with an electric current the
carbon is heated white hot by the resistance it
offers to the electric current. The carbon cannot burn be-
cause there is no air in the bulb, and it does not melt since
there is not sufficient heat to accomplish this. Incandescent
FIGURE 159
TUNGSTEN
LAMP
488
MAGNETISM AND ELECTRICITY
lamps are also made with metal filaments. Only two
metals, tantalum and tungsten, have been found that will
withstand the intense heat. Incandescent lamp filaments
made from these metals are necessarily much longer and
thinner than the carbon filaments, and are therefore more
easily broken. But their great advantage lies in the fact
that they use only about one third the amount of current
in giving the same light. A tungsten filament will with-
stand much heavier jarring when it is hot than when cold.
It sometimes happens that a lamp has imperfections that
render it dangerous to handle carelessly. If one touches
the metal part of such a lamp when it is in use, especially
with wet hands, one is likely to receive a severe shock. These
shocks have sometimes proved fatal. To avoid such possible
danger one should touch only the hard-rubber switch in
turning a light on or off. Especial care should be taken
when the hands are wet, because moisture is an excellent con-
ductor of an electrical current.
Electroplating. — Experiment 168. — Almost fill a dish with a
strong solution of copper sulphate (blue vitriol). Across the dish
^_ and a little distance apart,
place two parallel wooden
rods. Carefully clean with
fine sandpaper a strip of lead
and a strip of copper. Punch
a hole in an end of each strip
and attach to each strip two
or three feet of fairly heavy
copper wire . Pinch the wires
firmly on to the copper and lead at the points of connection. Sus-
pend a strip from each of the rods by winding the wire once around
the rod. Attach the wire from the copper to the positive pole of a
battery and the wire from the lead to the negative pole. A copper
plate will be deposited on the lead.
SIMPLE APPARATUS FOR ELECTROPLATING
ELECTROPLATING
489
In the preceding experiment the copper solution is de-
composed by the electric current as it passes through the
solution from the' copper strip to the lead strip, and the
copper freed from
the compound is de-
posited on the lead.
Just as fast as cop-
per from the solution
is deposited on the
lead strip, the same
amount of copper is
dissolved from the
copper strip; and so
the strength of the
solution is main-
tained as long as
there is any of the
copper strip remain-
ing. If it were de-
sired to plate with
silver, a silver strip
would have to be
substituted for the
copper strip and a
solution of a suitable
silver compound sub-
AN ELECTROTYPE
Photograph of the plate from which page 15
of this book is printed.
stituted for the
per sulphate solution.
Whatever the metal used for plating, corresponding solutions
would have to be used. All gold, silver, nickel, and other
plating is done in this way.
This book, like all books made in large numbers, has
490
MAGNETISM AND ELECTRICITY
been printed from electrotype plates. First a page was
set up in type, and then a careful impression of it was taken
in wax. Wax is not a good conductor of electricity and so
the face of the wax mold was evenly and thinly coated
with graphite in order to make it conduct electricity. The
graphite-covered mold was then attached to the nega-
tive electric pole, as was the lead in Experiment 158, and
immersed in the copper sulphate solution. To the positive
pole was attached a copper strip. As soon as a layer of
copper of the thickness of a calling-card had been deposited
on the mold, taking its shape, the newly formed copper
plate was separated from the wax impression and was
" backed up " with type metal to make it strong enough
to be used in the printing press.
Electromagnet. — Experiment 159. — Wind several feet of No.
20 insulated copper wire around the nail used in Experiment 148 as
you would wind thread on a spool. Attach the ends of this wire
to the poles of a dry cell.
Bring the nail thus arranged
toward a suspended magnet.
Reverse the ends of the nail.
Does the nail act as it did
before it was placed within
the coil of wire connected to
the battery ? Bring another
nail in contact with its ends.
What happens? What has
the nail as arranged be-
come ? Disconnect one of the wires from the battery and try
the test again. Does the nail act as it did when the battery
was connected?
We found that if a nail is placed in a coil of wire connected
with an electric battery (Figure 160) it becomes magnetic,
but only as long as the connection is maintained. Magnets
FIGURE 160
THE ELECTRIC BELL
491
of this kind are called electromagnets. If the nail had been
hard steel and the battery exceedingly strong, the steel would
have remained a magnet after being taken out of the coil.
Electromagnets have come to be of almost inestimable
use in modern life. The telegraph, the telephone, the mag-
netic crane, the electric motor, and almost innumerable
Courtesy of Illinois Central Railroad
ELECTROMAGNETIC CRANE
Loading steel rails on a freight car. The magnet is lifting seven rails, a
burden of about three and one half tons of steel.
other mechanical devices are dependent largely upon the
principle of electromagnetism for their usefulness.
The Electric Bell. — One of the simplest applications of
the electromagnet is the electric bell (Figure 161). When
the punch-button (P) is pushed down it closes the circuit
through the electromagnet (M). The hammer (H) is then
492
MAGNETISM AND ELECTRICITY
attracted toward the
magnet, and as it
moves toward it the
circuit is broken at
((7). Because of this
break the current no
longer flows through
(M) and the soft iron
cores instantly lose
their magnetic power.
Since the hammer is
no longer attracted
FIGURE 161. -ELECTRIC BELL to y^ ^ .g thrown
back by the spring (S) to its original position, thus closing
the circuit again and reestablishing magnetic attraction
at (M). This alternate
closing and breaking of
the circuit at (C) goes
on so rapidly that the
successive taps of the
clapper on the bell blur
into an almost continu-
ous sound. As soon as
the button (P) is re-
leased, the circuit is broken at that point and the bell
ceases ringing.
The Electric Telegraph. — In
1832 an American, Samuel F. B.
Morse, invented the commercial
telegraph. This was the first step
in the wonderful progress that has
FIGURE 163 been made during the last century
FIGURE 162
ELECTRICAL COMMUNICATION
493
SOUNDER
UNE BATTERY
FIGURE 164
in communicating rapidly between distant points. The
necessary instruments used in this form of communication
are a sounder (Figure 162) and a key (Figure 163). The
following experiment illustrates the ar-
rangement and operation of a simple
telegraph.
Electrical Communication.— Experiment
160. — Attach one end of a wire to a pole of a
dry cell and the other end to one of the bind-
ing posts of a telegraphic sounder. From the
other binding post of the sounder lead a wire
to a binding post of a telegraphic key. Con-
nect the free binding post of the key with the
free pole of the battery (Figure 164). When
the key is pushed down, the circuit is closed
and the sounder clicks. If a relay can be procured, remove the
sounder and connect two of the binding posts of the relay in the
same way that the sounder was connected.
Connect one of the free binding posts of the relay with a binding
post of the sounder and the other binding post with the pole of a
dry cell. Connect the other pole of the dry cell with the free
binding post of the sounder. When the key closes the circuit
through the relay,
the circuit through
the sounder and its
dry cell is closed
by the relay (Fig-
ure 165), and the
sounder clicks. This
is the usual arrange-
ment in a simple
telegraph office. The sounder in the first part of the above experi-
ment can be replaced by an electric bell (Figure 166) and the
key by a push button, thus showing the arrangement of the
ordinary doorbell.
FIGURE 165
494
MAGNETISM AND ELECTRICITY
The sounder is simply an electromagnet such as was made
in Experiment 159, arranged to attract a piece of soft iron
held at a short distance from it by a spring. When this
piece of iron is attracted
toward the magnet, it
strikes on another piece
of iron, making a click,
and so remains drawn
to the magnet as long
as the circuit is kept
closed. Thus long and
FIGURE 166
short clicks can be made.
Morse arranged a combination of these long and short
clicks to represent the alphabet. Thus he was able to
send words from one station to another.
WIRELESS TELEGRAPH STATION, Los ANGELES
Many improvements have been made since Morse first
sent a dispatch between Washington and Baltimore, but
his dot-and-dash alphabet and the electromagnet sounder
and the key are still in use. Since 1832, the land has been
THE TELEPHONE - . 495
strung with telegraph wires and the ocean girdled with
cables, and now an important event occurring in any part
of the earth is known almost instantly in all other parts.
The telephone, the wireless telegraph, and the wireless
telephone, all electrical devices, have added to the ease of
communication so that the whole earth is brought into such
close relation that every part knows what all the other parts
are doing.
The Greatest Electrical Discovery. — In 1831, Michael
Faraday, an English physicist, made a discovery the results
of which have almost revolu-
tionized civilized man's in-
dustrial life. He found that
when a magnet is quickly
thrust into a coil of wire a FlGURE 167
momentary electrical current is generated in the wire, and
when the magnet is removed a momentary current is gener-
ated in the opposite direction. The same effect is produced
if the strength of the magnet in the coil is quickly increased
or decreased, or if the coil is revolved between the poles
of a magnet. This discovery makes it possible to transform
mechanical energy into electrical energy and is responsible
for the invention of the dynamo, the motor, and many
other electrical devices.
The Telephone. — In 1875 Alexander Graham Bell first
communicated by telephone from Boston to Cambridge, a
distance of only a few miles. To-day man can talk across
the continent. Probably no device has resulted in greater
saving of time.
The simple telephone (Figure 168) consists of a hard-
rubber case in which is a permanent bar magnet surrounded
496
MAGNETISM AND ELECTRICITY
at the end by a coil of fine wire. In front of the magnet,
and almost touching it, is mounted a thin iron disk. Above
this a concave rubber cap with a hole in the center com-
pletes the case. The ends of the coil of wire are
connected with the wires from the coil of another
instrument of the same kind. One of the wires
from each coil may be connected with the ground.
The sound waves from the voice (or from any
other source) cause the disk to vibrate back and
forth in front of the magnet. These rapid vibra-
tions of the disk result in correspondingly rapid
changes in the strength of the magnet, and momentary
electrical currents are induced in the coil of wire. These
electrical impulses flow to the coil of wire in the other
instrument, where they cause correspondingly rapid changes
FIGURE 168
TELEPHONE STATION IN THE TRENCHES DURING THE WORLD WAR
THE DYNAMO
497
FIGURE 169
in the strength of the permanent bar magnet of that
instrument. The rapid variations of strength of this mag-
net cause the disk in front of it to vibrate in the
same way that the first disk vibrated and thus to throw
out sound waves similar to those of the
speaker's voice. The sound is in no sense
transmitted. The sound waves are trans-
formed into electrical impulses which are
transmitted to the other instrument, where
they are again transformed into sound waves.
For complicated modern telephone systems, a different
instrument is used for transmitting (Figure 169), but the
principle involved is the same. The instrument described
is still used for re-
ceiving, except that
the bar magnet has
been replaced by a
U-shaped magnet.
The Dynamo. -
The dynamo is a pro-
foundly important
result of Faraday's
discovery. In the
dynamo, coils of wire
are revolved between
strong magnetic
poles, and the cur-
rents of electricity
which are generated are collected and delivered to the line
wire to be used wherever desired. In commercial machines,
there are usually several pairs of electromagnets and many
DYNAMO
498 MAGNETISM AND ELECTRICITY
coils of wire. The coils are revolved by means of water
power, steam power, or any other available power.
The electricity that is generated by the dynamo is easily
transferred by wires to a long distance from the point where
it is generated. Los Angeles uses electrical power which is
generated in the mountains over 300 miles away. The
Courtesy of Chicago, Milwaukee and St. Paul Railway
POWER PLANT AND DAM OF THE MONTANA POWER COMPANY
This plant at Great Falls, Montana, transforms energy of running water into
electrical energy by which trains are operated over 641 miles of track.
energy of the water falling at Niagara is transformed . into
electrical energy which is utilized for transportation and
for industrial purposes at a distance of nearly 200 miles.
The location of the power no longer determines the site of a
'factory. The factory may be located at the most con-
venient place possible and be run by power which is trans-
mitted from almost inaccessible mountain retreats.
THE ELECTRIC MOTOR
499
The Electric Motor. — In the dynamo the coils of wire
are revolved in a magnetic field by some mechanical power,
and electricity is generated in the coils. In the motor the
process is reversed ; electricity is passed through the coils of
the motor. This causes them to revolve in a magnetic
field and to produce mechanical power. In appearance and
Courtesy of Chicago, Milwaukee and St. Paul Railway
ELECTRIC LOCOMOTIVE
One of the locomotives which obtains its power from the plant pictured
opposite. The most powerful electric locomotive in the world.
make-up the two machines are similar, but their work is
different. The dynamo generates an electrical current ; the
motor uses an electrical current.
In the running of the ordinary street car, the motor and
the dynamo supplement each other. At the power house
are dynamos run by any convenient kind of mechanical
power. The electricity that is generated is collected and
500 MAGNETISM AND ELECTRICITY .
transmitted by wires and trolley through the controller
to the motor under the street car. The motorman, by
means of the controller, is able to turn the current into the
motor or to shut it off. When the current is turned on,
the motor revolves; by gearings the motion is imparted to
the wheels and the car moves. Thus the electricity gen-
erated by the dynamos in power houses, wherever they
may be, not only lights our homes and streets, but also en-
ables the little motors in our homes, the powerful motors
on street cars, and the giant motors of our factories to do
all kinds of work for us.
Theory of Electricity. — A great deal is known about how
electricity acts and what it does, but as yet little is known
about what it really is. Recent experiments indicate that
the atoms of matter (page 51) contain electricity, and
that the negative electricity in them exists in the form
of exceedingly minute particles called electrons. There
are hundreds of these electrons in each atom, and they are
held there probably by the attraction of a positive charge
of electricity at the center of the atom. If the positive and
negative charges in the atoms of a body are equal, the body
is unelectrified.
If, however, the electrons are in any way joggled off and
accumulated, a negative charge of electricity develops
where this accumulation takes place. As the electrons are
all negative, they repel one another and tend to move away
from the point where they have accumulated to places
where the accumulation is not so great. This is what hap-
pened in Experiment 156, when the electrical machine was
used. An electric current is supposed to be a stream of
these electrons.
QUESTIONS 501
SUMMARY
Certain substances may be made to take on the properties
of loadstone and to become magnets. A magnet has a
positive and a negative pole. The dipping needle and the
mariner's compass are applications of magnetic properties.
There are two kinds of electrical charges, positive and
negative. Electricity may be generated by friction, but to
be of practical service it must flow continuously as a current.
Lightning is an electrical discharge. Currents of electricity
may be generated by means of voltaic cells, and these cur-
rents may be conducted by wires. There are many practi-
cal applications of electricity, as in electroplating, incandes-
cent lamps, welding, flatirons, electric bells, the electric
telephone, and the electric telegraph.
Michael Faraday made the greatest electrical discovery
when he found that a magnet if thrust quickly into a coil
of wire generates a momentary current in one direction,
and if withdrawn generates a momentary current in* the
opposite direction. This discovery made possible the in-
vention of the electric dynamo and the electric motor.
Recent experiments indicate that atoms of matter con-
tain electricity, and that the negative electricity in them
exists in the form of exceedingly minute particles called elec-
trons. A current of electricity is supposed to be a stream of
these electrons.
QUESTIONS
Where have you ever seen magnetism employed to man's ad-
vantage ?
What is the relation between lightning and electricity ?
With what simple electrical devices are you familiar ?
In how many different ways do you know electricity to have
been applied for your benefit ?
Describe four electrical machines or appliances which you con-
sider of particular value.
CHAPTER XVII
WITHIN THE EAKTH'S OKUST
Beneath the Earth's Surface. — Many excavations and
borings have been made deep into the earth's crust and it
has been found that the temperature increases with the
depth. The rate of increase is not the same in different
places, nor is the increase always uniform in the same
SAN MIGUEL HARBOR IN THE AZORES
Notice the volcanic cone in the distance.
place. The average of a number of deep excavations in
different parts of the earth gives a rise of 1° F. for each 70
or 80 feet of descent.
The greater the pressure to which rocks are subjected the
more difficult it is to melt them. If it were not for this, the
solid part of the earth could not be more than 40 or 50 miles
502
BENEATH THE EARTH'S SURFACE 503
thick, as the interior heat would melt rocks under ordinary
pressure. But the earth is too rigid for its interior to be
otherwise than solid. So great is the pressure to which it
is subjected that probably none of the material deep down
in the interior of the earth is in a molten condition.
If the pressure near the surface should be decreased,
or if the normal amount of heat at any place should be
increased, the material might become fused, and under
AN HAWAIIAN CRATER
certain conditions might find its way to the surface. We
know that heated material from below does rise toward the
surface and intrude itself into the surface rocks and in
some places pour forth over the surface.
What causes the uprising and outpouring of this molten
material from below the surface of the earth, and how and
why it 'reaches the surface are questions which as yet are
unanswerable. But as soon as this igneous material comes
within the range of observation, its properties and actions
504 WITHIN THE EARTH'S CRUST
can readily be studied. The following descriptions of some
well-known typical volcanoes show some of the results of
subsurface activity.
Monte Nuovo. — In 1538, on the shore of the Bay of
Naples near Baise, that once famous resort of the Roman
nobles, after a period of severe earthquake shocks there
suddenly occurred a tremendous eruption. From within
the earth emerged a mass of molten material blown into
fragments by the explosion of the included gases. Within
a few days there was formed Monte Nuovo, a hill 440 feet
high and half a mile in diameter, having in the top a cup-
shaped depression or crater over 400 feet deep.
So great was the explosive force of this eruption that
none of the ejected material was poured out in the form of a
liquid. The whole hill is made up of dust, small stones, and
porous blocks of rock which resemble the slag of a blast
furnace. The small fragments in such eruptions are called
ash or cinders. In a week the eruption was over, and noth-
ing of the kind has since occurred in the region.
When visited by the writer a few years ago, the bottom
of the crater was a level field planted to corn. The whole
process of formation of this volcanic cone was observed and
recorded by residents of the region. Other similar eruptions
have been observed, but perhaps this is the best known.
Vesuvius. — When the Roman nobles were building
their magnificent villas and baths along the shore of the
Bay of Naples, the scenic beauty of the region was greatly
increased by a mountain in the shape of a truncated cone,
which rose from the plain a few miles back from the shore.
Its sides, nearly to the summit, were covered with beautiful
fields.
VESUVIUS
505
In the top of the mountain was a deep depression some
three miles in diameter, partly filled with water and almost
entirely surrounded by precipitous rock cliffs. There
were no signs of internal disturbance. Around the moun-
tain were scattered prosperous cities, the soil was fertile,
the vegetation luxuriant. To this natural fortress Spar-
tacus, the gladiator, retreated when he first began to defy
the power of Rome.
In 63 A.D. the region about the mountain was shaken
by a severe earthquake which did much damage. This
VESUVIUS AND NAPLES
was followed by other earthquakes during a period of six-
teen years. In August, 79 A.D:, the whole region was fright-
fully shaken, and the previously quiet mountain began to
belch forth volcanic dust, cinders, and stones, so that for
miles around the sun was obscured, and a pall of utter
darkness shrouded the country, lighted at intervals by
terrific flashes of lightning.
506 WITHIN THE EARTH'S CRUST
A large part of the ancient crater, now known as Monte
Somma, was blown away, and the villas and towns near
the mountain were covered with the ash and cinders ejected.
So deep were many of these buried that their sites were
utterly forgotten. Pompeii and Herculaneum, after lying
buried and almost forgotten for hundreds of years, have
been recently partially uncovered.
These fossil cities show the people of to-day how the
ancient Romans lived and built. The topography of the
country and the coast line were greatly changed by this erup-
tion. Pompeii formerly was a seacoast city at the mouth
of a river. It is now a mile or more from the sea and at a
considerable distance from the river.
From the date of its first historic eruption until the present
time Vesuvius has had active periods and periods when
quiet or dormant. Sometimes the activity is mild, and at
other times tremendously violent. At times the material
ejected is fragmental and at other times streams of molten
lava pour down its sides. Its ever changing cone, unlike
that of Monte Nuovo, is composed partly of ash and partly
of consolidated lavas. Even as late as 1907 a tremendous
outpouring of ash took place which devastated a con-
siderable area.
Mount Pelee. — At the north end of the island of Mar-
tinique in the West Indies rose a conical-shaped mountain.
In a hollow bowl-like depression at the top lay a beautiful
little lake some 450 feet in circumference. The mountain
and lake were pleasure resorts for the people of the city of
St. Pierre. According to legend this mountain had been
violently eruptive, but in historic time there had been no
indication of this except one night in 1851 when the volcano
MOUNT PELEE
507
had grumbled and a slight fall of volcanic ash was found in
the morning over some of the surrounding region.
On April 25, 1902, people began to see smoke rising
from the vicinity of the mountain and from this time on
MOUNT PELEE AND THE RUINS OF ST. PIERRE
till the final catastrophe smoke and steam came out in
small quantities. By May 6 the volcano was in full erup-
tion. On the morning of May 6 the cable operator at St.
508
WITHIN THE EARTH'S CRUST
Pierre cabled, "Red-hot stones are falling here, don't
know how long I can hold out." This was the last dis-
patch sent over the cable.
About 8 o'clock on the morning of the 8th a great cloud
of incandescent ash and steam erupted, swept rapidly down
the mountain toward St. Pierre, and in less than three
LAVA FLOW IN THE HAWAIIAN ISLANDS
Liquid lava flowing over a cliff.
minutes killed 30,000 people, set the city on fire, and de-
stroyed 17 ships at anchor in the harbor. Thus within
two weeks from the time of the first warning a rich and
densely populated region was made a desolate, lifeless, fire-
swept desert.
Distribution of Volcanoes. — The number of active vol-
canoes on the earth is about three hundred. Most of them
are situated on the borders of the continents, on islands near
DISTRIBUTION OF VOLCANOES
509
the continents, or else they form islands in the deep sea.
Soundings show that there are many peaks in the sea which
have not reached the surface ; these are probably volcanic.
Few volcanoes are far from the sea, although there is an
MOUNT LASSEN IN ERUPTION
This volcano, after being dormant for centuries, suddenly renewed its
activity in 1914.
active crater in Africa several hundred miles from the
Indian Ocean.
About 800 miles west of Portugal rises from the depths of
the Atlantic a group of nine islands, the Azores. .They
510
WITHIN THE EARTH'S CRUST
have an area of about 1000 square miles, and the soil is
very fertile. The islands are mountainous, one of the
mountains rising to between 7000 and 8000 feet above the
sea. Their formation is due entirely to volcanic forces.
Islands of this kind and coral islands are the only projec-
tions rising to the surface from the deep ocean floor.
In the Cordilleran region of the United States, west of
the meridian of Denver, there are a score or more of lofty
THE CITY OF ST. HELENA
peaks which show conclusive evidence of volcanic origin.
Until the summer of 1914 when Mt. Lassen suddenly began
to erupt, none of these had been active since white men
became familiar with the region. In the Aleutian Islands
are numerous volcanoes which are still active, and in Hawaii
are some of the greatest volcanoes on the earth.
Extinct cones are sometimes found far in the interior of
continents, as the Spanish Peaks of Colorado, which are
GEYSERS
511
more than 800 miles from the present coast. Many of
the once active deep-sea cones have now become extinct,
and their gently sloping shores have been cut back into
cliffs which rise abruptly from the sea. One of these, St.
Helena, rising from
the depths of the
Atlantic Ocean, and
bounded by precipi-
tous cliffs, is noted
as being the place of
exile of the Emperor
Napoleon I of France.
Geysers. — In the
north island of New
Zealand, in Yellow-
stone National Park,
and in Iceland, re-
markable spouting
springs called geysers
are found. These
places have had re-
cent volcanic ac-
tivity. The eruption
of a large geyser is
a most picturesque
and startling phe-
nomenon. Almost
without warning there is thrown into the air a column
of hot water from which the steam escapes in rolling clouds.
It rises in some cases to a height of a hundred feet or more
and is maintained at nearly this height by the ceaseless
GIANT GEYSER IN ERUPTION
512
WITHIN THE EARTH'S CRUST
outrushing of the water for a time varying from a few minutes
to between one and two hours. Then it gradually quiets
down and dies away into a bubbling spring of hot water.
The time at which most geysers will erupt is uncertain,
but there is one, Old Faithful, in Yellowstone Park, which
is almost as regular as a clock, the time between its erup-
tions being a little over an hour. This geyser plays to the
height of about 150 feet and maintains the column of water
for about four minutes. The Giant Geyser of the same re-
gion throws a large column of water to a height of 250 feet.
It plays from one to two hours.
Experiment 161. — Fit a 250 cc. glass flask with a two-hole rubber
stopper. Through one hole extend a glass tube (a) almost to the
bottom of the flask and through the
other hole a tube (6), 5 or 6 cm. longer
than the height of the flask, to within
about 1 or 2 cm. of the bottom of
the flask. This last tube should be
slightly drawn out at the end and
bent at the top so that it slants away
from the flask. Arrange the flask on
a ring stand so that it can be heated
by a Bunsen burner. Connect to the
tube (a) a rubber tube long enough
to reach into a water reservoir placed higher than the top of the
flask and to one side. Fill the reservoir with water. (Figure 170.)
Through the tube (6) " suck " the air out of the flask until the
water from the reservoir begins to run into the flask. A siphon will
be formed which, when there is no internal pressure, will keep the
water in the flask slightly above the bottom of the tube (6) . Now
heat the flask. When steam begins to form, hot water will be
thrown out of the tube (6) until its lower end becomes uncovered
and the pressure of the steam relieved. Water from the reservoir
will then run in again, slightly covering the end of the tube. As
soon as more steam is formed, hot water will be ejected as before.
FIGURE 170
EARTHQUAKES
513
Thus a spray of hot water is intermittently ejected from the flask
as long as heating continues. We have here an action which re-
sembles that of a geyser.
The outpouring hot water brings up with it dissolved
rock and as the spray falls back and cools, this is deposited,
forming craters of singular shape and grotesque beauty.
On looking into these craters a smoothly lined, irregular,
crooked, tubelike open-
ing is seen to extend
down into the ground.
It is through this that
the water finds its way
to the surface. How long
these tubes are nobody
knows, but they must
reach to a point where
the heat is sufficient to
raise water to its boiling
point. This heat is prob-
ably due to hot sheets of
lava.
When the water in the
tube is heated enough to
make it boil under the pressure to which it is subjected,
steam forms and some of the water is pushed out over the
surface. This escape of water relieves some of the pressure,
and more of the water far down in the tube expands into
steam, thus throwing more water out. Huge indeed must
be the reservoir to which the tube in a geyser like the Giant
leads, to be able to pour out such a vast quantity of water.
Earthquakes. — In mountain regions which are young
or still growing, earthquakes are not uncommon. These
FAULT LINE OF AN EARTHQUAKE
514
WITHIN THE EARTH'S CRUST
are due to breaks or slips of a few inches or a few feet in the
rock structure. From the place at which the break or slip
takes place the motion is transmitted through the rock mass
to the surface, where it causes sudden and often tremendous
shocks. These slippings may occur occasionally for ages
along the same fault line.
Sometimes they are in-
tense enough to cause
great damage; at other
times only a slight tremor
is felt.
The rapidity of the
transmission of the shock
differs with the kind of
material through which
it is transmitted, varying
from a few hundred feet
to several thousand feet
per second. The nearer
a place is to the break
or slip the greater is the
intensity of the shock.
Sometimes the crack or
fault along which the movement occurs reaches to the
surface and makes the displacement apparent.
If an earthquake originates under the sea, a great wave may
be developed which rushes inland from the coast, causing
great destruction. One of the most fearful of these waves
occurred at Lisbon, Portugal, in 1755, sweeping away thou-
sands of people who had rushed into an open part of the city
to get away from the falling buildings caused by the earth-
quake shock.
FENCE BROKEN BY THE SLIPPING OF THE
EARTH ALONG A FAULT LINE
MINING IN MOUNTAIN REGIONS 515
Sometimes earthquakes are followed by terrible fires
which cannot be extinguished on account of the disarrange-
ment of the water supply. This was the case in the San
Francisco earthquake. With the care taken in rebuilding
SAN FRANCISCO FIRE
The direct damage to property and loss of life by earthquake in 1906 was
insignificant. The disarrangement of the water supply made possible
one of the greatest conflagrations in history. Extraordinary precautions
were taken in relaying the water mains of the risen city.
that city and in laying its water-mains, it is unlikely that
any such disaster could ever follow another earthquake of
the same sort.
Mining in Mountain Regions. — When rocks are folded
and crushed, in forming mountains, heat is generated, and
heated water under pressure acts upon the components of
the rocks and dissolves some of their minerals, which ac-
cumulate in cracks and crevices called veins. When the over-
lying beds have been worn away, these mineral veins, formed
516 WITHIN THE EARTH'S CRUST
deep below the surface, are exposed and can be mined.
Mountains are therefore the great regions for the mining of
metals.
In this country mining is a most important industry in
the Sierra Nevada Mountains and in the Appalachian re-
gion. In one are found great quantities of copper, silver,
PLACER MINING IN THE SIERRAS
The sand is washed from the gold by huge streams of water.
and gold, and in the other iron and coal. In the old Lauren-
tian Mountain region, near the Great Lakes, much copper
is found. The Alps and the Pyrenees are among those
mountains that have few minerals.
The Story of Coal. — We have learned that warm, moist
air is necessary for the activities of the bacteria of decay.
Where there is too much water and not enough air the con-
ditions are not favorable for complete decay. When plants
THE STORY OF COAL
517
die and fall into water, they undergo changes but not the
changes that occur in air. Most of the carbon, which in
the air would be oxidized into carbon dioxide, is preserved
under water.
Where vegetation grows, dies, and falls into water year
after year for great lengths of time, the plant remains will
DIGGING PEAT IN IRELAND
gradually accumulate until they fill the swamps in which
they have grown or the lakes which they have bordered.
This explains the formation of great peatbogs in Ireland
and in other parts of the world. Some of the peatbogs
of Ireland are more than forty feet deep, and the spongy
peat when cut and dried furnishes the most widely used
518
WITHIN THE EARTH'S CRUST
fuel of that country. That such bogs are filled lakes or
swamps and that it has taken thousands of years for the
peat to accumulate, is shown by the fact that hollowed
Courtesy of Taylor Coal Co.
COAL MINING IN SOUTHERN ILLINOIS
Using a pneumatic drill, preparatory to blasting. Notice the horizontal
layers in which the coal lies.
logs used as canoes by prehistoric men are sometimes found
buried in the peat at a depth of thirty feet or more.
If these peat accumulations should at some time be grad-
ually submerged and covered with sand and silt, the ever-
increasing pressure of the water and of the layers of sediment
would gradually compress the spongy mass of vegetation
THE STORY OF COAL 519
into compact layers. In the course of ages these layers
would harden and change into seams of bituminous (soft)
coal. The overlying layers of sand and mud would change
into layers of sedimentary rock.
This process has been repeated many times in the history
of the earth. In fact there are some sections where it has
happened more than once over the same area, and has re-
sulted in the formation of several seams of coal, one above
the other, with layers of sedimentary rock between. If in
after ages such seams of coal were heated by the folding of
the earth's crust, or by some other means, the bituminous
coal was changed into anthracite (hard) coal.
Sometimes miners find the roots of ancient trees, now
changed into coal, projecting from the bottom of a seam of
coal into the underlying rock layers that formed the soil
in which this ancient vegetation grew. Sometimes the
impressions of leaves and plant stems are found in the
underlying or the overlying rock layers and even in the coal
itself.
How dependent the greater part of the civilized world
is upon nature's supply of coal, for comfort and for com-
merce, was shown during the coal famine of the winter of
1917-1918 in our Eastern and Middle states. Coal is a
plentiful commodity in normal times, and in many sections
is very cheap ; but considering that nature has required
ages to form and preserve it, and that what now seems an
unlimited supply must some day be exhausted, the prodigal
waste of coal of which recent generations have been guilty
is a serious matter.
Petroleum is probably the result of the decomposition of
animal and plant remains which have been subjected for
ages to heat and enormous pressure. By distilling petroleum,
520 WITHIN THE EARTH'S CRUST
or crude oil as it is generally called, many different products
are obtained, among which are gasoline, kerosene, benzine,
paraffin, and various lubricating oils.
The crude oil itself is burned in many sections to produce
heat and power. For many purposes it is better than coal,
OIL WELLS
Tapping the rock layers containing petroleum.
since the same amount of fuel can be carried in less space.
The supply of oil seems to be even more limited than that
of coal, but it has been wasted at times fully as recklessly.
In the interest of future generations, both coal and oil
should be more carefully conserved.
SUMMARY
Many excavations and borings into the earth's crust have
shown that temperature increases with depth. If it were
not for the tremendous pressure of outside layers of matter,
the heat at the interior of the earth would probably cause
the matter there to be in a molten condition. If from
QUESTIONS 521
solid matter heated to such a temperature, pressure should
be withdrawn, or if the normal heat should be increased,
the heated matter might become molten and find its way
to the surface. What causes uprising and outpouring of
molten material is a question that is at present unanswer-
able. We know only that this does occur, and has resulted
in such volcanoes as Monte Nuovo, Mount Pelee, Vesuvius,
and other less famous volcanoes all over the world. Geysers
are spouting hot springs that are found in regions of recent
volcanic activity. Earthquakes are shocks communicated
to the surface of the earth from breaks or slips in rock
structure of the earth's crust.
Mountains are the great regions for the mining of metals.
It is supposed that the heat generated by the folding and
crushing of the earth's crust in these regions has brought
about the accumulation of the metal in cracks or crevices
called veins. Bituminous coal is a sedimentary rock of
vegetable origin, which has been deposited under such
conditions that the carbon instead of being oxidized was
preserved.
QUESTIONS
What is the probable condition of the earth's interior?
Describe the eruption and present condition of Monte Nouvo.
What has been the history of Vesuvius?
What is Mount Pelee' s story?
Describe a geyser.
What causes earthquakes?
How has coal been formed?
CHAPTER XVIII
LIPE AS RELATED TO PHYSICAL CONDITIONS
Ancient Life History. — As the rock layers of the earth
are explored, fossils of different kinds of plants and animals
are discovered. The fossils of the more recent rock layers
PETRIFIED TREES
Found near Holbrook, Arizona.
correspond very closely to the plants and animals that are
found upon the earth to-day, but the older the layers, the
less they correspond. There seems to have been a gradual
development in life forms through the past ages, a frag-
522
ANCIENT LIFE HISTORY
523
mentary record of which is engraved upon certain of the
sedimentary rocks. Rocks which were formed under dif-
ferent conditions contain different species of life-forms,
showing that throughout all time the geographic condition
has had a marked influence upon plants and animals.
The rocks and fossils also show that the geographical
conditions of certain areas have varied greatly. Some
SKELETON OF AN ANCIENT AMERICAN ELEPHANT
Found near Los Angeles, California.
regions have been below and above the sea several times.
