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APPLIED SCIENCE

FOR

WOOD- WORKERS

WILLIAM H. DOOLEY, B.S., A.M.

* r

Principal of New York Textile School ; Principal Navy Yard Appren-
tice School under the New York City Board of Education; Formerly
Principal of the Technical High School, Fall River, Mass. ; Author of
••Textiles," " Boot and Shoe Manufacturing," "Vocational Math-
ematics for Boys," "Vocational Mathematics for Girls," "Principles
and Methods of Industrial Education."

/ ' 2

NEW YORK

THE RONALD PRESS COMPANY

1919

The Ronald Press Company

4. » to ■ • #

> • to • •

Man is weak of himself and of small stature.
He stands on a basis, at most for the flattest soled
of half a square foot insecurely enough, neverthe-
less he can us tools, can devise tools. With these
the granite mountains melt into light dust before
him; he kneads glowing iron as if it were soft paste;
seas are his smooth highways; wind and fire his un-
wearying steeds. Nowhere do you find him with-
out tools; without tools he is nothing; with tools he
is all. — Thomas Carlyle.

424811

PREFACE

This book and its companion volume for the metal-work-
ing trades, first cover the general principles of science common
to all industry, this material being identical in the two books.
Additional material follows this, that relating specifically
to the wood-working trades appearing in this volume, and
that relating particularly to the metal-working trades ap-
pearing in * ' Applied Science for Metal-Workers . ' ' The books
are constructed in this way to meet the needs of particular
industrial, trade, continuation, or apprentice classes where
the instruction is intensive.

Every craftsman should not only be trained in the handi-
craft of his trade, but, if he is to be a really skilled worker,
should also master the scientific principles involved; that is,
he should become familiar with the reasons underlying the
various operations which he performs. Such knowledge is
obtained through the study of industrial science. The teach-
ing of related trade knowledge is not, so far as the author
knows, adequately covered in any system of industrial
education.

Experience proves that, though the average pupil who
completes the regular high school course may know the
principles of the sciences in an abstract way, he is unable to
recognize these principles in operation in the every-day work
of the world. This fact is not surprising. Observation shows
that many minds are able to grasp a principle in the abstract
but are not able readily to apply that principle in practice.

vi PREFACE

Therefore, the study of the application of the scientific prin-
ciples underlying modern industry is worthy to be treated as
a special subject.

The author believes that there is a place for the traditional
course in chemistry, physics, and biology in the regular high
school, in addition to the first-year science course. He also
believes that there is a type of mind in our intermediate and
secondary schools that can profit by the study of the prin-
ciples of science underlying the fundamental trades. A
course of this kind should develop in a boy's mind that
attitude of alertness toward theory on which all sound prac-
tice is bas^d — a mental attitude which will be valuable to all
manual workers, and particularly to those who are to enter
the distributive or productive spheres of industry. Hence
the title of this book, " Applied Science for Wood- Workers"
the purpose of which is to provide an elementary course, in
applied science for the wood-working trades.

The author wishes to express his thanks to the following
firms who have furnished cuts and information: Dodge
Sales and Engineering Company, The Lincoln Electric Com-
pany, The American Injector Company, Brown and Sharpe
Manufacturing Company, Tolhurst Machine Works, Novo
Engine Company, Bailey Meter Company, Nicholson File
Company, The Bigelow Company, Ingersoll-Rand Company,
Babcock and Wilcox Company, American Steam Gauge and
Valve Manufacturing Company, Henry Disston and Sons,
Inc., The L. S. Starrett Company, Norton Company, Millers
Falls Company, Watson-Stillman Company, American
Radiator Company, Whitall Tatum Company, Eberhard
Faber, United States Department of Agriculture, Ameri-
can Screw Company, Edison Storage Battery Company,
Independent Pneumatic Tool Company, National Lead

SUGGESTIONS TO TEACHERS vii

Company, Riehle Brothers, National Carbon Company,
Inc., Southern Pine Sales Corporation, Worthington Pump
and Machinery Company, Western Electric Company,
Greenfield Tap and Die Corporation.

Acknowledgment is also made of indebtedness to those
teachers who have kindly read the manuscript and offered
valuable suggestions.

The author will be pleased to receive any constructive
criticism of the book.

William H. Dooley.

New York City,
August 15, 1919.

SUGGESTIONS TO TEACHERS

The arrangement of this book is such that it may be
used equally well by science teachers in the regular secondary
and technical schools and by science teachers in vocational
schools. When used in connection with a year's course in in-
dustrial science in the technical, industrial, or manual training
courses of regular secondary schools, it will aid in correlat-
ing the principles of science with shop observation and
experience.

The method of presenting the subject of industrial science
in a vocational school should be different from the method
used in the regular high school, since there is a wide difference
both in the aims of the courses and in the types of pupils. In
the vocational school it is well to consider first the practices
of the trades and industries as based on practical shop ex-

viii SUGGESTIONS TO TEACHERS

perience and laboratory work, and from them to draw out the
principles of science involved.

To illustrate: In considering the properties of matter in
oak wood, present first the uses of oak wood; it is used, for
instance, in the manufacture of furniture and refrigerator
cases. To be used for these purposes, it must be capable of
taking a high polish and of undergoing long usage — it must
be a hard wood. As Walter Dill Scott says in "Influencing
Men in Business": "Water is not adequately described by
stating that it is composed of two parts of hydrogen to ono
of oxygen. The important thing about water is the uses
which may be made of it."

This method will be found to be far more effective in teach-
ing vocational school pupils than that of presenting the
principle first and the illustrative practice afterwards

CONTENTS

Chapter Page

I. Science and the Properties of Matter 1

II. Weights and Measures 7

III. Mechanical Principles of Machines 22

IV. Leverage 26

V. Pulleys, Inclined Planes, and Wedges 35

VI. Laws of Motion 54

VII. Mechanics of Liquids 68

VIII. Properties of Gases 86

IX. Heat and Expansion 99

X. Light, Color, and Sound 113

XI. Principles of Chemistry 125

XII. Acids, Alkalies, and Salts 135

XIII. Physico-Chemical Processes 143

XIV. The Chemistry of Common Industrial Substances 156
XV. Magnetism and Electricity 167

' XVI. Frictional or Static Electricity 184

XVII. Generation of Electricity on a Commercial Basis . . 190

XVIII. Transmission of Electrical Energy 204

XIX. The Telephone and Telegraph 213

XX. Science Underlying Mechanical Drawing Supplies 225

XXI. Strength of Materials 233

XXII. Common Fastening Agents 249

Chapter
XXIII.

XXIV.

XXV.

XXVI.

XXVII.

XXVIII.

XXIX.

XXX.

XXXI.

XXXII.

XXXIII.

XXXIV.

XXXV.

XXXVI.

CONTENTS

Page

Common Hand-Tools 262

Transmission of Power 283

Boilers and the Generation of Steam 302

The Steam Engine 328

Methods of Heating 342

Ventilation 354

Gas Engines 359

Paints and Varnishes 369

Trees 390

Lumber 396

Defects of Woods 412

Hand Wood-Working Tools 417

Power Wood-Working Machines 432

Patterns, Cores, Flasks, and Molds 439

• «•••«. • «•. • * •

• •»*••*• • • !*
•••••••• . • •

* • • • ••*■• « •_ • • • •

APPLIED
SCIENCE FOR WOOD-WORKERS

CHAPTER I
SCIENCE AND THE PROPERTIES OF MATTER

1. What Is Industrial Science? — The practice of different
trades and crafts is based upon certain principles of science
which may be appropriately called applied science, industrial
science, or shop science. In the schools of college grade this
subject is called technology. While the names industrial
science and technology do not refer to any distinct science,
they may be said to cover that body of information — con-
sisting of some of the laws and principles of physics, chem-
istry, botany, bacteriology, geology, and hygiene — that
explain^ the practices of the different trades and industries.

2. Classification of Scientific Knowledge. — Physics is the
science which deals with those changes taking place in a
substance which do not destroy its identity. Physics ex-
plains the properties of matter, physical force, liquids, gases,
heat, magnetism, electricity, sound, and light. Thus, copper
is used in the form of sheets and wires. Therefore it must
possess properties that allow it to be hammered into sheets
and pulled or drawn into wire. Air may be compressed, that
is, "squeezed," into a small space and used to drive machines.
Liquids, on the other hand, are practically incompressible.

These are all physical properties.

*• • •

*Al¥Lf ED # SCIENCE

Chemt&irg' explains tfee'fchafigfe's that take place in a sub-
stance when its identity is destroyed. When iron, for
example, is exposed to damp air, it becomes covered with a
reddish brown substance called rust. This rust is due to
a combination of the oxygen and moisture of the air with
the iron. Copper or brass when exposed in this way becomes
greenish in color from the same cause. The science of
chemistry makes clear why such changes as these take
place.

Other sciences explain the why and wherefore of other
classes of phenomena or physical changes. Thus, botany
treats of the growth and changes in plants. Bacteriology
explains how changes in substances are caused by germs.
An example of such a change is the rotting of wood. Geology
treats of the structure of the earth, especially of rocks.
Hygiene explains the principles underlying the care of
our bodies. It is desirable to understand the principles
of science as they relate to the different trades, so that we
may have an intelligent knowledge of the processes and
changes whereby raw substances or materials taken out of
the ground are transformed into useful and beautiful things.

3. Properties of Matter. — Materials used in industry
are generally defined and described according to their
physical and chemical properties or characteristics. For
most purposes the chemical properties are not so important
as the physical, although in some cases the composition of
the materials must be taken into account. The chief prop-
erties of materials are cohesion, adhesion, inertia, elasticity,
ductility, brittleness, toughness, malleability, compressibility,
porosity, durability, infusibility, hardness. Some of these
characteristics, such as inertia, porosity, cohesion, and

SCIENCE AND THE PROPERTIES OF MATTER 3

adhesion, are common to all forms of matter and may be
considered as general characteristics. Others, such as brit-
tleness and ductility, which are found only in certain kinds
of matter, are called specific characteristics.

4. Cohesion, Adhesion, and Inertia. — The particles of
matter in solids and liquids are held together by a force
called cohesion. This cohesive force is stronger in some bodies
than in others. Sometimes the word tenacity is used instead
of cohesion. We may speak of a substance as possessing
great tenacity or great cohesion; such a substance is said
to be tenacious. Correctly speaking, tenacity is the measure
of cohesion.

The property of a substance which enables it to stick or
cling to another substance is called adhesion. Glue, for
instance, is held to wood by adhesion.

Inertia is the tendency of a body to retain its condition
of rest or of motion. The inertia of a hammer prevents
it from moving itself. A lathe tends to run after the
power is shut off.

6. Elasticity and Ductility. — When a carpenter bends
the blade of his saw and releases it, the saw blade tends
to return to its original position. This property is called
elasticity.

A substance is said to be ductile when it can readily be
extended or drawn out. Copper, because it possesses a
high degree of ductility, can be drawn out into wire.

6. Brittleness and Toughness. — When a substance breaks
easily under strain, it is said to be brittle. Glass furnishes a
good example of a particularly brittle substance.

4 APPLIED SCIENCE

Toughness, on the other hand, is that property which
enables a substance to resist cutting and to bear strain
without breaking.

7. Malleability and Compressibility. — A malleable sub-
stance is one which can be rolled or hammered into sheets
without breaking or cracking. Gold and silver both possess
a high degree of malleability.

When the particles of a substance can be forced to occupy
a small space, that substance possesses the property of com-
pressibility.

8. Porosity, Durability, and Infusibility. — Every body
of matter is composed of very fine particles that fill the
space occupied by the body. The particles of some bodies
are held more closely together than are those of others,
and we express this difference by stating that some bodies
are more or less porous than others. A body whose
particles are not very close together is said to possess
porosity. Unglazed earthenware will absorb water.

The property of a substance which enables it to withstand
long wear without decay or change is called durability..
Painted oak, for instance, is a very durable wood, as it will
stand a great deal of hard usage.

A substance which resists heat and will melt only at a
high temperature is said to possess the property of in-
fusibility. Platinum possesses a higher degree of infusi-
bility than any other metal. The following table shows
the order of malleability, ductility, tenacity, and infusibility
of the most common metals. Those possessing these
properties to the highest degree appear at the tops of the
columns.

SCIENCE AND THE PROPERTIES OF MATTER 5

Table Showing the Order of

Malleability

Ductility

Tenacity

Infusibility

Gold

Platinum

Iron

Platinum

Silver

Copper

Iron

Aluminum

Iron

Aluminum

Copper

Platinum

Gold

Tin

Gold*

Silver

Lead

Aluminum

Zinc

Aluminum

Zinc

Gold

Zinc

Platinum

Tin

Lead

Iron

Lead

Tin

9. Indestructibility of Matter. — While all forms of matter
may be changed or modified they can never be destroyed.
As an illustration, when sugar dissolves in water the particles
of sugar are so small or so minutely divided that they cannot
be seen. Yet they are not destroyed because they can be
recovered by boiling the water until it disappears in the
form of steam and leaves the particles of sugar behind. Or,
if wood or coal is burned and the ashes, vapors, and gases
that have come from it are collected and separated from the
gases of the air with which they have united during the pro-
cess of combustion, it will be found that the united mass of
the ash, gases, and vapors is the same as the mass of the
original piece of wood or coal. It is a fundamental principle
of science that matter is indestructible.

Questions

1. Is shop practice based upon any or many sciences?

2. Is it sufficient to know only the practice of the trade to be
a successful mechanic?

3. How will it assist a mechanic to know why he performs each
operation and uses each tool?

4. Does the average mechanic explain his work in terms of
science? If he does not, explain the reasons.

6 APPLIED SCIENCE

5. Name the branch of science that explains the reasons for
the following: iron rust; expansion of a metal by heat; freezing
of water; boiling of water; protection of body by rubber gloves in
working around electrical machines; finding lead in the form of
sulphides in the earth.

6. Of what use to a practical man is a knowledge of the physical
properties of water?

7. If the use of a material, such as copper (used in sheet metal
tanks and electric wires), is known, is it possible to state its physical
properties?

8. What are the physical properties of high-grade sheet metals?
Wire? Copper? Lead? Zinc?

9. Give the names and uses of some materials that are: porous ;
compressible; elastic; soft; hard; heavy; light.

CHAPTER II
WEIGHTS AND MEASURES

10. Units of Measure. — Since not all objects have the
same dimensions, it becomes necessary to have standards
with which different bodies may be compared. The three
fundamental units that are used in our daily experiences
are the units of time, length, and mass. Without these units
it would be impossible to do accurate work or to give and
receive working instructions.

The unit of time is the second and is the same in all coun-
tries. The day is divided into 24 hours of 60 minutes each,
and each minute contains 60 seconds. Twenty-four hours, or
one day, is the time taken by the earth to make one complete
revolution on its axis. In most trades the hour, minute,
and second are used in place of the day as the practical
working units of time.

The unit of length by means of which the English-speaking
races measure distance is the yard. The standard of length
in the British system is the imperial yard. It was defined
by an act of Parliament in 1855 as the distance between two
cross lines in two gold plugs in a certain bronze bar, kept at
62° Fahrenheit. This bar is preserved at the Board of
Trade office in London. Though the unit of length was
intended to be the same for England and America, in reality
the United States yard exceeds the British by .00087 of an
inch. The United States standard yard is the distance
between the twenty-seventh and sixty-third inch marks

8 APPLIED SCIENCE

of a scale prepared by the United States Geological Survey,
It is kept at the Bureau of Standards, Washington, D. C.
The foot is one-third of a yard, and the inch one thirty-sixth
of a yard. •

The units of area and volume are the square and the cube
of the unit of length, i.e., the square yard and the cubic yard.
The American unit of volume for liquids is the Winchester
wine gallon, which contains 231 cu. in.* The British unit
is 277.274 cu. in. A quart is one-
fourth, a pint (Fig. 1) one-eighth, and
a gill one thirty-second of a gallon.

The unit of weight, i.e., mass, is the
pound. This weight ia based on the
force of attraction exerted by the earth
upon a block of platinum called a
pound weight. This block also is kept
in the Board of Trade office in Lon-
don. The United States standard
weight is the avoirdupois pound which
is copied from the English measure.
Fig. 1. — Pint Graduate.
SSrSwt^S 1L Measurement of Distance.-
tions of a pint. The Distances of a few feet are usually
fs'tbe'symboL f or pin" measured with the ordinary foot rule
graduated in inches, and in halves,
quarters, eighths, and sixteenths of an inch. A carpenter's
wooden rule is made of boxwood, because of all woods this
is affected least by climatic conditions. Machinists' rules
(Fig. 2) are usually made of hardened steel and are graduated
to. a fine degree.

* The unit by which gas is measured ia the cubic foot. The unit
by which building materials are measured is usually the cubic yard.

WEIGHTS AND MEASURES 9

For convenience in carrying in the pocket, foot rules
(Fig. 3) are often made with hinged joints so that they fold
into a short length (4 in. or 6 in.) |i p i M i « | ™™ i pp iiiii: mnww
and longer rules are made in r^i y r 'T."L"xj.nLl.iIZ'i^ l .*ZI
multiples of a foot. Formerly Fig. 2.— A Machinist's Rule.
the most common rule used by

mechanics was the folding 2-ft. boxwood rule. Present-
day mechanics also uae this rule largely, but where greater
lengths are to be measured the zigzag folding rule is more
commonly employed. This latter rule folds into 6-in.
sections and may be obtained in
any length up to 10 or 12 feet.
The yardstick (3 ft. long), sub-
divided into feet, inches, and frac-
-Foldirig Rule. tionsof an inch, is also frequently
used as a unit of measure, es-
pecially for the measurement of textiles.

In building construction and timber measurements a
10-ft. pole is often employed. It is usually divided into
I-ft. sections, with the first foot subdivided into inches and
fractions of an inch. Long objects, such as steam pipes,
shaft lines, buildings, etc., are usu-
ally measured with a steel tape (Fig.
4). For ordinary purposes tape
measures are made of various ma-
terials, such as linen braid or steel
ribbon, in different lengths, and i
are graduated either in eighths or

sixteenths of an inch. The gradua- Fiu. 4.— Steel Tape.
tions are printed on the braid,

and the better grades are woven with wire selvages
or edges to prevent stretching. Spring-tempered steel-

10 APPLIED SCIENCE

ribbon tapes on which the graduations are accurately etched

are to be preferred for extremely careful measurements.

They are very convenient in measuring curvilinear or irregu-
lar surfaces, as is done in measuring the circum-,
ference of a gas tank, the length of a belt to run
over pulleys, or the length of band iron around
a -packing case. When using a tape measure for
any considerable distance, care should be taken
to see that the tape is supported at frequent in-
tervals or rests on the floor. Otherwise an error
will occur, due to the sagging and stretching of
the unsupported tape.
Pig. 5. Compass-like devices with curved legs, called

Calipers, calipers, are useTl to measure the diameters of

Formeuur- r0UI ,d bodies (Figs. 5 and 6).

mg inside °

meters. '*" * 2 - Mass and Weight. — Mass is the quantity
of matter contained in a body. When we speak
of a pound of lead, the word pound expresses a definite quan-
tity of matter. Commercially, weight
always stands for mass. A merchant
estimates his stock in pounds and usually
understands by those weights nothing
more than the quantity of matter pos-
sessed. The unit of mass is the quantity ,
of matter in a standard pound.

The weight of a body ?'s the measure of
the force attracting it towards the center of
the earth. Figure 7 illustrates the principle ^"SJSS
of ordinary weighing scales. outside diameters.

13. Density. — The simplest way to determine the weight
of a large body is to measure its volume and then multiply

WEIGHTS AND MEASURES 11

that by the weight of a unit volume of the substance. The
weight of a unit volume of any substance is coiled its density.

Fib. 7. — Weighing Scales.
These scales will weigh any body not more than
1 lb. in weight. Its scale is graduated in ten-
thousandths of a pound . Such scales are used for
weighing small articles, screws, samples of paper,
etc. The weights are in front of the scales. The
object to be weighed is placed in the pan.

The density of various substances has been compiled and refer-
ence tables have been prepared. The rule for determining the den-
sity of any substance may be written:

Mass or weight in pounds

Density —

Volume in cubic feet

It follows therefore that:

Weight = Density X Volume

Weight

14. Speed. — The distance over which a body passes in a
unit of time is called speed. Since the unit of space is usually

APPLIED SCIENCE

the foot, etc., and that of time usually the minute, it follows
that speed is measured in feet per minute, or in corresponding
units.

16. Table of Weights and Measures. — The English sys-
tem of weights and measures comprises the following tables
which are in daily use in the shop, mill, and commercial
work of America and England.

Long Measure

Troy Weight

12 inches = 1 foot

24 grains = 1 penny-

3 feet = 1 yard

weight

2 yards = 1 fathoir.

20 pennyweights = 1 ounce

16^ feet = 1 rod

12 ounces = 1 pound

4 rods = 1 chain
10 chains = 1 furlong

Cubic Measure

8 furlongs = 1 mile

1728 cubic inches = 1 cubic foot

3 miles - 1 league

27 cubic feet = 1 cubic vnrd

16 cubic feet = 1 cord foot

Square Measure

8 cord feet or ) , ,

*^« i .*..-= 1 <*>rd
128 cubic feet \

9 square feet = 1 square yard
30 J^ square yards = 1 square rod
40 • square rods - 1 squarerood
8 square roods = 1 acre
640 acres = 1 square mile
An acre is 208.71 feet square.

Land Measure

7.92 inches = 1 link
25 links = 1 rod

4 rods = 1 chain
80 chains = 1 mile

Circular Measure

Avoirdupois Weight

60 seconds = 1 minute

16 drams = 1 ounce

60 minutes = 1 degree

16 ounces = 1 pound

30 degrees = 1 sign

25 pounds = 1 quarter

60 degrees = 1 sextant

4 quarters = 1 hundred

90 degrees = 1 quadrant

20 hundreds = 1 ton

360 degrees = 1 circle

WEIGHTS AND MEASURES

Dry Measure

2 pints = 1 quart

8 quarts = 1 peck
4 pecks =■ 1 bushel

Liquid Measure

4 gills = 1 pint

2 pints = 1 quart
4 quarts = 1 gallon

Apothecaries Weight

20 grains = 1 scruple

3 scruples = 1 dram
8 drams = 1 ounce

12 ounces = 1 pound

Time Measure

60 seconds = 1 minute

60 minutes = 1 hour

24 hours = 1 day

7 days = 1 week

52 weeks )
12 calendar months > = 1

365 days J

Table of Quantities
12 units = 1 dozen

year

12 dozen

1 gross

20 units

1 score

24 sheets

1 quire

20 quires

= 1 ream

General Measure

A mile =

5280 feet

A cubit =

2 feet

A pace =

3 feet

A palm =

3 inches

A hand =

4 inches*

A span =

10?/£ inches

Wells and <

cisterns .hold for

each foot in depth:

Diam.

Gallons

2 feet

- 23

3 feet

- 53

4 feet

- 94

5 feet

= 147

6 feet

= 211

7 feet

- 288

8 feet

= 376

16. The Metric System. — The metric system of measure-
ment is French in origin and is largely used in Continental
Europe. It is the system used by nearly all scientific workers
and is finding more and more favor in this country. ' In this
system the unit of length is the centimeter, which is one-
hundredth part of a meter. The meter is one ten-millionth
part of the distance on the earth's surface from the equa-
tor to the pole. It is defined in the United States and
France as the distance on certain bars in Washington and
Paris which are kept at the temperature of melting ice. The
unit of weight is the gram, which is equal to about one-

14 APPLIED SCIENCE

thirtieth of an ounce. The unit of volume is the liter which is a
little larger than a quart. The gram is the weight of one cubic
centimeter of pure distilled water at a temperature of 39.2°
Fahrenheit; the kilogram is the weight of one liter of water;
the metric ton is the weight of one cubic meter of water.

The principal advantage of the metric system consists in
the use of decimal subdivisions and ease in calculations. The
principle of the metric system is sound, but since there is no
exact equivalent between the metric and English systems it is
difficult to use the former for practical purposes where ma-
chines and formulas have been made according to the English
system.

17. Table of Metric Measurements. — The metric system
of weights and measures comprises the following tables.
The symbols used to express the various units of measure-
ment in abbreviated form are also given:

Measures op Length

10 millimeters (mm.) = 1 centimeter (cm.)

10 centimeters = 1 decimeter (dm.)

10 decimeters = 1 meter (m.)

10 meters = 1 dekameter (Dm.)

10 dekameters = 1 hektometer (hm.)

10 hektometers = 1 kilometer (km.)

Measures op Surface (not Land)

100 square millimeters (mm.) = 1 square centimeter (sq. cm.)
100 square centimeters = 1 square decimeter (sq. dm.)

100 square decimeters = 1 square meter (sq. m.)

Measures of Volume

1000 cubic millimeters (mm.) = 1 cubic centimeter (cu. cm.)
1000 cubic centimeters = 1 cubic decimeter (cu. dm.)

1000 cubic decimeters = 1 cubic meter (cu. m.)

WEIGHTS AND MEASURES

Measures

Capacity

10 milliliters (ml.)

1 centiliter (cl.)

10 centiliters

1 deciliter (dl.)

10 deciliters

1 liter (1.)

10 liters

1 dekaliter (Dl.)

10 dekaliters

1 hektoliter (hi.)

10 hektoliters

•

1 kiloliter (kl.)

Measures

Weight

10 milligrams (mg.)

1 centigram (eg.)

10 centigrams

1 decigram (dg.)

10 decigrams.

1 gram (g.)

10 grams

1 dekagram (Dg.)

10 dekagrams

1 hektogram (hg.)

10 hektograms

1 kilogram (kg.)

18. Metric Equivalents. — The equivalent of the metric
units in English measurements and vice versa, carried out
when necessary to several decimal places, are given below.
The approximate English equivalent for the metric units
of measurement are found in the last table.

Linear Measure

1 cm. = .3937 inches (in.) 1 in.

1 dm. = 3 . 937 in. « .328 feet (ft.) 1 ft.

1 m. = 39 . 37 in. - 1.0936 yards (yds.) 1 yd.

1 Dm. = 1 .9884 rods (rds.) 1 rd.

1 km. = . 6214 miles (mi.) 1 mi.

Square Measure

1 sq. cm. =* . 1550 sq. in. 1 sq. in. =

1 sq. dm. =.1076 sq. ft. 1 sq. ft.

1 sq. m. = 1.196 sq. yd. 1 sq. yd.

1 are = 3.954 sq. rd. 1 sq. rd.

1 hektar = 2.47 acres 1 acre

1 sq. km. = .386 sq. mi. 1 sq. mi.

2.54 cm.
3.048 dm.

.9144 m.

.5029 Dm.
1.6093 km.

6.452 sq. cm.

9.2903 sq. dm.
.8361 sq. m.
.2529 are
.4047 hektar

2.59 sq. km.

16 APPLIED SCIENCE

Weights

1 g. - .0527 ounce (oz.) 1 oz. - 28.35 g.

1 kg. = 2.2046 pounds (lbs.) 1 lb. . - .4536 kg.

1 metric ton = 1.1023 English tons 1 English ton = .9072 met-
ric ton

Approximate English Equivalents

1 dm.

= 4 in.

11.

= 1.06 quarts (qt.)

1 m.

= 1.1 yds.

liquid .9 qt dry

1 km.

= h /% mi.

Ihl.

= 2<Hjbushels (bu.)

1 hektar

= 23^ acres

1kg.

= 2Klbs.

stere, or cu.

m. = M cord (cd.

) 1 metric ton

= 2200 lbs.

19. Care in Using Right Units. — In performing all cal-
culations care is required to see that the correct units are
used. Oftentimes, through haste and confusion, inches in-
stead of being first changed into feet are multiplied by
feet to obtain area in square feet. This error is often over-
looked because there are many formulas or rule-of-thumb
methods that have been abbreviated to their lowest terms
by cancellation so that in their final form it is possible to
multiply inches by feet or pounds. Therefore in using a
formula, care should be exercised to see that it is correct
and that the proper units are employed.

To illustrate: the formula for determining the thickness of a lead
pipe necessary for a given head of water is:

h Xs

750

where T is thickness of pipe in inches, 8 is size of pipe expressed
s decimal of an inch, and h is the head of water in feet.

WEIGHTS AND MEASURES 17

In this formula, feet are multiplied by a decimal of an inch. As
an example, the thickness of a half-inch pipe carrying a 50-foot
head of water would be:

m 50 X .5 25 1

T = = — = .033 in.

750 750 30

20. Precision of Measurements. — Mechanical problems
or operations usually consist of two parts: the collecting of
data, and the solving of the problem. Both of these opera-
tions require a basic knowledge of materials, considerable
judgment, and care for the accuracy of the work. One of
the most effective methods of checking measurements is to
take them twice, and then to arrange them in a systematic
and tabular form. To avoid errors, it is well to refrain from
using too many decimal places'. It is generally a good plan
to carry all calculations to one place further than that in
which accuracy in the final result is desired. For instance,
if it is desired to have a final result accurate to a hundredth
of the whole, the calculations should be exact to the thou-
sandth of the whole.

When one of a series of measurements has been taken
and the results recorded to three decimal places, the second
place of the decimals may be the same in all the measurements
but the third place may differ. In other words, the result
will be correct to two places, but the third place will be in
doubt.

The following plan may be used to determine the place that is in
error in the final product: Place a circle around the last digit that
is nearest to the decimal place which is the least accurate. In the
case of 6.845 X 4.5 this is .5.

18 APPLIED SCIENCE

6.845
4.6

34225
27380

30.8025

Since 6 may be in error, any part of the partial product involving
5 may also be in error. Therefore it is doubtful whether any figure
to the right of the first of the result (which is in doubt) should
be retained.*

21. Rules for Finding Area and Volume. — The forms of
most tanks, compartments, and mechanical parts are those
of simple geometrical figures such as squares, rectangles,
hexagons, ellipses, and circles. Every pupil should be able
to find the area and volume of such figures quickly and
accurately. The following rules will be of assistance:

Rules Relative to the Circle

To Find Circumference:

Multiply diameter by 3.1416
Or divide diameter by .3183

To Find Diameter:

Multiply circumference by .3183
Or divide circumference by 3.1416

To Find Radius:

Multiply circumference by .15915
Or divide circumference by 6.28318

To Find Area:

Multiply circumference by one-quarter of the diameter

* For a more extended discussion of practical mathematics see
" Vocational Mathematics," by William H. Dooley.

WEIGHTS AND MEASURES 19

Or multiply the square of diameter by .7854

Or multiply the square of circumference by .07958

Or multiply the square of one-half diameter by 3.1416

To Find Side of an Inscribed Square:

Multiply diameter by .7071

Or multiply circumference by .2251

Or divide circumference by 4.4428

To Find Side of a Square of Equal Area:

Multiply diameter by .8862
Or divide diameter by 1.1284
Or multiply circumference by .2821
Or divide circumference by 3.545

Square:

A side multiplied by 1.4142 equals diameter of its circumscrib-
ing circle

A side multiplied by 4.443 equals circumference of its circum-
scribing circle

A side multiplied by 1.1284 equals diameter of a circle of equal
area

A side multiplied by 3.545 equals circumference of an equal
circle

To Find the Area of an Ellipse:

Multiply the product of its axes by .7854

Or multiply the product of its semi-axes by 3.14159

Rules Relative to Other Geometrical Figures

Contents of cylinder = area of end X length

Contents of wedge = area triangular base X altitude

Surface of cylinder = length X circumference -f area of both ends

Surface of sphere = diameter squared X 3.1416, or = diameter

X circumference
Contents of sphere = diameter cubed X .5236
Contents of pyramid or cone, right or oblique, regular or irregular

= area of base X one-third altitude

20 APPLIED SCIENCE

Area of triangle = base X one-half altitude

Area of parallelogram = base X altitude

Area of trapezoid = altitude X one-half the sum of parallel sides

Questions

1. What measuring instrument is used to measure the length
of a 9-ft. plate? 36-ft. boat? 20-ft. wind-shield?

2. What measuring instrument is used to measure the width
of lumber? Length of bolts? Screws?

3. What measuring instrument is used to measure the diameter
of a cylindrical metal bar? Balls?

4. What measuring instrument is used to measure the inside
diameter of pipes? Elbows?

5. What measuring device is used in measuring the length and
width of a table?

6. A foreman desires to measure the length of the shop floor.
What measuring tool should he use?

7. What objection may be raised to measuring the length of a
school room with a 2-ft. rule?

8. An apprentice was told to obtain the diameter of a pulley
by measuring the longest distance across the pulley. Was this
instruction correct?

9. How may the diameter of a small iron ball be obtained
accurately?

10. Is there an exact number that shows the exact relation
between the meter and the foot?

11. Give the advantages and disadvantages of the metric system
of weights and measures. English system.

12. Explain some of the reasons why the metric system has
not been extensively adopted in this country.

Problems

1. What is the area of a square surface 14 in. on a side? Give
the area in square feet.

2. What is the area of a rectangular surface 1 ft. 5 in. by 8 in.?
Give the area in square feet.

3. What is the area of circular piece of metal with a diameter of
8 in.?

WEIGHTS AND MEASURES 21

4. What is the area of an elliptical shape with diameters
4 ft. 5 in. and 7 ft. 8 in.?

6. What is the volume of a cube 1 ft. 8 in. on a side? Give the
answer in cubic feet.

6. What is the volume of a rectangular tank 8 ft. 5 in. by 7 ft.
7 in. by 5 ft. 4 in.?

7. What is the volume of a sphere 8 in. in diameter?

8. What is the volume of a cylinder 14 in. high with a diameter
of 7 in.?

9. What is the area of a triangular surface, base 11 in. and
height 9 in.?

10. What is the circumference of a pulley that measures 24 in.
in diameter?

11. What is the side or thickness of a square bar, machine made
from 1J^ in. circular stock?

12. A square bar is 1^ in. thick, what size of circular stock
must be used to make it?

13. What are the contents of a wedge with a triangular base
of 14 sq. in. and 4 ft. high?

14. Give the area of the surface of a cylinder with diameter
7 in. and length 1J^ ft.?

16. What is the surface of a sphere in square feet with a
diameter of 11 in.?

16. What are the contents of a sphere with a diameter 4j/£ in.?

17. Give the contents in gallons of a conical-shaped vessel with
a diameter of 2J^ in. and a height of 1J^ ft.?

18. What is the volume in cubic centimeters of a tank
2 m. X 4 dm. X 5 cm.?

19. Give the English equivalents of the following dimensions
from a French blue-print: 1.7 m.; 26 dm.; 3 cm.; 5 mm.; 19 mm.;
24 dm.; 89 m.; 4 km.; 46 dm.; 7.9 m.

20. Give the metric equivalents of the following dimensions:
18 in.; 3 ft. 7 in.; 1 gal.; 7 qt.; 19 pt.; 5 ft. 9 in.; 2 l / 2 lbs.; 1 lb.
9 oz.; 1 ton; 34 oz.

21. A milkman charges 60^ a gallon for milk. What is the price
per liter?

22. A powder sells for 70^ a pound. What is the price per
kilogram?

CHAPTER III
MECHANICAL PRINCIPLES OF MACHINES

22. Why Machines Are Used. — The invention of ma-
chines is the result of man's desire to save labor and to econo-
mize in the use of his own strength by utilizing, where possible,
the natural forces of steam, wind, water, and electricity.
Man possesses only a certain amount of energy. If one man
works so fast as to exhaust himself by the end of the day,
he will not accomplish so much in the long run as the work-
man who utilizes a little less than half his natural strength,
and works at about one-third his greatest working speed.

Strength must be carefully distributed over the day's work,
to obtain the best results. A machine never tires and can
work almost constantly at its maximum practicable speed.
It is for this reason that machines and labor-saving devices are
continually being invented. These mechanical contrivances
are the result of the experiences of the human race. The
only tools that man possessed in the beginning were his hands
and his teeth. As time went on he found that his hands
and teeth were not sufficient, and he invented a club — a
form of hammer. At later periods axes of stone, copper,
bronze, and steel, and later the saw, plane, square, chisel,
and file were invented. All these tools resulted from neces-
sity, experience, observation, and the intelligent desire of the
human race to save itself labor and toil.

23. Tools and Machines. — Tools are simple machines.
When they become complicated they are called machines,

MECHANICAL PRINCIPLES OF MACHINES 23
and machines acting with great power take the name of

Workshop tools are divided into two classes, handWools and
machine tools. The former class includes hammers, chisels,
files, ratchet braces, span-
ners, etc. The latter class
includes lathes, planing,
ehapi ng,d rilling, andslottlng
machines, used in the fit-
ting shop; and punching and
shearing machines, bending
rolls, and steam hammers,
used in the smith's shop.
The compressed air at-
tachment (Fig. 8) is a good Flo 8 _ A ^ ^ {compreaaed

example Of a power tool. air attachment) tightening nuts

on a freight car. Compressed air
may be utilized in this way to
24. Force and Work.- SaS^SeSh""" "" ^
To understand the princi-
ples underlying the use of tools and machines, it is necessary
chiefly to understand the differences between force, work,
and energy. Force is that which tends to produce, to change, or
to destroy the motion of a body. The" force may be the strength
of man or animal, or of steam, or electricity, etc. Tools and
machines when stationary are in what is called a state of in-
ertia. The overcoming of resistance through any distance, such
as putting tools or parts of machines in motion, is called work.
Work is done when a force produces or destroys motion.

26. Estimating the Work Done.— In estimating the work
done two factors are employed — distance and force (weight)
— the units of which are the foot and the pound respectively.

24 APPLIED SCIENCE

The unit of work is the product of the unit of weight and the
unit of distance. When one pound is raised one foot (against
the force of gravity) it is called a foot-pound.

Therefore the weight in pounds multiplied by the distance in
feet gives th§ number of foot-pounds. By this means the energy
expended in lifting a weight is measured.

Pounds X Feet = Foot-Pounds
1 lb. X 1 ft. = 1 ft.-lb. (one unit of work)

When 847 lbs. is raised 12 ft., the work done is 847x12 =
10,164 ft.-lbs.

Power is the rate of doing work, or work done in unit time.
In other words, power is the number of foot-pounds of work
that can be done per minute or per second.

To illustrate : If a man exerts a force of 80 lbs. in pushing a wagon

60 ft. in one minute, the rate of doing work during that minute is

80 X 60 = 4800 ft.-lbs. If the same amount of work is performed

4800
in two minutes, then the rate of doing work is = 2400 ft.-lbs.

per minute. The unit of power is the horse-power (H. P.) 33,000
ft.-lbs. per minute, or 550 ft.-lbs. per second. Watt, years ago,
found this to be the rate at which an average horse can work, hence
the name.

Energy is the ability to do work, and is classified according
to its source — animal energy, mechanical energy, electrical
energy, etc.

26. Mechanical Principles. — A tool or machine is com-
posed of one or more of the following mechanical elements;
a lever, wheel and axle, pulley, inclined plane, wedge and

MECHANICAL PRINCIPLES OF MACHINES 25

screw. The force exerted on the mechanical principle is
called acting force or power, and that given out is called
weight or resisting force. We must bear in mind that none
of these simple machines or mechanical elements can gen-
erate energy, but that they enable energy to be distributed
and utilized to the best advantage. As an illustration, the
ability to work hard and without rest varies according to
the manner in which a workman applies his force, and the
number of muscles he brings into action. In the operation
of turning a crank, a man's strength changes in every part
of the circle which the handle describes. It is greatest when
he pulls the handle upward from the height of his knees,
and weakest at the top and bottom of the circle, where the
handle is pushed or drawn horizontally.

Questions

1. Is it possible to determine the degree of skill of a trade by
the number of tools used? Explain.

2. What impression would you gather from a person who was
driving carpet tacks with a machinist's hammer? Explain.

3. Is it economical to use a sledge hammer to drive ordinary
wire nails into a board floor? Explain.

4. State the kind of energy used in the following cases: (a) a
man lifts a casting from the floor; (b) a house is moved with horses;
(c) a grist mill grinds corn by means of running water back of the
mill; (d) a steam boiler drives the engine.

6. Has a mechanic more energy in the morning before going to
work than after a day's work? Explain.

CHAPTER IV
LEVERAGE

27. The Principle of the Lever. — Many tools are based
upon the principle of the lever. A lever is a rigid bar, straight
or bent, free to turn about a point called a fulcrum. Levers
are generally divided into three kinds or classes, the class be-
ing determined by the position of the fulcrum in relation to
the applied force or effort and the resisting force, i.e., the
weight. The mechanical principle of the lever was discovered
by a Greek named Archimedes^ who lived in the third cen-
tury. He stated that if he had a lever long enough and a
place to stand, he could move the earth.

28. Mechanical Advantage. — Since a lever is a tool, ics
object is to assist in distributing strength or speed to the best
advantage. Suppose a lever is used in moving a heavy stone.
By what means can the amount of assistance rendered by
it be determined? This assistance, called the mechanical
advantage, is obtained by dividing the force arm or effort arm
(the perpendicular distance from the fulcrum to the direc-
tion of the force), by the weight arm (the perpendicular dis-
tance between the fulcrum and the weight), or by dividing
the resistance or weight by the effort or applied force. In other
words, there are two ways by which a lever can be made
to be of more service: first, by lengthening or increasing the
force arm ; second, by shortening or decreasing the weight arm.

If a mechanic, for example, desires to have more advantage,
or, as he usually says, more "leverage," he may increase the
length of the force arm by taking a tool with a longer handle.

LEVEKAGE 27

29. Moment of Forces. — All problems in leverage may
be solved by arithmetic and without using a model.

Suppose that two weights are balanced as in Fig. 9 at the

distances shown therein. u t8 . f n .

As 11 times 18 equals 12 U | 1 1

times 16J^ (198) it fol-
lows that the weight of one

Mil lbs

side times its distance from FlG . 9._The Moment of Forces.

the fulcrum is equal to the

weight on the other side times its distance from the fulcrum.

W X D = W X D'

This rule always holds true for all classes of levers. If,
therefore, the amount of both weights and one distance are
known, the other distance can always be found; or if any
three of the four quantities are known, the fourth can always
be found. As an example, if we know all but the 16^ lbs.
in Fig. 9 we can find this figure in the following way:

18 X 11

= 16^ lbs.

In all classes of levers the weight or force times its perpen-
dicular distance from the fulcrum is called the moment

Thus in the above problem, 12 X 16}^ is one moment and
18 X 11 the other. As another example: What force will balance
a weight of 100 lbs., 12 in. from a fulcrum located at the short end
of a lever? The long end of the lever is 24 in. in length.

100 X 12 = moment of acting force
W X 24 = moment of resisting force

But, when a lever is balanced, the moments of forces are equal,
according to the rule explained above.

28 APPLIED SCIENCE

W X 24 - 100 X 12
24TT - 1200
W = 50 lbs.

That is to say, it will take 50 lbs. at the long end of the lever to
balance the 100 lbs. at the short end.*

30. Levers of the First Class. —

In levers of the first class, the fulcrum

Fig. io.— A Lever of the is placed between the acting and re-
First Class. sisting forces as shown in Fig. 10.

This figure illustrates the lifting of a heavy block by means of
a crowbar and a support.

E = Effort
F = Fulcrum
W = Weight

By pressing down the end of the bar E the other end of the lever
raises the weight W and the center of motion is at the fulcrum F.
In other words, the applied force E acting on the lever supported
by the fulcrum F overcomes the resistance, called weight W.

The force of the lifting power of the lever increases in
proportion as the distance of the effort E from the fulcrum
increases, and diminishes in proportion as the distance of
the weight W from the fulcrum increases.

* It should be noted that when leverage problems are figured
by arithmetic no account is taken of the weight of the lever itself.
The results obtained by using simply weights and distances are
exact enough for all practical purposes. If the designer had to
allow for the weight of the lever itself, he would have to make a
long and difficult calculation. Such allowance, however, is not
necessary because, for safety, all parts of machinery are made at
least five times as strong as they need to be.

LEVERAGE 29

31. Examples of Levers of the First Class. — Another
example of a lever of the first class is the use of the fire poker
with the bar of the grate serving as a fulcrum. When a
lever consists of two parts fastened by a rivet, it is called
a double lever. Scissors, pincers, and forceps are all examples
of such a lever; the rivet serves as a fulcrum.

The scale beam used in weighing is also a simple lever.
The arms on each side are of equal length and are suspended
over the center of support. The axis at the point of suspen-
sion is sharpened to a very fine, sharp edge, so that when
weights are placed in the scales, the beam may turn with as
little friction as possible. When the arms are not of equal
length, the scales cannot weigh accurately, although the
beam may seem fairly balanced and the weights true. If
one arm is 8 in. long and the other only 7}^ in. the scale will
balance with a 1-lb. weight on the short arm and 15-oz. on
the long arm. Thus the customer of a merchant who uses
such a scale loses an ounce in every pound. The deceit can,
of course, be discovered by changing the weight and material
to the opposite scales. In some cases where the beams of
scales are not accurate, the articles to be weighed are put
in one pan and balanced by weights; the article is then put
in the other pan and balanced again. The correct weight
is found by taking the square root of the product of the two
weights.

32. Levers of the Second Class. — In the second class
lever the weight and force are on the same side of the ful-
crum, the weight being placed between the force and the
fulcrum.

For example, if a mason desires to move a large piece of stone
forward, instead of bearing down upon the lever to raise the stone

APPLIED SCIENCE

Fkj. 11. — A Lever of the Second
Class.

up a little, he sticks his crowbar into the ground under the stone
and at the" same time pushes forward (Fig. 11). In this way he

moves the stone onward little by
little, the ground being the fulcrum.
The same principle of leverage ap-
plies to the opening of doors or box
covers. The oars of boats and the
masts of a ship in which the cargo
acts as resistance, the bottom of the
vessel as the fulcrum, and the sails
as the moving power, are also levers
of the second class. Nutcrackers
(Fig. 12), lemon-squeezers, and de-
vices consisting of two legs joined
by a hinge are further illustrations of this class of levers.

33. Levers of the Third Class.— la the third type of
lever the fulcrum is at one end, the
weight at the other, and the force
is placed between them (Fig. 13).
The advantage of this arrange-
ment is that a small force causes
the extreme point of a long arm to move over a great space.

The mechanism of the muscles acting on the bones illustrates
1^ ! this form of lever. The

7 fy n ) elbow or joint is the ful-

- l crum, the muscle the mov-
ing power, and the weight
raised the resistance. The
muscles of large migrating
birds, for example, must be

Fig. 12. — A Nutcracker.
An example of a lever
of the second class.

Fig. 13.— A Safety Valve.
A lever of the third class.

very powerful in order to sustain the weight of their bodies while
they travel for days.

34. Compound Levers. — Levers are said to be com-
pounded or compound when their free ends are joined to the

LEVERAGE

Fig. 14. — Compound Levers.

free ends of other levers. Large scales used in weighing
luggage, bricks, wagon loads, and so on, consist of an arrange-
ment of compound levers, ^ _ . , _ ,
whereby the arm on one ,,<^3$fcz T rrr U P
side of the fulcrum is
lengthened and the arm
on the other side is short-
ened. The brake rig-
ging on locomotives and cars is a familiar example of a
compound lever.

Two or more levers joined and working together (Fig. 14) il-
lustrate this principle of leverage. Here a weight suspended on a
hook at W causes the end of the second lever P to swing downward.

35. Problems in Compound Leverage. — Problems in
compound leverage are easily reduced to repeated cases of
simple leverage, the force at the end of the first lever being
the weight or force applied to the second lever, and so on
through any number of levers.

As an example: If the force at W in Fig. 14 is 12 lbs., what is
the force at Pf •

For the first lever the force pushing up at the end of the long arm

is: = 3 lbs. For the second lever it is: = % lb.

12 12 4

While the safest way is always to figure each lever as a simple

lever, as just explained, a shorter method of obtaining the answer

is as follows:

Multiply the weight by the continued product of the short arms of
all the levers, and divide this by the continued product of the long
arms of the same levers.

32 APPLIED SCIENCE

Applying this rule to the above problem we have

12 X 3 X 3

12 X12

-5* lb.

The answer is the same as before, and after a little thought it is
evident that the two steps in the first case have merely been put
together in one expression in the second case. If the weight, %
lb., on the long end of the second lever at P is known (see Fig. 14),
and the pressure or weight which would be needed at W is to be
found, the same rule will apply but will be expressed in this man-
ner: Multiply the weight by the continued product of the long arms
and divide this by the continued product of the short arms:

3 12X12

— X = 12 lbs.

4 3X3

Regardless of how many levers there are working together,
the rule is applicable. In all leverage problems the first,
and the most important, thing is to find and locate the ful-
crum, as the fulcrum is the point which determines the
moment arms from which the required answer is obtained.
The moment arm is always the perpendicular distance from
the force or weight to the fulcrum.

36. Shapes of Levers. — The fulcrum of levers used in
machinery is usually cylindrical in shape, made of soft

metal, and supported in the in-
terior of a cylindrical opening in
which the lever works, so as to
reduce the friction. The lever is
Fig. 15.— A Bent Lever. not only oscillating or vibrating,

but where the motion is circular
the fulcrum becomes the axis of rotation.

LEVERAGE

A bent lever (Fig. 15) is often used for peculiar circum-
stances, but it acts obliquely and, consequently, with less
effect.

The rules of leverage apply with equal accuracy whether a lever is
straight or bent at an angle. Take, for example, the lever shown
in Fig. 16. This lever, it will be noted,
has one arm bent up at a right angle
to the other and a weight hung on
the horizontal arm. Imagine a force
applied at the end of the vertical
arm as shown. It is plain that the
weight W times its distance A from

the fulcrum is equal to the force F j lst\1\ _gC

times its distance B from the fulcrum, ^ ™ v

just as if the lever were in the same
straight line.

jkeE4^

It is, of course, understood that Xi&^SStartte
in all leverage problems the force

must always be at right angles to the arm. Therefore,
while the weight acts vertically, the force acts in a horizontal
direction. The lever is bent up as the direction of the force
on the end that is bent is thus changed.

Questions

1. Draw a sketch of a hammer removing a nail from a board.
Where is the fulcrum? What class lever is it? Why?

2. Draw diagrams of the three classes of levers and give an
example of each kind.

3. Name some examples of bent levers.

4. Give three examples of compound levers.
6. Define fulcrum, force arm, and weight arm.

6. Will a mechanic who knows why he performs each operation
of his trade enjoy his work better than one who does not? Explain.

34 APPLIED SCIENCE

7. Explain why some hammers are large, some small, and of
different shapes.

8. Is it necessary to know the principles of science in designing
a tool?

9. What would happen to a mechanic if he used a hammer
four times as heavy as necessary? Would he accomplish as much
work with the large hammer as the small hammer (assuming the
small hammer will do the work effectively)?

10. Why not use a claw hammer in driving tacks into the floor?

11. Name a number of "hitting tools." Notice the manner in
which they are used. Is it practically the same? What is the
mechanical principle involved?

Problems

1. Take a yardstick and balance* it in the middle. Where is
the fulcrum?

2. If a 2-lb. weight is attached 7 in. from the fulcrum, where
should a 3-lb. weight be placed to balance it? Draw a sketch.

3. Examine common tools and devices, such as scissors, pliers,
tack-lifters, lemon-squeezers, nutcrackers, can openers, pokers,
etc., and measure the force arm and weight arms.

4. What is the weight or lift produced on a pump handle that
has a weight arm of 5 in. and a force arm 21 in. long when 25 lbs.
is applied at the handle? Draw a sketch.

6. A safety valve on a stationary boiler is loaded with a 50-lb.
weight at W (Fig. 13). Distance F P is 4 in., P W y 12 in. Find
the total steam pressure necessary to open the valve.

CHAPTER V
PULLEYS, INCLINED PLANES, AND WEDGES

37. Simple Form of Pulley. — The pulley is a machine
which in its simplest form consists of a grooved wheel, made
of wood, brass, or iron, with a rope or chain passing over it,
fixed in a framework, and free to revolve.
As the type of pulley shown in Fig. 17 j
turns on an axle fixed in one place it is
called a fixed pulley.

Such a device makes it easier for a man stand-
ing on the floor to raise a weight by pulling
on the end of the cord at P than if he
pulled the weight straight up by the cord with-
out any pulley, or carried the weight up a flight
of stairs.

A pulley may be considered as a rotating lever
which is used simply to change the direction of

a force. The belt or rope does the work, not F IG .i7. a Fixed

the wheel. There is no leverage in a single fixed Pulley,

pulley, and if the weight is 50 lbs., it takes a pull
of 50 lbs. at P (ignoring the slight friction of the wheel axle) to
raise it. In Fig. 17 the lever arms in the pulley are equal to
the radius and the fulcrum is at the center; that is, in a pulley
16 in. in diameter one arm would be 8 in. on one side and the other
8 in. on the other side of the fulcrum.

38. Block and Tackle. — The advantage of the single pulley
may be increased by combining several pulleys, as is done in
the case of the appliance called the block and tackle.

36 APPLIED SCIENCE

Figure 18 shows the arrangement of a single pulley block or shop
tackle, consisting of one fixed pulley in the upper block and a raov-
, ....mm - aD ' c one m the lower block. One end of the rope
ifonVrivi ' s fastened to the upper block. This arrange-
■-•Jfc '. i OQ! incnt is merely a single movable pulley with its
roj>c extended up and around another pulley, thus
j enabling the operator to pull down when raising
the weight. The upper pulley therefore does not
l£ affect the amount of the force, but merely
changes its direction from a pull-up to a pull-
down on the rope. The advantage of this type
of block and tackle is that the force is decreased
one-half, while the space the worker pulls through
is twice that of the movement of the weight.
IV is 100 lbs.; the worker has only to lift 50 lbs.;
to raise the weight 1 ft. he must draw up 2 ft. of
rope, that is, one on each side of the pulley. With-
out the pulley he would have 100 lbs. to raise 1 ft.

Increasing the number of pulleys decreases the weight per
strand, and allows a
smaller force to overcome
a larger at the expense of
space and low of time.
(Fig. 19.) The pulley
ropes used arc called
tackle, and the pulley,
a block. A number of
pulleys placed together
occupy much space and
are inconvenient to han-
dle. To avoid this, and
al the same time obtain
the required mechanical
advantage, it is commou to have several pulleys, called

1*). — Series of Pulleys,

Fia. 20.— A Dumb-Waiter Pulley.

PULLEYS, INCLINED PLANES, AND WEDGES 37

sheaves, assembled in one block on the same pin. Some-
times three, four, or more sheaves are placed thus side by
side, a strong pin
serving as an axis.
In this way a force
can move two, three,
or four times its own
resistance. Thus in a
three-sheaved mov-
able block, 100 lbs.
would balance 300 lbs. Since the entire movement of the
pulley is made up of a series of stops and starts, the movable
pulley acts during its
motion on the principle
of a lever of the second
class. As a result, the
force applied times the
diameter of Ike pulley
wiU always equal the
Fig. 21.— Tackle or Awning Pulley. weight lifted times the

radius of the pulley.
Figures 20, 21, and 22 show common forms of pulleys.

Problems on Pulleys

1. How much pull at P would be required to lift 150 lbs. at Wf
(Fig. 18.)

2. What force at W would just balance 200 lbs. at Pf

3. With what force or how many lbs. is the rope C pulling on
its fixed end when 300 lbs. is being lifted at Wf (This force or pull
is called the tension at C.)

4. If a rope is carried around six pulleys as shown in Fig. 19
and a pull of 100 lbs. is exerted at P, what weights would be lifted
bA A, B, and Ct

38 APPLIED SCIENCE

6. How far would the three lower pulleys and frame be raised
if the rope at P is pulled down 6 ft.?

6. How does the force of the arrangement shown in Fig. 19
differ from the force obtained from a block and tackle having
three pulleys in each block (neglecting friction)?

Fio. 22. — Use of a Single Pulley. Double-platform material
elevator for lifting materials to a building. One elevator
goes up while the other comes down, so that only force
enough to lift the actual load ia required.

39. Wheel and Axle. — The study of pulleys and tackles
leads naturally to that of the wheel and axle, which consists
of a wheel or crank attached to an axle. The weight is
lifted or moved by means of a rope, belt, or chain running
over the axle. The force is applied to the rim of the wheel.
In previous problems the pulleys have all been of equal
diameters, and operated by cords or ropes, but the wheel
and axle may be considered as fixed pulleys of different
diameters fastened on a shaft, the larger pulley being the
wheel, and the smaller pulley the axle.

PULLEYS, INCLINED PLANES, AND WEDGES 39

The principle of the wheel and axle is very important,
since a great many machines, such as derricks, cranes, eleva-
tors, steam shovels, etc., are con-
structed on this plan.

Figure 23 shows the simplest form
of wheel and axle, in which A is the
wheel and B the axle or drum. If
a weight P is hung from a cord
wound on A it will wind up a certain
weight W on drum B.

Fi«. 23.— Wheel and Axle.

40. Comparison with the Pulley. — In theory the wheel
and axle is nothing more than a single movable pulley, which
instead of being a lever of the second class, and always lift-
ing the weight exactly at its center, is a lever of the first
class and lifts the weight some distance off the center. A
single movable pulley moves the weight in the same direc-
tion in which the rope is pulled, but the Vheel and axle
moves the weight in the opposite direction from which the
rope is pulled. The lengths of rope wound or unwound
from the wheel and axle are always inversely proportional
to the weights raised or lowered.

Problems on Wheel and Axle

Note carefully in all problems on the wheel and axle that more
force is required the faster the weight is lifted. Moreover, if the
axle is made smaller, the weight will be lifted more slowly and less
force will be required.

These same principles are true in the case of pulleys and tackles.
In fact, it will be found that in all machinery it takes more force
to do work quickly than to do it slowly.

1. Figure 24 shows a common winch or hoist which is a good
illustration of the wheel and axle; the crank is the wheel and the

APPLIED SCIENCE

Fig. 24.— Hoist.

6-in. drum is the axle. If a boy turns the handle P uniformly
with a force of 50 lbs., what weight can he lift at Wl

2. Suppose in problem
1, 15% were lost in friction,
what would be the answer
to the problem?

3. If 26 ft. 8 in. of rope
were wound up on the drum
in Fig. 24, how many turns
and parts of turns did the
crank P make? (Take

'* = 7 •)

4. In Fig. 24, what is the ratio between the weight lifted and
the force applied?

5. A wheel and axle has the wheel 24 in. in diameter and the
axle 12 in. in diameter. If 10 ft. of rope are wound up on the wheel
how many feet will be unwound on the axle?

Note. — To do this problem it is necessary only to consider the
circumferences of the wheel and the axle. One turn of the wheel
will wind up 3.1416 X 24 in. of rope and at the same time unwind
3.1416 X 12 in. t)f rope from the axle. This is the same as saying
that the lengths of cord wound and unwound are proportional to
the circumferences of the wheel and axle. But we already know
that the circumferences of circles are proportional to their diameters
and so we can say that the lengths of rope wound and unwound are
proportional to the diameters of the wheel and axle and in the
above problem we will have,

24 : 12 = 10 : rope unwound from axle.

12 X 10

f> ft. rope unwound from axle.

A simple rule for this would read: To find the length of rope un-
wound from the axle multiply the length of rope wound on the wheel
by the diameter of the axle and divide this by the diameter of the wheel.

If we wanted to find the length of rope wound up on the wheel
the rule would read: To find the length of rope wound on the wheel

PULLEYS, INCLINED PLANES, AND WEDGES 41

multiply the length of rope unwound from the axle by the diameter of
the wheel and divide by the diameter of the axle.
Or in the above problem,

= 10 ft.

In the derrick (Fig. 25), the hoisting mechanism is a form
of double wheel and axle in which the axle of the first works
upon the wheel of the second by
means of gears. It is used for
raising heavy weights.

41. Inclined Planes.— Another
simple machine, called an inclined
plane, is a slope used to enable
a small force, such as the strength
of a man, to overcome the weight
of a large body. When, for ex-
ample, it is necessary to move
heavy boxes, barrels, etc., from a
sidewalk to a wagon or from a ... ... ,. . .

wagon to the sidewalk the team-
ster usually places a plank between the two distances, thus
making an inclined plane and pushes the barrel or box onto
the wagon. If a wagon bed is 4 ft. above the ground and
a board 8 ft. long is placed against, it, a man can then roll
the barrel up the inclined plane with one-half the force he
would have to exert when lifting, but in twice the time, as
the distance covered is twice that of the vertical or upright
height.

The mechanical power gained on an inclined plane is

APPLIED SCIENCE

equal to the quotient obtained by dividing the length of
the plane by the height. To illustrate: If a barrel weighing
300 lbs. is to be rolled onto a wagon 4 ft. from the ground
and a plank 12 ft. long is used, a strength or force of 100
lbs. would balance the barrel, because the inclined plane is
three times the perpendicular height. A slight force over
the 100 lbs. would move the barrel.

Roads constructed to the tops of hills are either wound
round and round, or made so broad that a person or driver
of a vehicle can wind from side to side in climbing the hill.
In building houses, an inclined plane in the form of a plank
walk is used to facilitate the transit of wheelbarrows in and
out of the building. The stairs of a house form a steep
inclined plane on which the steps enable one to secure a
firm footing.

ball A

42. An Example of the Inclined Plane. — Figure 26 repre-
sents an inclined plane supporting a ball A which is free to roll

on an axle through its center.
" A cord attached to the yoke
of the axle passes over a
guide pulley B to a counter-
weight W. The weight W
is then pulling against the
ball in a direction parallel
to the face of the plane and
is preventing the ball from
rolling down.

Now it is easy to see that the weight W does not need to be
so heavy as the ball to keep the ball from rolling, since part of
the weight of the ball is supported by the plane. In other words,
the ball naturally tends to fall straight down in the direction of the
dotted line XY, just as though it were dropped from the hand
and fell to the floor.
By a diagram of similar triangles, it can be proved that the

Fig. 26. — Inclined Plane.

PULLEYS, INCLINED PLANES, AND WEDGES 43

length and height of the inclined plane are proportional *o the
weights A and W. For example, if in Fig. 26 we make the height
of the plane 1 ft. and its length 2 ft., we know that the weight W
need only be one-half as heavy as the weight of the ball to keep it
from rolling down the plane. Stated as a proportion this would be,

Weight A : Weight W = 2 ft. : 1 ft.

We will now study the relative movements of the weights if the
height of the inclined plane is one-half its length. In Fig. 26 when
the ball rolls from the top of the plane to the bottom it has traveled
2 ft. on the plane but has dropped only 1 ft. in a vertical direction.
By this we know that the distance the ball travels on the plane is
to the vertical distance it moves through as 2 is to 1, when the
height of the plane is one-half its length.

It has now been proved that there is a definite ratio or relation
between the height and length of the plane and the weight of the
ball and counterweight, and also between the distances the ball
moves along the plane and perpendicular to it. Whatever the heigh t
or length of the plane, these relations always hold true.

From what has been explained, short, simple rules can be
made for problems relating to inclined planes as follows:

I. To find the counterweight or force, multiply the weight
on the plane by the height of the plane and divide by the length
of the plane.

II. To find the weight on the plane, multiply the force
by the length of the plane and divide by the height of the plane.

Problems on Inclined Planes

1. Neglecting friction, what force is necessary to keep a weight
of 100 lbs. stationary on an inclined plane, the perpendicular height
of the plane being 4 ft. and the length of its incline 14 ft.?

2. The length of an inclined plane is 15 ft. and its height 7 ft.
What weight will a power of 78 lbs. sustain on the plane, neglecting
friction?

44 APPLIED SCIENCE

43. The Wedge. — A combination of two inclined planes
joined at their bases is called a wedge. This simple machine is
used to split wood, rocks, etc., and to raise heavy weights short

distances. The power of the wedge cannot
be accurately estimated, as the force, number
of blows, and incline all have to be taken into
account. In splitting wood (Fig. 27), the
sides of the opening in the log act as levers,
and thus force the mass apart in advance
of the point of the wedge. More power is
gained by striking the head of the wedge
with either a small or a large hammer, than

Fig. 27.— Wedge, by pressure, as the momentum of the blow

tends to shake the particles of matter and

cause them to separate.

The lifting power of the wedge is utilized in dockyards, where
large vessels are raised by its agency. The heads of hammers are
fastened on by wedges driven in at the part of the handles near
the heads. Nails, knives, needles, razors, hatchets, chisels — all
act on the principle of wedges. A saw in motion represents a series
of wedges which are drawn along and pressed on the object to be
cut. When the edge of a razor is examined by a microscope, it
is seen to be sawlike in formation; by being drawn along the
beard, it cuts off the hairs.

44. Application of the Principle of the Wedge. — Just as
the power of the inclined plane is proportional to the height
and length of the plane, so is the power or force applied to
the wedge proportional to its height and length. In this
latter case, however, the length is the horizontal length or
base ac (Fig. 28) and not the sloping face bg. By the prin-
ciples of similar triangles, we can easily prove that when a
force acts in a direction parallel to the base of a wedge, the

PULLEYS, INCLINED PLANES, AND WEDGES 45

wedge will lift a weight as many times greater than the force,
as the base or length of the wedge is times as long as the
vertical face or thickness This may be
stated as a rule as follows:

To find the force required to lift a certain
weight multiply the weight by the greatest
thickness of the wedge and divide by the
horizontal length. „__^^

On the inclined plane previously described p IG 28. Lifting

the force acts in a direction parallel to the Power of Wedge,
plane; that is, the cord attached to the
ball pulls up the plane. In Fig. 28 a weight W is being lifted by
driving two single wedges. To raise the weight we must strike
or push on the face of either one of the wedges, as at F on the face
ab. This force acting parallel to the base ac of the wedge causes
a pressure P in a direction at right angles to the base.

Problem on the Wedge

A single wedge is 2 ft. long and 4 in. thick. What force must
be applied to it to lift a weight of 600 lbs., neglecting friction?

46. The Principle of the Screw. — The screw possesses great

industrial utility in pressing bodies together
or in raising weights, and may be classed
among the simple machines. The screw is
an inclined plane, and the effect of a screw is
produced when such a plane moves spirally
around a cylinder. This movement may
be illustrated by cutting out a wedge-
shaped piece of paper and wrapping it
FlG % 2 3*~Tp rmc,ple about a round stick or bolt. The sloping

of the Screw.

side draws a thread on the stick as in

Fig. 29. This thread is called a helix (Fig. 30).

APPLIED SCIENCE

HANMU

It really makes no difference in the result whether the
inclined plane is wound in a spiral or circular path, or left

straight; the wedging action will be there
just the same. This means that all screw
threads, nuts, bolts, etc., are circular or spiral
wedges. The ease with which a screw turns
and ascends depends on the slowness of the
ascent, that is, on the number of turns, or threads, in a given
distance.

-T— j JMUA0

Fig. 30.— Helix.

46. Jack Screw. — The ordinary jack screw is a good
example of the wedge principle. It is a screw in combination
with a lever.

Figure 31 shows a common jack screw. The thread is the inclined
plane or wedge and the circumference of the screw or thread cor-
responds to the base of the plane. The
force P on the handle is the force acting
parallel to the base and the weight W is
the weight lifted. The same rule which
is used for the wedge will now apply. If
the length of the handle, the pitch of the
thread (the distance between two succes-
sive threads), and the force applied to the
handle are known, the weight which can * IG * 31 - ^ ac ^ ^ crcw -
be lifted, neglecting friction, can easily be calculated.

