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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 earth 1 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- 
gationAlkali 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 W T orld 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 W T ind 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- F IQURE 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 i s O f 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 P lete 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 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 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 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, w T hat 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 R OCK 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 cub j c j nch Q f 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. FI QURE 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 i n g 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- 
in g? 

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 C. into 
water at 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 T V 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 S lass P lu - 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. p IQUBE 
(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 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 JP IQURE 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 -22C. 
(-7F.) although pure water freezes at C. The freezing 
point of a salt solution may, therefore, be anywhere from 
slightly below 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 substance 4 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 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 

o c the work necessary for continued 

0< & O Q o$ existence there must be a dis- 

o? o *>o 00 oo o go Q tributory system. Thisisneces- 

^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 ? W T hat 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 \ 




0ygen 



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 w T as 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 Q UP 

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 are 4 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 |g r 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 ? ts b j f 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 = Trr 2 ) ; 
the surface of a sphere is four times the area of a circle through its 
center (A = 4 Trr 2 ). 



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 (?rr 2 ) 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 S6 1 00 
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, 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 | 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 nest r 
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 r V of 100,000, or 10,000 cu. ft. 
2d hand shows T V 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 T 7 ff 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 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 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 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. 

1 Wood 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 ri s ht - If & is the s P rin s 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 ... 407408 
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 . . 4455, 

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 . 344345 
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 ... 157158 

" 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 



YC VI027 






459964 




UNIVERSITY OF CALIFORNIA LIBRARY