Regions now cold have been warm, and those now dry have
been wet, and vice versa. Thus the life in certain areas has
suffered great changes by the geographical accidents to
which the region has been subjected. The petrified forests
near Holbrook, Arizona, show some of the most remarkable
tree fossils ever found and indicate that the region has been
subjected to remarkable geographical changes.
524 LIFE AS RELATED TO PHYSICAL CONDITIONS
Distribution of Life. — Plants and animals are found
wherever the conditions are suitable for their existence.
The surface of the earth is a universal battlefield of plants and
animals struggling to
exist and to in-
crease. They extend
themselves wherever
attainable space is
opened. But barriers
may oppose their
spread and geo-
graphical accidents
may drive them from
areas which they had
heretofore held. The
retreat of the sea may
cause a change in the
position of shore life.
In the water a land
barrier or an expanse
of deep water may
prevent the spread
of shore forms. On
the land a mountain
uplift, a desert area,
or a water barrier may limit the space occupied by animal
and vegetable species.
• Certain plants and animals are much more widely dis-
tributed than others. Plants like the dandelion and thistle,
whose seeds are easily blown about by the wind, spread
rapidly, while trees like the oak and chestnut spread slowly.
As plants have not the power to move about, they cannot
GILA MONSTERS
These are very poisonous reptiles of the
southwestern American desert.
EFFECT OF THE GLACIAL PERIOD
525
distribute themselves as easily as animals. Certain birds
which are strong of flight are found widely distributed over
regions separated by barriers impassable to other animals.
Some of the present barriers to life distribution have come
into existence in comparatively recent geological time.
There is good reason to believe that the British Isles and
Europe were formerly connected, and that in very ancient
times Australia was joined to
Asia. It is also believed that
for long ages North and South
America were separated by a
water barrier and that even after
they were once connected, the
Isthmus of Panama was again
submerged.
These are but a few illustra-
tions of the changes in the earth's
surface which have affected the
distribution of animals and
plants. Climatic changes like
that which brought about the
great ice advance of the Glacial
Period have affected in a marked
degree the distribution of life.
It is thus found that when a study is made of the present
distribution of life, careful attention must be given to the
present and past geographical conditions of the region.
Effect of the Glacial Period upon Plants and Animals. —
All plants and animals were forced either to migrate be-
fore the slowly advancing ice or to suffer extermination.
Individual plants, of course, could not move, but as the ice
CANA-DA THISTLE
One of the most widely dis-
tributed of plants.
526 LIFE AS RELATED TO PHYSICAL CONDITIONS
spread toward the south with extreme slowness and with
many halts, the plants of colder latitudes found conditions
suitable for their growth ever opening toward the south.
They were thus induced to spread in that direction, so
that at the time of the greatest extension of the ice the
plants suitable to a cold climate had penetrated far to the
south of their former habitat.
As the ice receded, these cold-loving plants were forced
to follow its retreat or to climb the mountains in order to
obtain the climate they needed. They did both, so that
in areas once covered by the ice, plants similar to those of
far northern regions are found on the tops of the mountains
in middle latitudes. What was true of the plants was true
also of the animals.
Waterfalls Due to Glaciation. — As the ice spread over the
country it filled the river valleys in many places with debris.
When the ice melted away, some rivers could no longer
find their old courses and were forced to seek new ones.
In its new course a stream might fall over a cliff.
The Merrimac furnishes a fine example of water power
due to glaciation. The great manufacturing cities of Lowell,
Lawrence, and Haverhill would not exist had not the river
been displaced from its previous channel by the glacial ice,
and in developing its new valley come upon ledges. The
Niagara is another notable example of vast water power
due to the displacement of drainage by the ice. It is probable
that in pre-glacial time there was a river which carried off
the drainage of the area now drained by the Niagara, but
it did not flow where the Niagara now flows.
Thus we see that the hum of the spindle and the lathe
are often but the modulated whispers of those ancient forces
WATERFALLS DUE TO GLACIATION 527
YOSEMITE FALLS
A wonderfully beautiful waterfall due to glacial action.
528 LIFE AS RELATED TO PHYSICAL CONDITIONS
which thousands of years ago sorted the rock materials and
built the vast continental ice palaces of the Glacial Period.
Adaptability of Life. — There is hardly a place on the
earth's surface not adapted to some form of life. Even upon
the ice-bound interior of Greenland a microscopical plant
and a tiny worm
have found a home.
The dry desert re-
gions have a few
plants with small
leaves or, like the
cactus, with no true
leaves. Lack of
leaves prevents the
evaporation of the
water from plants
and so protects them
from drought.
Another example
of adaptability is the
fact that the small
animals of the desert
are generally of a
sandy color, which
makes them hardly
distinguishable from
their desert sur-
roundings. The large
ones are swift, strong
runners, like the an-
telope and ostrich,
CACTI
These are adapted to desert life because
they have no leaves from which water can
evaporate.
ADAPTABILITY OF LIFE
529
RATTLESNAKE COILED READY TO
The color of these reptiles makes them
hardly distinguishable from the sur-
rounding desert.
or, like the camel, are
able to travel for long
distances without water.
In the colder regions
the plants have the power
of rapid growth and
germination during the
short season when the
snow has melted away.
Then, during the long
winter, they lie dormant but unharmed under the snow and
ice. The animals are either able, like the reindeer, to live
upon the dry mosses, lichen, and stunted bushes, or else
upon other animals.
Their color, like that
of the polar bear,
often blends with
their surroundings.
Some animals have
a wide range of
adaptability, like the
tiger, which is found
from the equator to
Siberia. But usually
the range of an ani-
mal species is much
more restricted, since
it is seldom able to
adapt itself to widely
differing conditions. The surrounding region, the eleva-
tion, the temperature, the amount of moisture, the soil,
the kinds of winds and their force, all have a marked
A HERD OF REINDEER
This animal is of invaluable service to man
in polar regions.
530 LIFE AS RELATED TO PHYSICAL CONDITIONS
effect upon the fauna (animals) and flora (plants) of a
country.
The species that thrive in a region must have adapted
themselves to the existing conditions, yet other animals
and plants may be as well adapted for certain regions as
those now inhabiting them. Striking examples of this
CALIFORNIA RABBIT DRIVE
In some localities rabbits become such a pest that the inhabitants turn
out in a body, drive them into inclosures, and kill them.
are the English sparrow and the gypsy moth, which have
spread with such tremendous rapidity since their introduc-
tion into this country. The rabbit in Australia and southern
California is another striking example. The adaptability
of plants to a new region is also illustrated by the Russian
thistle which was introduced into this country in 1873 and
which has now become a national pest.
LIFE OF THE SEA 531
Life of the Sea. — The plants living in the sea are nearly
all of a low order. The mangrove trees which border some
tropical shores represent their highest type. The most
abundant of sea plants, the seaweeds, have no flower or
DIFFERENT KINDS OF SEAWEED
seed or true root, although most of them have an anchoring
device by which they are attached to the bottom. Their
food is absorbed from the surrounding water. They have
developed little supporting tissue, but instead have bladder-
like air cavities or floats, which enable them to maintain
532 LIFE AS RELATED TO PHYSICAL CONDITIONS
an upright position or to float freely in the water. Usually
they abound near the shore where the water is shallow.
The vast surface of the open sea supports few plants
except the minute one-celled plants, the diatoms, of which
there are many species and an almost infinite number of
individuals. These furnish about the only food for the
animals of the open sea except that obtained by preying
upon one another.
A great quantity of detached seaweed (Sargassum) , filled
with multitudes of small marine animals and the fishes
which prey upon
them, covers the sur-
face of the middle
Atlantic, the center
of the oceanic eddy.
Through this Colum-
bus sailed from the
16th of September
to the 8th of Octo-
ber, 1492, greatly to
his own astonishment
and to the terror of
his crew, who had never before heard of these " oceanic
meadows."
The animals of the sea vary in size from the microscopic
globigerina (page 400), whose tiny shells blanket the beds
of the deeper seas, to the whale, that huge giant of the deep,
in comparison with which the largest land animals are but
pygmies. Although monarch of all the finny tribe, it is
not a fish at all, but a mammal which became infatuated
with a salt-water life and so through countless ages has more
and more assumed the finny aspect. It is obliged to rise
A SMALL SHARK
Photographed under water.
LIFE OF THE SEA 533
to the surface to breathe. It cares for its young like other
mammals.
Here, too, are found the jellyfish, the Portuguese man-of-
war (Figure 171), some fishes, many crustaceans, a few in-
sects, turtles, snakes, and mammals. Most of these animals
are lightly built and are well equipped for floating and
swimming. Some sea animals, like the oyster, barnacle,
and coral polyp, are fixed, and rely upon the currents of
the water to bring them their food, while others, like the
crab, the lobster, and the fish, move from place
to pbce in search of prey.
In the warmer seas the surface water is often
filled with minute microscopical animals which
have the power, when disturbed, of emitting
light, so that when a boat glides through these
waters at night, a trail of sparkling silver, called
phosphorescence, seems to follow in the wake. *
Between the surface and the bottom of the FlGURE 1T1
deep ocean there seems to be a vast depth of water almost
devoid of life. This region, like the bottom of the ocean,
has been little explored and there may be life here which has
not been discovered. From the bottom of the sea the
dredge has brought up some very curious forms of life.
Here under tremendous pressure and in profound darkness
have been developed species of carnivorous fishes.
Some of these have large, peculiarly well-developed eyes
and others have not even the rudiments of eyes. As the
light of the sun never penetrates to these depths, it would
seem at first that eyes could be of no use, but it has been
found that some of the animals of the ocean bottom have
the power of emitting light in some such way as the glow-
worm and firefly do, and it is probable that it is to see
534 LIFE AS RELATED TO PHYSICAL CONDITIONS
FLYING FISH
Notice how the front fins have become
wing-like
this phosphorescent light that the eyes of the animals are
used. There are no plants here and the life is much less
abundant and less
varied than near the
surface.
There is but little
variation in the con-
ditions surrounding
the animals of the
sea, and so the organs
corresponding to
these conditions are
not diverse. Living
in a buoyant medium
dense enough to sup-
port their bodies, and of almost unvarying temperature, the
sea animals have never required or developed varied organs
for locomotion, like
the wing, the hoof
and the paw, or for
protection from cold,
like the feather, the
hair, or wool. It is
true that certain sea
dwellers, like the seal,
are covered with
hair, but these air
breathers were prob-
ably originally a land
type and have ac-
quired the habit of SEALS
living in the Water. Originally land animals.
LIFE OF THE LAND
535
The highest traits of animal life, such as are found in land
animals, have not been required or acquired by the sea
animals, and although the number of species and kinds
is very great, there is not found among them the same grade
of intelligence or power of adaptability, as among the
land animals.
Life of the Land. — The highest development of both
plant and animal life is found upon the land. Here ^t the
meeting place of the solid-
earth and its gaseous en-
velope, subjected to great
variations in amount of
sunlight, moisture, tem-
perature, and soil, the
plants and animals have
acquired a marvelous
variety of forms and
structures to adapt them
to their varied surround-
ings, and to enable them
to secure a living.
Some plants lift their
strong arms high into the
air to intercept the sun- PRICKLY PHLOX •
beams before they strike Notice the thorn?tsbjf which {i protects
the earth, while others
clothe the surface with a dress of varied green. In some
plants, odor, nectar, or juicy berries attract the animals
whose aid is needed for fertilizing and scattering their seeds,
while in others, noxious odors, prickles, thorns, and acrid
secretions ward away animals destructive to their welfare.
536 LIFE AS RELATED TO PHYSICAL CONDITIONS
The highest perfection of beauty, utility, and productiveness
among plants has been reached by those of the land.
The animals of the land, surrounded by the air, which
bears no food solutions to inert mouths, must be well en-
dowed with the power of motion in order to procure their
food. They must either crawl
over the surface or be provided
with appendages to support their
weight against gravity. There is
no floating indolently in the air as
in the water. Movement, exer-
tion, search, are the requisites of
life on land. The eggs and young,
as a rule, cannot be abandoned to
hatch and to care for themselves ;
the nest, the burrow, the den must
be provided. This is the realm of
homes.
/^ The land animals are also the
/, lam& I most intelligent. Birds long ago
solved the problem of flight for a
body heavier than air, which is
now being successfully solved by
man after years of effort. Cer-
tain animals, like the bee, the
ant, and the squirrel, have the provident habit of storing
up food in the summer against a day of need. Other ani-
mals, like the birds, have learned to migrate to a warmer
clime when winter comes. The beaver is probably the
pioneer in hydraulic engineering. When he feels the need
of a water reservoir, he builds a dam and makes it. To-
day many a swamp in the northern states owes its origin
BIRD'S NEST
A simple home.
DISTRIBUTION OF ANIMALS 537
to him. Wonderful indeed is the intelligence of many of
the land animals, due in large part to their development
amid varied geographical conditions.
DOUBLE BEAVER DAM AND BEAVER HOUSE
In the foreground, one of the dams is plainly visible. In the background
is a second dam running almost parallel to the first. To the right in
the quiet water is the beaver house. To the left are stumps of trees
that were felled by the beavers. Picture taken in Estes Park, Colorado,
by Frank M. Hallenbeck of Chicago.
•
Distribution of Animals. — An examination of a globe
shows (1) that the land is massed around the north pole,
(2) that the three continental masses to the south are
separated from one another by wide seas, and (3) that
while two of these are connected by narrow strips of land
to northern continents, the third is entirely separated from
all other land.
But slight changes in elevation would connect the northern
continents with one another. As they are so closely related
538 LIFE AS RELATED TO PHYSICAL CONDITIONS
to one another, it might be expected that the animals of
these continents would resemble one another, particularly
in the more northern
parts. This is true.
Bears, wolves, foxes,
elk, deer, and sheep of
nearly related species
are found distributed
over the northern con-
tinents.
The animals of the
southern continents
are much less nearly
related. The ostrich,
giraffe, zebra, and hip-
popotamus are among
the characteristic ani-
mals of Africa which are not found elsewhere. In South
America the tapir, great anteater, armadillo, and llama
are among the animals not represented elsewhere. Both
of these continents,
however, have ani-
mals ^closely related
to those of other
great divisions, show-
ing that their present
isolation has not con-
tinued far back in
geological time.
The animals of
Australia differ
greatly from those
OSTRICHES
The largest of all birds.
OPOSSUM
Many opossums have no pouch but carry
their young on their backs.
DISTRIBUTION OF ANIMALS
539
of the other continents. The quadrupeds here are marsu-
pials, animals which usually carry their young in a pouch.
The only members of the family existing at present else-
where are the American opossums. The largest of the
marsupials is the great kangaroo, which measures between
seven and eight feet from its nose to the tip of its tail. Al-
though it has four feet, yet it runs by making extraordinary
KANGAROO FEEDING
leaps with its strong hind feet. Here is also found one of
the most singular of all living animals, the duckbill, the
lowest of all quadrupeds, which in its characteristics re-
sembles both quadrupeds and birds.
All this seems to show that the distribution and devel-
opment of the animals of the different continents have been
largely dependent upon the former geographical relations
of the land masses. The native animals of a region are
540 LIFE AS RELATED TO PHYSICAL CONDITIONS
not necessarily the only ones suited to it ; animals from
other places may be even better adapted, but they have
been kept out by some natural barrier. This is particu-
larly evident in the case of Australia, where the weak native
animals would have been readily displaced by the stronger
animals of Asia could these have reached that isolated con-
tinent.
Life on Islands. — Islands which rise from the conti-
nental shelves were probably at one time connected with
the continents, but have since been separated by the sub-
mergence of the intervening lowland. The animals and
plants of such islands are similar to those of the adjacent
large land masses. But oceanic
islands possess only those types
of plants and animals which
originally were able to float or
fly to them over the surround-
ing water expanse. Indigenous
mammals, except certain species
of bat, are wanting. Birds are
abundant.
On the tropical islands the
cocoanut palm furnishes the main
supply of vegetable food, cloth-
ing, and building material. Many of the species of both
plants and animals are different from those of the nearest
continent and even of the adjacent islands. So complete
has been the isolation of the life on these islands for so long
a time that it has been possible for great differences in
species to develop. Large unwieldy birds unable to fly or
run rapidly have been found on some oceanic islands, the
THE DODO
Although the dodo is extinct,
sufficient remains have been
found to enable scientists to
tell how it looked.
LIFE OF MAN AFFECTED BY PHYSICAL FEATURES 541
dodo of Mauritius, now extinct, being one of the most
notable.
The absence of predatory animals has probably made the
development of such forms possible. The great species
of tortoise from the Galapagos Islands perhaps owes its
development to the same cause. Nowhere else have such
huge tortoises been found. The remarkable fauna and
flora found on oceanic islands may be regarded as due to
their geographical isolation.
Life of Man as Affected by Physical Features. — Moun-
tains offer a retreat to persecuted people as well as to ani-
mals. Here are often found the races which once inhabited
A COTTAGE IN THE SCOTCH HIGHLANDS
the surrounding plains, but which have been driven from
them by conquerors. The people of Wales and the Scotch
Highlanders are probably descendants from more ancient
inhabitants of the island than those in control to-day. The
542 LIFE AS RELATED TO PHYSICAL CONDITIONS
Pyrenees, the Caucasus, and the Himalaya Mountains each
contain tribes which were driven from the lower plains,
but have been able in these retreats to withstand invaders
who were too powerful for them in their former homes.
Old-fashioned customs still maintain their hold in remote
mountain regions long after they have been discarded in
the surrounding country where intercommunication is
easier. In some of the Scotch Highlands the natives still
CRIPPLE CREEK
One of the largest mining camps in the world.
cling to their ancient dress, and in sections of the southern
Appalachian Mountains many of the customs of the early
pioneers are still common.
In mountain regions rich in ores, mining naturally be-
comes the chief industry, and here, if there were any secluded
native inhabitants, these have been replaced by the energetic
miners from distant places. The deep and remote valleys
and mountain sides have become the homes of mining
camps and cities. Railroads have been built to these,
overcoming almost impassable obstructions, and ore crush-
EFFECT OF MOUNTAINS ON HISTORY 543
ing and smelting works supply the places of the mills and
factories of the manufacturing cities. When the ore fails,
the army of workers moves on, and the city, once thriving
and booming, becomes suddenly simply an aggregation of
empty dwellings.
Modern irrigation has developed many barren uplands
into wonderfully successful agricultural districts.
Effect of Mountains on History. — Not only have moun-
tains been retreats for the vanquished, but they have been
barriers against further conquest by the conquerors. It
is very difficult for an army to traverse a mountain range.
For a long time the Alps hemmed in the power of Rome.
One of the greatest exploits of Hannibal and later of Napo-
leon was the passage of these same mountains.
In our own country the Appalachian Mountains acted
for a long time as an impassable barrier to the expansion
of the Thirteen Colonies. The trails across them were
so long and difficult that it was many years before the fer-
tile plains on their western side became populated. The
Mohawk valley opened a comparatively easy route at the
north, but the Cumberland trail at the south was long,
circuitous, and full of places suitable for Indian ambuscade.
The little mountain country of Switzerland is a buffer
state for the rest of Europe. Afghanistan, rough, moun-
tainous, and desert, is a buffer state for Asia. It may
happen that mountain boundaries are so broad and compli-
cated that a little country inserts itself along the boundary
of two powerful nations and is able to protect itself from
being absorbed by either. The little country of Andorra,
containing only 150 square miles, situated in a lofty valley
on the southern slope of the Pyrenees, with a population
544 LIFE AS RELATED TO PHYSICAL CONDITIONS
not exceeding 10,000, has remained independent for nearly
a thousand years in spite of its powerful neighbors.
Life on Plains. — The life conditions on plains are very
different from those in places where the irregularities of
the surface are great. Movement is as easy in one direc-
tion as in another, and the lines of travel tend to be straight.
A HERD OF CATTLE ON THE GREAT PLAINS
There is usually no reason for an accumulation of popula-
tion in any one place, so the population tends to be uni-
formly distributed.
As movement from place to place is easy, it is not dif-
ficult for the inhabitants of a plain to mass themselves
together at one point. In case of invasion by a superior
enemy there is no place for hiding or safe retreat, and sub-
jection or extermination are the alternatives, unless the
plain is so large that the enemy is unable to spread over
it. In the case of animals this has been shown in the prac-
tical extermination of the American bison and antelope.
LIFE ON PLAINS
545
In the case of men it was shown on the plains of Russia
in the thirteenth century when the Tartars conquered the
region and threatened to overrun Europe.
Another instance was that of the fatal invasion of Russia
by Napoleon. The Russians, unable to find a strategic
place to make a stand, retreated farther and farther into
the plain. The depletion of Napoleon's army, due to the
A HERD OF BISON
extent of territory which must be held in his rear, the dis-
tance from his base of supplies, and the rigor of the Russian
winter, forced him to begin that disastrous retreat, the fatal
results of which probably led to his final overthrow.
Plains have always played an important part in history.
Here armies can march and countermarch with compara-
tive ease. Large bodies of men can easily be assembled.
Military stores can be readily collected and all the opera-
tions of war carried on without natural obstructions. Thus
546 LIFE A£ RELATED TO PHYSICAL CONDITIONS
it happens that certain plains have been
innumerable wars. The great plain of
phrates was the gathering ground and
ancient monarchies. The plains of the
arena in which embattled Europe has
deadliest strifes, while the level lands of
dyed again and again with the blood
the seats of almost
the Tigris and Eu-
battlefield of vast
Po have been the
settled some of its
Belgium have been
of thousands and
A PART OF THE PLAIN OP* WATERLOO, BELGIUM
thousands of Europe's bravest sons. The brutal invaders
of 1914 cynically admitted that they overran Belgium be-
cause it was the shortest and easiest military route to Paris.
Life on Coastal Plains. — The valuable minerals of the
earth are usually found in the older rocks, so there is no
mining on a coastal plain, and because the rivers are shal-
low and fall over no ledges as they flow across these plains,
no great water power for manufacturing can be developed.
The sluggish streams are often dammed and small water
LIFE ON COASTAL PLAINS
547
powers developed, but there is not the fall necessary for
large factories, except sometimes in the hilly region back
near the old land where the rivers have developed rather
deep and narrow valleys, and mill ponds of considerable
size may be made.
As the different kinds of soil lie in belts, agriculture will
vary with the belts. In warm climates rice can be raised
along the shore where the -land is marshy. On the sandy
land most profitable
truck farming is pos-
sible if the transpor-
tation facilities are
good. In many
places in the south-
ern states these sandy
areas support fine
forests of pine (page
344), which are most
valuable for the pro-
duction of turpen-
tine, tar, and lumber.
Where the soil is not •
too sandy and the climate is warm, cotton is raised in
abundance. The materials for making glass, pottery, and
brick are widespread over coastal plains.
The cities on coastal plains are usually found either
(1) near the coast, where the rivers have formed harbors
and so have made ocean commerce possible, or (2) at the
head of navigation in the rivers where water transporta-
tion begins, or (3) still farther up the river at the fall line,
where manufacturing on a large scale is possible.
The fall line is the point on a river where its bed passes
CRUDE TURPENTINE STILL
Turpentine is distilled from the pitch of
the pine.
548 LIFE AS RELATED TO PHYSICAL CONDITIONS
from the harder rock of the old land to the softer material
of the coastal plain. The softer material is worn away more
easily than the hard material, and falls or rapids are pro-
duced suitable for water power. A glance at a map of
the southeastern United States will show that the princi-
pal cities lie in line nearly parallel to the coast. Of those
PINEAPPLES
near the coast are Norfolk, Wilmington, Charleston, Sa-
vannah, Jacksonville; at the fall line, Trenton, Phila-
delphia, Richmond, Columbia, and Augusta.
Advantages of Harbors. — The importance to mankind
of good harbors cannot be overestimated. The latest and
greatest of all wars has especially emphasized this. Thou-
sands and thousands of men have been sacrificed in efforts
to obtain or to defend harbors.
No civilized country by its own products can supply all the
wants of its inhabitants. Since earliest times man has been
ADVANTAGES OF HARBORS
549
a barterer of goods. The sea offers him an unrestricted
highway for his traffic. Harbors he must have to load and
unload his wares safely.
Although many of the best harbors of the world are
found along depressed coasts, such as the harbors of New
York, San Francisco,
London, Liverpool,
and Bergen, yet there
are several other
sorts of harbors.
The delta of a great
river may afford a
good harbor, as those
of New Orleans and
Calcutta. Harbors
may be formed by
sand reefs and spits,
like those of Galves-
ton, Provincetown,
and San Diego. The
atolls of the mid-
Pacific and even the
submerged craters of
volcanic islands af-
ford safe resting
places where ships
may ride out the
storms.
All natural fea-
tures have a greater
. MINOT'S LEDGE LIGHTHOUSE
or less influence upon
Situated on a reef about 15 miles southeast
the inhabitants of of Boston.
550 LIFE AS RELATED TO PHYSICAL CONDITIONS
the earth, but perhaps none has so directly and obviously
influenced man's activities as has the kind of coast on
which he lives. Europe, with its harborful, and Africa
with its almost harborless coasts are in striking contrast
to each other. This difference between the inducements
SAN FRANCISCO HARBOR,
A harbor due to a depression of the coast.
to travel and commerce which the two continents afford
is one of the factors in producing the marked difference
in progress attained by the native peoples of the two con-
tinents. They stand to-day as types on the one hand of
economic progress and on the other, of stagnation.
The Phoenicians, the Carthaginians, the Greeks, the
English, and the other great nations of the world have
ADVANTAGES OF HARBORS
551
felt the enticing allurement of a captive sea waiting in
their harbors like a steed for them to mount and ride away
in quest of the world's best. Thus they have extended
their conquest and influence far beyond the homeland.
All nations regard adequate outlet to the sea as essential
CALIFORNIA, U. S. A.
One of the finest harbors in the world.
to progress. The struggle of all the great world powers to
strengthen their navies, no matter what the cost, shows
with what jealousy the products of their ports are guarded.
Coasts with harbors give their people the facilities and
inducements for seeking the unknown, while the harbor-
less coasts confine the aspirations of their inhabitants to
the products immediately around them. A glance at the
552 LIFE AS RELATED TO PHYSICAL CONDITIONS
coast line and harbors of Greece shows one cause of its
ancient civilization and a reason why the Greeks were
" always seeking some new thing."
SUMMARY
Physical conditions have a great effect on the distribution
of life upon the earth. It is hard for living things to cross
high mountains, broad oceans, or vast deserts. When con-
fined to certain climates and areas, plants and animals
naturally adjust themselves to these.
Life in the sea is so simple that plants and animals there
are not forced to become as highly developed as are those
of the land. On land there are greater ranges of climate
and other physical conditions, so that plants and animals
have been forced to a high development in order to survive.
Man is one of the greatest forces at present affecting land
life. He transplants and transports animals and plants
according to his desires. The physical conditions decide
whether or not they shall live.
The elevation of mountain regions, difficulty of travel,
and lack of agricultural lands cause these sections to be
sparsely settled by backward peoples unless mining has
attracted progressive settlers. Mountains have always
furnished safe retreats for persecuted peoples and have been
barriers to further conquest.
Life on the plains is usually most varied. But since the
plains offer no safe retreat, the inhabitants of level lands
have always been subject to invasion and conquest, and the
native animals to extermination. Coastal plains offer no op-
portunities for mining, but certain kinds of manufacturing and
agricultural pursuits are peculiar to such regions. Access to
QUESTIONS 553
the sea, which is the oldest and easiest highway, is essential
to the progress of a nation.
QUESTIONS
What do the rock layers show in regard to the history of life ?
Give several reasons why the same kinds of plants and animals
are not found all over the earth.
How has the glacial period affected plants and animals and
man's activities?
What plants and animals do you know that are particularly
adapted to the conditions in which they live? .
How does the life of the sea differ from that of the land?
How has the distribution of animals been affected by geographical
conditions ?
How have different physical features of the earth affected man's
life and history?
APPENDIX
Units. — To measure any physical quantity a certain
definite amount of the same kind of quantity is used as the
unit. For example, to measure the length of a body, some
arbitrary length, as a foot, is chosen as the unit of length;
the length of a body is the number of times thfa unit is con-
tained in the longest dimension of the body. The unit is
always expressed in giving the magnitude of any physical
quantity ; the other part of the expression is the numerical
value. For example, 60 feet, 500 pounds, 45 seconds.
In like manner, to measure a surface, the unit, or stand-
ard surface, must be given, such as a square foot; and to
measure a volume, the unit must be a given volume, such,
for example, as a cubic inch, a quart, or a gallon.
Systems of Measurement. — Commercial transactions in
most civilized countries are carried on by a decimal system
of money, in which all the multiples are ten. It has the
advantage of great convenience, for all numerical operations
in it are the same as those for abstract numbers in the dec-
imal system. The system of weights and measures in use
in the British Isles and in the United States is not a dec-
imal system, and is neither rational nor convenient. On
the other hand most of the other civilized nations of the
world within the last fifty years have adopted the metric
system, in which the relations are all expressed by some
power of ten. The metric system is in well-nigh universal
use for scientific purposes. It furnishes a common numer-
ical language and greatly reduces the labor of computation.
555
556 EVERYDAY SCIENCE
Measure of Length. — In- the metric system the unit
of length is the meter. In the United States it is the dis-
tance between two transverse lines on each of two bars of
platinum-iridium at the temperature of melting ice. These
bars, which are called " national prototypes," were made
by an international commission and were selected by lot
after two others had been chosen as the " international pro-
totypes " for preservation in the international laboratory
on neutral ground at Sevres near Paris. Our national
prototypes are preserved at the Bureau of Standards in
Washington. The two ends of one of them are shown below.
The only multiple of the meter in general use is the kilo-
meter, equal to 1000 meters. It is used to measure such
distances as are expressed in miles in the English system.
ENDS OF METER BAR
The Common Units in the Metric System are
1 kilometer (km.) = 1000 meters (m.)
1 meter =100 centimeters (cm.)
1 centimeter =10 millimeters (mm.)
The Common Units in the English System are :
1 mile (mi.) = 5280 feet (ft.)
1 yard (yd.) = 3 feet
1 foot =12 inches (in.)
By Act of Congress in 1866 the legal value of the yard
is tftf meter ; conversely the meter is equal to 39.37 inches.
The inch is, therefore, equal to 2.540 centimeters.
APPENDIX
557
The unit of length in the English system for the United
States is the yard, defined as above. The relation between
the centimeter scale and the inch is shown below.
100 MILLIMETER8=r 10 CENTIMETERS = 1 DECIMETER = 3. 937 INCHES.
Square inch
INCHES AND TENTHS
CENTIMETER AND INCH SCALES
Measures of Surface. — In the metric system the unit
of area used in the laboratory is the square centimeter
(cm.2). It is the area of a square the edge of which is
one centimeter. The square meter (m.2) is often employed
as a larger unit of area. In the Eng-
lish system both the square inch and the
square foot are in common use. Small
areas are measured in square inches, while
the area of a floor and that of a house lot
are given in square feet ; larger land areas
are in acres, 640 of which are contained in
a square mile.
The square inch contains 2.54 X 2.54
= 6.4516 square centimeters. The relative sizes of the two
are shown in the accompanying figure.
k The area of regular geometric figures is obtained by computation
from their linear dimensions. Thus the area of a rectangle or of a
parallelogram is equal to the product of its base and its altitude
(A = b X h) ; the area of a triangle is half the product of its base
and its altitude (A = \b X h) ; the area of a circle is the product of
3.1416 (very nearly 2^) and the square of the radius (A = Trr2) ;
the surface of a sphere is four times the area of a circle through its
center (A = 4 Trr2).
SQUAKE CENTIMETER
AND SQUARE INCH
558'
EVERYDAY SCIENCE
Cubic Measure. — The smaller unit of volume in the
metric system is the cubic centimeter. It is the volume of
a cube the edges of which are one centimeter long. The
cubic inch equals (2.54)3 or 16.387
cubic centimeters. The relative sizes
of the two units are shown here.
In the English system the cubic foot
and cubic yard are employed for larger
volumes. The cubical capacity of a
room or of a freight
car would be ex-
CUBIC CENTIMETER AND pressed in cubic feet ;
the volume of build-
ing sand and gravel or of earth embank-
ments, cuts, or fills would be in cubic yards.
The unit of capacity for liquids in the
metric system is the liter. It is a decimeter
cube, that is, 1000 cubic centimeters. The
imperial gallon of Great Britain contains
about 277.3 cubic inches, and holds 10
pounds of water at a temperature of 62°
Fahrenheit. The United States gallon has
the capacity of 231 cubic inches.
Common Units in the Metric Svstem :
CYLINDRICAL GLASS
GRADUATE
1 cubic meter (m.3) = 1000 liters (1.)
1 liter = 1000 cubic centimeters (cm.3)
Common Units in the English System :
1 cubic yard (cu. yd.) = 27 cubic feet (cu. ft.)
1 cubic foot = 1728 cubic inches (cu. in.)
1 U. S. gallon (gal.) = 4 quarts (qt.) = 231 cubic inches
1 quart = 2 pints (pt.)
APPENDIX
559
The volume of a regular solid, or of a solid geometrical figure, may
be calculated from its linear dimensions. Thus, the number of cubic
feet in a room or in a rectangular block of marble is
found by getting the continued product of its length,
its breadth, and its height, all measured in feet. The
volume of a cylinder is equal to the product of the #rea
of its base (?rr2) and its height, both measured in the
same system of units.
Liquids are measured by means of graduated vessels
of metal or of glass. Thus, tin vessels holding a gal-
lon, a quart, or a pint are used for measuring gasoline,
sirup, etc. Bottles for acids usually hold either a
gallon or a half gallon, and milk bottles contain a
quart, a pint, or a half pint. Glass cylindrical grad-
uates and volumetric flasks are used by pharma-
cists, chemists, and physicists to measure liquids.
In the metric system these are graduated in cubic VOLUMETRIC
centimeters. MASK
Units of Mass. — The unit of mass in the metric system
is the kilogram. The United States has two prototype
kilograms made of
platinum-iridium and
preserved at the Bureau
of Standards in Wash-
ington. The gram is
one thousandth of the
kilogram. The latter
was originally designed
to represent the mass
of a liter of pure water
at 4° C. (centigrade
scale) . For practical
purposes this is the
STANDARD KILOGRAM kilogram. The gram IS
560 EVERYDAY SCIENCE
therefore equal to the mass of a cubic centimeter of water at
the same temperature. The mass of a given body of water
can thus be immediately inferred from its volume.