Referring to Fig. 31, for every turn of the handle the weight is
raised an amount equal to the pitch :

P XC = W XV

where P, W, and p are as shown in the sketch and C is the circular
distance the end of the handle moves through in making one turn,
or

C = 2 x It

PULLEYS, INCLINED PLANES, AND WEDGES 47

Problem on the Jack Screw

A jack screw has a single thread, seven turns to the inch, and
a handle 18 in. long. If a force of 50 lbs. is applied to the end
of the handle what weight can be lifted, neglecting friction?

22
(Take -z = — •)

47. Measurement of Machine Power. — It is often very
desirable to determine the power
necessary to operate a machine.
This may be done by means of
instruments called dynamometers.
The prony brake is one of the most
simple and familiar examples of the
dvnamometer.

(Copyrighted by Millers
Palls Co.)

Fig. 32. — Principle of
Prony Brake.

Figure 32 represents one type of prony
brake in which a fixed band of leather,
or rope, is in contact with a portion of
the circumference of a pulley or drum
A. The band has one end attached as shown at B, while the weight
C is hung at the other end.

The formula to find the foot-pounds per minute is:

3.1416 X diam. of pulley X rev. per min. X weight

As an example, if the pulley of a band brake is 126.04 in. in diameter
and makes 200 revolutions per minute, while a weight of 5 lbs.
hung at end of the band just affects the speed, what is the H. P.?

3.1416 X 126.04 X 200 X 5
12

= 32,997.272 or approximately 33,000
ft.-lbs. per minute = 1 H. P.

48. Another Form of Prony Brake. — Figure 33 shows the
prony brake as generally constructed. The clamp shoes c and d

APPLIED SCIENCE

are clamped to the pulley with bolts a, a. As the pulley revolves
in the direction indicated by the arrow, the tendency is for the
entire brake to rotate in the same direction; this is prevented by

(Copyrighted by Millers Falls Co.)

Fig. 33. — Prony Brake as Usually Constructed.

the weights P in the scale pan suspended from the end of lever A.
When the pulley runs at its normal speed, sufficient weight is
placed in the pan at P to balance the lever between the pins e, e,
which are provided to prevent the lever from revolving. The
power absorbed by the clamp shoes c and d is equal to the amount
of work which is accomplished in foot-pounds per minute by the
revolving shaft.

This work in foot-pounds = NxPxLx2t:

where N is number of revolutions per minute, and L the length of
lever.

The H. P. =

2r,NPL
33000

The small pulleys /, /, and the weight W are provided as a counter-
balance for the lever arm when the machine is at rest. The clamp
shoes c and d should be well lubricated. To illustrate the calcula-
tion, assume that an engine shaft makes 240 revolutions per minute,
what is the H. P. developed when a weight of 50 lbs. is just balanced
at the end of a 10-ft. lever, as shown in Fig. 33?

2 x NPL 6.2832 X L40 X 50 X 10
H. P. = 22.8 H. P.

33000 33000

PULLEYS. INCLINED PLANES, AND WEDGES 49

49. The Cost of Mechanical Advantage. — It has been
shown that by the use of tools and machines which are all
based on one of the six principles just described, it is possible
to apply a small force to overcome a large resistance. This
advantage is obtained by sacrificing either speed to gain
force or force to gain speed. The ratio of the resisting force
to the applied force is called the mechanical advantage of the
tool or machine. The advantage gained in all the simple
machines is lost in time. No machine will enable a given
amount of force to raise 2 lbs. with the same velocity as
it can raise 1 lb. As a matter of fact, power is wasted by the
use of machinery because the in-
crease of friction adds to the amount
of force which has to be used.

60. The Effect of Friction. — Thus
far we have considered the relations
of speed, force, and resistance from a
somewhat theoretical standpoint; in
actual practice a deduction has to be
made from the advantage apparently
gained because of the resistance of
the machine to free motion. This

resistance is due to the rough surfaces -p ia _ 34 Metal Under a

of the bearings of the machine, al- MagnifyiDg Glass. Iro-

, , , , , aginative view of a

though to the naked eye these bear- shaft showing micro-

ings may appear perfectly smooth. EfirriSS"' ^
When polished surfaces are inspected

or examined under the microscope (Fig. 34) they are
seen to have many inequalities and to be comparatively
rough. These inequalities fit into the hollows of the oppo-
site surface, out of which it requires some force to lift or

50 APPLIED SCIENCE

slide them. This is done first by polishing the surfaces
until they are as smooth as possible and then by inserting
some lubricant, such as oil, grease, or black lead which fills
up the little holes and thus reduces friction. Friction is
also reduced by having two different substances or metals
in contact, as, for example, the brass or sometimes jeweled
boxes in which the steel axles of wheels in clocks and watches
revolve. The greatest amount of friction arises just before
motion takes place, because the inequalities of the upper
surface sink into those in the lower more completely at rest
than in motion.

In going down a hill, drivers of heavy vehicles pass a

chain through a spoke of the wheel to increase the friction,

and thus prevent the wheel from turning. Friction between

the ground and the shoe enables us to walk. Shoes with

hob nails are dangerous on a smooth

iron plate because the two iron surfaces

give little friction.

SL Use of Ball Bearings. — Rolling
friction is friction due to a solid rolling
over a smooth surface, as in the case
of a car wheel moving over a rail, while
a sliding friction is due to the sliding of
the same particles of a wheel over a
rail. Sliding friction is greater than
rolling friction, and in the case of iron
it is 100 times greater. Hence the use
of ball bearings (Fig. 35).

52. Measurement of Friction.— In all machines there is
more or less friction. The work done by the acting force

PULLEYS, INCLINED PLANES, AND WEDGES 51

always exceeds the useful work by the amount that is trans-
formed into heat. The ratio of the useful work to the total
work done by the acting force is called the efficiency of the
machine.

Useful work accomplished

Efficiency =

Total work expended

The efficiency of simple levers is very nearly 100% because
the friction is so small as to be disregarded. In the inclined
plane the friction is greater than in the lever because the
two bodies come in contact with a larger surface. The
efficiency of a lever is somewhere between 90 and 100%.
The efficiency of the commercial block and tackle with several
movable pulleys varies from 40 to 60%. In the case of the
jack screw there is necessarily a large amount of friction
so that its efficiency is often as low as 25%. Gear wheels
or chain gears, such as are used in bicycles, are machines of
high efficiency, often running as high as 90% or more.

Questions

1. A crane consists of what simple machines?

2. Name a number of "twisting tools and appliances" such as
are used in placing a nut in position. Notice the manner in which
they are used. Are two distinct circumferences made in their
operation? Name the mechanical principles involved.

3. Name a number of "screw tools and appliances," that is,
tools and appliances that are based on a spiral groove. Divide
them into two parts: those that communicate motion and those
that are used as fastening agents.

4. Explain the manner in which a screw communicates motion.

5. Name a number of "hoisting tools and devices." How do
they work? What is the mechanical principle involved?

6. Name a number of "cutting tools." What is the shape of
the cutting edge? Does the part that "cuts" come to a point

52 APPLIED SCIENCE

or sharp edge? Does the part away from the cutting edge become
thinner or thicker?

7. Name a number of "run appliances," that is, appliances
or tools connecting two floors or stagings at different levels.

8. Is the "run" appliance always longer than the perpendicu-
lar distance between the two levels?

9. Divide all the ordinary tools and appliances that you remem-
ber into the following groups: hitting tools; twisting tools; screw
tools; hoisting tools; cutting tools; "run" appliances.

10. Name a list of simple tools and appliances and state whether
"speed" or "power" is gained by the use.

11. Name some machines that involve more than one of the
simple machines or mechanical principles.

12. What is the meaning of the expression "mechanical effi-
ciency "? " Mechanical advantage "?

13. What is friction?

14. Where is friction found?

15. Is friction a form of energy?

16. Is friction a "necessary evil" or has it some advantage?

17. Do we use friction in walking?

18. Is friction used in the case of automobiles?

19. How is friction reduced?

20. What are roller bearings? Are they useful in reducing
friction?

21. Why is sand placed on the railway track?

22. Why are roller bearings placed on skates?

23. Explain why it is difficult to walk on ice.

24. What is the object of waxing a floor before dancing?

26. Give the approximate percentage of efficiency of the different
simple machines.

26. What is a lubricant?

27. What are some of the dangers of excessive friction among
woody materials, paper, or cotton stock?

Problems

1. A plank 11 ft. long is used to raise a barrel of flour (196 lbs.)
into a car 3^ ft. high. What force is necessary to raise it?

PULLEYS, INCLINED PLANES, AND WEDGES 53

2. A carpenter uses a force of 10 lbs. in pulling a saw across a
piece of wood and 100 strokes of 2 ft. each to saw the wood in two.
What amount of work was done?

3. A differential pulley has a large wheel 10 in. in diameter and
a small one 8 in. What is the mechanical advantage?

4. A person desires to roll a barrel weighing 200 lbs. into a
wagon that is 4 ft. above the ground. What is the most effective
way to do it if he can push with a force of 80 lbs.? How long a
plank will be necessary?

CHAPTER VI
LAWS OF MOTION

53. Three Laws of Motion. — Some interesting facts
about the motion of bodies, which we ordinarily find out
only as the result of long experience, can readily be under-
stood by a knowledge of the laws of motion and momentum.
A body set in motion by a force, such as steam or electricity,
starts slowly and its speed increases in proportion to the
strength of the force and the resistance of the body. To
illustrate: When an electric car moves we experience a
heavy jarring; this is due to the seat starting before our
body and pulling us along.

The natural state of inorganic or lifeless bodies is one of
rest, called inertia. Every body continues in a state of rest, or
when set in motion continues to move in a straight line, unless
acted upon by some external force. This is the first law of
motion.

When an object is moving, its speed may be increased by
applying more force. If the force is applied in a different
direction from that in which the body is moving, the body
will either stop or change its direction of motion. This prin-
ciple may be expressed by stating that every change of motion
is in the direction of the new force applied to the body, and is
proportionate to it This is the second law of motion.

A force never appears singly. That is, there are always
two or more contending forces in every mechanical operation
and in all mechanical work. To illustrate : When a mechanic

LAWS OF MOTION 55

attempts to unscrew a nut, the pull or force he applies to
the nut is called action, and the resistance is called reaction.
The reaction consists of friction and of the tendency of the
nut to remain stationary. The relation between action and
reaction is such that every action is resisted by an opposite
and equal reaction. This is the third law of motion.

54. Momentum of Bodies. — The momentum of a body is
the quantity of motion in the body, and is the product of the
mass and the speed.

As an example: To find the momentum of a body 9 lbs. in weight,
moving with a velocity of 75 ft. per second, the rule is:

Mass X Velocity = Unit of momentum
9 X 75 = 675 units of momentum

We may abbreviate this rule by substituting letters for quantities.
Let the mass be represented by M and velocity by V. Then

Momentum = M X V

The multiplication sign is usually left out between letters; there-
fore the quantity is written MV. Momentum may be expressed as
a product of pounds by feet per second and tons by feet per second.
In the metric standard it may be expressed as a product of grams
by centimeters per second, or kilograms by centimeters per second.

55. Gravitation and Center of Gravity. — If we take a
thin bar of iron and place it on a table, it will remain there.
Remove the support, and the bar will fall to the ground.
All bodies act in the same way. The earth attracts them,
and this force is called gravitation. If a bar of iron is laid
across a support, one particular point will be found at which
it will balance, and remain at rest; that point is called the
center of gravity of the iron bar, because it is the point at which
the entire weight of the body may be considered as centered;

56 APPLIED SCIENCE

if the bar is of the same thickness throughout its length, it will
be exactly in the center. If the support is changed to any
other point, the bar will fall to the ground; or if a weight of 1
lb. be fixed on one end, and a weight of 4 lbs. on the other end,
then the center of gravity will be 1 ft. from the 4-lb. weight.
The center of gravity is also called the center of inertia or the
center of mass. It is the point in a body about which the mass
is evenly disposed and if pivoted at that pointy the body ought to
be balanced.

56. The Line of Direction. — A perpendicular line drawn
from the center of gravity to the earth is called the line of direc-
tion. This imaginary line is of great importance in the con-
struction of buildings, chimneys, and other tall struc-
tures. By the use of the law of gravity and the ' * plumb
line/' the mason, bricklayer, or machinist can test a
wall or other kind of structure as it is being built to
see that it is perpendicular and perfectly straight.

57. Mercury Plumb Bobs. — Mercury plumb bobs
(Fig. 36) are usually made of hollow steel rods filled
with mercury or quicksilver. Consequently they are
unusually heavy in proportion to their size, and their
centers of gravity are low. Their comparatively small
diameters also allow them to be used close to corners
Fig 36 anc * wa ^ s J they are not easily affected by draughts of
Mercury a ir ; and they can be packed in a small space. As a re-
Bob, suit, they may be used to advantage almost anywhere.

68. Acceleration Due to Gravity. — If a body falls freely
in vacuum, that is, without resistance from the air, its ve-
locity will not be constant throughout the entire f all, but will

LAWS OF MOTION 57

increase at a uniform rate. This uniform increase in speed
is called the acceleration of gravity. It is expressed in feet
per second per second.

When a body falls freely in this manner it will have attained
at the end of one second a velocity of 32.2 ft. per second.
Thus the average velocity during the first second will be
16.1 ft. per second. Since the velocity increases at a uni-
form rate, it will be 64.4 ft. per second at the end of 2 seconds,
and the space fallen through during this second second will
be 48.3 ft.

The average velocity of the object for any second is the average
of the velocity at the beginning and the velocity at the end of
that second.

Thus:
Velocity at beginning of 1st sec. = 00.0 ft. per sec.
Velocity at end of 1st sec. = 32.2

a a a

2)32.2
Average velocity for 1st sec. = 16.1 "

<< a

Velocity at beginning of 2nd sec. = 32.2
Velocity at end of 2nd sec. = 64.4

2)96.6

Average velocity for 2nd sec. = 48.3

Velocity at beginning of 3rd sec. = 64.4
Velocity at end of 3rd sec. - 96.6

2)161.0

<( << <<

11 u a

it << ({

u a it
u a i(

Average velocity for 3rd eec. - 80.5

As the space fallen through in any given second is equal
to the average velocity for that second, it follows that the

58 APPLIED SCIENCE

total distance fallen through at the end of any given second is
equal to the average velocity up to the given point multiplied
by the number of seconds during which the object has fallen.

For example:
Initial velocity = 00.0 ft. per sec.

Velocity at end of 3rd. sec. = 96.6 " " "

2) 96.6

Average velocity for first 3 sec. = 48.3 " " "

3 X 48.3 = 144.9 ft., space fallen through in first 3 sec.

The above theory supposes a body to be falling freely in
a vacuum, but while the air will offer a resistance and some-
what reduce the actual motion the principle is the same.
Acceleration due to gravity varies but little at different
latitudes of the earth. Acceleration due to gravity decreases
at higher altitudes, and increases as we go below the surface
of the earth. All these variations on the earth's surface are
so small that they hardly need to be considered in any cal-
culation concerning practical problems in mechanics. Ac-
celeration due to gravity may be considered as 32.2 ft. per
second each second.

Since the velocity of falling bodies increases at the uniform
rate of 32.2 ft. per second, the final velocity in feet per
second must equal the product of the time in seconds multi-
plied by 32.2.

To illustrate the calculation: What final velocity will a body
acquire in a free fall during 7 seconds?

V = 7 X 32.2 = 225.4 ft. per second

59. Kinds of Motion. — Motion may be uniform or variable.
When equal distances are traversed or covered in the same

LAWS OF MOTION 59

length of time the speed is constant. On the other hand,
when the speed changes and equal distances are not traversed
or covered in the same length of time, the motion is said to
be variable. The rate of change of velocity is called the
acceleration. It is said to be positive when it increases,
and negative when it decreases.

A body moving from one place to another in a straight
line is said to undergo translation or rectilinear motion. When
a body moves around a fixed point or axis it is said to rotate.
The particles of the body make concentric circles, as a pulley
rotates on a shaft; such motion is said to be curvilinear.

60. Cams. — In a great many machines, such as looms, sew-
ing machines, printing presses, punch presses, automobile
engines, etc., it is often necessary to give to each machine a
motion peculiar to itself. In one machine it may be necessary
to change circular or rotary motion into back-and-forth or
reciprocating motion at definite times during the working
of the machine. In another machine the opposite effect
may be desired. A curved plate or groove, called a cam,
is used for producing such irregular motion. Cams are
constructed in various shapes and dimensions. They may
consist of simply a wheel, a projecting part of a wheei,
or a revolving piece. The nature of the motion given
by the cam to a machine is determined by the shape of
the cam.

61. Centrifugal Force. — Rotating bodies like grindstones,
fly-wheels, etc., are built to run at a certain maximum speed.
If this speed is exceeded the body may fly to pieces, as there
is a tendency for particles of a rotating body to fly off in
straight lines. The force that causes this movement away

60 APPLIED SCIENCE

from the center of gravity is, as we have noted, called
centrifugal force. This force is overcome by the cohesive
force of the material that composes the fly-wheel, or the
adhesive material that holds the particles of the grindstone
together. This cohesive or resisting force is called centri'petal
force and is directed toward the center.

The principle of centrifugal force is utilized to great ad-
vantage in the construction of hydroextractors, i.e., machines
designed to throw
off the water con-
tained in dyed or
scoured fabrics, in
sugar in a liquid
state, and in bolts
and nuts or other
small metal parts.
All centrifugal ma-
chines operate on
essentially the same
principle. Figures
37 and 38 show a
, machine designed
to extract the liquid
from solid or semi-
solid matter by cen-
trifugal force; this
ing has- type of machine is
og. . . .

known as a chip

wringer. Figure 37 shows the basket about to be lowered
into its casing; the machine is then ready for use. Figure
38 shows the machine open with the basket inverted, the
material having been dumped out.

LAWS OF MOTION 61

The operation of the chip wringer is comparatively simple.
Suppose the liquid is to be extracted from a pile of bolts
and nuts. The bolts and nuts are placed in the basket, sus-
pended above its casing by means of a device. The basket is
then lowered into its
casing. When in
this position, ready
to be set in motion,
there is a very nar-
row slit between the
rim of the basket
and the casing. This
slit is so narrow that,
although liquid can
readily flow through
it, the passage of
any solid particles
is prevented.

The basket is then
set in motion and
made to revolve at
a high speed. The
centrifugal force
thus generated

forces the bolts and nuts to the sides of the basket and throws
off the liquid. (The amount of centrifugal force generated
increases with the revolutions per minute [R. P. M.] of the
basket.) All the water thrown off is ejected from the basket
through the narrow slit just described. When all the water
has been removed in this way, the machine is stopped. The
basket is then raised, carried along to a convenient place,
and dumped.

62 APPLIED SCIENCE

62. Force Expressed Graphically. — Sometimes it is neces-
sary to express or measure a force or forces graphically,
that is, by means of lines. This is particularly true in the
building of machinery and structures, where the results of
the application of force and skill may be obtained with less
labor than by calculation. Graphic expression also gives ac-
curacy sufficiently near for good practice. Force is mea-
sured in this way by considering the beginning of a line to
be the point at which the force is applied, the length of the
line to be its magnitude, and the direction of the line to
be the direction of the force.

To illustrate: If a force of 10 lbs. is applied at a certain point A
in an easterly direction, it would be represented by the line AB
drawn 10 units in length. If there are two forces acting on a body
at A and at right angles, one with an easterly direction of 10 lbs.
and another with a northerly direction of 5 lbs., the actual direction

of the motion of the body may be repre-
sented by the following parallelogram, the
lines of which are parallel to each other
(Fig. 39). If AC represents a force of 5
lbs. (called a component force) and AB

Z, OA n „ , represents a component force of 10 lbs.,

Fig. 39.— Parallelogram *1 * '

of Forces. AD will represent the resultant of the

two forces. To maintain the forces AB
and AC in equilibrium a force must be applied at A equal to
AD and acting in the opposite direction AF.

AF = AD
AF is called the equilibrant.

The above principle may be worked backwards. For
example: If one force is given, it is always possible to find
two others in given directions which will balance it.

LAWS OF MOTION 63

63. Different Kinds of Energy. — There are, as noted in
Chapter III, many forms of energy, such as chemical, elec-
trical, muscular, mechanical, etc. Any one form may be
transformed into any other form. For instance, electrical
energy may be transformed into chemical energy by charging
a storage battery; muscular energy into mechanical energy
by sawing a board with a hand-saw ; mechanical energy into
electrical energy by means of a dynamo. It is impossible
to create or destroy energy, but it is easy to transform it.
A pile-driver head weighing 75 lbs. suspended 25 ft. above
the ground possesses energy, to the extent of 1875 ft.-lbs.
due to its position. This energy is known as static or poten-
tial because it is stationary. When the weight is released
and falls, the energy is called kinetic energy, that is, energy
released or due to motion. Potential energy is sometimes
called, energy of stress; for example, the spring in a spring
balance is under tension when a weight is suspended from
the hook. Of course in all cases the weight times height
equals the energy of the body,

E (potential) = W X H,

although sometimes the velocity is given instead of the
height. Then the:

wxv 2

E (kinetic) = — —

2 Force of gravity

or WV 2

K =

2(7

This is obtained by substituting in the formula for energy,
for the height its value

(Velocity) 2

2 Force of gravity

64 APPLIED SCIENCE

2</

Impulse equals force times time. Impulse may be defined
as the force multiplied by the length of time it acts.

Weight X Velocity

Momentum =

The energy stored in a revolving fly-wheel is kinetic, and
is, therefore, represented by the formula

WV 2
K =

W stands for, or is equal to, the weight of the wheel in pounds,
g for 32, attraction force of gravity, V for velocity of a de-
finite point in the iron in feet per second. At this
definite point the whole weight is assumed to be
collected.

64. Springs as a Source of Energy. — Springs are
useful as machine parts, because of their capacity
for yielding to force without permanently losing their
shape — technically called their "permanent set."
Wound springs possess potential energy, because at
some previous time work has been performed upon

Fig" 40 them * n *he winding. Coiled springs in watches and

Coiled clocks which set the mechanism in motion, are an
illustration. Steel is superior to all other materials

for the manufacture of springs, but must be protected when

exposed to dampness; otherwise it will rust.

IAW8 OF MOTION 65

The force of a spring is not exactly uniform in its action,
for it has its greatest energy when most bent or most tightly
wound. Since the elastic force of a spring is not
affected by the force of gravitation, it is used to
ascertain the amount of the earth's attraction
(pul! or weight) in various places. This is done
by the use of a cylindrical spring balance to which
a hook or ring is fastened (Fig. 41). The object
to be weighed is hung from the hook which pulls
the spring in proportion to the weight. From
graduations on the scale it is possible to read
directly the weight of the commodity.

66. Weights as a Source of Power. — Weights
are used as a source of energy when uniform
pressure or action is desired. The proper tension
is maintained on a rope by means of a weight „ .,
suspended on a movable pulley. There are Spring
many applications of weights as a motive force,
but when they are used, the action is comparatively, slow.

They are sometimes employed as the motive force for large clocks,
such as those installed in towers.

A clock or watch contains three important pieces of mechanism
or elements: (1) the source of energy to move the parts, which is
a suspended weight in large clocks or a spring in small clocks and
in watches; (2) the series of wheels, called a train of wheels, or
gears, operated by the driving force; and (3) a device for control-
ling the movement of the train of gears.

66. Accumulated Energy. — We know that energy tends
to accumulate in our muscles while at rest and that it can
then be expended either gradually or by one effort, but to no
greater extent than the reserve force that has been accumu-

66 APPLIED SCIENCE

lated. The same accumulation of energy takes place in run-
ning before taking a jump. This accumulated energy or
method of gathering momentum is utilized in machines by
placing a fly-wheel on the driving shaft. When such a wheel
revolves, the momentum will cause it to run a long time after
the power has been shut off, due to the energy stored in the
fly-wheeL

Questions

1. Explain why the wind is able to do the work of turning a
windmill.

2. When the wood-chopper chops wood he usually swings the
axe high when he comes to a knotty piece. Why?

3. Why is it more comfortable to ride in a carriage with pneu-
matic tires and springs than in a farm wagon with neither?

4. Explain why fortifications are usually made of earthwork
and not masonry.

5. When an automobile runs too fast around a corner it "skids."
Why?

6. Explain why a person riding in a rapidly moving railway
car is thrown forward when the car stops suddenly.

7. Explain why a person standing in a street car is thrown
back when the car starts suddenly.

8. (a) In attempting to kick the panel out of a door why does
one experience a pain from the kick? (b) This pain is not severe
when you kick a canvas curtain. Why?

9. Why does a man lean forward when he climbs a hill?

10. (a) What is the ballast of a ship? (b) What is the object
of the ballast?

11. Why is it unsafe to stand in a canoe?

12. Which is more steady (stable) a load of wood or a load of
metal equal in volume?

13. Explain the principle of a revolving clothes-dryer used in
laundries.

14. The outer rail of a railroad curve is higher than the inner
one. Why?

LAWS OF MOTION 67

16. Give the kind of energy present in the following examples:
pile-driver hammer 40 in. in the air; gunpowder; moving ship;
water running over a dam; water in a lake on a mountain; water
in a reservoir; charged storage battery; coal; wood; recoil of a
gun; escaping steam.

16. Why is oil thrown off from gears and pulleys? Why is
mud thrown off automobile wheels?

17. Why does a lathe continue to move after the switch is
turned off?

Problems

1. How much energy does a mass weighing 3 tons acquire in
falling through 100 ft.?

2. A machinist exerts upon a file a force of 11 lbs. downward
and 15 lbs. forward. How much work does he do in 41 horizontal
strokes each 6 in. long? In what units is the result expressed?

3. A pile-driver weighing 510 lbs. drops from a height of 15 ft.
pushing the pile down 6 in. What was the potential energy of the
weight before it started to fall? What is the resisting force of the
pile?

4. If a drop hammer weighs 600 lbs. and falls from a height of
24 in., what kind of energy will it possess before falling, and how
much energy will be expended?

5. A large weight of 700 lbs. is allowed to fall a distance of 18
ft. in order to break old car-wheels. What is the kind and the
amount of energy?

6. An elevator in a public building weighs 3J^ tons. How
much energy will be necessary to lift it from the first floor to the
second, a distance of 20 ft.?

7. A pile-driver weighs 265 lbs. and falls from a height of 16 ft.
What is the energy at the time it strikes the pile?

CHAPTER VII
MECHANICS OF LIQUIDS

67. The Utilization of Liquids in Industry. — Liquids,
particularly water, possess certain properties which render
them invaluable for many industrial purposes. These
properties form the bases upon which hydraulic machines
and many other devices are constructed. To know how to
use all these contrivances efficiently and intelligently, it is
necessary to know the principles underlying them.

68. General Properties of Liquids. — Water and all other
liquids resemble solids in that they possess a definite size;
that is, they occupy a definite space. Liquids differ in that
they have no definite shape. The shape of a liquid is the
shape of the vessel which holds it. A solid has a definite
shape and retains it until acted upon by a force greater
than the cohesive strength of its particles. The force of
gravity is continually forcing liquids to seek the lowest leveL
This fact is illustrated when two vessels containing the same
liquid are connected. The level in each becomes the same,
regardless of the form or distance of the connecting pipe.
This peculiarity of liquids is commonly expressed by the
saying "water seeks its own level."

A force of any kind, however small, will change the shape
of a liquid. To illustrate: If a pebble is dropped into a pond
it moves the whole of the water and the motion can be seen
by the ripples which form on the surface of the pond. The

MECHANICS OF LIQUIDS 69

rate of this change in shape varies with different liquids.
Those in which the change proceeds slowly are called viscous
liquids, while liquids in which the change takes place quickly
are called mobile.

Another important property of liquids is that they cannot
be compressed. If force acts on any part of a liquid, it
will transmit the pressure of the force equally in all direc-
tions. This principle, which is called Pascal's law from its
discoverer, renders liquids very valuable as a medium for
pressure transmission in all forms of hydraulic machines.

69. Water Pressure. — Water exerts a pressure on the

bottom and sides of the vessel which holds it. Fill a vessel

1 cu. ft. in volume with water. If the water is weighed it

is found to weigh about 62.5 lbs. Therefore 62.5 lbs. is

pressing on the bottom of the box, the area of which is 144

62.5
sq. in. Therefore the pressure per square inch is — - or

.434 lb. The unit of pressure is the amount of pressure
to the square inch. Pressure equals force per unit area.

A liquid also exerts pressure on the outside of any object
immersed or pushed into it and the pressure increases with
the depth. This phenomenon may be explained by consider-
ing a liquid as made up of a large number of thin horizontal
layers, each layer supporting the weight of those above.
The lower the layer, the greater the weight of liquid it has to
support; hence the greater the pressure exerted upon it.
This pressure has nothing to do with the size and shape of
the vessel and is evenly exerted upon each square inch of
surface.

The total pressure of a liquid upon any portion of the
vertical sides of a vessel is equal to the weight of a column

APPLIED SCIENCE

20*

S:j=t

of the liquid, whose base and length are respectively the area

of that portion of the side and its average depth. This may
be explained in another way. The pressure against the
vertical side of a tank at the surface of the water is zero,
for the liquid has no depth. But the pressure on the side
increases with the depth until we reach the bottom of the
tank, when it is equal to the pressure against the bottom.

The average pressure on the side then
is the pressure exerted on the middle
of the side, and is equal to one-half
the pressure per unit of surface
against the bottom.

The following laws apply to
liquids:

I. The pressure does not depend
upon the size or shape of the vessel.
The pressure increases with the verti-
cal depth below the free surface.

II. At any point in a liquid, the
upward, downward, and lateral or
sideways pressures are equal.

III. To find the lateral pressure of
Fkj. 42.— Tank of Water, water, upon the sides of a tank, multi-
ply the area of the submerged portion

of the side in inches, by the pressure of one-half the depth.

As an example: What is the lateral pressure on one side of a
tank 20 in. wide and 2 ft. deep (Fig. 42)? The solution is as follows:
20 in. X 24 in. = 480 sq. in., area of side.
2 ft. X .434 = .868 lb., pressure at bottom of tank.
.868 -*- 2 = .434 lb., average pressure due to one-half the

depth of tank.
.434 X 480 = 208.32 lbs., pressure on one side of the tank.

^^^^^^^

I
I

2ft.
i
I
l
i
i

I
I
i

(Copyrighted by Millers Palls
t. o.)

MECHANICS OF LIQUIDS 71

70. Hydraulic Press Machinery. — It has already been
shown that when pressure is applied to any part of a confined
liquid, the pressure is transmitted equally in all directions.
This law of Pascal is utilized to increase or multiply pressures.
For example: If two pistons of unequal area are pressing
upon the same liquid, held in connected tubes or cylinders,
and weights are placed upon the pistons to keep them from
moving up or down, it will be found that the weights must
be proportional to the surfaces of the water if one piston is
not to force out the other. This principle is applied in the
construction of the hydraulic press. The hydraulic press is
a machine used in mills and in boiler- and machine-shops for
punching holes through plates, for exerting enormous pres-
sure on paper, cotton, and cloth, for testing iron and wooden
beams, and so on. It operates by creating a pressure over
a small distance, by means of a lever and water.

The hydraulic press consists of two pistons of unequal area
working in connected cylinders which are filled with water. When
the small piston is raised, water rushes into the cylinders through
a valve opening upwards. As soon as this piston is lowered,
the valve closes. The small piston thus acts as a pump when water
is forced from the small to the large cylinder, causing the large piston
4 to rise slowly.

Usually the small piston is 1 in. in diameter, giving an area of
.7854 sq. in. The large piston, called the ram, may be any size, de-
pending upon the pressure required. The size of the cylinder is usu-
ally from 10 to 14 in. in diameter. The pressure per square inch is
the same in both cylinders. As the flow of water is slow, and the
distance is short, little or no pressure is lost in transmission. As the
areas of the pistons are unequal, the total pressure must differ ac-
cordingly. To illustrate; If the diameter of the large piston is 10 in.
#nd the diameter of the small piston 1 in., then the area of the large'
piston is 100 times that of the smaller, or 78.4 sq. in. (The areas
of two circles are to each other as the squares of the diameters.)

APPLIED SCIENCE

Therefore, a pound pressure on the piston of the small cylinder
gives a total pressure of 100 lbs. on the large cylinder. While the

machine develops a cer-
tain amount of friction
at the stuffing box,
pins, etc., of the pump
or smaller cylinder, the
loss is probably only
5%. Therefore, as a
general rule, 95% of the
pressure applied to the
smaller cylinder is given
to or transmitted to the
water in the pump.
Figure 43 illustrates a
hydraulic press designed
to show a pressure up to
300 lbs. to the square

inch. The handle of
Fig. 43.— Hydraulic Press. the pump which com .

presses the water in the small cylinder is seen on the left.

r ^//^//////////////////A^

w _

71. Uses of Hydraulic Machinery. — For the majority of
operations requiring very great force applied through a
comparatively short stroke, as in riveting, punching, shear-
ing, lifting, forging, flanging, and many other similar opera-
tions, there is no other machinery so efficient as hydraulic;
first, because there is absolutely no motion or power con-
sumed except in the act, and at the moment of performing
the desired operation — at all other times everything is at
rest; secondly, because the water is carried or transmitted
in a small pipe from its reservoir or tank to the machine.
Under proper conditions, this transmission can be accom-
plished with an efficiency far surpassing that of the line-shaft,
electric wire, or air tube. All the energy which a steam pump

MECHANICS OF LIQUIDS 73

can deliver in the course of 10 to 15 minutes is utilized in
the hydraulic machine within a few seconds. This is not
possible in the use of any other form of machine tool.

72. Capacity of Pipes. — In computing the capacity of
pipes used to convey liquids one should remember that the
capacity varies with the area, and that the areas of similar
figures vary as the squares of their corresponding dimensions.
Pipes being cylindrical in shape are, therefore, similar figures.
The areas of any two pipes are to each other as the squares
of their diameters.

Thus, if one pipe is 6 in. in diameter, and another is 3 in. in di-
ameter, their ratio is — , or 4 to 1, and the area of the larger one is,
therefore, 4 times that of the smaller one.

73. Water. — A manufacturer usually stores quantities of
water for manufacturing purposes in a tank at the top of
each of the different buildings of the plant, but in case the
factory or mill is near a stream, the water is stored in a dam,
at a convenient height. The pressure of the water against
the sides of the tank or dam is exerted perpendicularly to
the surface on which it bears. Every pound of water in a
tank or dam at some height above the point where the
water is to be used possesses a certain amount of potential
energy due to its position. To illustrate: W lbs. of water
raised a definite height H possess the capacity of doing work
which is equal to the weight of water in pounds multiplied
by the height in feet. The result is W X H ft.-lbs.

To estimate the energy in the reservoir of a city or town
so as to know the exact water pressure, it is necessary to
know the perpendicular height from the water level in the

74 APPLIED SCIENCE

reservoir to the point of discharge. The perpendicular height
is called the "head." Mechanics, engineers, etc., often
speak of a "head of water," meaning the pressure that
water exerts. "A head of 50 ft.," for instance, is the pres-
sure (due to its weight) of a column of water 50 ft. high.

The pressure per square inch at any point in a body of water
equals the depth in feet below the surface, or the head times .434.
If P is pressure per square inch and H is head,

To find the head when pressure is given the rule is: Divide the
pressure by .434.

74. Dams and Water Wheels. — Look at a mill or factory-
erected on the side of a stream. The water will usually be
found confined by a wall of earth
or stone. The water runs from
the stream through an opening
called a canal and then to the
water wheel. The difference in
height between the canal and the
river represents the fall or pres-
sure of water which moves the
machinery in the mill. In case
of floods the water can run freely
over the dam, without affecting
the mill.

Falling water is a source of energy that supplies power
to operate mills, factories, electric power plants, etc. Many

MECHANICS OF LIQUIDS 75

factories and mills are located on the borders of rivers in the

valleys of hilly communities. The water

draining the hills rushes with considerable

force down the rivers. The energy of

this water is utilized by allowing it to run

over an overshot water wheel (Fig. 44).

The weight and force of the moving water

are such as to cause the wheel to move,

which in turn moves the machinery by

means of belts or gears.

The most effective method of utilizing

water power is by me%ns of a wheel called

a turbine. The river is dammed, and the

water is conducted through a canal which

runs alongside the mills. The water is al-
lowed to pass through a
cylindrical tube to a pen-
stock which surrounds an
iron case containing the tur- Pio.4S.— UaeofTur-
bineorrotatingwheel (Figs.
45 and 46). By means of a connecting shaft

Fl «- 4 ^r" T . ur " the wheel may be made to operate a dynamo.
Where there is current and little elevation,

the energy of the water may be

utilized by means of an undershot

wheel (Fig. 47). The force of the

current strikes against the lower

part of the wheel.

Where the water is delivered

under considerable pressure its

power may be utilized to run

lathes, sewing machines, and Fin. 47— Undershot Wheel.

APPLIED SCIENCE

other light machinery. A common rotary water motor
is employed, and is attached to the faucet. The water
striking against the cup-shaped fans attached to the axle
of the motor causes it to rotate. The axle is attached to a
shaft which is connected directly or by belts to the machines.
The motor is enclosed in a metal case with an opening
in the bottom to allow the water to escape into the sink or
outlet.

75. The Pelton Wheel.— The Pelton wheel (Fig. 48),
a modified form of undershot wheel, has cup-shaped buck-
ets sticking outward at regular
intervals around its circumfer-
ence. There is a partition in the
center of each bucket. A nozzle
is so arranged that it directs water
on the buckets as they reach the
lowest point of a revolution. The
water strikes the partition of the
cup and turns right and left in-
side of the cup. The change of direction transfers the
energy to the wheel.

Fig. 48.— Pelton Wheel.

76. Wasted Water Power. — Very few people realize the
vast amount of water energy that goes to waste every year.
Every particle of falling or running water represents energy,
the amount of which depends upon the quantity and the
depth of the fall. This energy can be harnessed in the same
way as the energy obtained from the coal we burn. Water
that possesses energy, that is, water that falls, is often
spoken of as "white coal." Power plants that transform
the energy of falling water into electrical energy, oftentimes

MECHANICS OF LIQUIDS 77

are the centers of distributing systems that cover hundreds
of miles of territory, and give electrical service to many
towns.

77. Measurement of Flowing Water.— Oftentimes, as when
water is sold to a corporation or city, it is necessary to know the
quantity of water coming

down a stream. To mea- .. r --. ..(■ .^^=* ,>

sure this a device called a
weir (Fig. 49) is constructed
at the sides of the stream so
as to form either a rec-
tangular or angular opening
through which the water
flows. Where a large quanti-
ty of water is measured the
opening is usually shaped in

this way L_J; "here «— M«™™^ W.te, with .

the quantity is small the

opening is V-shaped, as the How of water may then be measured
with greater accuracy.

The volume of the flow is measured by ascertaining the height
of the water above the bottom of the notch. To do this a peg is
driven into the bed of the stream as at E in Fig. 49. The top of
this peg is exactly the same height as the bottom of the notch.
A measuring scale inserted in the water as shown in the illustration
then enables the exact height of the flow over the weir to be measured.
The formula for determining the volume of flow is:

Where Q = cubic feet passing over the notch per second, K = .59,
which is a constant, B is the breadth of the water in the notch, H
is the height of the water in the notch, g = 32.2 (force of
gravity).
The energy stored in the moving water is equal to the number

APPLIED SCIENCE

of cubic feet passing down the stream per minute multiplied by
the weight of a cubic foot of water, multiplied by the perpendicular
distance this water falls. This equals the number of foot-pounds
per minute. Weight of a cubic foot of water 62.5 lbs.

The E. H. P.* or estimated horse-power, stored in the moving
water is expressed by the following formula:

E. H. P. =

W XU
33000

Where E. H. P. = estimated horse-power, W = weight of water
passing per minute in pounds, H = height it falls in feet.

78. The Law of Buoyancy. — Explanation of why cer-
tain substances float on water depends upon what is called
the law of buoyancy. When a ship is constructed, it is
necessary to lay out the plans in accordance with the prin-
ciple or law involved. Consequently a knowledge of the
law of buoyancy is important.

When a body is immersed in a liquid, it is buoyed up by a
force equal to the weight of the liquid displaced. The weight of
a floating body is equal to the weight of the liquid displaced.
The upward pressure, or buoyancy, of the liquid may be re-
garded as exerted at
the center of gravity
of the displaced
water, B, which is
called the center of
pressure or of buoy-
ancy.

Fig. 51. — Principle
of Stability.

A vertical Fig. 50.— Principle

of Buoyancy,
line drawn through

it is called the axis of buoyancy or of flotation (Fig. 50). In a

floating body at rest, a line joining the center of gravity of the

MECHANICS OF LIQUIDS 79

body, <?, and the center of buoyancy of the water, B f is
vertical, and is called the axis of equilibrium. When an
external force causes the axis of equilibrium to lean, if a
vertical line is drawn upward from the center of buoyancy
to this axis, the point where it cuts the axis is called the meta-
center. If the metacenter is above the center of gravity
the distance between them is called the metacenter height,
and the body is then said to be in stable equilibrium, that is,
tending to return to its original position, when the external
force is removed.

79. Stability of a Ship. — A ship at sea is subject to rolling
and pitching and must be designed to be stable and not
capsize. Rolling is the motion of a ship from side to side.
Pitching is the alternate rising and falling of bow and stern.
In general a ship's motion is a combination of rolling and
pitching. The principle of hydrostatics (water pressure)
governing the stability is as follows: When a ship is floating
at rest its center of gravity and its center of buoyancy are
in the same vertical line. If the force of winds or waves
causes the vessel to keel over as in Fig. 51, the weight of
the ship W acting downward through G, and her buoyancy
acting upward through B constitute a couple which tends to
pull the ship back again upon an even keel with a turning
moment equal to IT X GP. If the couple be strong enough
the ship will swing back towards an even keel. But since
the vessel acquires kinetic energy as it swings, it will not

* A couple is composed of two equal parallel forces acting on the
ends of a bar, for example, in opposite directions ; so far as producing
forward or backward motion is concerned their resultant is zero.
They do, however, tend to cause the bar to rotate.

APPLIED SCIENCE

stop on the even keel, but will roll some distance the other
way, and will continue to oscillate about its mean position
for some time.

80. Specific Gravity. — The specific gravity of a substance
is the number of times it is heavier than the weight of an equal
bulk of water. It may be expressed thus:

Specific gravity (sp. gr.) =

Weight of body or substance
Weight of an equal bulk of water

The specific gravity of a solid is obtained by first weighing
or computing the weight of the object. The weight of an
equal bulk of water is then computed. Finally, the weight
of the object is divided by the weight of the equal bulk of
water.

The following tables show the weights and specific gravi-
ties of the most important metals and liquids.

Weight and Specific Gravity of Metals

Metals

Aluminum

Antimony, cast

Bismuth

Brass, cast ....

Bronze

Copper, cast. . .
Copper, wire. . .
Gold, 24 carat .
Gold, standard.
Gun-metal. . . .

Specific
Gravity

2.67
6.72
9.822
8.4
8.561
8.607
8.9 "
19.361
17.724
8.459

MECHANICS OF LIQUIDS

Weight and Specific Gravity of Metals — (Continued)

Metals

Iron, cast

Iron, wrought. .

Lead, cast

Lead, rolled . . .

Mercury

Platinum

Platinum, sheet

Silver, pure

Silver, standard

Steel

Tin, cast

Zinc

W. per
Cu. Ft., Lbs.

450
485
708
711
849
1344
1436
654
644
490
455
437

W. per
Cu. In., Lbs.

.26

.28

.408

.41

.489

.775

.828

.377

.371

.284

.262

.252

Specific
Gravity

7.21
7.78
11.36
11.41
13 . 596
21 . 531
23.

10.474

10.312

7.85

7.291

Weight and Specific Gravity of Liquids

Liquids

Water, distilled, 60° F.

Water, sea

Water, Dead Sea

Acid, Acetic

Acid, Nitric

Acid, Sulphuric

Acid, Muriatic

Alcohol, pure

Alcohol, proof

Alcohol, of commerce. .

Cider

Honey

Specific
Gravity

1.03
1.24
1.062
1.217
1.841
1.2
.792
.916
.833
1.018
1.45

W. per
Cu. In., Lbs.

036
037
045
038
044
067
043
029
033
030
.036
052

W. per
Gal., Lbs.

8.33
8.55

10.4
8.78

10.16

15.48
9.93
6.7
7.62
6.93
8.4

12.

APPLIED SCIENCE

Weight and Specific Gravity op Liquids — (Continued)

Liquids

Specific
Gravity

W. per
Cu. In., Lbs.

W. per.
Gal., Lbs.

Milk

1.032

.037

8.55

Molasses

1.426 « 05

11.66

Oil, Linseed

.940

034

7.85

Oil, Olive

.915 | .033
.870 .031

7.62

Oil, Turpentine

7.16

Oil, Whale

.923

.848

.878

1.015

.033
.031
.032
.036

7.65

Naphtha

Petroleum ,

Tar

7.39

•8.4

Water. — The weight of fresh water is in practice usually
assumed as 62^ lbs. per cubic foot. But 62J^ would be
nearer the truth at ordinary temperatures, about 70°; or 1
lb. = 27.759 cu. in.

81. Hydrometer. — The common method of determining
the specific gravity of liquids is by means of the hydrometer

(Fig. 52). This instrument consists of a
glass tube with mercury or lead shot in the
bottom to keep it in the water. A scale is
graduated on the narrow stem reading either
directly or indirectly into specific gravity
reading. The scale is graduated by placing
it in liquids of known strength and marking
the level of the liquid on the stem. It is
Fig. 52.— Hy- usual to have two separate instruments, one
rome r. ^ j^j^ ijq U j ( j Sj on w hich the mark is near

the bottom of the stem, and one for heavy liquids, on which
it is near the top.

MECHANICS OF LIQUIDS 83

82. Beaume Hydrometer. — The Beaume hydrometer is
used to determine the strengths of liquids in bleacheries, etc.
The readings are expressed in degrees which may be changed
into specific gravities by this formula:

146.3
Sp. gr. =

146.3 -AT
N is the reading on Beaume scale.

Example. — Change 30° Beaume to specific gravity.

146.3 146.3

Sp. gr. = = 1.258

146.3 - 30 116.3

83. Twaddell Hydrometer. — The Twaddell hydrometer is
used by many manufacturers. The readings may be con-
verted into specific gravity from this formula

100 + .5AT
Sp. gr. =

100
N is tbe Twaddell reading.

Example. — Change 84° into specific gravity reading.

100 + 42 142
Sp. gr. = » — ~ 1.42

100 100

Questions

1. Is water necessary for industry? Explain.

2. What great property do liquids possess that solids do not?
What use is made of water in industry?

3. A liquid is often used as a part ol machinery. What
property is utilized?

84 APPLIED SCIENCE

4. How can the pressure of a liquid on the surface be ascer-
tained?

5. Will the perpendicular sides of a trough filled with liquid
sustain the same pressure, whether the trough be narrow or wide?

6. Explain the principle of science underlying hydraulic
machines.

7. Name some of the applications of hydraulic machines.

8. Why does deep sea diving often cause pain and bleeding
in the ears and nose?

9. Explain the importance of a knowledge of the principle of
specific gravity in the trades.

10. Explain how a modern warship floats although made entirely
of steel, its walls being of steel plate from 6 to 18 in. thick.

11. What is the water-line of a boat?

12. A boat passes from fresh into salt water. Will the water-
line rise or fall?

Problems

1. What is the weight of a rectangular block of hardwood
with the dimensions 8 ft. 4 in. X 7 ft. 6 in. X 3 ft. 3 in.? The
specific gravity of wood is .7. The weight of a cubic foot of water
is 62.5 lbs.

2. What is the weight of a cylindrical block of soft seasoned
wood 8 in. in diameter and 4 ft. long? The specific gravity is .5.
The weight of a cubic foot of water is 62.5 lbs.

3. What is the weight of salt water in a rectangular tank
5 ft. 2 in. X 4 ft. 7 in. X 3 ft. 5 in.? The specific gravity of salt
water is 1.03 and the weight of a cubic foot of water is 62.5 lbs.

4. Express in pounds per square inch a "bend of 69 ft."

5. What is the pressure near the keel of a vessel drawing 18 ft.
of water. (Salt water has specific gravity 1.03.)

'6. A hole is cut in the bottom of a ship drawing 17 ft. of water.
What force is necessary to hold a plank tightly against the hole?

7. It is desired to have a pressure of 60 lbs. at a hydrant.
How high must the reservoir be above the main?

8. A rowboat weighs 230 lbs. How many cubic feet of water
does it displace? A cubic foot of water weighs 62.5 lbs.

MECHANICS OF LIQUIDS . 85

9. The cork of a life preserver weighs 19 lbs. What is the
volume in cubic inches? The specific gravity of cork is 0.25.

10. Elevators are often run by water pressure obtained from the
local water system. If the pressure on the main is 55 lbs. and the
diameter of the plunger of an elevator is 11 in., how heavy a load
can the elevator lift if the friction loss is 30%?

11. Soundings at sea are made by lowering a form of pressure
gauge. If a pressure gauge reads 65 lbs., what is the depth? (Con-
sider the density of sea water 1.026.)

12. What is the weight of a cylindrical piece of lead 4 ft. long
with a diameter of 3 in. ? The specific gravity of lead is 11.4 and
the weight of a cubic foot of water is 62.5 lbs.

13. What is the weight of concentrated sulphuric acid (specific
gravity 1.84) contained in a cylindrical jar 8 in. in diameter and
2% in. high? A cubic foot of water weighs 62.5 lbs.

14. Determine the weight of gasolene in a rectangular tank
3 ft. 7 in. X 2 ft. 2 in. X 1 ft. 8 in., if the specific gravity is .7 and
a cubic foot of water is equal to 62.5 lbs.

15. The inside diameter of a lead pipe is 1 in. and the thickness
of pipe is \i in. How many pounds in a foot of pipe? The specific
gravity of lead is 11.4 and a cubic foot of water weighs 62.5 lbs.

16. What are some of the principles of science underlying the
hydraulic machine?

17. What are some of the uses of hydraulic machines?

18. . (a) What is the weight of a cubic inch of water if a cubic
foot weighs 62.5 lbs.

(b) How may the weight of a cubic inch of a substance be de-
termined, if the specific gravity of the substance is known?

19. In making solder (composed of lead and tin), the tin melts
first and then floats on top. Why?

CHAPTER VIII
PROPERTIES OF GASES

84. Gas Pressure and Industry. — There are many tools
driven by air pressure, and there are a number of devices
that depend upon the properties of gases for their action.
Therefore intelligent knowledge of trade work frequently
depends upon an understanding of some of the fundamental
properties of gases.

86. Three States of Matter. — Ice, water, and steam re-
present the three states of liquid matter. A block of ice has
a definite form and volume. Water has a free, level surface,
but assumes the shape of the containing vessel. Steam has
neither shape nor volume. Notice the steam escaping from
a kettle or from the exhaust pipe of a power plant, and see
how it tends to spread out when released from the containing
vessel. Almost all substances can be transformed into a
solid, liquid, or gaseous state by suitable changes in tem-
perature. We may summarize the characteristic differences
of these three conditions by saying that solids have per-
manent form and volume; that liquids have no permanent
form, but have a definite volume; while gases have neither
permanent form nor permanent volume.

All gases tend to spread out or diffuse themselves and this
tendency causes them to exert considerable pressure equally
against the sides of the vessels holding them. If a piston were

PROPERTIES OF GASES 87

attached to the side of a vessel, the gas would tend to push
the piston out, provided the pressure of the gas on the inside
was greater than that of the atmosphere on the outside.
This is the case when a gas is compressed in a tank. The
gas may be transferred from place to place intact, and then
allowed to pass through pipes, to the place where its energy
is to be utilized.

86. Expansion of Gases. — Gases are said to be perfectly
elastic because they have no elastic limit and expand and con-
tract alike under the action of heat. That is to say, every sub-
stance when in the gaseous state and not near its point of
liquefaction has the same coefficient of expansion, this co-
efficient being j 73 of its volume for each degree Centigrade
or TzoTi of its volume for each degree Fahrenheit.*

Since a gas contracts j 7*3 part of its volume when its
temperature is lowered 1° C, such a rate of contraction would
theoretically reduce its volume to zero at a temperature of
—273° C ( —459.4° F). Since all gases reach their liquefying
point before this low temperature is attained, however, no
such contraction exists. At the same time, it may be said
that if heat is considered as a motion of the molecules of a
substance, that motion is to be considered as having ceased
when the temperature has reached -273° C.

This temperature of -273° C ( -459.4° F), therefore, is
called the absolute zero, and from it all temperatures should
properly be reckoned. Whenever a temperature is men-
tioned as being in degree absolute, either in the Centigrade
or the Fahrenheit scale, it is understood to be counted from

* The relation between the Centigrade and Fahrenheit thermo-
meters is discussed in Chapter IX,

APPLIED SCIENCE

the absolute zero, and therefore is equal to the observed
temperature plus 273 or 459.4 as the case may be.

The lowest temperature which has thus far been attained
is —252° C. Dewar produced it by the evaporation of liquid
hydrogen.

87. Principle of the Barometer. — Gases, though gener-
ally lighter than air, all have a definite weight. This weight

depends upon the volume of the gas and the pres-
sure exerted, as may be proved by means of an
instrument called a barometer (Fig. 53). The
principle on which the barometer is based may
be explained in the following manner.

If you put one end of a tube into a bowl of
water and the other end into your mouth, you can
draw the water up through the tube into your
mouth by sucking. You may think that you
suck the water up, but you do not; you merely
suck the air out of the tube by means of the
Fig 53. niuscles of your mouth. The weight of the outer
Simple Ba- a ir then presses down on the water in the bowl
and forces it up into the tube. As soon as you
let the air into the tube again the water runs back into the
bowl. If you had a tube 40 ft. in length and could suck all
the air out of it, the water would rise up in the tube nearly
34 ft. It would stop at that height, because the weight of
the column would just balance the weight of the air which
presses down on the surface of the bowl. As the tube is
more than 34 ft. long, in the space above the water, there
would be nothing, not even air. Such a space is called a
vacuum, from the Latin word meaning space without air.
If you put the tube into a fluid lighter than water, such a*

PROPERTIES OF GASES 89

alcohol, the alcohol will rise higher in the tube than 34 ft.,
because it will take more fluid to balance the weight of the
air. If the fluid were heavier than water, as is quicksilver
or mercury, it would not rise so high, because it would require
less of it to equal and balance the weight of air.

88. History of the Barometer. — In 1643, more than two
hundred years ago, an Italian, named Torricelli, filled a glass
tube, 33 in. long and open at one end, with mercury. Putting
his finger over the open end so as to keep the mercury from
falling out, he turned it bottom upward into a bowl of mer-
cury, and then removed his finger. As mercury is one of
the heaviest things in the world, it would seem as if it should
have run out of the tube into the bowl; yet it only fell a
little way, and then remained standing in the tube. As
mercury is about fourteen times heavier than water, Tor-
ricelli saw that the height of the mercury in the tube was
about -I* part of the 34-ft. column of water. He at once
concluded that the mercury was held up by the pressure of
air on the surface bowl. He afterward noticed that the
mercury did not always stand at the same height, but that
it rose and fell with the changes in the weather, the air pres-
sure decreasing in damp, wet weather and increasing in dry,
fine weather. This led to the making of the barometer,
which is the same in principle as the tube used by Torricelli.

89. Kinds of Barometers. — The barometer in its simplest
form consists of a long inverted vacuum tube, sealed at the
upper end. The lower end dips into a cup of mercury. A
graduated scale on the side of the tube measures the rise
and fall of the mercury. Such an instrument is often used
to determine the height of mountains and other high places,

90 APPLIED SCIENCE

The air becomes thinner or rarified, the higher one goes and
the pressure becomes less and leas on the mercury in the open
cup, so that the mercury in the long tube is made to fall.
If the distance the mercury will fall for every 100 ft. of alti-
tude is known, the height of a mountain may easily be
ascertained by noticing the height of the mercury column
first at the bottom of the mountain and then at the top.

90. Aneroid Barometer. — The barometer most commonly
made for commercial purposes is the aneroid barometer

(Fig. 54). The word "aneroid"
comes from the Greek and means
"not wet," and was selected
because this type of barometer
operates without any fluids. It
consists of a round, metallic, air-
i tight vacuum case, somewhat like
I a watch, the lid of which, held by
metallic springs inside, rises and
falls with the pressure of the at-
mosphere. By means of levers
and a delicate chain inside, this
rise and fall is made to turn the

pointers on the index. The deflection may then be read

on the circular scale.

91. Properties of Air. — The air or atmosphere which
surrounds the earth is a mixture of two very different gases
called oxygen and nitrogen. To every 21 parts of oxygen
the air contains 79 parts of nitrogen. There are always pres-
ent in the air some dust, moislurc, and other impurities
when atmosphere is put in motion by the unequal distribution

PROPERTIES OF OASES 91

of the heat. When such unequal distribution of heat occurs
the air is called wind. By exposing a large canvas surface
to the wind, boats may be propelled. The farmer utilizes
the wind to turn a large wheel or windmill, and thus pump
his water from a well.

92. Moisture in Air. — Absolutely dry air is a thing un-
known in the natural world. The atmosphere is like a great
sponge. It greedily takes up water and gives it back only
when it has more than it can hold. Very few people realize
that water in the form of vapor is much lighter than air,
and that air containing a large proportion of water vapor
weighs considerably less than the same bulk of perfectly dry
air.

The amount of water vapor in the air varies of course
with the temperature. In every cubic foot of air at 40°
below the Fahrenheit zero, there is
20 of a gram of water. When the
atmosphere contains as much mois-
ture as it will hold it is said to be
saturated, and its humidity is 100%.
If it contains only one-fourth of what
it can absorb the humidity is 25%.
The average humidity of the United
States varies from 80% along the
coasts to less than 40% in Arizona and

New Mexico. A relative humidity of Fl °- Sfi.-Hygrometer.
less than 50% indicates a comparatively dry climate,
while a humidity of only 35% indicates the dryness of
the desert.

The percentage of water in the air is measured by an
instrument called a hygrometer (Fig. 55).

92 APPLIED SCIENCE

93. Manufacturing of Ice. — Ice-making and cold storage de-
pend upon the scientific principle that ammonia evaporates readily
and absorbs a great deal of heat in passing from a liquid to a
gaseous state. Apparatus for the manufacture of artificial ice con-

Fig. 56. — General Arrangement of Refrigerating Plant.

sists of a large cylinder containing liquid ammonia. Attached to
the cylinder is a vat containing brine or salt water with coils
of pipes passing through from the cylinder which holds the liquid
ammonia. The ammonia flows from the cylinder to the coils.-
The vat is filled with galvanized iron boxes, the size of an ordi-
nary cake of ice, and the boxes are filled with distilled water. A
pump exhausts air from the coils, which in turn causes the ammo-
nia to evaporate quickly. As the ammonia passes through the
coils the latter attract the heat from the surrounding bodies to the
extent of freezing the water.

94. How the GaB is Condensed.— The ammonia gas is
taken from the refrigerating section and compressed by a pump.
The ammonia starts from the compressor under, a high pressure
and temperature and passes to a cooling coil, which is the con-

PROPERTIES OF GASES 93

denser. Here, by means of a cold water sprinkler, the gas is
cooled to 45° or 50° F. and is condensed under high pressure to a
liquid state. It then passes to the storage tank.

When ammonia is received ready for use, it is in a liquid state
and enclosed in steel drums, which are only partly filled, leaving
space enough for expansion so as to prevent an explosion. Am-
monia drums have exploded, but always under conditions of over-
heating, for in general, with proper care, there is no danger.

96. Air Pumps. — It is often desirable to force air into
or remove it from a vessel. Air is forced into a vessel by
machines called air pumps, air compressors, condensing
pumps, and blowing engines or blowers. The air pump con-
sists of a tube or pipe with a rim, ground smooth and flat,
extending from the cylinders.

Notice the tire of an automobile as air is pumped into it.
As the air enters, the tube expands, due to the pressure of
the gas, until finally the pressure becomes great enough to
support the weight of the automobile. To remove air from
a vessel, a screw connection is fitted tightly to it. As the
piston is drawn up a partial vacuum is caused by the pres-
sure of the air underneath, so that the air from the vessel
immediately rushes to the cylinder, forcing the valve upward.
This continues until the air pressure is reduced to such an
extent that it is unable to force the valve of the cylinder
open.

96. Boyle's Law. — When the outside temperature is the
same as that of the air within a vessel, the product of the pres-
sure and volume is constant. This is called Boyle's Law. To
illustrate: If the volume of a gas is 2 cu. ft. at a pressure of 1
atmosphere (15 lbs.), then the volume would be decreased
one-half as the pressure is increased twofold. Boyle's Law is

94 APPLIED SCIENCE

sometimes expressed thus: At constant temperature volume of
gas varies inversely as the pressure.

To calculate the volume of a gas at a given pressure, multi-
ply the old volume by the old pressure and then divide by
the new pressure.

I' ': P' = V' : V

P X V = P' x V

Where P and P' are the original and new pressures, and V and
V' the original and new volumes.

The quotient will be the new volume. When a volume of gas
is given it is understood to be at a pressure of 1 atmosphere
unless some other pressure is
expressed. One atmosphere
is equal to 15 lbs. air pressure.
Note. — In order to convey to
the mind the relationship be-
tv.cen quantities, such as be-
tween volume and pressure, the
expressions ' ' varies directly "and
"varies inversely" are used.
The expression " varies directly "
is used to convey to the mind
F, £ 57.— WocJ-boring Machine the idea that one quantity grows
Operated by Compressed Air. , ... ^ * .

larger in the same proportion as
the other. When the relation between two quantities is such that
one quantity grows larger in the same proportion as the other grows
smaller, the first quantity is said to vary "inversely" as the other.

97. Pneumatic Tools. — A pneumatic tool consists of a
cylinder with a handle, which contains a working (percus-
sion) piston with various air ports, a cap nut, and a spring.
Air is usually supplied to pneumatic tools from air tanks. The

PROPERTIES OF GASES 95

air is pumped into the tank by means of a motor and a pump
and the pressure in the tank is regulated to 7 atmospheres,

the motor starting and stopping automatically. The air is con-
ducted through flexible tubes lined with materials capable of

Pig. 59. — Pneumatic Drill. Partly in section.

withstanding this working pressure of 7 atmospheres. Figures
57, 58, and 59 show important types of pneumatic tools.

96 APPLIED SCIENCE

98. The Use of Compressed Air in a Sand Blast — Sharp
sand under air pressure is used in etching or frosting glass
and cleaning castings. The pressure of the air and hardness
of the sand is governed by the class of work.

A sand blast outfit includes a sand blast machine, hose
and nozzles, and a standard air compressor of the size and
pressure capacity required by the conditions of the work,
together with a good-sized air receiver with the usual gauges,
safety valves, and drain cocks. If air is already in use at
the location, at higher pressures than required for the sand
blast operation, a pressure reducing valve may be installed,
leading preferably to a separate receiver which will be main-
tained at the proper pressure for the sand blast operation.

A clean, sharp sand, thoroughly dried, will give best results,
and it is essential that the air used with the blast be kept as
dry as possible by the installation of blow-off cocks, and
occasionally "U" loops introduced in the line of air piping,
with drip cocks installed at the bottom of the loops; or by
the ordinary bucket steam trap. Sand especially suited to
the operation can be obtained from manufacturers of the
sand blast machines..

For etching on, or frosting glass, a pressure of 2 to 5 lbs.
is ample; for cleaning brass castings and removing core
sand, 15 to 20 lbs.; for cleaning the general run of iron cast-
ings, 15 to 20 lbs.; and for steel castings, 30 to 75 lbs.

99. Siphon. — In commercial and industrial plants it is
often necessary to remove a liquid in a small stream from a
large cask, without disturbing a sediment, to fill smaller
receptacles. This is particularly true in the case of corrosive
liquids, like acids, ammonia, etc., where there is great danger
in pouring the liquid from the cask. In such cases the task

PROPERTIES OF GASF.S 97

is accomplished by means of a rubber tubing or bent glass
tubing with unequal arms. This apparatus is called a siphon.

The principle of the siphon is explained as follows: In order to
start the siphon it is necessary first to remove the air from it. This
is done either by filling the siphon with water and placing a thumb
at each end of the siphon, then placing the smaller end in the water
that is to be removed from the vessel, or by drawing the water up
through the long end of the tube. The water in the tube is
driven toward the longer arm by a force equal to the difference
in the weight of the water in the two
arms. The difference in the lengths of
the arms should be great enough to over-
come the friction in the pipe and the
weight of the water in the short arm.
When this happens the water falls out of
the long arm and tends to leave a vacuum
at the top, but atmospheric pressure forces
the water up the short leg to fill this space.

The tube ABCD (Fig. 60) is a siphon.
The shorter leg.-i.tt is put into the liquid

H, which is to be drawn off into (1. If the p la so _si p hon.

air be taken out of the tube the pressure

of the air on the surface of the liquid E will force the liquid up
the tube AB, and it will then fill the whole tube and continue to
run until all the liquid in E has run into the vessel G.

Questions

1. Why do clothes dry more quickly on a windy day than on
a quiet day?

2. Does sprinkling the street on a hot day make the air cooler?
If so, why?

3. In what part of the summer is the heat oppressive? Explain.

4. What becomes of the cloud of steam that escapes from the
exhaust pipe of a power plant or a blowing locomotive whistle?

6. When does moisture gather on a water pipe? Why?

6. Why does the morning fog disappear usually before noon?

98 APPLIED SCIENCE

7. Why do we fan ourselves when we perspire?

8. Why must the bung of a barrel be removed in order to secure
a proper flow of liquid from the faucet?

9. Why does high mountain climbing often cause pain and
bleeding in the nose?

10. Small packages and folded papers are often transmitted in
a carriage by air pressure through brass tubes called pneumatic
dispatch tubes. An exhaust pump is attached to one end of the
tube in which a tightly fitting carriage moves, and a compression
pump to the other. If the air is half exhausted at one end and has
twice its density at the other end, find the propelling force on the
carriage if the tube is 4 in. in diameter.

11. Explain why it is impossible completely to exhaust a vessel
of air by an air pump.

12. A pneumatic hammer, often called an "air gun,"' is used to
drive rivets. Explain how it works.

13. Explain the care of a pneumatic hammer.

14. What is the practical value of a barometer? Explain the
principle of a barometer.

15. Why is compressed air used in building a subway?

16. What advantage has compressed air over electricity in
transmission of power?

17. Give some of the advantages of a pneumatic tire over a
solid tire of the same size.

18. The general shape of boats and air-ships is usually made to
conform to that of a fish. Why?

19. What is a fog?

20. What is a cloud?

21. Why is a bottle of hot water better than a hot stove cover
for keeping your feet warm in bed?

22. Explain the principle of science underlying pneumatic
machines.

23. Is it possible to measure gas pressure with the same gauges
that are used to measure the pressure exerted by liquids?

24. How is air compressed? What is the commercial method
of compressing air?

CHAPTER IX
HEAT AND EXPANSION

100. Generation and Movement of Heat. — If we file a
soft iron nail for a moment and then feel the file surface,
we find that it is warm or hot; that is, the surface of the file
is warmer than the body. Another way of expressing the
same idea is to say that the temperature of the surface of the
file is higher than that of the body. There is then a transfer
of heat from the warmer body to the colder body, until both
are equally warm. Then both bodies are said to have the
same temperature. A hot frying pan when plunged into
a bucket of water gives off heat to the water, until the
temperatures of the water and the frying pan become equal.
Temperature is a measure of the tendency of a body to give up
its heat to other bodies.