The unit of mass in the English system is the avoirdupois
pound. The ton of 2000 pounds is its chief multiple; its
submultiples are the ounce and the grain. The avoirdupois
pound is equal to 16 ounces and to 7000 grains. The " troy
pound of the mint " contains 5760 grains. In 1866 the mass
of the 5-cent nickel piece was legally fixed at 5 grams ; and
in 1873 that of the silver half dollar at 12.5 grams. One
gram is equal approximately to 15.432 grains. A kilogram
is very nearly 2.2 pounds. More exactly, one kilogram
equals 2.20462 pounds.
All mail matter transported between the United States and the
fifty or more nations signing the International Postal Convention,
including Great Britain, is weighed and paid for entirely by metric
weight. The single rate upon international letters is applied to the
standard weight of 15 grams or fractional part of it. The Inter-
national Parcels Post limits packages to 5 kilograms; hence the
equivalent limit of 11 pounds.
Common Units in the English System :
1 ton (T.) = 2000 pounds (Ib.)
1 pound =16 ounces (oz.)
1 ounce = 437.5 grains (gr.)
Common Units in the Metric System :
1 kilogram (kg.) = 1000 grams (g.)
1 gram = 1000 milligrams (mg.)
The Unit of Time. — The unit of time in universal use
in physics and by the people is the second. It is S6100
of a mean solar dav. The number of seconds between
APPENDIX 561
the instant when the sun's center crosses the meridian of
any place and the instant of its next passage over the same
meridian is not uniform, chiefly because the motion of the
earth in its orbit about the sun varies from day to day.
The mean solar day is the average length of all the variable
solar days throughout the year. It is divided into 24 X
60 X 60 = 86,400 seconds of mean solar time, the time re-
corded' by clocks and watches. The sidereal day used in
astronomy is nearly four minutes shorter than the mean
solar day.
The Three Fundamental Units. — Just as the measure-
ment of areas and of volumes reduces simply to the measure-
ment of length, so it has been found that the measurement
of most other physical quantities, such as the speed of a ship,
the pressure of water in the mains, the energy consumed by
an electric lamp, and the horse power of an engine, may be
made in terms of the units of length, mass, and time. For
this reason these three are considered fundamental units
to distinguish them from all others, which are called derived
units.
The system now in general use in the physical sciences
employs the centimeter as the unit of length, the gram as
the unit of mass, and the second as the unit of time. It
is accordingly known as the c. g. s. (centimeter-gram-second)
system.
PROJECTS
PROJECT I. — How a Boy Scout Determines Directions by the Stars,
pages 9 and 10
Determining directions by the stars requires a little practice.
The necessary information may be found on pages 9 and 10 of
the body of the book. When you are in some locality where you
know the points of the compass, turn to the northern sky on a
clear night and see if you can locate the Big Dipper (Diagram,
p. 10).
Remember that the stars in the north appear to go around in a
circle once every twenty-four hours (p. 8), and so you may find the
Big Dipper near the zenith (the point of the sky directly overhead),
down near the horizon, or somewhere on its circuit between these
two points. Rotate the diagram on page 10 about Polaris as a
center, and you will observe all the relative positions to the North
Star which the Big Dipper may occupy.
If you live hi the southern portion of the United States, part of
the Big Dipper may disappear below the horizon when the con-
stellation swings below the North Star; but the "pointers" are
generally in sight. If you will follow the direction indicated by
these "pointers," as shown in the diagram on page 10, you will
find Polaris very easily. It is a lonesome-looking star, because it is
fairly bright and is surrounded by stars of lesser brilliance. To
identify it further, see if you can trace the Little Dipper. The
North Star forms the tip end of the handle (Diagram, p. 10).
Now see if you can locate the constellation of Cassiopeia's Chair.
It is about as far from the North Star as the Big Dipper and always
on the opposite side of Polaris from that constellation (Diagram,
p. 10) . Above the North Star, it is M-shaped ; below Polaris, it
is inverted into a W-shaped cluster.
563
564 EVERYDAY SCIENCE
Learn to recognize these three northern constellations so that
you can trace them readily, and you will be able to locate the North
Star without difficulty. Then when you are in a strange locality,
the northern sky will seem familiar to you and will guide you
unerringly.
When you have located the North Star, face it with arms out-
stretched to right and left. The right arm points to the east;
the left arm to the west.
PROJECT II. — How a Boy Scout Determines Directions by Day,
pages 23, 24, 37, 38
(a) To determine directions with the aid of a watch, point the
hour-hand toward the sun. To do this accurately, hold the watch,
face upward, in the palm of your hand. Hold a match or a straight
twig upright at the edge of the dial and turn the watch until the
hour-hand points toward the match and the shadow of the match
lies directly along the line of the hour-hand.
The point on the dial halfway between the hour-hand and the
figure XII will then indicate south with a fair degree of accuracy.
Thus, if the hour-hand is at X, the figure XI on the dial will point
toward the south ; if the hour-hand is at III, the mark on the dial
that indicates 1 : 30 will point toward the south.
EXPLANATION. — The reason for this is that on a day of average
length (twelve hours) the sun appears to describe a half-circle in the
sky while the hour-hand of your watch is describing a complete circle.
If the watch and the sun both described a semicircle in the same length
of time, the figure XII would always point toward the south if the hour-
hand were aimed at the sun. But since the hour-hand travels its cir-
cuit twice as fast as the sun, it is necessary to halve the distance between
the hour-hand and the figure XII in order to find the point on the dial
that indicates the south.
(6) A "reliable pocket compass may be had for a reasonable sum.
Learn from some surveyor the declination (p. 38) for your imme-
diate section so that you may determine the true north accurately;
You may purchase magnetic charts from the United States Geolog-
PROJECTS 565
ical Survey which will show the variation for any section accurately.
Only be sure that you have the latest issue of the chart, because the
declination of the needle slowly changes from time to time (pp.
38, 39).
Set your compass in a place, as nearly level as possible, away
from the vicinity of steel and iron. Then allow for the declination
and you will have the true north.
If you cannot afford a compass, make one as suggested in Exper-
iment 8, pages 37 and 38. To use this satisfactorily, you will have
to train your eye to gauge the declination. This you can do by
floating the cork compass at the side of a manufactured compass
as often as you have opportunity. Train the eye to recognize the
declination of the floating compass by comparing it with the
measured decimation on the manufactured compass.
Put the cork in your pocket and carry the magnetized needle in a
small glass phial. You can set this compass wherever there is
water.
(c) Hard and fast rules for telling direction by the growth of
mosses and lichens and other vegetation in forests are responsible
for a good deal of current misinformation. Writers sometimes give
specific information for certain regions, and amateur woodsmen
get the impression that the instructions are true for all times and
places.
Practiced guides, like the Indians of old, can tell direction within
a very few degrees of perfect accuracy by observing forest vege-
tation. This ability comes of long and acute observation and can-
not be cultivated by rule. A few basic facts may be given, along
with advice that accurate information for any section can come
only of close observation and reasoning.
As a rule, mosses and lichens grow on the cool or shady side
of a tree. In the North Temperate zone, this is generally the north-
ern side, but it may vary with the immediate surroundings and with
the direction of the prevailing winds and rains. For instance,
trees growing on a north slope, where the sun has no access to them,
are coolest and dampest on the side toward the ground, and may
therefore have moss on the south side.
566 EVERYDAY SCIENCE
To offset this cause of confusion, it is well to remember that in
such sections underbrush and small plants grow more densely on a
northern exposure than on a southern exposure, because the sun
does not get a chance to dry out the north slope so thoroughly.
The practiced guide knows too that mosses grow where they can
have not only shade but an abundance of moisture. The prevail-
ing winds, therefore, may have something to do with local variation
of moss growths.
If you are near a forest, make a study of conditions that prevail
there and report on them to the class. Take your compass with
you. Find out on which side of trees the moss growths usually
occur. If not on the north side at all times, see if you can offer a
reason for the variation. Study the vegetation and soil on all slopes,
if you are in a hilly or mountainous region, and report the results
of your observations.
If you will be constantly on the alert, in whatever sections
you traverse, you will eventually accumulate much valuable forest
lore.
PROJECT III. — How a Boy Scout Determines Latitude by the North
Star, page 32
Choose a straight post or tree from which the North Star may be
sighted. Nail a smooth piece of board, about a foot square, to the
east or west side of the post or tree so that you can sight the North
Star along the face of the board.
Drive a six-penny or eight-penny wire nail straight and securely
into the upper north corner of the face of the board (K), and sus-
pend a plumb line from the nail (KL) . Now from the south edge
of the board, sight along the face of it until you can see the North
Star immediately under the wire nail. Then move the point of a
knife, or scratch-awl, along the face of the board near your eye until
you can just sight the North Star over the edge of the blade. When
the knife reaches this spot, stick the point of the knife-blade care-
fully into the board. If you have sighted accurately, the star can
be seen just under the nail and over the knife blade. If the eye
PROJECTS
567
be moved ever so little up or down, either the nail or the knife-
blade will cut off the light of the star.
Now you are ready to draw three lines on the face of the board,
and you probably will need an artificial light. With a ruler, draw
a line exactly corresponding to the plumb line (KL). Then draw
FIGURE 1
a straight line from the point of the nail to the edge of the knife
blade (KT). With a carpenter's square, draw a line (TU) at right
angles to the plumb line. The number of degrees in the angle at T
will be approximately equal to your latitude. If you haven't a
protractor to measure this angle, take the board to the laboratory
and measure the angle.
EXPLANATION. — If we could draw a line from the center of the
earth to the point where we stand (KL, Figure 2), we should have a
line running "straight down" (p. 24). Since the weight of a plumb
line points to the center of the earth, the direction of the plumb line
568
EVERYDAY SCIENCE
(KL, Figure 1) is "straight down." Now if a line should be drawn at
the earth's surface (TD, Figure 2) at right angles to the first line, it
would indicate* our horizon, or line of
vision along the earth's surface. The
line TD on the board (Figure 1) is drawn
at right angles to the plumb line and
may, therefore, be regarded as our horizon
line.
Now suppose we were standing at the
north pole (K, Figure 2). The North
Star would be directly overhead, and the
line of light from the star to the eye
(K — N-S, Figure 2) would be at right
angles, 90°, to our horizon line (TD, Fig-
ure 2). Thus the angle of the North Star
above the horizon line at the north pole, 90°,
equals the latitude of the north pole, 90°.
Suppose we should travel along a meridian line to a point midway
between the north pole and the equator, 45° latitude (K, Figure 3).
The North Star would no longer be overhead, but would be about half-
FlGURE 2
D
I)
FIGURE 3
FIGURE 4
way between the zenith and the horizon. The line of light from Polaris
to the eye (K — N-S, Figure 3) would, therefore, form about half a right
angle, 45°, with our horizon line (TD).
Suppose we should travel on to the equator, 0° latitude (K, Figure
4). The North Star would then be on the horizon. The line of light
PROJECTS 569
from it (K — N-S, Figure 4) would be identical with the horizon line
(TD), and there would be no angle, 0°. From this it can be seen that,
in order to measure our latitude, we need only measure the angle of
the North Star above the horizon.
Your calculations may be as much as one degree off, one way or the
other. But if you will make your observations on a night when the
constellation of Cassiopeia is just as high above the horizon as the
North Star, you will get accurate results. See the " Boy Scouts' Hand-
book," p. 96, and Figure I, on page 10 of this book, and report on this
to the class.
PROJECT IV. — Star Projects Varying with the Seasons, pages 1-18
The two other constellations in the northern heavens that are
shown in the diagram on page 10 are Cepheus and the Dragon
(Draco) . After you are able to locate with certainty the other three
constellations we have talked about, you will probably be able to
trace these two constellations.
Two of the best known stars in the northern heavens are Vega
and Arcturus. The two stars forming the inside edge of the Big
Dipper next to the handle form a line which points past the head
of the Dragon toward a large, brilliantly white star. This is Vega.
The two stars that form the bottom of the Little Dipper form a
line pointing away from the Pole toward a very bright reddish star
of the first magnitude. This is Arcturus, mentioned on page 7
of this book.
Since the earth, by reason of its revolution around the sun as
well as its rotation, gradually changes its position in relation to the
stars, there is a noticeable change of the evening sky map from month
to month. The best way to make a study of the evening sky for
any particular month is to obtain a copy of the "Monthly Evening
Sky Map," l a little journal for amateur astronomers. By means
of this, from month to month, you may identify the planets, im-
portant constellations (such as Scorpio, in midsummer ; and Orion,
in midwinter) and important stars, including Sirius, the Dog-Star,
1 "The Monthly Evening Sky Map," Leon Barritt, Publisher, 367
Fulton Street, Brooklyn, New York.
570 EVERYDAY SCIENCE
the brightest star in the heavens, which appears low on the southern
horizon in midwinter.
Among the many interesting books on the study of the stars are
the following :
"Earth and Sky Every Child Should Know," Rogers. Double-
day, Page & Co.
"Easy Star Lessons," Proctor. G. P. Putnam's Sons, New York.
"The Book of Stars," Collins. D. Appleton & Co., New York.
For those whose interest in the study of the heavens does not
wane, a most useful and interesting device is "The Barritt-Serviss
Star and Planet Finder." This is a cleverly constructed, revolving
chart which furnishes in a moment's time a map of the heavens for
any hour of any night of the year. Address Leon Barritt, Publisher.
(See footnote, p. 569.)
PROJECT V. — How to Clean Drain Pipes, pages 56 and 57
Nothing has a more important bearing on the health of a house-
hold than the condition of drain pipes leading from sinks, washbowl,
and bathtubs. Typhoid, diphtheria, and other deadly germs find
ideal breeding places in the grease and filth of these drains. House-
keepers who keep their homes otherwise immaculate sometimes for-
get the cleansing of drains because the unsanitary accumulations
are out of sight. No sink drain ought ever to go without attention
until the waste water runs slowly or the pipes are clogged.
If a sink becomes clogged, a cupful of lye in a wash-boilerful of
boiling water will generally cut the grease that has gathered and
holds other waste accumulations. Chloride of lime used in the
same proportions will accomplish the same purpose. The solution
should be poured in fast enough so that it will run through with
considerable force. If this fails, cover the opening to the drain and
fill the sink with a second boilerful of the solution. Then with a
force-cup (familiarly known as a "plumber's friend") force the
mixture down the drain pipe. This seldom fails to produce the
desired result.
PROJECTS 571
To keep a sink drain in sanitary condition, flush it daily, prefer-
ably in the evening, with a dishpanful of clear boiling water in which
a tablespoonful of washing soda has been dissolved. Once a week,
flush with a wash-boilerful of boiling water in which a teacupful of
chloride of lime has been dissolved. Lye must be handled with
such great care that it is best not to use it unless its use is made
necessary by clogged pipes. At any rate, chloride of lime is
fully as effective for disinfecting and almost as effective for
cleansing.
PROJECT VI. — How to Prepare Certain Acids and Bases for Re-
moving Stains, page 57
The most common acids for removing stains are lemon juice,
lactic acid (the acid found in sour milk and buttermilk), tartaric
acid, oxalic acid, and salts of lemon in solution. If spots can be re-
moved without the use of oxalic acid or salts of lemon, so much the
better. They are more apt to cause injury to fabrics than milder
acids, and besides they are rank poisons.
The most common bases for taking out stains are ammonia, bak-
ing soda, washing soda, borax, and Javelle water.
The least familiar of these acids and bases are probably tartaric
acid, oxalic acid, salts of lemon, and Javelle water.
Tartaric Acid. — This may be prepared by dissolving any given
quantity of cream of tartar in an equal or even smaller bulk of water.
The same effect may be had by wetting the stain thoroughly with
water and applying the dry cream of tartar. This is the more
common way of using it, because tartaric acid prepared as above
indicated will not "keep."
Oxalic Acid. — Dissolve commercial oxalic acid crystals in ten
times their bulk of water. If this solution proves too weak, add
crystals until desired strength is obtained. Painters use a very
strong solution of this (about one part of oxalic acid crystals to two
parts of water) for bleaching stains out of wood. The crystals dis-
solve much more quickly in boiling water, and the solution should
be used hot for bleaching wood.
572 EVERYDAY SCIENCE
Salts of Lemon. — This is the common name for oxalate of potash.
It may be purchased at a drug store under either name. It may be
used in solution, but is generally applied to a stain after the fabric
has been soaked in water — as in the case of cream of tartar.
Javelle Water. — Dissolve one fourth of a pound of chloride of
lime in a quart of boiling water, and a pound of washing soda in a
second quart of boiling water. Pour the two solutions together and
set the mixture aside to settle. Pour off the clear liquid and store
it in bottles or a stone jug. This is Javelle water, a very effective
bleaching solution for white cotton or linen.
Helpful Hints on the Treatment of Stains
Direction for removing stains must always depend both on the
nature of the fabric and on the kind of stain. Vegetable fibers,
such as linen and cotton, will stand more vigorous treatment than
wool, silk, or other animal fibers. The most common stains are
those of acids, alkalies, ink, grass, iron rust, fruit, mildew, tar, paint,
grease, and oil. The last four enumerated are more easily removed
by substances that will dissolve them or absorb them. They will
be discussed later. Here we are interested chiefly in stains that
may have to be removed by undergoing chemical changes.
Many stains may be removed by solution (Project XXVIII) or
absorption (Project XXXIV) before long exposure to the air brings
about certain chemical changes that set the stain. Since strong
acids and bases must be employed to remove such stains after they
are set, it is especially desirable that stains on delicate or colored
fabrics be treated while fresh. Thus the use of strong chemicals,
with consequent risk of injury to the cloth, may be avoided.
Where chemicals must be used, the milder agents should be tried
first, and the stronger acids or bases used only as a final resort.
When the stronger acids are used, they should be followed by
ammonia in order to neutralize the acid. It is often wise, especially
in the case of a valuable fabric, to make tests with a scrap of the
same or a similar piece of goods before running any risk with the
treasured article.
PROJECTS 573
Oxalic acid and salts of lemon may be used with care on any kind
of vegetable or animal fabric that is white. They will bleach colored
fabrics, but the color may often be restored by the use of ammonia
followed by chloroform. The most useful acid for removing stains
is probably tartaric acid. It cannot be made strong enough to in-
jure fabrics, and if the cream of tartar is mixed with an equal bulk
of salt, it is not likely to cause colors to run. It is only slightly
poisonous.
PROJECT VII. — How to Remove Acid Stains
Many acids will stain fabrics of any sort. Some acids which
will not affect white goods will stain colored goods, especially blues
and blacks.
To Bleach Acid Stains from White Cotton or Linen. — (a) Wash
the article, dip the stain in Javelle water, and rinse in clear cold
water. Or, (6) dampen the stain and expose it to the fumes of
burning sulphur.
To Neutralize Acid Stains in Goods of Any Fabric or Color. —
Apply ammonia to the stain. In the case of colored silk or other
delicate colored fabrics, apply the ammonia very gently. A camel's
hair brush or a medicine dropper is recommended for the purpose.
Take care not to rub the ammonia into the stain or it may cause the
color to run. If the color is affected, apply chloroform to restore it.
PROJECT VIII. — How to Remove Alkali Stains
White or Colored Goods. — If fabrics of any sort are stained by
washing soda, lime, or other strong alkalies, moisten the stain with
lemon juice, vinegar, or tartaric acid. Afterwards apply chloro-
form, if necessary to restore the color.
PROJECT IX. — How to Remove Ink Stains
Fresh Ink Stains. — (a} If possible, ink stains should be treated
immediately, before they have a chance to be set. Wet the fresh
574 EVERYDAY SCIENCE
ink spot immediately with water, or preferably with warm milk,
and cover it with dry starch, French chalk, or salt, or weight a clean
blotter on the stain. Remove the absorbent or change the blotters
as the ink is absorbed. Keep the spot wet and repeat the operation
until the ink is removed. This treatment is safe for any fabric.
If the milk leaves a greasy stain, remove it with benzine or carbona.
(6) For any fabric that will stand soap and water, melt pure tal-
low and pour it over the fresh ink stain. If the article is small, dip
it in the tallow. Remove the tallow after an hour or so with hot
water and soap. Many dyers and cleaners do this first, because it
cannot hurt the fabric and it may obviate the risk of using chemicals.
Old Ink Stains. — Test. — Before using any chemical on an ink
stain that has set, make the following test, if possible, of the ink
that caused the stain : Write a few lines on a piece of paper and allow
the ink to dry. Better than this, take a specimen of writing with
the ink that is several days or weeks old. If when the paper is
dipped in water the ink blurs or smirches badly, it probably con-
tains a coal-tar product known as nigrosine. The effect of certain
acids on this coloring matter is to make it almost indelible. In
such a case use a strong solution of washing soda or apply Javelle
water to the stain with a brush or sponge and rinse in clear cold
water from time to time. Do not use an acid.
To Remove Ink That Does Not Contain Nigrosine. — Old-fashioned
inks depended on a compound of iron for the black coloring. Most
modern blue-black inks have, in addition to an iron compound in
their make-up, certain aniline dyes. Acids mentioned below change
the iron compound so that it will dissolve in water, but the acid
must be followed by a bleaching compound to remove the color of
the aniline dyes. Following are the treatments suggested. The
first two are very mild treatments ; the third mild, but much more
effective ; while the fourth is to be reserved for very stubborn stains.
(a) Wet the stain with lemon juice and cover with salt. To
hasten the action of the acid and salt, expose to the sun, hold in the
steam of a tea-kettle, or lay the cloth over a plate that is used as a
cover for a sauce pan containing boiling water. Afterward expose
the spot to the fumes of sulphur (sulphur dioxide) or apply Javelle
PROJECTS 575
water with a brush or sponge. Rinse thoroughly in clear cold
water. Repeat if necessary.
(6) Soak in sour milk and salt or in buttermilk and salt. Cover
the stain with salt and expose to the sun.
(c) Wet the stain thoroughly and cover with cream of tartar.
Proceed then as in (a) . Most ink stains will yield to this treatment.
For Delicate or Colored Fabrics. — Wet the stain thoroughly and
cover with cream of tartar mixed with an equal bulk of salt. Sponge
very lightly with clear water and expose to sulphur fumes. If the
color is affected, apply ammonia with a camel's-hair brush or a
medicine dropper and follow with an application of chloroform.
Repeat if necessary.
(d) For Stubborn Spots on Heavy White Goods. — Wet the stain
thoroughly and rub in salts of lemon or oxalic acid with a small
stiff brush, keeping the stain over a hot plate as in (a). Sponge
with ammonia and bleach with sulphur fumes or Javelle water as
in (a). Rinse in clear water. Salts of lemon and oxalic acid are
very poisonous if taken internally.
PROJECT X. — How to Remove Grass Stains
(a) Sponge out the stain while it is fresh with clear water. If
this is not sufficient, sponge the stain with alcohol before it is set.
Do not use alcohol if the stain is several hours old.
(6) Another effective method for fresh stains is to cover the stain
with lard, allow it to stand thus for 24 hours, and then wash with
hot water and soap.
(c) If the stain is old, the green coloring matter of the grass has
undergone chemical changes by being exposed to air. Alcohol
will then change the green spot to a dark brown spot that will not
wash out. Wet an old stain and apply cream of tartar and salt in
equal bulk. If this leaves a light brown stain, sponge it with water.
If colored fabric is affected by this treatment, sponge with ammonia
and follow with an application of chloroform.
(d) An old grass stain on white goods may be removed by bleach-
ing with a mixture of equal parts of clear water and Javelle water.
576 EVERYDAY SCIENCE
PROJECT XI. — How to Remove Rust Stains
The simplest method is to wet the stain with lemon juice, cover
with salt, and expose to the sun.
If this fails, wet the stain and cover it with a mixture of equal
parts of cream of tartar and salt. Expose the spot to the sun, hold
it in the steam of a tea-kettle, or over a hot plate as suggested in
Project IX. This may be used on any kind of fabric and is not
likely to injure even colored fabrics. If it does affect colors, sponge
lightly with ammonia and follow with an application of chloroform.
On any white fabric, dilute oxalic acid, salts of lemon, or Javelle
water may be used. Follow either of the first two with ammonia
and rinse in clear water.
PROJECT XII. — How to Remove Fruit Stains
Fresh Fruit Stains. — All fruit, tea, and coffee stains should be
treated while they are fresh. Plum, peach, and blackberry stains
are especially stubborn if they become set. While the stain is
fresh, stretch the cloth over a bowl, cover the stain with baking
soda or washing soda, and pour 'boiling water through the cloth until
the soda is dissolved. If necessary, let the cloth sag into the water
in the bowl for a while.
Another method is to soak the fresh stain in warm milk and salt,
cover with salt, and expose to the sun.
Old Fruit Stains. • — To a fruit stain on any white fabric, apply
Javelle water, salts of lemon in solution or dilute oxalic acid and
follow with ammonia.
For wool, silk, delicate and colored fabrics, wet the stain with
a mixture of equal parts of alcohol and ammonia. Sponge gently
with alcohol until stain is removed. Sponge gently with chloroform
to restore color if necessary.
PROJECT XIII. — How to Remove Mildew
(a) If the fabric will stand it, boil in strong borax water,
(fe) Soak the stain in buttermilk or sour milk and salt, cover with
salt, and expose to the sun.
PROJECTS 577
(c) Soak the stain in lemon juice. Apply common salt and pow-
dered starch or salt and expose to the sun.
(d) Keep the stain wet with Javelle water and expose to the sun.
(e) Wash the stain with Ivory soap or any pure white soap. Rub
in powdered chalk with a flannel cloth. Cover with more chalk
and lay in the sun.
(/) Dissolve two teaspoonfuls of shavings of any hard white soap
in four teaspoonfuls of water, add a teaspoonful of starch, one half
teaspoonful of salt, and the juice of half a lemon. Mix thoroughly
and apply to the mildewed stain with a brush. Keep the spot wet
with this mixture until the stain disappears.
Of these six methods, 6, c, and/ are probably the most commonly
used.
PROJECT XIV. — How to Test Fabrics with Acids and Bases,
pages 55-57
There are numerous ways of testing fabrics to determine what
they are made of. Experts can easily distinguish the fibers of silk,
wool, cotton, linen, and other fabrics under the microscope. The
various fibers have their characteristic appearances and odors while
burning that may be observed and distinguished by experimenta-
tion. Very reliable tests may also be made with the aid of certain
acids and bases.
To Distinguish between Wool and Cotton. — If you are in doubt
as to whether a piece of goods is wool or cotton, boil a sample of it
for five minutes in a strong solution of caustic soda (sodium hy-
droxide). If it is all wool, it will dissolve completely. If it is all
cotton, it will not be visibly affected, except possibly to appear
somewhat shrunken and a bit more silky. If the fabric is mixed
wool and cotton, the wool will be dissolved, leaving the cotton that
was woven with it. If it is mixed wool and silk, the wool will dis-
solve first, leaving the silk. About 15 or 20 minutes more of
boiling will dissolve the silk.
Caustic soda and other strong alkalies dissolve wool very readily,
but do not so affect cotton. In fact, cotton is treated with caustic
578 EVERYDAY SCIENCE
soda as the first step in mercerizing it. Silk also dissolves in caus-
tic soda, but not so readily as wool.
To Distinguish between Silk and Mercerized Cotton. — Put a
little concentrated hydrochloric acid in a test tube and heat it
gently, stirring it with a chemical thermometer until the ther-
mometer registers 50° C. or a little less. Immerse a sample of the
fabric in the acid and keep it there for three or four minutes, being
careful to keep the acid at a fairly even temperature. If the fabric
is silk, the sample will be dissolved. If it is mercerized cotton, it
will remain intact. Concentrated hydrochloric acid will not dis-
solve either wool or cotton.
To Distinguish between Cotton and Linen. — The simplest test
to determine whether a fabric is linen or cotton is made, not with
an acid or an alkali, but with olive oil. . Thoroughly soak the fabric,
or a sample of it, in olive oil for about five minutes. Remove the
excess of oil by pressing the cloth between blotters. If the fabric
is linen, it will now be translucent. If it is cotton, it will be as
opaque as it was before soaking in the oil.
A most interesting book for anyone who is interested in chem-
istry in everyday life is "The Amateur Chemist," A. F. Collins.
D. Appleton & Co.
PROJECT XV. — How to Make Soap from Waste Fats at Home,
page 57
Collecting enough waste fats for a batch of soap is likely to prove
a tedious performance. If through carelessness or impatience
a pupil then fails to produce soap, there is a discouraging loss of
time, effort, and money. It is recommended, therefore, that the
first batch of soap be made a community affair for the entire class ;
or that the class be divided into groups, each group undertaking
the project.
If there is a school lunch-room or cafeteria, pupils may be able
to enlist the aid of the school kitchen in collecting waste fats for
the experiment. If not, pupils may each contribute a few ounces
of fat from their home kitchens and may divide the expense of
PROJECTS 579
borax and potash. Experiments in soap-making on a very small
scale are somewhat difficult to perform. It will be found easier
to produce soap from five pounds of fat than from five ounces.1
Follow the directions carefully and patiently :
Into a six-quart iron or heavily enameled vessel put 2 quarts of
water and heat it to boiling. Remove from the stove and dissolve
1 can of Babbitt's potash in the hot water.
In a third quart of hot water, dissolve one half pound of borax.
Pour the borax solution into the potash solution and set the
mixture aside to cool.
Melt 5 pounds of fat and strain it through three layers of cheese-
cloth. Allow this fat to cool to a soft paste-like consistency.
The next step requires patience. Add the fat, a spoonful at
a time, to the potash-borax solution, and stir each spoonful into the
solution slowly and carefully. After the fat is all in, stir the mix-
ture slowly for fifteen minutes.
If at the end of this time the soap is not of a paste-like consistency,
let it stand, giving it an occasional slow stirring. Your success
may be immediate, or your patience may be taxed for a day or
more. Do not give up.
When the mixture has become pasty, pour it into a rectangular
pan lined with oil paper. As soon as it hardens, it may be cut into
bars. It should be allowed to dry out for several weeks before it is
used. This soap is of very good quality and may be used for toilet
purposes.
Coloring, Perfuming, and Molding. — It is recommended that the
pupil confine his first efforts to producing soap. After he has made
a batch or two, he may wish to try experiments with coloring and
perfuming. Coloring matter, such as eosin (a very small amount),
should be added after about ten minutes of stirring and before the
mixture begins to become jelly-like. A few drops of oil of lemon
or some other perfume may also be added at the same time.
After the soap has hardened, it may be remelted with a gentle
heat and poured into molds lined with oiled paper.
1 Collecting waste fats at home though tedious work is to be en-
couraged, as the soap made therefrom will repay the effort.
580 EVERYDAY SCIENCE
PROJECT XVI. — How to Remove Dents in Wood,
pages 64-67
A heavy blow of a hammer will leave a dent in wood. What
happens is that the molecules of the wood at this particular place
have been forced into smaller space; that is, the spaces between
them have been lessened (see p. 67 of this book). If the wood
had been as elastic as rubber, the molecules would have regained
their original positions immediately; but wood has not great
elasticity.
If now we can cause the wood to absorb enough heat and moisture,
the molecules will be driven back to their original relative positions.
Heat an iron very hot. Soak several thicknesses of soft brown paper
in hot water. Lay this pad of wet paper over the dent and cover
it with a double thickness of cloth soaked in hot water. Apply the
hot iron to the cloth just above the dent, and let it stand until the
cloth and paper are nearly dry. If the dent is deep, this process
may have to be repeated several times.
PROJECT XVII. — How a Boy Scout Makes Fire without Matches,
page 72
Five things are necessary to produce a rubbing-stick fire : a drill
or spindle, a fire-block or hearth, a hand-socket, a bow, and tinder.
FIGURE 5
In choosing wood for making the drill and fire-block, great care
must be exercised. The wood should be dry and long-seasoned,
but sound. Gummy and resinous woods should be avoided. A test
for good wood for this purpose is that the wood-dust ground off
shall h,e smooth to the touch, not gritty or sticky. Two of the
best and most widely distributed woods are cottonwood and willow.
Better even than these are the cedar, the cypress, or the tamarack,
if they can be had. If none of these is at hand, try soft maple, elm,
poplar, sycamore, or buckeye.
PROJECTS
581
Drill. — Out of a straight dry branch or piece of seasoned wood,
whittle a roughly rounded spindle, about 12 inches long, and not
more than f inch in diameter. Sharpen the two ends of the stick,
as shown in Figure 5.
Fire-block. — Take a piece of wood not more than 12 inches
long, 2 or 3 inches wide, and not more than f inch thick. On one
FIGURE 6
side of this board, well toward one end, cut a notch \ inch deep,
and bevel it slightly toward the under side of the board. About
£ inch, or less, from the tip of the notch make a little hollow or pit
in the board, as shown in Figure 6, A.
Hand-socket. — *• If nothing better is at hand, take a pine or
hemlock knot that will just fit comfortably into the palm of the
hand. Make a pit in the center of one of the
flat surfaces of the knot, about J inch in diam-
eter and | inch deep.
If you are going to practice fire-making on
camping trips, you will find it a great saving
of time to have a socket made for your per-
manent use. Take a solid block of wood 5 or 6 inches long,
If inches wide, and 1| inches thick. Set in the middle of one face
of this block a piece of soapstone or marble 1 inch square and about
| inch deep. In the center of this piece of stone make a small
smooth pit, f inch wide and f inch deep. Smooth and round the
opposite face of the block so that it will fit your palm comfortably
and can be grasped firmly. The socket is now ready for use (Fig-
ure 7). ?
Bow. — (a) For this, any slightly curved rigid branch or stick,
18 tc 24 inches long, may be used. Fasten a thong of buckskin,
FIGURE 7
582
EVERYDAY SCIENCE
belt-lacing, or of any pliable leather, about f inch wide, to the bow,
as shown in Figure 8. The thong should be just long enough so
FIGURE 8
that when it is given one turn around the drill it will be stretched
taut (Figure 9).
Tinder. — Any dry, finely divided material that readily bursts
into flame from a spark is called tinder. Shredded cedar bark,
a wad of dry grass,
crumpled dry leaves,
willow catkins, scraped
cedar or spruce wood
will serve admirably.
Any observing person
will be able to find
plenty of good tinder
in a forest.
In addition to this
tinder, which is used
to nurse the glowing
spark into flame, the
fire-maker should have
at hand a collection
of twigs, long-stemmed
dry grass, splinters,
slivers of dry bark,
etc., to be used as
kindling for the larger
fuel that is to follow.
To Make Fire. — Set the fire-block on firm ground or on flat
rocks or on any foundation where the block cari be kept from slip-
ping or joggling. Slip a thin chip under the notch of the hearth.
FIGURE 9. — TOOLS IN POSITION TO MAKE FIRE.
At A is shown a hole that has been bored in
producing fire.