The surface of the file becomes warm or hot because of
friction. The same effect is produced on the surface of a
saw in sawing wood, in rubbing a metal surface on cloth, in
» the bearings of moving car-wheels, etc. Heat is generated
also when a piece of lead or other metal is hammered and
when a rifle bullet strikes a wall. This heat is caused by
percussion.

Heat is also produced by compression, chemical means,
and electricity. For example, the temperature of air is
raised when it is compressed in a bicycle pump; when

100 APPLIED SCIENCE

muriatic acid is added to zinc the chemical reaction which
takes place produces heat; a current of electricity passing
through a piece of platinum raises the temperature of the
platinum.

Two very common effects of heat noticed in every-day
life are the changes in length, surface, or volume of mate-
rials, and the changes of state — from solid to liquid and from
liquid to gaseous. Since heat is due to the motion of the
particles that compose a body, it will expand as the rate of
motion is increased. This principle is utilized when the
blacksmith first heats a tire before putting it on a wheel so
that when the tire contracts as it cools it fits closely. For
the same reason, rivets are made red-hot before they are
put into boilers, bridges, or steel structures. When cool they
contract and draw the parts tightly together.

Heat travels in three distinct ways: by conduction, by
convection, and by radiation.

When a poker is placed in a fire, the heat passes along
the poker from the hot to the cold part; this action illus-
trates conduction. Heat passes through some materials
more readily than through others; materials of the first
class are called good conductors and those of the second
class, poor conductors. Iron, for instance, is a good conductor
and wood a poor conductor of heat.

The heat from a stove passes through the air without
any apparent motion; movement of heat in this manner is
called convection.

Heat comes to us from the sun; this method of trans-
mission of heat is called radiation.

101. The Manufacture of Thermometers. — For the meas-
urement of modern temperatures there are two standard

HEAT AND EXPANSION J 101

j ^ ■* j - -

thennometers: the Fahrenheit used in this country and
England for ordinary purposes, and the Centigrade used in
Continental countries, and by scientists.

A thermometer consists of a cylindrical glass tube of a
uniform bore and diameter, sealed at one end. A fluid is
first placed in the tube, which then is heated until the fluid
expands ahd fills the tube, thereby driving out the air.
It is necessary to create a vacuum; otherwise the air would
prevent the fluid from expanding in the closed tube. After
the air has been driven out the tube is sealed. It is then
placed in an atmosphere of free steam representing the boil-
ing point of water, and next in an ice bath consisting of
broken pieces of ice floating in water. The positions of
the liquid at both of these points are marked on the tube,
the boiling point representing 212° F. and the freezing
point 32° F. The intervening distance between these two
points is divided into 180 divisions and each division is
called a degree. The Centigrade thermometer has 100
divisions between these two points. Mercury is especially
adapted for use in thermometers on account of the uni-
formity with which it increases in volume, and also on
account of its extremely high boiling point. Alcohol
colored with some dyestuff is used in cheap household
thermometers.

102. Measurement of Temperature in Industry. — Ther-
mometers assist us in comparing or fixing the temperature
of certain industrial operations. This is important, as in a
great many manuf ajcturing operations it is necessary to know
when a certain temperature is reached. As a result a num-
ber of different kinds of thermometers have been invented.
They are all based upon the same principle as are the Fahren-

* •

• • •

102
heit

•7* * .*/••••••

* # * ,, " ...AP?LiEt) Science

'and Centigrade thermometers, namely, that substances
r\ expand with an increase and contract with a
decrease of temperature. In the measurement
of heat in stoves and furnaces where the tem-
perature exceeds 900° F. an instrument called
a pyrometer* is used.

103. Relation between Fahrenheit and Centi-
grade Scales. — While all temperature measure-
ments in American and English shops are
expressed according to the Fahrenheit scale,
it is often necessary to change the Fahrenheit
into the Centigrade readings. Below is given

„ „ _ a comparison of the two at the boiling and
Fig. 61.-Cen- . ** . . 6

tigrade and freezing points, together with conversion for-

Fahrenheit j^ui^ f or use } n changing readings from one
standard to the other. (Figure 61.) Fahren-
heit is denoted by the letter F. and Centigrade by the
letter C.

Boiling Point

Fahrenheit Scale 212°

Centigrade Scale 100°

To convert Fahrenheit to Centigrade:

5 (F - 32)

= C

To convert Centigrade to Fahrenheit *

C + 32 = F

Freezing Point

32°

0°

* For a description and illustration of the pyrometer see Chapter
XV.

HEAT AND EXPANSION 103

This rule may be stated as follows:

To convert Fahrenheit to Centigrade subtract 32° from the
Fahrenheit degree and divide by 1.8, or take j of it.

To convert Centigrade to Fahrenheit multiply the Centigrade
degree by 1.8, or \, and add 32.

Example 1. — Convert 212° F. to Centigrade reading.

5(212-32) (180) 900

— - = 5 = — = 100° C.

9 9 9

or 212 - 32 =180

180 + 1.8 = 100° C.

Example 2. — Convert 100° C. to Fahrenheit reading.

9(100) 900

— + 32 = + 32 = 180 + 32 = 212° F.

5 5

or 100 X 1.8 = 180

180+32 = 212° F.

104. Heat Units. — The unit of heat that is used in the
industries and shops of England and America is the British
thermal unit (B. T. U.) It is the quantity of heat required to
raise 1 lb. of water to a temperature of 1° F. Therefore, the
heat required to raise 5 lbs. of water through 15° F. is

5 X 15 = 75 B.T.U.

Similarly 72 lbs. of water require, to raise its temperature

72 x Yt = 36 B.T.U.

The unit that is used on the Continent and in scientific

circles in America is the metrfc system unit called a calorie.

A calorie is the amount of heat necessary to raise 1 g. of

water 1° C,

104 APPLIED SCIENCE

106. Latent Heat — Examine a pan of water over the fire.
Note that the heat passes first to the particles of the pan, then
to the water nearest to the source of heat. As these parti-
cles expand, they become lighter and pass to the surface
of the water. This process continues until the whole mass
of water reaches a uniform and fixed temperature called the
boiling point — 212° F. under ordinary conditions. In the
generation of steam under pressure higher than the ordinary
air, the boiling point varies, increasing in proportion to the
pressure. With a pressure of 16 lbs. to the square inch, water
boils at 212.1° F.; with a pressure of 20 lbs. at 228.4°, etc.

After the boiling point has been reached the temperature
of the water remains constant, however long the heat is ap-
plied to the vessel. The steam bubbles will rise rapidly,
the whole mass will be in a state of agitation (ebullition),
and the steam vapor will be given off in large quantities.
The heat that is absorbed and given off without raising the
temperature of the water is catted the latent heat of the steam.
This latent heat is either lost or dispelled in the air or is
given off when the steam is condensed.

When a substance is heated as it passes from the solid
to the liquid state, and from the liquid to the gaseous state,
a certain amount of heat is expended in molecular work,
separating the molecules of the substance without raising
the temperature. The heat thus absorbed or lost is spoken
of as latent. For example, when a pound of ice is heated its
temperature remains the same until the melting point (32° F.
or 0° C.) is reached; further application of heat, however
intense, will cause no further rise in temperature until the
ice has been entirely melted. Experiment shows that 144
B.T.U. are required to convert a pound of ice into water at
32° F. Further application of heat causes a rise in tempera-

HEAT AND EXPANSION 105

ture, 180 B.T.U. raising it to the boiling point (212° F.,\
Xhe rise in temperature ceases until all the pound of water
at 212° F. has been converted into steam, which requires
970.4 B.T.U. This is called the latent heat of vaporization
of water. When the steam is condensed to water, the same
amount of heat is given off.

106. Steam Pressure. — When steam is generated under
ordinary conditions it is termed "steam of one atmosphere"
(15 lbs. per square inch). One cu. in. of water will produce
approximately 1 cu. ft. of steam (1728 cu. in.). If the
pressure is increased the volume is diminished; i.e., the
pressure varies inversely as the volume. Thus with a pres-
sure of 30 lbs. the volume is only one-half of what it. would
be under normal pressure. One cu. in. of water produces
864 cu. in. of steam under 30 lbs. pressure.

P :P' =V':V
15 : 30 = V : 1728
30 V = 15 X 1728
15 X 1728

30
V = 864 cu. in.

107. Specific Heat. — If equal amounts of copper and
water are heated, it becomes evident that it takes a great
deal more heat to raise 1 lb. of water 1° F. than to raise 1 lb.
of copper. The unit of heat has already been defined as
the amount of heat necessary to raise the temperature of
1 lb. of water 1 F. The quotient obtained by dividing the
amount of heat required to raise the temperature of the substance
one degree Fahrenheit and that required to raise the tempera-
ture of an equal mass of water one degree is called the specific

106 APPLIED SCIENCE

heat of the body. To illustrate: The specific heat of lead is
.031 while the specific heat of water is 1. This means that
it would require 31 times as much heat to raise 1 lb. of water
one degree in temperature as it would to raise the temperature
of 1 lb. of lead one degree.

The following table gives the specific heat of the different
substances in which the mechanic and engineer are most
interested.

Table of Specific Heat

Water at 39.1° F 1.000 Copper 095

Ice at 32° F 504 Lead 031

Steam at 212° F 480 Coal 240

Mercury 033 Air 238

Cast Iron 130 Hydrogen 404

Wrought Iron 113 Oxygen 218

Soft Steel 116 Nitrogen 244

108. Boiling Point and Vacuum Pan. — At the sea level,
with an atmospheric pressure of 29.922 in. of mercury in
the barometer — in other words at a pressure of 15 lbs. on
the square inch — water boils at a temperature of 212° F.
(100° C). Above this level, the layers of atmosphere be-
come less dense and consequently exert less pressure. The
boiling point is, as a result, reduced several degrees below
212° F. With an increase of atmospheric pressure, as found
in a deep mine, the reverse takes place, and water requires
the application of several degrees of heat above 212° F.
before it actually boils.

This variation of the boiling point of water under different
pressures is taken advantage of in many manufacturing
processes by the use of the vacuum pan. Under a reduced
pressure, produced by mechanical means, liquors can be

evaporated and concentrated in the vacuum pan without

HEAT AND EXPANSION 107

injury to the active ingredient they contain. By working
under a low pressure, clarified sugar juices, food extracts,
glycerin, dyewood, gelatin, and other liquors can be con-
centrated to any desired extent without injury. If such
liquors were heated to a temperature of boiling water for any
prolonged period, as would be necessary were they evaporated
in an open pan, their nature or constitution would to a greater
or lesser extent undergo a change and they would be spoiled.
For vacuum evaporation, a pump is necessary, first for
exhausting the air and the steam from the vacuum pan and
then for sending both to a vessel called a condenser where
the vapors are condensed. One of the most practical devices
is called the multiple effect system. This device consists of
four simple vacuum pans so connected that the steam from
the boiling liquid of the first is made to pass through the
others. In this way the heat of the steam of the first pan
is sufficient to heat the liquid of the second to the boiling
point, the heat of the steam of the second raises the tempera-
ture of the third, and so on.

109. Expansion of Metals. — Heat causes metals to ex-
pand. The expansion of unit of length for one degree is called
the linear coefficient of expansion. The increase per degree for
unit of surface is called surface expansion; for unit of volume
it is called cubic expansion. A steel joist 3 ft. long is, for
example, about Y% in. longer in summer than in winter;
hence long steel structures must not be rigidly fixed at
both ends. Steel car-rails are laid about 3^ in. apart to
allow for expansion. The amount of expansion of various
substances in length, area, and cubic contents or capacity
is given in the following table. For each degree of heat the
metal expands the fraction of an inch indicated.

108

APPLIED SCIENCE

Coefficients of Expansion (1°F.)

Name of Substance

Linear

Cast Iron

Copper

Brass (plate)

Silver

Iron (wrought) . . .
Steel (untempered)
Steel (tempered) . .
Zinc

.00000556
.00000887
.00001052
.00001079
.00000648
.00000606
.00000689
.00001407

Surface

.00001112
.00001774
.00002104
.00002158
.00001296
.00001272
.00001378
.00002814

Cubic

.00001668
.00002661
.00003156
.00003237
.00001944
.00001908
.00002067
.00004221

110. Expansion of Substance. — When a substance con-

sisting of two or more bodies which have different coefficients
of expansion undergoes any change of temperature, it is
subjected to stresses, since its various parts do not expand
in an equal degree. Thus, Portland cement, which has a
coefficient of expansion of .000011, cannot make a reliable
joint under varying temperatures with leading, the coefficient
of which is .000028. On the other hand, the coefficient for
steel fortunately approaches very closely to that of concrete,
so that these materials may be combined to advantage in
construction work. In the case of brittle substances fixed
together, this unequal expansion is a frequent source of
fracture. The cracking of glaze upon tiles and terra cotta
may be attributed to this cause. The plastering on walls
and the seams of cheap wall-paper sometimes open on
account of unequal expansion.

Allowance for expansion in non-metallic bodies, such as
stone, brick, or concrete, is not usually of importance because
the coefficients of expansion of such bodies is as a rule smaller

HEAT AND EXPANSION

109

and the specific heat higher than those of metals. For this
reason they require more heat to produce a given rise in
temperature than do the metals.

The expansion of a number of common substances used
in building construction is given below.

Linear Expansion of Solids at Ordinary Temperature

Substance

Far 1° F.

Aluminum, cast

Brick, best stock

Zinc

Cement, Roman, dry

Cement, Portland, mixed, pure. . . .
Cement, Portland: mortar mixed

with sand

Concrete: cement, mortar, and

pebbles

Copper

Ebonite

Glass, English flint

" French flint

" white, free from lead

" blown

" thermometer

" hard

Granite, gray, dry

red

.00001234
.00000310
.00001407
.00000797
.00000594

.00000656

.00000795
.00000887
.00004278
.00000451
.00000484
.00000492
.00000498
.00000499
.00000397
.00000438
.00000498

Far 1° C.

.00002221
.00000550
.00001755
.00001435
.00001070

.00001180

•

.00001430
.00001596
.00007700
.00000812
.00000872
.00000886
.00000896
.00000897
.00000714
.00000789
.00000897

There are a few substances, of which water is perhaps the
most common, that do not follow the rule of expansion and
contraction. When a body contracts, its density, and there-
fore its weight per cubic inch or cubic foot, increases and we
say that it beCQmes heavier, Water freezes at 32° F. and

110 APPLIED SCIENCE

ice floats at 34° F. showing that it is lighter than water.
Careful investigation reveals that water is heaviest at 39° F.

(4° C).

111. Drying and Evaporation. — The theory which under-
lies the process of drying is that dry air is capable of absorb-
ing moisture; hence by circulating currents of dry air in
and around wet substances, the absorbing power of the air
draws off the moisture. For continuous drying, free cir-
culation is a necessity, as air soon becomes saturated and
incapable of taking up more moisture. Warming the air
increases its capacity to absorb moisture; thus air at a high
temperature is capable of drying material much more quickly
than the same volume of air would at a low temperature.
A free circulation of air at 85° to 100° F., evenly distributed,
and with ample provision for the escape of the saturated air,
is essential for good drying work.

Experience shows that when a liquid passes into a gaseous
state it absorbs heat from the surrounding bodies. To il-
lustrate: If a few drops of ether were placed on your hand
you would notice the ether disappear in the form of a vapor
by reason of the process termed evaporation, and your hand
would feel cold. Evaporation produces coldness. Experi-
ence also shows that in condensing a gas by pressing the
particles together, heat is given off. Thus the pressure on a
gas, that is, its compression, generates heat, while the libera-
tion of particles produces cold.

All gases may be liquefied by increasing the pressure suffi-
ciently. If this pressure is suddenly removed the gas will
evaporate quickly and expand, thereby absorbing heat and
reducing the temperature of the surrounding bodies.

These scientific facts are taken advantage of in refrigerat-

HEAT AND EXPANSION 111

ing plants, described in Chapter VIII, where ice is manufac-
tured by means of the expansion of ammonia which is the
most economical gas to liquefy.

Questions

1. When is a body hot?

2. When metals begin to melt, they liquefy at once. Why?

3. Why is ice packed in sawdust?

4. Why does a draft extinguish a flame?

5. Which will heat more quickly, rough or polished surfaces?

6. Why does sprinkling a shop floor cool the air?

7. Why are steam cylinders polished on the inside?

8. Why are glass tumblers broken by pouring hot water into
them?

9. What is the basis of all cooling mixtures?

10. Explain why so much energy is lost in steam engines.

11. Is temperature a measure of the amount of heat in a body?

12. Explain why railroad engines have a polished sheet iron
jacket around the cylinder and boiler.

13. What becomes of the cloud which forms about a blowing
locomotive whistle?

14. Why are expansion joints added to long lines of steam pipes?

15. Place a ball through a ring, then heat the ball in an alcohol
or Bunsen flame and try to pull it back through the ring.

16. Why do mechanics who work in a warm room wear flannel
shirts to keep cool in the summer and warm in the winter?

17. Why is felt a better conductor of heat when firmly packed
than when loosely packed?

18. Ducts and pipes are frequently covered with felt or asbestos.
Why?

Problems

1. Change the following Fahrenheit readings to Centigrade
readings: 56°; 75°; 5°; 0°; -23°; 45°; 54°.

2. Change the following Centigrade readings to Fahrenheit
readings: 0°; 68;° 44°; -17°.

112 APPLIED SCIENCE

3. How many units (B.T.U.) will be required to raise 4863 lbs.
of water 62° F.?

4. How many units (B.T.U.) will be required to raise 785 lbs.
of water from 74° F. to 298° F.?

5. How many units of heat will be necessary to raise 40 g. from
50° C. to 70° C?

6. A wrought iron bar 22 fl. long is heated from 70° F. to 300°
F. How much will it lengthen?

7. A straight pipe 256 ft. long is heated from a tempera-
ture of 50° F., to a temperature of 370° F. How much will
the pipe expand? How much would a brass pipe expand
under the same conditions? (Coefficient of expansion of brass is
.00001052. Coefficient expansion of iron is .0000065 ft. per foot
of length per degree Fahrenheit.)

8. A bar of copper 12 ft. 6 in. long at 82° F. is heated to 289° F.
What is its length while it is at 289° F.?

9. A brass rod measuring 36 ft. 3 in. at 78° is heated to 188° F.
What is its greatest length?

10. A flat surface of zinc measuring 4 ft. 6 in. is heated from 81°
F. to 312° F. How much does the surface expand?

CHAPTER X
LIGHT, COLOR, AND SOUND

112. Characteristics of Light. — We see objects by means
of what we call light. Light comes from the sun by means
of vibrations and produces an effect on the eye. These
vibrations may also come from illuminated objects, but such
objects give off only waves of light that fall on them from
some other source. Bodies which give out light waves
directly from themselves are called luminous; those that
do not are called non-luminous. Light travels to our eyes
very rapidly, and always in straight lines. A line of light
is called a ray. A number of rays are called a beam of light.

Light passes through some objects, such as a piece of glass,
very readily. Such objects are spoken of as being trans-
parent. If light passes through a body with difficulty, the body
is said to be translucent. When light fails to pass through
a body at all, the body is said to be opaque. In this latter
case, the light passes by the extremities or outline of the
object, and a shadow is erected.

Objects may also be seen by means of reflected light. When
rays of light fall on
a smooth, opaque
body, which is pol-
ished, they are re-
flected at the same p IG . 62.— Regular Re- Fig. 63.— Irregular Re-
angle at which they flection of Light. flection of Light,

Strike the surface (Fig. 62). These reflected rays form an
8 113

114 APPLIED SCIENCE

image. When the image is quite distinct, the surface is called a
mirror. When the surface is rough the rays are not reflected
regularly, but at different angles (Fig. 63). This action is
called diffused reflection. Diffused reflection throws the
rays of light in all directions and assists, therefore, in illumi-
nation.

113. Refracted Light. — Light travels faster in a rare
than in a dense substance. Therefore when a ray passes

from a rarer to a denser sub-
stance, it is bent on entering and
on leaving the denser substance,
and in both cases the refraction
or bending is toward its base
(Fig. 64). When light passes

from the air through water
Fig. 64. — Refraction of Light. „ ,

or a prism, the rays are bent.
This fact is taken advantage of by manufacturers and
others who are located in thickly settled communities,
where the streets are narrow and the buildings are high.
The upper panes of the windows are then made of a
peculiar combination of prisms and lenses. By means of
this device, the rays of sunlight in the street or yard are
deflected from their original direction and projected and
diffused into the stores, rooms, and basements. All forms of
prismatic glass reflect the rays of light downward.

114. Composition of Uluminanjs. — All practical illu-
minants are made of carbon brought to incandescence
(glowing). The types of illuminants fall into two classes:
first, particles heated by the combustion of their own carbon,
such as candles, lamps, and gas flames; second, particles of

LIGHT, COLOR, AND SOUND 115

carbon heated by outside means, such as mantle gas-burners,
electric incandescent lamps, electric arc lamps, etc.

A flame is caused by the glowing of solid particles that
have been volatized, converted into vapor, and rendered
luminous by intense heat. The flame of a common lamp
or candle is produced by the oil or melted tallow rising be-
tween the fibers of the wick through capillary attraction
(attraction which causes liquids to go up into minute open-
ings). When the wick is ignited, the oil is heated to a state
of vapor, which inflames as the oil first raised is used in burn-
ing. Other portions are attracted up the fibers, become
vapor, and are burned likewise. In this way a constant
and steady combustion is maintained. The flame of a lamp
is hollow, not solid, as the heated vapor must combine
with oxygen before combustion can ensue. Hence, only
the portions that come in contact with the air are trans-
formed into flame. The vapor that rises from the wick in
the center rises unburned. The hollow part of the flame
is indicated by the darker and less luminous portion seen
just above the wick.

115. Standard of Light. — The only standard of light
used in this country is the English standard candle. The
unit is one candle-power, which is the amount of light given
off by a spermaceti candle, weighing 1200 g. and burning
120 grains per hour. Photometry is that part of the science
of light that deals with the measurement of luminosity.

116. Importance of Proper Lighting. — The problem of
an adequate amount of light presents itself to every manu-
facturer and city-dweller. With the increasing value of
space and the constant crowding of buildings, the natural

116 APPLIED SCIENCE

source of light, the sun, has been shut off in a great many
buildings. The result is that artificial illumination in the
daytime is a practical necessity. When such artificial
sources of light are used in place of sunlight they must
meet the needs of the eye and be installed with that aim
in view.

Light should not shine directly into the eyes, but directly on
the object we wish to see. The paper that gives the great-
est amount of diffused reflection is white blotting paper.
Dirty paper does not diffuse light as well as a clean, white
board. White painted surfaces diffuse light well. Green,
red, and brown surfaces have low diffusive values. Color
on the walls of rooms and shops produces an effect upon
the color of objects within the room. Any strong color
on the wall will furnish a colored component of the total
light.

Shades and reflectors are used either to modify the colors
of the radiating object or the brilliancy of the source, so
as to keep too bright a light out of the eyes, or to modify
the distribution of light so as to put it where it will be of
most service.

117. Incandescent Lamps. — The most common form of
electric lighting at the present time is the incandescent lamp.
It consists of a slender filament of some highly resisting
material prepared from carbonized paper or bamboo and
enclosed in a glass bulb. The ends of the filament are con-
nected to platinum or lead wires fused in the glass. One of
the wires is connected with the base of the socket, and the
other with its rim. The intervening space is filled with
white cement, which is a non-conductor. An attachment
is placed on the socket by which the current enters and

LIGHT, COLOR, AND SOUND 117

leaves the lamp. The air is exhausted from the bulb as
completely as possible, and the exhaustion tube sealed off.
When the electricity passes through the filament, it glows
on account of the great resistance, but because of the lack
of air does not burn. The glowing particles of the filament
give off the illuminating rays. The way in which the light
is distributed from the lamp depends upon the form in which
the filament is bent.

When certain metals with a very high melting point, such
as tungsten, osmium, etc., are made into fine wires or fila-
ments, they possess remarkable endurance and a high degree
of efficiency.

118. The Nerast Lamp. — The Nernst lamp has a filament
of compressed oxides of certain rare metals. This filament
conducts electricity only when heated to a high temperature,
and as it is not combustible it need not be enclosed in an
exhausted vessel. A small encircling coil of platinum wire
(called a heater) through which a current of electricity passes
brings the filament to incandescence.

119. Arc Lamps. — The ordinary arc light is formed be-
tween two carbons. When a current of electricity is passed
through these carbons, the great resistance offered causes
the ends of the carbon to become very hot and to glow. As
the carbon gradually burns, the distance between the ends
becomes greater. An automatic attachment by which the
lower carbon is raised, keeps the distance between them
constant.

120. The Drummond Light. — The Drummond light is pro-
duced by exposing small pieces of lime to ignition in a blow-

118 APPLIED SCIENCE

pipe. Oxygen and hydrogen gases are. directed upon the
ball or disk of lime from separate vessels or gasometers through
a flame arising from alcohol. This light, invented by Cap-
tain Drummond, is probably the most powerful known, and
can be seen a distance of 30 miles. It is now much used for
light-houses.

121. Gas Lighting. — Luminosity depends upon the re-
flection of glowing particles, and since a yellow flame heats
many of these small particles of carbon, it gives off more
light than does a blue flame. Consequently, the yellow flame
is extensively used for gas lighting. The most effective
gas light is produced by using a mantle. (A mantle is a
screen which glows when the gas is lighted.)

122. Natural Gas. — A form of gas called natural gas is
obtained from the earth by drilling a deep well. Such gas
is formed as the result of decomposition of organic matter
under pressure and heat. It comes to the surface often
under great pressure and requires but little preparation for
use. In different districts natural gas is of different composi-
tion, but its principal constituent is always "marsh gas,"
a compound of carbon and hydrogen that has a very low
lighting but a very high heating value. It is used for both
heating and lighting.

123. Manufactured Gas. — Manufactured or artificial gas
is used in most places in this country and is made by
heating coal gas, that is, gas obtained by distilling coal.
Artificial gas is used for both heating and lighting, but its
cost tends to be prohibitive for the former purpose.

LIGHT, COLOR, AND SOUND

119

124. Light and Color. — The color of a body depends on
its nature, and the light in which it is viewed. A scheme of
color that is harmonious by daylight may be just the opposite
at night when viewed by artificial light. Different bodies
or substances, like dyestuffs, etc., owe their property of color
to the light that falls on them, and not to the body or sub-
stance itself. This fact may be illustrated by allowing
different colored lights to fall on the same substance, and
noticing the colors thus produced.

Sunlight, as any other light, comes to us in the form of
waves vibrating at different rates. Each wave is one color,
and when they are mixed in a beam they produce white
light. Light may be separated into different colors or wave
lengths, by means of a triangular prism of glass, whereby
the rays are refracted and those with the greater vibra-

ULTRA-VIOLET

•**

ft*

«3

INFRA-RED

&}
^

«5

INVISIBLE RAYS INVISIBLE RAYS

EG.

65.

— S

pec

itru

tion are bent more. In this way sunlight is separated
into its component parts. The colors thus obtained make
up what is called the spectrum (Fig. 65). The spectrum
contains red, orange, yellow, green, blue, indigo, and violet rays.
These rays are not all of the numerous components of white
light, but only the principal or primary ones.

Light in a dry goods store, where fabrics are displayed,
should be diffused daylight, while in a ballroom a softer light,
rich in yellow and orange tints, is preferable. Every opaque
object assumes and reflects a color. A piece of red cloth

120 APPLIED SCIENCE

looks red because it selects from white light mainly red for
reflection.

125. Theory of Color.— Sunlight is called white light, and
is, as just noted, composed of all the colors of the rainbow.
When sunlight falls upon a body, a part of the light is ab-
sorbed by the body and converted into heat. The rest of
the light is reflected to the eye and renders the body visible.
If the body reflects all the colors of the rainbow equally,
then the body is white. If the molecules of the body absorb
certain compound colors of sunlight, then the reflected light
is deprived of those particular colors. To illustrate: If blue
is absorbed, the light reflected will be deprived of this primary
color and the active remaining color which is red will pre-
dominate. Thus, the body will appear red.

This theory of light has been used to advantage in protect-
ing the eyes of the workmen engaged in electric and oxy-
acetylene welding. When metals are heated to a very high
temperature, the eyes of the workman may be damaged by
the repeated flashes of brilliant light from the glowing metals.
Very careful experiments show that certain rays in large
amounts, such as the ultra-violet rays and the infra-red
rays, are harmful. Such rays are present in the working of
molten iron or steel, or any incandescent material, where
the temperature is 2000° F. or more. Special colored
glasses or lenses will neutralize or cut out these dangerous
rays.

126. Table of Colored Lenses. — The following table indi-
cates the kind of colored lenses which should be used to nullify
or prevent any injury tp the eyes from the industrial pro-
cesses tabulated below,

LIGHT, COLOR, AND SOUND

121

Group

Process

Approx.
Tempera-
ture (F.)

Correct
Color*

Open-Hearth Steel

Charging machine

3400°

S+AZ

Steel pourers

2800°

S +AA

Platform men

3000°

S+AZ

Melters

2800°

Special blue

Crucible Steel

Melting floor

3400°

S+AZ

Hand-pouring

2800°

S +AZ

All-steel pouring

2800°

S+AA

Bessemer Steel

Pulpit operators

3600°

Bessemer

Blowing steel

3600°

Pouring in molds

2800°

S +AA

Blast Furnace Steel

Tapping

2800°

S +AA

Tuyeres

3500°

Special blue

Wrought Iron

Puddling Furnace

2800°

S +AA

Furnace

Gas heating

2500°

AK+D

Electric heating

5000°

S +AA

Large electric heating

6000°

S +AZ

Welding

Oxyacet. cutting

4000°

S +AA

Oxyacet. welding

4350°

S +AZ

Light spot welding

S +AA

Heavy spot welding

S +AZ

Iron arc welding

5500°

S+AZ

Carbon arc welding

6450°

Arkweld

I^ipweld

AK+D

orS +AA

Symbols used by opticians.

122 APPLIED SCIENCE

127. Characteristics of Sound Intensity. — When a ham-
mer strikes a piece of metal a noise is produced. The sound
is caused by the particles of the two separate metals vibrating.
The vibrations are transmitted through the air in a series of
waves. The presence of the vibrations can be detected by
pressing a stiff piece of cardboard against the surface or side
of the metal when it is struck.

Sound possesses three properties — intensity or loudness,
pitch, and quality — by which one sound may be distinguished
from another. The intensity of a sound depends upon the
density of the medium through which the sound is trans-
mitted and upon the amplitude of the sound waves which
reach the ear. The intensity varies inversely as the square
of the distance. The waves become smaller and smaller as
they leave the point at which the sound is produced, because
the quantity of air through which the sound is conveyed be-
comes greater and greater. In other words, the intensity of
sound decreases as the distance from the source of sound increases.

All forms of speaking tubes are based upon the principle
that the sound waves set in motion in the tube are confined
to the air space of the tube. Therefore the sound is trans-
mitted without any decrease in intensity.

128. Pitch and Quality. — Pitch is the property of sound
which determines whether the sound is high or low. Pitch
is determined by the number of vibrations per second made by
the sounding body. Comparatively slow vibrations produce
a low sound, while rapidly vibrating substances produce a
high-pitched sound. This difference may be quickly ob-
served by entering a machine shop where the machines are
running at a low speed and comparing the low drill sound

to the high-pitcbed sound produced in a woodmill where

LIGHT, COLOR, AND SOUND 123

the machinery is running at a high speed. Low speed gives
a low vibration, while high speed gives a quick vibration
It is possible to detect the difference in the sound produced
by two bodies of different composition, but with the same in-
tensity and pitch. The property of sound by which we are able
to distinguish this difference is called quality. Quality depends
upon the form of the vibrations.

Questions
Light and Color

1. Petroleum oil looks bluish green when it is on the water.
Why?

2. Smoke and fine particles that float in the air deflect the
short waves of light more than the long ones. Why? Why is the
sky blue? Why is the sun red after a forest fire?

3. Should colors that are to be worn in an artificial light be
selected by sunlight or by the artificial light?

4. Why does a piece of red cloth appear black when seen by
blue light and red by red light?

5. Why is it desirable to have school windows reach to the
ceiling?

6. Why is it desirable to have the light for writing come over
your left shoulder?

7. Tell the advantages of rough gray plaster.

8. Why does a diamond sparkle?

9. Upon what principles may imitation stones be made?

10. When is a substance black?

11. Is black a color?

12. Is white a color?

13. Why are white clothes worn in the summer?

14. Why is a room with light walls better to work in than one
with dark walls, even when the same amount of light comes in the
room?

15. Why do rivers appear shallower than they really are?

124 APPLIED SCIENCE

16. Explain why a reddish lamp-shade makes a room more
cheerful at night.

17. Colored lights are often seen in fireworks. What causes
them?

Sound

1. An electric light bulb makes considerable noise when it
breaks. Why?

2. How may a rotten spot in a wooden beam be detected?

3. Why is it that persons often hold the hand behind the ear
that they may hear?

4. Watch a circular saw starting through a board and notice
that the pitch of the buzzing tone is high. Why?

5. Why does the pitch fall soon after the saw enters the board?

6. Tap a steam pipe with a hammer. Can the sound be heard
on the floor above?

7. If you burn gunpowder in the air it does not make a noise.
If the gunpowder explodes in the cannon it makes a loud noise.
Why?

8. Explain how a speaking tube acts so as to make sounds
louder.

9. How do we know that sound does not travel through a
vacuum?

CHAPTER XI
PRINCIPLES OF CHEMISTRY

129. Chemical Properties. — In previous chapters we
have discussed the necessity of a thorough knowledge of the
physical characteristics or properties of the various materials
used in industry. It is equally important to understand the
chemical "make up" of those materials; that is, their exact
composition. Iron and steel, for example, are used more or
less in every trade. The iron ore contains many other sub-
stances, such as carbon, silicon, phosphorus, sulphur, manga-
nese, and so on. Experience has taught the steel-maker
that it is desirable to have as little phosphorus and sulphur
as possible in the raw pig iron from which he makes his steel.
The foundry man requires pig iron without much manganese,
because this property tends to make the iron hard and
difficult to melt. Silicon in pig iron makes the carbon
assume a form called graphite carbon. This tends to weaken
the iron and steel bars, rails, sheets, etc., which are made
from the pig iron, because it forms flakes between the particles
of iron.

What has been said in regard to iron and steel, applies
equally to other materials. A knowledge of the principles
of chemistry is needed to understand the composition of
these materials, and the chemical processes that take place
when they are used in manufacture. In determining the
chemical properties of a substance it is necessary to take a
small amount of the mixture and analyze it (Fig. 66).

125

126 APPLIED SCIENCE

130. Mixtures and Compounds. — The great variety of
. solids, liquids, and gaseous substances that are used in one
form or another in every-day industrial operations may be
divided into mixtures, compounds, and elements.

Fig. 66.— Taking Test Borings of Pig Iron.
Various parts of the bar are drilled and the

borings thus obtained are mixed and analyzed.

When two or more substances are put together, the result
is called a mixture. While the mixture may differ in some
ways from each of the substances that compose it, no new
compound is formed, and the original substances may be
separated by mechanical means. We can mix substances
in any proportion. Gunpowder, for example, is a mixture of
sulphur, carbon, and saltpeter. Each one of these ingredients
may be separated from the others. Water, for example,
will separate the saltpeter.

A compound, the smallest part of which is called a molecule,
is a substance composed of two or more special substances
called elements, which are combined in definite proportions.
The new substance formed as the result is generally unlike
either of the elements which compose it. For example, by
passing an electric current through a mixture of 2 parts of

PRINCIPLES OF CHEMISTRY 127

hydrogen and 16 parts of oxygen, both of which are gases,
water, a liquid, is formed.

131. Elements. — Elements cannot be decomposed by
any known method or divided into anything simpler. The
smallest particles of elements are known as atoms. Elements
are sometimes found alone in the earth, as are pure copper
and gold, but are usually associated with other elements.
Nearly eighty elements have been discovered and named,
but many of them are not commonly found. In chemistry,
every elementary substance is represented by what is called
a symbol, which is usually a single capital letter or one capital
letter and one small letter. Symbols are used to save time
in writing and to describe briefly and clearly the composition
of a complicated compound substance.

Frequently the symbol for a substance is derived from the
first or the first and second letters of the Latin term for the
substance. For instance, Cu is the symbol for copper, and
the Latin term from which it is derived is cuprum. In like
manner, zinc, carbon, manganese, and silver are designated
by the symbols, Zn, C, Mn, and Ag. Latin has furnished
a number of the symbols for others of the common elements;
thus, the symbol for sodium is Na (natrium), for potassium,
K (kalium), and for iron, Fe (ferrum). The symbol Hg
(hydrargyrum) for mercury is from the Greek.

132. Metallic and Non-Metallic Elements. — The most
satisfactory way to classify elements is to consider them
as metals or non-metals. Non-metallic elements are those
that combine readily with metals to form compounds; for
example, chlorine, sulphur, silicon, phosphorus, etc. The
non-metallic elements have not so much trade importance

128 APPLIED SCIENCE ^

as the metals and consequently will not be considered in
detail in this book.

Metals are good 'conductors of heat, that is, warmth or
heat travels rapidly through them. About one-half of all
the known metals are very scarce, and some of them have
been seen by only a few persons. A few of the metals, like
gold, platinum, silver, copper, and bismuth are found in
a free state, that is, pure and unmixed with other materials.
The majority of the metals are found in ores combined with
oxygen or sulphur.

The art of extracting these metals from their ores and
refining them is called metallurgy. This extraction may be
accomplished in two ways: by the dry method, and by the
wet method. In the dry process, the metal is separated
from its ore by heat, and the use of high temperature in
large furnaces of different kinds is involved. This is the
process used in extracting pig iron (see page 370) from iron
ore. The wet method involves crushing or pulverizing
the ore, as in the case of copper ore, and treating it with
chemical liquids and acids, through which an electric current
is passed. This latter method is known as the electrolytic
process and involves what is termed electrolysis.

133. Atomic Weight. — Atoms are assumed to have a
definite weight. Hydrogen is the lightest element and has
therefore been selected as the unit of weight; all other ele-
ments are measured in terms of hydrogen. For example:
If equal volumes of hydrogen and oxygen are weighed,
oxygen is found to weigh sixteen times as much as hydrogen.
Hence the atomic weight of oxygen is 16.

The atomic weights of the commonest elements are given
in the following table:

PRINCIPLES OF CHEMISTRY

129

Table op Atomic Weights

ft
ft

Approximate

Element

Aluminum

Magnesium

Antimony

120

Manganese

Argon

Mercury

200.5

Arsenic

Nickel

58.5

Barium

137

Nitrogen

Bismuth

208

Oxygen

Boron

Phosphorus

Bromine

Platinum

195

Cadmium

112

Potassium

Calcium

Radium

226.5

Carbon

Silicon

Chlorine

35.5

Silver

108

Chromium

Sodium

Cobalt

Strontium

87.5

Copper

63.5

Sulphur

Fluorine

Tin

119

Gold

197

Titanium

Helium

Tungsten

Hydrogen

Uranium

Iodine

127

Vanadium

Iron

Zinc

Lead

207

134. Analysis. — If an electric current is passed through
water, made slightly acid to increase conductivity (ease of
passage), the water will be decomposed or separated into

130 APPLIED SCIENCE

its elements, oxygen and hydrogen, which can be collected
in separate tubes. Separating compounds into their elements
is called analysis.

In the case of water, for every volume of oxygen there
will be found to be just twice the volume of hydrogen.
Every molecule of water contains two atoms of hydrogen
and one atom of oxygen. The chemical formula expressing
this is H^O. In any formula the number of atoms is shown
by writing the number below the symbol of the element and
at the right.

135. Synthesis. — As already stated, when the proper
proportions by weight of oxygen and hydrogen are mixed
and a spark passed through, water is formed. This change,
often called a reaction, may be written as follows:

H 2

2 atoms of

combined

1 atom of

forms

1 molecule

hydrogen

with

oxygen

of water

Abbreviating a reaction in this manner is called writing
a chemical equation. In a very concise form it shows: on
the left-hand side of the equation the substances (called
factors) which enter the reaction, on the right-hand side
the products, and also the exact amount of each that must be
taken or formed. Once the products are determined (usu-
ally by experiments), the equation may be written and
balanced by having the same number of atoms of the elements
on each side of the equation. Forming compounds by com-
bining elements is called synthesis.

136. Molecular Weight. — The molecular weight of a
compound is the sum of all the atomic weights in the com-

PRINCIPLES OF CHEMISTRY 131

pound. To illustrate: H/) is composed of two atoms of
hydrogen and one atom of oxygen. According to the table
of atomic weights (page 129), water has a molecular weight
of 18, i.e., (1X2 (H 2 ) + 16 X 1(0) = 18). This means
that 2 parts of hydrogen combined with 16 parts of oxygen
form 18 parts by weight of water.

137. Law of Combined Weights. — When elements com-
bine to form chemical compounds, they unite according to
fixed proportions. To illustrate: When water is formed
from the combination of hydrogen and oxygen there must
be 2 parts of hydrogen to 1 part of oxygen. These gases
must unite in this proportion or water will not be formed.
Thus 2 atoms of hydrogen and 1 atom of oxygen unite
to form 1 molecule of water.

138. Valence. — If we examine a number of symbols of
binary compounds (compounds made of two elements) of
hydrogen, such as HC1, H 2 0, NH 3 , CH 4 , we find that the
first compound contains one atom, the second two atoms,
the third three atoms, and the fourth four atoms of hydrogen.
This means that the different elements are combined with
the same element (hydrogen), or other elements equivalent to
it in combining power, in different amounts as expressed by
the symbols. This power of an element to combine with
different amounts of hydrogen or its equivalent is calted a
valence. The combining power of hydrogen, which is one,
is selected as the unit.

139. Chemical Action. — Chemical change is due to the
action of chemical force, which like other forces cannot be
described; but is known by its effects. It is quite different,

132 APPLIED SCIENCE

however, from the other forces of gravitation, heat, light,
and electricity.

When two elements or compounds act chemically upon
each other (disintegrate) or are treated in some special way,
they are generally altered in appearance and state.

To illustrate: A mixture of oxygen and hydrogen is still a gas,
but a chemical compound of oxygen and hydrogen is water, or a
liquid. When zinc is added to muriatic acid ("raw acid") heat is
given off, a gas is generated, and the zinc combines with the acid.
The resulting compound, zinc chloride, is different from the original
substances. The equation is :

2HC1

ZnCl 2 + 2 H

Zinc

Hydrochloric

Zinc Hydrogei

Acid

Chloride

These illustrations show that chemical action is distinguished
from all other action: first, by producing a compound with proper-
ties entirely changed from those of the substances or compounds
originally used; second, by the fact that it takes place between
definite weights and volumes.

140. Hydrogen. — Hydrogen is a colorless, odorless gas,
burning with a pale blue flame and very little light, but with
great heat. It is chemically prepared by the action of zinc
or iron, and hydrochloric or sulphuric acid. Zinc and sul-
phuric acid form zinc sulphate and hydrogen. The reactions
may be represented by the equations:

Zn + H 2 S0 4 = ZnS0 4 + 2H

Zinc Sulphuric Zinc Hydrogen

Acid Sulphate

Fe + H 2 S0 4 = FeS0 4 + 2H

Iron Sulphuric Iron Hydrogen

Acid Sulphate

PRINCIPLES OF CHEMISTRY 133

141. Oxygen. — Oxygen exists in a free state in the
air, which is a mixture composed of 20% oxygen and 80%
nitrogen. Oxygen is a colorless, odorless gas, and may
be prepared by decomposing a compound rich in oxygen,
like KC10 3 (potassium chlorate), with heat, or it can be ex-
tracted from the air. In this latter case the gas is collected
over water.

142. Oxidation. — Oxygen unites readily with other ele-
ments, particularly metals, and forms compounds called
oxides. For example: When iron is exposed to moisture
and to the air which contains oxygen, it oxidizes and rusts.
When the oxygen combines with a carbon, as coal, it gives
off considerable heat and light. This process is called com-
bustion. A substance or element which burns is called a
combustible, and a substance or element that does not burn
is called a non-combustible. Oxygen is called a supporter
of combustion. Elements will not combine until a definite
temperature, called a kindling point, is reached.

Ozone is a form of oxygen, and is a powerful oxidizing
agent. When an electric spark passes through the air, it
changes oxygen into ozone. Three atoms of oxygen form
a molecule of ozone.

Questions

1. Why is a knowledge of the chemical "make up" of certain
substances, such as iron, important?

2. What is the difference between a mixture and a compound?

3. Name a number of mixtures; compounds.

4. Give the names of five common elements with their chemical
symbols.

5. Why is it desirable to abbreviate chemical names into
svmbols?

134 APPLIED SCIENCE

6. Why is hydrogen selected to fill balloons and some air-ships?

7. Give the characteristics of a metal.

8. What is the difference between a metallic and a non-metallic
element?

9. What is analysis? Synthesis? Metallurgy?

10. What is the symbol for water?

11. How do. we know what the definite symbol for water is?

12. What is the value of a chemical equation?

13. What is the valence of an element?

14. What is chemical action?

16. What is the difference between physical action and chemi-
cal action?

16. What is the molecular weight of hydrochloric acid?

17. Write the equation for "killing" (neutralizing) muriatic
(hydrochloric acid) and zinc.

18. How much zinc chloride will be formed from 4 oz. of zinc?

19. Describe the properties of oxygen; hydrogen.

CHAPTER XII
ACIDS, ALKALIES, AND SALTS

143. Classes of Compounds. — Compounds may be di-
vided roughly into four classes of substances: water, acids,
bases or alkalies, and salts.

144. Properties of Water. — Pure water is the commonest
compound that exists. The water we use comes to us either
in the form of rain or of melted snow from the mountains.
Part of it trickles or percolates through the ground and
dissolves any soluble material or gases with which it comes
in contact. When the water has passed into the ground and
comes in contact with limestone and magnesium compounds,
some of the substances are dissolved and the water becomes
hard. This kind of water appears when an artesian well is
drilled. Water that flows over the surface of the earth
contains suspended matter or dirt and is generally called
soft water.

Thus the distinction between hard and soft water depends
upon the substances which they carry, and especially upon
their chemical action. In soft water, soap readily lathers
and the suds thus formed exert a rapid cleansing action. In
hard water, soap lathers only with difficulty and often will
not lather satisfactorily at all, because of the formation of
lime soap, which is insoluble.

If hard water is boiled the hardness often disappears, and
soap then acts as in soft water, but in some cases boiling

13$

136 APPLIED SCIENCE

has no effect. Such a condition is wholly due to the action
of the dissolved solids upon the soap. Hard water contains
either magnesium or calcium sulphates or carbonates. If
carbonates only are present in the water, it is likely to become
soft when it is boiled, for boiling drives out carbonic acid gas
(C0 2 ) which holds the carbonates in solution.

Thus we see that water may differ in its properties accord-
ing to the influence of substances to which it has been ex-
posed. Rain and snow water are difficult to obtain; river
water may be muddy, more especially in stormy weather;
artesian well water will contain in solution the minerals with
which it has come in contact. The source of the purest
water is a location near a mountain, or in a mountainous
country. There the upland surface water has not yet come
in contact with impurities, and has had little opportunity
to dissolve lime or magnesia compounds.

145. Importance of Acids and Alkalies. — In addition to
water, the most important compounds or substances used
in chemical changes are acids and alkalies. They may be
called the fundamental chemical agents that produce chemi-
cal changes. It is important to know their properties.

146. Nature of Acids. — An acid is a compound of hydro-
gen with a non-metallic element or a group of elements that
act as one, called a radical. The acid may be a gas soluble
in water, as muriatic acid, or a liquid, such as sulphuric acid,
or a solid, such as oxalic acid. All acids have a sharp, sour
taste and most of them act on metals. The test used for
determining whether or not a solution is an acid is to place
a drop of the solution on a piece of blue litmus paper (paper
dyed blue with the juice of a small plant). If the blue color

ACIDS, ALKALIES, AND SALTS 137

changes to red, the solution is an acid. If the paper remains
blue, the solution is not acid. Acids have different powers
and uses. While some are health-
ful and are used for foods, others
are poisonous. Acids are used
very commonly in industry for
dissolving metals (Fig. 67).

147. Mineral and Organic
Acids.— There are two kinds of
acids — organic and mineral. Or-
ganic acids are those, such as car-
bolic acid, oxalic acid, etc., which
contain the element carbon in
their composition. Mineral acids
are those composed of any of the
other elements, suchas hydrochloric

acid.nitric acid, a„d» U lph U ric acid, T '%«Jf?% 'ft^S.
and are used principally in the iron is carefully weighed
, , j - . . ■ and then dissolved in acid

trades and industries. over a } &mp _

Nitric acid is largely used in the
manufacture of explosives, and hydrochloric acid as a "pick-
ling" liquor for cleaning metals. When nitric acid is added
to some' metals, it acts very quickly, and gives off reddish
brown fumes that are suffocating in their effect.

The change that takes place is represented by the following
equation :

3 Cu + 8 HNO a = 3 Cu (NOj), + 4 H,0 + 2 NO

Copper Nitric Copper Water Nitric

Acid Nitrate Oxide

The copper nitrate and water remain and the gas (nitric oxide)

138 APPLIED SCIENCE

passes off. Ordinary commercial nitric acid has a specific gravity
of 1.42 and contains about 68% of acid.

Sulphuric acid, often called oil of vitriol, is the most im-
portant chemical used in manufacturing operations. Its
symbol is H 2 S0 4 and in a diluted or weak form it acts on
metals. When concentrated or strong it forms on the metal
a coating of a salt which prevents further action.

The action of the acid on a metal may be represented by the
following equation:

H a S0 4

= FeS0 4

+ H 2

Iron

Sulphuric
Acid

Iron
Sulphate

Hydrogen

Muriatic," or hydrochloric, acid is generally made by the
action of sulphuric acid on salt.

The action may be represented by the following equation:

2 NaCl +

H 2 S0 4 =

= NaaSO, + 2HC1

Common Salt

Sulphuric

Sodium Hydrochloric

Sodium Chloride

Acid

Sulphate Acid

148. Formation of Salts. — A salt is a compound of metal-
lic and non-metallic elements or radicals. It is formed by the
action of: (1) an acid on an alkali or base (a base is a compound
of a positive, i.e., a metallic element, or a group of them
called a radical, and OH, the hydroxyl group); (2) an acid
and a metal; (3) an acid and a salt.

In forming a salt, the hydrogen of the acid is replaced
by the metal or metallic radical. If there is an excess of
acid — that is, if the base is only sufficient to combine with

ACIDS, ALKALIES, AND SALTS 139

part of the hydrogen — only part of the hydrogen is replaced
by the metal.

To illustrate: When sulphuric acid and sodium hydrate (NaOH)
are mixed, the first action is as follows:

H 2 S0 4

NaOH

= HNaS0 4 +

H 2

Sulphuric

Sodium

Acid Sodium

Water

Acid

Hydrate

Sulphate

The second step in the change is:

HNaS0 4 + NaOH = Na 2 S0 4 + H 2

If excess sulphuric acid is used, NaOH may be formed immediately.
The salt formed at first is called an acid salt. If all the hydrogen
were replaced it would be called a normal salt. Normal salts have
no effect on blue or red litmus paper.

One of the principal sodium salts is sodium carbonate,
often caned soda ash, and is represented by the formula
Na 2 C0 3 .

Soda crystals, or sal soda, are made by dissolving soda ash in
hot water, and allowing the clear liquid to cool. Crystals then form,
having the composition of Na 2 CO 3 .10H 2 0. Soda crystals contain
over 60% of water, do not dissolve as readily as does soda ash, and
are, therefore, not economical to buy.

149. The Formation of Alkalies. — Alkali is the commer-
cial arid industrial name for a strong base, such as caustic soda
(NaOH), caustic potash (KOH), and ammonium hydroxide
(NH 4 OH). An alkali is opposite to an acid in character
and turns red litmus paper blue. When a limited amount
of acid is added to an excess of alkali, only part of the OH
(hydroxide radical) is replaced by a negative element or
radical, and a basic salt is formed.

140 APPLIED SCIENCE

To illustrate: If excess iron (ferric) hydroxide and a limited
amount of hydrochloric acid are mixed the result is:

Fe (OH) 3 -f HC1 = FeCl (OH) 2 +H,0
or

/OH /CI

Fe— OH f HC1 = Fe— OH -:- II 2

\OH \OH

Ferric Hydrochloric Basic Water

Hydroxide Acid Ferric

Chloride

The most important of the alkalies iu caustic soda which
is made from soda ash bj r adding milk of lime (calcium
hydroxide) to the solution.

Na 2 C0 3

Ca(OH) 2

CaC0 3 +

2NaOH

Soda Ash

Milk of

Calcium

Caustic

Lime

Carbonate

Soda

The calcium carbonate separates as a sediment.

150. Nomenclature of Acids, Salts, and Bases. — Acids
usually have two names, the chemical and the common.
The chemical names are given according to certain rules
based upon the elements in the acid. The common name
of the acid is the commercial name.

Binary acids which are compounds of hydrogen and a non-
metallic element, are named hydro-ic acids. Thus, hydro-
chloric acid is HC1 and hydrobromic acid is HBr.

When there are three or four acids formed of the same
elements, oxygen is one of the elements and is the only
element varying in amount, as in: HN0 3 , HN0 2 , HNO;
and HCIO, HC10 2 , HC10 3 , HC10 4 .

The one with the most oxygen is called perchloric acid
HC10 4 , "per" meaning "above." The most common

ACIDS, ALKALIES, AND SALTS 141

of the above acids is HC10 3 , chloric acid. HC10 2 is called
chlorous acid, and HCIO hypochlorous acid, "hypo" mean-
ing " under " or " lesser. " When there ar« two salts composed
of the same elements, the one with the smaller proportion
of the non-metallic element usually ends in ouu. The one
with the larger proportion ends in zc. To illustrate: CuCl 2
is cupric chloride, and CuCl is cuprous chloride. FeCl 2 is
ferrous chloride, and FeCl 3 is ferric chloride. The ending
of a binary salt is always ide.

, Salts with more than two elements or radicals are called
tertiary compounds. When there are more than two salts,
the ending ic acid is changed to ate, for example, per-ic acid
is changed to per-ate; the ending ous acid is changed to ite,
for example, hypo-ous acid to hypo-itc.

, 151. Compounds of Metals. — When combined with other
elements, metals form compounds named generally after
the element with which they are united. Thus, compounds
with chlorine are called chlorides; with bromine, bromides;
and iodine, iodides.

* The most common compounds of metals are given in the
following tabic.

Compounds With

Oxygen form oxides.

Oxygen and hydrogen form hydroxides.

Sulphur form sulphides.

Sulphur and hydrogen form hydrosulphides.

Nitric acid form nitrates.

Nitrous acid form nitrites.

Acids of chlorine and oxygen form chlorates.

Sulphuric acid form sulphates.

Sulphurous acid form sulphites.

142 APPLIED SCIENCE

Carbonic acid form carbonates.
Phosphoric acid form phosphates.
Arsenical agid form arsenates.
Silicic acid form silicates.
Boric acid form borates.

Many of the compounds are found in nature; thus sul-
phate of calcium (CaS0 4 ) is a very common salt called
gypsum; oxide of iron, made up of iron and oxygen, is called
iron ore; and carbonate of iron (FeC0 3 ) is another form of
iron ore.

Questions

1. What are some of the common properties of an acid?

2. Name the mineral acids.

v 3. Name some organic acids.

4. What is the composition of the so-called " pickling" solution
used in trades? "
- 5. Write the action of copper and nitric acid.

6. Write the action of zinc and sulphuric acid.

7. Explain the difference in the products formed from nitric
acid and a metal, and sulphuric or hydrochloric acid and a metal.

t 8. Give the symbol cf oil of vitriol.
' 9. What is the composition cf a salt?

10. How are salts formed?

11. Give the composition of any salt.

12. What is a base? An alkali?

13. Why are there two names to the common acids and alkalies?

14. Give the chemical names cf the following symbols: HBr0 3 ;
HC10 4 ; NaCl; HN0 3 ; HC10; K 2 S0 4 ; CuCl 2 ; FeCl 3 ; N aa S0 4 .

15. The antidote or substance recommended to be taken in
case of poison from ammonia is lemon juice in water. Explain
the action.

16. Explain the difference between "hard" water and "soft"
water.

CHAPTER XIII
PHYSICO-CHEMICAL PROCESSES

152. Nature of Physico-Chemical Processes. — Certain
processes like:

1. Solution 6. Filtration

2. Ebullition 7. Crystallization

3. Evaporation 8. Sublimation

4. Precipitation 9. Distillation

5. Clarification

are physical in character, though used extensively in combina-
tion with certain chemical processes. They must be con-
sidered, therefore, in discussing the principles of chemistry.

153. Solution. — When a solid substance is placed in a
liquid and dissolves without a change in its chemical struc-
ture, the resulting liquid is said to be a solution of the dis-
solved substance. The liquid used is called the solvent of
the substance. As an illustration: Sugar dissolved in water
forms a solution of sugar. When the water will dissolve no
more sugar, it is said to be a saturated solution at that
temperature. A liquid saturated with one substance may
still be a solvent for another substance.

164. Ebullition. — Ebullition or boiling is the violent agi-
tation produced in a liquid when it is heated from a liquid
to a gaseous condition. The heat acts first oh that portion

143

144 APPLIED SCIENCE

of the liquid resting against the heated surface, and converts
a part of it into steam, which rises in the form of bubbles
that break on the surface of the liquid. The temperature at
which a liquid boils is called its boiling point. Each liquid
has its specific boiling point as well as its specific weight at
a specific atmospheric pressure. The boiling point remains
constant during ebullition.

165. Evaporation. — Evaporation is the process by which
a liquid is gradually changed into vapor which fumes into
the air. Evaporation may take place at any temperature,
but only on the surface of the liquid; thus it differs from
boiling which goes on inside the liquid. Since liquids
evaporate more or less at all temperatures, there is no specific
evaporating point, as there is a specific boiling point.

166. Precipitation. — Precipitation is the process of sepa-
rating solid particles from a solution by the action of either
heat, light, or chemical substances. The solid particles
separated are called the precipitate, and the liquid remaining
the supernatant liquid. A precipitate may either fall to the
bottom or rise to the top of the supernatant liquid. Pre-
cipitation caused by the action of heat is illustrated by the
coagulation and precipitation of albumin, when albuminous
fluids, such as the white of egg, are heated; precipitation of
silver salts by light as in photography illustrates precipita-
tion by light; and precipitation by chemical reaction occurs
in many instances when salts are mixed in solution.

The objects of precipitation are: (1) to convert solid
substances into the form of powder; (2) to purify liquids;
(3) to test chemicals; and (4) to separate chemical substances.

There is a distinct difference between a sediment and a

PHYSICO-CHEMICAL PROCESSES 145

precipitate; a sediment is a solid matter separated merely
by the action of gravity from a liquid in Which it has been
suspended. A precipitate, on the other hand, is a solid
matter separated from a solution by chemical means.

167. Clarification. — Clarification is the process of sepa-
rating from liquids, without making use of strainers or filters,
solid substances which interfere with transparency. The
principal methods of clarification are: (1) by the applica-
tion of heat; and (2) through the use of gelatin and other
substances. Boiling facilitates the separation, since the
minute bubbles of steam adhere to the particles and rise
with them to form scum, which may be skimmed off. This
process takes place when milk is heated and the albumin
rises to the top. If albumin be added and heat applied to a
turbid ("milky") liquid, the albumin will, on coagulating,
envelop the particles and rise to the top with them. Acids
may be used to precipitate the casein (white curd) of milk,
and the precipitated casein will carry with it the insoluble
particles. If a cloudy liquid be agitated with paper pulp
and then allowed to stand, it will gradually become clear.

168. Filtration. — The commonest method of separating
solids suspended in a liquid is by filtration, i.e., by passing
the liquid through the pores of some substance called a filter.
The liquor that passes through is called a filtrate, and the
material that remains, the residue. Various kinds of mate-
rial, such as, paper, cloth, cotton, wool, asbestos, slag, sand,
and other porous substances, are used as filters. Cotton cloth
is often used by fastening it onto a wooden frame in such a
way that a shallow bag is formed into which the liquid to
be filtered is poured. The first portion of the filtrate that
comes through is cloudy, but the rest soon becomes clear,

146 APPLIED SCIENCE

and then the first portion may be returned to the filter.
Filtration cannot be hastened by scraping or stirring the
precipitate on the cloth, as this action will merely cause the
filtrate to run turbid.

169. Processes of Purification. — When new compounds
are manufactured by means of chemical reaction, they are
seldom pure. In order to purify the product one or more
of the three processes of crystallization, sublimation, and
distillation are used.

160. Crystallization. — The crude product obtained
directly from a chemical reaction is usually amorphous
(not crystalline). To obtain the substance in uniform,
well-defined crystals and to separate it from impurities it
must be dissolved again with the aid of heat, filtered, and
allowed to cool slowly. Then the dissolved substances will
separate into large crystals or into very fine crystals termed
"crystal meal," according to conditions. Since the large
crystals are compact and offer a relatively small surface
to the action of water, they dissolve slowly. Crystal meal,
on the other hand, dissolves quite readily and is therefore
more commonly used.

The theory of crystallization is based on the fact that
every liquid has the power of dissolving substances. This
power can usually be increased by raising the temperature
of the liquid. There are a few substances, however, whose
maximum strength of dissolving is reached at a temperature
much lower than the boiling point. When a solution has
dissolved all the solid that it can take up, it is said to be
saturated; any decrease in the temperature will then result
in the separation of a part from the main body of the sub-
stance — usually as crystals. While crystals are being formed,

PHYSICO-CHEMICAL PROCESSES 147

there is a tendency to exclude from the solution all matter
not homogeneous with it, that is, all matter not of the same
kind. If a concentrated solution which is impure is allowed
to crystallize, the impurities may become enclosed or en-
tangled among the forming crystals. This is undesirable
and can be prevented by stirring the solution while crystal-
lization is taking place. Thus the formation of the very
fine crystals, called "crystal meal," is caused. These fine
crystals may be washed free from the "mother liquor"
(the liquor from which the impurities are obtained), and may
be cleansed of all impurities.

161. Water of Crystallization. — A great many compounds
crystallize very easily, and are sold in a crystallized form.
In crystallizing they take up more or less water from the
solutions and this water forms a definite part of the com-
pound. For example, blue vitriol is crystalline copper sul-
phate. Its symbol, CuS0 4 .5H 2 0, means that crystalline
copper sulphate contains 5 molecules of water. Merchants,
in purchasing chemicals, desire them in the crystalline form
as this form is considered the purest. Oftentimes compounds
are sold on the basis of their dry weight, i.e., the weight of
the substance minus the weight of the water.

The method of figuring the dry weight is as follows:
Assume that 34 lbs. of copper sulphate lose 7 lbs. on heating.
What is the per cent of water of crystallization?

7 lbs. = amount lost
34 lbs. = whole amount
g \ or .205 of the whole was lost

As it is customary to express the loss in per cent, the loss is:

.205 X 100 = 20.5%

148 APPLIED SCIENCE

162. Sublimation. — Most solid substances melt when
a certain amount of heat is applied to them. Upon being
heated further they vaporize. There are a few substances,
like ammonium chloride, which vaporize without melting.
To purify such substances, they must first be heated and
their vapors collected. This process of purification is called
sublimation.

163. Distillation. — Distillation is the process by which
a liquid is boiled and its vapor condensed. It is used, like
the processes of crystallization and sublimation, for purposes
of purification. If impure water, for instance, is placed in
a boiler to which a condensing apparatus (an apparatus for
cooling the steam) is attached, the vapor or steam given off
when the water is boiled, is condensed. It then becomes
pure or distilled water, all the non-volatile impurities having
been left in the boiler. The water has a lower boiling point
than the impurities, hence it boils first, and is thus enabled
to leave the impurities behind.

164. Chemical Properties of Coal. — The principal ma-
terials used for fuel are petroleum and coal. Ordinary hard
coal is called anthracite coal, and the soft, lumpy kind that
crumbles very easily is called bituminous coal. All fuels
are composed of carbon, or compounds of carbon and hydro-
gen, called hydrocarbons, combined with such impurities
as ash, sulphur, nitrogen, etc.

When fuel burns the chemical change which takes place
is that the oxygen of the air combines with the hydrogen
and carbon. The manner in which coal burns depends upon
its composition, the nature of the fire, and the air supply.

If the draught of air is insufficient, the gases are only partly

PHYSICO-CHEMICAL PROCESSES 149

consumed. The oxygen then unites with the hydrogen
and leaves the carbon in fine particles of soot or smoke,
which float away with the draught or are deposited upon the
surface of the boiler. Moreover, when the air is not suffi-
ciently hot, partial combustion again results, changes the
hydrogen to water*vapor, and sets the carbon free as soot or
smoke. If the gases become chilled, and pass off as a whole
unburned, they thus carry away, not only their own heat
of combustion, but also the heat which has been absorbed
for their liberation. Smoke is therefore the sign of the
imperfect combustion of hydrocarbons.

165. Chemical Bacteria. — Animal grease is not suitable
as a lubricant because it soon becomes "rancid," that is,
it gives off a disagreeable odor and forms acids. Careful
experiments show also that the changes which take place
in grease and other organic substances when exposed to
warm, moist air are caused by small living plants or organ-
isms. When these minute organisms alight upon certain
vegetable and animal substances, they grow vigorously,
and live on the material. As the result of their action, a
chemical change takes place. In the case of starch or sugar
this change is called fermentation; in the case of fat, ran-
cidity; and in the case of proteids (compounds of nitrogen,
carbon, oxygen, and hydrogen), putrefaction. These living
organisms are called microbes, germs, and bacteria.

All the changes that take place in milk, such as souring,
becoming tainted, etc., are due to bacteria. Cream, as it
is obtained from milk, contains bacteria in large quantities,
and as these organisms grow they produce the ripening effect
which gives flavor to the butter. Certain species of bacteria
carry disease and produce undesirable effects upon the

150 APPLIED SCIENCE

flavor of the cream and butter. To counteract such harmful
changes, growths of special protective bacteria called cul-
tures are introduced into the butter for the purpose of pre-
serving its flavor. Some bacteria are very harmful as they
produce disease in both the human body and in other sub-
stances, but others are extremely useful in industry, as they
produce desirable chemical changes and assist in converting
raw materials into finished products. Such a beneficial
change is produced by bacteria in the case of tanning.

166. Composition of the Earth. — Most of the raw mate-
rials used in trade and industry have their source in the
earth. A few of these substances, such as gold, are found
in a free state, but as noted before, the more common sub-
stances, such as iron, lead, tin, zinc, etc., are found combined
with oxygen, sulphur, and dirt. To understand why these
are found in this state, it is necessary to study the condition
of the earth.

The interior of the earth is a hot, molten mass, from which
constantly issues, on various parts of the earth, a stream of
hot, molten stone or hot steam, gases, and so on. The gases
are steam, carbonic acid, burning carbon, hydrogen, and
hydrogen sulphide. The surface of the earth is in a com-
paratively cold condition. As we dig below the surface we
find masses of stone and rock within which valuable metallic
particles are embedded. These particles are called minerals.
These combinations of mineral and rock are due to the mix-
ing of hot masses. As a result, the metals that are acted
upon by oxygen, acids (carbonic acid), hydrogen sulphide,
etc., are found in the earth as oxides, sulphides, carbonates,
etc. As gold is not acted upon by any of the ordinary gases
it is found in a free state.

PHYSICO-CHEMICAL PROCESSES 151

The earth appears to be composed of twelve main elements:
oxygen, silicon, aluminum, calcium, magnesium, potassium,
sodium, carbon, hydrogen, sulphur, chlorine, and iron. Of
course many other elements, such as the precious metals,
are present but are found in small quantities only. Most
of the rocks found in the earth are mixtures of two or more
minerals. Granite formed from volcanic eruption, for ex-
ample, is a mixture of three minerals — feldspar, quartz,
and mica; sandstone consists of particles of silica or sand;
limestone consists of a carbonate of lime; slates consist
of silicates of aluminum; and clay consists principally of
aluminum compounds. The minerals are held together in
the stone by some binding substance, like carbonate of lime,
iron oxide, or silica. The color of the clay, rocks, and differ-
ent parts of the earth is due to the presence of small quanti-
ties of iron and other metals. Changes in temperature cause
the rocks to expand and contract and consequently they
gradually split and crack. The rain then washes into the
valley the loose parts of the rocks. Thus the soft, loose soil
found on the surface of the earth is the result of the breaking
up of the rocks in this way, and the process by which such
soil is made is termed weathering or erosion.

Stones or rocks are designated as sedimentary, igneous,
or metamorphic, the classification depending upon their
origin.

Sedimentary rocks are remains of older rocks which have
been deposited under water, layer by layer. Limestone
and sandstone are examples of this class. Igneous rocks
are formed by the solidifying in a crystalline state of lava
from a volcano. Granite and allied stones are examples of
this kind of rock. Metamorphic rocks are rocks that have,
after formation, changed their original forms because of

152 APPLIED SCIENCE

the movement or pressure of the earth. Slates and marbles
are examples of this class.

167. Object of Lubrication. — Lubrication is the applica-
tion or introduction of some substance that will cling to or
flow between two surfaces and thus prevent friction. Bear-
ings and joints of engines and machinery are lubricated to
keep the various metal surfaces from coming in direct contact,
and thus to prevent excessive friction and consequent heat-
ing. (See Fig. 34, page 49.) Perfect lubrication is secured
when the surfaces are separated by means of the thinnest
possible film that is sufficient to prevent heating. A thick
film is harmful because it tends to produce fluid friction.

168. Kinds of Lubricants — Oils. — Lubricants may be
divided into three general kinds or classes — fluid, plastic,
and solid. To the first-named class belong the various oils;
to the second, the greases; and to the third, such substances
as graphite, talc, soapstone, or mica.

Where the speed of a machine is high and the pressure great,
oils are, in nearly all cases, the most satisfactory lubricants
to use. They cling to the contact surfaces and thus form
an elastic coating to the mefals and keep them apart. Oils
also absorb the frictional heat and carry it away. Other
advantages of oils are: (1) they can be obtained in almost
any desired grade or density, from the thin oils to the heavy,
dense oils; (2) they do not become rancid or gummy; and
(3) they contain no free acids.

169. Greases. — Greases are suitable for use on slow-
moving machinery where the pressure is not great. Even
where the speed is comparatively high, but the pressure is
light, a grease will often give excellent results, if the proper

PHYSICO-CHEMICAL PROCESSES 153

grade or consistency be selected. As a usual thing, However,
if grease is used indiscriminately on a large scale, especially
on textile machinery, a noticeable increase in the friction
load results.

Greases may be divided into two classes, the lime and
potash soaps, or high melting-point greases; and the tallow
base, or low melting-point greases. The first are made by
changing a small amount of fatty oil into a soap by means
of lime water, caustic potash, or other alkali, and mixing it
with a large amount of petroleum oil, such as engine oil.
Such greases have a melting point of 140° to 180° F. The
tallow base greases are composed of a large percentage of tal-
low combined with an alkali, and are brought to the desired
density by means of vaseline, petroleum, or petroleum oils.
Such greases, owing to their large content of tallow, have a
low melting point, usually about 116° to 120° F.

The high melting-point greases usually require forcing
down between the journal surfaces by means of compression
grease cups. The low melting-point greases can often be
packed in the journal box or directly on the bearings, as a
low frictional heat causes them to melt, change to an oil,
and lubricate the bearings.

170. Solid Lubricants. — The solid lubricants, such as
graphite, soapstone, etc., usually have but a limited field of
use. A certain form of graphite lately introduced, however,
has been shown in experimental laboratory tests, to have
great lubricating value with a low coefficient of friction.
The great value of this new form of graphite is due to the
fact that crystals of graphite appear as minute scales or
plates, which present a very good sliding surface and thus
serve a§ a lubricant,

154 APPLIED SCIENCE

171. Requirements of a Good Lubricant. — The selection
of the proper lubricant in any particular case depends, of
course, upon the class of machinery in which it is to be used.
If on light-running and high-speed machinery, such as is
used in the spinning, twisting, and other departments of
textile mills, the light-bodied or more fluid oils give the best
results. For slow-speed machinery, the heavier bodied oils
are best. For use on slow-speed engines, where the oil is
fed from cups, a heavy-bodied oil should be used. For high-
speed work and engines where continuous oiling systems are
used, a light-bodied oil is preferable. Cylinder oils have
for their base what is known in the oil trade as cylinder
stock, of which there are two classes — the light-colored or
filtered stock, and the dark or steam-refined stock, the latter
being almost universally used.

For steam turbine lubrication, a high-grade, pure mineral
oil is best, as the oil is subjected to high pressure and constant
churning, and consequently must be of good quality.

For gas cylinder lubrication, a pure mineral oil ranging
in body from light to heavy is found most satisfactory. This
type of oil burns freely without leaving a carbon ash.

Questions

1. What is a solution?

2. Will a cold solution dissolve more of a substance than a
hot solution?

3. What is a solvent? Name two or three common solvents.

4. What is a saturated solution? How are you able to tell if
a solution is saturated or not?

5. What is ebullition?

6. What is precipitation? Has it any industrial importance?

7. Explain the difference between a sediment and u precipitate?

8. What is clarification?

PHYSICO-CHEMICAL PROCESSES 155

9. What is filtration? Has it any industrial importance?

10. Name the three methods by which substances are purified.

11. Explain crystallization.

12. Explain how large crystals may be obtained; "mealy"
crystals.

13. What is the meaning of the term "water of 'crystallization"?

14. Give the percentage of water of crystallization in "washing
soda," Na i CO 3 .10H 2 O. (Refer to table of atomic weights in
Chapter XL)

15. What is the meaning of sublimation?

16. What are the two kinds of coal?

17. Explain the meaning of rancidity; putrefaction; fermen-
tation.

18. What are germs?

19. Explain why metals are sometimes found as oxides; sul-
phides.

20. What is the difference between granite, sandstone, and
marble?

21. Name the different classes of lubricants. State the advan-
tages and disadvantages of each class.

22. Explain the difference between crystalline and amorphous.

CHAPTER XIV

THE CHEMISTRY OF COMMON INDUSTRIAL

SUBSTANCES

172. Chemistry in Industry. — There are certain chemical
changes, such as the burning of forms of carbon, explosions,
etc., that are very common in industrial life. Moreover, the
chemical composition of certain building materials, such as
concrete, is so important to industry that everyone should
understand the fundamental principles underlying their
manufacture.

173. Forms of Carbon. — When an element is found in
several forms which have essentially different properties,
it is said to be allotropic in character. Carbon is such an
element, the different forms or modifications of which are
the diamond, graphite, and pure amorphous carbon.

The diamond is pure, crystalline carbon. It has a specific
gravity of 3.5 and is one of the hardest substances known.
On account of its hardness it is used to cut glass. The black,
impure variety, called carbonado, is set into the end of a
drill, called a diamond drill, which is used for boring holes
in hard substances.

Graphite is a soft, lead-colored, shiny solid often called
"black lead" or plumbago because it was originally sup-
posed to contain lead. It is smooth and greasy to the touch
and is used in the form of flakes as a lubricant because it

156

CHEMISTRY OF INDUSTRIAL SUBSTANCES 157

does not become decomposed, as do oils, by high tempera-
tures' and the heat of friction. Since graphite is soft, it
readily wears away and when drawn across a piece of paper
the friction causes it to pulverize and leave a mark on the
paper. Hence its use in pencils. In addition, graphite
serves as the basic substance in the making of stove polish
and as an ingredient in the manufacture of certain crucibles
in which metals are to be heated and melted.

Amorphous or noncrystalline carbon includes a number
of varieties of coal, charcoal, lampblack, coke, and gas
carbon.

Charcoal is a black, brittle solid and is obtained by heat-
ing wood in a closed pile without much access to air. The
heat drives out the liquids and gases. These are collected
as a by-product and distilled into wood alcohol, acetic acid,
etc. Charcoal resists the action of moisture, heat, and air,
and consequently telegraph and other poles are often charred
before being put into the ground. It is also used as a disin-
fectant, because it absorbs gases. Gunpowder has a basis
of charcoal. The charring of bones and animal refuse gives
a form of charcoal called animal charcoal or bone-black,
which is used in making pigments.

174. Oxides of Carbon. — When any form of carbon or
carbonaceous matter burns, it forms a gas called carbon
dioxide. If there is insufficient air or oxygen and considera-
ble heat, a lower form of the oxide, called carbon monoxide,
is the result of the chemical change. Carbon dioxide has a
slight taste, but no odor and will not burn. Hence it is used
as a fire extinguisher. Carbon monoxide is a very poisonous
gas. It is a constituent of illuminating gas and burns with
a blue flame.

158 APPLIED SCIENCE

176. Hydrocarbons. — The many compounds of carbon
and hydrogen are called hydrocarbons. Carbon unites with
elements, particularly metals, to form carbides, such as cal-
cium carbide and silicon carbide. Calcium carbide is made
by heating lime and coke or coal in an electric furnace. It
is a brittle, dark gray, crystalline solid which forms acety-
lene gas on the addition of water.

CaC 2 + 2H 2 = C 2 H 2 + Ca(0H) 2

Calcium Water Acetylene Calcium

Carbide Hydroxide

176. Flame. — When gases are burned a light is given off.
This light is called a flame. Flame is due to the combina-
tion of a gas with the oxygen of the air. A flame may be
luminous, as in the case of an ordinary gas light, or it may
be non-luminous, as in the case of the blue flame of a gas-
burner. The luminosity of a flame is due to the glowing
of small particles of carbon. A yellow flame is caused by
incomplete combustion.

177. Compounds of Carbons. — The following are the
names, symbols, and uses of some of the most important
classes of carbon compounds :

Class
of Compounds Composition Use

Carbohydrates Compound of carbon, hydro- Sugars

gen, and oxygen, the last Starches

two in the proportion to Cellulose
form water.

Alcohols Compound of carbon and hy- Wood alcohol

drogen with an OH group. Grain alcohol
C,H s .OH, ordinary spir-
its of alcohol,

CHEMISTRY OF INDUSTRIAL SUBSTANCES 150

Class

of Compounds

Composition

Use

Fats

Salts of certain organic acids

To make soaps,

called fatty acids.

lubricants.

Oils

Liquid fats

Soaps

When fats are boiled with

Washing pur-

sodium hydroxide or al-

poses. Gly-

kali, a soap and glycerin

cerin used

are formed.

to make
smokeless
powder.

178. Gunpowder, — Ordinary gunpowder is a mixture of
charcoal, sulphur, and potassium nitrate. The efficiency
of gunpowder depends upon the formation of a large volume
of hot gases in a closed space. The pressure exerted by these
gases propels the bullets, breaks the stones, etc. If gun-
powder is wet, the potassium nitrate dissolves and the
powder loses its effectiveness.

179. Sand. — Sand is composed of silicon dioxide (sym-
bol Si0 2 ). On account of their hardness, some varieties
of sand and mixtures are used for grindstones.

180. Glass. — When sand and several other substances
are mixed and heated, the fused mixture forms glass. The
coloring of glass is caused by the introduction of oxides of
metals into the heated mass.

181. Clay. — Clay is an impure form of aluminum silicate.
Clay is formed by the slow "breaking up" or decomposi-
tion of certain parts of rocks called the feldspars (silicates of
aluminum, sodium, or potassium). The decomposition

160 APPLIED SCIENCE

causes the feldspar to form an insoluble silicate and a soluble
silicate (sodium or potassium silicate). The soluble part
is washed away and the insoluble portion which remains —
particles of mica, quartz, carbonate of lime and magnesium,
and iron — is called clay. The greater part of the clay is pure
aluminum silicate (H 4 Al 2 Si 2 9 ).

182. Properties of Clay. — The principal property of
kaolin, or clay, is that it becomes slightly soft (plastic) when
wet and may be molded into various shapes. When clay
is heated it shrinks and in cooling becomes very hard.
The color of clay, which is due to the presence of iron and
other impurities, varies from gray to red.

183. Porcelain. — Porcelain is a glazed material used for
insulators, etc. It is made by mixing kaolin, fine sand, and
powdered feldspar, shaping the mass, and then heating it
to a high temperature. The surface is glazed by being coated
with a mixture of salt and heated. The heat causes the glaze
to melt and penetrate the surface.

184. Earthenware. — Impure plaster clay, when wet,
shaped, and heated to a moderate temperature may be used
for tiles, etc.

186. Bricks. — Many materials used in building construc-
tion, such as bricks, drain pipes, etc., are made from impure
clay by wetting, molding, and then heating the mixture
sufficiently to harden it. The red color in bricks is due to
the iron oxide in the compounds of the clay.

186. Mortar. — To make mortar a thick paste is formed
by mixing lime, sand, and water. This paste is placed

CHEMISTRY OF INDUSTRIAL SUBSTANCES 161

between bricks or stones and slowly hardens or "sets" by
losing water and absorbing carbon dioxide. The object of
the process is to make the mortar porous and to facilitate
the change of the hydroxide into the carbonate.

187. Cement. — Cement is either a natural or artificial
mixture of limestone, clay, sand, and iron oxide. Limestone
is an impure form of calcium carbonate mixed with silica
(sand) and clay. When the limestone contains about 10%
silica and clay it has the desired proportion to form a good
mixture that hardens under water, as well as when exposed
to the air. It is then good material for making cement and
is called hydraulic lime. Portland cement is made by heat-
ing the powdered combination into a clinkered mass and
then grinding it. A mixture of cement, sand, water, and
crushed stone is called concrete.

188. Bleaching. — A better appearance may be given to
cotton and many other fabrics by passing them through
bleaching solutions. The most effective bleaching agent is
bleaching powder, a white powder made by passing chlorine
gas (made by heating common salt and sulphuric acid) into
oxide of lime (CaO). Other bleaching agents, such as
sodium sulphite (Na^SC^) and sodium peroxide (Na^C^),
are sometimes used. The lime in the bleaching powder holds
the chlorine gas. The cloth to be bleached is placed in a
mixture of bleaching powder and water. The chlorine gas
from the bleaching powder acts on the water forming hydro-
chloric acid and oxygen. The oxygen combines with the
coloring matter and destroys it, thus leaving a white-surfaced
fabric. Bleaching is a distinct chemical action and may
weaken the fabric.

162 APPLIED SCIENCE

189. Dyeing and Dyestuffs. — The process by which color-
ing is added to fabrics by means of dyestuffs is called dyeing.
Dyeing may be done in one of three ways: (1) by immersing
loose raw material, such as unspun cotton threads, in the
coloring solution; (2) by immersing yarn before it is woven;
and (3) by immersing the woven cloth itself. The latter
method is the cheapest and the one most commonly used.

Dyestuffs are obtained from animals, vegetable substances, .
minerals, and organic materials. Examples of the dyes *
obtained from these four classes of materials are furnished
by cochineal coloring matter, indigo, Prussian blue, and
aniline dyes respectively.

Fibers of animal origin, such as silk or wool, can be dyed
by simply immersing them in the color solution, but materials
such as linen and cotton, which have a vegetable origin,
will not hold some dyestuffs. Therefore, in the case of these
latter fabrics it is often necessary to apply to the cloth or
to the coloring solution some chemical salt, such as alum,
in order to make the dyestuff adhere to the material. The
^chemical salt applied for this purpose is called a mordant,

190. Printing on Fabrics. — It is often desirable to print
a colored design on a fabric that has been already dyed.
There are three modern methods of printing patterns:
direct printing, discharge printing, and resist printing.

In direct printing the fabric is passed between polished
copper rollers, on the surface of which a design has been*
engraved. When there is to be more than one color in the
design a separate roller is necessary for every additional
color. The coloring material, which consists of dyestuffs
made into a paste, is placed beneath the rollers, a single
color for each roller. As each roller rotates it comes into

CHEMISTRY OF INDUSTRIAL SUBSTANCES 163

contact with the color and impresses the colored design
on the fabric. A strip of steel, called a doctor, removes the
color from every part of the roller except that covered by
the design.

Discharge printing consists in removing color by means
of a chemical from goods already dyed in the piece, thus
leaving a white pattern.

Resist printing consists in stamping a chemical on a plain
white cloth, and dyeing the cloth afterwards. The chemical
makes the dye ineffective on the pattern.

191. Sizing. — Sizing is a process of applying a thickening
agent or mixture to cloth, paper, etc. The change brought
about is distinctly physical. The object of sizing is to add
weight, strength, and smoothness (luster) to the material.
A considerable variety of substances are used in size mixtures,
the more important of which are included in the following
list:

(a) Substances possessing adhesive properties to strength-
en the material and fix other ingredients. This class includes*
flours and starches of wheat, sago, rice, maize, and potatoes.

■

(b) Substances to render the material soft, pliable, and
smooth. This class includes tallow, grease, oils, wax, gly-
cerin, and soap.

• (d) Substances to destroy or prevent the growth of germs
that cause mildew. Zinc chloride is almost exclusively
employed for this purpose.

(e) Deliquescent substances to attract moisture to the
material, whereby it may retain its pliability, and to prevent
powdery substances from being rubbed off. This class

1G4 APPLIED SCIENCE

includes magnesium chloride, calcium chloride, glycerin, and
common salt.

192. Mercerizing. — Cotton may be made to resemble
silk, so far as the luster is concerned, through the application
of a solution of caustic soda under tension. This process
is called mercerization. The effect of the caustic soda is
to cause the cotton fibers to become smooth and cylindrical
in form so that they reflect the light and appear "shiny"
with a strong luster. It is a physical and not a chemical
change.

193. Gassing. — The luster of mercerized cotton may
be increased by passing the material rapidly over a platinum
plate heated to a very high temperature. The effect is to
take off the loose fibers. This operation is called gassing.

194. Spontaneous Combustion. — Spontaneous combus-
tion is an expression used to explain the setting on fire of a
substance without the employment of any external agent,
such as a lighted match, a flame, or a spark. To illustrate:
There are times when a pile of coal will burst into flame
without the application of a flame or spark. The reason
for this is quite different from the reason for the burning of
coal in a stove or under a boiler. The first burning is caused
by spontaneous combustion, and the second by the ordinary
combustion of coal. In both cases, however, the fires follow •
definite laws.

All combustion is a chemical action attended with the
liberation of heat and is the result of the combination of oxy-
gen with the combustible material. Ordinary combustion
or burning is merely the result of a substance being heated,

CHEMISTRY OF INDUSTRIAL SUBSTANCES 165

in the presence of a supporter of combustion like air, to the
point of ignition by some external agent, such as a match.
When a substance oxidizes with great rapidity, a great deal
of heat is evolved and a flame is formed. The temperature
at which the flame forms is known as the point of ignition
or the kindling point.

Certain kinds of damp organic matter, such as soft coal
or cotton rags containing oil, confined tightly may absorb
enough oxygen to raise their temperature to the kindling
point. The result is spontaneous combustion. The quan-
tity of heat is the same whether the combustion is slow or
fast. A quantity of wood that decays gives off exactly the
same quantity of heat as if the same amount of wood were
burned in a furnace, provided in both cases the wood is
completely destroyed. The products of combustion are
exactly the same.

195. Chemical Solution for Extinguishing Fires.— The
most effective method of extinguishing fire is by means of a
solution used in chemical fire apparatus. This solution is
much more efficient for fire-extinguishing purposes than
plain water, because the chemical solution does everything
that water can do exactly in the same way and for exactly
the same reasons. In addition, it forms a considerable
blanket of fire-extinguishing gases which are heavier than
air and better supporters of combustion, and in this manner
'shuts off much more effectively the access of air (oxygen)
to the fire.

Chemical fire-extinguishing solution extinguishes fire more
by smothering than by cooling. The only drawback is
that the supply of chemical solution must necessarily be
comparatively limited. However, a reasonable supply of

166 APPLIED SCIENCE

chemical solution, instantly available, makes a large supply
of water unnecessary.

Questions

1. Why is a knowledge of the chemistry of common industrial
substances desirable?

2. What is the meaning of the expression "carbon has four
allotropic forms"?

" 3. Why do people prefer crystalline to powdered forms of
substances?

4. Describe the importance of the different forms of carbon.

5. Explain the formation of the oxides of carbon.

6. Draw a sketch of an ordinary yellow gas flame and explain
why it is luminous (bright) compared to the blue flame of the gas
stove. Which is hotter?

7. What is an alcohol? Carbohydrate? Fat? Soap? Oil?
Give an example of each kind.

8. What is sand?

9. Describe briefly the following: a dye; clay; gunpowder;
bleaching; bick; mortar; cement; porcelain.

10. What is spontaneous combustion?

11. Explain the action of the chemical solutions used in fire
extinguishers.

CHAPTER XV
MAGNETISM AND ELECTRICITY

196. Nature of Magnetism. — When we take a lump of
lodestone, which is an iron ore, and place it near a piece of
iron, the lodestone will attract the iron. The iron in its
turn will then attract particles of iron. The iron is called
an artificial magnet. Thus iron and steel when brought in
contact with the lodestone have the property of becoming
magnetized and attracting iron. Magnets made of soft iron
lose their magnetism very easily and are called temporary
magnets; while hard iron and steel retain their magnetism
and are called permanent magnets.

197. Shapes of Magnets. — Magnets are of two shapes:

straight or bar (Fig. 68) and - f ^ g^y -«*g^^fc

horseshoe (Fig. 69). In every ^%Kljg^ lUSMP?

magnet there is a Fig. 68.— Bar Magnet with

I* ,-1^ „•*«„,*«,„. Iron Filings,

limited space sur- °

rounding each end or pole in which its mag-
netic properties are exhibited. This is called
the magnetic field. If, for example, magnet-
ized iron filings are sprinkled over a sheet of

paper, they will assume curved lines, bring-
Fig.69 Horse-
shoe Magnet ln & ^° view a few of what are called the lines

with Iron Fil- f force of a magnetic field.. The portion of

this magnetic field that is the strongest
is assumed to contain the greatest number of lines of force

167

168 APPLIED SCIENCE

The total number of lines of force which pass through a fie|d
is called the magnetic flax. The magnetic flux always flows in
a complete circle or circuit. The material through which it
flows affects variously the resistance offered to the free pas-
sage of the flux.

198. The Mariner's Compass. — Experience shows that,
in all cases, like poles of magnets repel and unlike poles attract.
This principle, called the law of magnets, is utilised in the

device known as the mariner's
compass (Fig. 70), which con-
sists of a magnetized steel
needle balanced on a point
so that it will turn freely;
| the points of the horison are
i marked on a compass card.
The needle is acted upon by
the earth, which is a magnet.
The needle behaves the same
way in all parts of the earth.
The north magnetic pole is
near Hudson Bay, the south magnetic pole in the Antarctic
Ocean. As the true North Pole and the magnetic north pole
are not the same, allowance must be made for this variation.
Ships travel from point to point by the assistance of the
mariner's compiim.

199. Nature of Electricity. — As we look about us we find
electricity moving the cars on which we ride and producing
the light by which we see at night, and we naturally ask,
"What is electricity?" That question cannot, as yet, be
answered definitely. Electricity is no doubt a form of energy

MAGNETISM AND ELECTRICITY

169

having properties of its own, but obeying laws corresponding
quite closely to those governing the motion of water. A
great many explanations can be offered by comparing the
action of electricity with water. For example, electricity
flows through a wire in much the same way as water flows
through a pipe. From their likeness it has become popular
to speak of electricity as "juice."

Since electricity is, in a sense, considered a fluid, its flow
is called a current, and any substance, such as copper wire,
through which it flows is called a conductor. All metals,
salts, and solutions, living vegetable substances, and water,
are conductors of electricity. There are some bodies, how-
ever, such as glass and rubber, that offer a resistance so
great as to prevent the passage of electricity. Most vege-
table substances in a dry state, such
as shellac, resin, rubber, paper, and
cotton are in this group. Other
non-conductors are wood, sulphur,
glass, mica, silk, porcelain, and oil.
The path through which a current
passes is called a circuit. When a
path is continuous it is called a closed
circuit, but when there is a break it
is called an open circuit.

Fig. 71. — Lines of Mag-
netic Force Around an
Electric Wire.

200. Relation of Magnetism to
Electricity. — If a piece of copper wire
through which a current of electricity
is flowing is passed through a cardboard
or glass plate and the card or plate is

sprinkled with iron filings, the filings arrange themselves in circular
lines (Fig. 71). If the card or plate is jarred and the iron filings
displaced, they will rearrange themselves in the same circular lines.

170 APPLIED SCIENCE

If, on the other hand, the current is not flowing, the filings will
not assume circular lines. This shows that there is a definite rela-
tion between magnetism and electricity. When a conductor passes
through a magnetic field in the proper direction, it produces a
current of electricity, or when a current passes through a conductor
it produces a magnetic field.

201. Electromagnetic Force. — Soft iron retains very
little magnetism and yet it can be magnetized to such an
extent that it can be utilized in lifting large bodies. When
a bar of soft iron, in the form of a horseshoe, is wrapped round
with copper wire and a current of
electricity is passed through the wire,
the iron becomes a powerful magnet
called an electromagnet (Fig. 72) and
may be constructed to support a
weight of many tons. By making
one magnet fixed and another mov-
able, and by causing one magnet to
revolve within the lines of force of
another, an attraction and repulsion of great intensity can be
created, which will act as a great moving power.

The strength or lifting power of a magnet is measured with
a lever and scales by noticing the number of pounds reg-
istered. The lifting weight is the pull exerted minus the
weight of the magnet. The magnetic flow is proportional
to the number of turns of wire of the conductor and the
current flowing around the turns. The magnetic flux is
inversely proportional to the resistance of the circuit. The
total resistance is the sum of the resistance of the iron path
and the air path.

An electric bell (Fig. 73) depends upon the properties of electri-
city and magnetism for its action. When the button of the bell is

MAGNETISM AND ELECTRICITY

171

pressed by the finger, an electric circuit is completed. The current
flows around the coils of an electromagnet, which attracts a bar
of soft iron metal fastened to a lever, at the
other end of which there is a hammer that
strikes the bell. When the soft iron metal is
attracted the current is broken; this causes
the bar to go back. This backward move-
ment of the bar starts the current again and
the operation is repeated. These operations
are repeated in rapid succession so long as the
button is pressed.

202. Chemical Means of Generating
Electricity. — Electricity may be generated
by chemical agencies. When any two
different metals, such as zinc and copper,
are placed in an acid or solution and
wires are attached to them and connected, a current of elec-
tricity flows through the wire. This arrangement of metals
in a liquid is called a cell. Wlien the wires are not connected,
bubbles of hydrogen collect around the zinc plate, but the
moment the wires are connected, the hydrogen gas begins
to appear on the copper plate.

Commercial zinc contains a great many impurities, such as
iron and carbon. Little circuits are set up between the zinc
and carbon impurities; hence the bubbles which appear on
the zinc when it is immersed in the acid. This bubbling may
be avoided by amalgamating the zinc, i.e., by covering it
with mercury so that the zinc is used up only when the cur-
rent is flowing.

Fig. 73.— Electric
Bell.

203. Electrolysis. — The breaking up of a substance by
passing electricity through a solution of the substance is
called electrolysis and the solution in which it takes place

172 APPLIED SCIENCE

an electrolyte. This process is of great industrial importance.
All chemical compounds — acids, salts, and bases — are
made up of two parts; the positive or metallic part, and the
negative or non-metallic part. When any compound is dis-
solved, it breaks up partially into these two parts. The
positive or metallic portion is charged with positive electri-
city and is attracted to the negative electrode or plate.

204. Units of Measurements. — A quantity of electricity,
like a quantity of water, may be measured. Since the flow
or quantity of water depends on the pressure or "head" and
on the resistance of the pipes, so the quantity of electricity
depends upon the pressure and the resistance of the wires.

The acting force which gives rise to, or maintains, a current
or flow of electricity is called the electromotive force (abbre-
viated E.M.F.). The E.M.F. corresponds to pressure in
relation to water and is measured by a unit called a volt.
That force against which the E.M.F. acts, that is to say,
that force which retards the flow or current, is called the
resistance, and corresponds to the friction of pipes in rela-
tion to water. Resistance is measured by a unit called an
ohm. The quantity of electricity corresponds to the quart
or gallon of water. The current of electricity, or rate of flow,
is measured by a unit called a coulomb, which is the quantity
passing per second of time, and corresponds to a flow of
water of so many quarts or gallons per second. A rale of
flow of one coulomb per second is called an ampere. The
unit of rate of electrical work is the product of the E.M.F.
and the rate of flow or current — just as the pressure with
which the force acts is the work performed. The rate of
flow of electricity or current is proportional to the impelling
pressure or head.

MAGNETISM AND ELECTRICITY 173

205. Ohm's Law. — There is a definite relation between
the volts, ohms, and amperes of a circuit of electricity. This
relation was first stated by a man named Ohm, and is known
as Ohm's Law.

The quantity of electricity in amperes delivered by a
circuit is obtained by dividing the electromotive force in
volts by the resistance in ohms. This rule may be abbrevi-
ated into a formula:

Volts
Amperes =

Resistance
E

I =
R

where / is the quantity of electricity in amperes, E the
electromotive force in volts, and R the resistance in ohms.
By transformation of the formula

E = RI

E
R = —
/

Thus, if we know any two of the three units of a circuit,
it is possible to find the third.

206. Measurement of Electric Power. — Electric power
is measured in the same way as is water power. Water
power is equal to the quantity of water in pounds that falls
per minute multiplied by the "head" or "drop" in feet.

Electric power is equal to the intensity of current in
amperes multiplied by the pressure in volts. The unit of
electric power is a watt. A watt is the power given by a current
of one ampere flowing with a pressure of one volt.

174 APPLIED SCIENCE

The watt is a very small unit, so that the kilowatt (1000
watts) is generally used. Electricity is measured by the
number of kilowatts used per hour. To illustrate: If an
electric generator gives 14 kw. for 9 hra., it produces 126
kilowatt-hours of work.

207. Simple Voltaic Cell.— The voltaic cell (Fig. 74)
consists of a strip of zinc and a strip of copper in a glass jar

nearly full of sulphuric acid, supported
side by side without touching each
other. These two metal strips are
connected by a copper wire. Electric
current will flow from the copper to
the zinc. The copper is called the
positive pole and the zinc the nega-
tive pole of the cell. The current
may be detected by placing the free
ends of the copper wire on the tip of

Fio. 74.— Simple Voltaic the tongue. A slight stinging sensa-
tion will be felt, thus proving the

presence of an electric current.

208. Battery Cells. — When electricity is desired for
bells, burglar alarms, etc., it is obtained from battery cells.
The electricity is generated by chemical means. There are
many forms, each of which has its advantages and disad-
vantages. The four types most commonly used are described
below.

The Leclanchi cell consists of a glass jar containing a solution of
sal ammoniac (ammonium chloride) with a zinc rod for one pole
and a carbon plate in a block of compressed manganese dioxide
for the other. The purpose of the manganese dioxide is to prevent

MAGNETISM AND ELECTRICITY 175

polarization of the cell, that is, the collecting of bubbles of hydrogen
on the plate. Polarization diminishes the voltage by increasing the
resistance. As the manganese dioxide is in a powdered form it
hardens slowly, and if too large a current is taken from the cell,
polarization takes place. The advantage of this type of cell lies
in its freedom from local action and in the fact that it can be used
for a long time without deterioration.

The Danieil ceU consists of a zinc sulphate solution and a copper
plate in a copper sulphate solution. They are separated by a porous
cup to prevent undue mixing. As no hydrogen is developed in
this cell, there can be no polarization. When the circuit is left
open the copper coats the zinc and impairs its efficiency.

The gravity cell consists of a copper sheet placed in the bottom of a
glass. Crystals of copper sulphate are placed over the plate and
water is added until the jar is nearly full. A zinc plate is suspended
at the top of the jar and sulphuric acid added to start the cell. The
sulphuric acid acts on the zinc forming zinc sulphate. The zinc
sulphate is so much lighter than copper sulphate that, so long as the
cell is kept on a closed circuit, the solution mixes but slightly.

The bichromate ceU is used for operating small cells or motors,
and consists of a zinc and carbon plate in a solution of chromic acid
(mixture of bichromate and sulphur
acid). When the cell is not used, the zinc
must be removed from the liquid, so that
the chromic acid will not attack it.

209. Dry Cells. —Dry cells (Fig.
75) are not actually dry. They con-
tain the same ingredients as the
Leclanche cell, but instead of con- F, °- n ~ Dt V Cell.
taming a fluid electrolyte they have the solution absorbed
in a plastic mass of manganese dioxide and plaster of Paris
or other inactive substances.

The great advantage of the dry cell lies in the fact that
the liquid will not spill out under any conditions and there
are no vapors arising from the cell, as it is almost invariably

176 APPLIED SCIENCE

sealed. Dry cells have the disadvantage, however, of hav-
ing a very high internal resistance, because the electrolyte
cannot so readily carry the current when in this form as it
can when fluid. Furthermore, the small amount of liquid
present and the method of construction do not allow the
free escape of the gases which form when the cell is in opera-
tion. For this reason, the cell becomes polarized very soon
and is satisfactory only where intermittent service is needed.
It should not be used where the current must flow continu-
ously for any length of time.

In order that the internal resistance of the cells may be
reduced to its lowest point, the zinc and carbon are arranged
to present as great a surface as possible and to be as near to-
gether as circumstances will allow. This arrangement affords
a large conductor of short length for the current to flow through
inside the cell. The carbon should be as porous as possible, as
it can then absorb a great amount of oxygen and thus neutralize
the hydrogen gas produced by the cell when in operation and
prevent the cell from polarizing as soon as it would if there
were no oxygen present to combine with the hydrogen.

210. Storage Batteries. — The storage batteries of com-
merce (Fig. 76) are built up with electrodes composed prin-
cipally of lead peroxide (Pb0 2 ) as the positive electrode, and
sponge lead as the negative electrode. The positive plate
is hard, like soapstone, while the spongy lead is so soft that
it may be cut by the finger nail. Both plates are immersed
in a dilute solution of sulphuric acid. On discharging the
battery, the metallic lead, peroxide, and sulphuric acid react
forming lead sulphate and water. On charging, the reverse
takes place; the lead sulphate forms metallic lead, lead
peroxide, and sulphuric acid.

MAONETISM AND ELECTRICITY 177

When the battery is fully charged and in good condition,
the positive plate is a dark reddish brown or chocolate color,
while the negative plate is slate-colored. On discharging
the battery, the 8O3
is obtained from sul-
phuric acid, which
combines with
water and forms
lead sulphate with
lead. When the
battery is recharged
the current releases
the S0 3 , restoring
the plates to their
previous condition.
Storage batteries
are measured in
ampere-hours.
Thus a 100 ampere-
hour battery will
give a continuous

discharge of 1214

- r> . *ig- 76.— One Form of Storage Battery.

amperes for 8 hrs.

Theoretically, it should give a discharge of 25 amperes for

4 hrs., or of 50 amperes for 2 hrs.

The capacity of a cell is proportional to the exposed area
of the plates, the number of plates, and the active material
present.

211. Arrangement of Electrical Apparatus. — A group of
cells or electrical apparatus may be arranged in different
ways. The wire from the zinc of the first cell may be

178

APPLIED SCIENCE

JuOuOuT

■ ' Jj

connected to the carbon of the second, etc. (Fig. 77), or the
wire from the zinc of the first may be connected to the zinc
of the second, and the wire from the carbon of the first to
the carbon of the second, and so on. (Fig. 78.)

A battery is rated commercially by the resistance, and by
the electromotive force of a single cell. There are two r&-

r — , l — — distances to be con-

jl J . h j h j sidered in the calcula-
tions of the capacity
of batteries: the re-
sistance of the bat-
tery, due to polariza-
tion, etc., which is
represented by R, and the resistance of the external circuit,
such as the wire, which is designated by r. The current given
by a battery — according to Ohm's Law — is equal to the elec-
tromotive force divided by the resistance, which in this case
is divided into two parts.

Fig. 77.— Cells Ar-
ranged in Series.

Fig. 78.— Cells Ar-
ranged in Parallel.

Current =

Electromotive force

Resistance (internal) + resistance (external)

C =

R + r

212. Galvanometer. — One of the instruments used to
measure electricity is called a galvanometer. It depends
for its usefulness on the principle of magnetism. There are
many varieties of this device. The D'Arsonval galvan-
ometer (Fig. 79) consists of a horseshoe magnet placed
vertically. Between the poles of the magnet there is an iron
cylinder; above the cylinder is suspended a fine wire wound
on a thin copper frame so that it will swing freely between

MAGNETISM AND ELECTRICITY

17<J

the cylinder and the magnet poles. When the current is
sent through the coil it becomes a magnet which is acted
upon by the horseshoe magnet which
causes it to be deflected. The deflection
is measured on a scale which gives the
measurement of electricity.

213. Ammeter. — An ammeter (Fig.
80) is simply a commercial form of gal-
vanometer. It is constructed in the same
way, but only a small fraction of the
current to be measured passes through the
coil. The greater portion passes through
the shunt, which is located in one of the Fio. 79.— D' Arson al
leads coming from the machine. The Gal™nomete.
terminals on the shunt are connected to the terminals on the
ammeter by a pair of flexible leads about 10 ft. long. After
the ammeter is made, it is tested
by operating one machine on a
certain number of lamps at exactly
110 volts and then throwing ofl
that machine and operating the
same number of lamps with an-
other machine. If readings on
the ammeter are the same, it is
correct.

—Ammeter.

214. Voltmeter.— The volt-
meter is an instrument used to
determine the voltage of a circuit. It consists of a light,
rectangular coil of copper wire wound upon an aluminum
frame, pivoted in jeweled bearings, and capable of rotating

180 APPLIED SCIENCE

in a space between a soft iron core and the pole of a perma-
nent magnet. A light tubular pointer, attached to the coil ;
moves over a graduated scale. The current is introduced
into the coil by means of two spiral springs which serve to
control the movement of the pointer. When a current
passes through the wire, the coil tends to turn in a certain
direction against the action of the springs which tend to hold
it in place. The amount of deflection is proportional to the
voltage. The scale is graduated to read in volts. It is
accurate and substantial. This instrument should not be
placed in a strong field, as such a field will permanently
affect the permanent magnet. In this case the scale must
be graduated again.

215. Electric Pyrometers. — In certain manufacturing
processes it is necessary to determine the temperature of
furnaces. Hence the need of some instrument that is simple,

accurate, and capable of
being handled by a work-
— J man without special me-
chanical or . electrical

F. u . 81. -Pyrometer. knowledge. Such an in-

strument is found in the
electric pyrometer (Fig. 81) which consists of a thermo-ele-
ment, or insertion tube, for exposure to the heat, and a
sensitive galvanometer to indicate the temperature at a con-
venient distance from the source of heat.

The principle underlying this pyrometer is that when any
metal is heated an electric current is set up. The intensity
of the current depends upon the temperature to which the
metal is heated. Thus, measuring the current measures also
the temperature at the extremities of the metal.

MAGNETISM AND ELECTRICITY 181

The lower portion of the thermo-element, which is inserted
into the metal, is protected by crucible material (a clay sub-
stance that will resist great heat) or by a tube of pure graphite
with an insertion of quartz glass. In the latter case, the
graphite protection can only be 8 in. long, whereas in the
former case (for temperatures up to 2370° F.), the protection
tube for the thermo-element can be any desired length. The
latter is particularly valuable in cases where the increase
of temperature has to be watched while the crucible is in
the oven, so that it can be lifted out at the correct
moment.

The thermo-element consists essentially of two wires or
rods of different materials, which are joined or fused together
at their extreme ends and exposed to the heat. These ends
are called the hot junction. The other extremes of the rods
are called the cold junction. The cold junction projects
into the open air and is connected to the leading wires of
the galvanometer by means of screws.

The two rods of the thermo-element are of different elec-
trical conductivity. If, therefore, the ends of the rods at
the hot junction are heated, a difference of potential is pro-
duced, causing an electric current to flow, varying in strength
with the degree of the thermal difference between the cold
and the hot junctions, or with the intensity of the heat to
which the thermo-element is exposed. The relation of this
current to the temperature has been determined accurately
by experiment, and the scale of the galvanometer can there-
fore be divided to read directly in Fahrenheit or Centigrade
degrees. Thus, as soon as the thermo-element is exposed
to heat or cold, the electric pressure or current produced in
the two rods actuates the mechanism of the galvanometer,
and the needle of the latter indicates directly the exact

182 APPLIED SCIENCE

temperature of the hot junction at the place where the
thermo-element is inserted.

Inasmuch as the electric current produced in the thermo-ele-
ment through the heating of the hot junction depends on the
difference between the temperature at the two extremes of
the rods, it is, of course, essential that the outer ends of the
rods or the cold junction be kept cool.

The insertion tubes are made in various lengths and fitted
with protection tubes and flanges (screwed couplings) to
adapt them exactly to the different processes or apparatus
for which they are required. The constituents of the thermo-
element vary according to the intensity of the heat for which
they are intended. For temperatures up to 1100° F. or
600° C, the element consists of nickel and a special metal
alloy; for temperatures up to 2300° F. or 1250° C, nickel
and a special carbon are used; while for temperatures up
to 2900° F. or 1600° C, platinum and platinum rhodium
give the best results.

216. Galvanometers and the Measurement of Heat. —

Galvanometers can also be used to measure temperature
because, as noted above, an electric current is formed when
metals are heated. The current thus produced is propor-
tional to the temperature to which the metal is heated.
Consequently, a galvanometer reading in current indirectly
measures the temperature.

Galvanometers are used for the measurement of lower
temperatures up to 1100° F. They are hung vertically,
and the scale and finger are made very bold, so as to enable
the operator or workman to recognize the temperature at a
glance, without having to go close to the instrument.

When used for scientific and other work requiring exact-

MAGNETISM AND ELECTRICITY 183

ness and precision, galvanometers constructed to register up
to 1100° F. can be used only in a horizontal position on a
table or in a bracket. This limited use is also common to
galvanometers constructed to register higher temperatures
up to 2900° C, and to those designed to register very low
temperatures.

Questions

1. What is magnetism?

2. Explain the difference between a natural and an artificial
magnet.

3. Describe the shapes of magnets.

4. Explain the expressions: "magnetic flux," "lines of force,"
"magnetic field."

5. What is a mariner's compass?

6. What is the relation between electricity and magnetism?

7. What is electromagnetic force? Name some of the indus-
trial uses of this principle.

8. Describe an electric bell.

9. What is a simple voltaic cell?

10. Describe the chemical means of generating electricity.

11. What is electrolysis? Is it an important industrial process?

12. Describe some of the most common battery cells.

13. What is a dry cell?

14. Explain the use of a storage battery.

16. What is an electric pyrometer? Describe it.

16. What is a galvanometer?

17. What is an ammeter? Voltmeter?

18. In what units is electricity measured?

19. Explain Ohm's Law.

20. Describe the arrangement of electrical apparatus.

CHAPTER XVI
FRICTIONAL OR STATIC ELECTRICITY

217. Nature of Current. — When certain bodies, such as
leather belting and pulleys, paper and steel plates, or cotton
and steel rolls, are rubbed together, sparks are frequently
produced. This kind of electricity is called frictional or
static, and is quite dangerous because of its liability to cause
a fire. Frictional electricity acts in many ways like magnet-
ism. To illustrate: A magnetized body has at least two
poles which are unlike and the magnetism appears more or
less concentrated. In like manner, when a body which is
rubbed becomes electrified, it shows two different kinds of
electricity. For instance, if a sheet of glazed paper is
rubbed vigorously with a smooth pencil and then placed
over a small piece of paper, the sheet attracts the small
piece, showing that the bit of paper has a different electri-
fication from that of the sheet. When two different sub-
stances are rubbed or passed over one another quickly, one
becomes charged positively with electricity, while the other
is negatively or oppositely charged.

218. Leyden Jar. — Static electricity may easily be drawn off
and bottled up in what is called a Leyden jar. This is a glass jar
(Fig. 82) three-quarters of the surface of which is coated inside and
outside with tin-foil. A brass rod with a knob at the end goes
through the cork and into the jar until it touches the inside coating
of tin-foil. If the knob of this jar be held about half an inch from
the conductor of an electrical machine, sparks will pass for some

184

'/> -

FRICTIONAL OR STATIC ELECTRICITY 185

time from the conductor to the knob of the jar and will then cease.
The jar is then said to be charged, that is, the coating on its inside
is (as full of electricity as it will hold. The jar can be charged only
when the outside is connected with the earth; if the q
outside be insulated, no electricity can be collected in
it. It is enough to hold the outside of the jar in the
hand, as in this way it is connected with the earth
through the body. The positive charge from the con-
ductor then passes into the inside coating of the jar.

219. Loss Due to Frictional Electricity. —
Frictional electricity causes considerable loss in
the manufacture of paper, cotton, wool, etc. When tF 1 ^'^ j^
the paper or material passes over machines, two

forms of electricity are generated, each with different prop-
erties of attraction. The result is that the fibers of the
paper, cotton, wool, etc., are scattered and made uneven be-
cause of the attraction of the electricity on the fibers to
the opposite electricity on the machine.

220. Electric Neutralizes — Frictional electricity may be
removed by attaching to the machine a device called a neu-
tralize^ which is really a transformer.

This device may be bolted to the wall or ceiling in any convenient
place and serves to deliver the electric current in the proper form
to the various machines where the static electricity is to be neutral-
ized. A single line of heavily insulated wire leads from the trans-
former to the various points of treatment. This line may be run
along the ceiling over the machines or under the floor on which the
machines are set. On each machine is placed one or more inductors
connected to the line wire. The inductor is a steel tube of 1J^ in.
outside diameter and of suitable length to reach across the machines.
This tube is also slotted on one side from end to end and has a series
of porcelain blocks in the slot. These blocks contain the active

186 APPLIED SCIENCE

points from which the influence is radiated to the charged material.
The tube itself is grounded, but the line wire is connected directly
with the cable inside of the tube. The connection is made through
a convenient form of removable socket at the end of each inductor.
The inductor is placed at some point in the machine where the
charged material may pass by it at a distance of from 1 to 3 in.,
and the material becomes instantly neutralized thereby, even when
running at a speed of 1000 ft. per minute. On a printing press, the
inductor is placed across the press so as to treat the paper just
after it leaves the cylinder or at least before it goes into the pile.

Electricity may be detected in some substances, such as cotton,
glass, and wool, better than in a metal like silver, because the first-
named substances are non-conductors and do not allow the electri-
city to escape easily while the reverse is true in the case of conductors.
Moist air is a far better conductor than dry air; hence, electricity
shows itself on cotton when the air is dried. In order to keep the
air moist, humidifiers (apparatus for discharging moisture in the
air) are distributed throughout cotton mills.

221. Lightning. — Much of the electricity of the air is
caused by the rubbing of moist air against dry air. A great
deal of moisture is made by the sun or wind turning into
vapor or mist the salt water of the ocean. More water is
turned into vapor during the heat of summer and autumn
than in winter and for this reason there is more lightning
in warm weather than in cold. The electricity in the air
in clear weather is generally positive, but during fogs, rains,
or snows it tends to change to negative. Sometimes it
happens that two clouds, one charged with positive electri-
city and the other with negative electricity, come near each
other. The two kinds of electricity then rush together and
we see a flash of lightning and hear thunder. Lightning is
the same thing as a spark from an electrical machine, the
only difference being that a flash of lightning is sometimes
several miles long and the spark only a few inches.

FRICTIONAL OR STATIC ELECTRICITY 187

222. Danger from Lightning. — If a cloud filled with
one kind of electricity comes near the earth when the
latter is filled with the opposite kind, the cloud may dis-
charge its electricity to the earth. If any tall object,
such as a tree, a steeple, or a house, happens to be near
where the cloud discharges, the electricity will often pass
down it to the earth. In this way houses are sometimes
injured and set on fire and great trees are split up into
small pieces. Sometimes, too, human beings and animals
are struck and killed. It is not safe, therefore, to stand
under a tree or close to a high house during a thunder
storm.

223. Forms of Lightning. — We see lightning in several
different forms; sometimes its flash is straight, sometimes
it looks forked or zigzag, sometimes it is round like a ball,
and sometimes it spreads over the clouds like a sheet of fire.
When a thunder cloud is near the earth, the flash comes
straight down, because there is but little air for it to pass
through. When, on the other hand, the cloud is at a con-
siderable distance from the earth, the air in the path of the
lightning is made denser or thicker by being pushed together,
and as lightning can pass more quickly through thin than
through thick air, it flies from side to side so as to pass
where the air is thinnest. This makes its path zigzag or
forked. When there is a great charge of electricity in a cloud
it sometimes forces its way through the air in the shape of a
ball. What is called sheet lightning is either the reflection
or shine on clouds of a stroke of zigzag lightning which is
too far off to be seen, or light discharges of electricity from
clouds which have pot enough in them to make zigzag
lightning.

188 APPLIED SCIENCE

224. Cause of Thunder. — When lightning passes through
air it leaves a vacuum, and the air rushing in to fill it makes
the noise which we call thunder. We do not usually hear
this until some time after the flash of lightning because light
travels more than a million times faster than sound. When
the thunder cloud is at a distance, the sound comes to us
little by little and we then call it rolling thunder; but when
the cloud is near the earth the sound comes in one great
crash. You can generally tell how far off a thunder cloud is
by noting how long the time is between the flash of lightning
and the sound of the thunder. If you can count five as
slowly as the tick of a clock between the two, you may be
sure that the cloud is more than a mile away.

225. Use of Lightning Rod. — Lightning on its way to the
earth always follows the best conductor and consequently
will leap from side to side to find a building or a tree. It is
attracted to pointed things rather than to round or blunt
things, and for this reason lightning rods are made with sharp
points. Buildings properly fitted with lightning rods are
safe from being struck by lightning, because the rods lead
the electricity into the earth. When a cloud filled with
electricity comes over the rods, the electricity will flow
down them until the cloud is discharged. We see no flash
and hear no thunder; and we may feel sure that the building
will not be struck. The tops of lightning rods are usually
silvered or gilded, so that they will not rust and become worth-
less. The lower end of the rod must be carried down into
damp earth; if the earth is dry it is better to carry the end
into a well, because dry earth is not so good a conductor as
moist earth and the lightning might leap from the rod at the
lower end and go into the cellar of the building. High chim-

FRICTIONAL OR STATIC ELECTRICITY 189

neys should have rods on them because soot is a good con-
ductor, as is also the vapor which arises when fires are
burning.

Questions

1. What is frictional electricity?

2. Has frictional electricity industrial importance?

3. What is a Leyden jar?

4. Does frictional electricity cause any danger? Explain.
6. How may this danger be removed?

6. Describe an electric neutralizes

7. For what are humidifiers used in mills?

8. Describe lightning.

9. What dangers are attached to it?

10. Name the different forms of lightning.

11. Explain the relation of thunder to lightning.

12. What is a lightning rod?

CHAPTER XVII

GENERATION OF ELECTRICITY ON A COMMERCIAL

BASIS

226. Generating Large Amounts of Current. — We have
studied how electricity is generated by chemical means in
batteries and by friction. These two forms of electrical
energy are very valuable, for commercial purposes where a
small current is sufficient, such as is necessary for ringing
electric bells, etc. The current generated by these two
methods is not, however, strong enough to drive large
machines or to light lamps. The commercial method of
generating electricity on a large scale is by means of a
machine called a dynamo or generator. The principal parts
of a dynamo are: (1) the magnetic field, produced by per-
manent magnets or electromagnets; and (2) the armature,
which consists of a moving coil or coils of wire wound on a
revolving iron ring or drum.

227. The Principle of a Dynamo. — The generation of
electricity by a dynamo is based on a principle of magnetism
called induction. When the lines of force that pass from the
north to the south pole of a magnet are cut by a wire there
is produced or induced in the wire a current of electricity.
That is, if we take a loop or coil of wire which has no current
in it and a magnet which also has no current, and move the
loop or coil l>etween the poles, as shown in Fig. 83, a momen-
tary current is produced. If a series of loops or coils are

190

GENERATING ELECTRICITY COMMERCIALLY 101

used instead of one loop, a current may be generated con-
tinuously. This method of generating electric current is
called induction.

The strength of a current in electromotive force set up
by induction depends upon: (1) the strength of the magnet,
(2) the number of turns of wire in the coil
or loop, and (3) the speed with which the
magnetic lines bf force are cut, that is,
the speed at which the coil rotates.

228. Direction of an Induced Current, fig. 83.— Magnetic

—The direction of an induced current de- , Field -. Showing

loop of wire rotat-

pends upon two factors: (1) the direc- ing between the
tion of the motion of the wire, and (2) ^\ h (s^olestf
the direction of the magnetic lines of force, a magnet.

A very valuable method of determining the direction of
current used in practical life is called Fleming's Rule.

Place the thumb, forefinger, and center finger of the right
hand so as to form right angles to each other. If the thumb
points in the direction of the motion of the wire, and the fore-
finger in the direction of the magnetic lines of force, the center
finger will point in the direction of the induced current.

It is very important to know the direction of the current
in revolving a loop of wire between the poles of a magnet
in order to understand the working of a dynamo.

Examine Fig. 83 and notice the loop of wire between the poles
of the magnet. If the loop is rotated to the ri^ht, as indicated by
the arrow head, the wire XB moves down during the first half of
the revolution. According to Fleming's Rule, the current would be
directed from B to X. The wire YA would move up during the
first half of the revolution and the current flow from A to Y. As
the result of the first half of the revolution, the current would flow
in the direction A YBX.

192 APPLIED SCIENCE

Repeat the reasoning for the second half of the revolution. Notice
that for every complete revolution, the current reverses its direc-
tion twice. It is accordingly called alternating current. As the
strength of the current depends upon the number of lines of force
cut, so the induced electromotive force starts at zero, goes to a
maximum, and then back to zero in the first half-turn. That is,
the induced electromotive force reaches its maximum when the
loop is in a horizontal position because it cuts the most lines of
force at this position. It cuts the least number of lines of force
at the beginning and at the end of each half-vertical revolution.

229. Commutator. — We have seen that the current
generated in the coil is alternating. Alternating current
is very valuable for lighting and power, but there are cases
in electroplating and charging storage batteries where it is
absolutely necessary to have the current flow in the same
direction. To do this, it is necessary to add to the dynamo a
device called a commutator, the object of which is to make
the current flow in one direction in the external circuit,
regardless of the fact that the current reverses twice in every
revolution.

A commutator consists of copper bars which are arranged
in circular form and separated or insulated from each other
by thin plates of mica. The bars connect with the arma-
ture wires, so that the current, as fast as it is generated, flows
from the armature to the segments of the commutator.

230. Armature Brushes. — The electricity is taken off
the commutator by strips of carbon which touch or lean
upon it. There are usually two brushes on the opposite
sides of the commutator. The brushes, when adjusted,
can shift sections on the commutator just when the loop
is in a vertical position, so that the current will flow out of
the positive brush and in at the negative brush.

GENERATING ELECTRICITY COMMERCIALLY 193

231. Armature and Core. — The armature of a dynamo
(Fig. 84) consists of a steel or iron shaft on which are mounted
a large number of thin circular iron disks held together by
bolts. This arrangement makes a cylinder with a groove

Pia. 84. — Armature.

cut in it, running parallel to the armature shaft. Insulated
wire is wound around the core and laid in the grooves, which
are lined with mica or some other insulating material. The
wires are painted over with shellac. Binding wires are
wound on the outside to hold the armature coils in place.

The iron core or shaft is used in the armature to concen-
trate the lines of force and to keep them from escaping.
The electric current is generated by the rotary motion of
the armature between the poles of the magneto.

232. Action of a Dynamo. — A dynamo, then, is a machine
for transforming mechanical energy (which is the energy that
rotates the armature) into electrical energy, and for forcing
the current of electricity through the wires.

A dynamo, when in action, may be considered as a pump,
which raises electricity from a low level or pressure to a high
level. When the dynamo is in action the electricity flows

194

APPLIED SCIENCE

through the circuit; when it stops the electricity ceases to
flow.

mmcmcua

233. Classes or Types of Dynamos. — There are three
classes of dynamo machines on the market — series, shunt,

and compound — each one adapted for
special work. They differ in the man-
ner in which their field magnets are
wound.

234. Series Machine. — A series ma-
chine (Fig. 85) is a dynamo which
allows all the current produced to pass
through the field magnet coils by taking
1 the wire from one brush and carrying

^*«t' 85.-—Senes- ^ the required number of times around
Wound Dynamo. „ , , t . Al _

the field magnet, and then connecting
it with the external circuit. The other end of the external
circuit is connected with the other brush. Such a machine is
not usually found on the general mar-
ket, but is a common form of motor
made especially for traction purposes.

235. Shunt Machine. — A shunt
dynamo (Fig. 86) is a machine which
has only a portion of its total current
passing through the field magnet coil.
It is used in all cases where it is desir-
able to have a constant pressure voltage Fig. 86.— Shunt-Wound
at all loads, as in the case of the ordinary Dynamo,

parallel or multiple system used for lighting buildings. The
shunt machine is used in large plants, where the diversity

GENERATING ELECTRICITY COMMERCIALLY 195

factor is so large that the varying demands of customers tend to
average up and keep the load either constant or very nearly so.

236. Compound Machines. — A compound dynamo (Fig.
87) is one having two series of windings; one series winding,
around the part through which the main
current flows, and a shunt winding
through which a fraction of the main
current flows. Compound machines
are used in railway power plants, be-
cause of the violent fluctuations of load,
and in small lighting plants of low
diversity factor, where the consumers'
demands fluctuate widely.

Fig. 87. — Compound-
Wound Dynamo.

237. Direct Connected Machine.
— A direct connected dynamo is one
which is driven by an engine without the use of a belt; that
is, the armature shaft is connected to the engine shaft by
means of a flexible device; or the engine shaft is made extra
long with a bearing, and the armature is mounted on the
shaft. This device saves space, is quiet in operation, and
increases efficiency, since there is no loss due to transmission
of power by belts.

238. Direct and Alternating Dynamos. — While dynamos
vary in the manner of winding the fields and armatures as
described above, the most important difference between
the different types is in the kind of current generated. This
classification divides dynamos into the two types of direct
and alternating. An alternating current dynamo is similar
in its action to a direct current dynamo, except that in the

196 APPLIED SCIENCE

former the two ends of the various armature coils are con-
nected in a ring. As the armature travels past the poles
of the field magnet, the armature coils cut through the mag-
netic field in opposite directions. This produces a flow of
current in the coils which reverses as the particular wire
passes each pole. The current is collected by means of the
rings, and is transmitted through the circuit as a series of
rapidly oscillating pulsations. It is necessary to have or
maintain the magnetic field of an alternating current dynamo
in a constant condition; that is, the lines of force must
always travel between the poles in a constant direction.
To attain this reshlt, the field must be excited (receive its
power) from a dynamo generating a continuous current. '

239. Care of Dynamo. — A dynamo to run properly must
be kept clean and dry. The parts that require the greatest
care are the commutators and brushes. The commutator
should be kept clean by wiping it with a hard cotton cloth.
The occasional application of a little vaseline tends to di-
minish friction between the commutator and brushes. Oil
should never be used for this purpose. As the commutator
becomes roughened with age, it should be smoothed by hold-
ing fine sandpaper against it while the machine is revolving.
If the commutator gets out of true (out of adjustment), it
must be turned down in a lathe. If it becomes wet, the
insulation of the armature and field coils will be injured or
destroyed, because in such a case resistance between the
frame and the electrical part becomes low. A commutator
in which this trouble occurs is said to be "badly grounded."
There should be an insulation resistance of 10,000,000 ohms.
The bearings of a dynamo require no more attention than the
bearings of any other machinery.

GENERATING ELECTRICITY COMMERCIALLY 197

240. Electric Motor.— An electric motor (Figs. 88, 89, 90,
91) is a machine for transforming electrical into mechanical
energy. An electric current causes the armature to rotate,
and the mechanical energy due to the rotation may be uti-
lized (o drive machinery. The motor is quite similar to a

Fia. 88.— An Electric Motor.

dynamo; in fact, the direct current motor is almost identical
with the dynamo in structure and circuit, although in detail
of design its external appearance is sometimes quite different.
The principle of magnetism on which the direct current motor
works is as follows :

When a current of electricity is passed through a coil of
wire on the armature, the coil will always revolve so as to
include as many lines of force as possible. When it reaches
this position, the commutator changes the current in th;>

198 APPLIED SCIENCE

coil so that the armature must again rotate a half-revolution
in order to include the greatest number of lines of force. Each
turn of wire acts in the same way, so that the continual
force acting on the armature causes it to rotate. By means

of shaft and pulley, the energy may be transmitted to other
machines and made to do work. The direction in which a
motor runs may be reversed by changing the connection so
that the direction of current is reversed through either field
or armature.

241. Kinds of Motors. — There are different kinds of
motors as there are dynamos. Series motors are used in
hoists, cranes, railways, etc., where it is necessary to start
with a full load and where the automatic regulation of speed
is not necessary. Shunt motors are used when automatic

GENERATING ELECTRICITY COMMERCIALLY 199

regulation is desired. In starting any direct current motor,
it is necessary to put a considerable resistance in series with
the armature. Otherwise, the very low resistance of the
armature would permit the flow of an enormous current,

which would blow fuses or overheat armature coils and cause
excessive sparking. As the machine increases in speed this
resistance is cut out by using a starting box with each motor.

242. Electric Railway Motors. — The work of the electric
railway requires a special type of motor of great flexibility.
For example, the current demanded by a motor in starting
a car is always in excess of the current afterwards required
to run the car at full speed on a level track. The rating of a
railway motor is the horse-power output it will deliver during
a one-hour run. at a rated voltage at the brushes with a

200 APPLIED SCIENCE

temperature rise of any part of the motor not exceeding
70° C. A car motor usually has its four poles covered so
as to be waterproof. It transmits power by means of a
single reduction gear. The motor is suspended at one end
upon the car axle, and the spring is suspended at the other
end.

243. Resistance Box. — A device to resist or check the
flow of current is commercially called a resistance box. It
generally consists of an insulated wire, wound in a spool,
the ends or terminals of which are fastened to large brass
blocks. If the spools contain a large amount of silk, mois-
ture tends to accumulate and cause inaccuracy. The plugs
should be cleaned with coarse paper.

244. Rheostat. — A rheostat consists of a number of
coils of wire connected in series for the purpose of introducing
resistance into the circuit. An adjustable device allows the
resistance to be varied by cutting out as many of the coils
as is desired.

245. Starting Box and Controller. — A starting box is a
rheostat used to cut down the voltage in the line, when start-
ing a motor. The current should flow through it only while
the motor is attaining its normal speed, the resistance being
decreased as the speed of the motor increases.

A controller is a rheostat used in connection with a motor
to cut down the voltage, and thereby to control the speed of
the motor. It differs from the starting box in that it is in-
tended for continuous service.

246. Efficiency of Dynamo. — The efficiency of a dynamo
is the quotient obtained by dividing the amount of electric

GENERATING ELECTRICITY COMMERCIALLY 201

power furnished by the dynamo by the amount of mechanical
power delivered to the dynamo. It is measured by indicat-
ing the engine while running the dynamo at full load and
noting the reading of the ammeter and voltmeter, and then
indicating the engine when the dynamo is idle. The differ-
ence between the two readings is approximately the mechani-
cal power supplied to the dynamo.

Watts Volts X Amperes

= = Horse-Power

746 746

Motors are rated in horse-power (H.P.) Dynamos are
rated in kilowatts (kw.).

1 H. P. = 5i kw.

247. Electric Transformers. — The commercial require-
ments of users of electricity are best served by distributing
electricity at high voltage and low
amperage and by changing the
same current into low voltage
and high amperage by means of
transformer placed on a pole, or
better in a vault, before the elec-
tricity enters the building.

A , - /TV rtffc v . . Fig. 92.— A Transformer.

A transformer (Fig. 92) consists

of three parts: (1) the primary coil, which is the wire which

connects with the alternating current from the supply lines;

(2) a core of iron; (3) and a secondary coil or wire in which

is generated an electromotive force by the change of magnetism

in the core which it surrounds.

248. Fuse. — A fuse is a safety device intended to melt
when a current exceeding a certain strength passes through

202 APPLIED SCIENCE

a conductor. Thus the fuse protects the conductor from
being overheated by excess current. The fuse, which con-
sists of a piece of soft metal, such as an alloy of lead, is
soldered to copper terminals, so shaped that they may be
clamped.

249. Circuit- Breaker. — When a large volume of current
is used it is necessary to have a device known as a circuit-
breaker, as fuses are sometimes too slow in action. A circuit-
breaker is practically a switch, which, when the current
exceeds a certain amount, automatically opens by means of
the pressure of a spring regulated by a coil through which the
current passes. When the current becomes greater than a
certain amount, the coils attract an iron rod attached tc
a trigger and release it. This trigger comprises a spring
v/hich acts upon the switch. One current-breaker is used
for each generator.

Questions

1. What is the- commercial method of generating electricity?

2. What are the principal parts of a dynamo?

3. Explain the principle of a dynamo.

4. The strength of a current depends upon what factors?
6. What is an induced current?

6. How may the direction of an induced current be determined?

7. What is a commutator?

8. What are armature brushes?

9. Describe the action of a dynamo.

10. Name and describe the different kinds of dynamos.

11. What is the difference between alternating and direct cur-

rents?

12. What is an electric motor?

13. Describe the different kinds of electric motors.

14. Explain the expression "efficiency of a dynamo."

GENERATING ELECTRICITY COMMERCIALLY 203

15. Explain the care which, should be given to a dynamo.

16. What is a transformer? Describe it.

17. What is a fuse? Describe it.

18. What is a circuit-breaker? Describe it.

19. What is a resistance box? Rheostat? Starting box?

CHAPTER XVIII
TRANSMISSION OF ELECTRICAL ENERGY

250. Practical Uses of Electricity.-^-Mechanical energy
is transformed into electricity because in this form it can
be conducted very readily from a convenient place of genera-
tion or source of power, such as a waterfall, to any spot
within a reasonable distance and there be utilized as heat,
light, or power.

Electric heating is only practicable when it is desirable
to use heat for a short time at a certain point. In small
quantities electric heat is used in cookers, welding processes,
foot-warmers, cigar-lighters, etc. The advantage of this
form of heat is that it is free from fumes, odor, and noises;
its disadvantage is that it is too expensive for general heating.
Electricity, when consumed in large quantities in a special
electrical furnace, produces a very high temperature — ordi-
narily as high as 3500° C. — without difficulty, while in the
case of a furnace used for smelting metals by the burning of
coke under a forced draught, the temperature hardly ever
exceeds 2000° C.