PROJECTS 583
Turn the thong of the bow once around the drill. If the thong
is of the right length, it will now be taut. *
Set one point of the drill into the pit near the point of the notch
of the fire-block, fit the upper end into the hand-socket, and with
your left hand hold the drill perpendicular to the block. Anchor
the fire-block with your left foot, and steady your left hand by
resting your left wrist against your left shin. This is to enable
you to keep the drill steadily in an upright position (Figure 9) .
Now with the right hand draw the bow slowly and steadily back
and forth the full length of the thong, pressing lightly on the hand-
socket. Keep the bow horizontal, and do not touch the drill with
it as you saw back and forth. The twirling motion of the drill soon
makes it bite into the block, boring out powdered wood. When
it begins to smoke, put a little more pressure on the socket and drill
faster. When the dust comes out in a compact mass and the smoke
increases to a considerable volume, you probably have the spark.
Carefully lift the fire-block so as to leave the smoking powder
undisturbed on the chip. Gently fan this with your hand into a
bright glow. Then put a wad of tinder gently over the glowing
powder and blow until the tinder bursts into flame. Follow this
with the kindling and your fire is started.
N. B. If you are left-handed, you will probably reverse the
directions for employing the right and left hands.
PROJECT XVIII. — • How to Make Fire with Flint and Steel,
page 73
It is much easier to make fire with flint and steel than to pro-
duce a rubbing-stick fire. Flint and steel and even tinder fuse may
be bought of dealers in camping outfits. Many lighting devices
for pocket use are based on the principle of striking fire from flint
with steel.
But neither the flint and steel nor the tinder have to be pur-
chased. Any piece of steel and any piece of quartz or hornstone
or flint may be made to serve your purpose. If you want to be sure
of having "punk" that will be sure to catch the spark, soak pieces
584 EVERYDAY SCIENCE
of cotton wicking in a solution of saltpeter and dry them thoroughly.
Of the materials to be found in a forest nothing is better than dried
fungus growths of various sorts. Thoroughly dried puff-balls, or
the flat white fungus growths found on decaying tree-trunks, or
dried lichens or moss are among the best materials. Dust or very
fine shavings scraped from dry cedar bark, spruce, or pine will
catch the spark readily.
To obtain the spark, rest the flint on the "punk" and strike
downward with the steel along the edge of the flint so as to throw
the shower of sparks into the "punk."
When you have the spark in the "punk," nurse it into a glow
exactly as in the case of the rubbing-stick fire, transform the glowing
spark into flame with the aid of tinder, and add the kindling and
larger fuel gradually until your fire is established.
PROJECT XIX. — How to Operate a Fire-extinguisher,
pages 79 and 80
The principle of the fire-extinguisher which produces carbon
dioxide is carefully explained on pages 79 and 80 of the body of
the book. Every pupil of junior high school age ought to know
how to operate . one of the extinguishers without a moment's
hesitation.
Every modern fire-extinguisher has explicit directions for operat-
ing it printed on the metal container. These directions should be
followed to the letter. It is especially important that the ex-
tinguisher should be discharged occasionally so as to have the
machine always charged with fresh chemicals.
Build a small fire in the open, away from all buildings, and use
a fire-extinguisher to smother the fire. Remember that the pur-
pose oi these machines is to cover the fire with a blanket of carbon
dioxide gas. Play the spray from the machine over the whole fire
so as to cut off the oxygen from all burning material.
When you have extinguished the fire, refill the cylinder according
to directions, not neglecting to wash it out thoroughly before re-
filling. If you are at all in doubt as to whether you have refilled
PROJECTS 585
correctly, discharge the extinguisher again in a second experiment
with a small bonfire.
One of the machines that generates carbonic acid gas also pro-
duces a foam, the bubbles of which imprison the carbonic acid gas
and form a sort of foamy blanket that is especially effective in
extinguishing burning oils.
Another very commonly used extinguisher, which is compact
enough to be convenient for automobile use, is filled with a liquid
that contains carbon tetrachloride. When this liquid comes in
contact with heat, it is readily converted into a heavy gas which
smothers the fire just as carbon dioxide does. This machine is
operated like a simple hand-pump.
PROJECT XX. — How to Make a Fireless Cooker at Home,
page 91
A very satisfactory fireless cooker may be made at home at
relatively slight expense.
The Box or Container. — The outside of the box may be a tightly
built wooden box, an old trunk, a galvanized iron ash can, a large
lard tin or butter firkin.
A well-built conveniently sized box (Figure 10, A}, with a hinged
cover (Figure 10, #), fitted with a hasp lock is perhaps the most
satisfactory container, although the cooker incased in metal has
the advantage of being fireproof. If a box is to be used, its size
will depend on the size of the metal nest which holds the cooking
vessel (Figure 10, (7). If possible, the box and the nest should be
large enough to accommodate a six-quart cooking vessel (Figure
10, D) . There must be enough space in the container to allow for
at least four inches of packing material above, below, and all around
the metal nest.
Packing or Insulating Material. — For insulating material a
variety of substances may be used. Crumpled or shredded news-
paper, sawdust, cotton-seed hulls, ground cork (such as is used
in packing Malaga grapes), wool, Spanish moss, hay, straw, and
excelsior may be used satisfactorily (Figure 10, B).
586
EVERYDAY SCIENCE
H
It is safer to pack the container with some non-inflammable
material, such as asbestos. A cheap and easily obtained substitute
is small cinders sifted from soft coal ashes, which may be obtained
at the boiler house of any mill if soft coal is not used in your home.
(Cinders from hard
coal are not quite
so good but will
serve.) Experi-
ments with soft
coal cinders made
by home econom-
ics specialists for
the United States
Department of Ag-
riculture showed
that this material
is very nearly as
satisfactory for
packing as crum-
pled or shredded
paper.
The Metal Nest.
— The insulating
material is packed
Courtesy of U.S. Department of Agriculture.
FIGURE 10. — LONGITUDINAL SECTION THROUGH
FIRELESS COOKER
solidly into
container, as
the
will
Showing details of the construction: A, outside
container (wooden box, old trunk, etc.) ; B, packing
or insulating material (crumpled paper, cinders, etc.) ;
C, metal lining in nest ; D, cooking kettle ; E, soap- be described later,
stone plate, or other source of heat ; F, collar to cover go as |0 fi^ snugly
, -,
metal
insulating material ; G, pad or cushion for top ; , , ,
H, hinged cover of box or container. about the
nest (Figure 10, C}.
This nest should be of a trifle greater diameter than the cooking
vessel and deep enough to hold a hot brick or soapstone (Figure
10, E) under the cooking vessel. A galvanized iron bucket may
be used as a metal nest. Better still, a tinsmith can make a galvan-
ized iron can of the required size, with straight sides, a rolled rim,
and a flat cover (Figure 11, A and C).
PROJECTS
587
Flange or Collar to Cover Insulating Material. — Have the tinner
cut a sheet of galvanized iron exactly to fit the opening of the
container. It should fit so closely in length and breadth that
it will just slip into the container so as to cover the contents com-
pletely. In the center of this metal sheet cut a hole just large enough
to allow it to be slipped over the bottom of the metal nest and fitted
up snugly under the rolled rim as a collar for the metal nest (Figure
11, D). When the nest is
" C
put in place, the collar
(Figure 10, F) covers the
packing, and serves the
important purpose of keep-
ing it dry.
The Cooking Vessel. —
This should be durable and
free from seams and crev-
ices, which are hard to
clean. It should have
perpendicular sides. The
cover should be as nearly
•B
FIGURE 11.
A, metal nest, with rolled rim, B ; C, cover ;
D, detachable collar or flange-
flat as possible and should be provided with a deep rim extending
well down into the kettle to retain the steam. It is possible to buy
kettles made especially for use in fireless cookers ; these are provided
with covers which can be clamped on tightly.
Tinned iron kettles should not be used in a fireless cooker, for
although cheap they are likely to rust from the confined moisture.
Enameled ware kettles, with covers of the same material, are
satisfactory. Aluminum vessels do not rust, and they may be
purchased in shapes that are especially well adapted for use in fire-
less cookers.
To Pack the Box or Container. — Line the bottom of the box, and
the sides to within four inches of the top, with 10 or 12 sheets of
newspaper or wrapping paper, with several thicknesses of card-
board, or with sheet asbestos f inch thick. Use a few tacks to
hold the lining in place. Shred newspaper into bits and cover
the bottom of the box evenly and compactly with the shredded
588 EVERYDAY SCIENCE
paper to the depth of four inches. Cover this with one or two
thicknesses of sheet asbestos | inch thick. (If non-inflammable
packing material is used, this asbestos cover for the lower four
inches of packing is not needed.)
Wrap the metal nest with a sheet of the asbestos paper, and stand
it, without the collar, on top of the packing, in the center of the box.
Pack more shredded paper, or whatever insulating material is being
used, all around the nest as solidly as possible, until it reaches the
rim of the metal nest. The top of the packing material and the rim
of the nest should now be about four inches, or more, below the
cover of the box.
Carefully remove the metal nest, slip the galvanized iron collar
over the bottom' of it, and slide it up until it rests just under the
rolled rim of the nest. Cut a piece of sheet asbestos of the same
shape as the collar and fit it just under the collar. Now replace the
nest carefully, and the collar with the asbestos lining under it will
cover the packing completely.
Cushion or Pad. — A cushion or pad (Figure 10, G) must be pro-
vided to fill completely the space between the collar or flange and
the cover of the box. This should be made of some heavy goods,
such as denim, and stuffed with asbestos fiber, cotton, shredded
paper, or excelsior.
A heavy but very efficient pad may be made by tying or quilting
newspapers together that have been cut to fit the top space, and
covering this paper pad with denim. The pad should be exposed
to sun and air whenever it is not in use.
To Use the Cooker. — A fireless cooker is best suited to those foods
which require boiling, steaming, or long slow cooking in a moist
heat. The classes of food best adapted to the cooker are cereals,
soups, meats, vegetables, dried fruits, steamed breads, and puddings.
Less water is needed than when foods are cooked on the stove,
because there is practically no escape of moisture from the cooking
kettle.
To cook food, bring it to a boil on the stove, and at the same time
heat the brick or soapstone. Transfer the heated plate to the nestr
close the cooking kettle tightly, and place it on the heated plate
PROJECTS 589
in the nest. Cover the nest, lay on the pad, close the box, and
fasten the hasp. Allow the food to remain undisturbed in the cooker
for six or eight hours.
Selected recipes for preparing food to be cooked in the fireless
cooker may be found in Farmers' Bulletin No. 771, "Homemade
Fireless Cookers and Their Use."
Leave the cooker open when it is not in use.
PROJECT XXI. — How to Make a Cheap Ice Box, page 92
The fireless cooker described in Project XX may very readily
be used as an ice box for keeping milk (or any other food that may
be put in an inclosed vessel) at a low temperature. Simply put
the bottle of milk tightly sealed or corked into the middle of the
nest and pack ice solidly around it up to the neck of the bottle.
Close the lid and keep the box in as cool and shady a place as
possible.
A much better and safer plan, if you wish to continue the use of
the fireless cooker for an ice box, is to obtain a covered bucket tall
enough to hold a milk bottle and of a diameter that will allow about
an inch of air space all around between the bucket and the metal
nest. Pack the bottle in this with crushed ice, place the bucket in
the nest, and close up the box. The double advantage of this is
that the air space between the bucket and the metal nest gives
extra insulation against the heat, and the bucket may be more
easily taken out once a day, emptied of water, washed with soap
and water, and sunned.
If the milk, or other food, is cold when it is put into the cooler,
it will keep safely for 24 hours. If the food is warm, or the weather
is exceptionally hot, the food may require re-icing at the end of 12
hours. Much depends on the care you have exercised in construct-
ing your box. If ice is not obtainable, very cold well water is the
best substitute. Put the milk bottle or other closed container
into the bucket and fill the bucket almost to the top with cold
water. Change the water every twelve hours.
If you have not made a fireless cooker in accordance with the
590
EVERYDAY SCIENCE
specifications of Project XX, a still simpler contrivance is
suggested by the Chicago Department of Health. Obtain a covered
bucket tall enough and wide enough to hold two quart bottles of
milk. For a nest get a still larger bucket that will allow about an
inch of insulating air space all around between the nest and the
inside bucket.
To hold this, a covered box at least 14 inches square and 15 inches
tall will be needed. Hinge the cover, put a hasp on it, and cleat
FIGURE 12.
M, milk in sealed bottles, packed in ice in covered bucket ; S, sawdust
packing around nest ; C, hinged cover with newspapers cleated to it.
to the inside o'f the cover about fifty thicknesses of newspaper, so
trimmed that the cover will close tightly. Cover the bottom of
the box with three inches of sawdust, lay the nest in the center of
the sawdust area and pack sawdust to the top of the nest. A
vertical cross section of this box is shown in Figure 12. Use the
box as directed in the preceding paragraphs.
The principle that explains both the fireless cooker and the ice
box here described is that a non-conductor of heat is interposed
between substances of different temperatures, thus preventing
them from equalizing those temperatures.
N.B. If a tinned iron bucket is used, put a little soda into it each
day when the ice is packed. This will tend to prevent rusting.
PROJECTS
591
PROJECT XXII. — How to Make an Iceless Refrigerator, page 104
A very useful device for the home where ice is not easily obtain-
able is the iceless refrigerator (Figures 13 and 14). In farm homes
where large amounts of milk and butter are to be kept, it pays to
have a separate cooler for these
delicate foods, in order to keep
them from absorbing odors.
The following directions for
making such a cooler contain
suggestions taken from bulle-
tins of the United States De-
partment of Agriculture.
Make a stanch wooden frame
for a case 42 inches tall, with
the other dimensions 14 X 16
inches (Figure 13). Make a
solid floor and top for the case,
with matched boards if possible.
The solid top should be set
below the top of the frame-
work, so as to furnish an insert
to hold the tapering base of a
14X16 inch biscuit pan (Figure
13). Fit a full-length door-
frame to the case as in Figure 13,
and mount it on brass hinges.
Be sure that the door fits closely
enough to be fly-proof.
Shelves may be made of poul-
try netting on light wooden frames, as shown in Figure 13. These
shelves rest on side braces set in the frame at desired intervals.
Now cover the entire framework and door carefully with rustless
wire screening of the smallest mesh obtainable.
Provide a 17X18 shallow bread pan in which to stand the entire
case after it is finished.
Courtesy of U.S. Department of Agriculture.
FIGURE 13. — FRAMEWORK OF THE
ICELESS REFRIGERATOR.
592
EVERYDAY SCIENCE
Give the framework, screening, shelves, and top and bottom
pans two coats of flat white paint. Give plenty of time for drying
between coats. When the flat paint is thoroughly dry, apply two
coats of white enamel. Remember that the success of enameling
a surface depends largely on allow-
ing sufficient time for drying
between coats.
Before applying the second coat
of enamel, be sure that the first
coat has lost all trace of stickiness.
The amount of time necessary
between coats depends on the con-
dition of the atmosphere. It may
be several days before you can
apply the last coat. Remember
that you want a hard enamel sur-
face, and the only way to produce
it is to exercise enough patience
to allow thorough drying between
coats of paint and enamel, and a
final "thorough drying before the
cloth cover is attached to the
frame.
A covering of canton flannel,
Courtesy of U.S. Department of Agriculture, burlap, Or duck should be CUt and
hemmed to fit the case, as in Fig-
ure 14. If canton flannel is used,
have the smooth side out . About three yards of material are needed .
This covering should extend down to the very bottom of the case.
Button the cover around the top and bottom of the frame with
buggy hooks and eyes. Another way to button the cloth to the
frame is to sew large buttons firmly to heavy strips of cloth at
desired intervals, and then tack these strips to the edges where the
cover is to be buttoned. On the edges of the covering provide
buttonholes at intervals corresponding to intervals between buttons
on the strips.
FIGURE 14. — THE COMPLETED
ICELESS REFRIGERATOR.
PROJECTS 593
Arrange the covering so that the door may be opened without
unbuttoning the edges of the covering. In order to do this, the
cover on the front of the case must be buttoned to the top and
bottom and latch panel of the door, as shown in Figure 14. Another
row of buttons fastens the other vertical edge of the covering to
the framework at the opening of the door. Make sure that the
hems on these vertical edges are extended far enough to cover the
crack between the frame and the closed door.
Sew to the top edge of each side of the covering a double strip
of the same kind of cloth. Make these strips long enough to extend
about 3 inches into the biscuit pan on top of the case, and taper
these strips to a width of 8 inches.
Keep the upper pan filled with water. The strips of cloth serve
as wicks to supply the sides of the covering with moisture (Experi-
ment 97, p. 325). The lower pan is to catch the drippings from
the covering. A small amount of water in the lower pan also serves
the excellent purpose of keeping ants and other insects from the
refrigerator. The only inconvenience about the operation of the
refrigerator is that the wicks attached to the door must be wrung
dry whenever it is opened.
Put the refrigerator in a shady place where the air circulates
freely. On dry hot days a temperature as low as 50° F. may be ob-
tained in one of these coolers. When the air is full of moisture,
the refrigerator will not work so well. Explain this. On such days
more water will drip into the lower pan.
PROJECT XXIII. — How to Make a Substitute for a Vacuum Bottle,
page 92
A very serviceable substitute for a vacuum bottle may be made
of a three-pound coffee-tin, a small amount of asbestos insulating
cement (such as is used to cover steam boilers and steam pipes),
a yard of cheesecloth, and a bit of flour or library paste, two or
three old newspapers, and a Ball-Mason quart jar (Figure 15).
A Ball-Mason quart jar measures 7 inches in height and 3 inches
in diameter at the base. An ordinary 3-pound coffee-tin is about
594
EVERYDAY SCIENCE
B
m
-c
2 inches greater in diameter and a little over 2 inches greater in
height. This tin serves as the outside container. If such a tin can-
not be had, procure a covered tin bucket of as great, or greater,
dimensions.
Mix enough water with the asbestos insulating cement to make
a plastic paste. Cover the bottom of the tin with an inch of this
paste (A] . Now mold up a wall of
asbestos (TFTF) of even thickness,
so as to form a well or nest 7 inches
deep and scant 4 inches in diam-
eter.
When the asbestos cement is dry,
line the well and cover the top of
the asbestos wall with cheesecloth.
This may be pasted on with flour
paste, rice paste, library paste, or
paper-hanger's paste. The latter
may be bought in small cartons at
any paint store.
When the jar (B) is placed in the
well, the top of the jar should be
FIGURE 15. — CROSS SECTION OF even with the top of the asbestos
INSULATED BOTTLE. ^ and there ghould be an Qpen
insuialLT^ttot oftn! ^ °f a ^ ™* ^ «» ™*
WW, asbestos wall ; P, insulat- below the cover of the can. To fill
ing pad; B, Ball-Mason jar; this space, make a newspaper pad.
C, cover for tin. /->».• i • /•
Cut circular pieces of newspaper to
fit the space, until you have enough to make a pad of sufficient
thickness to fill the space (P). Quilt them together and cover the
pad with denim.
An insulated jar made in this way will keep liquids hot or cold
for 10 or 12 hours. A pint jar may be insulated in a smaller con-
tainer, if preferred.
There are several reasons why a Ball-Mason jar is superior to
an ordinary bottle in the device described : it may be tightly
sealed; it is less likely to break when filled with hot liquids; it
PROJECTS 595
has a large mouth and may be easily washed and sterilized ; if it
breaks, a duplicate may easily be had.
An insulated bottle may be made by using a round cardboard
cereal carton for an outside container, newspaper for nest and pad,
and an ordinary wide-mouthed bottle with a tight cork for a liquid
container. Before pouring hot liquid into such a bottle, be sure
to heat the bottle by submerging it in cold water and bringing the
water to a boil (pp. 65 and 66) .
PROJECT XXIV. — How to Humidify Indoor Air in Winter,
page 107
The air in kitchens and bathrooms is generally plentifully supplied
with moisture. Other heated rooms ordinarily require the addition
of considerable moisture to the air.
In case a room is heated by stove, keep a pan of water continuously
on the stove.
Modern hot-air furnaces are furnished with water pans to supply
moisture to the air. If your furnace has no such moisture supply,
you will have to contrive a humidifier best suited to your needs.
Where floor registers are used, it is sometimes possible to set a pan
just under the grating and keep it filled with water. If this cannot
be done, it may be necessary to adapt the principle illustrated in
Figure 53 of the body of the book to a humidifier, which may
be put in some inconspicuous place in the room. Of course, the
nearer it can stand to the warm air draft, the more rapidly the water
will evaporate.
For rooms heated by steam or hot water, have a tinsmith make a
galvanized iron water can of the general shape indicated in Figure
16. The length, breadth, and thickness of the can will depend on
the amount of space available between the wall and the radiator.
At most it need not have a capacity of more than 2 gallons.
On one of the broad faces of the can solder. two No. 10 galvanized
iron wires, as shown in Figure 16, A A. Curve the ends of these
wires so as to hang them over the connecting rod of the radiator
as means of support. The distance between the wires must be such
596
EVERYDAY SCIENCE
that the weight of the can will be well balanced and each wire will
fall between two coils of the radiator.
Bend two No. 15 galvanized iron wires, or a strip of galvanized
iron 1| inches wide, as indicated in Figure 16, BB. These should
be long enough to
have the ends se-
curely soldered to
the narrow sides of
the can and to ex-
tend at least 6
inches above the
mouth of the can.
Fill the can with
water. Over the
rack (BB) hang a
double thickness
of canton flannel,
rough side out, with
the ends of the cloth
extending down into
the water to the
bottom of the can.
Suspend the can by
the curved wires to
the rear of the radi-
ator. The canton
flannel will absorb
the water from the
this
FIGURE 16.
can (see in
HUMIDIFIER FOR STEAM OR HOT connection Project
WATER RADIATOR. VVTT 111
XXII and look up
Experiment 97, p. 325), and the heat from the radiator will cause
rapid evaporation from the cloth wicking as well as from the
surface of the water in the can. Be sure to keep the can sup-
plied constantly with water. It will probably need attention at
least once a day.
PROJECTS 597
PROJECT XXV. — How to Operate a Refrigerator, page 111
In operating a refrigerator, there are four things to be kept
constantly in mind : it should have a steady temperature of 50° F.,
or less ; it must have a steady circulation of air, as shown in Figure
58 of the body "of the book; it must remain dry; it must be kept
spotlessly clean.
Low Temperature. — The low temperature of a refrigerator does
not necessarily destroy germs; it prevents their multiplying. If
food is in good condition when it is put in an efficient refrigerator,
it will remain in good condition. Before you buy a refrigerator, be
sure that it will maintain a sufficiently low temperature. If the
walls are properly insulated in the first place, the joints tight and
secure, and the doors tight-fitting and proof against warping, the
refrigerator will remain efficient for years.
To maintain low temperature: (1) Keep t the ice compartment
full of ice. Incidentally it is cheaper to do this than to maintain a
low supply. (2) Keep drinking water in a covered jar, instead
of opening the ice compartment frequently to chip off ice. (3) Do
not leave any refrigerator door open a second longer than necessary.
If you are removing food that is to be replaced in a few seconds,
close the door in the meantime.
Test the temperature of your refrigerator occasionally with a
thermometer. Leave the thermometer on each shelf in succession
for several hours. If the temperature is much above 50° F.,
examine carefully the joints, doors, and locks for faulty insulation.
Also see that the drain pipe is clean, and that nothing is interfering
with the circulation of the refrigerator. If nothing can be done to
keep the temperature low in your refrigerator, the safest and cheap-
est plan is to buy a new one. An epidemic of intestinal disease in
a well-known New York hospital a few years ago was traced to in-
efficient refrigerators.
Air Circulation. - — The air circulation explained and illustrated on
page 111 of this book is of vital importance. It keeps the in-
terior of the refrigerator at a fairly even temperature and helps
to keep it dry. Moreover, the circulating air collects the odors
598 EVERYDAY SCIENCE
and impurities and deposits them on the ice, whence they are
carried out by the melting ice through the drain pipe.
It follows, therefore, that delicacies, such as milk, cream, and
butter, should be put where the air fresh from the ice strikes them.
Meats and other such foods should come next. Vegetables, fruit,
cheese, fish, or any other foods that emit strong odors, should be
last in the circulatory system, so that the odors will be deposited on
the ice without tainting the more delicate foods. Even with this
arrangement, all highly odorous foods should be kept covered. Two
or three pieces of charcoal scattered through the refrigerator and
changed two or three times a month will help to absorb odors.
Large cafes have a separate refrigerator for each kind of food.
Do not stuff any shelf so full of foods as to impair the circulation
of air. As soon as the circulation of cold air is cut off, the tem-
perature of the refrigerator rises and moisture collects — two
conditions favorable for germ life.
Do not put any kind of food on the ice. It may impair the
circulation of air; but more important than this, it will gather
the odors and impurities that should be deposited on the ice.
Dryness. — Keep a little salt in an open dish in your refrigerator.
If this becomes damp or sticky, examine your refrigerator, as has
been suggested in the case of too high temperature. High tem-
perature and dampness generally go along together in a refrigerator.
Foods that you wish to keep moist or liquids that you wish to
keep from evaporating should be kept in tightly covered vessels.
Cleanliness. — Keep your refrigerator spotlessly clean. A porce-
lain enameled lining without joints or seams is most satisfactory
and safest. Don't allow a single drop of milk or speck of food to
remain on the shelves of your refrigerator, as breeding places for
germs. Keep the interior wiped out with water clean enough to
drink and a cloth or sponge clean enough to wash your face with.
Wipe all milk bottles, especially the caps and tops, with a clean
damp cloth before putting them into the refrigerator.
Once a week wash the interior with soap and water, wipe it out
with clear water afterwards, and dry it with a dish towel. Cleanse
the ice compartment and flush the drain with a strong solution of
PROJECTS
599
washing soda. After cleaning the refrigerator, replace the ice
and close the doors for a while before replacing the food. An
iced refrigerator dries much more quickly with the doors shut than
an un-iced refrigerator will dry with the doors open.
PROJECT XXVI. — How to Install Devices for Ventilating, pages
113-114 ^
Full instructions are given on pages 113-114 for making ventilat-
ing boards and screens. Measurements must depend on the size
of the window to be fitted.
In the case of cloth screens, the simplest way to get measure-
ments is simply to duplicate the frame of the summer screen and
then substitute muslin for wire screening.
PROJECT XXVII. — How to Siphon Cream from a Bottle of Milk,
page 119
To remove cream from a bottle of milk with a spoon or patent
cream dipper is a difficult and often a wasteful operation. The
cream or top milk may
be much more easily
and effectively removed
with a glass siphon.
Bend a piece of glass
tubing in the labora-
tory into the form of
a siphon (Figure 17).
Have the two arms of
the siphon close enough
together so that the
loop may be inserted in
a milk bottle as shown
in A, Figure 17.
To start the action of the siphon, dip the short arm of the siphon
into the cream, as in A, Figure 17, allowing the cream to run in and
fill the short arm, and the long arm to the depth of the short arm.
FIGURE 17.
600 EVERYDAY SCIENCE
Now hold the thumb over the opening of the long arm and place the
siphon in position, as in B, Figure 17.
Adjust the end of the short arm to whatever depth you wish,
place a receiving vessel under the opening of the long arm, and
remove your thumb from the opening of the long arm (Figure
170).
The siphon may be cleansed by running warm (not hot) soapy
water through it and rinsing with clear warm water.
PROJECT XXVIII. — How to Use the Most Common Solvents to
Remove Stains, page 140
Gasoline. — This is the most common solvent for sponging out
grease or oil stains. The most delicate fabrics may be soaked or
washed in it without risk. It should be used either out of doors or
in a well- ventilated room, without flame or smoldering spark of fire
or even a hot iron in the room. Never use a hot iron on goods
cleaned with gasoline until the fabric has been hung out long
enough for all the gasoline to evaporate.
After using gasoline, give the fumes plenty of time to pass out
before you light any sort of fire. Remember it is the volatile
vapor of gasoline that is so dangerously inflammable.
To remove grease from delicately colored fabrics, chloroform,
ether, and benzine are superior to gasoline because they evaporate
more rapidly and are less likely to leave a "ring." Chloroform and
ether are the best, but also the most expensive.
Probably the best fabric for applying stain solvents is clean cheese-
cloth.
Gasoline is sometimes mixed with carbon tetrachloride, another
effective solvent of grease, and sold under a trade name such as
"Carbona." The great advantage of such a mixture is that its
vapor is not inflammable.
Turpentine. — (1) Paint and Varnish. — Turpentine will remove
wet paint or varnish very easily from any fabric. If used with suffi-
cient patience and perseverance, it will also remove dry paint from
any fabric. After the paint is removed, sponge with chloroform
PROJECTS 601
to remove the turpentine. Alcohol followed by chloroform, or
chloroform alone, will often remove paint or varnish from delicate
fabrics.
(2) Tar or Wagon Grease. — Rub lard into the stain to soften it.
Wet with turpentine. Gently scrape off all loose particles with a
knife. Wet again and again with turpentine and continue to scrape
until all loose particles have been removed. Then sponge with
turpentine and rub gently with a clean cloth until the fabric is
dry. Sponging with chloroform will remove the turpentine and
restore the color if it is affected.
For such stains on white wash goods, rub lard on the stain, wet
with turpentine, and after several hours wash with soap and warm
water. On heavy goods use a brush.
(3) Vaseline. — If sponging with turpentine fails, try sponging
with ether.
(4) Hardened Paint Brushes. — (a) Soak for 24 hours in raw
linseed oil. Rinse in hot turpentine. Repeat, if necessary.
(6) Heat vinegar to the boiling point and allow the brushes to
stand in it.
(c) Soak the brushes in paint and varnish remover, which may
be bought at any paint store.
N. B. — Brushes should never be allowed to dry hard. They
should be kept suspended — never resting on the bristles — in raw
linseed oil. A good way to suspend brushes is to bore small holes
through the tips of the handles, thread them on a wire stretched be-
tween two nails and allow the brushes to be submerged in the oil to a
depth of at least \ inch above the ferrule or binding strap.
PROJECT XXIX. — How to Prevent Tea-kettle Scale, page 144
If a tea-kettle is given the daily attention that any other kitchen
utensil or cooking vessel receives, there will be no accumulation of
scale. Tea-kettle scale is unsightly but in no wise harmful. The
principal reason why it should not be allowed to accumulate, or
should be removed if it is allowed to accumulate, is that it causes
such a waste of fuel. This is not noticeable if the kettle is set all day
602 EVERYDAY SCIENCE
over a coal fire, but the waste is considerable if measured gas is
the fuel used. It has been estimated that certain kinds of scale
offer from twenty to fifty times the resistance to heat that is offered
by an equal thickness of wrought iron.
If the tea-kettle is washed daily, or even three times a week,
and scoured if necessary with Bon Ami or Old Dutch Cleanser,
scale will not accumulate.
Housekeepers who will not exercise this care, may put a piece of
limestone, rough marble, or oyster shell in the tea-kettle. Change
it for a fresh piece two or three times a month.
PROJECT XXX. — How to Remove Tea-kettle Scale, page 144
Heavy Iron Kettles. — To remove accumulated scale from a
heavy iron kettle, fill the kettle with cold water and add a heaping
tablespoonful of sal ammoniac. Bring this to a, boil and then
empty the kettle. Place the empty kettle over a flame until it is
very hot and the scale will peel off. Set the kettle aside and allow
it to cool slowly! Repeat if necessary. After the scale has been
removed and the kettle is cool, fill it with a strong solution of wash-
ing soda, boil, and rinse with clear hot water.
Aluminum Kettles. — In the case of an aluminum kettle, fill
with cold water, and add a heaping tablespoonful of oxalic acid
crystals. Boil the solution, let it stand all night, and boil again in
the morning. This will remove a thin scale, but the operation will
have to be repeated several times for a heavy scale. Afterwards
wash the kettle thoroughly with ordinary soap and warm water
and rinse with clear hot water to remove all trace of the poisonous
acid.
Concentrated nitric acid will remove the scale from aluminum
much more quickly than oxalic acid, without injuring the aluminum.
But it has to be handled so carefully that it is not recommended
for ordinary household use.
Strong alkalies dissolve aluminum. Never use them on that
metal for any purpose.
Enamel Kettles. — Scale does not tend to accumulate so rapidly
PROJECTS 603
on good enamel ware. Keep an enamel kettle clean by washing
it, or boiling it if necessary, frequently with a strong solution of
washing soda. Either oxalic acid or nitric acid will remove scale
from enamel ware without "eating" through the enamel, but any
strong acid will remove the high polish from the surface of enamel.
PROJECT XXXI. — How to Soften Hard Water for Domestic Use,
page 146
Water of temporary hardness does not offer a serious problem
because it can be softened by boiling. Permanently hard water
requires something more to soften it.
For Laundry Use. — Washing soda is the most common softener
for laundry purposes. The two mistakes commonly made in its use
must be guarded against : do not make too strong a solution ; and
be sure that the soda is thoroughly dissolved. A failure to observe
these cautions may result in injury to the clothes.
Dissolve 1 pound of washing soda in a quart of hot water. For
most hard waters, 2 tablespoonfuls of this solution will soften a
gallon of water. If the water is unusually hard, more of the solution
will be required.
For Delicate Fabrics. — Borax is much to be preferred to washing
soda as a water softener because it will do no injury either to the
hands or to delicate fabrics. It is so expensive, however, that it
cannot be used in great abundance. To soften water for washing
delicate fabrics, dissolve 1 tablespoonful of borax in a cup of hot
water. This will soften a gallon of water.
For Toilet Purposes. — (a) Borax used as suggested in the preced-
ing paragraph will soften water satisfactorily for toilet uses.
(6) The addition of the juice of one or two lemons to a bowl of
hard water softens it agreeably for washing or rinsing the hair.
PROJECT XXXII. — How to Read a Water-meter or Gas-meter Dial,
pages 200-206
Water is sometimes sold to the consumer at a flat rate by the
month or year. In such cities there is no direct measurement of
604
EVERYDAY SCIENCE
the amount of water a consumer uses. In other cities water is
sold at so much per 1000 gallons, and the quantity used by
each consumer is measured by a meter on the consumer's premises.
Water-meters are pretty accurate instruments. If they are out of
order, they are most likely to record less water than is actually used.
It is convenient to know how to read the dial of your water-
meter. If it is a direct-reading dial, no instruction is needed. Most
water-dials, however, are like the
dial shown in Figure 18, and re-
quire some explanation.
On this dial the unit of meas-
urement is the cubic foot. The
hands revolve about circles. The
numbering on each circle indicates
the direction the hand of that
circle travels. On the dial shown
in Figure 18, the hands in the
100,000, 1000, and 10 circles
travel contrary to the hands of a
clock . The alternate hands travel
in the direction of clock-hands.