The practical use of electricity gives employment to a
great many people. The various types of electrical work
include over two hundred occupations. Four types of
electrical work will be described in this chapter: (1) electrical
apparatus work; (2) inside wiring; (3) outside wiring; and
(4) power station work.

204

TRANSMISSION OF ELECTRICAL ENERGY 205

251. Electrical Apparatus. — Electrical apparatus work
includes the manufacture of all electrical machines, instru-
ments, and devices. This work is so varied and widely
differentiated that no brief description can cover it. In
general, however, it may be said to consist of the skilled elec-
trical work required in the manufacture or repair of all forms
of electrical apparatus, such as generators, motors, electric
meters, rheostats, telephones, switchboards, and testing and
signal apparatus.

252. Outside and Inside Wiring. — Outside wiring consists
of the installation of all outdoor lines, such as general elec-
trical power transmission lines, street lighting, telephone,
telegraph, and signal lines. There are two general types of
outside wiring: aerial, in which the wires or cables are
supported high in the air on poles or other suitable devices;
and underground, in which the wires or cables are laid in
conduits.

Inside wiring consists of the installation of electric wires,
appliances, and fixtures for all purposes within the confines
of some structure. It includes such work as lighting, heat-
ing, power, bell, telephone, and signal installation.

There are four general types of inside wiring: (1) open
work, in which the wires are exposed to view, and are mounted
on cleats or knobs; (2) molding work, in which the wires
are run in a special molding, made either of wood or metal;
(3) concealed work, in which the wires are run in partitions
and other places not exposed to view, and are insulated by
means of knobs and tubes; and (4) conduit and armored
cable work, in which the wires are run in metal pipes called
conduits or are protected by an integral metal coating or
armor. The above classification does not include all forms

206 APPLIED SCIENCE

of electrical work, as there are some specialized occupations,
such as power house work, which have been omitted.

253. Requirements of the Trade. — A very considerable
a nount of trade and technical knowledge is required by an
electrician. The following are some of the details upon
which an inside wireman must have ready and definite
knowledge: (1) the methods of installation of electric wires
and conduits; (2) the making of electrical connections
(fixture wiring); (3) the installation of electrical appliances;
(4) the testing of circuits; (5) the methods of computing
the sizes of wires; (6) connections and fuses required for
specific electrical currents; and (7) the methods of estimat-
ing the amount of current required for the specified work.
This work presupposes a thorough knowledge of the electrical
requirements of the trade as set up by experts, and called the
code, together with some knowledge of the theory of electri-
city, with emphasis on the definition of terms and electrical
measurements. Some knowledge of building construction
is also necessary.

Electric wiring demands careful insulation from all sur-
rounding material which might under any circumstances
become a conductor of electricity. This need for special care
in insulating has caused the establishment of definite and
fixed rules. It is important that these rules (the electrical
code) be understood and observed by the worker, since not
only his business integrity and reputation are affected by
poor or slipshod work, but the safety of property and even
the lives of many people are dependent upon the proper
installation of electric wires and appliances.

254. Switchboards. — The output from generators and
dynamos is regulated by means of switches on a switchboard

TRANSMISSION OF ELECTRICAL ENERGY 207

(Fig. 9) which ia divided into two sections: the machine
panels, and the feeder panels. The machine panels are
equipped with ammeters, with the switches necessary for
regulating, and with voltmeters for measuring the electrical

Fiq. 93.— A Switchboard.

energy generated. The feeder panels have similar instruments
for controlling the output of energy to the various circuits.
The operator in charge of the switchboard is able to tell by
a glance at these instruments the amount of work each,
machine is doing, and thereby to know when it is advisable
to throw out of or put into operation additional machines.
A rheostat is furnished for each generator so that the pres-

208 APPLIED SCIENCE

sure may be varied. Circuit-breakers or fuses to interrupt
any particular circuit through which an excessive current
may flow, are also included in the switchboard equipment.

A switchboard is always placed away from the wall or
ceiling to reduce the danger of communicating fire to adja-
cent combustible material. Conductors should be of soft
annealed copper, about 97% pure, and should be insulated
for their entire length by a vulcanized rubber compound
that adheres to the wire. Wires should be arranged to secure
distribution centers in easily accessible places so that cut-
outs and switches may be conveniently located. The load
should be divided as evenly as possible among all the branches,
and complicated and unnecessary wiring should be avoided.

255. Transmission of Electrical Current. — The electrical
current must be transmitted from the power plant to different
points of distribution in an economical manner; that is,
with very little loss of electricity, and at the same time in a
way that will reduce the danger to life to a minimum. The
problem is not serious when the generating plant is in the
same or an adjacent building, as in the case of a private
plant; but it is a serious problem in a central power plant
that supplies electricity over a large area.

The current is usually transmitted, as noted above, through
copper wire supported on steel poles or towers, or in under-
ground conduits. The wire used underneath the ground
must be insulated, while the wire used overhead may or
may not be insulated. Overhead wires should be separated
as far as possible so they will not swing together. Over long
distances, such as 15 to 20 miles or more, the energy is trans-
mitted as alternating current at from 11,000 to 22,000 volts.
If the central station is near the center of distribution, the

TRANSMISSION OF ELECTRICAL ENERGY 209

voltage is about 2200 volts, and is reduced by transformers
before it reaches the consumer.

Alternating current is usually generated at a medium volt-
age and then raised by step-up transformers for transmission
purposes. When the current of high voltage reaches the
substation, it is reduced by means of step-down transformers.
If necessary, the alternating current may be changed over
to direct current by means of a rotary converter.

Electrical energy must be furnished to meet the maximum
demand during any part of the day, even if this maximum
demand continues only for a short time. To avoid the
expense and large investment of an equipment big enough
to supply such a maximum, storage batteries are utilized to
store up current during the slack hours and distribute it
during the rush hours of the evening when many lights are
burning. In this way the equipment is kept evenly at work
throughout the day.

256. Measurement of Strength of Current. — Electricity
is distributed from the power station where the energy is
generated to the different points where it is to be utilized for
power or lighting. The amount of work done or " power"
consumed in transmitting electricity from the power station
to the point of consumption is found in the following manner:
Multiply the electromotive force, determined by the volt-
meter, and the strength of the current, determined by the
ammeter, and the time in seconds; the result is the power
consumed and is expressed in joules, the electrical unit of
energy. This formula may be written:

Energy = Pressure X quantity X time
Joules = Volts X amperes X seconds

210 APPLIED SCIENCE

Power is the rate of doing work and the electrical unit is
the number of joules per second. It is expressed as watts.

257. Size of Wire. — In distributing electricity there is,
as previously stated, more or less resistance to its passage
through wires. In overcoming this resistance heat is devel-
oped and energy is lost by the friction caused by the electric-
ity moving through the conductor. The resistance offered
to an electrical current depends upon the material through
which it passes, the length and sectional area of the circuit
wires, and the surrounding conditions.

To illustrate: If 900 ft. of a certain wire offers a resistance of 2
ohms, the resistance of 450 ft. of the same wire is 1 ohm. If the
diameter of the wire were one-half, the area would be one-quarter
and the resistance four times as great, or 4 ohms. This is often
expressed in mathematical language by stating: Resistance varies
directly as the length and inversely as the square of the diameter
of wire.

Since watts are the product of electromotive force and current,
the question of furnishing 15,000 watts to a certain point from a
power station might be settled by having either an electromotive
force of 1500 volts and a current of 10 amperes, or 150 volts and
100 amperes. The loss due to heat increases with the strength of
the current.

The size of wire necessary to transmit a given current is deter-
mined by the drop in voltage allowed between the generator and
the point of application of the current, and the increase in tempera-
ture due to the current.

High voltages are used in long-distance transmissions to increase
the carrying power of a given size of wire, in other words, to decrease
the cost of line necessary to transmit a given amount of energy.

268. Kilowatt and Kilowatt-Hour. — Many people con-
fuse kilowatt (kw.) and kilowatt-hour (kw.-hr.). Kilowatts
(watts divided by 1000) represent the number of units of

TRANSMISSION OF ELECTRICAL ENERGY 211

energy used at any one time. Kilowatt-hours mean the
amount of energy used oyer any given period of time.

To illustrate: Assume a motor of a different size makes an imme-
diate demand on the power plant of 1 kw. If the motor continues
running for two hours, the amount of electrical energy consumed is:

1X2=2 kw.-hrs.

That is, the motor demands 1 kw. and the consumption is 2 kw.-hrs.

259. Injuries in Electrical Work. — Injury in electrical
work is usually caused by direct contact with a live conductor
and may consist of either a shock, burns, or both.

When the electric current enters the body, it causes more
or less complete paralysis of the nervous system; this in turn
causes the heart and lungs to cease functioning. The degree
of the shock depends upon certain conditions. For example,
if an electric circuit is completed by making a contact with
the body at the shoulder and hand of the same arm, the
current will pass through the arm and not reach the heart
and lungs. On the other hand, if the circuit is completed
from hand to hand the current will pass through the body
near the heart and lungs and may be sufficient to cause death.
Sometimes the shock may not kill but stun the person to such
a point as to stop his breathing. This is due to the fact that
the skin of the body, unless wet, offers high resistance to
the current and the conductor makes only a short and in-
complete contact with the body. A person can be released
from a contact with a live conductor only by means of a
piece of dry, non-conducting material, such as a piece of
wood, a coat, rope, or hose. If possible, the switch should be
turned off or the wire should be cut by means of rubber
protected shears.

212 APPLIED SCIENCE

Burns are produced either from an arc or by the heating
of the tissues of the body by the current. In case burns
are produced it is very necessary not to touch or irritate
them. They should be protected from the air by a soft
dressing, such as carron oil (a mixture of limewater and
linseed oil), baking soda (teaspoonful to a pint of water),
or a paste of flour and water. A dry or charred wound should
never be covered by a liquid dressing, but simply with a
clean cloth.

Questions

1. Name some of the practical uses of electricity.

2. What are the possibilities and limitations of electrical heating?

3. Describe some of the principle lines of electrical work.

4. What is the difference between outside and inside wiring?

5. Describe the method of transmitting electricity over a long
distance.

6. How is the size of wire for transmitting electricity regulated?

7. What is the difference between the kilowatt and kilowatt-
hour?

8. What are some of the common injuries in electrical work?

CHAPTER XIX
THE TELEPHONE AND TELEGRAPH

260. History of Telephony. — Less than forty years ago
there were no telephones. Today there are more than
10,000,000 in use and they are found in every civilized coun-
try on the globe. The United States has more than 7,000,000
telephones. In New England alone there are over 1,000,000
miles of telephone wire, hundreds of central offices, and over
half a million telephones.

The telephone was invented by Alexander Graham Bell
in Boston in 1876. At first it was looked upon as a toy and
considered as of little value. So strong was this general
opinion that it was hard to get money to develop it. Today
the money invested in telephony runs into billions and the
telephone has proved one of the greatest inventions of all
time. It has made possible instant talk over a wire between
millions of people. One can talk from Boston to Chicago,
and even hundreds of miles farther, almost as easily as across
the street.

No business ever grew so rapidly. Although it was pos-
sible to talk over a crude telephone wire in 1876, it was not
until years later that the invention was really established on
a sound footing.

261. Telephone Principles. — Many people use the tele-
phone daily without having the slightest conception of the
principles upon which it operates. The fundamental principle

213

214 APPLIED SCIENCE

is a comparatively simple one, involving merely the carrying of
sound waves by means of an electric current, but in a large
city with thousands of telephones and many exchanges, the
problem of proper connection and transmission becomes a
complicated one.

The transmitting and receiving instruments are identical
in nature, each consisting of a coil of insulated wire con-
nected with the line.

In transmitting, the message is spoken into the mouth-
piece at one end. The to-and-fro motion thus imparted to
the metallic diaphragm attached to the mouthpiece produces
induction currents in the coil. These impulses passing
over the main line produce similar movements in the dia-
phragm of the receiving instrument and thus cause the latter
to reproduce the message in articulate sound to the one
listening.

262. Making a Connection. — In order to understand how
a call is made through a large city exchange, it is necessary
to have in mind a distinct picture of a switchboard and to
understand the functions of the various operators. (See
Fig. 94.) For the sake of clearness it will l>e well to take a
single typical case.

Between fifty and ninety subscribers' lines run to each
operator's switchboard. Operator A, for instance, receives
all the calls from the subscribers on the Audubon exchange
whose numbers are from 1 to 50. At the bottom of her
switchboard there is a hole, called an answering jack, for
each of these lines. Should one of these subscribers, Mr.
Smith, take his receiver from the hook in order to call, a
small supervisory lamp lights below the answering jack in
which Mr. Smith's line ends. Operator A is thus notified

THE TELEPHONE AND TELEGRAPH 215

that Mr. Smith is calling, and connects herself with his line
by inserting one of a pair of plugs in the answering jack.

The top of operator A's switchboard contains a hole for
every number on the Audubon exchange, and an additional

Fiq. 94.— Operating Room in a Small City Exchange.

one for a trunk line. (The operation of the trunk line will
be explained later.)

Should" Mr. Smith be calling Mr. Jones, whose line is also
on the Audubon exchange, the operator can make the con-
nection directly by inserting the other plug of the pair at

216 APPLIED SCIENCE

the top of the switchboard into the hole which marks the
termination of Mr. Jones' line and which may be distin-
guished by the number it bears.

Operator A can be called only by those subscribers on the
Audubon exchange whose numbers are from 1 to 50. She can,
however, call directly any of the subscribers on the Audubon
exchange.

Suppose, on the other hand, that Mr. Smith is calling
Mr. Harper, whose line is on the Rector exchange. In this
case, it is necessary for operator A to use the trunk line in
order to make the connection. The trunk line is the line
which connects the various exchanges with one another, and
has nothing to do with the subscriber directly.

Operator A, in this case, inserts the second plug of the
pair in the trunk line hole, the first plug being in the answer-
ing jack of Mr. Smith's line. Thus the trunk line operator
is called. Operator A gives her Mr. Harper's Rector ex-
change number, and she then connects operator A with one
of the Rector exchange operators. It does not matter which
Rector operator is given, the call, for just as operator A can
call any subscriber on the Audubon exchange, so can any
Rector operator call any subscriber on the Rector exchange.

In this case it may be assumed that the trunk line operator
knows that operator B on the Rector exchange is the least
busy and, consequently, gives her the call. Operator B
then " plugs in" Mr. Harper's number at the top of her
board and thus through operator A, the trunk line operator,
and operator B, Mr. Smith on the Audubon exchange is
connected with Mr. Harper on the Rector exchange. In
very large cities there may be an operator for each exchange
who merely receives calls from the trunk line operator and
apportions them to the operators on her exchange. In such

THE TELEPHONE AND TELEGRAPH 217

case, the trunk line operator would call this apportioning
operator instead of calling operator B directly.

263. The Supervising Lamps. — There is, on the operator's
switchboard, a supervising lamp associated with the calling
plug as well as with the receiving plug. When a subscriber
calls the operator, the supervising lamp under the receiving
plug lights, as before noted. When the operator " plugs in"
and connects herself with the calling subscriber, that lamp
is extinguished. When she "plugs in" at the calling hole,
the second supervising lamp lights, and remains lighted until
the party called answers. So long as these two lights are
extinguished, the operator knows that the subscribers are
using the line. When the subscribers replace their receivers
on the hooks, the lamps relight.

264. The Listening Cam. — The listening cam is a small
key on the switchboard by means of which the operator puts
herself in connection with a subscriber after having " plugged
in" at his answering jack. After connecting two subscribers
the operator closes her listening key and thus shuts herself
off from their conversation. Were it not for this device,
every conversation would, perforce, pass through the opera-
tor's ears.

266. Cables and Distributing Frames. — Wires enter and
leave the telephone exchange building in the form of cables
(Fig. 95). A cable is composed of pairs of twisted copper
wires, insulated with spiral wrapping and enclosed in a lead
casing.

Within the exchange these cables are supported by two
frames; the main distributing frame and the intermediate

APPLIED SCIENCE

distributing frame (Fig. 96). The main distributing frame
allows the entering wires of the subscribers' lines to be changed

without changing the telephone number. The intermediate
distributing frame is so constructed as to permit anj call
to be answered at any portion of the switchboard. Thus no
individual operator need be overloaded with calls.

THE TELEPHONE AND TELEGRAPH 219

266. Construction Work. — The work of telephone com-
pany construction crews is almost entirely outdoors. The
linemen work in gangs under a foreman, and generally not
far from their homes. During the summer, however, they
travel about putting up through lines of poles and trunk

wires. If the men cannot find accommodations in some
house during such times, they camp out. After a great
storm, linemen are called from every section with all possible
speed to repair any damage which may have been done.

A large number of men are employed in central office
repair work, testing the wires, installing telephones in houses
and offices, and making inspections.

220 APPLIED SCIENCE

267. The Story of the Telegraph.— Samuel F. B. Morse,
an American inventor, holds the most important place in the
development of the telegraph. Although Wheatstone and
Cooke in England occupied a distinct place in this field, the
telegraph system invented by Morse in 1837 is the one that
is almost universally used, except for railroad work, to which
the needle instruments of the Englishmen are peculiarly
adapted.

Morse was assisted in the practical and mechanical devel-
opment of the telegraph by Alfred Vail, an uncle of Theodore
N. Vail of more recent telephone and telegraph fame. It
was, moreover, through the financial assistance of Alfred
VaiPs father that Morse was able to put up the first experi-
mental line. The telegraph today, in connection with the
cable which was perfected some time later, reaches practi-
cally every civilized portion of the world, gives employment
to thousands of men and women, and renders service to
millions of others.

268. Parts of Telegraph. — The telegraph is an instrument
used to send messages to a distance by means of electricity.
It is usually worked by electrical current or by an electro-
magnet. The instrument is made up of four separate parts:

(1) the generator, or battery to generate the electricity;

(2) the conductor, or insulated wires by which the electric
current is carried to any distance; (3) the transmitter, or
instrument which regu'ates the flow of electricity; and (4)
the register, which records the signals. The generator is
made up of one or more voltaic batteries, each of which is
composed of a number of cells connected in a series. The
Grove cell was formerly much used and then the Daniell
cell; but a cell called the gravity cell, which is as good as

THE TELEPHONE AND TELEGRAPH

221

either of these two and a great deal cheaper, is now commonly
employed. To send a message a long distance a stronger
battery is needed than to send one a short distance. A battery
can be made stronger by adding more cups or cells to it.

269. Steps in Telegraphing. — To telegraph from one
place to another it is necessary to stretch between the two
places a wire, over which the electric current may flow. Iron
wire is generally used, oecause it is stronger and cheaper

Fig. 97. — A Telegraph System.

than copper wire. In the United States, wires are usually
stretched upon high poles. As the electricity would run down
the poles to the earth if the wire touched them, the wire is
fastened to a glass knob. Glass being a non-conductor, the
electricity is thus insulated and flows freely between the
places connected by the wire.

Figure 97 shows the actual arrangements of. a telegraphic
system. If the operator at one end of the line desires to send
a message he opens the switch connected to his key, which is
always kept closed except when sending a message. He then
begins to operate his key. Every time he touches his key he
closes the circuit and the electricity flows through the line

222 APPLIED SCIENCE

causing his own sounder and the one at the other end to click.
Because of the great resistance to the current, the electricity
by the time it reaches the end of the line is so feeble that
it is necessary to place in the local circuit a battery and a
second electromagnet, called a sounder. On the main line
there is another electromagnet, called a relay. This has a
greater resistance, due to its fine wire, than the sounder,
which has a small resistance.

When the telegraph operator at one end of the line presses
on the key so as to close the circuit, the magnets at the other
end of the line become magnetic, the end of the lever is
attracted and drawn down by the magnets, the other end
is pushed up and the steel point presses against the paper
and dents a line in it. This line is made so long as the key
is kept pressed down in the sending office.

As soon, however, as the sending operator takes his fingers
from the key, the circuit is broken. The magnets in the
register at the receiving station then lose their power on the
lever, the end drops down, and a blank space is left on
the paper. When the operator in the sending station taps
on the key so as to close the circuit only for an instant, a dot
or very short line is made on the paper in the receiving station
as shown on the table below. By pressing on the key a little
longer time, or not at all, the operator can make dots, lines,
or blank spaces on the paper in the receiving station. By
putting together these lines and dots in different ways all
the letters of the alphabet may be made, so that any kind
of a message may be sent.

The alphabetical application of the dot-and-dash code
invented by Morse was made in 1837 by Alfred Vail, though
it is universally known as the Morse alphabet. This alpha-
bet, which is used in the United States and Canada, and in

THE TELEPHONE AND TELEGRAPH

223

a modified form all over the Continent of Europe, is made
up wholly cf dots and lines, the letters most used having the
simplest symbols.

a
b
c
d
e
f

g
h

J
k

Morse Alphabet

m —

American

- -

_ _ — _

- -

- - -

•

- - _ -

International

n —

o —

P -"

-— q —

r —

t —

V - -

w - -

— x —

y —

z —

Morsk Numerals

2 -- —

3 ----
4

Period,

Comma, --
Interrogation,
Exclamation,

Colon,

Semicolon, -
&,

7
8
9

1
2
3
4

6
7

8
9

Morse Punctuation, etc.

224 APPLIED SCIENCE

Questions

1. How long has the telephone been used?

2. Who invented the telephone?

3. Explain the principle on which the telephone is based.

4. Describe the steps in telephoning.

5. Describe the construction of a switchboard.

6. Who invented the telegraph?

7. Describe a telegraph instrument.

8. Describe a telegraph system.

9. Explain the steps in telegraphing.

10. State some of the advantages of the telephone and telegraph.

CHAPTER XX

SCIENCE UNDERLYING MECHANICAL DRAWING

SUPPLIES

270. Mechanical Drawing — Supplies Required. — Me-
chanical drawing plays a large part in directing the perform-
ance of all industrial operations. It is the guiding hand, so to
speak, which directs the erector in the shipyard, the machinist
in the shop, and the builder of bridges at the river. Therefore,
a knowledge of the principles of science underlying its applica-
tion is as important as a knowledge of the science of the trade.

In making a mechanical drawing, certain supplies are
necessary. The first requisite is a pencil, properly made;
the second, a paper of suitable quality for the work in hand;
and the third, an eraser of just the right degree of hardness.
With these simple yet important tools, together with a
compass and ruler, the draftsman makes his working draw-
ing. The tracing of the pencil-made drawing is the next
step in the process. For the purpose of tracing, tracing
cloth and paper are necessary, as well as a special kind of
ink, called India ink. After a tracing has been completed,
the making of the blue-print comprises the final step. A
blue-print is used because if it is lost, another one can easily
be made, whereas an original drawing can be made only at
the cost of much time and money.

271. The Lead Pencil. — A lead pencil consists of a stick
of graphite in the center of a cylindrical piece of red cedar

is 225

226 APPLIED SCIENCE

wood. This particular type of wood is selected because it
can be cut easily and smoothly with a penknife. The eas3
with which it can be cut is due to the closeness of its grain
and the softness and tenderness of its fiber. The graphite
used in lead pencils is of the highest grade. It is mined in
Ceylon and Mexico and comes from the earth in the form of
large, crude stones.

This crude graphite is crushed to a powder in a large roll-
ing machine. A smooth clay, called a binding agent, is
added to the graphite to hold the particles together. The
ratio of the clay to the graphite determines the hardness of
the "lead" in the pencil; increasing the proportion of clay
makes the pencil harder. The mixture is washed to remove
all particles of grit and other impurities.

To make the pencil rods, or " leads," the mixture of graphite
and clay is placed in the bottom of a steel cylinder which
contains dies of the proper gauge for the thickness of the
"lead." Under enormous pressure the mixture is forced
through the dies and emerges like a cylindrical shoe-string
at the rate of 170 ft. per minute. This cylindrical string is
straightened and dried, cut to pencil lengths, and placed in a
crucible to harden. The heat toughens and gives the proper
temper to the rods.

Six pencils are made at one time. The red cedar wood,
already mentioned, is cut into slats. Each slat is slightly
longer than a pencil, slightly thicker than half a pencil, and
as wide as six pencils. The slat is well seasoned — kiln-dried .
— and passed through a planing and cutting machine. This
machine planes the surface of the slat smooth and cuts in it
six lengthwise grooves. Into each of these grooves a piece
of lead is inserted by hand . Then another slat, similarly
grooved and planed, is fitted over the slat into which the

MECHANICAL DRAWING SUPPLIES 227

lead has been placed. This second slat is coated with glue
before being fitted over the lead, so that the two slats hold
fast after being brought together. After the glue has se^
thoroughly, the slats are fed lengthwise into another machine
which separates their six parts into six pencils.

Since there is a demand for pencils of every grade, from the
soft pencil of the news editor to the hard pencil of the drafts-
man, pencils are made in sixteen grades of hardness. These
grades vary widely enough to meet every demand.

272. Drawing Paper. — Paper is a fabric or kind of cloth
composed of numerous fibers or threadlike filaments, the
rough edges of which cause them to stick together. Draw-
ing paper and other fine grades of paper are made from linen
rags. The first step in the process of manufacture is to
place the rags in a vat filled with water and to beat and
tear them until they are transformed into paper pulp, a
substance which looks very much like cottage cheese. The
pulp is then taken to another vat where it is mixed and
churned with more water until in its more diluted form it
becomes of the thickness or consistency of cream. This
creamlike substance is then allowed to flow over the screen
of the paper machine on which it is transformed inio long
rolls or sheets of paper.

The paper machine consists of a fine screen of wire about
6 ft. wide and 200 or more feet long. The screen runs over
rollers on the principle of an endless belt. The creamlike
pulp is allowed to flow on one end of the traveling screen
which vibrates as it moves along. The water in the pulp
gradually drains through the screen on which the fibers settle
evenly in the form of a porous sheet, like very spongy blot-
ting paper. As the screen travels along it passes between

228 APPLIED SCIENCE

rollers which compress and squeeze out more of the water
from the creamy substance, making the sheet of paper less
spongy. After the pulp has been pressed into a sheet, the
screen passes over hot rollers for the purpose of drying the
wet sheet of paper. The distance which the paper pulp
travels on the screen before it is transformed into paper
is 100 ft. or more. The thickness of the paper depends
upon the rate at which the pulp is allowed to flow on the
traveling screen. "Hot pressed" paper is paper to which
the extreme pressure is applied while the pulp is still hot,
while "cold pressed" paper is not subjected to pressure
until the pulp is cold. The former type of paper is of the
highest grade.

273. Rubber Erasers. — Rubber erasers are used exten-
sively in drawing to remove pencil and ink marks. They
are made of rubber combined
with sufficient sulphur to
give the proper hardness.
Other materials are added in
varying proportions to give
different degrees of softness
and suppleness. It is by
these qualities that the dif-
ferent grades of erasers arc
distinguished.

The process of obtaining
the rubber used for erasers,

Fio. 98,-TappiDg Rubber TW and for maD y ° ther P"rpOBeS

as well, is a most interesting

one. Rubber is obtained f roui the sap of certain tropical trees.

A series of slanting cuts made in the bark allows the sap to

MECHANICAL DRAWING SUPPLIES 229

run out (Fig. 98). A cup is hung at the bottom of the tree
and gradually the milky sap runs into it. The contents of
a number of these cups are then poured into a large vessel.
A wooden paddle is dipped into
the sap and when withdrawn
is held over a fire made from
palm nuts. The heat from the
thick smoke hardens the sap.
This process is repeated many
times until a ball, called a bis-

cuit (Fig. 99), is formed. The »"• »--R»M»r Bi™it.
paddle is then withdrawn from the biscuit and the biscuit
is ready for market. After coming to the market as balls
or biscuits, the rubber is purified and made into sheets.
Because of its softness and sticky nature, this crude rubber
is useless for erasing and consequently must be subjected to
a hardening process called vulcanization. This process
consists in subjecting the rubber to supreme heat. After
being vulcanized the rubber is suitable for erasers and other
commercial products.

274. The Working Drawing. — The drawing from which
the blue-print is made is called a working drawing. The
method of preparing it is simple. The draftsman merely
looks squarely at the object and draws the outline of it.
By changing the point of view, different views of the object
may be obtained. The views usually drawn are of the front,
top, and side. To show the interior, additional views may
be drawn of the object in section.

The front view of an object is the view obtained by looking
squarely at it from the front. This view is often called the
elevation. The top view is the view obtained by looking

230 APPLIED SCIENCE

squarely at the object from the top. This view is often
called the plan. The side view is the view obtained by
looking squarely at the object from the end. This view is
often called the profile view or the end elevation.

275. Distinction between Working and Perspective
Drawings. — A perspective drawing is one that portrays
an object as it appears to the eye from one point of view.
The rails of a car-track, for instance, appear to converge.
The parallel lines of any object appear to the eye to converge
in like manner, and a perspective drawing will show this
feature. Any picture or photograph furnishes an example
of the perspective drawing.

The working drawing, on the other hand, is designed not
to present a picture, as is the perspective drawing, but to
indicate all the various parts of the object together with their
dimensions. In other words, a working drawing is really
three distinct drawings of the same object, each of which
is drawn from a different point of view. A working drawing
of a cube, for instance, would comprise three drawings exactly
alike, because a cube presents the same appearance whether
viewed from the front, top, or side. A working drawing of a
book, on the other hand, would present drawings of three
rectangles, each of which would have different dimensions.

This distinction between a perspective and a working draw-
ing is an important one, but once made clear, is very simple.
A perspective drawing is the result of what the eye sees,
while a working drawing is the result of what the ruler and
compass tell.

276. Tracing Cloth. — Tracing cloth consists of muslin
cloth heavily sized and pressed to make it translucent and

MECHANICAL DRAWING SUPPLIES 231

smooth. There is some oil in the sizing preparation, and
consequently before the cloth is used, whiting or chalk is
rubbed into it to absorb the oil.

277. Tracing Paper. — Tracing paper is made from tissue
paper of an even texture, and possesses long and strong
fibers. This tissue paper is treated with oil and solutions
of resins and varnishes.

278. India Ink. — India or Chinese ink is always used in
making the tracing of a mechanical drawing, because of its
permanence, its distinct blackness, and because it is water-
proof. Moreover, India ink, because of its heavy composi-
tion, is less liable to "spread" and cause a blot. It is a
mechanical mixture of pure, dense lampblack and a solution
of gelatin, gum, or agar-agar. (Agar-agar is a gelatinous
substance obtained from seaweed.) This mixture forms a
black paste which is dried and pressed into cakes. It
was formerly the custom to use it in this form, but at the
present time it is easily obtainable in the liquid form ready
for use.

Should the draftsman, however, buy India ink in the cake
form, he can easily prepare it for use by shaving off a portion
of the cake into water and stirring the mixture thoroughly.

279. The Blue-Print. — When a mechanic in the shop
receives a working drawing, it is in the form of a blue-print,
a blue paper on which the lines of the drawing appear in
white.

A specially prepared paper, known as blue-print paper,
is used for making blue-prints. This paper is prepared by
the application of a chemical solution of red prussiate of

232 APPLIED SCIENCE

potash, water, citrate of iron, and ammonia. The solution
is applied with a camel's-hair brush and is then allowed
to dry. After drying, the paper assumes a greenish yellow
color.

The blue-print itself is made in the following manner.
The tracing of the drawing is placed over a piece of blue-print
paper. The two are then put into a frame constructed simi-
larly to an ordinary picture frame. The frame is then exposed
to the direct sunlight. The rays of the sun pass through
every portion of the tracing paper except the black lines
of the drawing, and act upon the chemical solution of the
blue-print paper in such a way as to turn to a yellow color
the entire paper, with the exception of that portion beneath
the black lines. The blue-print paper is then dipped into
water, which changes it, with the exception of the lines, to
a blue color. The lines become white and are, of course,
an exact reproduction of the tracing.

Questions

1. Describe the composition and manufacture of a lead pencil

2. What constitutes a good grade of drawing paper?

3. Explain the composition of an eraser. What qualities must
an eraser possess?

4. How is rubber obtained and refined?

5. What is a working drawing?

6. What is the difference between a working drawing and a
perspective drawing?

7. What is tracing cloth?

8. What is tracing paper?

9. Describe the composition of India ink. Why is it used for
drafting purposes?

10. What is a blue-print? How is it made?

CHAPTER XXI
STRENGTH OF MATERIALS

280. Need of Knowledge of Strength of Materials. —

Mechanics are often called upon to determine the size of
rod or beam required to support a certain weight or force.
Not all pieces of material have the same strength. The
strength of any piece of material depends upon the nature
of the material (cohesion of the particles composing it) and
upon the position, shape, and bulk of the piece. Therefore,
it is absolutely necessary to know something about the
properties and laws governing the strength of materials
used in industry. When a force acts on beams, structures,
or bodies of any kind, it may be considered as weight, and
may be measured in pounds.

281. The Effects of a Load of Force on a Body. — When
a body is supporting a load, a force is acting on it. This
force will produce a change, perhaps not very noticeable,
in the form of the body. Unless this load is so great as to
cause a break or fracture, the elasticity, which has previ-
ously been defined as the tendency of the particles of a body
to unite, or return to their original positions, will support
the load. The forces of the body resisting the pull or pressure
of the had are called stresses. The change of shape of the body
producing these stresses is called a strain. To illustrate: The
molecules of a piece of iron are held together by the force
of cohesion, which is stronger in iron than in some other

233

234 APPLIED SCIENCE

bodies. This force must be overcome in order to change the
condition, form, or size of the iron bar, or to break it into
parts. When the iron bar is supporting a load, the resistance
which the bar offers to the pressure or pull of the load that
tends to overcome the force of cohesion is called a stress. If the
load is not very great, the particles of iron may be separated
while the iron is supporting the load, but they will return
to their original position as soon as the load is removed.

The elasticity of different substances varies. The degree
of elasticity of the various materials is found by measuring
the forces required to produce equal changes in four pieces
of the same material of like dimensions. In case the load
is very great and the particles of iron are separated to such
an extent as not to return to their original positions when
the load is removed, the structure of the iron is more or less
broken down. This is very clearly shown by the change in
appearance of polished surfaces of a metal in a stressed condi-
tion. The bright surface suddenly becomes dull when the
stress exceeds the amount which affects the permanent struc-
ture. Another example of stress is seen when a large casting
is lifted by a crane or derrick. The chains supporting the
casting are then said to be " in stress" or "stressed."

282. Different Kinds of Stresses. — Stresses may be di-
vided into the following five classes according to the action
of the force producing them:

(a) Tension (pulling stress) usually called tensile stress.

(6) Compression (crushing stress) usually called compres-
sive stress.

(d) Torsion (twisting stress).

(e) Flexure (bending stress).

STRENGTH OF MATERIALS 235

Tension, or pulling stress, is the force that overcomes external
forces that tend to stretch a body. A rope or wire sup-
porting a load is an example of tensile stress. The rope
or wire is subjected to a tensile stress of the weight of
the load.

Compression, or crushing stress, is produced when external
forms act so as to compress a volume or any supporting body.
When an engine rests upon rails, the rails are subjected to
the compressive stress of the weight of the engine.

Shearing, or cutting stress, is produced when forces tend
to cause the particles of one section to slide over the section of
an adjacent body. When a bolt is in tension the head of the
bolt is subjected to a shearing stress tending to strip the
head from the shank of the bolt.

Torsion, or twisting stress, is produced when forces tend
to twist. A rotating shaft is obliged to resist a twisting force.

Flexure, or bending stress, is produced when forces tend to
bend. A floor timber in a house has to resist the bending
force that tends to break it.

283. The Effect of Strains. — Since a strain is the length-
ening due to the action of a stress it is measured in fractions
or decimals of an inch.

To illustrate: If a bar of steel, such as a piston rod, has been
stretched or lengthened ^ f in. by the stress caused by the weight
of the driving box, the strain in the steel rod is J* in.

If a weight is hung from a beam resting on two supports A and B
as in Fig. 100, the beam is a lever of the second class. If we consider
the pressure on the support A as the power and the pressure on the
support B as the fulcrum, we can easily find the power if we know
the weight. Then knowing the power, we can find the pressure on
support B, provided we know the distance of the weight from

236

APPLIED SCIENCE

/viawn

WUGHT

one end and the distance between the supports. It makes a
difference which support we consider to be the fulcrum.

If the weight were hung

U— 6Fi^* /8 ft H from the center of the beam,

it is plain that each support
would carry one-half of the
load. But if, as shown in
the figure, the weight is
hung a distance equal to
one-fourth the length of the
beam from A , the support A
will bear three-fourths of the
weight and the support B
will bear one-fourth.

- 24Ft

Fig. 100.

Example. — Suppose instead of one weight, we had two weights
hanging on a 1000-lb. steel beam as shown in Fig. 101. What will
be the pressure or weight on supports A and Bf Consider one end
of the beam, A, as the fulcrum. Then the moment of the 6-ton
weight will be: 6 X 6 or 36, , ^ ^ ,

6ft

liwrn f ^ ^■n-t/v/.s

fsn

and the moment of the 9-ton
weight will be: 9 X 12 or
108. The moment of W.
the weight supported at B,
will be 18 X IF. Then
since the sum of the mo-
ments of the weights will be
equal to the moment of the
weight supported at B, we
will have: 36 + 108 = 18
X W, or W - 8 tons, for

the weight supported at B. But the beam itself weighs 1000 lbs.,
one-half of which is supported at A and the other half at B. Adding
this to W makes 8 tons plus \i ton, or 8J4 tons for the total weight
supported at B. The weight supported at A will, of course, be the
amount left after subtracting the weight at B from the total weight:

6 tons + 9 tons + Y^ ton - 15)^ tons, total weight
and \h x /z tons - 8J£ tons = 7J£ tons, the weight supported at A

Fig. 101.

STRENGTH OF MATERIALS 237

284. Bending Force. — When a beam is bent, the forces
at any point tend to pull the fibers apart in the upper part
and push them together in the lower part, while the portion
between the two is subject to less stress. The nearer the
center the force acts, the less becomes the stress, until fi-
nally the beam or neutral axis is reached. At this point the
bending stress is zero. Accordingly structural steel beams
are made with flanges (reinforcements) at the top and bot-
tom to take care of the bending stresses. These flanges are
connected by a plate called a web. The material of the web is
subject to a shearing stress — the maximum of which occurs
at the support and the minimum where the bending is greatest.

Wood offers the greatest resistance when placed in an
upright position. A short post is stronger than a long one
of the same section, since the stress in the short post is due
merely to compression, while in the long post there is apt
to be bending. By applying a stay or projection to the
part about to bend, firmness may be given to the support.

A fluted column offers a greater resistance to a bending
force than a smooth one; therefore it is stronger. When a
beam is supported at both ends, it is twice as strong as one-
half its length supported only at one end. Of two beams with
the same cross-section area, the longer beam is the weaker.

286. Measurement of Stresses. — Stresses are measured
in pounds per square inch.

For example, if we have a bar in tension there is a stress distrib-
uted equally all over its cross-section. In other words, if the bar
is 1 in. square, each particle of that square inch will bear the same
stress or load. If a bar is 2 in. square then its area is 4 sq. in. and
each inch of this area has an equal load or stress acting upon it.
The pounds of stress per square inch on a piece in tension or com-
pression is called the unit stress.

238 APPLIED SCIENCE

If a bar of 4 sq. in. cross-section is under a total pull of 36,000
lbs., the unit stress is then one-fourth of 36,000 lbs., or 9000 lbs.
per square inch.

When a piece is stressed beyond the elastic limit and
consequently breaks, we say that it has been stressed to its
ultimate strength. The ultimate strength or breaking stress
is a unit stress and is always given in pounds per square inch.
The ultimate strength is that unit stress which is found just
before rupture and is the greatest unit stress the piece will bear.

Suppose we find, by testing, that a bar of wrought iron 2 in. square
breaks under a tension of 240,000 lbs. What is its ultimate strength?
Since the sectional area is 4 sq. in. and the total stress which it took
to break the bar was 240,000 lbs., the stress per unit of area will
be 240,000 -*■ 4, or 6000 lbs., the ultimate strength.

286. The Stress of Elongation. — Ultimate strength and
the unit of ultimate elongation are closely related. The ulti-
mate elongation is a strain produced in a unit of length by a
stress equal to the ultimate strength of the material. In other
words, the elongation of a test piece 1 in. long just at
the point of rupture is its ultimate elongation. A rule for
finding the ultimate elongation is: Divide the total elongation
of the piece at rupture by the original length.

In making tests of materials, it is often well to record
the percentage of elongation. This is nothing more than
the ultimate elongation expressed in per cent.

Suppose we find that a 50-in. rod elongates Yi in. under a certain
load. The unit of ultimate elongation will then be J^ s- 50 or
T <J 7r in. The per cent of elongation will be jfo in. expressed
in per cent. If the ultimate elongation is expressed as a decimal
the same rule will hold; that is, simply multiply the decimal by 100
and call the answer per cent. For example, if an ultimate elonga-
tion figures .025 in., multiplying this by 100 will give us 2.5%.

STRENGTH OP MATERIALS 239

In figuring the ultimate elongation of a test piece broken
in the machine, it does not matter what the sectional area
of the piece is. All we need to know is the increase in length
over the original length. This increase should be divided
by the original length. The quotient will be the ultimate
elongation of the tested piece.

287. The Stress of Compression. — Compression is one
of the most common of all stresses and everywhere things
are seen undergoing compression. The foundation walls
of the shop, the legs of the table, the foundation of the lathe,
the shaper, the drill press, or the planer, the posts or columns
that support the shop roof — are all in compression.

If the length of a piece is not more than five times its
least transverse dimension, the laws of compression are simi-
lar to those of tension, and the strain is proportional to the
stress until the elastic limit has been reached. Upon reach-
ing the elastic limit, the strain increases more rapidly than
the stress, as in the case of tension.

288. Testing Laws Applicable to Materials. — Repeated
experiments with materials in testing machines and in prac-
tice have proved that there are certain laws which always
hold true. These laws may be enumerated as follows:

I. When a body is subjected to a small stress a small
strain is produced. When the stress is removed the body
springs back to its original shape.

II. Within certain limits the change of shape, or strain,
is directly proportional to the stress producing it. This is
the same as saying that when a tensile force is gradually
applied to a bar it elongates the bar and that up to a cer-
tain limit this elongation is proportional to the force.

240 APPLIED SCIENCE

For example, if we take a bar of wrought iron 1 sq. in. in section
and subject it to a tension of 5000 lbs., it will be found to elongate
.02 in. ; if a tension of 10,000 lbs. be applied the elongation will be
.04 in.; if a tension 15,000 lbs. be applied it will be .06 in.; for a
tension of 20,000 lbs., .08 in., and for a tension 25,000 lbs., 10 in.
When, however, the next 5000 lbs. is added, making a total stress
of 30,000 lbs., it will be found that the total elongation is .14 in.,
which shows that the elongation is increasing more rapidly than
the stress.

The point at which the elongation begins to increase more
rapidly than the stress is called the elastic limit

III. When the stress is sufficiently great a strain is pro-
duced which is partly permanent; that is, the body does
not spring back entirely to its original shape when the stress
is removed. This lasting part of the strain is called a set,
and when a body is strained sufficiently to give it a permanent
set it is said to be strained beyond its elastic limit.

IV. When a still greater stress is applied to a body after
the elastic limit is reached, the strain rapidly increases and
the body is finally ruptured or broken. Many materials,
such as iron and steel, after the elastic limit is reached, act
very much like molasses candy. When pulled they stretch
and draw down thinner and thinner until finally they break
apart. The machine designer must remember that the
stress should never exceed the elastic limit of the material,
because when a bar is thus stressed it is very unsafe and is
likely to break.

V. A force acting suddenly, such as a sledge hammer blow,
is called a shock and causes greater injury than the same
force gradually applied, because of the velocity or speed of
the blow and the effect of its sudden application. Familiar
examples of steel subjected to repeated stresses and shock

STRENGTH OF MATERIALS 241

are found in the piston and connecting rods of a locomotive.
These parts are always made heavier than would be necessary
if they were to remain stationary.

289. Tables of Strength of Materials.— The first thing
to know in determining the size of beam or timber is the
weight or force load the
timber is to support and
the location of the load.

Very careful experi-
ments have been made in
testing laboratories (Fig.
102) to determine the
tensile or pulling strength
of materials under differ-
ent conditions. The re- _

,, ... . Fio. 102.— Testing Machine.

suits of these experiments

have been compiled and published in tabular form, as shown

below. Mechanics and contractors can find the strength of

any material of any size by looking in the table.

Average Tensile Strength of Materials in Pounds per
Square Inch

Antimony 1053 Gun-metal 32000

Aluminum: Castings 16000 Phosphor 40000

Sheet 24000 Manganese 62720

Bars 28000 " Tobin 78500

Brass: Yellow 26880 Copper: Cast 22400

Bronze: Cast: Lunken- Sheet 30240

heimer 34000 Wire 40000

Delta metal: Cast Steel: Lunken-

Cast 44800 heimer 80000

Rolled 67200 Gold 20384

242 APPLIED SCIENCE

Average Tensile Strength op Materials in Pounds per

Square Inch — Continued

lron:Cast:.' 18000 Silver: Cast 40000

Lunkenheimer 25000 Steel: Cast 60000 to 80000

Wrought 45000 Forgings. .60000 to 95000

Lead: Cast 1800 Tin: Cast 3360

Rolled Sheet 3320 Zinc: Cast 3360

Platinum Wire 53000 Sheet 15680

"Puddled" Semisteel:
Lunkenheimer 35000 to 42000

Woods

Ash 11000 to 17000 Locust 20500 to 24800

Beech 11500 to 18000 Maple 10500 to 10584

Cedar 10300 to 11400 Oak: White 10253 to 19500

Chestnut 10500 Pine: White .... 10000 to 12000

Elm 13000 to 13489 Pine: Yellow. . . . 12600 to 19200

Hemlock 8700 Spruce 10000 to 19500

Hickory 12800 to 18000 Walnut : Black . 9286 to 16000

In designing a piece of machinery, the first thing to find
out is the strength of the metal or material of which it is
to be made. The technical meaning of "strength" is the
power of a body to resist force and in mechanics the word
" body " means any solid object. The* word " force " means a
push, a pull, a twist, or a cut.

290. Weight of Metals per Cubic Inch. — It is often ne-
cessary in designing a machine to know the weight of its
parts, and any good engineer's handbook will give the weights
per cubic inch of all the metals. Not all kinds of iron weigh
exactly the same, since different processes of manufacture
use different amounts of the materials of which it is made.
The same thing is true of all metals, so only the approximate
weight is given in the following table which shows some of

STRENGTH OF MATERIALS 243

the metals used in construction and their approximate weights
per cubic inch.

Metal Wt. per Cu. In.

Cast Iron 260

Wrought Iron 281

Steel 282

Copper 317

Brass and Bronze 307

Lead 409

Tin 263

Aluminum 096

291. Factors of Safety. — In building a machine or a
structure of any kind, care must be taken not to subject any
part to a stress that would strain it beyond its elastic limit.
The usual practice is to divide the ultimate strength of the
material by some number depending upon the kind and
quality of material and upon the nature of the stress. This
quotient is called the factor of safety. The factor of safety of
any material is the ratio of its ultimate strength to the actual
stress to which it is to be subjected.

Suppose the actual tensile stress on a rod 1 in. square is to be
10,000 lbs., and we have found by testing that the ultimate tensile
strength of a material of this kind is 70,000 lbs. Then the factor
of safety for this material would be

70,000

10,000

= 7

The rod when stressed 10,000 lbs. will then have a factor of safety
of 7.

As has been stated, a force acting suddenly is called a
shock and does more damage than the same force gradually

244 APPLIED SCIENCE

applied. This rapidly applied force has been found by tests
to be about twice as much as the slowly applied one. There-
fore, in designing machinery it is necessary to consider
whether the part will be subjected to a steady stress, a
varying stress, or a shock, before deciding the proper factor
of safety to use.

The table below gives the factors of safety generally used
in American practice:

Material

Steady
Stress

Varying
Stress

Sho

Timber

Brick or Stone

Cast Iron

15
30
15

Wrought Iron

Steel

292. Strength of Chains. — Chains for hoisting weights
are made from a good grade of wrought iron, which has a
tensile strength of from 40,000 to 48,000 lbs. per square inch.
Chains used for raising weights should never be made from
steel, as it is not so strong under shock as wrought iron, and
does not weld so readily. Because of the possibility of the
weld not being as strong as the balance of the link, the
strength of the chain is not reckoned as twice the strength
of the bar from which it is made. When buying chains in
the open market it is advisable to base the computation of
strength on the lowest tensile strength of iron used for the
purpose, i.e., 40,000 lbs. to the square inch.

The strength of a chain link is 1.63 times the strength of
the bar from which it is made. The strength referred to is
the breaking, or tensile, strength. It is never safe to strain
to anywhere near the breaking point, because every time a

STRENGTH OP MATERIALS

245

piece of metal is strained to a point beyond its elastic limit

it is permanently stretched and weakened. For this reason, it

is never considered advisable to strain

a chain to more than one-half the

amount shown by the method given

for computing the tensile strength. In

other words, the proof test of a chain

should be about 50% of the ultimate

resistance of the weakest link.

Fig. 103.

If, for example, the tensile strength of a chain made from Yi hi-
wrought iron is 40,000 lbs. per square inch, the safe working strength
may be calculated as follows:

Area - Diameter squared X .7854 = .5 X .5 X .7854 = .19635
' .19635 X 40,000 = 7854
7854 X 1.63 - 12,802 lbs.
12,802 X .50 = 6401 lbs.

ultimate breaking strength
proof test, or safe working
strength.

Fig. 104.

Questions

Stresses

1. What name should be applied
to the stress produced at point A in
Fig. 103?
To what stress are the legs of the table subjected in Fig. 104?
To what stress is a boiler seam rivet subjected? (See Fig. 105.)
What stresses are produced in the
main rod of a locomotive when the engine
is working?

5. What stresses are produced in the
piston rod of a locomotive when working?

6. To what stress are the stay bolts of a boiler subjected?

7. To what stress are the sheets of a boiler subjected?

8. To what stress does the blacksmith subject a piece of iron
when he strikes it a blow with his hammer?

2.
3.
4.

Fig. 105.

246 APPLIED SCIENCE

9. To what stress is the boom of a crane subjected when lifting
a load?

Material-Testing

1. What makes one substance stronger than another?

2. What is elasticity of a body?

3. Is it possible to twist, bend, or stretch a body? How may
each of these actions take place?

4. What is meant by a cross-section?

Problems

Stresses

1. What is the weight supported at A and B in Fig. 101?

2. Two men carry a weight of 20 lbs. on a pole, one end of the
pole being held by each. The weight is 2 ft. from one end and 3 ft.
from the other. How many pounds does each man carry?

Material-Testing

In the following examples, 271,000 is the breaking load.

1. A test piece 8 in. long between marks and 1J^ in. square
shows an ultimate strength of 40,000 lbs. per square inch. What is
the total load required- to break it?

2. What is the ultimate elongation in the above test if the
elongation of the whole piece is -fa i* 1 -?

3. The breaking load in a tension test is 300,900 lbs. If the
specimen is 1}^ in. in diameter, what is the ultimate strength?

4. A bar 8 in. between marks is pulled in a testing machine until
it measures 8.125 in. just at the breaking point. What is the per
cent of elongation?

5. A piece of boiler plate 16 in. long stretches .0125 in. during
a test. What is the per cent of elongation?

6. The unit elongation of a piece in tension is jfa in- What is
its ultimate elongation?

7. If a cast iron bar 1J^ in. X 2 in. breaks under a tension of
60,000 lbs., what tension will break a bar of the same material
lJi in. in diameter?

STRENGTH OF MATERIALS 247

8. A bar of wrought iron 2J£ in. in diameter ruptures under a
tension of 271,000 lbs. What is its ultimate strength?

Factor of Safety

For convenience in working the following problems we will use
values given in the table below, unless otherwise specified. These
are average values which have been established by actual test.

Material E. L. U.T.S. U.E. U.S.S. U.C.S.

Brick 2,000

Stone 6,000

Timber 3,000 10,000 .015 3,000 8,000

Cast Iron 6,000 20,000 .005 20,000 90,000

Wrought Iron... 25,000 55,000 .20 50,000 55,000

Steel 50,000 100,000 .10 70,000 150,000

E.L. = Elastic limit
U.T.S. = Ultimate tensile strength
U.E. = Ultimate elongation
U.S.S. = Ultimate shearing strength
U.C.S. = Ultimate compressive strength

The above is given in pounds per square inch, except "ultimate
elongation" which is given in inches per linear inch, "linear" mean-
ing "inch of length."

1. A piece of steel shows a tensile strength of 85,000 lbs. per
square inch, and is used in a bridge where it is subjected to a steady
stress of 17,000 lbs. per square inch. What is the factor of safety?

2. If a piece of wrought iron has a tensile strength of 42,000 lbs.
per square inch, find the load that would be needed to break, in
the testing machine, a piece of the same material % in. in diameter.

3. A wrought iron bar % in. in diameter is pulled apart at a
load of 4970 lbs. What would be the tensile strength of this iron?

4. What would be a safe load for the bar in problem 3 if it
were to be subjected to a varying stress?

248

APPLIED SCIENCE

5. A piece of steel plate with a cross-section J^ in. X 1 in.
pulled apart in the testing machine requires a load of 29,6*00 lbs.
What load would a piece with 1 in. cross-section require?

6. A piece of steel x /i in. square
pulled apart in the testing machine requires
a load of 6000 lbs. What is the ultimate
tensile strength of this material?

7. There are four wrought iron bolts in
the press shown in Fig. 106. If the
capacity of the press is 10,000 lbs., what
size should the bolts be?

8. What must be the diameter of a
steel piston rod if the piston is 18 in. in

diameter and the steam pressure is 110 lbs. per square inch?

Area of piston = 18 2 X .7854 = 254.47

254.47 X 110 = 27,991.7 lbs.
or, about 28,000 lbs., which is the stress in the rod.

9. What size piston rod must we use if the piston is 22 in. in
diameter and the steam pressure is 150 lbs.?

Fig. 106. — Letter Press.

CHAPTER XXII
COMMON FASTENING AGENTS

293. Nails. — The most popular of all fastening agents
is the nail. There are two common forms: wire nails
(Fig. 107) and cut nails (Fig. 108). The wire nail is mads
of a cylindrical piece of wire, with one end sharp-
ened to a point, and the other end flattened into
a head. The wire nail is valuable because of its
holding power and because it will not split the
wood. A disadvantage is that it will bend unless
hit squarely on the head.

A cut nail, as its name implies, is made from cut Fig. 107.
iron or steel. It has two flat, parallel sides and edges Jf 1 .?*
which taper from the head to the point, thus forming
a wedge. When a cut nail is driven into wood, it should
enter the wood across and never parallel to the grain. In

this way the wedge-shaped nail enters the
1 wood in its strongest direction, the length of

the fibers. The holding power of the nail is
thus increased and the wood is not split.
Because of their clinching power, cut nails
are generally used to secure the short hinges

FiG.~108.-^Cut °f a barndoor. Nails are packed and shipped

in kegs (Fig. 110).

Nails.

294. Screws. — There are a great many varieties of screws,
but the principal one is the wood screw (Fig. Ill), which is

249

250 APPLIED SCIENCE

made by machine. Wood screws were originally made with
blunt points. It was then necessary to make a hole in the
wood before the screw could be driven. In the nineteenth
century, the invention of the gimlet-pointed screw obviated

the necessity for this preparatory process. When first
manufacturing these screws by machinery, the metal was
cut out between the threads. This method tended to weaken
them, and they frequently broke when driven into wood.
Later the method of manufacture which is in use today was
introduced. The modern process consists of raising the
thread by a system of rolling and compression. An operator
feeds into a screw-making machine wire of various sizes, and
the machine cuts off the wire at the desired length and turns
the screw. The hammer part of the machine then strikes
the exposed end of the wire, shaping the head of the screw.
This method makes a screw that is Btrong and that p

COMMON FASTENING AGENTS 251

good holding power. Screws are usually made of steel, and
are finished in many ways, so that we have on the mar-
ket blued, brassed, and bronzed screws. Wood screws are

Fia. 110.— Kegs of Nails.

specified by their length, and by a number which is the
gauge number of wire from which thuy are made. They
are sold by the gross. The screw is capable of resisting a
much greater force than the nail, and is therefore a much
better fastening agent. It is, however,
more expensive than the nail, and cannot
be driven into wood so rapidly.

In addition to being used as fastening
agents, screws are also used for communi-
cating motion, as is the case of the lead .
screw of a lathe or the screw of a jack
screw. These screws are produced by a
cutting process in which the thread is
formed from solid pieces of stock; that is,
a single-pointed cutting tool, harder than
the stock, cuts it, or it is cut by means of taps and dies.
The tap and die are tools of hard steel used to produce in-
ternal and external threads respectively.

APPLIED SCIENCE

295. Bolts. — A bolt (Fig. 112) is a special form of screw
with a nut attached or screwed on the end to hold it in place.
A bolt can be more easily removed than a screw. Many
machine shops, especially rail-
road shops, require a large
number of more or less ac-
curately threaded bolts. Bolt
machines thread these bolts by
means of a revolving die which
may be opened at the desired
place, permitting the quick
withdrawal of the bolt.

(o) Round (6) Plat (c) Fill is- 296. Parts of Screw

Head Head ter Head T iu. ead ._Certain definitions

Pio. 112.— Bolte. ...

in regard to the screw should

be carefully noted. A screw may be either right-handed or
left-handed. Right-handed means that, when turning it into
a nut or threaded hole the screw must be turned in the same
direction as the hands ^.___jpj[

of a clock. When the
thread inclines or slopes
so that the under side is
nearer the right hand, it
is right-handed.

The thread shown in
Fig. 113 is a single thread. Fla "S.-Single-Thread Screw.
Figure 1 14 shows a double thread. If three threads are wound
around the cylinder it would have a triple thread. Four or
five threads are sometimes wound around the cylinder, but
this type is not often found in shop practice.

The distance from the bottom of one groove to the bottom

COMMON FASTENING AGENTS 253

of the next is called the pitch, as P in Fig. 114. The pitch is

always the distance from one thread to the next, no matter

whether it is single, double, or triple thread. The distance

that a screw enters

a nut or hole for one

complete turn is

called the lead. For

a single thread the

lead is equal to the

pitch, for a double

thread the lead is

twice the pitch, and

for a triple thread

the lead is three „ „ , , m

. , Fio. 114.— Double-Thread Screw.

tunes the pitch.

The point of a thread is the projecting end. The diameter
of a thread is the distance measured over it, and is the same
as the diameter of the bolt before the thread is cut. The
perpendicular distance from the top of the thread to the
bottom of the groove is called the depth or height; twice
this distance is called double-depth. The root is the bottom
of the groove. The diameter at the root is the outside dia-
meter minus the double depth. This is called the root
diameter.

297. Measurement of Thread. — Figure 115 shows how to
measure the number of threads to one inch of a bolt. In this case
the threads are an even 8 to the inch and we see that there are just
8 grooves from the end of the scale to the 1-in. mark. If a thread
is an even number per inch it can be easily measured with the scale
as described, but when we have fractional threads such as ll}4 per
inch it is best to measure the threads for 2 in., which would give us
23 whole grooves. Dividing 23 by 2 gives 1 1J^ threads per inch.

Fia. 115. — Measurement of Screw Threads.

254 APPLIED SCIENCE

When a bolt is less than an inch long, it is necessary to count the
grooves in Yi in. and multiply this by 2 to get the threads per inch.
The best way to measure threads is with the thread or pitch gauge.
The number of
threads per inch is
the same on the
same sized bolt
whether the thread
is cut single, double,
or triple. If a double
thread, 8 threads
per inch is wanted,
we ask for "8
threads per inch
double"; if a triple
thread, we say "8 threads per inch triple." Although to avoid
any misunderstanding it would be clearer to say for the double
thread, " % in. lead, H m - pitch, double thread." There would
then be no chance for mistake since we sometimes find an old print
which calls for "8 threads per inch double," and means that
a double thread, 16
threads per inch is
wanted. With single
threads the word "sin-
gle " is not used, as it is
understood. All single
threads of coarse pitch
weaken considerably
the bolt or piece which
is threaded. For this
reason, multiple
threads are used. With

a double thread the FlG U 6. -Triple-Thread Screw,

groove is only one-half

as deep as a corresponding single thread, and the bolt will ad-
vance just as far for one turn as it would if cut single. Figure
116 shows a triple thread with its corresponding single thread
dotted.

COMMON FASTENING AGENTS 255

298. Depth of Thread. — It is important to be able to
find the depth of a thread, for upon this depends the cutting
of all threads and the size of all tap drills. By referring to
Fig. 117, we see that the depth of the thread is the altitude
of a right-angle triangle, since the angles are all 60° and the
sides of the V or groove are equal i__ mcH ^ ^

to the pitch. Knowing two sides /fv /|\\

of a right-angle triangle we can /*\ /§\ \^

easily find the other, since we /\ f\/ ^j \\^

know that the square of the alti- *"~ " 1^7/rat ~\

tude of any right-angle triangle is fig. 117.— Measurement of

equal to the square of the hypo- Pitch of Screw.

tenuse minus the square of the third side. A simple problem in
square root will give the correct figure for the altitude of depth.
An easier way to find the depth of a United States or V
thread is to remember that the depth of a United States
thread of 1 in. pitch is .65 in. and the depth of a V thread of
1 in. pitch is .86 in. Now if we wish to find the depth
of any other thread we simply divide these figures by the
number of threads to the inch. For example, we determine
the depth of a United States standard thread 13 threads to
the inch in this manner — .65 -5- 13 = .05 in., and the depth
of a V thread 4 threads per inch, in this manner — .86 -r- 4
= .215. When figuring the size to bore or drill a nut or
a hole to be threaded, subtract the double depth of the thread
from the outside diameter of the thread on the bolt or
rod.

299. Kinds of Screw Threads. — There are many kinds of
bolts and screws to meet different needs and in order to
specify a particular grade of bolt or screw it is necessary to
mention :

256

APPLIED SCIENCE

(a) Shape or form of thread.

(6) Pitch, or number of threads to the inch.

(d) Outline of body, barrel, or stem.

(e) Diameter.

(J) Direction of thread.

(g) Length.

(h) Material.

Before 1861 every manufacturer had a peculiar thread
that he made for his own work. The result was that the
large number of threads caused confusion among engineers
and machinists. To avoid this it was proposed to have a
standard form; today each country has a standard of its own.

300. Standard Threads. — The two forms of screw threads
in use in the United States are the common V thread and
the United States standard thread, while the Whitworth screw
is the most common in England.

The V-shaped thread (Fig. 118a) is a thread having its
sides at an angle of 60° to each other and perfectly sharp

at the top and bottom.
This thread is used most-
ly on screws designed for
wood-working and for
small brass work. The
objections to its use are
that the top, being very
sharp, is injured by the slightest accident; and that in the use
of taps and dies, the fine, sharp edge is quickly lost, causing
constant variation in fitting.

The V-shaped thread is the strongest form of screw thread
used in the making of bolts. But because the thrust be-

te) V Thread (^Whit-
worth
Thread

Fig. 118. — Standard Screw Threads.

COMMON FASTENING AGENTS 2$7

tween the screw and nut is not parallel to the axis of the
screw, there is a tendency to burst the nut. Therefore this
form of thread is unsuitable for transmitting power.

The Whitworth's screw (Fig. 118b) is slightly rounded
at the top and bottom. Compared with the American threads,
the difference is in the angle between the sides, which is 55°.
The French have a standard screw with the thread at an
angle of 60°, with a flat top and bottom. Its pitch and dia-
meter are given in millimeters. An international standard
for metric screw threads was adopted at Zurich in October,
1898. This thread is based on the United States standard,
which is an equilateral triangle truncated (cut) one-eighth
of its height at top and bottom.

The United States standard thread (Fig. 118c), often
called Seller's thread (from the man who first manufac-
tured it), is also made with its sides at an angle of 60° to
each other, but its top is cut off to the extent of one-eighth
its pitch, and the same quantity is filled in at its bottom.
The advantages claimed for this thread are that it is not
easily injured, that the taps and dies retain their size
longer, and that bolts and screws made with this thread
are stronger and have a better appearance. As this thread
has been recommended by the Franklin Institute of
Philadelphia, it is sometimes called the "Franklin Institute
Standard."

Since this thread is flattened or cut off at the point and root
an amount equal to one-eighth of the pitch, it is only three-
fourths as deep as a V thread of the same pitch. For example,
a 1-in. bolt threaded with a United States standard thread
will have a root circle .837 in. in diameter, while a V thread
of the same pitch cut on a 1-in. bolt will have a root circle
.784 in. in diameter. This shows that the V thread cuts into

258 APPLIED SCIENCE

or "nicks" the bolt deeper, and therefore the bolt is not so
strong as when threaded United States standard.

301. Taps and Tap Drills. — A tap is a tool for cutting
inside or internal threads in holes so that the holes will hold
tightly the bolts, screws, or studs which may be screwed into
them. Taps are generally made from hammered round bar
steel. After being drawn nearly to size, they are heated to
a low, red heat, and covered with lime or ashes, that they
may cool slowly. This process softens the metal and takes
out the strains, which occur in iron or steel after it is ham-
mered. The outside surface or skin, where the hammer
blows affect the iron most, is subjected to the greatest strain,
or^as it is called "initial tension." There are many styles
of taps, the most common being standard hand-taps, boiler
taps, stay bolt taps, pipe taps, and machine screw taps.

Tap drills are drills used to make the proper sized hole
for a standard tap, leaving the hole small enough in diameter
to permit of threads being made by the teeth of the tap.
For example, the size of tap drill for a ^ in. screw is .24
in. in diameter; for a J^ in. screw tap it is .4 in., leaving
.1 in. for the diameter of threads on both sides of the
hole. The size of a drill's or reamer's outside diameter and
the size of a tap is the diameter outside of the threads, and
not the size at the bottom of the threads.

Standard hand-taps are found in sets of three. Figure
119a is called a taper tap and is used to start the thread in
the drilled hole; Fig. 119b is called a plug tap, and Fig.
119c, a bottoming tap. The plug tap will finish the thread
if the hole goes through the piece, but if the hole "bottoms"
or only goes part of the way through, the bottoming tap must
be used to cut a full thread the entire depth of the hole.

COMMON FASTENING AGENTS

?.o9

The word "standard" means that the number of threads
to the inch is United States standard, and all taps made to
this standard are exactly alike,

302. Teeth of Taps.— The teeth or cutting edges of taps
are radial. The cutting edge of a tap penetrates the metal
very much like a wedge.
For this reason taps for
taking very heavy cuts
are backed off much
more than finishing taps
which take light cuts.
Too much backing off
makes the tap wobble in
the hole and weakens
the cutting edges of the
teeth .

Taps made for cutting

the threads in solid wood

and split dies for screw cutting are called hobs. They differ

from ordinary taps chiefly in having from six to eight more

flutes. A large number of flutes makes the tap stiffer and less

likely to wobble. As a result, the thread cut will be more

perfect than if made with

an ordinary tap. The

i term hob is also applied

to the milling cutter used

"* for cutting the toeth of

Copyrighted by Miller Falls Co.

FlG jgo worm wheels.

303. How to Determine the Size of a Tap Drill. — A simple
method of finding a tap drill for a V thread, or a United States
standard thread tap, is provided by the following formulas (see

(e) Bottoming Tap
Fio. 119.— Taps.

260

APPLIED SCIENCE

Fig. 120), where S is the desired size, T the diameter of the tap or
screw, and N the number of threads per inch.

For V thread:

5 - T -

1.733

For U. S. standard thread :

S = T

Example. — What is the tap size drill for a % in. diameter 10
thread per inch V-thread tap?

1.733 3 1.733

.75 - .1733 « .5767 in.

N 4 10

S - T -

COUNTER BUTTON SMASHED _^

*SUNK POINT />0/NT TAP

POINT ^^ SK fitVET

Fig. 121. — Rivet Heads and Points.

304. Rivets. — A rivet before being driven is a simple
cylinder finished at one end with a head. Various forms of

heads are shown in Fig.
121 . The point of a rivet
is formed when it is
driven, while the rivet is
hot. Various forms of
points are shown in the
sketch. A tap rivet is not
really a rivet, but a form of screw. After being tightly
screwed in place and secured, the square projecting portion
shown in the sketch is cut off leaving a flat or flush head.
Tap rivets are used for connecting thin to relatively thick
parts.

Questions

1. State the advantages and disadvantages of a cut nail.
What causes a nail to split the wood?

COMMON FASTENING AGENTS 261

2. State the advantages and disadvantages of a wire nail.

3. What advantage has a screw over a nail, as a fastening agent?

4. Explain the manufacture of screws.

5. What is a bolt?

6. Explain the construction of different screw threads.

7. What are the advantages and disadvantages of each?
Draw sketches.

8. Define the following terms: thread, triple thread, pitch,
lead, point, depth of a thread, root of thread, root diameter, pitch
of screw, number of threads to the inch.

9. What are the uses of the different screw threads?

10. How is a thread placed in a hole?

11. What is a tap?

12. What are the standard hand-taps?

13. How would you determine the size of a tap drill for a thread?

CHAPTER XXIII
COMMON HAND-TOOLS

306. Kinds of Hammers. — Among the hand-tools there
are a number of hammers that are common to most trades.
Therefore it is necessary to know the principles underlying
their construction and uBe.

The small end of the hammer is called a peen, and "to
peen" means to hammer lightly with the small end. Ham-
mers are made of tool steel and tempered
very hard on each end, the eye being left
soft. The neck of the hammer handle is
made small so that it will spring a little
under the shock of the blow. The spring
makes it less tiresome to use. The face of
the hammer is made slightly crowning or
rounding.

The claw hammer (Fig. 122) used prin-
cipally for driving nails, is probably the
most commonly used tool. It is based
upon the principle of the lever. The
hammer should not be grasped near the
head but at the end of the handle, so that
the greatest leverage may be utilized. To
Fiq. 122.— Claw deliver a free,accurateblow,the wrist should
be kept up so that the handle is horizontal
when the blow falls. Claw hammers are graded by the weight of
the head ; the ordinary claw hammer weighs from %to\% lbs.

COMMON HAND-TOOLS

263

Machinists' hammers for metal work are made in three
forms as shown by Fig. 123. Fig. 123a represents a ball-peen
hammer, the small end of which is shaped like a ball; Fig.
123b a straight-peen; and Fig. 123c a cross-peen hammer.

The sledge hammer, used many times every day by the
blacksmith, is a tool so large and heavy that two hands are
usually needed to wield
it. Sledge hammers are
also used for breaking
coal, those designed for
this purpose having a
particularly long head.
The heavy smooth-faced
hammer, frequently used
for driving wedges in splitting stone, is also referred to as a
sledge hammer. The peen of a sledge hammer is usually
made of steel.

There is still another hammer called a lead or copper
hammer which is used for striking on finished parts that
would be dented by a steel hammer. The machinist never
uses a steel hammer on finished work. Other hammers
used for special purposes are the chipping and riveting
hammers.

(a) Ball- (6) Straight- (c) Cross-

Peen Peen Peen

Hammer Hammer Hammer

Fig. 123. — Machinists' Hammers.

306. Kinds of Chisels. — The simplest form of metal cut-
ting tool is the chisel, called a cold chisel. The mechani-
cal principle of the cutting edge of the chisel is that of the
wedge. Chisels for machine work differ from wood chisels
in several ways, the principle difference being that cold
chisels have no handles. There are many kinds of chisels
in common, use in the metal trades, some- small and some
large, but all are generally made of % in. octagonal (8-sided)

APPLIED SCIENCE

fool steel 8 in. long. After the chisel is forged (hammered
in a hot condition) to the required shape, the end is hardened
by drawing the temper (heating) to a purple color. There
are three elements to be considered in making a good chisel,
namely, shape, temper, and cutting edge. Chisels must be
forged and tempered at a low heat, as a high heat will burn
the steel (burn the carbon out of the steel).

W) (6) (c) (d) (e)
(a) Flat Chisel (Side View).
(6) Flat Chisel (Front View).

(ft) Round-Nose Chisel.
(i) Side Chisel (Front View).
0) Side Chisel (Side View).
Fig. 124.— Chisels.

Chisels made for use in the pneumatic hammer are longer
than hand-driven chisels. The shanks are fitted to the
holder or socket in the hammer and the chisel bead should
be tempered to keep it from upsetting. Ordinary chisels
should never be used in the pneumatic hammer. The flat
chisel (Fig. 124, a and b) is the form most commonly used.
The cutting edge is generally drawn out about y% in. wider
than the stock from which it is made and then ground to an
angle of 60". For cutting soft metal the angles should be
less ; 30° for lead or Babbitt metal (a soft mixture of metals),

COMMON HAND-TOOLS 265

and 45° for brass and soft cast iron, may be used. For very
fine chipping, the cutting edge may be curved slightly, as
shown by Fig. 124c. A small cutting angle used for cutting
steel would soon break, while a blunt or large angle would
not cut Babbitt metal but would simply tear it off. The flat
chisel is used for all-around chipping, snagging castings, etc.

Figure 124, d and e, shows another common form of chisel
called a cape chisel. It is made of the same steel and tem-
pered in the same way as the flat chisel, but the point is
drawn down to a width of about 3/8 in. The cape chisel is
made wider on the cutting edge at A than it is at B to provide
a clearance, and keep the sides of the chisel from breaking out
the edges of the groove or channel which is being cut. The
cutting edge is ground to the same angle as on the flat chisel.

There are four other forms of chisels used, but they are
not so common as the flat and cape chisels. These are the
gouge (Fig. 124f), the diamond-point (Fig. 124g), the round-
nose (Fig. 124h), and the side chisel (Fig. 124, i and j). They
are made of the same stock as the other chisels and tempered
in the same way. The diamond-point and round-nose, like
the cape chisel, should be made wider at the cutting edge than
farther back, for clearance. The round-nose is very much
like the cape chisel except that the cutting end is rounded
and the bevel is on one side only. The side chisel is ground
with only one bevel, like a wood chisel, but with angles just
the same as if it had two bevels. This chisel should also be
ground thinner or " backed off" near the point for clearance.

The gouge is used for work on round corners and on all
concave surfaces. The diamond-point is used for cutting
V-shape grooves and finishing out square corners; it is
also used for drawing drilled holes and for cutting round
corners and oil grooves.

266

APPLIED SCIENCE

(a) Hot Chisel

There are several other forms of chisels used especially
by boiler-makers. Figure 125 shows four handle chisels,
so called because they are held by the wooden handle when

used. A hot chisel (Fig.
125a) is used for trim-
ming or cutting hot
plates, etc. The cold
handle chisel, used for
general chipping on boiler
work as well as erecting
work, is very similar, ex-
cept that the cutting edge
is not drawn so thin as
that of the hot chisel.
Figure 125c shows a
round punch used for
knocking off rivet heads
and driving out stay-
bolts, rivets, etc. Figure

(6) Square Punch
Chisel

(d) Side-Set
Chisel

Fig. 125.— Handle Chisels.

125b shows a square punch used for driving keys and
knocking off rivet heads. Figure 125d shows a side set
which is also used for cutting off rivet heads. All these
tools are made of tool steel. The hot chisel is tempered
to a dark straw color and the cold chisel to a blue color;
the set is also tempered slightly. It is customary not
to temper or harden punches since they would be apt to
break off. The handles in all these tools should fit loosely
and should be made of soft yielding wood so that the shock
or jar of a glancing blow will not hurt the hands.

307. Kinds of Files. — A file is a bar of high-grade crucible
steel, pointed at one end for a handle and having cutting edges

COMMON HAND-TOOLS 267

or teeth extending from a point near the handle to the opposite
end. The mechanical principle of the teeth of a file is that
of the wedge. The handle acts as a lever. In the course
of manufacture, files pass through the successive processes of
forging, annealing (gradually heating and cooling), grind-
ing, cutting, hardening, and tempering. They are annealed
before being ground and cut, and
thus the hardness is reduced, i iwkv^s^
File teeth are like a series of
small chisels cut at an angle v tMM0kgmt0 ~- ^„- ru

° v WORK ^^7££TH

to the sides of the file, as shown M 126> __ Action of Kle

in Fig. 126. Cutting on the re- Teeth.

turn stroke dulls the teeth and

injures the file. It is possible to destroy some of the teeth

of a brand new file in one minute's careless work.

Many new kinds of files of all shapes and sizes, have re-
cently appeared, so that there are now at least 104 different
varieties on the market. All may be divided into three
general classes, namely single-cut, double-cut, and rasps
(Fig. 127). The files in each of these classes vary in length,
in shape, and in coarseness of teeth.

A single-cut file has the teeth all running diagonally
across the face in one direction only. A double-cut file
has the teeth criss-crossing or running across the face in
two directions, making a surface covered with small, sharp
points. Each style or shape of single-cut and double-cut
file has several grades of coarseness. These grades are called
coarse, bastard, second-cut, and smooth, the coarseness
varying with the length of the file. The longer the file, the
coarser the teeth and the cut. Single-cut files are generally
used for cutting soft metals and for lathe work. Their
coars?r grades are sometimes called float files, or "floats."

268

APPLIED SCIENCE

The double-cut files are used for all kinds of hand-work. The
teeth of a rasp are entirely separate. They are round on the
top and are formed by raising with a punch, small porjbions of
stock from the flat surface of the file flank. The rasp is used

(«)

(b)

(c)

(a) Single cut.

Fig. 127.— File Cuts.
(6) Double cut.

for removing large quantities of stock quickly and will work
well on soft metals and even on wood. When a good job is
wanted a rasp must be followed up with a file of finer grade.
Piles are made convex, i.e., rounding, as shown in Fig.
128, for three reasons : (1) to overcome the effect of the spring
down or bending of the file due
to the pressure of the hands in

making a cut; (2) to overcome Fig. 128.— Shape of File,
the spring or warp caused by

heating and hardening the file when made; (3) to make the
file bite or cut with only a few teeth in the middle of its length.
Figure 1 29 shows the end view of sections of files. A is the flat
file, B the hand, C the square — the most commonly used — D
the triangular or 3-square, E the half-round, and F the round.

COMMON HAND-TOOLS 269

The length of a file is the distance from the heel H to the point

P (Fig. 130). The tang T is not included in the length. In order-
ing a file from the toolroom it is c

necessary to state the length, the 4 I I

degree of coarseness, and the shape. L - ' *—r*

For example, you may want a* 14 ^ A

in. flat bastard, or a 16 in. half- « ■ ' *—*

round float ^ IG# *^9. — Cross-Sections of

Files.

308. Methods of Filing. — It requires a great deal of
practice to file a surface flat, as there is a great tendency for
the file "to rock or fulcrum" on the corners of the work and
make the surface rounding or crowning. The worker should

always take long strokes, not short
f=^^HHOTBf jerky ones. Figure 131 shows the

umm correct method of holding a file.

Fig. 130.-Measuring a Jf ^ ffle ig alwayg ^^ Qr pughed

one way a series of small grooves
will be cut across the work. It is always best to drive the
file diagonally across the first direction to make a smoother
surface. If this is done the file will always bite (cut) better,
and as the marks can be seen the eye will tell when you have
filed over the whole surface.

Sighting (looking) along the length of a new file will show
which side is the most "bellied"
(curved). This side is the best
>one to use.

Cast iron is harder to cut Fia. 131.— Proper Method of

with a file than wrought iron or Usmg a ^

soft steel. A new file should never be used on rough cast
iron, as the scale will dull the teeth and soon spoil the file.
If the scale is not very deep it can be removed with the
cutting edge of a flat file. When a file is too dull for cast

270 APPLIED SCIENCE

iron, it may still be useful for cutting wrought iron or soft
steel. Some flat files have a safe edge, i.e., a smooth edge
with no teeth. Such files are used when it is necessary to
file out a corner, as the safe edge prevent* cutting a groove
in one side of the corner when the other side is being filed.
Such a file is shown in Fig. 132.

Files get clogged with chips and should be frequently

cleaned with a wire brush, called a file-card. This will

remove the chips, and keep the work from being scratched

and grooved. File-cards are generally carried

in the toolroom. When cutting cast iron

with a new file, a little white chalk should be

rubbed on the file; this chalk will absorb the

oil and the chips will not be so likely to stick.

Oil should never be used on a file for cast iron,

but will sometimes make a file work better

F 'th sT Ed"' !e on wr0U B &t ' ron ' ft * 8 - however, best not

to use oil if only one file is available for both

metals. When filing cast iron, the hand or finger should not

be rubbed over the work, as the work will become greasy

as a result and keep the file from cutting.

When filing finished work in the vise, the lead or copper
jaws should always be used. Otherwise the vise jaw will
bite into the work. The work may be given a very smooth
finish by draw filing, which is simply drawing the file in a
direction at right angles to its length. A single-cut, second- ,
cut, or smooth file is best for draw filing.

309. Use of Scrapers. — When a job cannot be finished
accurately enough with a file, a tool called a scraper (Fig.
133) is used. Scrapers are generally made from octagonal
steel flattened on both ends and tempered very hard to a

COMMON HAND-TOOLS

271

• STRAIGHT C06£ CU*V£0£OG£*

Fig. 133. — A Scraper.

light straw color. After grinding, the edge should be rubbed
down on an oil stone. On one end of the scraper the edge
may be slightly curved as shown:

Another type of scraper with a wood handle, sometimes
called a graver, is used for work
in lathes and for hand-work on
round corners. A good scraper
can be made from an old file.
When work is to be scraped it must be first rubbed or
tested on a standard and perfectly flat plate called a sur-
face plate. The method used is to put a very thin coat-
ing of red lead mixed with oil on the surface plate. The
high points which must be removed first, are shown by small
red spots on the surface of the block. When the work is
heavy and awkward to handle the surface plate may be
j. j. rubbed on it. Care is required to rub
| I over the whole plate evenly to prevent

| I wearing and dishing the center.

JIjI 310. Kinds of Drills. — Drill points

^j are used for boring small holes in

A A K f wood, iron, brass, or other materials.

M III There are three kinds of drills; flat,

MA 1^1 straight-fluted, and twist drills (Fig.

wm l\ 134). The flat drill can be used for

▼^ almost any material, but does not cut

(Copyrighted by Millers ... . - ,

Pails Co.) so rapidly as either of the others. It

is best suited for use on thin metals

and on tile. The straight-fluted drill
Fig. 134.-Drill Points. can be uged advantageous i y on wood

and the softer metals. It is especially satisfactory for drilling
holes all the way through a piece of material, as it does not

(a) (6) (c)

Straight- Twist Flat
Fluted

272 APPLIED SCIENCE

have a tendency to "draw in " when breaking the hole through.
The twist drill is the most rapid cutter of the three, and is
especially desirable for work on very hard woods or heavy
metals, and for work where a deep hole is to be drilled. The
twist drill, besides presenting a cutting edge at the point, carries
the chips up to the surface, and thus prevents clogging. It is,
therefore, unnecessary to remove a twist drill from the hole
to clear it of chips.

311. Drills and Drilling. — Most drills are made from
round bars of tool steel hardened and tempered to suit the
work to be performed, generally to a dark straw color. The
flat drill is made in the shop and is used because it is cheap.
It is impossible to drill a hole accurately with a flat drill,
although such a drill does very well for rough work in the
boiler or smithshop. The flat drill was the first form of
drill made, but later it was found to wear out quickly and
require frequent grinding. Thus the cutting edge or Up
wore away so rapidly that the drill soon had to be redressed
(made over) by the tool-maker. To overcome this fault the
lips were twisted into a curve or spiral. This improvement
was found to give a cutting edge which did not change its
shape when the drill was reground. Thus it is evident that
the twisted flat drill led to the fluted twist drill and later to
the flat twist drill. The former drill is a round bar of tool
steel having two straight grooves or flutes cut on opposite
sides. This form of drill is used for drilling in brass, copper,
or Babbitt metal.

312. Mechanism of Drill Points. — To understand the
principle of drilling efficiently, it is necessary to study the
mechanism of a drill point. Drills are used to separate small

COMMON HAND-TOOLS

273

Fig. 135.— Cutting
Edge of Flat Drill.

particles of metal by scraping or cutting and to do this there
must be a central or leading point about which the cutting
edges turn. Figure 135 shows the cutting edges of a flat
drill. The mechanical principle of the
cutting edge of the drill is that of the
wedge. It is seen that the left lip AB is
ground at an angle sloping in the opposite
direction from the right-hand lip CD.
The angle of these slopes, called the clear-
ance angle, is shown in the side view.
The line bd in the plan view represents
the intersection of these sloping lip faces
and is called the drill point.

Clearance with a drill is practically the
same as with a cold chisel. It is very important that the
clearance angle for the metal to be cut should be ground cor-
rectly. Giving the lip of a drill clearance is nothing more than
cutting back or " backing off" the face of the lip, so that its
cutting edge will cut clean and will not scrape or rub on the
bottom of the hole which is being drilled.

The two-fluted twist drill (Fig. 136)
and the counterbore (Fig. 137) are
among the most extensively used types.
Twist drills work more accurately than
flat drills. The cylindrical shape fills
the hole, keeps the drill properly
ground, and also serves as a channel
through which the chips may pass
out of the hole, their spiral form
wedging or forcing them out as the drill
rotates. Twist drills are sometimes made with three flutes.
These are used for enlarging cored or punched holes, but

Fig. 136.
Two-
Fluted
Twist
Drill.

Fig. 137.
Counter-
bore.

274 APPLIED SCIENCE

they will not drill the initial hole. Some twist drills are
made with a small groove cut around the outside, which
contains a tube for carrying oil to the drill point.

313. Operation of Reaming. — It is difficult, if not quite
impossible, to drill a hole to an exact diameter. For most
work, however, a variation of a few hundredths of an inch
is of no account, but when greater accuracy is required the
hole must be reamed. Holes to be reamed are first drilled
a little smaller than the desired size ( B V in. or even 1 ^ in.),
and then reamed out to exact size. They should never
be drilled over - 3 l j in. smaller than the size of the reamer.
Reaming is especially necessary where two or more parts
are to be bolted together, since the drill in passing through
them will often cut more out of one part than another because
of the variation in the structure of the metal.

Reaming may be done by hand or with a drilling machine;
or the reamer may be held in the drilling machine, or in the
drill spindle socket and turned by hand with a wrench.
Reaming should be done very carefully, and it may be neces-
sary to tap the reamer gently with a hammer or wrench
to feed it. There should be no " wobbling" or irregular mo-
tion, but a very steady and slow motion under light pressure.
In some cases the weight of the reamer and the wrench is
sufficient to feed the tool through the hole.

In reaming with a drill press a power feed may be used
in some cases, but great care must then be exercised to see
that the reamer does not stick and break. Some reamers
have a shallow screw thread cut on the small end which
makes them self-feeding. Oil, drilling compound, or some
other lubricant should always be used when reaming wrought
iron or steel, but not when reaming cast iron or brass.

COMMON HAND-TOOLS

275

<«)

314. Kinds of Reamers. — When not carefully sharpened,
all forms of reamers have a tendency to produce a rough hole.
Too much clearance reduces the support of the reamer in
the hole and tends to make it work unsteadily.

Reamers are made from tool steel and then hardened and
tempered to a straw color; they may be straight or tapered,
and may have a square end or tapered shanks. The square-
end reamer is generally operated by hand. Reamers may
be solid or may be made with inserted, adjustable blades.
The solid reamer has the
disadvantage of becom-
ing undersized as soon as
worn, but the adjustable
reamers are considerably
more expensive.

Figure 138a shows a
straight-fluted reamer
with a square end, the
type most commonly
used. Figure 138b shows
a spiral straight reamer,
which is used when a slow feed is required. The spiral is
made left-handed, while the reamer, in cutting, turns right-
handed; this construction tends to prevent the reamer from
drawing into the hole and sticking. Figure 138c is a straight-
fluted shell reamer, so called because it is made hollow in the
center in order that it may be used with a mandrel. Figure
138d shows a rose reamer. There are a great many other
kinds of special reamers made for different classes of work,
but space will not permit their being described here.

Reamers are rarely given less than 6 flutes, and usually
have from 6 tQ £0^ the number depending upon the size of

(a) Straight-Fluted Reamer

(b) Spiral Straight Reamer

(d) Rose Reamer

Fig. 138. — Reamers.

276 APPLIED SCIENCE

the reamer. The number of flutes is generally made odd
in order that there will always be two teeth opposite one
tooth. These two teeth stay or hold the tool better so that
it does not tend to wobble or chatter as much as it would
with but one tooth opposite one tooth. It is easier, how-
ever, to caliper (measure) a reamer with an even number
of flutes, having one tooth exactly opposite another on the
diameter. With reamers having a large number of teeth,
the odd or even feature is not of so much consequence.
Shell and rose reamers may be given the same number of
flutes and have their cutting edge formed in the same
manner as solid reamers.

316. Emery Cloth. — The art of finishing or polishing
wood and metal is very old. Originally it was done by tak-
ing the dried skins of sharks and rubbing the material.
Later sandpaper and emery cloth were invented. As
nearly as can be ascertained, emery cloth and sandpaper
came into use about two hundred and fifty years ago. The
process of manufacturing was then very primitive, consisting
of coating the backing with glue, covering it liberally with
the desired abrasive, shaking off the superfluous material,
and hanging the sheet up to dry. The steady march of
progress, however, has brought about wonderful improve-
ments in the manufacture of abrasive papers and cloths.
At the present time emery cloth is made from Turkish emery
of different grades. Turkish emery is a hard black and brown
stone found in Turkey and brought to this country for use
in machine shops. Its quality, for hardness and durability
in mechanical work, has never been excelled in any stone yet
found. The cloth made is of various grades of coarseness.
The numbers representing the grades of emery run from 8

COMMON HAND-TOOLS 277

to 120, and the degree of smoothness of surface they leave
may be compared to that left by files as follows:

8 and 10 represent the cut of a wood rasp

" 20

" a coarse rough file

" 40

" an ordinary rough file

" 40

" a bastard file

" 60

" a second-cut file

" 80

" a smooth file

" 100

" a superfine file

120

F and FF

" a dead-smooth file

316. Polishing and Burnishing. — Metal is polished to give
it a fine finish and to produce a smooth surface which will
reflect light to its highest degree — in other words to give it
a "shine." The principal substances or abrasives used to
produce such a surface are emery, carborundum, rouge,
putty powder, silica, and burnishing materials. While
emery is not so hard as some other abrasives, it is the strong-
est abrading powder. The powder principally used for giving
a fine polish to small articles is called rouge, and is composed
of ferric oxide. Most polishing compounds contain rouge.
Its color and properties depend to a large degree on the tem-
perature at which it is manufactured. Rouge made at a
low temperature is soft proportionally. For this reason,
jewelers' rouge is made at a low temperature, while rouge
for polishing iron is made at a high temperature. Putty
powder is an oxide of tin. Silica is the oxide of silicon, and
is found in different forms: in the crystalline form it is
called quartz; in the form of sandstone, which consists of
particles of crystalline or rounded silica cemented with
silica powdered sand, it is used for grindstones. Artificial
polishing stones are made by cementing very fine white sand
with shellac or other materials.

278 APPLIED SCIENCE

Burnishing is the process of producing a smooth surface
by pressing down the inequalities or rough spots. It is,
therefore, best adapted to soft materials.

317. Development of Grinding Stones. — Tools were
originally shaped by chipping one stone against another
until the stone which was to be the tool was made the desired
shape. When man learned the use of metal, he continued
to sharpen his
tools on certain
grinding stones
or rocks. Ex-
perience taught
him that the
most effective
way to grind his
tools, was to
make the stone
circular, with a
flat edge, and
mounted on a
F.<-.. ISO.-Grindstone. ghaJt) and ^

to reduce the heat of friction the stone should be rotated
through a water bath.

Originally grindstones were made of sandstone, composed
of hard, sharp particles of sand or quartz. Since then better
and harder forms of stones have been discovered and placed
on the market. These modern grindstones (Fig. 139) are made
of emery, alundum, corundum, and carbide of silicon. Emery
has a rounded, opaque grain, while alundum grain is parti-
cularly sharp. Corundum grain is sharp and transparent,
with distinct evidences of crystallization. Carbide of silicon

COMMON HAND-TOOLS 279

grain presents a distinct crystalline structure with a sharp
cutting edge. From these materials are made a wide variety
of grinding wheels and sharpening stones.

318. Corundum and Emery Wheels. — Corundum is an
extremely hard oxide of aluminum. Emery is a very hard,
granular variety of corundum, containing a small amount
of magnetite or hematite. Ground to a powder, these sub-
stances are used for polishing, grinding, or abrading stone,
metal, glass, etc. In the crushing and grinding process,
which is conducted in machines more or less enclosed, con-
siderable fine dust is given off. After sifting and grading
according to fineness, the product is stored in appropriate
compartments, from which it is taken as needed. Wheels
are made of emery or other abrasive material.

The proper selection of a grinding wheel may be the means
of saving much money and time, as each metal requires some
special difference in the wheel. Wheels are of different
coarseness and grades, and when ordering, the diameter,
thickness, size of hole, and grade number must be given.
It is not reasonable to expect a wheel which was made for
cast iron to grind properly brass or steel. Some wheels
are made so that they will stand a constant stream of water
running over them, while others will not. When moisture
is to be used with the wheel, this fact should be stated in
ordering.

The grade letter of a wheel denotes the hardness to which the
wheel has been baked in the retorts. The number of the emery
denotes the particular grade of that substance which is used in
making the wheel. The number of emery and the grade letter of
wheels to be used for some of the most important materials are
as follows;

Emery No.

Grade Letter

16-20

P-Q

20-36

P-A

16-20

R-J

16-30

O-P

34-46

N-0

20-30

P-R

280 APPLIED SCIENCE

Materials

Large Iron or Steel Castings
Small Castings
Hard or Chilled Castings
Wrought Iron Forging
Lathe and Planer Tool
Brass Castings

The makers of emery wheels usually paste tags on each
wheel stating the grade, speed, and order letter, but in some
cases the machinist may have to find the speed for special
wheels. If the wheel is run at a higher speed than that
stated on the tag, the centrifugal force may, as before stated,
break the wheel.

Some emery wheel houses advise a speed of 5500 ft. per minute.
From this we can calculate the speed for any diameter by multiply-
ing the diameter in inches by 3.1416, reducing to feet, and dividing
this figure into 5500. A 10-in. wheel would give us 10 X 3.1416 =
31.416 in., or 2.6 ft. 5500 divided by 2.6 - 2108 revolutions per
minute.

319. The Discovery and Use of Carborundum. — The

discovery of carborundum nearly thirty years ago, brought
into use a new and exceptionally efficient abrasive. In 1891,
experiments with electric furnaces showed that when clay
and crushed coke were heated through a piece of carbon in
an electric furnace, the heat fused the two ingredients, and
that when the carbon was withdrawn, minute crystals adhered
to it. These tiny crystals were found to be amazingly sharp
and hard. Subsequent tests proved that the material had
great value as an abrasive, and it is now in general use.

The principal materials entering into the manufacture of
carborundum are coke, which supplies the element of carbon,

COMMON HAND-TOOLS 281

and sand, which supplies the silicon. The coke is crushed
in a mill, and is then mixed with the sand. The mass of
raw material is then placed in an electric furnace for 36
hrs. and a current of 2000 electrical horse-power is passed
through it.

The resistance thus interposed results in the generation of
enormous quantities of heat, so great is the temperature of
the resistance path; the surrounding mass of coke and sand
is heated to a point which is between 4000° and 4500° F.
In this terrific heat all known metals not only melt, but vola-
tilize (disappear in the form of a gas). Iron and steel are
turned to vapor and granite rocks melt away. All the im-
purities and substances in the coke and sand other than
carbon and silicon are destroyed or driven off in gaseous form,
and the atoms of these two elements fly together and unite
as carborundum.

The total energy used in a single run of a carborundum
furnace is 72,000 horse-power hours. Incidentally, enough
electric power is consumed to operate an arc light continu-
ously night and day for twelve years, or to operate one
16 candle-power carbon incandescent lamp for two hundred
and twenty years.

Questions

1. Draw a sketch of a hammer removing a nail from a board.
Where is the fulcrum?

2. Would you gain more advantage in holding the handle of
the hammer in the middle or the end? Explain.

3. Why are hammers graded by weight?

4. Why is the neck of the hammer made small?
6. Name the common hammers and their uses.

6. How does a chisel for cutting steel differ from one used in
cutting wood? Why?

7. Explain the different forms of cold chisels,

282 APPLIED SCIENCE

8. Explain the manufacture of a file.

9. What is the mechanical principle of a file?

10. What is the difference between a file and a rasp?

11. Draw a sketch of a file. Name the principal parts.

12. Name the different kinds of drills and the shape and pro-
perties of each.

13. Explain the mechanism of a drill point?

14. Is it possible to drill a hole to exact diameter? Why?
16. What is reaming?

16. What effect will irregular motion have in reaming?

17. Why is it necessary to use oil or some lubricant when ream-
ing wrought iron or steel?

18. What is corundum? Describe some of its physical properties.

19. Why is it necessary to have a special difference in grinding
wheels for different metals?

20. What holds the particles of a grinding stone together? Is
there any danger of the stone's breaking?

21. What is emery cloth?

22. Why are metals polished? Explain the operation.

23. What is rouge?

24. Explain the development of artificial grinding stones.

CHAPTER XXIV
TRANSMISSION OF POWER

320. Methods of Transmitting Power. — The power that
drives a machine is usually transmitted in 6ne of three ways:
(1) from a fly-wheel in the power house to a pulley on a main
line of shafting in the shop and then to another pulley on a
small shaft over each machine, called a countershaft; (2)
directly from the pulley of an electric motor, located in the
shop where it drives the main line of shafting; or (3) by
means of gears from a separate electric motor attached to
each machine. The first two methods are called power trans-
mission by shafting f and the third is called power transmission
by separate motor or "individual drive. "

321. Arrangement of Shafting. — The transmission of
power by shafting is accomplished by means of pulleys and
belts, or ropes attached to the shafts, which in turn are sup-
ported by hangers. Shafting consists of cylindrical bars of
steel or wrought iron from 13^ in. to 2*^ in. in diameter.
The different lengths of shafting are connected by a device
called a coupling. The shafting is supported by hangers
attached to the ceiling (Fig. 140) and revolves through an
opening in the hanger called a bearing. The part of the
shaft which rotates in the bearing is called the journal. The
bearing is encased in a soft metal called Babbitt metal, to
reduce the friction to a minimum. Babbitt metal is white
alloy of copper, tin, and antimony. The hardness of the

283

284 APPLIED SCIENCE

alloy increases according to the amount of tin which it con-
tains, the usual proportion being 8% tin and 9% copper.
The resistance to wear is sometimes increased by the addi-
■ tion of 2% phosphorus. The
' speed of shafting, that is, the
number of revolutions per min-
ute (abbreviated R. P. M.), is
governed by the type of machine
run by the shafts. This speed
varies from 125 to 150 R. P. M.
in metal-working shops to more

than 250 R. P. M. in wood-
Fio. 140.— Heavy Head Shaft , . ,

Hanger. working shops.

322. Formula for Horse-Power a Shaft Will Transmit-
To find the horse-power which a shaft of a given diameter will trans-
mit, multiply the cube of the diameter in inches by its revolutions
per minute and divide by 92 for steel shafts and by 190 for wrought
iron shafts. The quotient is the horse-power. To find the revolu-
tions per minute necessary for a shaft to transmit a given horse-
power, multiply the given horse-power by 92 for steel and 190 for
wrought iron and divide the product by the cube of the diameter
of the shaft expressed in inches. The quotient is the required
revolutions of the shaft per minute.

Considerable power is lost by the use of shafting and the average
loss would be about as follows. For each 100 H. P. generated, 10
H. P. is consumed by the friction of engine, 15 H. P. by the line-
shafting, 15 H. P. by the belts and pulleys, 15 H. P. by non-produc-
tive machinery, and only 45 H. P. goes for productive work. There-
fore every effort is made to reduce friction and waste to a minimum,
and shafts are usually adjusted every ten or twelve hours.

323. Setting Line-Shafting. — There are two points to be
considered in setting line-shafting in line. One is that it
should be either horizontally or vertically in line with its

TRANSMISSION OF POWER 285

journal; the other that the line-shaft and counter-shafting
should be in line with each other. Unless these precautions
are taken much difficulty will be experienced in the trailing of
the belts. One of the best methods of making sure that two
shafts are in line with each other is to place two slender reach
poles or rods of exactly the same length from one shaft to
the other at their opposite ends. The shaft may then be
adjusted until the distance is the same at each end.

324. Flange Couplings. — Line-shafting which is to en-
counter much shock and sudden variations of load must be
coupled with what are known as flange couplings. The dis-
tance between the hangers must be regulated by the number
of pulleys on the shaft. If the number is large the hangers
must be closer together.

325. Bending and Twisting of Shafting. — Shafts are
subject to bending and twisting. The bending is due to the
load strain of the pulley, while the twisting is caused by the
rotation of the shaft. Because it is liable to be rendered use-
less in this way, it is important that the shaft selected be of
a size suitable for withstanding the expected load.

326. Leather Belting. — Most belts used in machine shops
are made of oak-tanned leather (Fig. 141), but canvas is
sometimes substituted for leather belting. Single belts are
made from one thickness of leather or canvas, and are ^ of
an inch thick. Double belts are made from two thicknesses
cemented together, triple belts from three thicknesses, and
quadruple belts from four thicknesses. As a rule it is not ad-
visable to use anything but single belts on pulleys smaller
than 12 in. in diameter. Double belts, however, transmit

286 APPLIED SCIENCE

about 70% more power than single ones of the same width.
There are various formulas
given for finding the horse-
power that can be transmitted
safely, but a common rule
used by mechanics is: A single
belt one inch in width, running
at the rate of 1000 ft. per minute.

Fig. 141. — Oak-Tanned Leather will transmit one horse-power
e Ing " without making the belt so tight

that undue strain from journal friction wiU result.

327. Fastening Belts.— There are several methods of
fastening the ends of belts together. It is customary in the
ease of wide belts (8 in. and over) to fasten the ends by
cementing. Narrow belts are fastened by lacing, wiring,
hooks, or any one of the numerous forms of belt-fasteners on
the market. The smooth or hair side of a belt should run
next to the pulley with the flesh side out, as this latter side is
softer than the other. While belts must be made tight enough
to run the machine, they should never be tight enough to
strain the journal bearings, or excessive heat and wear will
result.

328. Sag of Belts. — When placing in position shafts that
are to be connected by belts, care should be taken to separate
them by a proper distance, so that the belt may be allowed
to sag a little when running. No arbitrary rule can be given,
as the location is the determining condition, but a general
rule may be stated as follows: Where narrow belts are to run
over small pulleys, a separation of 15 ft. is a good average, as
the belt may then have a, sag of about 2 in. For larger belts,

TRANSMISSION OF POWER 287

the shafts should be placed farther apart, say 20 to 25 ft.,

and a sag of 3 to 4 in. will be permitted. If possible, shafts

should be arranged so that the sag of the belt will increase

the arc of contact with the pulley.

If they are not so arranged, the

sag will lower the efficiency of the

belt.

329. Rope Drives. — Some-
times instead of a pulley, a wheel
with grooves on its circumference
(Fig. 142) is used for rope trans-
mission. The use of rope for the
transmission of power is more com-
mon in Europe than in the United
States. The advantages claimed for this method of power
transmission are:

(a) A larger amount of power is transmitted.

(b) A rope can be run in any direction or to any distance.

(d) Electrical disturbances are absent.

(e) Economy is obtained in first cost and in maintenance.
(/) There is an absence of slip.

For successful work the pulleys must be large in diameter
and must have a smooth surface where the rope bears upon
them. The speed and the load on the rope must be only such
as experience has shown to be economical. When these con-
ditions are fulfilled a rope drive is one of the most satisfactory
methods of transmitting power.

330. Measurement of Coiled Belting.— When belting is
purchased it is not necessary to uncoil it to determine its

288 APPLIED SCIENCE

length. It may be measured in the coil in the following
manner: To the diameter of the coil in inches, add the diameter
of the hole in inches; multiply by the number of coils in the belt
and multiply the resulting figure by .1309. The product will be
the length of the belt in feet.

Example. — How many feet of belt are there in a coil that is 22
in. in diameter? The hole is 4 in. in diameter and there are 48 coils.
22 + 4 = 26
26 X 48 - 1248
1248 X .1309 = 163.36, the Dumber of feet of belting in the coil.
If exact measurements are desired, it is necessary to get the average
diameter of the coil and the hole, and also any fractional parte of a
turn the belt makes in the coil.

331. Pulleys and Their Management. — Pulleys are made
of wood or steel (Figs. 143 and 144). They are measured by
their diameter and by the distance across the face or rim.

(a) Taper Cone Pulleys (6) Step Cone Pulleys

Fio. 143.— Wood Split Pulleys.

As the tendency of the belt on a pulley is to run to its highest
portion, the highest part of the face should be in the center
of the pulley, towards which the face should taper or crown.
It is the practice to crown pulleys with a taper of 34 i Q - per
foot or 1 in. per foot.

TRANSMISSION OF POWER 289

As shop machines are usually arranged so that they may be
disconnected from the power while the shafts are moving,
it is very important in
starting or stopping them
to avoid sudden jars or
changes, as such sudden
movements are dangerous
to the machine. To avoid
this danger a device, called
the fast and loose pulley
(Fig. 145), is used. This
consists of two pulleys
placed on the shaft, the
one being firmly fixed, and

the other loose so that it ^t^Jto^S^febS
may easily turn while the applied quickly to any shaft al-
... . j ready in place.

shaft remains at rest, or

vice versa. The belt is made to pass over either pulley by
means of a
forked guide;
if on the fast
pulley, the
machine
■ moves; if on
the loose pul-
ley, the ma-
chine remains

Fig. 146. — Countershaft with Fast ant* Loose Pulley

on Right. A shifting rod throws the belting from MO a „. ,„j

one pulley to the other. . 33 *' »peed

of Pulley —

The size of the pulley governs the speed of the machinery and

this speed is determined by the relative movements of the

290 APPLIED SCIENCE

pulleys and the ratios between their diameters and speeds.
Pulleys are usually arranged in pairs, each with a different
diameter and on a separate shaft. The mechanical prin-
ciple involved in a pair of pulleys is that of the wheel and
axle, the larger pulley being the wheel and the smaller one
the axle. (See Chapter V.) Since the belt running over
the two pulleys always runs at the same speed as their
rims, it is plain that the rims of both pulleys run at the
same speed. The pulley running the smaller number of
revolutions must be the larger of the two.

Take, for example, a 16 in. driving pulley making 180 R. P. M.
running with a pulley making 320 R. P. M. The rim of the 16 in.
pulley will travel in one minute a distance equal to 180 times its
circumference, or 180 X 16 X 3.1416, and the rim of the other
pulley will travel, if we call D its diameter, 320 X D X 3.1416.
Since the rims of the two pulleys will always travel at the same speed
we can put these two expressions equal to each other, or

180 X 16 X 3.1416 - 320 X D X 3.1416

and solving this equation to find D, we will have

^ 180 X 16 X 3.1416 ^ rt .
D , or D = 9 in.

320 X 3.1416

Now, according to the rule, we will have

16 X 180 = 9 X 320
or 2880 - 2880

which proves that the rule is correct.

333. Size of Pulley. — To illustrate the method of find-
ing the size of a pulley, suppose a shaft is to make 360
R. P. M. and that it is driven from a line-shaft making 180
R. P. M. The larger pulley on the line-shaft is already in

TRANSMISSION OF POWER 291

place and is 16 in. in diameter. What diameter should we
make the pulley on the shaft making 360 R. P. M?

Since we know the ratio of the speeds and diameters, we have the
proportion: Speed of small pulley is to speed of large pulley as
diameter of large pulley is to diameter of small pulley, or using
the same figures as above, we have

360 : 180 =» 16 : diameter of small pulley

The rule thus deduced is as follows:

The diameter of the driving pulley multiplied by its speed
equals the diameter of the driven pulley multiplied by its speed.

In practice it is found that a belt creeps or slips so that it
does not usually drive a pulley quite so fast as the calcula-
tions indicate. For this reason, the relative speeds of pul-
leys are only approximately exact and are always subject to
slight variation.

334. Object of Gears. — The liability of belts and ropes to
slip when transmitting heavy loads renders their use prac-
tically impossible when a constant ratio of velocity between
the driving and driven shafts must be maintained. In these
cases toothed wheels, called gearing, are usually employed.

335. The Principle of Gearing. — The principles under-
lying the design of gears may be best understood by con-
sidering the historical development of the gear. Originally
transmission of power in machines was carried out by two
smooth cylinders placed close together, as in Fig. 146, the
revolution and friction of one causing the revolution of the
other. Smooth cylinders, however, tend to slip when under
a load, so projections or notches were placed on their sur-
faces, as in Fig. 147. Here the diameters D and d are the

292

APPLIED SCIENCE

same size as on the rollers in Fig. 146. Teeth were simply
added to gear A and corresponding notches cut in gear B.
These two gears did roll together without slipping, but as the
teeth were short their points soon wore off. To overcome
such troubles, the teeth on gear B were made twice as long

Fig. 146.

Fig. 147.

emeus*
Fig. 148.

and the corresponding grooves or recesses in gear A were
cut twice as deep, as in Fig. 147. Today this is the de-
sign of the teeth. Gears are made by casting a blank wheel
and then cutting the teeth in the gear according to the above
design.

Note that the inside dotted circles in Fig. 148 are exactly
the same size as the rollers in Fig. 146 and are called pitch
circles. When the gears turn together they simply roll to-
gether on the dotted circles just as they would do if they had
no teeth.

Two gears represent the mechanical principle of the wheel
and axle. The large gear represents the wheel and the small
gear the axle. The most important part of gearing is the
relative movements of the gears and the ratios between their
diameters, their teeth, and their speeds.

When a small gear drives a larger one, the latter will
make fewer revolutions in a minute. Just the reverse is
true if a large gear drives a smaller one; i.e., the smaller
one will make fewer revolutions in a minute. The rate at
which a gear revolves is always proportional to the number
of its teeth.

TRANSMISSION OF POWER 293

As there are driver and driven pulleys, so there are driver
and driven gears. The driver gear and the driven gear
may be distinguished by the following characteristics: The
teeth of the former are bright or
worn on the front side — that is, the
side which faces in the direction of
the motion of the gear; the teeth
of the latter are worn on the side
opposite from the direction of

m0ti011 - „ hLW^-to.

Since gears are simply pulleys
with teeth on them, the principles underlying pulleys apply
to gears. When the teeth of two gears interlock they are
said to mesh.

336. Types of Gears. — Of the different types of gears in
use the principal ones are the spur (Fig. 149), the bevel {Fig.
150), and the worm (Fig. 151)
gears. Spur gears are wheels
with the teeth or cogs arranged
round the outer or inner sur-
faces of the rim, in the direction
of radii from the center, and their
action may be regarded as that of
two cylinders, rolling one upon the
other. Bevel gears are wheels the
, teeth of which are placed upon
the outer periphery (circumfer-

^ ..« m 7~„ ence) in a direction converging

Fig. 160. — Bevel Gear. ' . , °y

to the apex of a circle and their

action is similar to that of two cones rolling upon each other.

When two bevel wheels of the same diameter work together

294 APPLIED SCIENCE

at an angle of 45°, they are called miter wheels (Fig. 152).
The teeth are called teeth when they are of the same piece aa
the body of the wheel, and cogs when they are of separate
material. Wheels in whose rims
( ® U cogs are inserted are called mor-
tise wheels.

337. Teeth of Gearing.—
Toothed gearing is employed for
transmitting motion from one
shaft to another. Under favor-
able conditions it is the most
economical of all means of transmitting power from one shaft
to another, but when the twisting effort is very irregular and
the space between the teeth great, much noise arises from
them, due to the teeth striking against each other. This
striking is called backlash. When backlash is excessive it
reduces the life of the wheel, but is seldom so great, except
in much worn teeth, as to be a
source of danger. It should be
remembered that impulsive (sud-
den) loads produce twice the strain
on the teeth that dead (steady)
loads of the same magnitude pro-
duce, and that an impulsive load
may strain the teeth up to, or be-
yond, the elastic limit of the ma- Fia 152i _ MitoGeiri
terial. If stress of this kind is

repeated many, many times, the life of the teeth is greatly
shortened.

When the position of gears requires that they be installed
so as to operate noiselessly, the teeth of one made of wood,

TRANSMISSION OF POWER 295

or rawhide, are let into and fixed in the iron rim of the gear.
The gear so formed is termed a mortise gear, and is always the
quicker running gear of the pair. It is in such a case as this
that the teeth are termed cogs and they are usually made of
hornblende or beech, both of which are compact in grain and

take a smooth surface. Machine gears which are subject to
much vibration and shock are frequently made of phosphor-
bronze (an alloy of copper, tin, and phosphorus), gun-metal,
steel, or malleable cast iron, because these materials have a high
tensile strength and greater elasticity than ordinary cast iron.

338. Relation between Speeds and Diameter. — In the

mechanical world or in speaking of machines, the expression
"geared to 75" is often heard. This means that one turn of
the driving wheel will cause the circumference of the drive to
pass over 75 in.

To illustrate : A bicycle sprocket with a circumference of 30 in. and

80 8 oy
a rear wheel of 80 in. would give this ratio of speed: — =* - = 273;

30 3
i.e., one turn of the pedal would turn the rear wheel 2% times.
The gear of the wheel is found by multiplying this number by the
diameter of the wheel, say 27 in. ; 27 X i = 72 in.

The proportion between the speeds and the diameters of gears is
just the same as the proportion between the speeds and the number
of teeth. This means that we can find the ratio of the speeds of two
gears just as well if we know their diameters as if we know the num-
ber of their teeth. Suppose the diameters of two gears are 12 in.
and 24 in. respectively. Then the ratio of their speeds would be as
2 is to 1, if the 12 in. gear is the driver. If the 24 in. gear is the
driver the ratio would be as 1 is to 2; i.e., if the 24 in. gear is driving
and turns ouce, the 12 in. gear would turn twice. :

Sometimes it is easier to figure the ratio of the speeds of
gears from their diameters, but as the diameter used is the

296

APPLIED SCIENCE

diameter of the pitch circle and not the diameter outside of
the teeth, it is often hard to measure it exactly. For this
reason gears are usually classified according to the number of
teeth. As we can count the teeth we can get a more exact
answer when figuring their speeds than if we figured from
pitch circles.

339. Ratio of Gears. — Suppose we have two shafts, Dand F y as
shown in Fig. 153 and that we want to connect these shafts by gears
so that shaft D will make one revolution while shaft F makes two.

^ In order to do this we

"^K must place a gear on

/ ^i j *■» shaft D having twice

the number of teeth
of the gear on shaft F.
If we put a gear on D
with 24 teeth, the gear
on F will then have 12
teeth, or half as many,
and each time the gear
on D turns around
once the gear on F
will turn twice; that
is, the 24 teeth on
gear D will have to turn gear F twice in order to mesh with 12
teeth on F.

The relation of the speed of F to the speed of D is 2 to 1. This is
called the ratio of the gearing. We can now write the ratios be-
tween the speeds and the number of teeth in the form of a proportion
thus: 24 : 12 =2:1, that is, the number of teeth on gear D is to the
number of teeth on gear F as the speed of F is to the speed of D.

340. Direction of Gears. — The number of turns or revolu-
tions which a gear makes is always proportional to the number of
its teeth. It makes no difference how many gears there are
in a train, the gears between the first and last gear have

Fig. 153. — Ratio of Gears.

TRANSMISSION OF POWER 297

nothing to do with the speed of either of these two. That is
to say, the ratio between the speeds of the first and last gear
is not changed by put-
ting any number of gears
between them. The con-
tinued product of the
revolutions of the first
driver and the teeth of all

the driving gears is equal FlG . 154 ._T r ain of Gears,

to the continued product

of the revolutions of the last follower and the teeth of all
the driven gears. The formula for this is RDd=rFf. This
principle is true for any number of driving and driven gears.
The position of a driver does not affect the speed of the last
follower. Thus, either driver in Fig. 154 can be placed at D
or at d. Either follower can go on at F or at / without
affecting the speed of the last follower.

341. Gearing Terms. — There are certain terms relating
to gears with which the mechanic should be familiar. Some
of the most important of these are explained below. (See
Fig. 155.)

Spur. — Spur originally meant a projection or tooth, but is
now used to distinguish spur gears from other varieties of
gears, such as bevel gears and worm gears.

Pitch Circle. — The pitch circle of a gear is the distance
around the teeth and is the same size as the friction rollers or
cylinders would be if no teeth were present: i.e., when two
spur gears roll together their pitch circles are considered
to be constantly in contact.

Pitch Diameter. — The pitch diameter of a gear is the
diameter of the pitch circle.

298

APPLIED SCIENCE

Circular Pitch. — The circular pitch of a gear is the distance
measured along the pitch circle from the center line of one
tooth to the center line of the next.

WORKING DEPTH LINf

Fig. 155.

Diametral Pitch. — The diametral pitch of a gear is the
number of teeth per inch of pitch diameter. (For example,
if a gear has 30 teeth and its pitch diameter is 3 in., the
diametral pitch is 30 •*- 3 or 10.)

Addendum. — The addendum of a gear is the height of the
top part of the tooth, i.e., the distance from the pitch line to
the point of the tooth.

Dedendum. — The dedendum of a gear is the working depth
of the tooth below the pitch line. It is always equal to the
addendum.

Working Depth. — The working depth of the teeth of a
following gear is the depth to which the teeth in the mesh-
ing gear center into the spaces between the teeth of the first
or driving gear.

Clearance. — The clearance of a gear is the amount that the

TRANSMISSION OF POWER 299

tooth space is cut deeper than the working depth. (The
working depth of a tooth equals the sum of the addendum
and the dedendum, while its total depth equals the sum of
the addendum, dedendum, and clearance.)

342. Ratio of Gear Measurements. — Repeated designs and
tests of spur gears prove that the dedendum (or addendum) should
always have a certain definite ratio or relation to the diametral pitch
which is: dedendum times diametral pitch = 1, or, what is the same

-TOOTH

Fig. 156.

thing, dedendum = 1 -*- diametral pitch. This relation, of course,
holds true for the addendum, since the addendum and the dedendum
are equal. It is well to remember this relation, since the diametral
pitch is the most important thing to know about a spur gear and all
gears are ordered and made according to their diametral pitch. The
clearance is also referred to as the diametral pitch. Most gear-
makers use the Brown and Sharpe rule which is to make the clear-
ance times the diametral pitch equal .157; expressed as a formula
this would read :

F - .157 -f- P

Where F equals the clearance and P equals the diametral pitch.

Since we know that the outside diameter is equal to the pitch
diameter plus the two addendums, and since the addendum equals

300 APPLIED SCIENCE

1 -5- diametral pitch, we can make a formula for the outside diameter

which will read :

1 1

= D +- + -

P P

2
or, adding up, we will have = D H —

where = outside diameter, P = diametral pitch, and D = pitch
diameter.

Questions

1. State some advantages and disadvantages of the transmis-
sion of power by individual drive.

2. What is the mechanical principle involved in pulleys trans-
mitting power by belting?

3. What is the property of matter that allows the belt to turn
the pulley?

4. What kind of motion is illustrated in a rotating pulley?

5. Explain how Babbitt metal reduces friction.

6. Is f rictional electricity ever generated by the belt going over
the pulley?

7. Why is it necessary to have shafting of different diameters?

8. Explain two forces at work on a rotating shaft.

9. Is leather belting stronger than canvas?

10. Why is a pulley "crowned"?

11. Explain the difference between a pulley and a gear.

12. When is transmission by gearing preferred to transmission
by pulley and belt?

13. Name the common types of gears and explain their uses.

14. Explain the meaning of the following terms used in gearing:
diametral pitch, circular pitch, diameter of pitch circle, whole
diameter, bottom diameter, number of teeth, working depth of
tooth, velocity of gear, distance between centers of teeth, whole
depth of tooth.

Problems

1. One gear has 200 teeth and another 50 teeth. What is the
ratio of the diameters of their pitch circles?

TRANSMISSION OF POWER 301

2. Two gears have pitch circles of 85 in. and 17 in. in diameter
respectively. What is the ratio of their speeds? What is the ratio
between the number of teeth in their gears?

3. A 48-tooth gear drives a 120-tooth gear. What is the ratio
of their speeds?

4. Two shafts are connected by gears. One turns 55 times a
minute, and the other turns 11 times a minute. If the smaller gear
has 32 teeth, how many teeth has the larger gear?

5. Three gears of a train have 69, 30, and 74 teeth respectively.
If the 6&-toothed gear makes 100 R. P. M., how many R. P. M. will
the 74-toothed gear make? Figure the result and make a sketch
of the gears, showing by arrows the direction in which each turns.

6. A train of gears is made up of 6 gears having teeth as follows:
46, 60, 32, 72, 56, and 48. While the first gear in the train makes
10 turns, how many turns will the last gear make?

7. What two gears will give a ratio of speeds so that the driver
will make } f as many turns as the follower; in other words, while
the driver makes 13 turns the follower will make 14?

8. A horse used for moving a house walks around in a 12-ft.
circle pulling 800 lbs. on a capstan bar. If the drum of the capstan
is 24 in. in diameter, how much pull will the rope exert on the
house?

CHAPTER XXV
BOILERS AND THE GENERATION OF STEAM

343. Source and Characteristics of Steam. — The source
of energy used in driving many forms of machinery is the oil
or coal consumed — usually in the boiler-room of the power
plant. When this oil or coal is burned it gives off heat. The
heat converts water into steam, and the expansion of the

steam drives the engine. The steam

that issues from a steam locomotive

or from an open pipe of a power plant,

like the steam that is given off from

a kettle on the stove, is a watery

Fia.157. — Heating Water (aqueous) vapor and is always found
by Steam. The arrow ^T 1 ' . *7 A , 01

represents the passage when water is heated. Steam resem-

the 16 water St *Tte 'at- ' > ' es common *** an ^ other gases in
tachment is screwed many of its properties. It differs
onto the steam pipe. . . ,. , ., j , , .

from gases in that it does not retain

permanently its gaseous condition. For this reason it is not
called a gas but an aqueous vapor. The white cloud of vapor
noticed when steam is liberated is due to water particles in
suspension in the air.

The chief property or characteristic of steam is its elas-
ticity which makes it capable of enormous expansion.

344. The Boiler of the Steam Engine. — The principal
parts of a steam engine arc the boiler and the engine. The
boiler is a cylindrical steel vessel located over a fireplace.

BOILERS AND OENERATION OF STEAM 303

Both the boiler and fireplace are enclosed in fire-brick. Boilers
may be divided roughly into two general classes: water-tube,
and fire-tube boilers. The distinction between the two is
that in water-tube boilers water flows through the tubes and

Fio. 158.— Return Tubular Boiler.

the fire is on the outside of the tubes, while the conditions are
reversed in the case of fire-tube boilers.

The most widely used of all boilers in America and England
is the return tubular boiler (Fig. 158). This is a closed vessel
made of steel or iron, simple in construction, and easy to clean
and repair. The first horizontal tubular boilers were ordinary
iron storage tanks, 30 or 40ft. long and 48 to 56 in. in diameter.
This type of boiler frequently exploded at the girth seam over
the fires, and 50 or 60 lbs. was considered high pressure.

304 APPLIED SCIENCE

Steel instead of iron is used in the construction of modern
boilers. Although the average diameter of boilers has in-
creased only slightly and the average length has even de-
creased, the modern type is capable of carrying three times
as high a pressure as the old type. The diameters of modern
boilers range from 48 to 69 in., and the lengths from 16 to
20 ft., but a boiler carrying a pressure as high as 150 lbs.
per square inch is not at all uncommon; some carry even a
much higher pressure.

346. Water-Tube Boiler. — The water-tube boiler is the
result of a demand for high pressures of steam. In this type
— of boiler the water is

contained in tubes
which, on account of
their comparatively
small size, reduce the
thickness of metal,
the quantity of water
contained, and con-
sequently the total
weight of the boilers.
At the same time the
small tubes increase
the rapidity with
which steam can be
generated without in-
Fio. 159. — Marine Boiler. The tubes are jury from unequal
of small diameter and shorter than in . „, .

land type. Oil may be burned in this expansion. Water-

boiler. In this boiler the entire surface tube boilers are in
is composed of fire-brick.

extensive use for both
stationary and marine work (Fig. 159). They are more com-

BOILERS AND GENERATION OF STEAM 305

plicated, as a general thing, than some of the forms of fire-
tubular boilers and under the best conditions for each type
have not shown any particular increase in economy. This
type is claimed, however, to be the safer of the two because it
contains a less amount of water. When an explosion occurs
the tubes simply blow out. The cause is generally defective
welds or the thinning of the tubes from corrosion.

The common type of water-tube boiler is made of lap-
welded wrought iron tubes placed in an inclined position,
connected with each other and with a steam-and-water drum
on the top of the tubes by a vertical passage at each end. A
mud drum is connected to the rear and lowest point of the
boiler. The steam-and-water drums are made of sheets of
iron or steel of the desired thickness to withstand the pressure.
The plates are double-riveted. The mud drum is made of
cast iron, as this is the best material to withstand corrosion.

The tubes are fitted by an expander into drilled holes ac-
curately sized and tapering at the end connections. These con-
nections are in one piece for each vertical row of tubes. The
tubes are arranged so that each row comes over the space in
the previous row.

346. Boiler Building — Boilers 14 ft. or less in length are
constructed of two plates, each forming the entire circum-
ference. Above 14 ft. in length the shell is constructed in
three parts, i.e., three plates are required to make the length
of the boiler shell. These steel plates are J^, %, %, or ^
of an inch thick and range from 45,000 to 85,000 lbs. per
square inch tensile strength. They are ordered by the boiler-
maker from the steelmill usually 3^ in. larger than the
finished size required and they come to the shop perfectly
flat. Here they are first weighed to find out if they are up to

306

APPLIED SCIENCE

specifications in thickness. They are then placed on a bench
and laid out, " squared up" on the edges, and the location of
every rivet hole, nozzle, etc., is marked off with a soapstone
pencil. The rivet holes are punched 34 * n - less than their
finished size, then reamed full size, after which the plates are
brought to a planing machine and planed to the exact size
on the edges. Edges that are to be calked (pressed to-
gether by a compressed air hammer) are beveled (inclined
to an angle other than 90°), while the others are planed at
right angles to the surface of the plate.

The cylindrical shell of a boiler retains its shape without
the need of a brace or support for the very simple reason that
the internal pessure tends to keep it cylindrical. On the
other hand, this internal pressure has a constant tendency
to force or "bulge" out the flat surface of the heads of the
boiler which in consequence are reinforced by means of the
diagonal brace and stay-rods. The brace is used for low pres-
sure, and the stay-rods for high pressure. Stay bolts extend
from head to head. These bolts are often broken by the

unequal expansion of the

fire-box and outer shell.

(Copyrighted by Millers Pall Cos.)

Fia. 160. — Lap Joint.

347. Joints of a Boil-
er. — It is very important
that a boiler should safely
withstand the pressure of
steam for which it has
been constructed. Though
the tensile strength of the

boiler plate is marked on it, it is necessary to .test it when
the boiler is completed. When a rivet hole is punched, the
plate is weakened proportionally because a quantity of

o. ©.

©• Ca

©a qa

Ca Oa

Lfe

t_ —J,

BOILERS AND GENERATION OF STEAM 307

metal has been removed. Therefore an additional piece of
metal, known as a strap, must sometimes be placed around
such rivet holes to make up this deficiency to some extent.
At the present time, most fire-tube boilers made to generate
steam for engines have the
different portions of the shell
overlapping one another, as
shown in Fig. 160, and these
are held with a single row
of rivets. This arrangement
forms what is called a lap
joint. Lap joints are not
used to any great extent id Fkj _ iei.— Butt Joint.

joining the two ends of the

same sheet. In this case the ends are brought together and
one strap is placed on the inside and another on the out-
side, as shown in Fig. 161. This method forms what is called
a butt joint. These straps and the plate are joined by
riveting, as shown. If a single row of rivets is used on
each side of the joint through

\ l the outer plate, as shown at

j p ° — I J AA, it is called a single-riveted
j® ® ® ^^JS butt joint. If a double row is
I fi © © © 3 ) placed on each side of the
© O b 6 q| q joint through the outer strap,

i_ © ©__[ as shown in Fig. 162, it is called

' a double-riveted butt joint; if

[Copyrighted by Millers Falls Co.) ^^ ^^ ^ y^ j t fa ca [ led

Fki. 162.— Double-Riveted . . , - , . ... ...

Butt Joint. a triple-riveted butt joint.

348. Thickness of Boiler Plate. — The Boiler Inspection
Department of Massachusetts recommends the following

308 APPLIED SCIENCE

formula for determining the thickness of boiler plate:

PXRXFS

T =

TSX%

Where T = thickness of the boiler plate in inches.

P = boiler pressure in pounds per square inch.

R = radius (J^ diam. of boiler) in inches.

FS = factor of safety.

TS = tensile strength of the metal in pounds per

square inch.
% = strength of the joint.

The efficiency or strength of a joint is the percentage of the
strength of the solid plate that is retained in the joint. It
depends upon the kind of joint and method of construction.
If the thickness of the plate is more than J^ inch, the joint
should always be of the double-bolt type.

Example. — What thickness of plate should be used when making
a 40-in. diameter boiler to carry 125 lbs. pressure, if the strength of
the plate is 60,000 lbs. per square inch, using a factor of safety of 6,
and 50% as the strength of joint?

125 X 20 X 6 w

T = = Y 2 in. sheet

60,000 X .50

To find the safe working pressure use the following formula, where
the letters have the same significance as in the previous formula:

_ TS X % X T
R XFS

Example. — Find the safe working pressure of the same boiler.

p = 60,000 X .50 X .5 = ^ Ibs
20 X 6

BOILERS AND GENERATION OF STEAM 309

349. Testing Boilers for Defects. — Boilers are tested ia
two ways: (1) by hydraulic pressure, and (2) by the hammer
test. The hydrostatic teat consists in filling the boiler with
water and then exerting by means of a boiler test-pump (Fig.
163) one-half more pressure than the boiler is expected to
carry. For instance, if it is expected to carry 100 lbs. pressure,
it is tested up to 150 lbs. The hammer test is made by going
over the boiler and tapping it with a small hammer. An
experienced ear can tell by the sound of a blow and by the
feel of the
iron whether a
weakness has
developed.
Corrosion and
strains from
expansion and
contraction
are liable to
cause a de-
crease in the

strength of . r »- m - M " r *"**"■*

steam boiler. Corrosion, which may be either internal or
external, is the wasting away of the material of the boiler
by pitting, grooving, etc. Internal corrosion is mainly caused
by the action of oxygen, minerals, or acids in the water,
External corrosion takes place generally through rusting and
from the action of sulphur in the fuel. Under certain con-
ditions this sulphur attacks the metal when the boiler is
"starting up" or "cooling down," a time at which the gases
are much reduced in temperature.

Boilers should be fed with hot water. Cold water tends to
reduce the temperature of the water already in the boiler,

310 APPLIED SCIENCE

particularly in the parte near the opening of the feed pipe,
causing these parts to contract. This contraction strains the
seams and the plates more or less severely, according to the
temperature and volume of the water introduced. Draughts
of cold air have the same effect, often resulting in leaky tubes
and seams.

360. Boiler Repairs. — Boilers may be repaired by placing
a hard or soft patch on the defective part. For a hard patch,
the defective part is cut out, rivet holes are drilled or punched
around the opening, and the patch is applied and calked. A
soft patch is made by placing a piece of boiler plate over the
place that threatens to give way. The plate is held in place
with 5^ or % in. countersunk screw bolts. A piece of sheet
packing covered with red lead is often put under the patch, or
the red lead is used alone.

351. Principal Parts of a Boiler. — The principal parts of
a boiler are the shell, tubes, fusible plug, hand-hole, safety
valves, and water gauge. The shell and tubes have already
been explained. A fusible plug is a
brass plug with a tapering center of
Banca tin (Fig. 164). The large end
is put next to the pressure to prevent
the soft metal from blowing out. This
plug is screwed into the rear head of a
boiler not less than 2 in. above the top

—Fusible Plug.

row of tubes, and extends 1 in. into

the water to prevent its becoming
scaled. If the water "shrinks" below this plug the soft
metal melts, allowing steam to escape, and thus giving
timely warning.

BOILERS AND GENERATION OF STEAM 311

The manhole, through which it is necessary to enter to
inspect the inside of the boiler, is cut in the top or in one
of the heads, and is made steam-tight by a rubber gasket.
Hand-hole plugs are located in the bottom of the front and
rear heads for the purpose of permitting the boiler to be
cleaned. The blow-off is connected, at the bottom of the shell
at the rear end, with a valve on the pipe outside of the brick-
work called the blow-off valve. This valve is designed to
empty the boiler and should be used every morning, so that
the sediment that has settled at the bottom of the boiler over-
night may be blown out. The boiler should be emptied and
washed out at least once a month.

352. Safety Valves. — As the cylinder of the boiler is made
to stand a certain pressure, any excess may cause it to burst.
Therefore it is essential that the fireman should know when
that pressure is exceeded. Various devices have been de-
signed to give the fireman warning. Among these are the
safety valve, the pressure gauge, and the water gauge.

A boiler usually has two safety valves, a water gauge, and
a pressure gauge. The function of a safety valve is to relieve
the boiler of all pressure in excess of that allowed. The valve is
placed at the top of the boiler and piped outside. As it often-
times becomes corroded and sticks, it should be tried every day.

The size of the safety valve is a very important matter,
and is determined by the area of the grate, the weight of fuel
burned, and the steam pressure. The amount of steam gen-
erated in a given time will depend upon the weight of coal
burned, while the velocity of escape through the valve will
depend upon the pressure. Low pressure safety will not run
higher than 30 lbs. The figure stamped on the lever shows
the limit.

312

APPLIED SCIENCE

A lever safety valve (Fig. 165) consists of a disk, a stem, and
a lever with a weight hung on the end. The weight keeps
the valve in its place until the steam pressure under the valve

overcomes that of the weight
and some of the steam es-
capes. If it were not for the
safety valve, boiler explosions
would be much more fre-
quent.

(Copyrighted by Millers Falls Co.)

Fig. 165.— Safety Valve.

363. Construction of
Safety Valves. — Calculations
for lengths of arms and

weights required for any boiler pressure are obtained from the
formulas for levers, taking into account the weight of the
lever and valve.

The center of gravity is the point at which the lever and
valve attached to it will just balance over a balancing bar
(bar with knife edge). The fulcrum is at the center of the
pivot on which the lever works.