The number on the outside of
FIGURE 18. — DIAL OF WATER- • •••
METER. 01 cubic feet recorded for one
complete revolution of the hand.
Each circle has 10 divisions ; each division thus indicates -fa of the
total for the circle. (In reading the dial, pay no attention to the
circle measuring 1 foot. It is used for test purposes, as will be
explained later.)
The reading of the dial in Figure 18 is as follows :
1st hand shows rV of 100,000, or 10,000 cu. ft.
2d hand shows TV of 10,000, or 1,000 cu. ft.
3d hand shows & of 1,000, or 800 cu. ft.
4th hand shows A of 100, or 60 cu. ft.
5th hand shows T7ff of 10, or 7 cu. ft.
PROJECTS 605
Caution. — Notice that when a hand is between two figures, the
lesser is read, just as in the case of the hour-hand of a clock. If the
hand is very near a figure, and you do not know whether it is just
short of the figure or just past the figure, the following circle will
guide you. For example a careless observer might read the 2d
circle 2000. If it were 2000, then the hand in the 3d circle would
have reached 0 or passed it. Since the hand in the 3d circle has not
quite reached 0, the 2d dial-hand is to be read 1000 instead of
2000. In other words, think of the dial hand which shows a doubt-
ful reading as the hour-hand of a clock, and the dial-hand of the
following circle as the minute-hand. If the "minute-hand" has
completed a revolution and points to 0 or beyond, read the figure
toward which the " hour-hand" is pointing. If the " minute-hand "
has not quite reached 0, read the lesser figure preceding the "hour-
hand."
It can be seen that a quick way to read the dial is to begin with
the 10 circle and put the figures down in reverse order. Thus, the
10 circle records units, the 100 circle tens, the 1000 circle hundreds,
etc.
Commercially, one cubic foot is equal to 7 gallons, and so if you
wish to reduce cubic feet to gallons, multiply by 7.
The dial cannot be set back to 0 after reading. The record
is continuous. To ascertain the amount of water used in June,
for example, you would have to subtract the reading taken on the
31st of May from the reading taken on the 30th of June. You can
also ascertain the amount of water used for any single purpose,
such as sprinkling the lawn, by taking the readings before and after
using the water.
If you suspect that water is being wasted through some leak,
close all outlets tight, and observe the circle on the dial marked
"one foot." If it continues to move, there is a leak somewhere
on your premises, since the meter can register only when water is
passing through it.
A gas-meter does not record any number of cubic feet smaller than
hundreds. Consequently, the last two circles on a water-meter,
recording tens and units, are missing on a gas-meter.
606
EVERYDAY SCIENCE
The reading on the gas-meter shown in Figure 19 is 79,500 cubic
feet. The hand in the first circle presents a fine example of a
doubtful reading. It looks as if it might be exactly 80,000 cubic
feet. But since the hand in the 2d circle has not quite reached
FEUT
FIGURE 19. — DIAL OF GAS-METER.
zero, the first hand must be read 7 and the second hand 9 — giving
79 instead of 80 thousand.
The circle marked "two feet" is for test purposes, as was ex-
plained in the case of the water-meter.
PROJECT XXXIII. — Learning Weather Lore That a Boy Scout or
Camp Fire Girl Ought to Know, Chapter VIII.
Careful observation of sky and clouds for centuries, of air condi-
tions, and of the behavior of birds, barnyard fowls, and insects,
has resulted in a wealth of weather maxims that are pretty reliable.
Of course there are many bits of superstition that pass as weather
lore that are utterly unreliable. The task for an observer is to
sort out weather wisdom from silly superstitions. The most useful
and interesting books for the amateur weather forecaster are :
"Official Handbook, Boy Scouts of America."
"Reading the Weather," T. M. Longstreth. Outing Publishing
Co.
PROJECTS 607
"American Boys' Book of Signs, Signals, and Symbols," Dan
Beard. J. B. Lippincott Co.
"The Wonder Book of the Atmosphere," E. J. Houston.
Frederick A. Stokes Co.
" Practical Hints for Amateur Forecasters," P. R. Jameson.
Taylor Instrument Companies, Rochester.
"Weather Lore," Richard Inwards.
Study the folk-signs as well as the scientific signs of weather,
and report from time to time on the reliability of these signs.
Some of the most interesting and trustworthy signs are here
given :
Clouds and Sky. — White feathery wisps of clouds, like spreading
locks of hair, five or six miles above the earth are cirrus clouds.
When these appear suddenly, especially with the ends of the feathers
turned upwards, showing that they are falling, they indicate rain
to come within two or three days.
Very large low-hanging cumulus clouds (p. 103) indicate violent
storms in the immediate future. Such clouds seldom, if ever,
appear without an electric display.
When the blue sky is obscured by a delicate veil of white, indi-
cating a thin mist high overhead, rain is indicated. This veil is
known as a cirropallium.
Small, dark clouds scurrying along below the big clouds mean
rain.
When the sky is overcast with thick, gray clouds with lumpy
lower surfaces "like the inverted tops of a pan of buns," a steady
rain is indicated.
A pink sunrise indicates fair weather, as does a ruddy sunset.
But a ruddy sunrise or a pale yellow morning sky indicates rain.
A bright yellow morning sky indicates wind. A great deal of
weather wisdom is wrapped up in the old maxim :
"Evening red and morning gray
Will set the traveler on his way ;
But evening gray and morning red
Will bring down showers on his head."
608 EVERYDAY SCIENCE
Air Conditions. — When all kinds of odors are more noticeable, and
smoke descends instead of rising, there are good prospects of rain.
When no dew appears on the grass in the morning, rain is prob-
ably indicated.
If raindrops cling to leaves and twigs instead of drying quickly,
there will probably be more rain.
Birds and Fowls. — When migratory birds fly south earlier
than usual, an early cold winter is indicated.
When birds capable of long flights remain close to their nests,
wind and rain may be looked for.
Guinea fowls raise a great clamor before a rain.
Chickens roll and flutter in the dust before a rain. .
Crows fly low and wheel in great circles, cawing raucously, be-
fore a rain. But if they fly high in pairs, continued fair weather
may be expected.
Gulls circle around at great heights, emitting sharp cries as of
distress, before a rain.
Insects. — When spiders are seen crawling about more than
usual on walls, rain will soon come. This is a reliable sign, especially
in the months of winter rains.
When spiders spin new webs or cleanse their old ones, expect fair
weather. If they continue spinning during a rain, the rain will soon
be over.
When flies or gnats are more than ordinarily troublesome, ex-
pect rain or a drop of temperature.
When flies cling to the ceiling or disappear, rain is to be expected.
PROJECT XXXIV. — How to Remove Stains with Absorbents,
page 325
The principle of capillarity illustrated in Experiment 97 is applied
in the removal of stains from the most delicate garments. The
use of absorbents, such as blotting paper, French chalk (which is
ground soapstone), pipe clay, fuller's earth, common starch, and
melted tallow, is the simplest and least risky method of removing
grease, wax, blood, and scorch stains.
PROJECTS 609
Mention has been made in Projects IX and XXVIII of the use
of absorbents for the removal of ink and tar.
Grease. — (a) Cover the spot with fuller's earth, pipe clay, or
French chalk. Put a sheet of brown paper over this and press
with an iron that is warm but not hot enough to scorch or change
the color of goods.
(6) Mix a paste of French chalk or fuller's earth with water and
place it over the spot. Allow this to stand for several days and then
brush it off. Repeat if necessary.
(c) Put a piece of blotting paper under the spot and another
over it. • Put a warm iron on the top blotter. Keep changing the
blotters until all the grease has been absorbed. Sponge the spot
lightly with chloroform or ether if necessary.
Mud on Delicate Fabrics. — Wait until the mud dries. Gently
remove the loose particles. Make a paste of boiled starch. Lay
this over the stain and let it dry thoroughly. Brush it off carefully.
Repeat if necessary.
Scorch. — Make a paste of boiled starch and use as in case of
mud stain.
Blood. — Make a paste of common starch and warm water.
Apply it to the stain, allow it to dry thoroughly, and remove by
brushing gently.
Wax. — Gently remove all the wax possible from the surface
of the fabric with a penknife. Put a piece o£ brown paper under
the fabric. Cover the spot with a paste of starch or French chalk
and water. Lay another piece of brown paper over this and press
with a warm iron.
Machine Oil on Wash Goods. — Cover the spot with lard and
allow it to stand several hours. Wash in cold water with soap.
PROJECT XXXV. — How to Prepare Soil for Planting a Lawn,
pages 307-339
"The ideal soil for grasses best suited for lawn making is one
which is moderately moist and contains a considerable percentage
of clay — a soil which is somewhat retentive of moisture, but never
610 EVERYDAY SCIENCE
becomes excessively wet, and is inclined to be heavy and compact
rather than light, loose, and sandy. A strong clay loam or a sandy
loam underlaid by a clay subsoil is undoubtedly the nearest approach
to an ideal soil for a lawn ; it should, therefore, be the aim in es-
tablishing a lawn to approach as near as possible to one or the other
of these types of soil." Farmers' Bulletin No. 494, United States
Department of Agriculture.
Since one does not choose his home site for the quality of the
soil, it is clear that the soil in his yard may not be particularly
adapted to the raising of a good lawn. Since the lawn is intended
to be a permanent feature of the decoration of the place, it is
worth while to do all in one's power to improve the condition of
the soil.
If one builds a house and is compelled to haul in soil to fill and
grade his premises, he can at least exercise care not to have the
wrong kind of filling. If the soil is of excellent quality for lawn
purposes, it may be necessary for the owner to guard against having
the surface soil covered with subsoil taken from the excavation
for the foundation. Never allow soil that is full of bricks, tins,
boards, and other building debris to be dumped into your yard even
for subsoil. Such debris interferes both with drainage and with
upward capillary movement of water in dry weather.
It is almost impossible to grow a lawn of any sort in coarse, sandy
soil and it is very difficult to keep a lawn in good condition which
has a sandy subsoil. To make a satisfactory lawn where the soil
is sandy, add a top dressing of two or three inches of clay and work
it into the top four to six inches of sand. If a mixture of loam and
well-rotted manure can be laid over this to the depth of two or three
inches, a very satisfactory lawn soil will be obtained.
If the soil is too heavy or sour for lack of drainage, mix a layer of
sand or finely sifted ashes with the heavy soil, at the same time
adding humus to help fertilize as well as coarsen the soil.
Soil should be prepared for a lawn to the depth of 8 or 10 inches,
even though the surface seed bed need not be more than 1 inch in
depth. In spading a soil that is not deep, be careful not to turn
the subsoil over the surface soil. After the soil has been spaded,
PROJECTS 611
rake it fine, then compact it with a lawn roller, and finally loosen a
shallow surface bed for the reception of the seed.
Grass should be sowed in the late fall or the early spring. If
in the fall, September and October are the favorable months, de-
pending on the time when the fall rains set in. It is not well to do
the seeding during a dry period, unless one has at his disposal arti-
ficial means for watering. Fall planting has the advantage of allow-
ing a number of weeds to germinate and be killed by the frosts.
In localities where there is low winter temperature and little
snow, fall planting is not so successful. In such cases, the soil
should be prepared in the fall so as to allow the weed seed to ger-
minate and the young weeds to be killed. Then sow to grass seed
as soon as the soil can be broken up in the spring and in time to
get the benefit of the warm rains of early spring.
PROJECT XXXVI. — How to Prepare Soil for the Home Vegetable
or Flower Garden, pages 307-339
Loam is the best garden soil. It needs practically no modification
except the liberal addition of manure or artificial fertilizer. As
much as 600 pounds of manure a year may be applied with advan-
tage to a garden plot 20 feet square. Coarse manure should be
applied in the fall and thoroughly spaded under. In the spring,
fine, well-rotted manure should be applied just before spading.
This spring spading should work the soil to a depth of 10 or 12
inches. Carefully fine the soil as deep as possible with a rake and
smooth the surface for laying off into rows. Tomatoes, eggplants,
and other plants that require long growing seasons are materially
benefited by an application of well-rotted manure between rows
when the plants are about half-grown.
But the back-yard gardener, cannot choose his soil. He may have
light, sandy soil or heavy compact clay instead of the desirable
loam. Much can be done in either case to improve the garden
plot. The sandy soil needs the addition of abundant manure to en-
rich it and to make it more retentive of moisture. If a supply of
moisture is lacking, the best substitute is compost. Every gardener
612 EVERYDAY SCIENCE
should have a compost heap. This is a pile of waste organic mate-
rial prepared from six to twelve months before using on the garden.
In every household there is a waste of garden rubbish, leaves,
grass mowed from the lawn, parings and other unused portions of
fruits and vegetables. These should all be thrown on the compost
heap to decay. Be sure to avoid throwing diseased plants and
weeds bearing ripe seeds on the pile. But do not burn your leaves
in the fall. Bury them on the compost heap and let them rot for
fertilizer. The compost heap should be built in alternate layers
of vegetable refuse and earth. Every six or eight inches of organic
matter should be covered with an inch or so of soil. The burying
helps to rot the vegetable matter. You will find it convenient to
make the heap not more than six feet square and about four feet
high. It is easier to make the sides of a small pile, such as, this,
perpendicular and to keep the top flat for the reception and reten-
tion of moisture to aid in rotting. If this is forked over once or
twice in the late fall and again in the early spring, decay will be
hastened. In the spring, spread it on the garden plot like manure
and spade it under.
Heavy clay soil may need the addition of sifted ashes from which
all clinkers have been removed in order to loosen its texture. Soil
that has long been uncultivated or that has been devoted to lawn
is likely to be sour. The presence of plantain or sorrel generally
indicates sourness. Clay soil because of its compactness and poor
drainage is apt to be in this condition. To remedy this, a small
amount of some base to neutralize the acid is needed. Apply evenly
over the garden plot, when you are preparing the seed bed in the
spring, 1 pound of air-slaked lime, 2 pounds of ground limestone, or
2 pounds of unleached wood ashes 1 to every 30 square feet. Rake
this into the soil to the depth of 2 inches. Be sure to do this after
the spring fertilizer has been worked into the soil, not at the same
time. Liberal use of manure and compost helps to loosen clay soil
and to make it more workable.
1Wood ashes have notable manurial value because of potash salts
contained ; but lose most of this value if subjected to the action of water
(leached).
PROJECTS 613
PROJECT XXXVII. — How Boy Scouts and Other Campers May
Prevent Forest Fires, Forestry Rules, pages 339-346
Every camper should obtain a copy of the laws of his state re-
garding the conservation of forests. If a legal permit to build
a fire in forests is required of all campers, such a permit should be
secured by all means. The following is a copy of the notice posted
in forests by the United States Department of Agriculture. It
directs attention to United States laws on this subject, and gives
a few suggestions that should be heeded carefully.
Forest Fires
The great annual destruction of forests by fire is an injury
to all persons and industries. The welfare of every community
is dependent upon a cheap and plentiful supply of timber, and
a forest cover is the most effective means of preventing floods
and maintaining a regular flow of streams used for irrigation
and other useful purposes.
To prevent forest fires Congress passed the law approved -
May 5, 1900, which -
Forbids setting fire to the woods, and
Forbids leaving any fires unextinguished.
This law, for offenses against which officers of the Forest
Service can arrest without warrant, provides as a maximum
punishment —
A fine of $5000, or imprisonment for two years, or both, if
the fire is set maliciously, and
A fine of $1000, or imprisonment for one year, or both, if
fire results from carelessness.
It also provides that the money from such fines shall be
paid to the school fund of the county in which the offense is
committed.
The exercise of care with small fires is the best preventive of
large ones. Therefore all persons are requested —
614 EVERYDAY SCIENCE
1. Not to drop matches or burning tobacco where there is
inflammable material.
2. Not to build larger camp fires than are necessary.
3. Not to build fires in leaves, rotten wood, or other places
where they are likely to spread..
4. In windy weather and in dangerous places, to dig holes
or clear the ground to confine camp fires.
The fire may be confined in various ways. A circle of stones
may be built around the fire, with the draft provided on the side
away from the windward. Or, a pit may be dug, and the dirt from
the pit cast up in a semicircle to windward, with the opposite side
more shallow to provide for draft. If the wind is high, it is wise to
clear a space of fifteen or twenty feet> in diameter by removing all
inflammable material and leaving only the bare earth exposed. Al-
ways have several buckets of water at hand to be used in case of
accident.
5. To extinguish all fires completely before leaving them,
even for a short absence.
"A fire is never out," says Chief Forester H. S. Graves, "until
the last spark is extinguished. Often a log or snag will smolder
unnoticed after the flames have apparently been conquered, only
to break out afresh with a rising wind."
To prevent the re-kindling of a fire after it has apparently been
extinguished, pour water over it and soak all the ground around
within a radius of several feet. If water is not available, cover the
charred remains of the fire completely with earth.
6. Not to build fires against large or hollow logs, where
it is difficult to extinguish them.
7. Not to build fires to clear land without informing the
nearest officer of the Forest Service, so that he may assist in
controlling them.
PROJECT XXXVIII. — Garden Projects, pages 366-399
In a manual of this sort, it is not practicable to offer any single
garden project, since weather and soil conditions differ so widely
PROJECTS 615
in various regions. Soil conditions may vary greatly even in the
same community. ,
Among the best pamphlets on flower, fruit, and vegetable gar-
dening are those issued by certain wholesale dealers in seeds and
by the United States Department of Agriculture. A number of
books are listed below, with comments as to their nature and degree
of usefulness for beginners.
Vegetables. — "Home Vegetable Gardening," F. F. Rockwell.
J. C. Winston Co., 1911.
"The Home Garden," Eben E. Rexford. J. B. Lippincott Co.,
1909. These two books are very good guides for the amateur.
They deal with vegetable gardening and fruit gardening, furnish
useful hints as to the general planning of gardens.
"The Home Vegetable Garden," Adolph Kruhm. Orange Judd
Co. Treats of each vegetable separately. Designed for the eastern
section of the United States.
"Home Vegetable Gardening from A to Z," Adolph Kruhm.
Doubleday, Page and Co., 1918. The same type of book as the
preceding, but written with special reference to Pacific Coast con-
ditions.
"Farm Friends and Foes," C. M. Weed. D. C. Heath & Co.
"Home Gardening in the South," Farmers' Bulletin No. 934,
United States Department of Agriculture.
"The Farm Garden in the North," Farmers' Bulletin No.
937.
"The City and Suburban Vegetable Garden," Farmers' Bulletin
No. 936.
"Control of Diseases and Insect Enemies of the Home Vegetable
Garden," Farmers' Bulletin No. 856.
"Home Storage of Vegetables," Farmers' Bulletin No. 879.
Fruits. — "Growing Fruit for Home Use," Farmers' Bulletin
No. 1001.
"Making a Garden of Small Fruits," F. F. Rockwell. McBride,
Nast & Co., 1914.
"Home Vegetable Gardening " (Part III), F. F. Rockwell. J. C.
Winston Co., 1911.
616 EVERYDAY SCIENCE
"The Home Garden " (Chapters XIV to XVII), Eben E. Rex-
ford. J. B. Lippincott Co., 1909.
Flowers. — " A-B-C of Gardening," Eben E. Rexford. Harper and
Bros., 19.15. A very simple and useful book on flower culture.
"Yard and Garden," Tarkington Baker. Bobbs-Merrill Co.,
1908. On the care of lawn, flowers, vines, shrubs, and trees. A
good all-around book for the amateur.
"Manual of Gardening," L. H. Bailey. Macmillan Co., 1911.
A larger book than either of the two preceding. It treats of the
care of the lawn, ornamental plants, shrubs, and trees, and devotes
a chapter each to the growing of small fruits and of vegetables.
PROJECT XXXIX. — How to Raise Strawberries without Garden
Space, pages 366-399
It frequently happens in crowded sections of cities that there is
no space in yards or near-by vacant lots for any kind of gardening.
It is interesting and profitable, therefore, to see what can be done
with a flour-barrel — or any other tightly constructed barrel —
filled with rich, loamy soil, and placed on a sunlit balcony or in a
sunny corner of a paved court.
After the barrel has been filled with good rich soil thoroughly
mixed with well-rotted manure, draw circles about the barrel par-
allel to the top and about six inches apart, beginning with a circle
six inches below the mouth of the barrel. On the lines of these
circles bore one-inch holes in the barrel, six inches apart. The holes
of each succeeding circle should be bored just below the middle of
the spaces in the circle above.
In the soil on top and in the holes bored through the sides set
strawberry plants. The suggested arrangement of holes gives the
maximum of light and air to each of the plants growing from the
holes. Two such barrels can be made to supply a good sized family
with strawberries in season.
Remember to keep the barrel where it can get the sunlight and
be sure to keep it watered. Be sure not to keep it drenched. If
water keeps running through the soil in too great abundance and
PROJECTS 617
draining from the hole and from the bottom of the barrel, it will
not only wash the loam from the holes and expose the roots of plants,
but will also wash the fertility out of the soil.
For careful instructions as to how to raise strawberries, write the
United States Department of Agriculture for a copy of Farmers'
Bulletin No. 198.
PROJECT XL. — How to Irrigate a Small Garden, pages 366-399
Inexperienced gardeners frequently make the mistake, in dry
weather, of sprinkling the surface of the soil lightly and frequently.
This surface supply of water quickly evaporates. Moreover, this
method of watering tends to lure the roots toward the surface in-
stead of making them strike deep, as the roots of hardy plants
should strike, into the soil. It is better, either with garden or
lawn, to soak a portion of it at a time, possibly taking several days
to cover the whole plot, rather than to sprinkle the surface lightly
every day.
Where one does not enjoy the convenience of an unlimited water-
supply and a garden hose, but has to carry water in buckets to
the garden, a very satisfactory system of irrigation on a small
plot of ground can be established with the aid of large cans and
buckets taken from the tin can pile. Take one-half gallon or gal-
lon cans or even old galvanized iron buckets. Perforate the sides
with a hammer and a ten-penny nail. Sink the cans to the level
of the ground, about two or three feet apart, between rows of gar-
den stuff.
Fill the cans with water instead of sprinkling the surface of the
soil. A gallon of water furnished directly to the roots of plants in
this way will do more good than three gallons applied to the surface
of the soil.
PROJECT XLI. — How to Cold-pack a Vegetable — Tomatoes, page 440
Start with clean hands, clean utensils, and pure clean water.
Use only clean, sound fresh tomatoes. No fruit or vegetable
which is withered or unsound should ever be cold-packed. If
possible, use only vegetables picked on the day of canning.
618 EVERYDAY SCIENCE
Glass jars are much to be preferred to metal cans for home canning.
Soft, elastic rubbers of the best grade should be used. Never use
old or cheap rubbers. The best are the most economical.
After washing and rinsing the jars carefully, submerge them in
a vessel of cold water. Submerge the lids and rubbers in cold water
in a separate vessel. Heat the water in these vessels slowly and
allow it to boil for fifteen minutes. Allow the jars, rubbers, and
covers to remain in the hot water until you are ready to use them.
Do not touch the insides of jars or covers with your fingers in the
process of paqking. Sterilize in the same way all spoons, cups, and
other utensils used for packing the tomatoes.
Wash the tomatoes carefully in cold water.
Place them in a cheesecloth bag or dipping basket, and dip them
in boiling water. Allow them to remain for 1| minutes. A shorter
period of scalding may loosen the skins ; but unless sufficient time
is given for scalding, the tomatoes may shrink after packing.
Lift the bag or basket of tomatoes from the boiling water and
plunge them into cold water.
Slip off the skins ; and if you wish, remove the cores of the larger
tomatoes, though the removal of cores is not necessary.
Pack the tomatoes directly into the sterilized jars. Press them
down with a sterilized silver tablespoon, but do not crush them.
Do not add water. The jar may be filled, however, with the juice
of the soft or broken tomatoes.
Add a level teaspoonful of salt for each quart of tomatoes.
Now adjust the rubbers and covers but do not seal them. In the
case of jars of the Ball-Mason type, screw the cover on only as far
as you can easily screw it with your thumb and little finger. In
the case of jars of the " Economy" or vacuum sealing type, place
the cover on and clamp it down with the spring. In the case of
clamp top jars, put on the cover, lift the wire into place, but do
not shut down the clamp. This is to allow for the escape of steam
and expanded air during the process of sterilization.
Place in a clean wash boiler a false bottom of wood or metal
grating in order to keep the jars off the bottom of the boiler. Better
than this, wire cages may be bought at very moderate expense,
PROJECTS 619
which serve to keep the jars off the bottom of the boiler and furnish
handles for removing the jars from the boiling water at the end of
the process of sterilization.
Put cold or tepid water into the boiler to the depth of two or
three inches and place the boiler over thfe flame. Place the jars in
the boiler, and add enough cold or tepid water to cover the jars to
a depth of several inches, but not enough to allow the boiling water
to reach the covers of the jars.
Cover the boiler and allow the jars to remain in it for 22 minutes
after the water begins to boil.
At the end of 22 minutes of sterilization, remove the boiler from
over the fire, take the jars out immediately, and tighten the covers.
The clamp-type or the Ball-Mason jars may be inverted a few
minutes to test for leakage. The vacuum seal jars should not be
inverted. Let them stand until they are cool. If, when the jars
are cool, you can lift them from the table by holding to the covers
alone, they are probably free of leakage.
For information as to cold-packing other vegetables and as to
varying the time of sterilization for altitudes higher than 1000
feet above sea-level, write to the United States Department of
Agriculture for a copy of Farmers' Bulletin No. 839, " Home Canning
by the One-period Cold-pack Method."
For canning by the cold-pack method in high altitudes, the
pressure cooker is very desirable. The increased temperature
makes sterilization more certain and hastens the process.
PROJECT XLII. — How to Cold-pack Certain Berries with Sugar,
page 440
The following particular instructions apply to the cold-packing
of blackberries, blueberries, currants, dewberries, black raspberries,
and huckleberries, but not strawberries, red raspberries, or goose-
berries. For cold-packing other kinds of fruits, see Farmers'
Bulletin No. 839, United States Department of Agriculture.
Sterilize jars, covers, rubbers, and all utensils, as directed for
cold-packing tomatoes (Project XLI).
620 EVERYDAY SCIENCE
If possible, obtain berries picked on the day of canning. Cull,
stem, and place them in a clean strainer.
Prepare a medium thin sirup as follows : Into 3 quarts of cold
water put two quarts of sugar. When the water has boiled just
enough to dissolve all the sugar thoroughly but not enough to make
the solution sticky, you have a thin sirup. To make a medium thin
sirup, continue to boil until the solution begins to thicken and
becomes sticky when cooled on the finger tip or on a spoon.
Rinse the berries in the strainer by pouring cold water over them.
Pack directly from the strainer into hot jars with a spoon or ladle.
Do not crush the fruit.
Pour the hot sirup over the fruit until the jar is level full and
ready to overflow.
Place the rubbers and covers in position without sealing.
N. B. Pack each jar, cover the fruit in it with hot sirup, and adjust
the covers and rubbers, before you begin to pack the next jar.
The operation of sterilizing the packed fruit is exactly the same
as in sterilizing the packed tomatoes, except that the berries need
be left in the boiler only 16 minutes after the water has begun to boil.
Remove from the boiler, tighten the covers, and test for leakage.
Store in a dark closet to prevent bleaching. If you have no dark
closet, wrap the jars in newspapers.
PROJECT XLIII. — How to Cold-pack Fruit without Sugar, page 440
Many excellent housekeepers maintain that the flavor of the
fresh fruit is retained better by canning without sugar. In such
case, the sugar is added just before serving. For pie filling or salad
purposes, fruit cold-packed without sugar is superior to that cold-
packed in sirup.
It is almost essential, in canning fruit without sugar, that the
fruit be picked on the day of canning. Cull the fruit, stem, seed,
or core it, and clean it by placing it in a strainer and pouring cold
water over it.
The process of cold-packing without sugar differs from the process
of cold-packing with sugar only in two essentials :
PROJECTS 621
1. After the fruit has been packed into the jars, pour boiling
water, instead of hot sirup, over the fruit until the jar overflows.
2. Leave the packed fruit in the boiler for 30 minutes after the
water has begun to boil.
PROJECT XLIV. — How to Preserve Vegetables and Fruit by Drying,
page 440
For some city dwellers cold-packing is much to be preferred to
the process of drying. Unless you have an oversupply of vege-
tables and fruits in your own garden, and can thus obtain them
absolutely fresh and without extra cost, you will probably find it
neither economical nor satisfactory in other ways to experiment
with the drying of vegetables.
If, on the other hand, you have an oversupply of vegetables
in your own garden that you cannot sell, and you have no jars for
cold-packing, by all means dry your vegetables and fruits for winter
use or for winter markets. Many people much prefer the flavor
of certain dried fruits and vegetables to that of corresponding
canned products.
It is hardly profitable to undertake the drying of a fruit or vege-
table simply to satisfy one's curiosty. If, on the other hand, an
oversupply of garden produce makes drying a practical and
economical project, detailed instructions are needed for guidance.
Such instructions, differing for each vegetable and fruit, are given
in Farmers' Bulletin No. 984, "Farm and Home Drying of Fruits
and Vegetables," United States Department of Agriculture.
PROJECT XLV. — How to Store Eggs for Winter Use,
page 440
. Eggs are most abundant and cheapest in spring and early summer.
This is the time to store them for winter use. To obtain the most
satisfactory results, do not store any but perfectly fresh eggs.
Eggs are somewhat like milk; they get their taint not so much
from being in storage as from careless handling before they are
622 EVERYDAY SCIENCE
stored. They should be kept away from all musty odors and in
a cool place from the time they are laid until they are eaten.
The three successful methods of preserving eggs, aside from cold
storage, are to varnish them with vaseline, to submerge them in
lime water, and to submerge them in a' solution of water glass.
Of these three methods, the water glass solution is the most satis-
factory. It must not be expected that preserved eggs will be as
palatable as fresh eggs, but if they are packed fresh in a solution
of water glass that is not too alkaline, they will compare very
favorably with the eggs that are bought at your grocer's in winter.
For cooking purposes they are just as satisfactory as fresh eggs.
Water glass may be bought as a thick sirup. It should be used
in the proportions of 1 volume of water glass to 10 volumes of
water. Water glass that is too strongly alkaline will make eggs
bitter.
To Preserve 10 Dozen Eggs. — Boil 5 quarts of water and allow
it to cool. Add one pint of water glass. Put the solution in
earthenware crocks or wooden pails that can be covered tightly.
Be sure that the receptacles are clean and odorless, and be sure
that the eggs are wiped, but not washed, clean before putting them
in the solution. (Washing removes an outer protective coating
from the eggshell.) After the eggs have been put in the solution,
small end down, cover the receptacle and put it in a cool place.
If you boil eggs that have been preserved in water glass, run
a needle through the shell at the large end. This will prevent the
shell from breaking through expansion of the moisture and air inside.
PROJECT XLVI. — How to Distinguish Fresh from Stale Eggs,
page 440
(a) Fresh eggs have a slightly rough coating over the shell.
(6) Since an eggshell is porous, an egg loses in time part of its
liquid contents by evaporation. This causes the white and yolk
to shrink, and the emptied space to be filled with air or some other
gas. This air space is generally at the broad end of the egg, and
in a good egg should not be larger than a dime.
PROJECTS 623
To Test Eggs by Candling. — Roll a sheet of cardboard into a tube
or cylinder, large enough to fit down over a lamp chimney or
a candle. A large shoe box with the ends removed and the cover
fastened in place will serve as well. In the side of the tube or box
opposite the flame, cut a hole somewhat smaller in diameter than an
ordinary egg.
Place the tube over a candle, lamp, or incandescent lamp, so that
the light is visible through the hole in the side of the tube. Hold
each egg to the opening in the cardboard, broad end up, and observe
it against the light. In a good fresh egg, the air space is small,
the yolk appears clear and round in dim outline, and the white is
clear. If the air space is rather large and the yolk is darkened, the
egg is stale. If the contents of the egg appear dark or hazy, with
a black spot, the egg is unfit for food.
If one has much testing of this k;nd to do, it is better to secure
a candling chimney for a small sum at a poultry store.
(c) The loss of liquid content by evaporation makes an egg lighter,
and so it may be tested by its specific density (p. 150). Make a
solution of one quart of water with two tablespoonfuls of salt.
A fresh egg will sink in this solution. A very stale egg will float.
Eggs at stages between a very fresh and a very stale egg may float
at various depths.
PROJECT XLVII. — How to Dress a Minor Wound,
pages 444-445
No home, office, or school should be without a Red Cross First
Aid Kit.
Do not attempt home treatment for anything but scratches or
shallow cuts or punctures. In case of deep cuts, accompanied by
severe bleeding, call a doctor immediately. Pressure on the wound
with a pad of aseptic gauze will retard the flow of blood until the
doctor can arrive. Do not use your fingers or an unclean cloth for
this purpose.
If the blood comes in spurts, an artery has been cut. In this
event, pressure should be exerted, if possible, on the supply artery
624 EVERYDAY SCIENCE
between the wound and the heart. The artery can often be located
by its pulsations. In case of a severed artery in leg or arm, let the
patient lie on his back and elevate the wounded leg or arm. An
elastic band, a pair of elastic suspenders, or a tightly wrapped
bandage applied between the wound and the heart will often serve
to stop the bleeding in 15 or 20 minutes.
In very severe cases, a tourniquet may be used. To make
a tourniquet, knot a strong handkerchief or cloth about the arm
or leg above the wound, place the knot over the supply artery,
and use a stick to twist the bandage as tight as necessary. Such
a bandage should not be left on more than 20 minutes. If the
doctor has not arrived in that time, exert pressure with a pad over
the wound itself for about five minutes and then replace the tour-
niquet.
In case of deep punctures, sujch as are made by nails, long splinters,
etc., have them cleaned and disinfected immediately by a doctor
to avoid danger of lockjaw or blood poisoning.
Never neglect minor incisions, scratches, or punctures. See
first that all foreign matter is removed from the wound and from
the surface around it. This should be done with a piece of aseptic
gauze and carbolic acid solution (1 teaspoonful of carbolic acid or
lysol to a pint of water), boric acid, bichloride of mercury solution,
turpentine, or grain alcohol. See that the antiseptic solution
reaches every part of the wound.
If there is tendency to bleeding, bandage the wound firmly with
aseptic gauze. A bandage is also useful to keep the wound from
coming in contact with infected surfaces. If the wound is where
there is little if any danger of such infection by contact, do not be
afraid to leave it open to light and air. This is infinitely better
anyhow than binding it with a cloth that is not clean or closing it
up with unclean court plaster.