Where F
W

VI =
L =

P
A

Then

the fulcrum on which the lever works.

weight of ball in pounds.

distance in inches from fulcrum to center of

gravity,
weight of valve and lever in pounds,
distance between ball and center of fulcrum in

inches,
distance between fulcrum and center of valve in
inches.
= boiler pressure per square inch.
= area of safety valve in square inches.

Trr A xP Xl -(VlXg)

W =

BOILERS AND GENERATION OF STEAM 313
AxPxl - (VI X g)

Example. — At what distance from the center of fulcrum must a
weight be placed, if the bailer pressure is 100 lbs., weight is 16 lbs.,
area of valve is 3 sq. in., and valve and lever weigh 16 lbs., center
of valve is 2}^ in. from fulcrum, and center of gravity is 12 in. from
fulcrum?

8X100X2K-P6X12) nHh

354. Water Gauge. — The function of the water gauge
(Fig. 166) is to register the height
of the water in the boiler. It
consists of a small cast iron drum
placed in an upright position in
front of the boiler, provided with
a glass gauge, cocks, water and st
connections. Pipe connections
arranged so that steam enters the
and water enters the bottom. W
gauge and cocks are essential to
safety of the boiler and should
blown out frequently to prevent i
ging. Water should stand half-
way in a gauge glass cock while
working, and at night should be
raised to the top gauge cock.
The first duty of a fireman in
taking charge of his boiler is to

see i! the water is at a proper F '«' ™ -W.K, G.uge.
level. To tell if the glass is registering correctly, the gauge
cocks must be tried. The water column should be blowu

314 APPLIED SCIENCE

out at least once a day, and sometimes three or four times,
depending upon the quality of the feed water. The gauge
cocks should be opened after blowing out the water column
to see that the level in the glass coincides with the level indi-
cated by the gauge cocks. The water has to be kept at about
the same height all the time, and the engineer can tell
whether it is right or not by opening the gauge cocks. One
of these is below the water line, and one is above it. If the

Fig. 167. — Cross-Section of a Boiler Pump.

water in the boiler is right, steam will come out of the upper
one and water out of the lower one; if it is too low, steam
will come out of both.

356. Boiler Pumps and Injectors. — A boiler should have
at least two means of feeding water, because one might fail
to work. The water inside a boiler is usually kept at a proper
level by either pumps or injectors. Steam pumps (Fig. 167)
are most commonly used on stationary and marine boilers,
and may be classified as boiler-feeders, general surface
pumps, tank pumps, or water-work pumps.

BOILERS AND GENERATION OF STEAM 315

The steam pump is commonly used in power plants ;to
supply feed water to the boiler. It is very important for
the engineer in charge of the plant to see that the pumps
supplying the steam boilers are in first-class order at all
times, as any failure to maintain the water at a proper level
in the boilers may result in serious injury to the boilers; an
explosion may even occur.

One end of a boiler pump is called the engine or steam end
and the other the pump or water end. A boiler-feeder is
intended to feed water into steam boilers while they are under
pressure. To illustrate: If the boiler is under a pressure of
100 lbs. to the square inch, and the steam piston in the pump
receives 100 lbs. to the square inch, it is clear that there will
be equilibrium between the steam pressure and water pres-
sure of the pump. This is overcome by reducing the plunger
diameter to perhaps one-half the size of the steam piston.
In this way an unequal area in the steam piston and pump
plunger is obtained. This difference enables the pump to
force water against a pressure greater than that of the
boiler. The necessary allowance for friction varies from
5 to 40%.

When a pump takes in water at only one end of the piston,
it is called a single-action pump; when it takes water in at
both ends, it is called a double-action pump.

All single, direct-acting pumps make use of an auxiliary
plunger to carry a valve which gives steam to the main pis-
ton. By means of various devices, steam pressure is made to
drive this auxiliary plunger backward and forward.

356. Measurement of Pump Pressure and Capacity.—

The formula for lifting or forcing water either under pressure
or head is as follows: P = HAW.

316 APPLIED SCIENCE

Where H = the distance from the level of the source of

supply to the point of discharge.

A = area in square feet of surface in contact with
the water.

W = weight of a cubic foot of water, or 62. 5 lbs.

Example. — What is the pull on a pump rod, when the diameter of
a bucket is 6 in. and water is raised 20 ft.?

6* X .7854

P = HAW = 20 X X 62.5 = 245.437 lbs.

144

From the above solution we find that the pull on the pump rod is
245.437 lbs. ; to this must be added the amount of power necessary
to overcome friction.

357. Measurement of Water Cylinder Contents. — To find
the cubical contents of a water cylinder per stroke, in cubic
inches, multiply the area of the piston in square inches by the
length of stroke in inches. To find the contents in gallons
divide this product by 231, and to find it in cubic feet divide
the product by 1728.

Example. — What is the capacity per hour of a single-action pump
with a water piston 6 in. in diameter and a 10-in. stroke, when the
piston makes 60 strokes per minute?

If the water cylinder is filled at each stroke, the contents are
AxL = (6x6x .7854) X 10 - 28.274 X 10 = 282.74 cu. in.

At 60 strokes per minute there will be 60 X 60 = 3600 strokes per
hour. If the piston pumps 282.74 cu. in. per stroke, then for one
hour it will pump

282.74 X 3600 = 1,017,864 cu. in. per hour
or 1,017,864 + 1728 - 589 cu. ft. per hour

or 1,017,864 -4- 231 = 4406.33 gal. per hour

To find the H. P. required to pump water to a given height,
multiply the weight in pounds of water to be raised per minute

BOILERS AND GENERATION OF STEAM 317

by the height in feet and divide by 33,000; the quotient will
be the H. P. required. The formula is:

W XH

H. P. =

33,000

Example. — Find the H. P. required to pump 4406.33 gal. of water
per hour to a height of 40 ft. above the source of supply.

If a pump will raise 4406.33 gals, of water per hour, it will raise
4406.33 -*• 60, or 73.438 gals, per minute; and as 1 gal. of water
weighs 8% lbs., 73,438 gals, weigh 73.438 X 8% or 611.983 lbs.
This weight of water is to be raised 40 ft. high. Then by formula :

W X H 611.983 X 40 24,479.32

xl. Jr. = = = = ./41 xl.-T.

33,000 33,000 33,000

358. Injectors and Ejectors. — The injector (Fig. 168) is
an apparatus for forcing water against pressure by the direct
action of steam on the water. It is universally used on loco-
motive and sometimes on stationary boilers. Steam is led
from the boiler through a pipe, which terminates in a nozzle
surrounded by a cone. This cone-shaped pipe is connected
with the water tank or well where the wat.er is stored. When
steam is turned on, so as to pass into the injector, it rushes
from the nozzle and thereby creates a partial vacuum in the
cone. Since this pressure in the cone is now less than the
atmospheric pressure in the water well, the water is forced
up to the cone. As the steam meets this water it condenses,
but not before its force has imparted enough of its velocity
to the water to give the latter sufficient momentum to force
down the valve that prevents the steam and water of the
boiler from escaping. An injector does not work well if the
feed water is too hot, as in that case the steam does not con-
dense quickly.

318 APPLIED SCIENCE

An ejector is similar in form and operation to an injector,
but is used to lift water without forcing it against pressure.
An inspirator is a
double - jet injector;
one jet lifts the water,
and the other forces it
into the boiler.

359. Water-Heat-
er. — Before entering
the boiler, water is
heated in a heater by
exhaust steam. This
heater consists of a
vessel filled with brass
tubes. Steam passing
through or around the
Fig. las.— Injector. tubes causes the tem-

perature of the water
to be raised. This process prevents steam from condensing in
the boiler as it wou|d if cold water entered. Moreover, the
salts are deposited in the boiler instead of in the heater. An
economizer is a device consisting of iron or steel tubes through
which feed water passes while the products of combustion
circulate around the tubes. A steam separator is used to
remove moisture from steam before entering the engine
cylinder. A steam trap is a device to remove condensed
steam from steam pipes without allowing any of the live
steam to escape.

A damper regulator is an apparatus f or regulating the damp-
er and controlling the draughts by the pressure of steam on the
boiler. This regulator has the power to move the damper or

BOILERS AND GENERATION OF STEAM 319

dampers in both directions by water pressure, and will close
or open them on a variation of one pound of steam. It makes
a partial stroke and stands at any point; that is, it will move
from the open position to one-quarter, one-half, three-quar-
ters, or fractions thereof, and come to and remain indefinitely
at a state of rest, and then return to the open position, thereby
making the only true and proper movement of the damper.

360. Cleaning the Boiler. — When the water is heated and
converted into steam, the sediment or suspended dirt remains
in the boiler and forms scales. These scales are composed
principally of mineral matter and affect the economical gen-
eration of steam by preventing the water from coming in
contact with the plates and tubes. The latter are then
heated to a much higher temperature than would otherwise
be necessary and to too high a temperature for the good of the
metal. Thick scales on the surface of a boiler cause unequal
expansion of the plates and tubes, resulting in leaky tubes and
seams, and largely accounting for blisters and bagging.

Various methods have been invented for removing and pre-
venting scale. Kerosene oil removes oil scale very effectually.
About half a pint of kerosene oil per day fed continuously into
the feed water will be found sufficient to remove scale as fast
as it can be taken care of by cleaning the boiler, and without
danger of accumulating and causing serious overheating.
Scale may be to some extent prevented by the use of a good
compound, provided the water has been analyzed and the
compound which has been prepared particularly for that
water is used. Mechanical boiler cleaners may also be used
with good effect, but with any method a boiler should be
thoroughly cleaned at regular and frequent intervals. Boiler
tubes also should be cleaned often. The soot that collects

320 APPLIED SCIENCE

in them is a non-conductor of heat, and, therefore, when the
surface of the tubes is covered with soot only a portion of the
heat of the gases passing through them can get to the water
surrounding the tubes. The remainder is carried to the
chimney. In a boiler tube, a layer of soot Y% in. thick will
cause as much waste of fuel as ifo in. of scale. When burning
bituminous coal, soot will collect to the above depth in about
ten hours. Therefore, in order to have reasonably clean tubes
at all times it is necessary to clean them once each day.

361. Care of Boiler. — The boiler should be inspected
frequently during construction, and when completed should
be thoroughly tested. After the boiler is in position and the
brickwork completed, it should be allowed to stand, if possible,
for a week in order to give the brickwork a chance to dry and
set. After this it may be filled to the proper level and a small
fire kept burning under it for a few days. Great care should
be taken at this time not to heat up the boiler and brickwork
too quickly.

In starting up a new boiler, it is a good plan to put a few
pounds of sal soda in the water, and then, after the brick-
work is well dried and set, to let down the fire and steam, run
off the water, and give the boiler a good washing out. This
treatment will be found to prevent the foaming which so often
occurs when a new boiler is started. This foaming is caused
by the grease left in the boiler by the boiler-makers.

The fireman who has charge should at all times, before
starting his fire, see that the water in the boiler is at the
proper level. He should not be satisfied by merely looking
at the water glass, but should open the cock at the bottom of
the glass, and also try the gauge cock. Many accidents have
occurred through neglect of this duty. He should also see

BOILERS AND GENERATION OP STEAM 321

that the blow-off cock is in order and closed, that the ash pit
is clear of ashes, that the tubes are clean, and that the safety
valve is raised off its seat, or that some valve or cock is open
to the atmosphere until steam issues from it. The grate
bars should be covered with coal from the bridge wall toward
the furnace door for about 3 ft. The fireman should then
put some light wood on the grate in front of the coal and with
a little oily waste set fire to it. When the fire has thoroughly
kindled the wood a little coal may be put on it. During this
time the ash pit should be closed and the furnace door left
open a little so that the flames may be communicated to the
coal at the back of the furnace.

As soon as a good fire is burning in the front of the furnace,
the front coals may be pushed back a little and the ash pit
damper opened. The fire should not be forced, but should
be allowed to work up gradually. An unequal strain through
forcing the fire when the boiler is cold may cause leakage and
make expensive repairs necessary. The fires should be main-
tained level and of a uniform thickness, but the thickness
must be determined by the demand for steam, the condition
of the chimney draught, and by the quality and nature of the
fuel.

362. Firing the Boiler. — Firing can best be done when
combustion is good, as but little dense smoke then is given
off. Dark spots in the fire, abundance of smoke, unsteady
steam pressure, unsteady water line, dirty tubes, and coal in
the ash heap are all evidences of careless firing, and should
not be tolerated. Experience is the only guide to the best
methods of handling the different kinds of fuel under the
different conditions to be met with in practice.

The coal should be put in lightly at regular intervals in

322 APPLIED SCIENCE

order to fire the green coal in the front of the furnace and
to allow the smoke to pass over a bed of incandescent fuel at
the backj and be consumed. Later the coal in front may be
pushed back and new coal added to take its place.

Side-firing, i.e., keeping one side of the fire always brilliant
while firing green coal on the opposite side, works very well.
No established rule, however, can be set for every condition,
and much must be left to the judgment of the fireman in each
individual case. When firing or cleaning fires where the
chimney draught is very strong, it is advisable to check the
stack damper to prevent too great a quantity of cold air
entering the furnace and causing undue contraction of the
plates. In boilers having a large furnace, it is well when
cleaning fires to clean one side at a time.

The feed water should be kept constantly on, and the water
line maintained at the proper level all the time. Every day
the steam pressure should be raised to the blowing-off point, so
that the fireman may know that the safety valve is in work-
ing order. If at any time, from any cause, the gauge should
show the pressure increasing rapidly up to or past the limit,
the feed should at once be put on and the draught checked.

363. Chimneys and Flues. — A chimney is a vertical flue,
usually of iron or brick, for conveying the heated air and
combustion gases from the fire to the outer air. It usually
extends some distance above the tops of buildings. The
height of the chimney determines the intensity of the draught.
The capacity of the chimney depends upon its height and
area. A draught may be natural, induced, or forced.

A natural draught is produced by a chimney alone, and is due
to the difference between the weight of a column of the hot
gases inside the chimney and an equal column of air on the

BOILERS AND GENERATION OF STEAM 323

outside. To illustrate: The air entering the furnace may
haye an average temperature of 62° F., while that in chimneys
often has a temperature of 500° F. A cubic foot of air at 62°
weighs .0761 lbs., and at 500° it weighs .0413 lbs. The heated
air is therefore .0348 lbs. lighter than the average air.
Hence its rapid passage to the smoke-stack and the conse-
quent draught. The length of stack or passageway has much
to do with the rapidity with which the smoke travels. On
every square foot of the cross-section of a 100-ft. stack, there
is at the bottom an upward pressure of 100 times .0348 lbs.,
or 3.48 lbs.

Induced draught is obtained by placing a fan-blower at or
above the boilers. The uptake from the boiler is connected
to the inlet of the blower and the outlet is carried to the chim-
ney, discharging the gases and heated air into the chimney.

Forced draught is obtained by conducting the discharge of a
powerful blower to the ash pit, the air being forced through
the fire.

364. Theory of Combustion and Smoke. — Smoke is a by-
product of the combustion of fuel, and is invariably the result
of incomplete combustion. It is composed chiefly of minute
particles of carbon and steam, and is due largely to an excess
of air admitted to the fire, although in a few cases the produc-
tion of smoke is due to an insufficient supply of air. If the
boiler is not crowded and the draught is good, the volume of
smoke will be reduced by first allowing the coal to coke in
front of the grates and by then pushing it back over the bright
coals. The hollow bridge wall, with suitable means for regu-
lating the supply of air, also gives good results where there
is a strong draught. A small grate area and a very hot fire will
reduce the volume of smoke, as will a very large grate area

324 APPLIED SCIENCE

and a slow fire, although the former arrangement is the more
economical.

An economical manner of banking fires is to push the live
coals back against the bridge wall, leaving the forward part
of the grates covered with ashes only, then covering the live
coals with a moderately thick layer of fresh coal. Fine coal
is preferable as the air does not readily pass through it, es-
pecially when the draught is diminished by closing the damper;
this should be done just before covering the fire with fresh
coal. The damper should be left open a very little to avoid
the accumulation of gas in the furnace and the possibility
of an explosion. This method of banking fires saves much
time when preparing to start again. The grates may be
quite thoroughly cleaned without disturbing the low fire at
the bridge wall.

In case the water level becomes dangerously low, the fire
should be drawn immediately. The engine should continue
to run, and water should not enter the boiler in any quantity.
When the furnace has cooled down to about the same tem-
perature as the boiler, the water level may be raised very
gradually until water appears in the glass. The boiler may-
then be filled more rapidly and the fire* started.

365. Temperatures of Steam. — Af ter steam has been once
generated, the temperature remains constant, and the latent
heat, not observable by the thermometer, is absorbed. The
temperature of steam in contact with the water from which
it is generated depends upon the pressure. If the vessel is
closed, as in boilers, the pressure becomes greater and raises
the boiling point of the water. Steam under pressure and
confined has considerable energy due to heat, which is
measured, as already noted, by the heat unit, B. T. U.

BOILERS AND GENERATION OF STEAM 325

When the steam is taken directly from the boiler to the
engine, it is termed saturated steam and is generated in con-
tact with its water of generation.

When the boiler is overworked, the steam, due to the vio-
lent action of its generation, takes with it particles of water.
Such steam is called wet steam. Dry steam contains no
watery moisture; it may be saturated or supersaturated.

Steam from the boiler, heated to a higher temperature by
passing it through a vessel or coils of pipe separated from the
boiler, called a superheater, is termed superheated steam.
Steam loses heat as quickly as it acquires it, and so every
passage conveying superheated steam should be well covered
with non-conducting material.

366. Terms Used in Calculations. — One should be famil-
iar with a number of terms which are frequently used in
calculations.

Heating surface means all surface having water on one side
and fire or heated gases on the other.

Grate surface means the surface of the grate bars, or the
area of the surface which supports the burning fuel.

Steam room is the space above the water line, or all the
space in a boiler not occupied by water.

Horse-power. There is no such thing as the horse-power
of a boiler. The term horse-power refers to the measure-
ment of power or energy produced in a given time. A boiler
does not produce energy; therefore, the work of a boiler
cannot be measured by horse-power. Energy is the product
of a given force in pounds multiplied by the distance in feet
through which it moves; horse-power is obtained by dividing
the energy thus obtained in one second by 550; in one minute,
by 33,000; and in one hour by 1,980,000. A boiler contains

326 APPLIED SCIENCE

a force only. Therefore the term horse-power is merely rela-
tive, and when applied to a boiler conveys to the mind the
horse-power of an engine which a boiler of a given size is
capable of supplying with steam.

Priming is that process by which the water is carried up
into the steam pipes in considerable quantities and frequently
over into the engine. The most common cause is a high
water line, which may be the effect of a faulty boiler design.
Too many tubes, the forcing of a boiler, irregular firing, or
sudden opening of the stop valve may also cause it.

Questions

1. Trace the energy used in a steam boiler from its original
source.

2. Why is steam considered an aqueous vapor and not a gas?

3. Describe the properties of steam.

4. What properties of steam are common to gases?

5. What is a boiler?

6. Describe the two classes of boilers.

7. Explain the manufacture of boilers.

8. Why is a boiler cylindrical and not square?

9. State the advantages of water-tube boilers.

10. State the advantages of return tubular boilers.

11. How are boilers tested? Explain the principle underlying
each method.

12. What objection is there to adding cold water to boilers?

13. How are boilers repaired? What is the difference between
a hard and a soft patch?

14. What are the principal parts of a boiler?

15. What is a fusible plug? Why is it used?

16. Why is a manhole elliptical and not circular?

17. What are the devices used on a boiler to tell when the maxi-
mum pressure is exceeded?

18. Describe a safety valve; pressure gauge; water gauge.

19. How is water fed into a boiler?

BOILERS AND GENERATION OF STEAM 327

20. Describe an injector. State the principle on which it works.

21. Describe a water injector.

22. Describe a water heater.

23. What is a damper regulator?

24. Why is it necessary to clean a boiler? How is it cleaned?
26. Describe the steps in starting a fire in a new boiler.

26. Describe the steps in firing a boiler.

27. What is a chimnev?

28. Explain the theory of combustion and smoke.

29. Define the following terms : saturated steam ; wet steam ; dry
steam; supersaturated steam; heating surface of a boiler; horse-
power of a boiler; priming.

CHAPTER XXVI
THE STEAM ENGINE

367. History of the Steam Engine. — The steam engine
is one of the most important mechanical contrivances used
in trade and industry. With its discovery came the great
industrial development of the world. The first steam engine
was invented by James Watt in 1781. For a long time he
seems to have been practically the only engine-builder doing
business and his patents probably prevented others from
entering this field until about the beginning of the nineteenth
century. The steam engine of today is the controlling feature
of our industrial civilization. It furnishes the motive power
for all our factories, and without it scarcely one of the articles
we use in every-day life could be produced in sufficient quan-
tity to satisfy human needs.

The steam pressure of the first engines was very low. Watt
ran his engines with a pressure of only seven or eight pounds
more than atmospheric pressure. The boiler pressures in
current use have steadily risen during the past century as
better materials and better workmanship made higher pres-
sures safe and advisable. Today 125 lbs. per square inch is
a very common pressure for ordinary stationary engines;
150 to 175 lbs. pressure is frequently met with in large power
plants; and in special cases 200 lbs. pressure is employed.
This increased pressure, of course, enables the steam engine
to yield a much larger output of power per ton of total weight
and the limit is not yet reached. As it has been possible to

32$

THE STEAM ENGINE 329

increase boiler pressures, bo also the working parts and the
structure of steam engines have been improved and strength-
ened, until now the weight of engine per horse-power of capac-
ity and the cost of the plant are much less than in Watt's time.

368. Principal Parts of Steam Engines. — The principal
parts of a simple engine (Fig. 169) are the' frame, cylinder,

Fia. 169.— Steam Engine.
A— Cylinder D — Steam Inlet G — Crank

B— Piston E— Steam Porta H— Slide Valve Eccen-

C— Slide Valve F— Exhaust Port trie

piston, rods, eccentric, crank shaft, governor, and wheels.
The cylinder is the long, round, iron barrel or tube in which
the piston works. The piston is a disk, fitting into the cylin-
der and dividing it into two compartments. Packing rings
are provided to make it steam-tight. The piston moves back
and forth, forced by the steam which is alternately admitted
on each side of it by means of openings called ports. That
is, steam is allowed to enter the cylinder by one port, and
forces the piston along, the other port being opened by the
slide valve into the exhaust port during this stroke. As soon
as the piston has reached the end of the cylinder, the first
port closes for the admission of steam, while the second port

330

APPLIED SCIENCE

admits steam which pushes the piston back again to its
original position.

The back and forth movement, thus imparted to the piston
by the steam, is transmitted to the crank and then to the
heavy fly-wheel. The fly-wheel by means of belting or rope
transmits motion to the smaller wheels or pulleys which drive
the machines in factories.

After moving the piston, the steam either escapes into the
air, as it does in the case of a steam locomotive, or passes into
one or more other cylinders where it exerts its force until it
condenses. An engine that allows steam to escape into one
cylinder only, is called a simple engine. If the steam expands
twice it is called a compound expansion, and if it expands
three times it is called a triple expansion.

369. Purpose of a Governor. — The governor (Fig. 170)
of a steam engine is a device which controls the supply of

steam by letting iDto the cylinder just
the right quantity. In the pipe which
carries the steam from the boiler to
the cylinder is a valve called the
throttle valve, by which the com-
munication between boiler and engine
may be opened or closed. A rod con-
nects this valve to the governor,
which is made to turn round by a
belt from the crank shaft. The faster
the crank shaft turns the faster the
governor goes round. At the lower
end of the governor are two heavy
balls, so hung that as the speed of the governor increases they
swing out farther from the center rod and as it slows dqwn

Fig. 170. — Governor.

THE STEAM ENGINE 331

they swing nearer to it. This action of the balls is due to
centrifugal force. It opens and shuts the throttle valve by-
raising and lowering the rod which leads from the governor
and in this manner the supply of steam is regulated. If the
engine moves too fast, the balls of the governor swing out,
and this pulls on the rod and partly closes the valve, shutting
off some of the steam; if it goes too slowly the balls swing
inward and thus open the valve and let in more steam. Thus
the speed of the engine is regulated by the governor.

The speed of the governor should be carefully adjusted,
and all its parts kept clean and in perfect working order.
When this is done, the engine will always run at a uniform
speed, no matter what load or work is on at any time. If any
machine is suddenly thrown out of action, the governor should
at once control the speed of the engine by cutting off the
supply of steam. On the other hand, when a heavy load
comes on more steam is admitted by the governor, and thus
the speed of the engine is kept nearly constant or uniform.

370. Crank. — The "crank" is a mechanical device em-
ployed for converting the parallel or reciprocating motion of
the piston into a rotary motion. It is connected by a key to
the shaft, which carries the fly-wheel. The power trans-
mitted to the crank exactly represents that exerted by
the steam in the cylinder against the piston, minus the
friction.

Between the piston and crank, connection is made by
means of a cross-head and connecting rod; the cross-head
runs to and fro between guides. This motion of the cross-
head is necessary to prevent the piston rod from being broken
or bent by the oblique positions of the connecting rod when
the crank is at mid-travel. The distance from the center of

332 APPLIED SCIENCE

the shaft to the center of the crank pin is called the crank's
throw, and is half the piston stroke.

371. Dead Center. — When the piston rod is fully out or
fully in, and the connecting rod and the crank in consequence
lie in a straight line, the crank is said to be at a dead point or
dead center. When the crank is in this position the admission
of steam will not produce motion since the thrust would be
absorbed by the bearings. A locomotive engine must be
constructed so that it may be started in any position. In
order that this may be done the engine must have at least
two cylinders, and the cranks must be set at an angle to one
another, so that when the crank of one is at a dead point the
other has reached a position where it exerts its maximum
turning power.

372. Steam Valves. — The steam is admitted into the
cylinder of an engine by means of valves, as previously stated.
There are three distinct types of valve — (1) slide, (2) Corliss,
and (3) poppet valves.

The slide valve is a simple casting similar in its lengthwise
section to the letter D. By being moved back and forth over
the steam ports of the engine it admits and exhausts the
steam alternately, thus causing the piston in the cylinder to
work back and forth.

Corliss valves are semirotary valves, cylindrical in shape,
which partly turn in cylindrical chambers.

Poppet valves are simply disks attached to a stem, which
work over a circular opening. They are raised and lowered
over the parts.

The mechanism controlling these valves is called the valve
gear.

THE STEAM ENGINE 333

373. Condensing Engines. — Non-condensing or high-
pressure engines are less economical than condensing or low-
pressure engines, because they use much more steam. When
the waste steam is let out of the cylinder, the air rushes in and
takes its place. This air presses hard against the piston so
that it takes power to drive it down.

After the steam is condensed in the condensing engine
there is a vacuum, or an empty space, on one side of the pis-
ton, so that but little fresh steam is necessary to drive it.
Thus the object of condensing is to do away with the back
pressure on the piston and thereby increase the mean effec-
tive pressure. There is a gain of 20 to 33 % % in economy,
depending on the size and type of engine. In small engines
the saving is not enough to be considered.

Where fresh water is scarce, it is of great importance to
the marine engineer to condense the steam by leading it into
a condenser when it has finished moving the piston. In this
process the steam as it leaves the cylinder enters a condenser
and passes over a number of copper tubes, through which sea
water is circulated by means of a pump. The steam is thus
condensed into water and a vacuum is created. Since this
water is warm, it is pumped into a hot-water well, whence a
pipe leads it to a pump, which in turn carries it back to a
boiler.

374. Installation of Pipes. — In installing pipes and metal
fittings of all kinds it is absolutely necessary to make proper
provision for expansion. (See Chapter IX, " Heat and Ex-
pansion.") When steam is turned on the temperature is
raised and the pipes expand. Pieces of curved pipe called
bends are usually used to take up the expansion and prevent
the joints from leaking. When steam is suddenly admitted

334 APPLIED SCIENCE

to a pipe partly filled with cold water, the water is set in
violent motion and travels the length of the pipe in the form
of waves often with sufficient velocity to break a valve or
other obstruction in its path. The extent of the break will
depend upon the manner in which the valve is opened. If
opened suddenly, a violent explosion is almost certain to
follow, but if opened very gradually, while there may be a
certain amount of noise and vibration, no serious results will
occur.

Engines are usually placed in a house separate from the
boiler, although it is a good plan to have them near so as to
avoid the necessity of laying great lengths of steam pipe.
Steam pipes are made of wrought iron or steel with flanged
joints. The pipes conducting the steam from the boiler to
the engines are covered with non-conducting material, such
as asbestos, to prevent the escape of heat. Draw-off cocks
are placed in convenient positions along the pipe to draw off
the water formed from condensed steam.

375. Alignment of Pipes. — When pipes are not in a
straight line, they are said to be out of alignment. Want of
alignment sometimes causes trouble by throwing excessive
strains on the flanges at the joints of stop valves, separators,
etc. This trouble is brought about, as a rule, by forcing the
flanges together by means of their joining bolts instead of
fitting them carefully into place. The flanges of modern steel
pipes and valves are usually of ample thickness, and if they
do not come together fairly, they should be taken down and
replaced. A thin ring of metal may be put in to make up the
length, if necessary.

When erecting heavy pipes, every length of piping should
be placed in position and properly supported and leveled

THE STEAM ENGINE 335

by its own slings and brackets. Then it will usually be
found that several lengths have to be altered before the
flange faces come into alignment. Not until this has been
done and every pair of flanges inspected by some responsible
person, should the various lengths be bolted together per-
manently.

When a number of small or moderate-sized engines are
connected with the same pipe system and stand on the same
foundation, or in the same building, it is sometimes difficult
to prevent the pipes from vibrating and at the same time
insure the necessary freedom for expansion and contraction.
Installations of this kind should therefore be arranged in
such a way that the pipes are quite free to move in one direc-
tion, parallel with their length, while movement in other
directions should be restricted so far as possible.

High-speed engines are those whose fly-wheels rotate at a
high speed; i.e., make a large number of revolutions per
minute. Such engines are less expensive to operate than low-
speed engines, because the power of an engine depends upon
area of its piston, the mean pressure of steam, and the speed
at which its fly-wheel rotates. Therefore by doubling the
speed, an engine may be built very much smaller and cheaper
per horse-power. Engines of this type are used for driving
electrical machinery, which requires high speed of rotation
and uniform angular velocity.

376. Horse-Power. — The power of a steam engine is com-
monly designated as horse-power. One horse-power is a force
strong enough to raise 33,000 lbs. one foot high in one minute; this
has been found to be about what a very strong horse could do
working 8 hrs. a day. An engine of 100 H. P. would be, of
course, able to do a hundred times as much as this. A steam-

336 APPLIED SCIENCE

boat of 1000 tons generally has an engine of 360 H. P. A
man-of-war usually has one horse-power for every ton.

There are several kinds of horse-power referred to in the dis-
cussion of a steam engine; nominal, indicated, and actual or net.

Nominal horse-power was a term used during the invention
of the steam engine to express the amount of work an engine
could perform during a given time.

Indicated horse-power is obtained by multiplying the mean
effective pressure in the cylinder in pounds per square inch,
by the speed in feet per minute, and dividing the product by
33,000.

Actual or net horse-power is the difference between the
indicated horse-power and the amount of horse-power ex-
pended in overcoming friction.

Example. — What is the horse-power of an engine that can pump
68 cu. ft. of water from a depth of 108 ft.?

1 cu. ft. of water = 62}^ lbs.
68 X 62^ - 4250 lbs.
4250 X 108 = 459,000 f t.-lbs.

459,000 153

—L « — . 13H H.P. - 13.9 H.P.

33,000 11

377. Corrosion of Pipes. — If the feed water contains lime
salts, a deposit will be formed in the economizer and feed
connection which will more or less effectually protect the
pipes from internal corrosion ("rusting" or "eating away").
If, however, the water is very free from lime, and air is intro-
duced by the feed pump, internal pitting (small hollows) will
be formed. Considerable damage may then be done before
the danger is discovered and steps taken to prevent further
mischief.

THE STEAM ENGINE 337

External corrosion does not as a rule give much trouble,
but under certain conditions the combined action of heat and
moisture on asbestos pipe-covering will set up pitting. This,
however, can be prevented by painting the pipes with any
good graphite paint before the covering is applied.

378: Piping Material. — For all ordinary and high pres-
sures used in connection with land boilers, steel pipe is almost
invariably adopted, the longitudinal joints being lap-welded.
Cast steel is largely employed for bends and elbows, although
copper is used in high-class work. Many old plants with
pressures up to 100 lb. per square inch are working with
cast iron pipes. On board ship, pipes are usually made of
copper.

Pipes of small diameter are generally solid drawn, but
many steam pipes on board ship are made with brazed joints.
In their construction, makers usually allow a factor of safety
varying from 10 to 15 tons per square inch, assuming the
copper to possess an ultimate tenacity of about 15 tons per
square inch.

Steam pipes expand and contract about one inch in fifty
feet, through variation of temperature. It is best to allow
for this movement, when possible, by arranging springing
lengths, so that the whole arrangement may be elastic. When
there are long lengths between fixed supports, expansion
sockets are sometimes adopted. These, however, should
always be fitted with guard bolts, to prevent the pipe from
being accidentally drawn apart.

Steam pipes should always be kept free from water, and
drain taps should, consequently, be fitted wherever necessary.
Should an accumulation of water accidentally occur in a long
horizontal length of pipe, its drainage under steam pressure

338 APPLIED SCIENCE

is very liable to cause fracture. Therefore drainage should
not be attempted without first isolating the boilers so as to
minimize the danger.

379, Turbines. — We have already seen the uses of water
wheels or water turbines. Steam turbines (Fig. 171) consist

of a wheel with blades. ■ The
steam, in the form of jets, strikes
against the blades and moves
the wheel. This machine was
invented to overcome the back-
ward and forward (reciprocat-
ing) movement of the piston,
which jars and shakes the en-
gine.

Steam turbines utilize the
kinetic energy of the steam. As
steam at the usual pressures em-
ployed has a very low density,
a cubic inch of steam must have
F.«. I71.-Steam Turbine. a yery Mgh velodty jf j t » to

expel any considerable amount of kinetic energy.

380. Action of Steam in a Turbine. — In entering the
turbine, steam acts in two ways, and turbines are accordingly
constructed on two plans. The more important type and
the only one to be described here, is the impulse turbine, in
which the steam from the boiler is completely or almost
completely expanded into an expanding nozzle. As the
steam forcibly strikes the vanes of the wheel, the turbine
wheel rotates at a very high velocity. This is illustrated in
the De Laval turbine which is used in place of the ordinary

THE STEAM ENGINE 339

steam engine in the generation of electric power, or in
the transmission of any other form of energy derived from
steam.

The working of the De Laval turbine is as follows: The steam is
blown through stationary divergent nozzles where it is allowed to
expand to the pressure of the exhaust chamber. Each particle of
steam, which moves very rapidly, strikes against a concave vane or
plate which projects from the drum like a spoke. This causes the
wheel to move rapidly. The outer end of the buckets are covered
by a ring which prevents the centrifugal escape of the steam. The
nozzles vary in number and can be closed independently of each
other, so that the number in use may be made to suit conditions of
running.

As the material composing the turbine machine limits the speed at
which it can safely be run, it is necessary to have some form of re-
ducing gear in the transmission. The smaller types of De Laval
turbines run at about 30,000 R. P. M., and are geared down to about
3000. The larger sizes run at about 10,000 R. P. M. under gear.
Even with all the disadvantages of gearing, the turbine is used ex-
tensively in units ranging from V/2 to 200 H. P.

Its principal parts are the shaft, drum, cylindrical case inside of
which the drum revolves, vanes on the drum and cylindrical part,
balance pistons.

381. Measurement of Work in Heat Units. — Experiments
show that one unit of heat is equivalent to 772 ft.-lbs. of
work, and when this quantity of work disappears in friction,
one unit of heat is generated. Other experiments show that
the unit should be 778 ft.-lbs. It is not of much importance
which number is used; some use one, and some use the other,
but all agree in naming this quantity of work after the dis-
coverer of the relationship, James P. Joule of Manchester,
England. The unit is therefore called Joule's equivalent, or
the mechanical equivalent of heat.

340 APPLIED SCIENCE

Example. — One pound of good coal gives out on complete com-
bustion, 14,500 B. T. U. of heat. Find the amount of work stored in
one pound of coal.

Units of heat X Mechanical equivalent = Work in foot-pounds.

14,500 X 772 = 11,194,000 ft.-lbs.

Questions

1. Who invented the steam engine?

2. What effect has the development of the steam engine had
upon trades and industry?

3. What is a steam engine?

4. What property has steam that allows it to drive a piston?

5. What is the purpose of the fly-wheel?

6. Why is a fly-wheel large and heavy?

7. What kind of motion has the moving piston of an engine?

8. What kind of motion has the fly-wheel of an engine?

9. How is the motion of the piston communicated to the fly-
wheel?

10. Why is it desirable to have the escaping steam enter a con-
denser?

11. What is a condensing engine?

12. What is a non-condensing engine?

13. What is the eccentric of an engine?

14. What is the governor of an engine?
16. What is the efficiency of an engine?

16. How is the power of an engine expressed?

17. What is a rotary engine?

18. What is a turbine?

19. What advantage has the turbine over the reciprocating
(straight-line) engine?

20. Explain how a turbine works.

21. Explain the measuring of indicated horse-power.

Problems

1. What is the H. P. of an engine that is required to pump out in
8 minutes a basement 51 ft. X 22 ft. X 10 ft. deep, full of water?

THE STEAM ENGINE 341

2. What is the H. P. of an engine that is capable of raising
3 tons of coal (2240 lbs. to the ton) from a mine 289 ft. deep in 3
minutes?

3. How many tons of coal can an 8 H. P. hoisting engine raise
in 34 sec. from the hold of a coal barge, a distance of 61 ft.?

4. How long will it take a 10 H. P. hoisting engine to raise an
812-lb. ram of a pile-driver to a height of 23 ft.?

5. How many pounds of water per half-minute can an 8 H. P.
pump raise to a height of 86 ft.?

6. If 1 lb. of coal gives off 15,337 B. T. U. of heat, find the
amount of work stored in 1 lb. of coal.

7. If 1 lb of coal gives off 14,897 B. T. U. of heat, find the
amount of work stored in 1 lb. of coal.

8. If 1 lb. of coal gives off 15,111 B. T. U. of heat, find the
amount of work stored in 1 lb. of coal.

CHAPTER XXVII
METHODS OF HEATING

382. Starting a Fire. — In countries where the winters are
cold it is necessary to deyote a great deal of time and labor
to the heating of dwellings. Heat is usually obtained by the
burning of wood, coal, etc. Such substances are called fuel.
The harder the fuel, the more difficult it is to kindle. Coal is
harder to light than wood because of its density, which in-
creases the difficulty of raising it to the temperature which is
necessary for burning. If the heat of another fuel, such as kin-
dling wood, be applied to the coal in sufficient quantity and
long enough to ignite it, it will then produce a fire much more
powerful and much more durable than will the lighter fuel.
Lighter fuel kindles easily, but the mixture of air in its pores
causes it to burn out rapidly. Hence the heat it produces is
but temporary, though often very strong. The usual method
of getting rid of the smoke from a fireplace is through a
chimney.

383. Methods of Heating. — Modern buildings and houses
are heated by stoves, steam, hot water, or furnaces. The
choice of any particular method will depend upon special
conditions and requirements. Heat is given from a stove by
radiation (Fig. 172) ; that is, the stove becomes hot, due to the
burning of coal, and the metallic parts radiate the heat. A
stove is not an economical means of heating, because much
of .the hot air goes up the chimney and is wasted. Moreover,

342

METHODS OF HEATING

343

\A/,

/»

to heat a home it is necessary to have a stove in each room.
A large furnace in the cellar overcomes these drawbacks, and
is consequently used in most houses. From the furnace, hot
air is distributed through ducts to
the different rooms. Such a fur-
nace draws in fresh outside air
and passes it into a dome over
and around the hot coal. As the
air becomes hot, it expands, and
thus makes its way to the several
rooms.

Steam radiates its heat with
ease, and also condenses very
rapidly. Heat given off by a
steam furnace is called steam
heat and may be provided direct-
ly or indirectly. Direct heat is given off by radiators in the
room to be warmed, while indirect heat is supplied by dis-
tributing throughout the building air that has been warmed
by passing over radiators in the basement.

Wood and coal stoves, gas heaters, steam and hot-water
radiators, coils of heated pipe, and electric resistance heaters
are all examples of direct radiation. The air in a room is
heated over and over again, and fresh air is admitted usually
only by leakage around doors and windows or by the opening
of one or the other.

Fig. 172.— Heating by Stove.

384. Steam Heating. — Steam for heating (Fig. 173) is
obtained from a boiler fitted with coils of pipe. As the steam
passes through the radiator it gives off its heat and is con-
densed into water. This water flows back into the boiler,
either through another return pipe or through the same pipe.

344

APPLIED SCIENCE

The double-pipe system requires greater length of piping, but
the single-pipe system requires larger piping, so as to allow

the condensed water to
return to the boiler while
the steam is ascending
the pipe.

385. Indirect Meth-
od. — The indirect method
of heating (Fig. 174) is
the more effective system
for large buildings and
schools. The heater is
generally placed in a
cellar or basement. The
air is passed over its sur-
face of pipes, and is then
directed by a distributing
system of sheet iron or tin
pipes up into the rooms
to be warmed. Heating
has the effect of circulat-
ing the air in the conduct-
ing pipes. The air may,
too, be forced into the cir-
culating pipes by a blower
„ „ . „ or fan located in the cel-

Fig. 173. — Steam Heating System.

lar. The well-known hot-
air furnace is an example of the indirect method of heating.

386. Advantages and Disadvantages of the Indirect
Method. — One great advantage of the indirect system is that

METHODS OF HEATING 345

there is always some ventilation. New air is always entering
the rooms, while at the same time the older air must make its
escape around windows and doors, or pass out through flues
built into the walls of the building for this purpose.

Ideal ventilation is not often secured, however, even by
indirect heating, for the air that comes from a cellar is not
always pure and fresh. It is
more often dusty and odorous
from the refuse or decaying
matter which frequently lies
about a cellar. To overcome
this difficulty, the air should
be brought in from outside the
building by means of an air-
tight flue or box. The inlet to
the box should be carried up
high enough outside of the
building to avoid drawing in
litter and dust and should be
covered with a strong wire-
mesh screen to keep out rats. In many public school heating
systems the outside air, before entering the heater, is purified
by being passed through a water-spray curtain.

387. Exhaust Steam Heating. — Exhaust steam from an
engine is often used for heating. The water of condensation
from an exhaust steam heating plant is frequently allowed
to run to waste, but as its temperature is near boiling, coal is
saved if the water is collected in a receiver and pumped back
into the boiler. Mill engines that are run "with condensers can-
not furnish exhaust steam for heating. In such a case, live
steam must be taken from a branch opening in the main steam

346 APPLIED SCIENCE

drum in the boiler-room. This requires the use of a reducing
valve to let the pressure down between 5 and 15 lbs. for the
heating coils. A receiving tank is necessary for the return
water, and a pump must be installed to force it back to the
boilers. Some mills have spare boilers that are used only for
heating purposes. These may be run at a low pressure, 10 lbs.,
and the steam may be passed directly into the heating system
without the use of a reducing valve. When the return water
is piped directly to the feed pipe of the boilers we have what
is known as a gravity return system. Since there is the same
pressure in the heating system that there is in the boiler, the
water of condensation runs back into the boiler simply by its
own weight. This requires that all heating pipes be on a
higher level than the water line in the boiler. If any radiators
or coils were lower than the boiler, they would, of course, fill
with water, and a pump would be required to return the water
from the low coils to the boiler. The gravity return system
is used in many dwellings, office buildings, churches, and
stores

388. Low-Pressure Steam Heating. — When steam at
atmospheric pressure is condensed into water at a tempera-
ture of 212° F., each pound of steam gives up 966 B. T. U. of
heat; but if steam of 100 lbs. gauge pressure (115 lbs. absolute)
is condensed into water at 212° F., each pound of steam must
give up 1004 B. T. U., which, is only 38 heat units more than
are contained in steam of atmospheric pressure. It is evident
from this that for heating purposes there is no advantage in
using steam of a high pressure. One pound of exhaust steam,
only a pound or two over atmospheric pressure, is almost as
valuable an agent for heating purposes, as live steam at 100
lbs. pressure direct from the boiler*

METHODS OF HEATING 347

389. Gas for Heating Purposes. — Gas, both natural and
manufactured, is used extensively for heating. It burns with
either a blue flame or yellow, luminous flame, depending upon
the type of flame device or burner which is used. The yellow
flame is suitable only for fireplaces or portable heaters and its
burner must be kept cleaned and regulated so that no smoke
or soot is given off. Since blue-flame gas heating appliances
do give off smoke and soot they are usually connected with a
flue or set in a fireplace that has an effective flue.

The blue flame is hotter than the yellow flame because it
is the product of perfect combustion, while particles of un-
burned carbon are floating about in the yellow flame. The
burners of blue-flame heating appliances are usually provided
with an air shutter by which the quantity of air which mixes
with the gas within the burner can be regulated. If a large
amount of air is admitted the number of carbon particles
is increased and the result is imperfect combustion. The
shutter should be opened sufficiently so that the flame above
each burner opening will have a sharply defined inner blue or
bluish green cone. This indicates that an adequate amount
of air is mixing with the gas in the burner.

If the air shutter is too wide open the gas may "fire back"
and burn within the burner itself. When the gas burns inside
the burner, combustion is incomplete and dangerous products
of partial burning are given off. The improper burning of the
gas within the burner is sometimes called " lighting back " and
is accompanied by a roaring noise. When this unusual noise
is heard the gas should be turned out at once and, after a
moment, lighted again.

390. Hot- Water Heating. — A hot-water heating system
(Fig. 175) operates by the movement of hot water from the

348

APPLIED SCIENCE

boiler to radiators, where it gives off heat. The colder water,
which has already given off its heat, Teturns to the boiler to
become reheated. By the circulation of water, heat is con-
veyed from the boiler to the room..
The movement of the water is due
to the fact that hot water is
lighter, or in other words its
density is less, than cold water;
hence it will rise and more cold
water will come in to take its
place. This movement will con-
tinue so long as there is a differ-
ence in temperature in the system.
One sq. ft. of heating surface is
required for 30 to 60 cu. ft. of
space heated.

391. Air Circulation. — The
circulation and ventilation of the
air in a room is necessary in any
method of heating. Warmed air
rises to the top of a room and
the cooler air settles nearer the
floor. A steam radiator warms
the air directly in contact with it
and this air therefore rises. Cold

Fig. 175.— Hot-Water Heating »» t^ 8 ite P lace and is in
System. ^urn warmed. The temperature

of the air in the room gradually rises until the air, walls,
ceiling, and furniture or machines have all been warmed. A
certain amount of heat is lost through the walls, ceiling, and
windows, and there is always a leakage of cold air into a room

METHODS OF HEATING 349

through cracks at windows and doors. This loss of heat
outwards and cold air leakage inwards increases as the differ-
ence between the temperature of the inside and outside air in-
creases. Double-windows, storm-doors, building-paper under
shingles, clapboards, and plastering tend to check these losses.

392. Radiators and Radiation. — Radiators are made up of
hollow sections of cast iron. The outer surfaces are so shaped
as to give the greatest possible area or, as it is generally
called, the greatest radiating surface. The castings for
radiators are purposely made rough, and are often elaborately
figured in pleasing designs, so as to present a larger radiating
surface than would be the case if they were smoothly finished.
The transfer of heat from hot metal surfaces to air is more
efficient if the radiating surface is rough and the color is dark.
Radiators are sometimes gilded for appearance, but practi-
cally they do not heat as well as if left ungilded. A cheap form
of radiator for stores and shops is cast with innumerable pro-
jecting plugs or pins.

For large rooms a radiator may be made up of pieces of 1 in.
or V/i in. pipe joined together by elbows and return bends.
Such a radiator is called a box coil. A more common method
of installing a direct radiation system is to run a group of
1J4 in. steam pipes along the side of a room and around the
corner, by means of couplings to provide for expan-
sion and contraction, and to connect the ends of the run
into branch trees. The advantage of this arrangement is
that it distributes the heat throughout the whole length of
the room.

In a dwelling house the radiators are generally placed near
the windows, since the cold air then reaches the radiators
quickly. The direction of the flow of air 1 along the floor is

350 APPLIED SCIENCE

•

towards the windows. Pipe coils in mills may be run along the
walls on brackets under the windows. The cold air dropping
downwards from the windows meets the current of warm air
rising from the coil and is tempered and warmed at once.
When it is desirable to have the hot-steam coils near the
working space they are generally hung from the ceiling near
the outer walls. This plan works well in a shop or mill where
there are shafts with whirling pulleys and belts in constant
motion. The air is churned by such motion and the heated
air is brought downward and mixed with the cool. In office
buildings and stores, coils placed near the ceiling are not
effective, for there is nothing to cause circulation and the
warm air naturally tends to remain at the top of the room.

393. Measurement of Heat Radiation. — The quantity of
heat given off by radiators or steam pipes, in the ordinary
methods of heating buildings by direct radiation, will vary
from 1% to 3 heat units per hour per square foot of radiating
surface for each degree of difference in temperature. An
average of from 2 to 2 l /i heat units is a fair estimate.

One pound of steam at about atmospheric pressure con-
tains 1146 heat units. If the temperature in the room is to be
kept at 70°, while the temperature of the pipes is 212°, the
difference in temperature will be 142°. Multiplying this by
2}/£, the emission of heat will be 319J^ heat units per hour per
square foot of radiating surface. A boiler must always be
capable of generating as much steam as the radiators arc
condensing. There should be 1 sq. ft. of heating surface in the
boiler for every 8 to 10 sq. ft. of radiating surface.

394. Main Piping. — All piping must be carefully put up,
and horizontal piping must have a pitch or slope of 34 to 3^

METHODS OF HEATING 351

in. in 10 ft., so that the water will flow out of the system as
quickly as possible. A low place or sag in the pipes or heat-
ing coils may trap the water. The result will be that a noisy
snapping or hammering will take place when steam is turned
on.

The pipe coils are hung on rollers to allow for expansion.
After the first heating season in a new building, and occasion-
ally in all buildings, the piping system should be examined.
The shrinkage and settling of doors may throw pipes and
radiators out of place sufficiently to cause serious trouble in
the action of the system.

The rule for finding the size of the main steam pipe is:
Divide the amount of the direct heating surface in square
feet by 100; divide the quotient by .7854; then take the
square root of this last quotient. The result will be the
diameter of the pipe in inches. (Pipe area = -^77 of
heating surface.)

395. Risers and Returns. — Risers are the pipes that pass
from the lower floor to the upper floors and to which the
radiators are connected by short pipes or nipples. These
connections must allow for expansion, and it is advisable to
put a valve into the lower end of every riser. By taking the
steam from the top of the main, less water enters the riser.

Returns are the pipes that receive the water of condensa-
tion from the coils and conduct it back to the boiler room.

396. Steam and Air Valves. — A heating system, when
cold, fills with air by leakage around valve stems. This air
must be allowed to escape so that steam may enter. Auto-
matic air valves may be placed on every radiator and coil.
These valves are open when cold. As steam enters the sys-

352 APPLIED SCIENCE

tem, the air escapes ahead of the steam and finally when
steam reaches the air valve, the heat of the steam expands a
plug in the valve, which thus closes automatically. As the
air valves often get out of order, it is a great convenience to
run small 34 i n * pipes from each radiator to the boiler-room.
The engineer can then open each air pipe until steam appears.
When this happens he can be certain that the coils are
working properly.

397. Steam Productions from Water. — The weight of
water required to make 1 cu. ft. of steam at any pressure is
the same as the weight of 1 cu. ft. of steam.

Therefore, the weight of water is obtained by multiplying
the number of cubic feet of steam required by the weight of
one cubic foot.

Example. — How much water will it take to make 300 cu. ft. of
steam at 100 lbs. absolute pressure?

One cubic foot of steam at 100 lbs. pressure is given as weighing
.2307 lbs. Therefore, 300 cu. ft. will weigh 300 X .2307, or 69.21
lbs. of water.

One cubic foot of water may, for any practical purpose, be
reckoned to weigh 62J^ lbs., and the weight of one gallon of
water may be taken as S-^s lbs. Therefore, 69.21 lbs. divided by
62.5 gives 1.1 cu. ft., or 69.21 divided by 8.3 gives 8.34 gals.

At atmospheric pressure one cubic foot of steam has nearly
the weight of one cubic inch of water, and the weight increases
very nearly as the pressure; therefore, the rule: Multiply
the number of cubic feet of steam by the absolute pressure in
atmosphere and the product is the number of cubic inches of
water required to give the steam.

In all such calculations, for practical purposes, a liberal
allowance must be made for loss and leakage.

METHODS OF HEATING 353

Questions

1. What is fuel?

2. Is a hard (dense) fuel difficult to kindle?

3. Why is it harder to light coal than wood?

4. What is smoke?

5. How is smoke removed from a fire?

6. What principle of science causes a draught?

7. Explain the method of heating by a stove.

8. Explain the method of heating by steam.

9. Explain the method of heating by hot water.

10. Explain the method of heating by a furnace.

11. What is meant by the indirect method of heating?

12. Is it possible to use exhaust steam for heating? Explain.

13. What is low pressure heating?

14. Explain why heating and ventilation go hand in hand.

15. Why are radiators rough?

16. Where are radiators usually placed?

17. How is heat radiation measured?

18. Why should steam pipes be examined after the first season?

19. What are risers? Returns?

20. Describe the valves used in steam heating.

CHAPTER XXVIII
VENTILATION

398. Object of Ventilation. — Ventilation is the process of
removing from an enclosed space foul air, laden with im-
purities, and replacing it with fresh air. An exact displace-
ment, however, does not always take place. The incoming
fresh air may merely dilute the foul air to a point suitable for
healthful breathing. The standard of pure air is taken as
that existing in the open country; it contains about four
parts of carbon dioxide (C0 2 ) per ten thousand of air and
is free from dust. An increase of two parts of carbon dioxide
is accepted as the standard of pure air. Any excess above
this is considered impure air. Badly ventilated rooms often
contain as many as 80 parts of carbon dioxide per ten thou-
sand of air.

399. Methods of Ventilation. — There are three ways of
removing dust and impurities from air in a building: (1) the
natural method; (2) forced ventilation by means of fans, and
(3) the exhaust method.

Natural ventilation is produced through doors and windows.
The air in a room is changed by this method about three
times an hour. If there is a fireplace in addition, the total
number of changes per hour will be about four. A furnace
will produce five changes of air per hour. Every room should
be large enough to allow proper ventilation without too much
draught. Authorities agree that not less than 300 cu. ft. of
air space should be allowed for each person.

354

VENTILATION 355

Heating by a hot-air furnace and by the indirect method of
steam heating necessarily involves the movement of air, and
therefore insures that the room will be ventilated.

Forced ventilation is produced by forcing the air into a
building with a fan or blower. Such a fan operates by means
of the centrifugal force of a paddle wheel which sends the air
off the edge of the blades.

Exhaust ventilation is that in which fans are placed at the
top of the house, or ventilating flue, thus lessening the pres-
sure within the building by producing a slight vacuum.

400. Waste Products. — The waste products of life and
industrial processes that interfere with indoor occupations are :

(a) Carbon dioxide and moisture from the lungs and skins
of animals.

(6) The products of combustion from lamps, gas burners,
aad other artificial lights.

(d) Irritating and poisonous dusts and gases.

The human body is constantly giving off heat, carbon
dioxide, and perspiration. The heat is due to the chemical
combination of the oxygen in the air we breathe with the
carbon of the body. The products formed are heat and car-
bon dioxide. The heat given off keeps the temperature of
the body at about 98 2 / 5 ° F. As we are constantly breathing,
there is a continual supply of heat which would increase the
temperature of the body above normal, unless it were radi-
ated in this manner to the air and surrounding objects. Some
of the heat is given off to the air in immediate contact with
the body, by conduction, and some is lost by evaporation and
perspiration.

356 APPLIED SCIENCE

401. Perspiration. — Perspiration • consists of water
charged with waste products. This water is evaporated
from the skin by the air. If the air is saturated with moisture,
as it often is during the summer, water does not evaporate
quickly and consequently perspiration does not evaporate at
its usual rate. As a result we sweat or perspire very freely.
When we fan ourselves we create a small breeze which quickly
evaporates or absorbs the perspiration.

Moisture is, however, readily taken up by dry air, and a
consequent cooling results. But if the atmosphere has a
humidity of 100 per cent, as it has just before or after rain,
the perspiration cannot be evaporated since the air already
has all the moisture it can hold. Everyone has noticed that
when the sun shines on a hot day just after a rainfall, the
heat is almost unbearable.

402. Noxious Gases. — Operatives who are exposed to
irritating or poisonous gases and fumes, such as lead and its
compounds, are likely to become victims of chronic poison-
ing. Gases that are merely irritating are of less import-
ance than those that are poisonous, because irritating gases
cannot be borne in large amounts and the person suffering
from their effect is forced to seek the relief afforded by
fresh air.

Offensive vapors and fumes, such as those given off in soap-
making, glass-making, tanning, and rendering, etc., may
cause general disturbance of the digestive system and head-
ache for a time to those who are not used to their effects, but
as a rule, tolerance is soon established and the odors are not
even noticed. These odors are popularly regarded as leading
to infectious disease, but this is not true, as they do not, in
reality, undermine the human system.

VENTILATION 357

403. Dust. — In the emery, corundum, sandpaper, and
allied industries, great attention is given to keeping the dust
away from the mouth and nostrils of the workmen by means
of hoods and exhaust fans. Oftentimes workmen remove
their hoods recklessly and thereby expose their lives to dan-
ger. There are two or three times as many deaths among
grinders, polishers, and cutters due to disease of the lungs
brought on by breathing these particles, as among adults
following other occupations. Proper working conditions and
a due amount of precaution on the part of the workman,
however, render a comparatively good protection against
these dangers.

In the rag-dusting, sorting, and cutting rooms of some
paper mills, objectionable amounts of dust are often present.
Workmen exposed to dusty atmospheres are especially sus-
ceptible to diseases of the lungs, such as tuberculosis, because
of the constant irritation of the respiratory tract. Constant
coughing causes the mucous membrane of the throat to
become inflamed and this condition allows germs to thrive.
In a healthy individual the normal mucous membrane would
not allow the germs to penetrate the membrane.

404. Cause of Tuberculosis. — It is a well-known fact that
a large percentage of deaths among factory operatives is due
to consumption. While perhaps some of this may be traced
to the environment of the home, many cases are contracted
in the factory from people who are in the early stages of the
disease. The reason lies in the fact that in every act of
spitting, coughing, sneezing, and speaking, minute droplets
of saliva, which may contain tuberculosis germs (specific
bacilli), are sent forth into the air, in which they remain sus-
pended for some time. The spitting consumptive is usually a

358 APPLIED SCIENCE

victim of the disease long before it is known. Sputum cast
about upon the floor and elsewhere becomes dried on ex-
posure to the air and then ground to powder, the bacilli
spreading in all directions.

Enough has been said to show the need of a systematic
method of removing the waste gases, dust, etc., from rooms
and buildings. Natural agencies, like the air, that pass
through the cracks of floors, doors, and windows may be
sufficient to remove some of the carbon dioxide of a dwelling
house by replacing it with new air, but in a factory where
hundreds of people are employed in the same rooms this
method is ineffective.

Questions

1. What is ventilation?

2. Why is ventilation necessary?

3. What are the different methods of ventilation?

4. Describe each method of ventilation.

5. What are the waste products of industrial processes?

6. Describe the changes that take place in the human body and
some of the waste products.

7. Name some noxious gases and the evil effects produced by
them.

8. Name some of the forms of dust found in industries.

9. What are some of the causes of tuberculosis?

CHAPTER XXIX
GAS ENGINES

405. Principles on Which Based. — The gas engine (Fig.
176), which is coming gradually into use, requires but a small
amount of fuel. In a steam boiler, the energy is transmitted
to water inside the vessel. In the gas engine, the gas or oil is
brought in contact, mixed with the air, and exploded. Gas
engines are constructed in somewhat the same way as an
ordinary high-pressure steam engine, and are built both as
single and coupled engines. The cylinder is specially con-
structed and is surrounded by a water jacket provided with
an ample supply of water to keep it cool (Fig. 177). The
piston and rod, guards, connecting rod, crank, and fly-wheel
are the same as those of a steam engine. The propulsive
force of the gas engine is furnished by an explosion produced
by igniting within the cylinder a mixture of air with coal
gas, kerosene, gasoline, or alcohol vapor. To have complete
combustion, it is necessary to have sufficient air, as the oxy-
gen must combine with the hydrogen and carbon of the fuel.
The gas is admitted at every other revolution, since the prod-
ucts of combustion must first be expelled by the piston on
its first return stroke. During the second stroke the mixed
gases are admitted through a valve, which closes like a pump
valve when the piston shoots back. When the piston is at the
end of its stroke and has compressed the gases, it closes an
electric circuit, which is broken when the piston shoots on its
second outward stroke. This produces a spark which ignites

359

360 APPLIED SCIENCE

the gases, and the operation ia then repeated. This method
of sparking ia classified as a make-and-break system, and
should be distinguished from the spark-plug system.

As the force is excited on but one side of the piston, and
only once in two revolutions, the gas engine is less steady
than the steam
engine, which
has two impulses
for each revolu-
tion. This fault
is overcome to
some extent,
however, by the
use of heavy fly-

406. Types
of Gas Engines.

— Most gas en-
gines are of the
four-cycle type
used in many
motor car en-
gines. It differs
Fia. 176. — Gas Engine with an Air Compressing from the tWO-
Outfit. Used for compressing air inagarage. The • ,

two large tanks or receivers in the rear are for "y 016 type, in
storing the compressed air. A gauge ia on top that the explo-
of the tank to indicate the pressure in the tank.

sive mixture is
admitted and ignited after every other revolution of the en-
gine, instead of after every revolution as in the two-cycle
type (Fig. 178). To get a more constant turning effect,
certain machines, like motor cars, have engines composed of

GAS ENGINES 361

two, three, four, six, and sometimes eight cylinders. The six-
cylinder engines are the most popular for touring cars.

407. Operation of Engine.— The operation of a four-cycle
machine may be understood by studying the four different
steps in the working of the engine.
There are two openings or valves in the
cylinder — an inlet valve for the mixture
to enter, and an exhaust valve for the
disposal of the gases. When the piston
is at its highest position, the valves are
closed. As soon as the engine is run-
ning, the motion of the fly-wheel carries
the piston down, and the partial vacuum
created behind causes the inlet valve to

open because the outside atmospheric Fig. 177. — TheCylin-
pressure is greater than the inside pres- j^ket^^fn section)
eure. Many up-to-date engines have a ofaGasEngine. De-
mechanical inlet, and do not depend premature ignition
upon atmospheric pressure to open the ? f th ^ mixture and
_,i_ i ■ • to assist in lubncat-

inlet valve. The explosive mixture of ingthepiston. The

air and gas enters and fills the cylinder. ^he cylindeHu'the
The momentum of the fly-wheel is suffi- *^. tion „ """ted
dent to keep the piston moving. The
greatest power is derived from an engine when the gas
explodes just before the piston reaches the highest point,
because the speed of the piston makes it necessary to
ignite the gas at the top of the stroke in order to have
complete combustion. The spark-plug, screwed into the
opening, gives off a spark which explodes the mixture.. As
the piston rises again, the exhaust valve opens mechani-
cally and the burnt gases, still very hot, escape through the

362 APPLIED SCIENCE

exhaust pipe. The piston passes through the cylinder four
times, twice in each direction. The first mixture of air

and gas is drawn
in during one
stroke; then the
mixture is ex-
ploded; the force
of the explosion

starts the next

Fig. 178. — The Action of a Two-Cycle Engine. gfa»oke and on
The explosive mixture is taken into the crank '

case through a non-return valve at a on the up the return the

t stroke of the piston. It is compressed on the i , « QO rva Q «^

', downstroke and allowed to flow into the cylin- Dmm £ ases are

der when the piston passes over and uncovers driven out.
the port b. The charge is compressed on the ,

upstroke of the engine, is fired and expanded I he heat gen-

on the downstroke, and exhausted when the era ted bv the
piston passes over and uncovers the part c. # ^

D is a deflecting plate to deflect the explosive burning of the

mixture toward the top and preventing it from ., . ,

going out ate. oil is so great

that the walls of
the cylinders would become red hot if water were not cir-
culated over them by a pump. The cranks of the engine
revolve in an oil-tight case and are dipped in oil so that it
will splash up into the cylinder and in this way keep the
piston well lubricated.

408. Principal Parts of a Motor Car. — To show the
"works" of an automobile it is necessary to remove the
body or top of the car. What remains is called the chassis
(Fig. 182).

Starting in front of the seat we see the handle, which is a
level for setting the engine in motion. Underneath the hood
is the engine. The lever connects to the engine. Front of
the engine is a heavy fly-wheel, The shaft of the engine is

GAS ENGINES 363

continued to the gear-box which contains the gears for alter-
ing the speed of the driving wheels to that of the engine. In
the rear of the gear-box
is the propelling shaft,
which connects by
means of bevel gears, a
special device of gears
called a differential, to
the axle of the driving
wheel to which the power
of the engine is trans-
mitted. The engines,
gear-box, etc., are all
mounted on the frame of

the car. Between the Fiu. 179. —Valves and Valve Cages.
frame and axle are the Showing how they may be removA
springs which absorb the shocks caused by humping over
rough roads.

Sometimes the power is transmitted from gear-box to axle
by means of chains. In this case there is a sprocket wheel on
a shaft behind the gear-box, and a larger sprocket wheel
attached to the hubs of the driving wheels. The axles of the
driving wheels are fixed to the springs and wheels revolve
around them.

409. Other Parts of Motor Car.— The other parts of an
automobile which need a brief description are the starting
handle, the carbureter, silencer, governor, magneto, and
gears.

Starting Handle. — In front of the car there is a handle
attached to a tube which terminates in a clutch. A powerful
spring keeps this clutch from a second one that is keyed to the

364 APPLIED SCIENCE

engine shaft. When one desires to start the engine he p
the handle towards the right, so as to bring the clutches to-
gether and turns the handle in the direction of the hands of a
clock. When the engine begins to fire the clutches slip over
one another.

Carbureter. — The carbureter (Fig. 183) reduces the liquid
fuel to a fine spray and mixes it with sufficient quantity of air

Pia. 180. — Ignition Apparatus for a Gas Engine. The illustration to the left
shows the interior with four dry cells and a spark-coil. The illustration to
the right shows the waterproof case, switch, and necessary wiring.

so that it will burn. It consists of two parts — a device for
regulating the supply of fuel called the float chamber, and a
device for controlling the amount of air to be mixed with the
liquid spray.

Silencer. — As the products of combustion are given off at
high pressure they expand violently and cause a vacuum in
the exhaust pipe. The air rushes back with terrific force
(15 lbs. per square inch) causing a loud noise. To overcome
this noise, a device called a silencer is fitted to the machine
which allows the gas to escape gradually, or reduces it to
atmospheric pressure so that the noise becomes a gentle hiss.

GAS ENGINES 365

Brakes. — There are usually two brakes on each car — a
side hand-lever that acts on the axle of the driving wheel
and another, operated by the
foot, that acta on the trans-
mission gear.