Quick closing of the surface of a wound is not desirable. The
healing should be "from the inside out." If inflammation and
soreness persist, it will frequently be found that the wound needs
to be reopened with a sharp instrument that has been disinfected
by dipping it in alcohol or carbolic acid. When the wound has
PROJECTS 625
been opened, cleanse it again with carbolic acid solution, bichloride
of mercury solution, turpentine, or grain alcohol.
Do not attempt to reopen or cleanse deep wounds. That is
a doctor's work.
Caution. — Do not depend on ordinary peroxide of hydrogen for
disinfecting.
Two of the best and simplest books on first aid are :
" First Aid for Boys," Cole and Ernst. D. Appleton & Co.
" American Red Cross Abridged Text-Book on First Aid,"
P. Blakiston's Son & Co.
PROJECT XL VIII. — How to Disinfect a Room by Fumigation,
pages 444-445
The most important thing to be done at the outset is to seal the
room thoroughly so as to prevent the escape of gas until the process
of fumigation is completed. Close all windows and doors, except
the door provided for exit, but leave the windows unlocked so that
they may be opened from the outside. The temperature of the
room should be at least 60° F. or higher. The higher the tem-
perature the better, provided there is no exposed flame in the
room.
Make a formaldehyde solution by dissolving 12 ounces of 40%
solution of formaldehyde in 1 gallon of water. Soak strips of paper
in this solution and paste 4 to 6 thicknesses of them with paper-
hanger's paste over all door, transom, and window cracks, over
stove-holes, keyholes, registers, or any other openings of any sort.
After the strips are in place, wet them thoroughly with a brush
dipped in the paste. Large openings may need more than a single
thickness of paper. To prevent the skin of the hands from roughen-
ing or peeling, grease the hands or put on rubber gloves before
handling the formaldehyde solution. The fumes from this small
amount of the solution may be disagreeable but they are not
dangerous.
Hang clothing, bed covers, and everything that cannot be dis-
infected by boiling, on lines stretched across the room. Stretch
626 EVERYDAY SCIENCE
shades and curtains to full length. Open long seams on pillows
and mattresses and set them on edge. Open closet doors, dresser
drawers, chests, and trunks. Open books and spread them out.
In short, make it possible for the fumes to reach every part of
everything in the room.
Now place an ordinary wood or fiber washtub in the center of
the room. In the middle of the tub put two bricks on edge as
a base for a large bucket.
Before proceeding to fumigate, moisten the air of the room
thoroughly by boiling water in the room, by dropping hot bricks
into warm water, or by using an atomizer. The first method is
the most effective. Remember that a moist atmosphere is essential
to effective fumigation. The cloudier the room becomes with
moisture the better.
When the room is ready, spread 10 ounces of potassium per-
manganate (the needle-like crystals, not the rhomboid crystals
nor the dust) evenly over the bottom of a 14-quart bucket having
rolled, not soldered, seams. Put enough boiling water into the tub
to reach almost but not quite to the top of the bricks. Put the
bucket on the bricks in the center of the tub. Pour into the bucket
24 ounces of formaldehyde solution. The reaction between the
potassium permanganate and the formaldehyde solution is very
rapid and formaldehyde is liberated in great quantities. Be sure,
therefore, that everything is in readiness for you to beat a hasty
retreat and to seal the door of exit, before you pour in the formalde-
hyde solution. Leave the room sealed for six hours.
Be careful in handling the potassium permanganate. It is likely
to stain anything with which it comes in contact. The effervescent
action is so violent when the formaldehyde solution is poured on
the potassium permanganate that the bucket must be fully as large
as indicated. If convenient, have it larger.
The amount of chemicals indicated is sufficient to fumigate
a room 12X12X10. If the room is larger, provide more tubs and
buckets. Do not increase the amount of the chemicals for
a single bucket. This process can be depended upon. Not all
the fumigating candles and advertised apparatus are so reliable.
PROJECTS 627
Even if candles approved by health authorities are used, it is best
to use twice as many of them as directed.
Fumigating with Sulphur Candles. — The preparation of the room
for fumigation is exactly the same as for fumigating with formalde-
hyde. For a room 12X12X10, six of the pound candles would be
needed, no matter what the directions accompanying the candles
may call for. Put them in pans on the table, not on the floor, in
the center of the room, fill the water jackets two thirds full, light
the candles, leave the room promptly, and seal the exit door. Leave
the room sealed for from 12 to 24 hours.
The advantage of sulphur fumigation over formaldehyde fumiga-
tion is that it kills all insects as well as germs and thus prevents
insects carrying the disease.
The disadvantage is that the fumes of sulphur tend to bleach
and otherwise to impair all kinds of' fabrics, and are apt to injure
brass, copper, steel, or gilt work.
NOTE. — An excellent gum for use in sealing the room with news-
paper strips is powdered gum tragacanth. Soak two teaspoonfuls
of powdered gum tragacanth in one pint of cold water for an hour.
Then place the vessel containing the mixture in a pan of boiling water
and stir until the gum is dissolved. This seals effectively, washes off
easily, and will not stain or discolor woodwork at all.
•
PROJECT XLIX. — How to Prevent Dampness in Cellars and
Dark Closets, page 444
Since dampness and darkness are favorable to the growth of
bacteria and molds, and furnish inviting conditions for waterbugs,
roaches, and other disagreeable insects, modern houses are built
as nearly damp-proof and as free from dark corners as possible.
In many old-fashioned or ill-constructed houses, there are damp
and dark closets and cellar-rooms. To the unpleasantness and
unhealthfulness of such corners is added the loss occasioned by
rust and mildew.
Permanent removal of these conditions by whatever building
alterations are necessary is the most satisfactory remedy, and
628 EVERYDAY SCIENCE
in the end it is the most economical. But if you do not own the
house, or for some other reason you find it impracticable to make
the necessary alterations, conditions may be greatly improved by
a simple expedient.
Place one or more earthenware bowls of quicklime in the closets
or cellar-rooms. The amount of quicklime will depend on the size
of the closet or room. Quicklime rapidly absorbs moisture from
the air (p. 141 of this book) and counteracts stale odors common
to such places. This drying, of the atmosphere lessens the
danger of rust and mildew. Moreover, the odor of quicklime
apparently repels insects and mice that are likely to congregate
in such places.
When the lime becomes air-slaked, substitute a fresh supply.
Do not throw the air-slaked lime away; you may find it useful
for your lawn or garden (p. '315 of this book; see also Project
XXXVI).
PROJECT L. — How to Pasteurize Milk at Home,
pages 446-447
Choose a covered pail large enough to hold the bottle or jar in
which the milk is contained. Obtain a pie tin that just about fits
inside the bottom of the pail. Perforate the pie tin and place it,
inverted, in the pail. On this false bottom set the bottle, or bottles,
of milk, tightly capped or plugged with absorbent cotton. If you
buy your milk in bulk rather than in bottle put it in a Ball-Mason
jar, sterilized as for canning vegetables (Project XLI). Adjust the
rubber, screw down the cap tightly, and put the jar into the pail.
Fill the pail with water enough to rise to the neck of the bottle but
not to reach the mouth of the bottle. The water should be as
warm as possible without being hot enough to break the bottle.
Now cover the pail, put it on the stove, and bring the water to
a boil. The minute the water begins to boil, not simmer, remove
the pail and its contents from the stove, set it in a place where
it will not lose heat rapidly, and cover it with a heavy cloth. Let
it so remain for thirty minutes. Then remove the milk bottle from
PROJECTS 629
the pail and cool it as rapidly as possible without breaking the
bottle. All possible speed in cooling the bottle is just as important
as the preliminary heating. As soon as the bottle is cool enough,
put it, still tightly capped, into the refrigerator.
In pasteurizing milk, it is well to raise its temperature to 150°
F. in order to destroy the dangerous bacteria, but not to exceed
160° so as to avoid scalding or boiling the milk. The method out-
lined above accomplishes this as well as it .can be accomplished
without special apparatus. It might be supposed that more
accurate results could be had by inserting a chemical thermometer
in the milk itself to test the temperature during the process of
sterilization.
But the best authorities do not recommend this procedure for
home pasteurization, because the hole for the insertion of the ther-
mometer prevents perfect sealing of the milk during pasteurization
and makes contamination possible through careless handling after-
wards. It must be remembered that pasteurization kills the
bacteria in milk, but it does not eliminate dirt or prevent milk
from being contaminated afterward through carelessness. It is
important that places where milk is kept should be spotlessly clean ;
refrigerators especially should be looked after in this regard.
Where milk is to be pasteurized regularly for infants, a home
should be provided with one of the commercial pasteurizers, such
as the Freeman or the Straus Home Pasteurizer. In these the milk
may be subjected to exactly the right temperature for the correct
length of time, and then cooled quickly. Moreover, the milk may
be pasteurized in the bottles from which the infant takes it. The
Straus Home Pasteurizer, invented by Nathan Straus, the great
crusader for pure, clean milk, is inexpensive, easy to manipulate, and
" fool-proof." Instructions for making and using such a pasteurizer,
if one cannot be bought in your community, are given in the fol-
lowing books :
"Disease in Milk; the Remedy Pasteurization," Lina G. Straus.
N. Y., 1913.
"The Milk Question," M. J. Rosenau. Houghton Mifflin Com-
pany, 1912.
630 EVERYDAY SCIENCE
PROJECT LI. — How to Test the Home Water-supply for
Organic Impurities, page 447
(a) In a clean porcelain dish boil one quart of the water to be
tested. Continue to boil it until it evaporates.
If what remains in the bottom of the vessel immediately after the
water is evaporated is white and powdery, there are probably only
harmless mineral substances in solution in the water-supply.
If what remains immediately after the water is evaporated is
partly white and partly yellowish or greenish, with gum-like stains
around the edge of the residue, the water contains organic impurities
of either vegetable or animal origin.
Continue to heat the residue. If the yellowish or greenish or
gum-like portions turn black, sputter, and burn away, giving out
an offensive smell like burning feathers, the organic matter is pretty
certainly of animal origin and is unwholesome if not positively
poisonous.
(6) Unless you live directly on the seacoast or in a region of
salt-bearing rocks, neither the surface nor the underground water-
supply should contain more than a minute trace of common salt.
Anything more than a trace of common salt probably has its origin
in vegetable or animal refuse.
To Test for Salt. — To a tumblerful of the water to be tested, add
20 drops of nitric acid, and a small crystal of nitrate of silver — or
5 drops of a solution of nitrate of silver. Stir with a clean strip of
glass. The normal amount of salt will be indicated by a faint
bluish-white cloudiness. If the water shows marked cloudiness
or a solid curdy substance, too much common salt is present.
The presence of both organic matter and considerable salt in-
dicates that the water is probably contaminated by sewage or
stable drainage. The source of pollution should be discovered and
removed without delay. In the meantime, none of the water
should be used for drinking or cooking without purifying it since
such water may contain bacteria dangerous to the health. If
there is the slightest doubt about the fitness of water for drinking
purposes, it should be treated as directed in Project LII.
PROJECTS 631
PROJECT LII. — How to Clarify and Purify Water for Home
Use, page 448
Water may be murky in appearance without being unwholesome ;
on the other hand it may be clear without being pure. But clear
water is at least inviting. If a water-filter is used to clarify water,
it should be thoroughly cleansed at least once a week — preferably
oftener. To remove heavy sediment, where a filter is not used,
water may be strained through a flannel bag. Small flannel bags
with running strings may be fastened on the faucets. These should
be changed daily. Wash the used bags with soap and water and
hang in the sun to dry.
Water that contains organic substances may be clarified with the
use of alum. The alum coagulates albuminous substances, much
as boiling coagulates the white of an egg. This coagulated albu-
men settles to the bottom and acts like a net in carrying down other
impurities with it.
A lump of alum suspended by a string and swung about in
a pitcher for a minute or so will clarify it.
A teaspoonful of powdered alum will clarify 4 gallons of water.
Stir the water vigorously before adding the alum. Allow the
impurities to settle and then draw the water in such a way as not
to disturb the sediment. The alum, if there is not too much used,
will settle with the sediment.
To purify contaminated water, boil it for 16 minutes. This
drives off the air and makes water taste flat. To restore the
sparkle, pour the water rapidly from one vessel to another several
times. This aerates the water. A few drops of lemon juice add
surprisingly to the palatability of boiled water.
PROJECT LIU. — How Boy Scouts Filter and Purify Water
for Drinking, page 448
The methods applied in the home purification of water may be
used by Boy Scouts in field or camp. Run no risks whatever with
the water you drink. If you are going for a day's tramp and are
632 EVERYDAY SCIENCE
doubtful of the purity of the water you may find, take a canteen
of pure water with you.
Chlorine is the substance most commonly used by city water
departments in the purification of contaminated water-supplies.
Chlorine tablets are sold for home use or for camping trips. Some
city health departments furnish them free or sell them at cost to
people who plan to spend their vacations camping. The tablets
may be used according to directions accompanying them to rid
water of all dangerous germ life. They are exceedingly con-
venient to have, especially when time or means is lacking for the
boiling of suspected water. All campers should be supplied with
them.
Water from ponds, lakes, or running stream in truly wild regions
is generally safe. If water is uncontaminated by animal refuse,
it will not cause disease, no matter how much decaying vegetation
there may be in it. Sometimes the murky water of ponds or even
swamps is purer than the clear water of running streams, which
may be polluted by careless campers upstream. The murky
water of ponds or swamps may be clarified by the digging of an
Indian well.
A few feet from the edge of the pond or swamp, dig a hole from
12 to 18 inches in diameter, with the bottom of the hole extending
6 inches below the water-level of the swamp or pond. Let the
water seep into it and then bail it out quickly. Repeat this process
at least three times. After the third or fourth bailing, the Indian
well will be filled with filtered water.
If you are at all in doubt as to the purity of the water, either
boil it or use the chlorine tablets as directed.
PROJECT LIV. — How to Exterminate the Mosquito, pages 452-
454 (Community Project)
This is a community project, except in rural districts where
houses are widely separated. But in the city or village it does no
good whatever to destroy the breeding places of mosquitoes on your
own premises if your neighbors provide favorable conditions for
PROJECTS , 633
them either on their own premises or on adjoining vacant lots.
In New Orleans, Havana, the Panama Canal Zone, and many other
places, intelligent and concerted effort has eliminated the mosquito
as an agent of disease. Any community may accomplish the same
thing.
In order to fight the mosquito intelligently, we must know some-
thing of the way the pest comes into the world. When one realizes
that one female mosquito lays from 75 to 300 eggs at a time and that
these eggs develop into full-grown mosquitoes in from 10 to 13 days,
one does not wonder at the clouds of mosquitoes that sometimes
infest low swampy places.
Mosquito eggs are laid at night or in the early morning on the
surface of stagnant water. Mosquitoes avoid running water or
fresh water that is frequently stirred. In about 24 hours in warm
weather — or somewhat longer if the temperature is not high —
the eggs hatch into the larva stage. The larva, or "wiggletail,"
which almost everyone has seen in stagnant pools or rain barrels,
spends most of its time, head downward, just under the surface of
the water. It keeps the tip of its tail (where the opening of its
breathing tube is located) almost constantly at the surface of the
water. In fact, the larva cannot live more than a minute or two if
it is unable to reach the surface to breathe. After seven days or more,
according to the temperature, the developing mosquito passes from
the larva to the pupa stage. After living in the water in the pupa
stage for three days or more, it finally emerges as a full-grown mos-
quito.
Mosquitoes do not fly far from the places where they are hatched ;
hence, if they can be kept from breeding near human habitations,
the problem of mosquito riddance is solved.
Drainage. — Since stagnant water furnishes breeding places for
mosquitoes, the first work to be done is to drain all unnecessary
ponds or pools. Very often valuable land may be reclaimed by
the very process of draining that rids a section of mosquitoes.
Kerosene. — Where it is impracticable to drain pools, puddles, or
marshes, the surface of the water may be covered with kerosene.
On small pools or tanks it is necessary only to pour the kerosene
634 EVERYDAY SCIENCE
on the surface of the water. It will spread in an even film over
the entire surface. On marshes or large ponds, where weeds and
intervening dams of mud prevent the film of oil from spreading
over the entire surface of the water, it is best to use a sprayer. In
either case, use about 1 pint for approximately every 20 square
feet of water surface.
This film of kerosene kills all eggs at the surface of the water,
suffocates the larva or "wigglers," by cutting off their air supply,
and destroys all adult female mosquitoes that try to lay their eggs
on the surface of the water.
It takes about a week or ten days for the oil to evaporate from
the surface of the water, and at least 10 days after that before a
new generation of mosquitoes can be hatched. It is a safe plan,
therefore, to apply kerosene to the surface of all stagnant pools
about twice a month. In covered tanks, cesspools, etc., one appli-
cation a month is sufficient, because evaporation does not take
place so rapidly from such unexposed places. In heavy soil, cow
tracks and other small depressions may hold water long enough to
hatch a generation of mosquitoes. After every rain, such de-
pressions should be drained or else sprayed with kerosene.
Fish. — Where pools are used for the watering of stock, kerosene
cannot be used, of course. In such cases, the remedy lies in stock-
ing the ponds with top minnows or sunfish. These fish feed on the
larva of the mosquito. If there are no other fish in the pond, the
top minnow may be used. If the pond is stocked with larger fish,
the sunfish, sometimes called "pumpkin-seed," is to be preferred
because it is able to protect itself by means of its rays against larger
fish. Do not neglect to drain cow tracks around such ponds, or
else spray them with kerosene often enough to prevent mosquitoes
breeding in them.
Screening. — Water tanks, rain barrels, cisterns, and other re-
ceptacles for water for the household , cannot be treated with kero-
sene. Careful screening of all the openings of these receptacles
is the only remedy. The only effective screening against mosqui-
toes is the 16-mesh screen — 16 wires to the inch. No one argues for
less than a 14-mesh screen, and most authorities insist on a 16-mesh.
PROJECTS 635
If your house is equipped with screens of larger mesh and you
are troubled with mosquitoes that squeeze in between the wires,
rub the screens every night before dark with a cloth moistened with
kerosene. If you dislike the odor of kerosene, try the more expen-
sive oil of pennyroyal.
Tin Cans as Breeding Places. — A single tin can may catch enough
water from a rain to breed a multitude of mosquitoes. Before tin
cans are thrown on the rubbish heap, punch them full of holes or
knock the bottoms out of them. Tin cans carelessly thrown on
vacant lots make a neighborhood look slovenly and furnish homes
for immense families of neighborhood mosquitoes.
The following Farmers' Bulletins dealing with the subject of
mosquitoes may be had on application to the United States De-
partment of Agriculture, Washington, D. C. :
"Some Facts about Malaria," Farmers' Bulletin No. 450.
"The Yellow Fever Mosquito," Farmers' Bulletin No. 547.
"Remedies and Preventives against Mosquitoes," Farmers' Bul-
letin No. 444.
PROJECT LV. — How to Fight the Fly, pages 454-455 (Commu-
nity Project)
Fighting the fly is not an individual project ; it is a community
project. If you live in a small town, you may be able to interest
various organizations in the project. If you live in a large city,
you may be able to wake up your neighborhood. You can do some-
thing and should do everything in your power on your own premises ;
but cooperation is necessary if the fly is to be conquered.
Boy Scouts, Neighborhood Improvement Clubs, Civic Leagues,
Women's Clubs, High School Science Clubs, Commercial Clubs,
Chambers of Commerce, and other organizations have succeeded
in making some communities almost flyless. The community must
be educated to the menace of the fly before anything worth while
can be accomplished, and this requires the combined effort of civic
clubs. Some day people will wonder that we tolerated such a men-
636 EVERYDAY SCIENCE
ace exactly as we wonder at the unsanitary living conditions com-
mon centuries ago.
The average life of a fly is about three weeks. Most of the
millions of flies that do not die of natural causes during the summer
succumb to fungous diseases in the fall or to the cold of early winter.
But in almost every house a few survive. They hide in all sorts of
warm crevices, where they pass the winter in a state of complete
rest. The number of flies that may be descended in one summer
from one wintered-over fly runs into the trillions ! The moral is :
clean and disinfect every crevice of your house in March and swat
the wintered-over fly.
Screen all porches, windows, and doors in fly time.
Make all vaults fly-proof with screening, and cover the contents
once a week with copperas or iron sulphate to disinfect them and
to prevent the development of fly maggots.
Keep all garbage covered tightly until it is disposed of. To kill
all flies in and around garbage pails, sprinkle formaldehyde solution
— 1 part formalin to 10 parts water — in and around the pails once
a week.
Make traps and set them near doors and other places where flies
congregate. Patterns and detailed instructions for making an
effective fly trap may be had by sending five cents in stamps to
the Agricultural Extension Department of the International Har-
vester Company, Chicago. See also Farmers' Bulletins Nos. 734
and 927.
All flies breed in filth. Ninety per cent of all flies breed in stable
filth ! This should be hauled away and spread as fertilizer at least
once a week. If this cannot be done, keep it in tightly covered
boxes or pits until it is removed. Farmers' Bulletin No. 851 gives
detailed instructions for the extermination by some means or other
of flies that breed in stable filth. See that ordinances are passed and
enforced against all people who maintain live stock in a community.
For organizations that wish to conduct a fly campaign, the fol-
lowing books and pamphlets will prove of great value :
"Farmers' Bulletin" No. 851. This treats of the life history of
the fly, of its carriage of disease, its natural enemies, control measures,
PROJECTS 637
preventive measures for communities and farms, and directions
for community campaigns.
"The House Fly," L. 0. Howard. Frederick A. Stokes Co., New
York.
" The Reduction of Domestic Flies," Edward H. Ross. J. B. Lip-
pincott Co., Philadelphia.
PROJECT LVI. — How to Make War on the Rat, page 454
(Community Project)
Among all mammals, the rat is the worst pest known to man.
Individual war against rats on one's own premises is more effective
than individual war against flies, but only united effort in com-
munities can achieve permanent results. The loss of approximately
150 millions of dollars a year from the depredations of rats, aside
from the menace of disease they offer, is too great a tax for the
United States to tolerate indefinitely.
The first thing to do on one's premises is to see that, by means
of steel, concrete, and wire netting, all construction is made rat-
proof. This applies not only to homes, but also to barns, granaries,
poultry-houses, drains, sewers, etc. The saving will more than pay
for the extra cost of construction.
Keep all garbage cans tightly covered, and leave no scraps of
food of any sort exposed on your premises as a lure to rats and mice.
Trapping is the safest method of dealing with rats that have
gained access to buildings, such as homes, stables, warehouses,
mills, factories, etc. The baited spring trap may occasionally
catch inexperienced young rats, but it seldom fools the wise old
ones. Rats are very wary, and they seem to recognize bait by its
position as well as by the odor of human hands. Of all traps for
the catching of rats, none is so satisfactory as the smallest "New-
house" game trap. Place unusual food — grain if the rats have
been feeding on meat ; meat if they have been feeding on grain —
where they can have easy access to it, and allow them to feed freely
on it for several days. Then set the spring traps in these places,
with the trigger very lightly caught.
638 EVERYDAY SCIENCE
Do not put anything under the "pan" of the trap, and do not
put any bait inside the circle of the open jaws of the trap. Sprinkle
food about the traps so that the rats will be likely to step on the
pans when they pick it up. Cover the trap with chaff, bran, or
earth and sprinkle a little oil of aniseed around the traps. Be sure
that the trap is so fastened that the rat may drag it around a few
feet. Do not set the traps in the same place twice in succession.
These traps set in rat runways along building walls, ditch walls,
or at the mouths of rat burrows, or on their trails to water will catch
many a rat. In fact persistent use of traps will eventually rid a
place of rats. But remember . that it frequently requires not one
but many traps, and more patience and shrewdness than the rats
themselves have. Trapping mice is merely a matter of baiting
and setting the traps, but trapping rats is a test of skill.
French cage traps can never be used with success without a period
of baiting. Put freshly fried bacon, cheese, grain, or any other
tempting bait into the trap every night for several nights and leave
the back door of the trap open. When the rats have become bold
about entering and eating, bait the trap as usual and close the back
door. After you have made your .catch, set the trap in another
place and repeat the process.
Poisons are not safe for use in buildings or on city premises.
Rats are too inconsiderate about choosing a place to die. Barium
carbonate, mixed with egg and made into a paste with meal or
breadcrumbs, is a cheap and effective poison. It is also about the
safest poison because in small quantities it is not dangerous to
domestic animals.
For fighting rats on farms, Farmers' Bulletin No. 896 offers a
wide range of sound advice. See also Bulletin No. 33, Biological
Survey, United States Department of Agriculture.
PROJECT LVII. — How to Read an Electric Meter and Compute
the Cost of Current, pages 486-487
In order to understand a few terms that are used in measuring
electrical energy, let us liken the invisible electric current to a stream
PROJECTS 639
of water. The electric stream may vary in size as does a stream
of water. We speak of a stream of water as running so many gallons
per second. The size of the electric current we measure in amperes.
For example, only a small stream of one-half ampere is required
to run an ordinary incandescent lamp of 16-candle power, but a
large stream of five amperes is necessary to run an electric iron.
It is in connection with the size of the stream of electricity in a
house that fuses serve the purpose of safety devices. For example,
suppose your electric company has a 15-ampere fuse on your din-
ing room circuit. Now suppose you are operating on this circuit
two 16-candle power incandescent lamps, each requiring one-half
ampere ; and a toaster and a chafing-dish, each requiring 5 amperes.
This makes a total of 11 amperes. If now you add a percolator, re-
quiring 5 amperes, all the devices on the circuit together would de-
mand a current of 16 amperes, and the overstrain would blow the
15-ampere fuse on that circuit.
The remedy is to put in a new 15-ampere fuse, and not to use so
many devices on the circuit at the same time. Or it may be that
the company will allow you a 20-ampere fuse on that circuit, so
that you may use all the devices at the same time. But do not use
fuses of larger amperage without the consent of your electric company,
because your wiring may not safely carry a larger stream. If the fuse
should be of larger amperage than the wiring would carry, an over-
load would burn out the wiring instead of the fuse. There must
always be a safe margin between the size of stream your wiring will
carry and the size of stream your fuses will withstand.
Water at the faucet is under a certain number of pounds of
pressure (p. 201). This pressure has nothing to do with the size of
the stream. For example, you may open the faucet only slightly
and get a very small stream of water or you may open it wide
and get a full stream. The pressure behind both streams is the
same. What corresponds to pressure in a stream of electricity is
measured in volts. The most common "pressure" or voltage for
a lighting circuit is 110 to 120 volts.
The power of a stream of water flowing from a faucet depends
on the size of the stream and the pressure behind it. The power
640 EVERYDAY SCIENCE
of an electric current depends on the size of the current (amperage),
and the "pressure," or voltage. This power is measured in watts.
The number of watts may be determined accurately for one kind
of current and approximately for the other by simply multiplying
the number of amperes by the number of volts. For example, an
electric iron using a current of 5 amperes under pressure of 110
volts requires 550 watts of electrical energy to keep it heated. If
this iron is used for an hour, we say that it consumes 550 watt-
hours of current.
But a watt-hour indicates so small an amount of current that
the commercial unit of measurement is the kilowatt-hour, 1000
watts for an hour's time. Another way of putting it is that 1 kilo-
watt-hour = 1000 watt-hours.
Your electric fixtures are marked with the number of amperes
and volts necessary to run them. The iron mentioned above would
KILOWATT HOURS
FIGURE 20. — DIAL OF A WATT-HOUR METER.
be marked "5 amperes, 110 volts." In an hour's time this would
consume 550 watt-hours of current, as has been shown. This is
iVirk, or .55, kilowatt-hour. If your company charges 10 i a kilo-
watt-hour, it costs you .55X$.10, or $.055, to operate your electric
iron for an hour.
An electric stove with all the switches open requires an electric
stream of about 20 amperes. On a 110-volt current such a stove
in full operation would consume in an hour 2200 watt-hours of
current. This is MH, or 2.2, kilowatt-hours. At 10 i a kilowatt-
hour, such an electric stove, with all the "burners" going, would
cost 2.2X$.10, or $.22 an hour.
PROJECTS 641
An incandescent lamp marked 40 watts indicates that it uses
40 watts of current per hour. A 40-watt incandescent lamp would
therefore burn 25 hours ( 1000 -r- 40) before it registered 1 kilowatt-
hour, or 10 ff worth of current.
Reading the electric meter, or watt-hour meter (as it is called)
is exactly the same as reading the water meter, except that the unit
is kilowatt-hours, and the 100,000 circle is missing. Beginning at
the right and reading to the left, the circles indicate units, tens,
hundreds, thousands. The dial in Figure 20 reads 538 kilowatt-
hours.
Notice that the hand in the tens circle is in a doubtful position.
It must be read 30 because the hand in the unit circle has not yet
reached 0. (See Caution, Project XXXII.)
PROJECT LVIII. — How to Attach Wires, to a Socket, page 488
Caution. If you wish to attach a socket to the wiring of your house,
be sure to open the switch at the fuse board, thus turning off the cur-
rent from your house wires.
First remove the shell from the cap of the socket (A, Figure 21).
If the shell is attached by screws or rivets, turn it to the left and
pull it off. If the socket is old, the screws in the cap may have
to be loosened. If the shell has a corrugated upper edge that springs
into the cap, it may be removed by pressing it firmly near the key
(the place is indicated on most shells by the word "Press ") and
pulling it out of the cap.
Notice that the cap and shell are completely lined with insulating
material. If the insulating material is missing or damaged, do
not use the socket ; it is dangerous.
Cut off the ends of the two wires even. Remove the insulation
from the ends of the wires just far enough back to allow bare wire
ends to fit under the attachment screws of the core (A, Figure 21).
To do this, cut through the braided cover and scrape off the in-
sulation around the wires. In removing this insulation, be very
careful not to cut the filaments of wire within.
When the insulation is removed, roll the exposed filaments of
642
EVERYDAY SCIENCE
wire between your thumb and forefinger into a compact strand
that will fit snugly under the screws of the core.
Slip the cap over the two wires, as in A, Figure 21. Loosen the
attachment screws on the core, bend a wire end around each of the
-2^: two screws in clockwise direction, and
fiijT tighten the screws again.
Replace the shell. If it is attached
to the cap by screws, slip the screws
into the grooves and turn the shell to
the risht- If & is the sPrins type of
shell, push the upper edge of it into
the cap until you hear it click.
If you succeed in taking a socket
apart and wiring it, you will have no
difficulty in taking almost any sort of
plug apart and attaching wires to it.
Just be careful to put the parts back
in the order in which you removed
them. Figure 21, B, shows one type of
attachment plug.
Two of the most interesting and practical books on electricity
for beginners are :
"The American Boys' Book of Electricity," Charles H. Seaver.
David McKay.
" Harpers' Electricity Book for Boys," Joseph H. Adams. Harper
& Bros.
PROJECT LIX. — How to Make the Acquaintance of Trees and Wild
Flowers (Independent Project)
Projects LIX and LX are independent projects, not specifically
connected with any particular portion of the text of this book.
But in a larger sense, they are very vitally related to the
entire book. One of the chief purposes of Everyday Science is
to encourage an interest in the great out-of-doors. No one can
PROJECTS 643
spend much time out of doors without having a desire to become
better acquainted with the birds, trees, and undergrowth. Unfor-
tunately, wild forest life is so scarce in most thickly settled regions,
that few boys and girls have the opportunity to make a study
of it.
Guidance for the study of outdoor life cannot be given except
in books devoted wholly to that purpose. As a general guide for
beginners in the study of the out-of-doors, probably no book excels
the "Official Handbook of the Boy Scouts of America " (200 Fifth
Avenue, New York). "The Book of Woodcraft," by Ernest
Thompson Seton (Doubleday, Page & Co.) is another book in
which boys and girls devoted to outdoor life can find a mine of
interesting and valuable information.
Among the best guides to the study of trees and wild flowers are
the following books :
"Field Book of American Trees and Shrubs," F. Schuyler
Mathews. G. P. Putnam's Sons. No other one book is as satis-
factory as this for the identification of trees and shrubs.
"Studies of Trees," J. J. Levison. John Wiley and Sons.
This is probably the most satisfactory all-around book for be-
ginners on the identification of common trees, choice of shade trees,
care of trees, and elementary forestry.
"The Tree Guide," Julia Ellen Rogers. Doubleday, Page & Co.
A convenient pocket-size guide that enables the forest rambler
to identify trees by their foliage.
" The Forester's Manual," Ernest Thompson Seton. Double-
day, Page & Co. A guide to the trees of Eastern North America,
with maps showing the distribution of each tree described.
."The Trees of California," Willis Linn Jepson. Cunningham,
Curtiss and Welch, San Francisco.
"Field Book of American Wild Flowers," F. Schuyler Mathews.
G. P. Putnam's Sons. This is the most satisfactory handbook for
the identification of wild flowers. Its abundance of illustrations
makes it particularly useful to the beginner or amateur.
"Wild Flowers Every Child Should Know," Frederic William
Stack. Doubleday, Page & Co. A valuable feature of this book
644 EVERYDAY SCIENCE
for the beginner is its arrangement of the most common wild flowers
according to color.
"Wild Flowers of the North American Mountains," Julia W.
Henshaw. Robert M. McBride Co. This is a beautiful guide to
the flowers of the Rockies.
"Field Book of Western Wild Flowers," Margaret Armstrong.
G. P. Putnam's Sons. A very satisfactory guide to the wild flowers
of the regions west of the Rockies.
"Flower Guide," Chester A. Reed. Doubleday, Page & Co. A
pocket-size guide illustrated in color for the forest rambler.
PROJECT LX. — How to Study Bird Life (Independent Project)
Three bulletins of the United States Department of Agriculture
make a very good introduction to the study of the common birds :
"Fifty Common Birds," Farmers' Bulletin No. 513 (15£).
"Bird Houses and How to Build Them," Farmers' Bulletin No.
609.
"The English Sparrow as a Pest," Farmers' Bulletin No. 493.
Among the most reliable and usable manuals for the identification
of North American birds are the following :
"What Bird Is That?" Frank M. Chapman. D. Appleton &
Co., 1920. This is the most usable handbook of birds for the United
States east of the Rocky Mountains. Every land bird in that section
is pictured in color. The color plates group the birds according to
season, and indicate the relative sizes of birds. The accompanying
text is simple but thoroughly adequate. This is not an expensive
book.
"Color Key to North American Birds," Frank M. Chapman.
D. Appleton & Co., 1912. The title indicates the character of this
book. It is a guide to bird study throughout the North American
continent.
" Birds of the Rockies," Leander S. Keyser. A. C. McClurg & Co.
" Birds of California," Irene Grosvenor Wheelock. A. C. McClurg
&Co.
PROJECTS 645
"Handbook of Birds of the Western United States," Florence
M. Bailey. Houghton Mifflin Co., 1917. This is a complete guide
for the great plains, the great basin, the Pacific slope, and the
lower Rio Grande valley.
Among the most interesting books about birds are the following :
" Bird Friends," Gilbert H. Trafton. Houghton Mifflin Co., 1916.
This treats of the life of birds, their economic value, the enemies
of birds, the protection of birds, and methods of attracting them.
"Wild Bird Guests; How to Entertain Them," E. H. Baynes.
E. P. Button & Co., 1915.
"Homing with the Birds," Gene Stratton-Porter. Doubleday,
Page & Co., 1919.
"Methods of Attracting Birds," Gilbert H. Trafton. Houghton
Mifflin Co., 1910.
INDEX
References are to pages
Abdo'men 410
Acids 54-59,315
neutralization of . . . 55-59, 315
Adenoids 408
Adiaba'tic cooling and heating
124-125, 221
Agricultural soils ; see Soils
Air .... 96-134, 135, 141, 152,
209-226, 279-283, 311, 313-314
425, 443, 445, 483
adiabatic cooling and heating
of 124-125, 221
atmosphere (earth's envelope
of air) . . . 96-^97, 114, 115,
120, 132-134, 141, 152, 209-213,
279-280, 313-314
bacteria in . 98-99, 120-122, 443
composition of . 97-100, 132-133
compression of 123-125, 133-134
condensation of . . 104, 125-126
density of 116, 132
evaporation of moisture in
100-107, 133
expansion of ... 109, 123-125,
133-134
humidity of (absolute ; rela-
tive ; saturated) . 102-107, 133
hygrometer 103
liquid air 125
precipitation of moisture in
101-104
pressure of ... 110, 114-125,
127-134,210-211
saturation of moisture in
102-103, 104, 106, 112, 141
temperature 100-107,
109-110, 112, 125-128, 134
vacuum of 117-118
ventilation . . 99,112-114,133
Air — Continued
water vapor in .... 98-108,
112, 127, 133, 141
weight of .... 99, 108-110,
114-115, 129-131, 133
winds 110, 125, 215-226, 281-283
Air sacks 408
Air tubes 408
Alcohol . . 105, 140, 431-432, 457
abuses of 431-432
evaporation of 105
solvent, as 140
Alimentary canal .... 419-421
Alkali soils 332
Alkalies 55
Altitudes ....... 132, 134
Ammonia (a gas) 127
Angles of incidence and reflec-
tion 352
Angleworm ; see Earthworm
Animals 98-100,166,
311-319, 345, 366, 399-421, 423,
425-458, 522-553
classification :
by distribution :
amphibia 532
land animals . . 536-541
sea animals . . 166, 532-536
phosphorescence . 533-534
by structure :
invertebrates . 400-405, 423
insects 400-405
protozoa 400-401, 423, 452
breeders and car-
riers of disease 401, 452
see also Bacteria
shellfish 400
worms .... 317-319,
345, 401-402
EVERYDAY SCIENCE
References are to pages
Animals — Continued
vertebrates 400, 405-421, 423,
533-534
amphibia, birds, fish,
mammals, marsu-
pials, reptiles . . 400
man (a mammal) ; see
Man
dependents (parasites and
saprophytes) .... 397
food as energy-maker of . . 399,
423, 425-458
physical features of earth as
affecting .... 541-553
Anther (of flower) 387
Anti-cyclones 224
Antitoxins '.444
Arcturus, distance from ... 7
Arid lands 336-338
Arteries . . . 408-409,411-412
Artesian wells .... 197-198
Ash (in volcanic eruptions) . . 504
Asteroids (planetoids) ... 11
Vesta 11
Atmosphere ; see Air
At'olls 549
Atoms .... 50-51,58,500,501
electrons 500,501
Attraction ; see Earth; Elec-
tricity ; Magnetism ; Matter
Auditory nerve 418
Auricles (of heart) 412
Aurora Bo-re- al 'is (" Northern
Lights ") 360
Axis (of earth) . . 8-9, 25-31, 39
Axle, wheel and ; see Wheel and
axle
Bacteria . . . .98-99, 120-122, 303,
313-318, 361-362, 398-399,
401, 422, 435-449, 516-517
air, general purity of 120-122, 443
beneficent 435-438
classes and varieties of .'398-399
coal and peat developed by
516-517
decay caused by ... 303, 315
disease-breeding. . 401,441-444
fertilizers of soil, as 315, 317-318
Bacteria — Continued
forms of 438-439
harmful . 314,435-439,445-449
food spoiled by . . .445-449
health and sanitation vs.
120-122, 444-447
microbes 98,443
nitrogen prepared for life-
uses by ... 98-99, 317-318
number of . 314
propagation of . . 398-399, 422
ptomaines caused by ... 439
soils developed by . 314, 315-318
structure of 398
water polluted by ... 445-449
see also Fungi ; Molds ;
Protozoa; Yeasts
Barograph 130
Barometer . . 128-131, 134, 217
Bars, sand . . . .• 162, 258, 282
Basalt (ig'neous rock) . . . 253
Bases 54-59
alkalies 55
neutralization of . . 55, 58-59
Beach 161,251
Bees (honey-bees) . . . 403-405
Bell, A. G. (inventor of tele-
phone) 495
Beverages .... 431-432,456
Birds (vertebrate animals) . . 400
Blizzard (snow and wind storm) 228
Blood 410-411
corpuscles, red and white* . 411
haemoglobin 411
plasma 411
Boiling point . 100, 125-127, 134, 136
Boracic acid (a disinfectant) . 445
Borax (an aid in emulsifying) . 146
Brain 413,418
Bread 437-438
Breathing (respiration) . . 407-410
means of obtaining energy
from air 407
organs utilized in ... 407—408
Bridges, natural (of Utah and
Virginia) 198
Bubo'nic plague (protozoan
disease) 454
Bud (of plant) 377-378
INDEX
References are to pages
Budding (plant-propagation) . 377
Buds (of yeasts) 399
Buoyancy of water .... 148
Buttes (of plateaus) . . . 272, 276
Calms (of the tropics) . . . 221
Calorie (measure of energy and
heat) 84
specific heat 84
Ca'lyx (of flower) 387
Cambium layer (of stem) . 374, 377
Canals 192-196, 336
Candle power (standard meas-
ure of light intensity) . . . 350
Canons (of plateaus) .... 268
Capes 258
Capillaries (of circulatory sys-
tem) 409,411
Capillary action (of water) . 170, 327
Carbohydrates 383, 423, 425-428, 456
composition of 425
food properties of ... 425-428
found in cereals and grains ;
fruits ; vegetables . . 427
amount necessary daily
in diet 428
functions of 425-428
manufactured in green-plant
leaves . . . 383,423,425
chlorophyll 382,383
Carbolic acid (a disinfectant) 444-445
Carbon . . . 399-400,425,456,
488, 517-519
constituent of food .... 456
for incandescent lamp fila-
ments 488
in coal and peat .... 517-519
Carbon dioxide . 98-99, 133, 144, 280
constituent of air 98-99, 133, 280
exhaled by animals .... 98
inhaled by plants .... 99
solvent of limestone . . . 144
weathering agent of atmos-
phere 280
weight 99
source of danger in mines . 99
Caverns 198
Caves 198
Mammoth Cave 198
Cells (of plants) . . . . 371, 388
structure of 371
protoplasm in 371
Centri'fugal force .... 43-47
Centri'petal force ; see Gravita-
tion ; Gravity
Chemical action . . . . 72, 484
Chemical changes .... 53, 58
Chemical compounds . . . 54-59
Chemical energy . . . . 72-94, 358
Chloride of lime (a disinfectant) 445
Chlorophyll 382, 399, 400, 419, 425
Choke damp 99
Cinders (volcanic) .... 504-506
Circulation (of blood) 410-413, 423
Circumference (of earth) . 2, 23, 39
Cities .... 198-208,257-263,
444-456, 457, 546-548
locations of . 257-263, 546-548
industries due to ... 546-547
sanitation of ... 444-456, 457
water-supply systems of . 198-208
Clay (of ocean) 156
Clayey soils . 307, 310, 319-320,
345
Cleanliness 451-455
preventer of disease . . 451-455
care of wounds .... 451
protector of health . . . 452-455
destruction and preven-
tion of harmful bacteria
and protozoa- . . . 452-455
Cliffs 160
Climate . . 238-244,245-246
causes of 238
effects of day and night upon 243
effects of physical features
upon . . 238-243,245-246
of mountains . . 238-240,245
of water-bodies . . .241-243
effects of seasonal changes
upon 243-244, 245
see also Weather
Clouds. . . . 102,104,133-134,
210, 215, 244, 483
condensation of atmospheric
moisture 104
electricity in 483
weather vs 210,244
EVERYDAY SCIENCE
References are to pages
Coal .... 254-255,516^519
anthracite 255
bituminous 254
mining of 516-519
story of 516
Coast, depressed 549
Coastal plains . 257-264, 274, 546
see also Plains
Cold-storage . . 125, 127-128, 134
Color .... 356-361, 364, 390
in light 356
refraction through prism 356-358
spectrum .... 357-358
effects of atmospheric
conditions . . . 357-361
spectroscope . . . 358, 364
of flowers 390
Combustion 71,97-98
Comets 18,19
Halley's Comet 17
see also Sky
Commercial fertilizers ... 316
see also Fertilizers
Compass, mariner's 39, 476-478, 501
dip of needle 477-478
corrections for declination . 478
Conservation . . 37, 40, 63, 74-80,
90-94, 108, 112-114, 133, 184,
198-206, 209-210, 307-346,
362, 430-433, 438-441, 444-
457, 462, 473
of energy . . . 63-64, 462, 473
of food 440-441
legitimate preservation . 440
illegitimate preservation . 441
of forests 339-345
of fuels 74-77, 94
of health .... 99, 108, 112-
114, 133, 361-362, 430-433, 438-
439, 443-457
by cleanliness and sanita-
tion 444-457
disinfection 361-362, 443-445
sewage 449, 457
by proper food . . . 455-457
by ventilation . 99, 112-114, 133
of heat . . 77-80,90-94,209-210
fire-control 77-80
smoke abatement ... 94
Conservation — Continued
of light 37, 40, 362
daylight saving and light-
less nights . . .37, 40, 362
of soils . . . 184,315,322-323,
329-332, 334, 339-345
by adding and conserving
soil-water .... 322-323
by cultivation .... 329, 334
by draining . . . .331, 334
by dry farming . . . 329-330
alternate-year planting . 330
by fertilizing 334
by forestry 339-345
by irrigation .... 330-332
ditching 331
flooding 330-331
by levees 184
by neutralizing over-acida-
tion 315
by prevention of seepage . 331
by prevention of -water-
logging ...... 331
by reclamation ; see Rec-
lamation
see also Soils
of water-supply .... 198-206
Constellations 9-10, 19
see also Stars
Continental shelf .... 256-259
bars 258
dunes 258
islands 256
lagoons 259
life on 257
reefs 258
see also Land
Continents .... 248,256-276
Contraction (of gases, liquids,
solids) 65-69,94
Convection currents . . 88-90, 94
Coral islands 510,533
polyps 533
CorSl'la (of flower) .... 387
Coro'nas 17,360,365
Corpuscles (of blood) . 411, 430, 444
Crane 491
Craters (of volcanoes) . 503-506, 549
Crevasse' (of glaciers) . . . 289
INDEX
References are to pages
Cribs ^intakes) . . . , -. . 204
Crustaceans (shellfish) , . . 533
Cultivation ; see Soils
Currents . . 110-111,161-162,484
of air . . 110
of electricity 484
of water 161-162
Cylinder (of engine) .... 471
Darwin (on earthworm) . . . 319
Day and night . . 3, 12, 24-26, 33
variations in length of . . 24-26
Daylight saving .... 37, 40, 362
Decay 303, 315
necessary in soil-making . . 315
process of 303
see also Bacteria ; Molds ;
Protozoa ; Yeasts
Declination (of earth) . . . 478
Degrees (of latitude and longi-
tude) ........ 32
prime meridian (Greenwich) 32
Deltas 189-190,549
Density . 66, 94, 116, 132, 137, 150
of air ....... 116, 132
of water 137
Deposition and erosion 252, 278-282
Dew 104
Dew-point .... 102-104, 112
Diameter (of earth) ... 2, 23, 39
Diaphragm 409
Diastase 383
Diatoms 532
Dicotyledons 375-377
Digestion (of food) . . . 419-421
alimentary canal . . . 419-421
esoph'agus 420
intestines 420-421
mouth 420
stomach 420
Diphtheria (bacterial disease) . 442
Direction (four cardinal points) 20, 24
Disease . 361-362,401,441-449,
452-455, 457
antitoxins 444
bubonic plague 454
causes of 454
bacteria. . 401,441-449,457
protozo'a . 400, 452-455, 457
Disease — Continued
disinfection . 361-362, 443-445
malaria 452
• prevention of . 361-362, 442-447
" sleeping sickness " of Africa 452
source of 443-447
Texas fever 454
toxins 444
typhoid fever 442
wound-infection 442
yellow fever 452
see also Health and Sanitation
Disinfection . . 361-362,443-445
air 445
chloride of lime 445
drying 444
soap 445
solutions 444-445
sunlight 444-445
temperatures, extremes of . 444
water 445
see also Health and Sanitation
Ditching (in irrigation) . . . 331
Divides, land 175-176
Doldrums 221
Drainage ; see Soils
Drowned river valleys . . 188-189
Dry farming 329
Dunes, sand 258, 283
Dust (volcanic) 283-285
Dynamo . . . ....'.- . . . 497
Ear (organ of hearing) 416-418, 423
auditory nerve 418
bones of 418
drum of 418
Earth (a planet) .... 20-41
air and atmosphere ; see Air
axis and poles of . 8, 9, 25-31, 39
centrifugal and centripetal
forces . . 43-49,58,93,326
circumference of . . . . 2, 23, 39
climate 238-246
clouds and precipitation . .102,
104, 133-134, 210, 215, 244, 483
coasts ; see, below, shores
composition of 42
continents and islands . . . 248,
256-276, 540-541
EVERYDAY SCIENCE
References are to pages
Earth — Continued
crust of, see below, surface
cycles of change 303
day and night .. 3, 12, 24-26, 33
development of earth-science 20
diameter of 2, 23, 39
direction, cardinal points of 20, 24
distances to celestial bodies
from 2, 11, 23
elements 51
equator 30-31,39
gravity. . . .47-49,58,93,326
harbors. . 188-189,548-552,553
interior of ; see, below, surface
• lakes . . 171-174,177-178,185
magnetism . 37-39, 475-480, 501
meridians and parallels . .37
minerals and mining . 254-255,
515-520, 542-543
moon .... 2,4,14-17,19,
165, 210, 347-351
mountains and hills 22, 238-241,
248, 264-267, 541-543
ocean . . . 152-167,249-251,
256-258, 514, 531-535, 552
physical conditions of . . 522-553
plains . . . 257-259,268-276,
301-302,544-548,553
planetary movements . . 48-49
revolution of ... 26-31, 39-40
rivers . . . 176-208,546-548
rocks . . 252-255,275,279-281
rotation of .... 23-26, 39
seasons 27-31, 40
shape of 21-23,278
shores . . . 243-244,256-259,
540-541,549,
size of 1-2,22-23
soils .... 57,173,197-198,
209, 212-213, 284-286, 293-300,
307-346, 401-403, 535
storms 221-231
surface (crust) outside and
within . 166, 247-306, 502-553
tides 17-19,164-166
volume 2
waves . . . 157-161,251,514
weather . . 209-237, 244-2v5
winds . . . 216-231,244-245
Earthquakes 513-515
cause of 513-514
effects of 514-515
conflagrations (San Fran-
cisco) . 515
ocean-waves (Lisbon) . . 514
Earth-science .... 8-9,20-21
Earthworms .311-319,345,401-402
fertilizers of soils . 317-319, 402
structure of ... 345, 401-402
Ebb tide 164, 166
Eclipse 16,17,353
of earth's moon 17
of Jupiter's moons . . . . 353
of sun ' . 353
Eddies 165
Egg cell (of plants) .... 388
427, 430
Food
Electricity . . . 62,72,94,350,
472, 480-501
atoms 500
attraction of 483
conductors and non-conduc-
tors 482
current' 484-487,500
dry cell 485
electrodes 485
electroplating . . . 488-489
electrotyping .... 489-490
energy of . . 72-94, 472, 484, 501
Faraday's discovery . . . 497
Motional 480
heat of 62, 486-487
intensity of 350
law of 350
light of 487-488, 501
theory of 500
voltaic cell 484-485
see also Magnetism
Electrodes 485
Electrons 500-501
Elements (of matter) . . 51-52, 58
Elevation . 259
Em'bryo (of animal and plant
life) 388-389,394
Emulsion 144-146
soap an emulsifier . . . . 145
borax and soda as aids . 146
INDEX
References are to pages
Energy ... 57, 60-94, 98, 100-
107, 137-138, 350, 357-358, 396,
399-400, 407-410, 419, 428-430,
456, 459-474, 483-484, 501
breathing as means of gen-
erating 407-410
by combustion . 72-94, 98, 399,
419, 428-429, 472, 474
by evaporation . . . •. . 101
by molecular motion . . 67, 94
law of 67, 94
by transference .... 357, 474
by transformation . 62-64, 72-94,
357, 470-474
conservation of 63-64, 462, 473
control of 57
evaporation as form of . 100-107
food as generator of ... 399,
419, 428, 430, 456
forms of 60-93, 396
friction vs. ... 63, 462-463
" lost energy " . 63, 462-463
intensity of ...... 350
kinds of :
chemical . . 62,72-94,358,
472-473, 501
electric and magnetic . 72-94,
472, 483-484, 501
gravitational . 62-63,93,483
heat . 61,93,137,357-358,501
light .... 61, 93, 357, 501
mechanical . . . .61, 72-94,
137-138, 470-474
laws of 67, 94, 350
of animals . , . .98, 399, 419, 428
of plants 399
power generated by . . 72-94,
137-138, 470-474, 484, 501
sun, source of 3, 93, 101, 396, 399
Epiglottis 408
Equator 30-31, 39
Equatorial winds 220
Erosion 159-161, 186,
252,278-285
by ice . ,. . . .... 285
by water 278
by waves 159-161
by wind 281-282
sand an agent 282
Es'tuaries 261
Ether ........ 105, 361
Evaporation . . 100-107, 127-128,
133, 136, 153, 166, 170, 172, 186,
278, 327-329, 331, 345, 385
a cause of salt lakes . . . 172
cooling by 104
in irrigation 331
of alcohol 105
of ammonia gas .... 127-128
of ether 105
of gasoline . . . 105, 140, 520
of water . . 100-107, 136, 153,
166, 170, 278, 327-329, 345, 385
moisture in plant-leaves . 385
rain-water 170
sea-water 153, 166
soil-water . . . 327-329,345
process of 100
temperature vs 100-106
Expansion 64-69, 94, 124-125, 136-137
Experiments (The experiment-
number is in bold face) :
air 35-43,97-111
atmospheric pressure . . 44—55,
114-131
earth's magnetism . . . . 8, 37
rotation . . / . .4-7,24-33
shape ....... 2-3,22
surface 80-87,248-279, 161, 512
electricity . . 152-160,480-493
energy . . . 145-146,462-466
food . . . 138-144,419-438
heat 18-34, 64-88
life animal . 133-137,402-417
plant . . 108-123,367-385
seed . . . 124-132,393-396
light .... 100-107, 347-358
magnetism . 147-151, 475-478
matter 9-15,42-55
changes of . . . 16-17,51-55
sky (the heavens) . . . . 1, 8
soils 88-99, 307-327
water . , . . 56-74, 135-170
weather, rainfall . . . 79, 231
winds . . . 75-78,216-218
Extension 42,43
Eye (organ of sight) . 414-416, 423
eyelid 414
8
EVERYDAY SCIENCE
References are to pages
Fall line (of rivers) . . . 547-548
Faraday's discovery . . . 495-497
Farm and garden .... 307-346
base of civilized life . . . 307
building material ana
clothing 307
Fats and oils . 423, 425-429, 456
carbohydrates 425
food properties of ... 425-428
functions of 425-429
oxidation 429
Fault (in land-structure) . . 513-514
Fauna (animals) 530
Ferret's Law 219
Fertility (of soils) .... 308-315
causes of 308
Fertilizers (of soils) . 315-319, 345
Fertilizing (of flowers) . 334, 390-
392, 405
Field of force (of magnets) 476-477
Filaments (of incandescent
lamps) 487
Filters 143
Fingal's Cave (wave-erosion) . 160
Fire (caused by earthquakes) . 515
Fire-control 77-80
Fire-extinguishment .... 94
Fishes (vertebrates) . 400, 533-534
carnivorous 533-534
Flood basins 338
Flood plains . . . 181-182, 185
Flood tide 164
Flooding (in irrigation) 330-331, 346
Flora (plants) 530
Flowers (of plants). . 387-392,422
colors of 390
extraneous means of fertiliz-
ing 390-392
function of 387
scents of 390
seed dispersal of .... 392
structure of 387
Foci (of axis) ....... 26
Fog 104
Food . . . 303, 313-314, 373, 383,
398-421, 423, 425-441, 445-
448, 451-457, 536
absorption of 421
alcohol and tobacco vs. . . 457
Food — Continued
bacteria in . 435-439, 445-449
beverages 427,430,
431-432, 446-448
classes of, fundamental . . 425
carbohydrates. . . 383,423,
425-428, 456
fats and oils 423, 425-429, 456
proteins . 383, 423, 425-429, 456
composition of .... 426, 456
conservation of .... 440-441
cooking and preparation of
433-434, 457
decay of 303, 438
diet, balanced . . . . . 431
disease caused by . . 445-447,
452-455
energy through . . . 399, 419,
428, 430, 456
health vs 425-433
life dependent on . 419, 425-426
chlorophyll in leaves 382-383,
399, 400, 419, 425-426
minerals in 430
pasteurization 447
storage of, by animals . . . 536
tissue-making and tissue-re-
pair by 313-314
varieties of :
animal (eggs, meats, milk,
etc.) . . 427-430,446-447
vegetable (grains and
cereals, fruits, mush-
rooms, nuts, roots) 313, 373,
398-399, 419, 425-426,
430-431,435,437-438
vitamins (vital element of life
in food) .... 430-431,456
water vs 428
Force (attraction) . . 43-49, 58, 93,
326, 476-477
centrifugal 43-47
centripetal (gravitation and
gravity) . . 47-49, 58, 93, 326
magnetic 476-477
Forestry 339-345
abuses of forests . . . 340-344
conservation of forests . 344—345
uses of forests . 339-341
INDEX
9
References are to pages
Formaldehyde (disinfectant) . 445
Formalin (disinfectant) . . . 445
Fossils (of animals and plants)
522-523
Franklin, Benjamin (inventor of
lightning-rod) 483
Freeze (southern " cold wave ") 228
Friction .... 63,72,462,480
generator of electricity . . 480
generator of heat ... 63, 72
methods of lessening . . . 462
Frost 104
Fruits 427-431
vitamin in 431
Fuel-saving 74-77,94
Fulcrum (of lever) . . . . . 464
Fungi .... 398-399,438-439
a cause of ptomaines . . . 439
mushrooms and toadstools 398-399
Gala'pagos Islands (home of
great tortoise) ..... 541
Galile'o (inventor of lift pump) 118
Gases 2,17,42,58,97,
110,115,315,472,504
equality of pressure of . . . 115
formation of, in soil . . . 315
formation of, in volcanic
eruptions . , . . . . 504
incandescent, of the sun . . 2, 16
inert 97
transformers of energy . . 472
Gasoline 105, 140, 520
Gastric juice 420, 433
Geometry (developed by Egyp-
tians) 21
Germination of seeds . . . 393-396
Germs (harmful bacteria) ; see
Bacteria
Geysers (hot springs) . .511-513
causes of 511
effects of 513
times of spouting . . . . 512
Gibraltar (a spit) .... 161-162
Glaciers 285-301,
304-305, 525-528
Alpine or valley . .... 288-289
crevasse' 289
glacial flour 291
Glaciers — Continued
glacial formations . . . 279-300
glacial lakes 300-301
Glacial Period . . 285, 292-298,
525-528
effects upon animals and
plants 525-528
effects upon surface 285, 292-298
glacial scratches 291
icebergs 294-295
ice fields (of Antarctic regions
and Greenland) . . . 293-294
moraines .... 290,297-300
waterfalls (Niagara and Yo-
semite) 526-528
Glass (reflector of light) . . 348-349
Globigeri'na 532
Gneiss (metamorphic rock) . 255
Gold (mineral) 516
Graded rivers 185
Grafting (method of plant-prop-
agation) 377
Grains and cereals . . . 427-431
composition of .... 428-431
Granite (igneous rock) . . . 253
Grape sugar (developed in
plant-leaves) 382
Graphite (conductor of elec-
tricity) 490
Graphs 213-214
Gravel 310, 345
Gravitation (attraction) . . 47, 49,
58, 93, 326
laws of 47, 58
Newton's discoveries . . 47
Gravity (earth-attraction) 47-48, 326
vs. soil-water 326
weight 47
influences upon direction . 48
Ground-water 170
Gulf Stream 162-164
influence upon climates . 162-164
Haemoglobin (of blood) ... 411
Hail 234
Halley's Comet 18
Halos .* 360,365
Hammerfest's climate (Gulf
Stream) 164
10
EVERYDAY SCIENCE
References are to pages
Harbors 188,548-552
advantages of .... 548-552
necessity of 548-549
of atolls 549
of deltas 549
of depressed coasts .... 549
of sand reefs and spits . . 549
of submerged craters . . . 549
Health and sanitation 99, 107-108,
112-114, 120, 133, 202-203,
361-362, 401, 408, 421, 433, 439,
441-457
antitoxins of the blood . . 444
artificial development of,
as prophylactics . . . 444
bacteria vs. . . . 120,361-362,
401,441-449
conservation of 457
corpuscles, white, as disease-
fighters 444
effects of dry and moist cli-
mates upon .'.... 108
humidifiers 107-108
food and its preparation vs.
433-434
laws of 421
ptomaines vs 439
sanitation of homes and sur-
roundings . . . 202-208,
361-362, 443-457
cleanliness 451-457
disinfection 361-362, 443-445
sewage disposal . . . 449-451
water-systems of city-
supply . 202-208, 447-449
throatal adenoids vs. . . . 408
toxins vs 444
ventilation . . 99,112-114,133
Hearing ; see Ear ; Sound
Heart (engine of body) . . 409-413
composition of 412
function of 412-413
shape of 412
structure of 412
Heat .... 2-3,16,18,28-31,
60-95, 98, 107, 110, 124-127,
136-139, 209-215, 221, 347,
350-353, 357, 429-431, 480,
486-487, 503
Heat — Continued
adiabatic 125, 221
air as conductor of ... 107, 215
properties of, vs. heating
systems 110
animal and plant life affected
by .... 62,98,347,508
boiling in different altitudes 127
capacity of water to hold . 139
compression of air vs. . . . 124
conduction of ... 87-88, 94
conservation of 64, 90-94, 209-210
contraction by ... 65-69, 94
convection currents of . 88-90, 94
density vs. . . . . . 66,94
electricity as generator of .62,
486-487
energy generated by . . 60, 93,
137, 429
expansion of air vs. ... 107
factors in .... 211-213,429
insolation of 209
intensity of 350
latent heat 84-86
light transformed into . . 347, 357
magnetism affected by . . 480
mass vs 66, 94
measure of .... 80-84, 94
molecular movements in . 67, 94
production of ... 69-72, 94
radiation of 90
reflection of 351-352
transmittance of ... 209-210
water vs 136-138
absorbed in 138
evaporated by .... 139
Heat lightning 230
Heavens, the 1-19
Hills ; see Mountains
Honey of bees 405
Honeycomb 405
Horizon 355
" Hot Wind " of Texas ... 229
Household .... 117-125,146,
254-255, 307, 516-519
appliances. . 117-125,486-488
bacteria in relation to forma-
tion of coal and peat . 516-517
borax as aid to emulsion . . 146
INDEX
11
References are to pages
Household — Continued
building-material and cloth-
ing 307
homes dependent upon soil . 307
minerals and mineral oils 254-255,
516-519
see also Sanitation
Humidifiers 107-108
Humidity 102-107, 133
absolute humidity . . . . 102
causes of 104
comfort vs 106-107
dew-point 102-104
hygrometer 103
relative humidity . . . . 102
saturation 102
Humors (of eye) 414
aqueous 414
vitreous 414
ttamus (constituent of soil) . 311,
314-320, 327, 345
bacteria in 314-315
qualities of . . . . .319-320
Hydrogen (a gas) . . . 136, 167,
425, 484-485
constituent of food .... 456
constituent of water . . 136, 167
formed in voltaic cell by elec-
tricity 484-485
Hydrogen peroxide (disin-
fectant) . . 444
Hydrometer 153
Hygrometer 103-104
Ice 127,137-138,279,
285-287, 293-295, 303
a factor in earth's surface
changes 303
contraction of, after forma-
tion . . ... . . . 138
erosion by 285
expansion of, while forming . 138
formation of 137-138
glaciers, icebergs and ice
fields 285-301,304-305,525-528
manufacture of 127
power of 279
pressure of . . . . =» . . 138
weight of 138
[Humiliation ; see Light
Imperial Valley (fertility of) . 173
Incandescent lamps .... 488
Incidence (angle of) .... 352
law of 352
Inclination (of axis) .... 26
Industries 546-547
Inertia 42-49, 58
laws of . . . . . 43, 44, 48, 49
[nfluenza (bacterial disease) . 442
Inorganic matter (or substance) 426
Insects (invertebrates) 400-405, 533
beneficent 403-405
productive 403-405
bee 403-405
silkworm 403
harmful ..403
of the sea . 533
of the soil 403
Insolation 209-210
Intakes (cribs) 204
Intensity 349-350,477
of heat 350
law of 350
of light . . , i . 349-350, 477
law of 477
of magnetism 477
of sound 477
International Date Line . . 35, 40
Intestines 420-421
large 421
small 420-421
function of . . . . . . 421
liver 421
pancreas 421
Inventions . 39, 91-92, 103-107,
111, 117-131, 137, 143, 147-150,
202-206, 416, 459-474, 467-478,
483, 486-501
Invertebrates . . . 317-319,345,
400-405, 423, 533-534
insects . . . 400-405,533-534
protozoa . . 400-401,423,452
shellfish 400
worms . . 317-319,345,401-402
Iris (of eye) 414
Iron and steel (magnet-making
minerals) 476
Irrigation 330-331, 346
12
EVERYDAY SCIENCE
References are to pages
Irrigation — Continued
ditching 331
flooding .... 330-331,346
evaporation 331
Islands . . . 256,261,540-541
continental 256, 540
oceanic 540
tropical 540
variations of life-forms on 540-541
Isobars 214
Isothermic maps .... 213-214
Isotherms 213
Isthmus (of land) 525
Jupiter (a planet) . . . 11-13,353
brilliancy of 12
day on 12
distance from earth and sun 11
eclipses of moons of ... 353
size of 13
surface of ....... 11
Kerosene (mineral oil) . . . 520
Kindling temperature . . 72-73, 94
methods of bringing sub-
stances to 73
spontaneous combustion . . 73
variation of, in different sub-
stances 72
Kinetic energy . . . .60, 93, 396
Lagoons . 259-260
Lakes .... 171-174,177-178,
185, 300-301
as filters 172
as reservoirs 172
evaporation the cause of salt
lakes 172-173
fringing lakes 185
glacial lakes 300-301
outlets of 172-173
Land . . . 160-162, 175-176, 181-
190, 247-306, 308, 525, 535-552
bars, sand . . . .162, 258, 282
beaches 161,251
capes 258
cliffs 160
composition of 252-255, 275, 308
continental shelf . . . 256-259
Land — Continued
continents .... 248, 256-276
divides 175-176
drowned river valleys . . 188-189
dunes, sand . 258-259, 283-284
hemispheres 537-538
hills 264-265
islands . . . 256,261,540-541
isthmus ' 525
life on ... 257-263, 535-552
marshes 260
mountains .... 22, 238-241,
248, 264-267, 541-543
plains . . 181-185, 257, 268-276,
301-302, 544-548, 553
reefs, sand 257-260
spits 161-162
structure of 255-256
terraces 186
Latent energy .... 60, 93, 396
Latitude . 32
Latitudes, horse 221
Lava (volcanic eruption) . 277, 506
Leaves (of plants) 379-386, 421-422
arrangement on stem . . 379-380
regulation of sunlight . . 380
composition of .... 382-383
function of .382
shapes of 380-381
sun's action upon .... 384
veins of 381
water in 385
Lens (of eye) 414-416
Lenses 355-356
concave 355
convex 356
use of 355
Levees 184, 338
Lever 462-465
law of 464
law of machines 465
principle of 464-465
Life (common to animals and
plants) . . . 98-100, 135, 141,
151-152, 210, 257-263, 311-319,
345, 347, 366-458, 522-553
adaptability to physical con-
ditions .... 528-535,552
ancient history of ... 622-523
INDEX
13
References are to pages
Life — Continued
composition of 366
dependence upon :
air .... 98-100, 141, 152,
210,313,425
earth 366
heat 347
light 347,364
soil-elements . . . .302,311
sun 366, 384
water .... 135,311,425
development of forms of
522-523, 539-540, 552
differentials as to animals
and plants 366
distribution of ... 524-525,
537-541,552
effects of :
climatic changes .... 525
Glacial Period . . .525-526
physical features of sur-
face . . 277-278,523-524
water . . 151-152, 166-167
of ocean 166-167
embryo of .... 388-389, 394
fertilizer of soil, as . . . . 318
food, as 419
necessary for . . 313-314, 366
growth of .... 151-152, 366
man in relation to other
forms of 425
microscopic, necessary to
other life 311
of the land . 257-263, 535-544,
552
of the ocean . . . 531-535, 552
of the soil .... 311-319,345,
401-402, 535
phosphorescence of ... 533-534
physical conditions of earth
vs 522-553
powers of 366
propagation and reproduc-
tion 366,524-525
similarity in low forms . 399-400
Light .... 2-9,16,18,37,40,
60-62, 93, 209, 347-365,
486-487, 533-534
color 356-364,390
Light — Continued
comfort vs 361
conservation of . . .37, 40, 362
direction of movement of 347-349
disease vs 361-362
electricity a generator of
487-488, 501
energy generated by . . 61, 93,
357, 501
essential to life .... 347. 364
intensity of ... 349-350, 364
moon as chief source of, at
night 16, 349, 351
properties of 348
reflection of 348-349,351-352,364
refraction of ... 353-356, 364
spectroscope 358,364
spectrum . . . 357-358,364
speed of .... 352-353,364
stars as lesser lights at night
4-9, 347
sun as chief source of . . 2-3, 18,
60, 93, 347, 364
artificial lighting . 347, 362-363
moon and stars as lesser
lights . . . 4-9, 16, 347, 349,
351
theories of Newton as to . . 361
Lightning (electricity in) . . 483
lightning rods 483
Limestone (sedimentary rock) . 254
Liquids 42,58
Lisbon (earthquake and ocean-
wave) 514
Listerine (disinfectant) . . . 445
Litmus paper (in acid and alkali
tests) 54-55,58
Liver 421
Loadstones . . . 37-40,475-480
attraction of 476-477
field of force 476-477
intensity of attraction . . 477
poles of 39, 40, 476
Loam 309-310,345
Local soil (sedentary) . . . 307
Loess beds (deposition) . . . 285
Longitude 32
Looming (mirage) .... 355-360
" Loss of energy " . . 63, 462-463
14
EVERYDAY SCIENCE
References are to pages
Loss of energy — Continued
friction 63, 462-463
• methods of lessening 63, 462-463
Lubricating oils 520
Luminous bodies (light from) . 348
Lungs 407-409
air sacks 408
air tubes 408
arteries, capillaries, veins . 409
Lysol (disinfectant) . . . 444-445
Machines 462-465
law of 465
Maelstrom (whirlpool) . . . 165
Magnetism . . 37-39, 475-480, 501
attraction of 476
compass . . . 39,476-478,501
field of force 476-477
intensity of attraction . . . 477
iron and steel as media for
magnets 476
loadstones . . . 37-40, 475-480
magnets. . . 37-40,476-480
molecular theory as to . 478-480
properties of 479-480
Magnets ; see Loadstones
Malaria (protozoan disease) 401, 452
Mammals 400,533
Man (vertebrate ; mammal)
166, 277-278, 303, 313-314, 373,
383, 398-458, 523-553
history of 522-523
structure and functions of :
organs :
of sense :
ear, of hearing 416-418, 423
eye, of sight . 414-416, 423
nose, of smell . . 413, 423
skin, of touch . . 413, 423
tongue, of taste . 413, 423
of vital functions :
brain, seat of nerve-
communication . . 418
heart, engine of body
409-413
lungs, blood-purifiers
of body . . .407-409
stomach, digester of
body 420
Man — Continued
skeleton 405-407
appendages, ribs, skull,
spine 406-407
cavities within :
abdomen ..... 410
thorax 409
systems :
of breathing . 407-410, 423
of circulation of blood
410-413, 423
of communication (nerv-
ous system) . 413-418, 423
of digestion . . 419-421, 423
tissues :
muscles, of locomotion . 407
nerves, of sense-trans-
mission . . 407,413^23
Manures (fertilizers) . . . 316, 334
Marble (metamorphic rock) . 255
Mars (a planet) .... 11-13
brilliancy of . .. . . . 12-13
day on 12
distance from earth and sun 11
Marshes , . . 260
Marsupials (vertebrate pouch-
animals) 538-539
Mass 66, 94
Matter 42-59, 67, 310-314, 475-501
chemical changes of . . 53, 58
chemical compounds of . 53-58
chemical mixtures of . 53-54, 58
classes of :
inorganic (mineral) . . 310-311
organic 314
composition of ... 42, 49-52,
58, 67, 500-501
molecules . . 49-50,51,58,67
atoms 50-51,58
electrons .... 500-501
compounds of ... 51-52, 58
elements of .... 51-52, 58
energy latent in 57
forms of :
gases . . . . 2, 17, 42, 58, 97,
110,115,315,472,504
liquids 42,58
solids 42,58
mixtures of .... 53-54, 58
INDEX
15
References are to pages
Matter — Continued
neutralization of acids and
bases 55-59
physical changes of . . 52-53, 58
planetary movements . 48-49, 58
properties of :
centrifugal force . . . 43-47
gravitation 47
electricity and magnetism
475-501
extension .... 42-43,58
inertia 42-47,58
weight of 47-48
Meanders .... 181-183,187
intrenched 187, 207
Meat 427-429
as food 427
oxidation of 429
protein in 427-429
quantity required in diet . . 428
Media (of light) .... 354-355
Mercury (a planet) . . . 11-13
day on 12
distance from earth and sun . 1 1
orbit of 12
position of 13
temperature of 11
Meridians and parallels 30-37, 39-40
degrees, minutes, seconds . 32
International Date Line . 35, 40
latitude and longitude ... 32
measurement of time . . 32-37
Prime Meridian 32
Standard Time . . . 34-35, 40
daylight saving ... 37, 40
time meridians of ... 35
Mesas . . '. V .. . -. . 272, 276
Meteorites 11
Meteors ........ 11
heat of 11
light of 11
Mica-schist 255
Microbes . „ * . 98
Microscope 356
Midnight I •' .. . 33
Milk .... 427,430,446-447
a balanced food .... 427-430
constituents of 430
dangers from infected . . 446-447
Milky Way (stars) .... 5
Mineral matter in soil . . 310-311
Minerals 515-520
Mining . . . 515-521,542-543
chief industry of mountain
regions 542-543
of coal 254,516-519
of copper 516
of gold 516
of iron 516
of peat 309, 517-518
of petroleum 519-520
of silver 516
regions of 516
veins of minerals .... 515
Mirage (looming) .... 355, 360
cause of 355
Moisture (water-vapor) . 100-107,
112, 141, 280, 303, 535
a factor in atmospheric
weathering 280
a factor in development of
bacteria, molds, yeasts . . 303
a factor in life of animals and
plants 535
in air 100-107,141
Molds 303,399,422
spores 399
Molecules (of matter) . 49-59, 67,
94, 478-480, 500-501
atoms 50-51,58
electrons 500-501
changes in . . . . . . 53, 58
compounds .... 54-55, 58
neutralization . . 55-56, 58-59
energy in 67, 94
molecular theory in magnet-
ism 478-480
Monocotyledons .... 375-377
structure of 375
Month (origin of) 15
Moon, earth's . . .2,4,14-17,19,
165, 210, 347-351
a source of reflected light 16, 347,
349, 351
axis of 15
day and night on ... 15, 17
diameter of 15
distance from earth and sun 15, 19
16
EVERYDAY SCIENCE
References are to pages
Moon, earth's — Continued
eclipses 16-17, 19
heat of 16
light from ... 16, 347, 349, 351
orbit of 15
phases of 16,19,349
revolution of .... 15-16, 19
rotation of 15
size of 2
surface of 14-15
tides influenced by . . 17, 19, 165
weight of 15
without atmosphere or water 210
Moons (satellites) .... 11-19
Moraines 290, 297
ground 297
lateral 29C
medial 290
terminal 290,298
Morse, Samuel F. B. . . . 492, 494
Mosquitoes .... 403,452-454
Mountains . . .22,238-241,248,
264-267, 541-543
age of, old and young . . 266-267
effects of, upon climate . 238-241
effects of, upon history . 541-543
hills 264-265
mining the chief industry
of 542-543
peaks of 266-267
products of recent earth-
changes 248
ranges of 267
structure of 265-266
volcanoes .... 503-511,521
Mouth 408, 420, 423
esophagus (throat) .... 408
epiglottis 408
saliva 420,433
teeth 420
Moving pictures 416
Mulches 328
Muscles 407
Mushrooms 398-399
spores 399
Neap tide 165
Neptune (a planet) . 5,11-13,49
day on 12
Neptune (a planet) — Continued
discovered by laws of gravita-
tion and inertia .... 49
distance from earth and sun 5, 11
moons of 13
orbit of 12-13
Nerves (transmitters of im-
pulses and sensations) . . 413-423
of hearing 416-418
of sight 414-416
of smell 413
of taste 413
of touch 413-414
Nervous system 407, 413-418, 423
brain as seat of . . 407, 418, 423
nerves 413-418
spinal cord ...... 407
Neutralization (of acids and
bases) 55-59,315
Newton, Sir Isaac .... 43-44,
47-49, 58, 361
Newton's First Law . . 43-44
on gravitation 47
on light 361
Niagara Falls and River . . 177, 526
Nitrogen (a gas) . . 52, 97-100,
133,311-314,345,425
an element 52
compounded for use ... 99
constituent of air ... 97-100
necessary for life . . .313-314
constituent of food . . 425, 456
necessary for soil .... 310-314
North Star (Polaris) ' . 9-10, 24
" Northern Lights " (Aurora
Borealis) 360
Nose (organ of smell) . . 413, 423
Obsidian (igneous rock) . . . 253
Ocean . . 17, 19, 152-169, 213, 249-
251, 256-258, 514, 531-535, 552
composition of water of . 152-154
currents in ... 161-164, 169
effects of . . . 162-164,213
motion of 162
rotating surface of . . . 162
sargasso seas 162
density of 154, 168
depth of 154, 168
INDEX
17
References are to pages
Ocean — Continued
floor of 155-156, 168
heat vs. distance from . . . 213
land interchanges with . 249-251
life in and of ... 531-535, 552
pressure in ... 154-155, 168
swell below surface of . . . 155
temperature of water of 156-157,
168
tides of ... 17, 19, 164-166, 169
value of, to man and other
life 166-169
volume of air in water of . . 155
waves 157-161, 169
" Oil on water " 158
Ooze (of ocean-floor) .... 156
Optic nerve 414
Orbits (of planets) ... 12, 26-31
Organic matter (or substance) . 426
Osmosis (diffusion through
membrane) 371
Ovary (of flower) 387
Oxbow lakes 182, 184
Oxidation 429
Oxygen (a gas) .... 97-100,
132-133, 136, 141, 152, 167, 280,
399-400, 410, 413, 425, 456
a constituent of air . . . 97-100,
132-133
a constituent of water . . 136, 167
agent of combustion ... 98
agent of weathering . . . 280
constituent of food .... 456
necessary for life . . 98, 141,
152,410,413
Pancreas 421
Parallels ; see Meridians and
parallels
Parasites 397-400
Passes (in mountainous re-
gions) 176
Pasteurization (of milk) . . . 447
P.eat 309,517-518
Peroxide of hydrogen (disin-
fectant) 444-445
Perspiration 106
Petrified trees 522-523
Petroleum 519-520
Phosphate rock (as fertilizer) . 317
Phosphorescence .... 533-534
light-emission by micro-
scopic animals .... 533
Phosphoric acid (as fertilizer) . 316
Phosphorus (as fertilizer) . 97,311.
316, 345
ignition qualities of ... 97
necessary for soil . . . . 311
Photography (utilization of
principles of light-refraction
and magnifying) .... 356
Physical changes (in matter) 53, 58
Physical features (of earth) 541-552
effects upon life .... 541-552
Piston (of engine) 471
Pith rays 374
Plains . . 181-182,185,257-259,
268-276, 285, 301-302, 544-548, 553
coastal 257-259,274
effects of life on . . 544-548, 553
flood 181-182,185
Great Plains of U.S. . 273-275,
276
prairies . . 274,285,301-302
plateaus .... 268-273, 276
Planetary movements . . 48-49
laws of gravitation and in-
ertia 48
discovery of Neptune and
Uranus by 49
Planetary wind belts .... 222
Planetoids ; see Asteroids
Planets . . . 4-15,18-19,20-21
brilliancy of Jupiter, Mars,
Venus 12
day and night on . 12-14, 18, 19
development of science con-
cerning 8-9,20-21
distances from one another
and sun 11, 19
distinguishing features of . . 4-5
light of 4, 5, 13, 19
reflected rays from . . 13-14
moons of .... 11,14,15,19
orbits of 12,19
positions 11-12
revolutions ... 5, 12, 18, 19
rotations 12, 19
18
EVERYDAY SCIENCE
References are to pages
Planets — Continued
sizes of 11, 13, 19
solar system 10-19
surfaces of 11
temperatures of . . . . 11, 19
visibility of 13
Plants . . . 98-100, 166, 279, 284,
366-399, 419, 421-422, 424,
425-427, 431, 435-441, 445-447,
522-541
bacteria . . 398-399,422,435
cambium layer .... 374, 377
capillary action 372
carnivorous plants . . . 380-381
cells of 371
chlorophyll in 397
circulation of sap in ... 382
classes of :
by distribution :
of land 284, 535-536, 540-541
of sea . . . . 166, 531-532
dependents. . . 397-399,422
green-leaved plants . . 397-399
diastase 383
energy of 399
factors in surface changes . 279
food, as 373, 399, 419, 425-427, 431
fossils of '. . 522
growth of 372
molds . 399, 422
osmosis in 372
physical conditions vs. . 522-541
propagation of . . 377, 392-393,
398-399
protoplasm in 371
self -protecting plants . . . 381
structure of :
flowers .... 387-392,422
leaves . 366,379-386,421-422
roots . . . 366-373, 421-422
seeds . . . 389, 392-396, 422
stems . 366,373-379,421-422
yeasts . . 303, 399, 422, 436-437
Plasma 411
Plateaus 268-273,276
dissected 270-271
old ........ 272-273
young 268-269
Pneumonia (bacterial disease) . 442
Polar winds 220
Polaris ; see North Star
Poles :
of earth 8-9, 26
of magnets 476
Pollen 388
Pollen basket (of bees) ... 404
Polyp, coral 533
Potash (fertilizer) 317
Potassium (fertilizer) . . . . 316
Potassium (necessary for soil)
311,345
Potential energy 396
Power (generated by combus-
tion, running water, wind) 472-473
Prairies (of U. S.) 274, 285, 301-302
Pressure . . . 123-126, 146-147,
154-155, 210-211, 502-503
boiling-point vs 125
condensation of steam vs. . 126
effects of 502-503
laws of 123
of air . . . . . 123, 210-211
of water . . 146-147, 154-155
transmission of 147
within earth 502-503
Prism (separator of colors of
spectrum) 356-359
Promontories 160
Proteins :
composition of . . 383, 425, 427
food properties of .... 428
amount necessary in diet . 428
found in eggs, fish, milk,
meat, etc 427
origin of ....... 425,
required for growth and re-
pair of body-tissues . . . 428
Protoplasm (life-principle) 383-384,
400, 419, 425, 428-430
composition of 428
developed in green plant
leaves . 38§-384, 400, 419, 425
428, 430
Protozoa (invertebrates) 400-401,
452-455
a cause of disease . 401, 452-457
analogy to bacteria .... 401
Ptomaines (caused by fungi) . 439
INDEX
19
References are to pages
Pulse 412
Pupil (of eye) 414
Radiation (of heat) .... 90
Rain . 104, 141, 170-174, 231-237,
245
Rainbow 359,365
Rats (carriers of disease) . . 454
Reclamation (of soils) . . 332-338
of alkali land 332-333
of arid land 336-338
of overflowed land . . . 338-339
Reefs, sand 257-260
Reflection (angle of) .... 352
law of 352
original rays of 352
Refraction (of light) . 353-356, 364
cause of 353-355
effects of - . 355
Relishes 431
Reptiles (vertebrates) . . . 400
Repulsion (of magnets) . . . 476
Reservoirs ...... 172, 201
for water-supply of cities . . 201
lakes as 172
Respiration ; see Breathing
Retina (of eye) 414, 416
Revolution (of earth) . 26-31, 39-40
Rivers .... 176-208,546-548
as inland waterways . . 190-196
improvement of ... 192-196
classes of .... 181-190, 207
deltas . . 189-190, 207, 549
drowned . . . 188-189,207
intermittent 186
meanders . 181-183, 187, 207
terraced 186
development of . . 177-181, 186,
207
graded 178-181
old-age 186, 207
young .... 177-178,207
fall line of 547-548
of coastal plains .... 546-547
Rocks . . . 252-255,275,279-281
igneous 252-253, 275
metamorphic . . . 254-255, 275
sedimentary . . . 253-254,275
weathering of .... 279-281
Roemer on deductions as to
light 352-353
Rolling (of soils) 327
Roots (of plants) 366-373, 421-422
as food 373
functions of 373
growth of 372-373
rise of sap in 372
structure of 372
uses of 367-371
Rotation (of earth) . . 23-26, 39
effects of 24
four cardinal directions . 24, 39
inclination of axis .... 26
Run-off (of water) 174
Saliva 420,433
Salt 142, 425
necessary for life-processes . 142
solutions of 142
Salt Lakes 172-173
causes of 172
fertility of beds of . . . . 173
Saltpeter (as fertilizer) . . . 316
Salts 54,58
obtained by neutralization of
acids and bases . . . 54, 58
San Francisco (earthquake and
conflagration) 515
Sand . . . 162, 281-285, 307-310,
319-320, 345, 549
an agent in surface-changes
281-285
deposition of 283-285
Sand blasts 281
Sandstones (sedimentary rock)
253-254
Sandy soils .... 307, 319-320
Sanitation ; see Health and sanitation
Santa Ana (cyclonic storm) . . 229
Sap (in plants) 372
Saprophytes (dependents on
dead animals and plants) . 397
Sargasso seas 162, 532
Sargassum (sea-plant) . . . 532
Satellites ; see Moons
Saturation 102-103, 104, 106, 112, 141
in solutions 141
in air 102-103, 104, 106, 112, 141
20
EVERYDAY SCIENCE
References are to pages
Saturn (a planet) .... 11-14
day on 12
distance from earth and sun 11
moons of 11
rings of 13-14
surface of 11
Scents (of flowers) 390
Science, earth (development of)
8-9, 20-21
Sea .... 160,213,249-251
beaches 251
caves 160
distance from, a factor in heat 213
interchange with land . . 249-251
Seasons 27-31,40
causes of 27-31
equinoxes, autumnal and
vernal 31
solstices, summer and winter 30
Seaweeds .... 162,531-532
sargassum 532
sargasso seas 162
Seeds (of plants) . . . 388-389,
392-396, 422
cotyledons 394, 422
development of 395
dispersal of 392-393
embryo 388-389, 394
energy of 396
germination of .... 393-394
Seepage (in irrigation) . . . 326
Senses 413-418,423
nerve-connection with brain . 413
of hearing 416-418
of sight 414
of smell 413
of taste 413
pf touch 413
Sewage (disposal of) . . . 449-450
see also Health and sanitation
Shellfish (invertebrates) ... 400
Shells (of low-life animals) . . 401
chalk cliffs of England . . 401
" Shooting-stars ; " see Meteors
Shore .... 243-244,256-259,
540-541, 549
continental shelf . . . 256-259
bars, dunes, islands,
lagoons, reefs 256-259, 540-541
Shore — Continued
depressed coasts 549
effects upon, of sun . . 243-244
Sight (sense of) . . . 414-416, 423
Silkworms (productive insects) 403
Silt 309-310,321,345
Silver (mineral) 516
Sirocco (cyclonic storm) . . . 229
Skeleton (of man) .... 405-406
appendages 406
ribs 406
skull 406
spine (vertebral column) . . 406
Skin (organ of touch) . . 413, 423
Sky (the heavens) .... 1-19
" Slack water " 164
Slate (metamorphic rock) . . 255
Sleeping sickness, African (pro-
tozoan disease) . . . .401,452
Sleet 104, 234
Smell (sense of) 413
Snow . 104, 234
Soap (emulsifier) . . . .145, 445
Soils ... 57, 173, 197-198, 209,
212-213, 284-286, 293-300,
307-346, 401-403, 534
agricultural . . . 313-341,345
building-materials dependent
upon 307
classes of . 284-285,307-310,345
clothing dependent upon . . 307
composition of . . 308-326, 345
cold frame 209
conservation and reclamation
of .... 322,332-339,345
cultivation of ... 329, 334, 345
drainage of ... 313, 323-326
331-332, 334, 345
evaporation of soil-water 327-329
fertility of . . 173, 308, 313, 315,
317-319, 345, 401-402, 535
fertilizers .... 315-319,345
food dependent upon . . . 307
forestry vs 339-345
formation of 285-300, 307-310, 345
heat vs 212
insects vs 403
life (animal and plant) in
311-319, 345, 401-402, 535
INDEX
21
References are to pages
Soils — Continued
bacteria, beneficent and
harmful . . . 314-318,345
earthworms, fertilizers of
317-319, 345, 401-402
mulching .... 328-329,345
subsoil 307-310
surface soil 308
varieties of 307-310, 319-321, 345
ventilation of 313
water vs. . 311-312,319,321-326
Solar day 33
Solar family, earth's ; see Solar
systems
Solar systems :
sun's 5, 10-18
stars? 6
Solids 42,58
see also Matter
Solstices (summer and winter) 30
Solutions 139-142
in water 142
saturated 141
with salt 142
Solvents (alcohol, gasoline, tur-
pentine, water) 140
Sound 416-418,423
wave-motion 417
medium of hearing . . . 417
transmission of .... 418
ear, organ of .... 418
Specific density of water . . 150
Specific gravity 47
Specific heat 84
Spectroscope 358, 364
Spectrum 357-358, 364
Spinal cord . . . .... 407
Spine (vertebral column) . . 406
Spits 161-162,549
Gibraltar 161-162
harbors of 549
Spores (of molds and mush-
rooms) 399
Springs (cold and hot) ... 196
Spring tide 165
Sprout (of plants) 394
Stamens (of flowers) .... 387
Standard time .... 34-50, 40
daylight saving .... 37, 40
Standard time — Continued
International Date Line . 35, 40
time meridians of .... 35
variations from exact time . 34
Starch (a carbohydrate) 382, 426-
429
Stars 3-10,18-19,347
constellations of . . . . 9-10, 19
distances from earth and sun
6-8, 18
Arcturus, light from . . 7
light of 4-9, 347
Milky Way 5
North Star 9
positions of 5, 8, 9
sizes of 6
suns, as 6, 18
solar systems 6
Steel and iron (as magnet-
making minerals) .... 476
Stems (of plants) 373-379, 421-422
buds of 378
functions of 375
propagation on 377
structure of 373-377
types of 375,422
varieties of 375
Steppes (of Russia) .... 285
Stigma (of flowers) .... 387
Stock-yard by-products (as
fertilizers) 316
Stomach 420
gastric juice 420
see also Digestion
Stomata (of plant-leaves) . . 386
Storms 125,221-231
adiabatic cooling and heat-
ing, a cause of .... 125
anti-cyclonic 224
cyclonic .... 221,226-231
see also Winds
Streams ; see Rivers
Submarines 150-151
Submergence . . . 150-151,303
a factor in surface-changes . 303
in water 150-151
of submarines .... 150-151
Subsoil 309
Substances ; see Matter
22
EVERYDAY SCIENCE
References are to pages
Sub-surface water .... 196-198
Sugars (carbohydrates) 382, 426-429
Sulphur (disinfectant) . . . 445
Summaries :
air and atmosphere . . . 132-134
earth 39-40
energy 474
heat 93-95
life (animals, man, plants)
421-423, 456-457, 552-553
light 364-365
magnetism and electricity . 509
matter 49-51
sky 18-19
soils 345-346
surface (crust, outside and
within) . . 275-276,304-305,
520-521
water and waterways . 167-169,
206-208
weather and climate . . 244-246
Sun, our . . 1-19, 27-30, 60-95, 101,
165, 209-210, 242, 248, 303,
347, 350, 355, 360, 364-365,
396, 399-400, 535
appearance of . 2-4, 17, 360, 365
incandescent gases . . . 2, 17
corona . . . 17, 360, 365
spots of 2-4
atmosphere as cold frame 209-210
circumference of 1
composition of 2
diameter of 2
distance from earth . . 2, 350
effects of, upon earth's sur-
face 248, 303
upon interior 248
upon exterior 303
effects of, upon life .... 535
evaporation caused by . . 101
family of 5-19
influence of, upon tides . . 165
interior of 2
rays of 28-30, 242
by day and night . . 28-30
by seasons 28-30
penetrating land and water 242
size of 1-2, 18
solar system 5, 10-18
Sun — Continued
source of :
clothing ....... 3
energy . . . . . 3, 399-400
food 3,399
heat .... 2-3,18,60-95
life 99,384
of animals 384
of plants 99, 384
light . 2-3,18,60,93,347,364
power 3
surface of 2
transmitter of heat and light, as 209
volume of 2, 18
Sun dial 33
Sunlight (as disinfectant) . . 445
Suns:
our sun ; see Sun
stars ; see Stars
Sunset 358, 365
Surface (of earth, crust) . . . 166,
247-306, 502-553
changes in . . 249-252, 258-263,
275-305, 523, 525-528
by burial and exhumation
258-259, 282-284
(through wave and wind action)
by decay and growth . . 279,
302-303, 305
(through animals and plants)
by deposition and erosion
252, 278-282
(through volcanic, water,
wave and wind action)
by depression and elevation 252
(through crust-move-
ment and volcanic ac-
tion)
by emergence and submer-
gence 260-263, 275, 303, 523
(through ocean and other
water-bodies)
by ice and snow . 279, 285-305,
525-528
by interchange of land and
sea .... 249-252,523
by rock-weathering . 278-281,
304-305
characteristics of, 252, 258-264, 275
INDEX
23
References are to pages
Surface — Continued
cycles of change .... 303
interior conditions of, 249, 502-521
pressure vs. temperature
502-503, 520-521
volcanic action . . . 504-521
earthquakes . . . 513-515
faults 514
geysers . . . 511-513,521
islands 509-511
volcanoes :
distribution of . . 508-511
Monte Nuovo 504,506,521
Mt. Pelee . 506-508, 521
Vesuvius . . 504-506,521
life (of animals, man, plants)
in relation to . . 166,277-279,
522-553
mineral deposits of ... 515-521
coal, copper, gold, iron,
silver 516-519
peat 517-518
petroleum and other oils, 519-520
veins of minerals .... 515
original condition of 247, 275, 278
structure of 255-274
Suspension of matter in water . 142
Swamps 174
Swarm (bee-colony) .... 404
Swell (in ocean) 155
Tantalum 488
Taste (sense of) 413
Teeth 420
Telegraph 492-494
invented by Morse . . . 492, 494
key of 493-494
sounder 493-494
wireless 495
Telephone. ...'... 495
Telescope (lenses of) .... 356
Temperature .... 11,72-94,
100-102, 106-109, 136-138, 142,
156-157, 211-213, 227-228, 248, 281
a factor in surface-changes . 281
air vs 107-109
evaporation vs. 100-102, 106-107
graphic method of showing
records of . 213
Temperature — Continued
heat vs 72-94
specific heat 84
measurement of ... 80-82, 94
thermometers . . 80-82, 93-94
of ocean waters . . 156-157, 213
of planets 11
of salt solutions 142
pressure vs 136-138,
211-213, 227-228, 248, 502
vs. depth within earth . 248, 502
vs. distance from sea . . 213
vs. height 212
vs. latitude 211
vs. soil 212
vs. storms 227-228
vs. water 136-138
Terraces, river 186
Terrestrial winds . . . ,221, 245
Texas fever (bacterial disease) 454
Thermometer . . . 80-82,93-94
scales of 81-82
Centigrade . . . 81-82, 93-94
Fahrenheit .... 82, 93-94
formulae 93
Thorax (of man) .... 409-410
Throat 408
Thundersqualls ; see Thunder-
storms
Thunderstorms . . . 229-230, 245
cause of 229-230
Tick (carrier of disease) . . . 454
Tides (of ocean) . 17-19, 164-166
eddies, tidal undulations,
whirlpools 165
Antwerp, Hell Gate, Mael-
strom . 165
influence of moon upon 17, 19, 165
influence of sun upon . . . 165
" slack water " 164
varieties of 164-166
ebb tide 164, 166
flood tide 164
neap tide 165
spring tide 165
Tillage ; see Cultivation
Time . 24, 26, 34-35, 37, 40, 248
in formation of earth . . . 248
International Date Line . 35, 40
24
EVERYDAY SCIENCE
References are to pages
Time — Continued
measure of . .
day and night .
year ....
Standard Time .
variations from
24-26, 33
24-26, 33
. . 26
34-35, 40
34
daylight saving . . 37, 40
time meridians 35
Toadstools 398
Tobacco (effects of) . 432-433, 456
Tongue (organ of taste) . . . 413
Tools 459-461
development of .... 459-461
primeval 459
see also Inventions
Tornadoes (cyclonic storms)
230-231, 245
Torricelli (inventor of mercury
tube) 118
Touch (sense of) 413
Toxins 444
Trade winds 221, 245
Transference (of heat) . . 86-94
conduction .... 87-88,94
convection current . . 88-90, 94
radiation 90,94
Transmission (of water-pres-
sure) 147
Transpiration (evaporation in
plants) 106
Transportation . . . . . 167, 196
rivers as means of . . . . . 196
ocean as means of . . . . 167
Tropical calms 221
Trough (of waves) 157
Tsetse (carrier of disease) . . 452
Tuberculosis (bacterial disease) 442
Tungsten 488
Turpentine (a solvent) . . . 140
Twilight 3,355
Typhoid fever (bacterial disease) 442
Universe (of the ancients) . . 8
Uranus (a planet) . . . . 11,49
day on 12
distance from earth and sun 11
position in space determined
by laws of gravitation and
inertia 49
Valves (of heart) 413
Vaporizing (of water) .... 136
Vegetables 427-431
composition of 430
Veins (filled with minerals) . . 515
Veins (of leaves) 381
of dicotyledonous plants . . 381
of monocotyledonous plants . 381
Veins (of human body) . . . 409
capillaries 409
functions of 409
Ventilation .... 112^114,313
of houses 112-114
of soils 313
Ventricles (of heart) .... 412
Venus (a planet) . . . .5, 11-12
beauty and brilliancy of . . 12
day on . 12
distance from earth and sun 5, 12
Vertebrates 400
amphibia, birds, fishes, mam-
mals, reptiles 400
Vesta (an asteroid) .... 11
Vesuvius (a volcano) . . . 504-506
Monte Somma 506
Herculaneum and Pompeii 506
Vitamins 430-431,436
effect of heat upon .... 430
vital element of food . . . 430
Volcanic action . . . 155, 284-285,
503-515, 523
earthquakes 513-515
fault 513-514
geysers 511-513
islands 509
volcanoes . 284-285,503-511,523
Volcanoes 155, 284-285, 503-511, 523
cause of 503
craters of 503
distribution of . . . .508-511
eruptions as factors in sur-
face-changes . . . 284-285
eruptive matter . . 284-285,
504-506
loess beds 285
famous volcanoes . . . 504-510
Monte Nuovo 504
Mt. Lassen .... 509-510
Mt. Pelee 506-508
INDEX
25
References are to pages
Volcanoes — Continued
Vesuvius 504-506
on ocean floor 155
Volta (discoverer of voltaic cell) 484
Voltaic ceil (in electricity) . . 485
Volume 66,94
Vulcanite (in magnetism) . . 480
Water .... 98,100-107,127,
135-169, 170, 174-179, 196-207,
278, 311-313, 319, 324-327, 347,
385, 400-401, 425, 445, 447-449, 528
a disinfectant 445
a food 428
a necessity to life-processes
135, 425
a solvent .... 139-144, 167
air in 141
boiling-point of .... 100, 136
buoyancy of 148-151
composition of 135-136, 153, 167
condensation of 136
density of 137, 150
diffusibility 139
displacement on .... 149-150
effects of, upon life-develop-
ment 151-152
effects of varying tempera-
tures upon 136-138
energy in 137-138
erosive power of . . . . 278-280
evaporation of ... 101-107,
136, 166, 278, 385, 528
expansion of . . . 136-138,167
freezing of . . 138, 141, 167, 279
heat-absorption of . 138-139, 347
infection of . 205-206, 447-449
purification of polluted
water 205-206
life in . . . 151-152,400-401
of land due to ocean-evapo-
ration 166
physical properties of . . . 151
power of running . . . 174-176
pressure in . 146-148, 167-168
transmission of . 147-148, 168
qualities of 144
soil- .... 196-198,311-313,
319, 324-326
Water — Continued
solutions in . 141-142, 167; 278
sphere of activity of . 101-107,
196-206
evaporation .... 101-107
condensation into clouds 104
precipitation as rain. etc. . 104
run-off as lakes and rivers '
200-206
sinkage as artesian wells,
springs, etc. . . . 196-198
submergence in 150-151, 167-168
submarine . . . 150-151, 167
suspension of matter in . 142-144
temperatures of . . 136-133, 142,
167
of salt solutions .... 142
vaporizing of ... 98-100, 136
volume of 137, 167
Waterfalls 526
Waterspouts 231,245
Waterways . 17, 19, 152-167, 169,
171-174, 176-208, 213, 249-251,
256-258, 514, 531-535, 546-548,
552
as a means of development . 190
as a means of transportation 196
effects of, upon climate . 241-243
effects of, upon shores . . 243-244
day vs. night ; summer
vs. winter .... 243-244
Watt, James (inventor of steam
engine) 470
Waves. . . . 157-161,169,514
as builders and destroyers of
land 159-161
beaches 161, 251
cliffs, promontories, sea-
caves 160
crest of 157, 159
motion of water in ... 157—158
" oil on water " 158
trough of 157, 159
volcanic action vs 514
Wax 405,490
Weather . . . 209-237,244-245
temperature vs. 209-237, 244-245
circulation of air . 215-216, 244
winds. . . . 216-231,244
26
EVERYDAY SCIENCE
References are to pages
Weather — Continued
barometric pressure . 217
deflection of ... 217-220
warming of atmosphere
209-213, 244
altitude vs 212
clouds as heat-containers
210, 244
insolation .... 209-210
latitude vs 211
soil vs 212-213
Weathering (of rocks) . . 279-281
Wedge 469
Weight 66,94
Weight arm (in lever) . . . 464
Welding (by electricity) ... 487
" Westerlies " 224
Whirlpools 165
Whooping-cough (bacterial dis-
ease) 442
Winds. . .110,125,162-164,213,
215-231, 244-245, 279, 281-285,
470, 472
adiabatic cooling and heat-
ing, a cause of . . . . 125
affected by ocean-currents,
162-164
as carriers of deposition . . 285
Wind — Continued
as causes of surface-changes
281-285
as transformers of energy . 470
as weathering agency . . . 279
barometric pressure vs. . . 217
circulation of air
110,215-216,244
deflection of 217-220
direction of 217
Fen-el's law 219
planetary wind belts 220-228, 244
terrestrial 221, 245
storms 224-228,245
Winds, trade 221
Wireless (telegraph and tele-
phone) 495
Wood ashes (fertilizer) ... 317
Worms (invertebrates) . . 401-402
earthworm 401-402
Yeasts .... 303, 399, 422, 437
buds of 399
Yellow fever (protozoan dis-
ease) 401,452
Yellowstone Park (geysers of) . 511
Zodiac
9
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