Governor. — The speed of
the engine may be regulated
in three ways by a centri-
fugal ball governor. When
the speed exceeds a certain
limit it either raises the ex-
haust valve so that no fresh
charges are drawn in, pre-
vents the opening of the inlet
valve, or throttles the gas
supply. The last arrange-
ment is the one most com-
monly employed. Fla - 181.— Electrical Gaa Engine.
Notice the two fly-wheels and

Gear-Box. — The gear-box the pulley attached on the left.

^a «a*a. ~«. i*. ,.„».. ;™ Power is transmitted from. the
a motor car is very 1m- puMey by means of belting

portant. An explosion en-
gine must be run at a high speed to develop its full power.
There are times when a machine must do heavier work
than usual, as for example, when it passes from a level
road to a steep hill. It accomplishes this task by alter-
ing the speed ratio of the engine to the driving wheel.
This change in the speed ratio is made possible by the
mechanism of the gear-box.

Spark-Plug. — An accumulator and induction coil is an
arrangement for producing a spark. It consists of a disk of
insulating material mounted on a cam or half-speed shaft
with a piece of brass, called a contact piece, attached. A

g s 83 6 si a

■3 .J i
s .1*8-1

III

GAS ENGINES 367

movable plate rotates and presses against the disk. When
this contact takes place a cur-
rent flows from the accumulator
through the different parts, in-
cluding the induction coil, and
back to the accumulator. In
this circuit is a spark plug so
arranged that there is a small gap
through which the current passes
and produces a spark.

Questions

L How does a gas engine work?

2. What is the combustible or inflammable material used?

3. What is the supporter of combustion?
i. What are the gases exploded?

6. How is gasoline made into a gas?

6. What is the source of energy of the gas engine?

7. What are the two types of gas engines commonly used?

8. Explain the operation of each type.

9. How does the two-cycle engine differ from the four-cycle
engine?

10. What is the object of compressing the charge in a gas engine?

11. Does the nitrogen of the air take part in the explosion?

12. What are the products of combustion in the explosion if we
assume the gas is composed of hydrocarbons?

13. At what point should ignition take place to get best results?

14. Upon what does a successful and reliable ignition depend?
16. How is ignition accomplished in a gas engine?

16. Name two systems of ignition.

17. Give advantages and disadvantages of each system.

18. What is the great source of loss of power in a gas engine?

Problems

1. The horse-power of a four-cycle engine is estimated approxi-
mately by multiplying the area of the piston by the length of stroke,

368 APPLIED SCIENCE

and this product by the number of revolutions per minute and
dividing the final product by 15,000. What is the horse-power of a
four-cycle gas engine with a 5 in. bore, 6 in. stroke, and 400 R. P. M.?

2. The proportion of gas and air in an explosive mixture is or-
dinarily a mixture of one volume of gas to seven to ten of air. How
much air should be mixed with 6 cu. in. of gas?

3. The maximum pressure in a gas-engine cylinder may be cal-
culated approximately by multiplying the gauge pressure of com-
pressure by four. What is the maximum pressure in a gas-engine
cylinder if the gauge pressure is 70 lbs.?

CHAPTER XX^

PAINTS AND VARNISHES

410. Objects and Operations of Painting. — Paints and
varnishes are used to preserve and ornament surfaces. A
paint is opaque and therefore completely covers the under-
lying material, while a varnish is transparent or translucent
and protects the surface without hiding it.

Painting includes a variety of operations, such as: (1) the
preparation of wood, plaster, and metal surfaces to receive
the coats of paints; (2) the removal of old finishes; (3) the
preparation and mixing of spirit or oil vehicles (carriers) and
lead, zinc, or other color substances called pigments; (4) the
rubbing down of coats; (5) the graining, laying on of gold-
leaf gilding, lettering, free-hand drawing, stenciling; (6)
the rigging of scaffolds; and (7) the setting of glass with
putty or molding in windows, doors, and skylights, con-
structed of wood, metal, or stone. These processes are per-
formed under a variety of conditions — in the paintshop, in
manufacturing plants of many kinds, or on the outside or
inside of dwellings or other buildings.

411. Preparation for Painting. — The first step in all types
of painting is the preparation of the surface which is to be
covered with paint. In new work, this consists in cleaning
and smoothing the surface with sandpaper and a dusting brush.
In refinishing surfaces which have once been painted the first
step is the removal of old finishing coats of paint or varnish.

24 369

370 APPLIED SCIENCE

This is commonly done by burning the old coat with a Bunsen
burner. The heat causes the paint to soften and to "peel"
or blister. It is then easily scraped off. In other cases paint
or varnish solvents are applied before scraping. Surfaces
from which old finishes have been removed must be sand-
papered until perfectly smooth. When the wood has been
laid bare, smoothed, and cleaned, it is ready for one or more
coats of new paint. The color selected for the first coat is
chosen with regard to the color of the coats that are to follow.
This first coat is known as the priming coat.

The priming coat is worked well into cracks and nail holes
to protect such broken surfaces and is then allowed to dry.
After this the cracks and holes are filled with putty, to which
the paint adheres well. Two or more coats of the required
color are then applied, the number and composition of the
final coats depending upon the class of work.

412. Composition of Paint. — A paint consists principally
of two elements: (1) a body of opaque coloring matter which
covers the surface and which is not dissolved by water,
and (2) a vehicle with which the coloring matter is mixed so
as to be easily applied. The vehicle evaporates and leaves
the coloring matter deposited on the surface. In addition,
other substances are added to paint, such as solvents, to
make the paint more liquid and therefore more easily applied,
and driers, to hasten the hardening of the paint.

413. Linseed Oil. — The principal vehicle for most paints
is linseed oil, as it is the best drying oil; that is, on exposure
to air it absorbs oxygen and is converted into a transparent
resin-like mass. Sometimes other oils are used, but they are
all inferior in drying power to linseed oil. Raw linseed oil

PAINTS AND VARNISHES 371

has a greenish yellow color. It is obtained by pressure from
flax seeds and after filtration is sent to the market as cold-
pressed oil. If the seed is pressed at a temperature near the
boiling point of water, more oil is obtained, but the quality
of the hot-pressed oil is inferior to that of the cold-pressed
oil.

Linseed oil is sold on the market in two grades — raw and
boiled. The method by which the raw oil is obtained has
already been explained. Boiled oil is ordinary raw oil which
has been heated so as to remove some of the "light" (volatile)
constituents. This operation produces a thicker and darker
oil resulting in a more resistant film. The oil is often bleached
to remove its color. This is done by the action of sulphuric
acid and steam. The traces of acid are removed by shaking
the oil with water.

414. Driers. — The necessity of increasing the rate of
drying has led to the addition of metallic salts or oxides,
called "driers," to hasten the oxidation of the paint. These
driers are added to the oil before the paint is mixed and act
as carriers of oxygen from air to oil. If a paint is dried too
quickly, the film produced by oxidation will not acquire
the toughness and elasticity which are essential for efficient
wear.

415. Thinners. — It is necessary at times to decrease
the thickness (viscosity) of paint so as to make it more
workable under the brush. It is to the interest of both the
workman and his employer to do this as reducing the paint
to as liquid a condition as possible, lessens the labor of apply-
ing and spreading it, and enables a given amount to cover
the greatest possible surface. A limited amount of' "thin-

372 APPLIED SCIENCE

ners" is legitimate and necessary. The thinning agent most
used in the paint trade is turpentine.

416. Turpentine. — The liquid known in the trade as
turpentine, or "turps," is obtained by the distillation of the
fluid exuded and collected from growing pines. It has a
strong smell, a bitter, disagreeable taste, and is a mixture of
hydrocarbons. Pine trees about forty years old, which have
been much exposed to the sun's rays, yield the most turpen-
tine. The bark of the tree is cut (wounded) in March, when
the sap begins to rise. The sap drips into a barrel placed
at the foot of the tree and is afterward purified by being al-
lowed to "settle " in the heat of the sun. The fluid filters into
the bottom of the barrel through a perforated false bottom.

There are several kinds of turpentine, the best of which
comes from the south of France. Canada balsam is a vari-
ety obtained from a tree growing in the cold countries of
North America. China or Cyprus turpentine is brought
from the north of Africa, the south of Europe, and from islands
of the Mediterranean. All these turpentines on being dis-
tilled yield an essential oil which is commonly called spirit
of turpentine because it is the product of distillation. After
the oil of turpentine has been obtained, a hard, brown, brit-
tle residuum is left, which is known to commerce as rosin.
Rosin is highly inflammable, easily melted, insoluble in water,
and readily unites with oils. Cheaper liquids than tur-
pentine that will easily mix with oils, such as rosin, spirit,
shale-naphtha, benzine, and petroleum oils, are often used as
substitutes.

417. Nature of Resins. — Resins are gluelike bodies which
are found in plants or are produced by the oxidation of tur-

PAINTS AND VARNISHES 373

pentine exudations. They are hydrocarbons and in composi-
tion closely related to turpentine. The varieties of resins
are amber, copals, lac, rosin, and asphaltum. Amber is the
best resin, but is too costly for ordinary purposes, so that
copals are generally used in its place. Rosin is hard, but
too brittle to be desirable. Lac is soluble in water and is thus
readily distinguished from the other resins. It is formed by
the action of insects upon the sap of certain Indian trees.
The commonest form of lac is known as shellac, and is dis-
solved in wood alcohol or benzine to increase its rate of
drying. Asphaltum is a mineral product and is used as the
solid ingredient of japan.

418. Composition of Varnishes. — Varnishes are solutions
of natural resins in oils and spirits. They are applied as a
final coating to painted or stained work and are oftentimes
mixed with paints before application. This is done in the
case of enamels. A good varnish depends upon both the
solvent and the resin, and it is necessary to use a solvent that
will oxidize and bind the film of resin. Spirit varnishes,
made wholly of volatile solvents, will not dissolve the harder
resin, but are desirable because they evaporate quickly. The
best varnishes are those consisting of a resin dissolved in lin-
seed oil. The surface to which a varnish is to be applied should
be free from dust and non-absorbent. A gelatin size will
produce this effect. Varnish should be put on in thin layers.

The qualities looked for in an ordinary varnish are tough-
ness, hardness, transparency, body, and freedom from color.
A good varnish should be dry and hard enough to touch
in ten hours. It should resist a moderate blow without
cracking, and the finger should leave no mark when rubbed
over its surface.

374

APPLIED SCIENCE

•

Fig. 184.— A Buckle.

419. White Lead Bases of Paint— The bodies in a paint
that are responsible for covering the material painted are

called "bases." The "bases" form

the mass of the solids contained in

paints. The substances added to

give colors are known as pigments.

Sometimes the bases play the part of

a pigment, as in the case of white lead,

zinc white, iron oxide, and red lead.

The principal base is usually white lead, a basic carbonate of

lead, which is produced, by the so-called Dutch process, as

a white amorphous powder. It is dense and has a good body.

A number of distinct operations go to make up the Dutch

process. (See Figs. 184-187.)

(a) The lead which has been extracted from the ore and refined,
comes to the white lead factory in the form of pigs. There it is
immediately melted and recast into perforated metal disks, called
"buckles." These buckles are about 5 in. in diameter and 34 in.
thick.

(b) The buckles are placed in earthenware corroding pots, which
somewhat resemble flower-pots as to shape.

These pots are so constructed, however, as to
permit the disks to rest upon a ledge some two
inches from the bottom. Into this space acetic
acid is poured before the buckles are inserted.

(c) The pots, containing the acetic acid sur-
mounted by the disks, are then piled in a stack-
house. The stacks consist of alternate layers of
20 in. thick tan-bark and corroding pots. Each
stack is about 22 ft. long, 20 ft. wide, and 30
ft. high.

(d) The tan-bark slowly decomposes, ferments, and creates a
heat strong enough to warm the acetic acid until vapor is given off.

(e) The acetic acid vapor steams up through the perforations in

Setting

Fig. 185.

PAINTS AND VARNISHES 375

the buckles, which gradually become coated with the lead acetate
and turn white. The fermenting tan-bark is, meanwhile, generating
carbonic acid gas. As the acetic acid fumes turn the metal lead
to acetate, the carbonic gas turns the lead acetate to basic lead
carbonate. This step completes the process of corrosion, which
takes altogether from 90 to 130 days.

(/) The stacks are then torn down ("drawn" or "stripped").
The acetic acid having evaporated, the disks are found to have

Fig. 186.

become so brittle that they may be crumbled with the fingers and
to have changed from a bluish gray to a white color.

(p) Next the corroded disks are subjected to several grinding, sift-
ing, and refining processes, the object being to separate and remove
the metal lead, so that only the pulverized white lead will remain.

(A) When the last step in refining has been finished, the purified
white lead is thoroughly mixed with linseed oil. The mixture is
then given a final grinding, from which it emerges in the doughlike
chunks which form the white lead of commerce.

376 APPLIED SCIENCE

Since white lead is expensive to prepare, various substi-
tutes, such as lead sulphate and chalk, have been used. In
addition, numerous more or less successful attempts have
been made to devise a method for making white lead quickly.
One method is to pass carbon dioxide through a ground
mass of litharge and salt in water; another is to pass a cur-
rent of electricity through a solution of sodium nitrate
(NaN0 3 ) in water in which a lead bar is suspended; and
a third is the wet process. The wet process is carried out in
the following manner. Metallic lead is melted and poured

Pig. 187.

from a height of 15 ft. into water, the result being that granu-
lated lead is produced. This is placed in cylinders and
treated with acetic acid, which is kept in motion by constant
pumping. The final product is filtered out, washed with
water, and ground in oil. It is not, however, so effective in
covering power as the Dutch white lead.

420. Pigments and Colors of Paints. — The color of a
paint is due to the pigment it contains, usually a metallic
salt. Sometimes aniline dyes (organic coloring substances

PAINTS AND VARNISHES 377

obtained from coal tar products) are used. Such colors,
however, fade as a rule within a short time after being ex-
posed to light. Some of the metallic pigments are changed
"by the action of light, air, and sulphur fumes. Lead, for
instance, is turned black by the fumes of burning coal.

When paints are mixed, the color of the mixture is deter-
mined, not by the mean average of the individual colors, but
by the nature of colors which are reflected, i.e., not absorbed,
by both pigments. If all colors are absorbed then the
body is black, while if no colors are absorbed the body is
white.

A great many artificial lights, such as yellow gas light,
are lacking in certain colors. Consequently the reflected
light from them will differ from the reflected sunlight, and
the color will be correspondingly different.

421. Chrome Yellow. — Chrome yellow (PbCr0 4 ) is a
solution or a powder of dichromate. Zinc sulphate added
to the yellow lightens the color. The basis of all yellow pig-
ments is chrome yellow, which is formed by precipitating a
chromate of lead, zinc, or barium. The shades may be modi-
fied by the addition of lead, barium, or calcium sulphate in
a grinding mill. Lead chromate has a great covering power,
but is blackened by sewer gas (hydrogen sulphide). It
should not be mixed with any substance that contains
sulphur.

422. Red Lead. — For protecting surfaces of metals, etc.,
a red paint, called red lead (Pb 3 4 ) is used. It is made
by heating lead in air to a molten state tb convert it into
litharge (PbO) and by then slowly heating the litharge until
it acquires the desired color.

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APPLIED SCIENCE

423. Zinc Bases. — Zinc compounds are often used as a
basis instead of lead, when the paint is to be exposed to
fumes of sulphur compounds. Zinc does not mix as readily
nor does it have the same body as lead.

424. Ocher . — Ocher, made with iron oxide as a base, is usu-
ally used to cover iron. The color varies from a brown to a red.

425. Staining, Filling, and Varnishing. — Dyes dissolved
in water, oil, or spirits are applied to the bare wood to give
color and to bring out the grain. This process is called stain-
ing. Another method of staining is to expose the surface to
ammonia fumes in a closed receptacle. The fumes by chemi-
cal action will in this case turn the wood nut brown.

The pores of the natural or stained wood are filled with
liquid or paste filler, liquid fillers being used on close-grained
woods, such as pine, and on large surfaces, and paste fillers
on coarse-grained woods, such as oak or chestnut. The
coat of filler is applied evenly, allowed to stand 24 hrs., and
then sandpapered lightly. In fine cabinet work on close-
grained wood, white shellac is often used as a filler, since
shellac makes a good foundation and does not darken the
wood as does varnish.

The best paste fillers are made of ground rock-crystal
mixed with raw linseed oil, japan, turpentine, and some
color suitable for the wood. They are applied to the surface,
worked into the pores, and left on the wood in a thin layer.
When the filler has become dull and chalkish, it is rubbed off.
The rubbing is done first across the grain to fill the pores
thoroughly, and then with the grain to bring out the high
lights. Twenty-four hours are allowed for the filler to hard-
en. One application is usually sufficient.

PAINTS AND VARNISHES 379

Copal or oil varnish is usually "flowed" on, the brush
being dipped deeply and varnish spread in a heavy coat.
The surface is then gone over lightly with the brush as free
from varnish as possible until the work is left with only a
thin coating. Three or four coats are generally applied, time
being allowed for each coat to dry before the next one is put
on. The first coats are rubbed with haircloth or curled
hair. For a dull finish, the last coat is rubbed smooth with
powdered pumice-stone and water, and the pumice removed
with a damp sponge and chamois skin. When a gloss finish
is desired, the last coat is not rubbed. For a polished finish
the last coat is rubbed with pumice-stone and water, then
with water and rottenstone; if a very fine surface is desired,
it is finished with oil and a little rottenstone and rubbed with
a soft flannel or with the bare hand.

Shellac or spirit varnish, made by dissolving shellac in
alcohol, does not flow freely. It must be applied thinly with
long, even strokes of the brush. A surface finished with
shellac varnish is given five or six coats, each coat being
rubbed down with fine steel wool, curled hair, or oiled sand-
paper.

These processes are performed in the order in which they
have been described. The stain is applied first, then the
pores of the wood are closed with a filler, and finally the
varnish coats are put on according to the finish desired.

426. Graining. — In imitating the grain of various woods,
the surface is first given at least two coats of paint tinted
according to the kind of wood to be imitated. The second
coat of ground-color is made to dry with a gloss, so that the
graining mixture will not, by being absorbed, make the grain
appear dingy. After the ground-color is thoroughly dry the

380

APPLIED SCIENCE

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graining mixture, of a color to suit the kind of wood to be
imitated, is applied, and before drying, the coarse grain is
made by drawing a graining comb of leather or gutta-percha
over the surface. The surface is then worked over with a
fine steel graining comb in the same direction. The heavier
figures of the grain are made by wiping out the graining
mixture with the thumb covered by a piece of cloth. A fine
bristle brush is finally passed lightly over the surface to blend
or soften the heavy lines, imitating as nearly as possible the
grain of the natural wood.

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427. Kalsomining. — In kalsomining the first process is
that of cleaning and preparing the walls. All grease or lime
spots are scraped and smoothed, and all nail holes and cracks
filled with putty, whiting, or plaster of Paris. The walls
are then given a sizing of thin glue, which causes the kalso-
mine to hold well to the wall, and at the same time prevents
it from striking in. Sometimes a coat of oil paint or hard oil
is used for this purpose, and also to prevent dampness from
striking through the walls and discoloring the kalsomine.

Kalsomining mixture consists of dissolved glue, whiting
to give body, and some coloring material, such as is used in
oil painting, to give the desired color. It must be prepared
with reference to the work to be done, more glue being re-
quired, for example, on side-walls to prevent rubbing, than
is required on ceilings.

In fresco painting, the kalsomine is applied while the wall
is still damp, making the color a part of the fresco work;
but in cases where the walls are not decorated, they are
allowed to become thoroughly dry before the kalsomine is
applied.

Any desired color may be obtained by mixing the primary

PAINTS AND VARNISHES 381

colors — red, yellow, and blue — lampblack being added in
some cases. Kalsomine is applied with a large brush; the
ceiling is worked first and later the side-walls.

428. Sign Painting. — Sign painting, which includes all
kinds of advertising painting, from small lettered signs on
cardboard or wood to large pictorial work on walls and
large signboards, requires on the part of the painter a special
aptitude for fine color-work, designing, free-hand drawing,
and lettering. Some classes of work are done in the shop,
but much of the work must be done outside.

In small lettered signs, the ground is prepared by laying
on several coats of white paint. When these coats have
dried thoroughly the letters are sketched off with white
chalk and then carefully traced with charcoal. After this
operation the surface is brushed over, leaving only a dim
layout, and the letters are cut in by outlining them with
lampblack mixed with linseed oil. The letters are filled
with paint, black paint being most commonly used on a
white background. For fine work, a small red sable pencil-
brush is used, and for large work a small bristle brush. When
the surface to be lettered is of metal, it is first pickled with
vinegar to make the paint hold well, the other processes being
the same as in the case of wooden surfaces.

When several signs of the same kind are to be made,
stencils are used. To make a stencil the letters or designs
are first drawn on a sheet of stiff, heavy paper and are then
carefully cut out. The sheet of paper is tacked to a light
wooden frame and well coated with shellac. When the
sign is to be made in two or more colors several stencils are
made, one for each color. After the sign has had two coats
of ground-color and has thoroughly dried the stencil is laid

382 APPLIED SCIENCE

upon the sign and the paint applied through the opening
cut in the stencil. The paint used is mixed with benzine
and is applied with a stiff bristle brush. After the letters
are dry they are second-coated.

429. Gold-Leaf Work. — In gold-leaf work the letters are coated
over with a good oil gold-size which is allowed to stand usually about
twenty-four hours until it has reached the degree of dryness called
"tacky." In this state the leaf will adhere to it strongly. The
gold-leaf whiph comes in booklet form, is then applied on a certain
part of the letter, and cut by running the finger nail across it. Then,
;| without removing the leaf from the book and keeping the rest of

the leaf covered, the portion cut is pressed firmly against the part
of the letter to be covered. The gold-leaf adheres to the size when
the book is withdrawn. When all of the letters have been covered
in this manner they are cut in with a size made of animal fat oil,
lampblack, and a little white lead. Generally, to complete the
work, the sign is laid in a horizontal position and smalt or ground
black glass is sifted on. When the size has dried enough to retain
the smalt, the sign is raised to a vertical position and the superfluous
smalt is brushed off with a soft brush.

In gold lettering on glass the letters are first outlined with chalk
on the outside of the glass. They are then covered on the inside
with a size made by placing in cold water Russian gelatin, sometimes
called Russian isinglass, and boiling it for about three minutes. The
size becomes "tacky" in from fifteen minutes to three hours. The
gold-leaf is put on by handling it with what is called a tip. A tip
is a brush consisting of a thin layer of camePs hair glued between two
pieces of cardboard. The hair of the tip is slightly oiled, so that
the leaf will adhere to it until placed against the size on the letters.
After the leaf is placed on the letters, the chalk lines which show
through the gold are carefully outlined on the inside with black
paint. When this paint is dry, the gold-leaf which projects beyond
the lines is removed with a piece of cotton and water. The letters
are usually outlined with paint in such a manner as to give them the
appearance of thickness. After this work is dry, the whole surface
is given a coat of varnish.

PAINTS AND VARNISHES 383

430. The Hygiene of the Painting Trade. — A thorough
knowledge of the dangers attached to handling and working
paints is absolutely essential as a safeguard against poisoning.
It has been scientifically demonstrated that many of the
materials with which the painter works are poisonous, and
many of the processes are such that it is difficult, especially
under certain conditions, to avoid contact with these poisons.
There are, however, certain simple precautions by which
the danger can be avoided.

Either or both the pigment and the vehicle of paint may
be poisonous and either or both may be perfectly harmless.
The higher priced paint usually contains white lead,
linseed oil, and turpentine. Both the white lead and the
turpentine are poisonous. The pigment in cheap paint
may be something perfectly harmless, as chalk or barium
sulphate, while the vehicle may contain so great a per-
centage of petroleum compounds that it is extremely poison-
ous, especially when used on inside work in poorly ventilated
enclosures.

431. Dangerous Pigments.— The pigments which cause
poisoning are the lead salts — white lead, sublimed white lead,
chrome yellow, chrome green (a mixture of chrome yellow
with Prussian blue), red lead, and orange mineral. Lead
carbonate and lead sulphate are used in the higher priced
paints, usually separately, but sometimes together, and the
carbonate more commonly than the sulphate. Chrome
yellow is used for tinting in house painting and in coach
painting; chrome green for painting window shutters; red
lead in painting structural iron- work; and orange mineral
for painting wagons. Of these constituents, lead carbonate
is considered the most poisonous; but when sandpapering,

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384 APPLIED SCIENCE

mixing, or chipping off old paint, the red lead is the most
dangerous because it is lighter and floats in the air more
easily. Chrome yellow is considered to be almost as harmful
as the red lead. Lead sulphate is not so dangerous as the
lead carbonate, red lead, or the chrome yellow. Both lead
carbonate and lead sulphate, however, produce acute lead
poisoning.

432. Safeguards Against Poisoning. — Experiments con-
ducted to determine the effect which milk, when combined
with the gastric juice (a fluid secreted in the stomach), has
upon the amount of lead dissolved, brought the conclusion
that when the milk and gastric juice are in equal proportion
the hydrochloric acid of the gastric juice is so completely
fixed by the milk proteins, or neutralized by the carbonates
in the milk, that the mixture has virtually no solvent action
on the lead salts; that is, it will not dissolve the lead. Con-
sequently, milk drinking will have a beneficial effect on the
worker exposed to lead poisons.

Three practical suggestions have been made for safe-
guarding painters against poisoning:

(a) Since lead carbonate is so much more toxic than the
lead sulphate, individual lead-workers, as well as industry
in general, should aim at the elimination of the use of the
carbonate wherever possible.

(6) Since basic lead sulphate, or sublimed lead, is poison-
ous, none of the precautions usually advocated for the pro-
tection of workers in lead should be neglected by those
handling lead sulphate.

(c) In addition to taking other important prophylactic
(preventive) measures, workers in lead salts should drink
a glass of milk between m3als — say at 10 a.m. and 4 p.m. —

PAINTS AND VARNISHES 385

in order to diminish the chances that the lead they may have
swallowed be dissolved by the free hydrochloric acid of the
gastric juice, as in some persons there is considerable secretion
of gastric juice in the empty stomach.

Dust from the sandpapering of lead-painted surfaces is
one of the most important causes of lead poisoning. The
dust thus raised is inhaled and lodges on the mucous mem-
brane of the throat and nose and is then swallowed. In this
way the great bulk of such dust finds its way into the stom-
ach and not into the lungs. The workman is thus poisoned,
as the lead in the dust is dissolved by the free hydrochloric
acid in the gastric juice and is easily absorbed. This dust
- is dangerous not only to the men doing the sandpapering,
but also to the others working nearby. The danger can
be entirely eliminated by the use of pumice-stone and water
in rubbing down coats. On a first coat, this process is apt
to raise the grain, and if the coat is on metal, it may cause
rust. In these cases the danger of poisoning can be elim-
inated by moistening the sandpaper with some cheap mineral
oil. Sandpaper so oiled lasts as well as when used dry, and
the results so far as tfye work is concerned are equally good.

When metal surfaces are to be repainted they are usually
chipped and cleaned, the work often being done by a com-
pressed air machine. This method is very dangerous, and
a much better way, whether on wood or metal, is the burning
process already described. Though some authorities speak of
contracting lead poisoning by the use of the burning method,
their fears are not likely to be realized unless the painter
should hold the flame long in one place and thus cause con-
siderable smoke which might mechanically carry small
particles of lead. The boiling point of lead is so high that
the danger of evaporation is very slight, as comparatively

386 APPLIED SCIENCE

little heat is required to shrivel the paint. Danger of poison-
ing from this method may arise, however, when the burned
paint is allowed to lie upon the floor of the shop until ground
to dust. This dust is stirred up by the feet of the workmen
or by moving materials, and is constantly inhaled and swal-
lowed. The scraps of paint should, in every instance, be
cleaned up before they become dry. The painter should
moreover be extremely careful in handling his food and to-
bacco, and should avoid wearing dusty and paint-soaked
clothing.

433. Poisonous Vehicles. — The dangerous vehicles of
paints are turpentine, benzine, naphtha, benzol, wood alco-
hol, and amyl acetate. Turpentine, used as a dryer and
for thinning, is a constituent of many paints and varnishes
and often makes up the entire vehicle. The inhaling of
much turpentine-laden air causes headache, dizziness, irrita-
tion of the throat, etc. These fumes also cause inflammation
of the skin and often affect the nervous system, as is evident
in the typical symptoms of staggering and, in extreme cases,
loss of consciousness.

Benzine and naphtha are used in hard oils as dryers, and
often constitute a large percentage of the vehicle in cheap,
quick-drying paints. Fumes from these liquids affect the
nervous system much as does alcohol, causing staggering,
defects of memory, and disturbance of sight and hearing.
Where the workman is long exposed to these fumes, chronic
poisoning takes place, causing skin diseases, weakness, ner-
vousness, and sometimes even impaired mentality.

Benzol is used in priming and as a paint- and varnish-
remover, because of its penetrating and solvent qualities.
Benzol fumes are very dangerous and may be fatal. They

PAINTS AND VARNISHES 387

cause changes in the blood, hemorrhages of the organs and
mucotfs membranes, and degeneration of the organs. The
symptoms of this poisoning are a flushed face, dizziness,
headache, followed by a blue appearance of the skin,
and nervous excitement or stupor, accompanied by nausea.
If the poisoning is chronic, ulcers appear on the gums
and lips.

Wood-alcohol poisoning comes chiefly from inhaling the
fumes while using varnish. Inhaling such fumes causes
headache, hoarseness, twitching of the muscles, weak hearing,
unconsciousness, and temporary or permanent impairment
of sight, even to the point of complete blindness.

Amyl acetate, derived from fusel-oil and acetic acid, is
used in varnishes, gilding fluids, and as a paint solvent.
Its fumes cause headache, uncertain movements, difficulty
in breathing, sleepiness, bad heart action, and poor digestion.

Poisoning from the various paint vehicles may be avoided
in most cases by insuring good ventilation, either natural
or artificial, of the shops or rooms where work is being done.
When this is not possible the men should be changed as
often as possible on work, so that no one of them will absorb
enough poison to render him permanent injury.

Although the vehicles in the various leadless paints
are usually much more poisonous than those used in lead
paint, the introduction of the leadless paints into the in-
dustry is a great help toward the betterment of hygienic
conditions in the trade, as it is much easier to avoid poison-
ing from the vehicle than from the various lead pigments
in the paint.

Aside from the dangers already noted, the only remain-
ing danger of accident is from imperfect construction of
scaffolds.

388

APPLIED SCIENCE

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Questions

1. What is an opaque body? A translucent body? A trans-
parent body?

2. Name the physical properties of a paint; of varnish.

3. What effect has heat on dry paint?

4. What is a solvent?

5. Does wood absorb paint? What property of matter has
wood that allows it to do this?

6. Putty adheres to paint. What property of matter has
putty that allows it to do this?

7. Name the physical properties of putty.

8. Is the body of paint soluble or insoluble in water? Explain.

9. Explain the chemical action of the absorption of oxygen by
linseed oil.

10. What is a drying oil?

11. Explain the manufacture of linseed oil.

12. On what principle of science is a volatile constituent sepa-
rated from linseed oil?

13. Does heat always have a tendency to thicken a liquid?
Explain.

14. Why is it necessary to remove all trace of sulphuric acid in
bleaching linseed oil? Would sulphuric acid affect metals and wood?

16. Explain the chemistry of the action of "driers."

16. What is the meaning of viscosity?

17. Explain the manufacture of turpentine.

18. Will turpentine burn? What are the products formed from
the complete burning of it?

19. What are resins? Name their physical properties.

20. Explain the meaning of the statement that white lead is a
basic carbonate of lead.

21. Explain the physical properties of white lead.

22. Why is heat necessary in making white lead?

23. Explain the disadvantages of such organic compounds as
aniline dyes or paints.

24. Lead sulphide is black. Explain why white lead and other
lead paints are not used indoors where they may be exposed to coal
fumes which contain sulphur.

25. Explain the theory of coloring as applied to mixed paints.

PAINTS AND VARNISHES 389

26. To what is black color due?

27. Why will a paint look differently by gas light and sunlight?

28. Explain the manufacture of chrome yellow.

29. What is the basis of yellow paints?

30. How are light shades produced in yellow paint?

31. What is red lead?

32. Why is zinc paint used indoors?

33. What is an ocher?

34. What is staining? How does it differ from painting?

35. What is a filler? Why is it used?

36. What is the object of graining? Explain how it is done.

37. What is kalsomining?

38. What property does "sizing" possess that holds kalsomine
to the wall?

39. Explain sign painting.

40. Explain gold-leaf lettering.

41. Explain some of the dangers of the painting trade. What
precautions should be used to avoid them?

CHAPTER XXXI
TREES

434. Industrial Advantages of Wood. — Wood is the most
important material used by carpenters, cabinetmakers,
shipwrights, and other wood-workers in carrying on their
respective trades. It possesses certain physical character-
istics that make it very valuable for industrial purposes —
it is easily worked with tools into desired shapes and sizes;
it is easily penetrated by fastening agents, such as nails and
screws; it is strong, light, and easy to handle; it is a non-
conductor of heat and electricity; and it can be protected
by paint from the effects of air and moisture.

435. Characteristics of Trees. — Wood is, of course, ob-
tained from trees of various kinds. Though each kind of
tree produces a distinct type of wood, all trees have cer-
tain characteristics in common. Trees consist of three
parts: (1) the roots, which extend into the ground to a length
of 30 to 40 ft., or still farther when the soil is not too hard and
they do not find moisture enough near the surface; (2) the
trunk or stem, which supports the crown and supplies it with
mineral food and water from the roots; (3) the crown, a
network of branches, buds, and leaves.

436. Sap-wood and Heart-wood. — A cross-section view
of a tree shows the bark on the outside, the heart-wood in
the center of the trunk, and the sap-wood between the two.

390

TREES 391

The sap-wood is still living and growing, whereas in the
heart-wood growth has ceased. Through the openings of
the cells becoming choked so that the sap can no longer flow
through them, the heart-wood is formed. It serves merely
as a framework to help support the tree. When the tree
is cut down, the sap-wood rots more quickly than the heart-
wood, because it takes up water more readily and because
it contains plant food which quickly decays. Some trees
have no heart-wood while in many others the difference in
color between the sap-wood and the heart-wood is very
slight.

437. Sap. — Sap is formed, mainly in the early spring,
from water rising from the roots through the sap-wood. In
the leaves this water is converted into true sap, which con-
tains sugar and soluble gums. The sap descends through the
bark and feeds the tissues in process of formation between
the bark and the sap-wood. The term "sap" sometimes is
used wrongly to mean the moisture in wood, and at other
times to mean the sap-wood itself.

438. Structure and Growth. — A tree grows from a seed
to a simple stem which puts forth branches and foliage. Its
food consists of carbon dioxide obtained from the air, water
and mineral matter from the ground. The leaves have
breathing passages through which they take in carbon di-
oxide which under the action of the sun and green coloring
matter (chlorophyl) breaks up into carbon and oxygen. The
carbon is retained and oxygen given off.

The wood of a tree is composed of innumerable cells or
tubes each of which is long and hollow. Every one of these
pells has some special function in the life of the tree. Some

392

APPLIED SCIENCE

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i I

conduct water from the roots to the crown, some store away
digested food, while others merely strengthen the structure
of the wood and hold it together.

Through these tubular cells, the light and heat of the sun
draw up water, which, when converted into sap, keeps the
tree alive and enables it to grow. The process by which
water is absorbed by a tree and carried to the ends of its
leaves is called osmosis — a complicated process by which
water and certain substances pass through the membranes
of the cells. The carbon from the carbon dioxide of the
air aids in the formation of new cells, and the water is given
off in the form of moisture. Medullary rays aid in carrying
the sap from the bark to the wood and vice versa. These
rays are narrow strips of cells, sometimes scarcely visible
to the naked eye, running from the center to the bark of
the tree.

The cells continuously divide themselves and it is by this
process, made possible by the means just described, that the
actual growth of a tree takes place.

439. Annual Rings. — The cells form and the tree grows
most rapidly in the springtimej^jfecause there is at that time,
an ample supply of water to meet the demands of the tree.
New cells form also during the summer, but as the supply
of water diminishes in hot weather, the cells formed at this
time are smaller and less numerous than those of the spring.
During the winter, growth practically ceases. Since a new
ring of cells forms every year and the spring cells are larger
than the summer cells, each set of cells appears in a cross-
section view as a distinct circle or ring. These circles are
known as annual rings and by counting them the age of the
tree may be ascertained.

TREES 393

440. Size of Trees. — The following is a very practical
way of classifying trees in general divisions according to
size: Young trees which have not yet reached a height of
3 ft. are seedlings. Trees from 3 to 10 ft. in height are small
saplings, and from 10 ft. in height until they reach a diameter
of 4 in., they are large saplings. Small poles are from 4 to
8 in., in diameter, and large poles from 8 to 12 in. in diameter.
Trees from 1 to 2 ft. through are standards, and, finally, all
trees over 2 ft. in diameter are veterans. It is important
to remember that all these diameters are measured at the
height of a man's chest — about 4 ft., 6 in. from the
ground.

441. Varieties of Wood. — Many kinds of wood are used
for commercial purposes. Each kind has certain character-
istics peculiar to itself. The following list includes the
names and chief characteristics of the woods most extensively
used by wood-workers in carrying on their trade.

Pine is of two varieties — white and yellow. When dried,
these woods are free from all tendency to warp or shrink
and the grain is handsome in appearance. Articles made
from half-seasoned pine wood tend to shrink and fall to
pieces.

Rosewood is hard and dark with a wavy grain. It is
reddish brown in color with darker zones or patches.

Walnut when well seasoned is tough and little inclined
to warp.

Maple is a light and very durable wood, a special variety
of which is called bird's-eye maple.

Oak requires a long time to season and is very unsatis-
factory if used green. It is very difficult to work but its
appearance improves with age. It has a tendency to warp

394 APPLIED SCIENCE

and to overcome this weakness it is usually paneled with
chestnut.

Pear wood is a light yellow wood with an even grain and
is, consequently, used for carving.

Chestnut is coarse-grained, strong, elastic, light, and
durable. In appearance it resembles oak and is used in the
manufacture of cheap grades of furniture.

Ebony is a heavy, hard, durable wood capable of being
polished to a high luster.

Mahogany is found in two grades — Honduras and Spanish.
The Honduras mahogany has a coarse, loose, and straight
grain without much curl. The Spanish mahogany is dark,
has a very fine close texture and considerable curl, and is
free from any tendency to warp. Because of its high price,
it is often veneered on some cheaper wood.

Hickory wood is very heavy, hard, and close-grained. It is
used for clubs, handles of tools, etc.

Ash is of two kinds, black and white. It resembles oak
to a great extent, but when worked is not so likely to split.

Beech is a very close, tough wood resembling a pale birch
in color. Its surface has a somewhat speckled appearance.

Birch is a very close-grained wood, strong, and easily
worked. It is pale, yellowish brown in color.

Cedar resembles mahogany, although more purplish in
color. It has no curl and is free from any tendency to warp.
The best varieties have a peculiar aroma which is offensive
to moths; for this reason, cedar chests are used for clothing.

It is impossible to describe the grains of woods in such a
way that one can be readily distinguished from another. Yet
with a little practice the eye quickly learns to note their
characteristics and the experienced wood-worker c&ji tell
pne kind of wood from another at a glance.

TREES 395

Questions

1. How is wood obtained?

2. Name the principal parts of a tree.

3. Draw a sketch showing the structure of wood. Name the

parts.

4. Why is summer wood darker than the spring wood?

5. Why does the wood of an oak and a pine become darker
after it has been in the trees, some years?

6. What is sap-wood? Why does it rot quicker than the heart-
wood?

7. What are the whitish lines running from the center of the
cross-section of an oak tree?

8. Explain the difference between maple and pine wood.

9. For what is walnut wood noted?

10. Describe the principal uses of cedar wood. Why are cedar
chests used to store clothing?

11. For what is hickory wood principally used?

12. Describe the kind of lumber which comes from an elm tree.

13. What is an annual ring?

CHAPTER XXXII

LUMBER

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442. Two Types of Lumber Trees. — The term lumber is
applied to timber or trees which have been cut and sawed
into a form suitable for commercial use. Ordinary planks
are a familiar example.

Not all trees furnish good lumber. The woods used in
the various trades are obtained from two kinds of trees —
forest trees, those that bear cones and have evergreen foliage;
and shade trees, those with broad leaves. Some lumbermen
speak of all lumber from the evergreen trees as softwood,
and that from the broad-leaved trees as hardwood. Although
correct in a general way, there are exceptions to this classifi-
cation, as poplar and sycamore woods, while very soft in
texture, are classified as hardwoods. Hardwood is close-
grained and resists decay for a long time, while softwood is
coarse-grained and easy to work. Hardwoods are extensively
used for building construction, furniture, floors, etc. Soft-
woods are used in the manufacture of cheap wooden forms,
such as ironing-boards, etc.

All the evergreen trees have a wood that is soft, light, and
easily worked; they also contain considerable resin. The
principal woods taken from this type of tree are white pine,
Georgia pine, spruce, hemlock, larch, and cypress.

The wood from the broad-leaved trees may be divided into
three grades: soft, close-grained hardwood; open-grained
hardwood; and dark-colored woods. . The poplar or white

396

LUMBER 397

wood is soft-grained; maple, birch, beech, and holly are
close-grained hardwoods; oak, chestnut, elm, and ash
are open-grained, light-colored hardwoods; black walnut,
cherry, ebony, mahogany, rosewood, maple, cedar, brazil-
wood, satinwood, and boxwood
are dark-colored, decorative
woods and are used where beau-
ty and fine grain are desired.

443. Chief Source of Com-
mercial Lumber. — Most com-
mercial timber comes from
forest trees. Since trees de-
pend on the sunlight for their
growth, it follows that trees
growing in the open fields, as
do the shade trees, have a full
crown and a short trunk. They
yield, consequently, compara-
tively little lumber and even
that little is of a poor quality,
since it contains many knots.

Trees grown in the forest,
where light enters only through
the top of the crowns of the
older trees, tend to grow tall and

straight in the struggle to the ^i^TouSSK
light. As the crown develops, branches, the result of sun-
*k i * ■ J u iT light on aU sides,

the lower twigs and branches

die, because the light and heat of the sun are cut off while
the trunk is small in diameter and while the branches
themselves are small, Thus the planks of forest trees are

398 APPLIED SCIENCE

straight and long and furnish excellent material for com-
mercial use.

444. Felling Timber.— Timber should not be cut until
it has reached its maturity. Before this time it contains
too much sap-wood. The time best adapted for cutting
timber is either midsummer or midwinter. In July or
August, the sound trees can be easily distinguished from the
unsound ones by the fact that the leaves of the former remain

Fiq. 189.— Cutting Forest Trees.

green while those of the latter become yellow. Trees are
felled by either chopping or sawing them near the base (Fig.
189). The small branches are then removed so that only
the stems (logs) of the trees remain. These logs are carried
on sleds to a saw mill (Fig. 190), usually situated near a

LUMBER 399

stream, and there, by means of a carriage constructed to
gauge an exact size, they are fed to a circular saw. The
logs are usually cut by one of two methods: (1) flat sawing,
by which the tree is sawed from one end to the other and
is made into planks; or (2) quarter or radial sawing, by

Fig. 190.— A Lumber Mill.

which the logs are first sawed into quarters, and each quarter
is then sawed into planks with the cuts at right angles to
the annual rings. The pieces taken off are called slabs.
Before the logs are placed in the circular saw, all knots, wires,
and nails are removed.

446, Grain and Figure. — When we examine the structure
of lumber,, we notice that it is composed of bundles of fibers,
or threads, called the grain. When the annual rings are wide,
the wood is said to be coarse-grained. If the rings are narrow
the wood is called fine-grained. Imperfections in the grain
of wood are very common and arc responsible for peculiar

400

APPLIED SCIENCE

1 -:

patterns and varied colorings. Fine-grained woods, such as
white oak, are capable of taking a high polish and when
finished in this way produce a beautiful luster.

446. Cutting Boards and Planks. — Planks may be cut in
four ways: (1) along the grain, (2) across the grain, (3)
square to the grain, and (4) oblique to the grain. The easiest
cut is along the grain, as the wood fibers are then removed
easily and smoothly as the cutting edge passes over the sur-
face. When a cutting edge moves across or at right angles
to the grain, it tears out a mass of fibers, and splinters the
surface badly. If the cutting edge is held vertically and
drawn square across the fiber lengths of the board, the fibers
on the surface are snapped apart. When lumber is sawed
in this way it is called "cutting square to the grain." A
sharp cutting edge is necessary to perform this cut effectively
as considerable force must be applied and very fine cuts made.

"Oblique to the grain" refers to an angular cut and is a
combination of "along the grain" and "across the grain"
cuts. Such a cut is made when it is necessary to protect the
ends of the fibers.

Before using a cutting tool, it is advisable to examine the
wood to see the way the grain runs so that the tool may be
moved in the direction to give the best results. The proper
direction may be determined by an examination of the grain
on the adjacent side of the surface.

447. Seasoning of Lumber. — Since between 20 and 60%
of the weight of freshly cut lumber is due to moisture, practi-
cally all wood, before being put to use, is either seasoned in
the air or dried in a kiln. Some lumber is subjected to both
processes. The main objects of seasoning are : (1) to increase

LUMBER 401

the durability of the wood in service, (2) to prevent it from
shrinking and checking, (3) to increase its strength and stiff-
ness, and (4) to decrease its weight. The sooner wood is
seasoned after being cut, the less is it likely to be injured

by the insects which attack unseasoned wood and cause it
to decay rapidly. Wood that is to be treated with a preser-
vative needs, in nearly all cases, to be seasoned as much as
wood that is to be used in its natural state.

The natural method of drying consists in stacking the
wood in horizontal piles and exposing it to the air Fig. (191).
Flat or horizontal piling may be done in two ways: (1) with

■
i

l '

! \

i :

i t

402 APPLIED SCIENCE

the ends of the boards toward the alley — endwise piling;
and (2) with the sides toward the alley — sidewise piling.
The stacks are arranged to slope from front to rear and to
lean forward so that water dripping from the top falls to the
ground without trickling down over the courses below. The
stacks should be so located in the yard that the prevailing
winds blow through them rather than against their ends.
Lumber loses from 15 to 20% of its moisture by this method
of drying. It is generally sold in this condition and is ready
to be used for such purposes as rough construction, sheath-
ing, siding, studding, subfloors, and other structures in
which subsequent shrinkage, if any should take place, would
not be a serious factor. Lumber destined for use in the in-
terior of heated buildings, however, especially in places where
considerable shrinkage would be evident, as in flooring or
furniture, must be dried still more so that no shrinkage will
occur after the wood is in place. Wood for such purposes
should contain only between 5 and 8% of moisture.

448. Kiln-Drying. — Lumber is kiln-dried (Fig. 192) when
it needs to be seasoned quickly, or when the yard-owner
does not wish to carry large stocks in his yard. A kiln
is used also to dry partially air-seasoned, or even fully air-
seasoned material, for special uses. The main problem in
f kiln-drying lumber is to prevent moisture from evaporating

from the surface of the pieces faster than it is brought to
the surface from the interior. When this happens the surface
becomes considerably drier than the interior and begins to
shrink and split. The evaporation from the surface of wood
in a kiln can be controlled to a large degree by regulating
the humidity and the amount of air passing over the wood.
A correctly designed kiln, especially one for drying the more

LUMBER 403

difficult woods, should be constructed and equipped in a
way to insure such regulation.

A dry kiln may consist simply of a box in which lumber
can be heated, or of a good-sized building or group of build-

Fio. 192.— A Dry Kilo.

ings (battery) containing steam pipes, condensers, sprays,
and various air passages capable of adjustment to regulate
the amount of ventilation. The elaborateness of the kiln
depends, of course, mainly upon the value of the lumber that
is to be dried. Kiln-dried lumber is valuable if it is to be

404 APPLIED SCIENCE

used immediately in a warm room, and is to be kept warm
and dry, until treated with some sort of paint filler that will
cover the wood and prevent the penetration of moisture. For
instance, if a piece of kiln-dried wood is exposed to the air,
it will absorb moisture until it soon has the same amount
as before being dried. Soft lumber, such as pine, spruce,
hemlock, etc., may without serious harm be kiln-dried as
soon as cut from the log, but hardwood, such as oak, hickory,
etc., should be previously air-dried for at least one year.
Wood must be seasoned very carefully in order to obtain
the best results. Sometimes as much as 20 to 25% of the
seasoned lumber in a yard has been rendered unfit for use
by defects which had their origin in the drying process.
Hence the necessity of knowing the right method of drying
wood.

449. Classification of Sources of Lumber. — The United
States produces many varieties of lumber. The following
list shows in brief form the particular sources of the various
types.

450. Yellow Pine. — Yellow pine lumber, of which there are
many varieties, is produced chiefly in the southern states. The
principal kinds of yellow pine are:

1. North Carolina pine, from Virginia, North Carolina, and
South Carolina.

2. Long-leaf pine, commonly called hard pine and Georgia pine,
from the Gulf states.

3. Loblolly pine, generally called short-leaf, old-field, rosemary,
or Virginia pine, from Virginia, North Carolina, South Carolina,
Arkansas, the Gulf states, and Georgia.

4. Short-leaf pine, chiefly from Arkansas, Virginia, North
Carolina, South Carolina, Louisiana, Mississippi, and to a less extent
from the other yellow pine states.

LUMBER 405

5. Slash (or Cuban) pine, from Georgia and the Gulf states
east of the Mississippi River.

6. Scrub pine, also called Jersey pine, from the Middle Atlantic
states.

7. Pitch pine, from the Middle Atlantic and northern states.

8. Spruce pine, from the Gulf states.

9. Pond pine, from the South Atlantic states.

10. Sand pine, from Florida and Alabama.

11. Table-mountain pine, from the Appalachian Mountains.

12. Western yellow pine, from every western state between
South Dakota and the Pacific Coast.

13. Bull pine, commonly called California white pine, New
Mexico white pine, western soft pine, or white pine, from the same
states as western yellow pine.

451. Cypress. — The commercial cypress wood is known as
bold cypress. The principal source of cypress is Louisiana, but
some is cut in the Atlantic and Central states.

452. Maple. — The lumber trade recognizes two kinds of maple
— hard and soft. Hard maple lumber comes from the sugar maple
tree and soft maple lumber from the silver and red species. These
three species grow all over the eastern half of the United States.
Sugar maple and silver maple are lumbered principally in the
northern states, while red maple is the most important timber tree
in the southern states.

453. Red Gum and Redwood. — The red gum tree is cut in
the lower Mississippi Valley and also farther east and north. Red
(or sweet) gum, commercially known as "sap gum," is the sap-wood
of the red gum tree.

Redwood lumber is found chiefly in California, but is present to
a small extent in southern Oregon.

454. Cedar. — A number of species are grouped under the com-
mon name "cedar." The several species rank as follows in im-
portance as lumber producers:

406

APPLIED SCIENCE

1. Western red cedar, the source of three-fourths of the shingles
made in the United States, is cut from lumber in Washington,
Oregon, and Idaho.

2. Port Oxford cedar is cut mostly in Oregon.

3. Northern white cedar, or arbor-vitae, is cut in the Lake states
and northeastern states.

4. Incense cedar is cut in California.

5. Southern white cedar, often called juniper, is cut in the
Atlantic Coast states.

6. Red cedar is cut chiefly in Tennessee, Florida, and Alabama.

7. Yellow cedar is usually cut in Washington.

' t

455. Douglas Fir. — Douglas fir is cut in the western states and
is available in larger stands than any other single species in the
I'nited States. The wood is quite similar to that of long-leaf pine
in many of its properties and uses. It is sold under the name of
Douglas fir, Oregon fir, red fir, yellow fir, Douglas spruce, and
Washington fir.

456. Oak. — The several commercial oaks furnish the bulk of
hardwood lumber. The lumber trade calls all oak lumber either
white or red oak. These trade names are based on the appearance
of the two general kinds of lumber cut from oak trees, white oak
lumber being light in color and dense, and red oak lumber being
somewhat reddish and porous. Since these two kinds of lumber
are supplied by distinct groups of trees, the trade distinction is
logical. The bulk of oak lumber is cut from less than a dozen
species, the largest part being furnished by white oak and red oak,
which are common throughout the eastern states. Chestnut oak
and Texas red oak rank next in importance.

The following is a list of the principal commercial oaks :

White Oak

1. Chestnut (or rock) oak occurs in the Appalachian Mountain
region.

2. Post-oak and bur-oak have about the same range as white
oak, but are not so abundant.

LUMBER 407

3. Overcup oak and cow (or basket) oak are the most important
of the southern white oaks.

Red Oak

1. Texas red oak furnishes the main supply of red oak lumber
in the lower Mississippi Valley.

2. Pin oak occurs in many eastern and central states.

3. Scarlet oak is a northern and northeastern tree.

4. Yellow (or black) oak is found in most states east of the Rocky
Mountains.

5. Willow oak is of commercial importance in the southern
states only.

457. White Pine. — White pine is the familiar white pine of
the Lake states, the Northeast, and the Appalachian region.

Norway (red) pine is lumbered in the Lake states and farther
east; though sometimes called red, it is really a yellow pine. The
better grades are often sold with white pine, but also have a market
under their own name.

Jack pine is a small tree of the Lake states, and is used only to
a limited extent. Western white pine, sometimes called silver pine,
supplies the white pine lumber cut in Idaho, Montana, Washington,
and to a limited extent in Oregon.

458. Hemlock. — Eastern hemlock is lumbered in the Lake
states, the northeastern states, and the Appalachian region. West-
ern hemlock is the main source of the hemlock lumber in the north-
western states, and its production is increasing. Although the mill
value of western hemlock is lower than that of eastern hemlock,
the former is of superior quality and is often sold as Douglas fir.
The western mountain or black hemlock and the Carolina hemlock
of the Appalachian region are lumbered only occasionally.

459. Spruce. — Several species of spruce are cut for lumber,
but red and Sitka spruce furnish the greater portion. Red spruce
is the most important species in the northeastern and Appalachian
regions, as are northeast black spruce and white spruce lumber in

408 APPLIED SCIENCE

the Lake states. Englemann's spruce is the source of spruce lumber
in the Rocky Mountain region.

460. Chestnut. — Chestnut is lumbered throughout most of
the central and eastern states. During late years, a chestnut bark
disease has killed much of the timber.

461. Yellow Poplar. — Yellow poplar is known in the eastern
states as whitewood poplar, or tulip poplar.

1 462. Birch. — Two species furnish the bulk of birch lumber

1 but no distinction between them is recognized in the trade. Yellow

birch is the principal source of lumber in New England, New York,
and the Lake states. White sweet (or cherry) birch is the principal
species cut in Pennsylvania and West Virginia. In northern New
1 i England paper birch, often called canoe or white birch, is the chief

i ' source of material for spools, toothpicks, and novelties; little of

' ; it is cut into lumber. River (or red) birch is poorer in color and

\ figure than the other birches, but is sometimes cut for lumber

J, ^

f; in the southern states. In the lumber trade, "red birch" means

lumber cut from the heart-wood of yellow or sweet birch. Western
birch is sawed into lumber to a slight extent on the Pacific Coast.
White (or gray) birch is a small New England timber tree which
possesses only a minor commercial value.

463. Larch. — The term larch isused to covertwo closely related
and similar species: tamarack, cut in the northern states from Min-
nesota to Maine; and western larch, cut in Montana, Idaho, Wash-
ington, and Oregon. Although sold for less at the mill, the lumber
of the latter is more valuable than tamarack, because, the tree
being much larger, the wood has more strength and figure and better
finishing properties.

464. Beech. — Beech wood lumber is cut chiefly in the states
east of the Mississippi River.

466. Basswood. — While three species of basswood trees are
cut for lumber, no distinction between them is made on the lumber
market. Basswood is grown chiefly in the New England and
northeastern states.

LUMBER 409

466. Ash. — Three kinds of ash are important sources of lumber.
White ash is cut mostly in the Central states and the Northeast,
and to some extent in the Lake states. A great deal of the ash
lumber cut in the Lake states comes from the black ash, while the
same species is cut to considerable extent in the Northeast. Green
ash is the principal source of ash lumber in the southern states.
The lumber trade divides ash lumber into white ash and brown ash;
brown ash lumber comes from the black ash tree, while white ash
lumber is cut from the white ash and green ash tree. In the Pacific
Coast states, Oregon ash is sometimes cut, while red ash is used
to a limited extent in the east.

467. Elm. — Elm lumber is sold as soft and rock elm. White
elm and slippery elm are the botanical species from which soft elm
is obtained. White (or American) elm is found in all states east
of the Rocky Mountains and furnishes most of the soft elm lumber
sold. Slippery (or red) elm covers the eastern half of the United
States, and is next to white elm in importance. Cork (or true rock)
elm is found in the northern states, and is cut mostly in the Lake
states. The wing elm and cedar elm of the lower Mississippi Valley
are only occasionally cut for lumber.

468. Cottonwood. — Cottonwood lumber is cut from a number
of related species, but the common Cottonwood tree furnishes the
bulk. Cottonwood is found in the whole country east of the Rocky
Mountains, but is lumbered principally in the lower Mississippi
Valley, where swamp cotton wood and common cotton wood are cut.
Aspen, or poplar (often called popple) is cut mostly in the Lake
states and the Northeast, but also occasionally in the Rocky Moun-
tains and westward. Large-toothed aspen, an eastern species, is
not usually distinguished from the other.

469. White Fir. — White fir, also called balsam fir, is cut only
in the west. It is the principal source of white fir lumber in all the
western states, except Oregon, Washington, Idaho, and Montana.
Other species, sold as white fir and therefore here included under
that name, are grand fir, silver fir, noble fir, red fir, and Alpine fir.
The cut of white fir lumber in Idaho and Montana is increasing.

410

APPLIED SCIENCE

470. Sugar Pine. — The sugar pine is the largest pine tree in
the United States. Its wood resembles white pine, and the uses
of the two are similar.

471. Balsam Fir. — Balsam fir is the name of the tree that fur-
nishes the balsam fir lumber which is lumbered in the Northeast
and in the Lake states.

472. Tupelo. — Tupelo lumber is cut in the Gulf states from
cotton gum trees, commonly called tupelo, and is sold under that
name. Black gum (or pepperidge) is next in importance and is cut
in the Atlantic and Central states; the lumber is sold both as tupelo
and black gum. A little lumber is made from the water gum tree
of the Southern Atlantic states.

473. Hickory. — Several species of hickory are cut for lumber
in this country; the wood grows naturally nowhere else in the world.
The species most cut are shagbark, shellbark, and pignut. The
lower Mississippi and the Ohio valleys supply the bulk of the hickory
lumber. Industries which use the largest quantities of hickory
prefer it in the form of blanks, squares, etc., and it is consequently
usually more profitable to saw hickory into such dimension stock
than into lumber.

474. Walnut. — Walnut lumber is cut from the common black
walnut which grows throughout the eastern half of the country,
but is most abundant in the central states.

til

Questions

i ,- ,

1. What is the grain of wood?

2. To what are the peculiar figures and coloring'in wood due?

3. What is hardwood?

4. What is softwood?

5. Name some of the common varieties of pine and tell how
they differ.

6. What are seasoning cracks? How do they form?
7» What is a forest tree?

LUMBER 411

8. What is a shade tree?

9. How does a forest tree differ from a shade tree?

10. How are the shade or broad-leaved trees divided?

11. How are trees classified as to size?

12. Describe the growth of lumber.

13. When should timber be cut?

14. How much moisture has green lumber?

15. How is lumber seasoned?

16. What are the advantages of natural drying?

17. What are the advantages of kiln-drying?

CHAPTER XXXIII

DEFECTS OF WOODS

475. Chief Defects — Knots. — The principal defects which
are liable to appear in commercial lumber are: (1) knots,
(2) checks, (3) warping, and (4) rottenness. Knots, such
as we find in boards (Fig. 193) are the marks left in the tree

J or No. 2 A or No. 1 C or No. 3 No. 1 Common
Fia. 193.— Four Grades of Yellow Pine Timber. A, or

No. 1, is the best; B, or No. 2, is the next; C, or No. 3,

is the next; and No. 1 Common is the poorest grade.

Notice that the poorer grades have more knots and

defects in them.

trunk by branches which have disappeared. When the
lower branch of a tree dies for want of light, as it frequently
does, the annual layer of new wood is no longer deposited
upon it. The dead branch, at the place where it joins the
tree, makes a little hole in the first coat of living tissue
formed over the trunk after the branch's death. The edges

DEFECTS OF WOODS 413

of this hole make a, sort of collar about the base of the dead
branch, and, as a new layer is added each year, they press
it more and more tightly. So strong does this compression
by the living wood become that at last what remains of the
dead tissue has so little strength that the branch is broken
off by a storm or even falls of its own weight. Then in a
short time the hole closes and after a while little or no exterior
trace of the knot remains.

476. Shrinkage of Wood — Checks. — Waterexists in wood
in two conditions: (1) as water absorbed in the cell walls,
and (2) as free water contained in the
cell cavities. Whenwoodcontainsjust
enough water to saturate the cell walls, ,
it is said to be at the "fiber satura-
tion point." Any water in excess of
this which the wood may contain is
in the form of free water in the cell
cavities. The removal of the free i
water has no apparent effect upon the
properties of the wood except to re-
duce its weight, but as soon as any
of the absorbed water is removed the
wood begins to shrink. Shrinkage (Fig. 194) is due to the
contraction of the cell walls, and sets up stresses which tend
to cause the wood to "check" or crack. "Check" is a term
used to denote cracks extending radially and following the
pith rays; lumber splits lengthwise only very slightly.

Since the free water is the first to be removed, shrinkage
does not begin, as a general rule, until the fiber saturation
point is reached, though in the case of some of the oak woods,
shrinkage begins above this point. For most woods, the

414 APPLIED SCIENCE

fiber saturation point corresponds with a moisture content
of from 25 to 30% of the dry weight of the wood."

When lumber is kiln-dried too soon, it becomes case-hard-
ened; that is, its outside becomes hard before the sap from
the center can evaporate (Fig. 195). During the process of

Feu. 195. — -Result of Case-Hardening.

drying, the lumber shrinks across the width of the board
and also in thickness, but rarely to any extent in its length.
The sap naturally escapes most readily from the ends of the
lumber. These ends often become quite dry while the
center of the plank still contains a great deal of moisture.
The ends of the plank then tend to become narrower than
the center and in consequence split or "check."

477- Warping, — Warping is another serious delect which
occurs in wood, and must be very carefully guarded against.

DEFECTS OF WOODS 415

Warping is the result of unequal drying or shrinkage. If
one side of a board is fully exposed to the air or heat while
the other side is less exposed, the side most exposed will dry
more quickly and, of course, shrink. This unequal shrinkage
causes the board to warp or curl somewhat on that side.
To prevent this occurrence, lumber is usually piled with
sticks between each course or layer, so that the air may
penetrate to the under side of each board. In some of the
modern kiln-dryers, the lumber is dried under pressure, the
piling sticks being replaced by steam pipes. When the lumber
is all piled, the whole mass is clamped together, so that
warping is impossible. Some wood has a natural tendency
to warp even before it is dried at all, and unless fastened,
cannot be kept straight. Such lumber comes from the
outside cuts obtained in flat sawing. In many cases it is
of commercial use, but is of an inferior quality, and should
not be used in the modern shop. The natural tendency in
warping is for the annual rings to straighten out. Therefore
boards cut nearest the heart are the best.

478. Cause of Rottenness. — Little plants, called fungi,
and insects attack wood in many ways and cause it to rot.
Some fungi kill the roots of trees; some grow upward from
the ground into the trees and change the sound wood of
the trunks to a useless rotten mass; and the minute
spores (or seeds) of others float through the air and come
in contact with that part of the tree which is above ground.
Wherever wood is exposed, there is danger that dis-
ease may form. Consequently all wounds, such as those
made in pruning, should be covered with some sub-
stance like paint or tar to exclude the air and the spores it
carries.

416

APPLIED SCIENCE

479. Effects of Seasoning on the Strength of Wood. —
Seasoning, as a rule, increases the strength of wood. The
increase in strength, however, gained by this lowering of the
moisture content is somewhat greater for small, clear pieces
than for timbers of structural size, because seasoning does
not, as a rule, cause any appreciable defects to appear in
the small pieces, while it often develops checks in large
timbers.

Questions

1. What are the principal defects in lumber?

2. What is a knot?

3. What causes shrinkage of wood?

4. What causes warping?

5. What causes wood to rot?

6. The strength of wood depends upon certain factors,
are they?

7. Draw a sketch showing the structure of wood.

8. Describe the different methods of cutting wood.

What

CHAPTER XXXIV
HAND WOOD-WORKING TOOLS

480. Working Edge. — Before wood can be worked to
measurements, it is absolutely necessary to have at least
two adjacent faces "true" — that is, flat and smooth and at
right angles to each other. These two surfaces are called
the "working faces," and the edge between them the "work-
ing edge." These surfaces are used as a foundation from
which to mark the lines for guiding the cutting tools. The
lines drawn on the wood show the form of the object to be
made and the waste parts to be removed; they are known as
the layout of the work.

481. Carpenters' Tools — Saws. — Carpentering involves
either benchwork or toolwork, and requires the use of a great
variety of more or less complicated tools. The carpenter
is expected to care for and sharpen these tools and must, of
course, know their use and construction.

The principal carpenters tool is the hand-saw, which
consists of a thin piece of steel, called the blade, along the
edge of which teeth are cut; the handle end of the blade,
called the head; and the other end, called the point. The
blade is considerably wider at the head than at the point.
Hand-saws are of two kinds: rip, and cross-cut. The rip-saw
is used for cutting with the grain of the wood, and the cross-
cut for cutting across the grain. The steel for a good saw
is tempered to a high degree of hardness. It is then ham-
27 417

APPLIED SCIENCE

HAND WOOD-WORKING TOOLS 419

mered to make it level and tough, and ground to give a
uniform, tapering thickness. Finally, it is polished to a
high degree so that it may run easily.

482. Setting a Saw.— A saw in order to cut well and move
freely must have what is called set. Setting a saw consists
in bending its teeth alternately from side to side, thus mak-
ing the cut wider than the thickness of the blade and pre-

Fig. 197. — Enlarged View of Rip Teeth.
venting the blade from sticking in its kerf (the groove or
opening made by the saw) . The amount of set varies accord-
ing to the use for which the saw is intended. A saw for
green or undried lumber requires a greater set than one for
well-seasoned lumber, and a cross-cut saw requires more
set than a rip-saw. The pitch of the saw tooth is the angle
formed by the slanting edge of the tooth with a line at right
angles to the edge of the saw blade. The amount of pitch,
like the amount of set, depends upon the kind of work for
which the saw is to be used; rip-saws, for example, require
more pitch than do cross-cut aaws.

420 APPLIED SCIENCE

483. The Operation of Sawing.— The opera-
tion of sawing consists, first, in cutting the wood
or metal, and second, in widening the cut in
order that the tool may penetrate the material
and then allow the cutting edge to go on (Fig.
196). In widening the cut, the fibers must be
pressed apart. The force that is required to
carry the saw forward, when the cutting edge
is just entering the wood or metal, is due to the
resistance of the material; the larger the angle
of the cutting edge, that is, the greater the
difference in direction between the stock and the
cutting tool, the more abrupt will be the turning
of the shaving or the chip of the metal, and
consequently the greater the resistance tosawing.
Experienced mechanics know that the smaller
the angle of the cutting tool that the metal or
wood will allow without breaking the tool, the
easier it is for the worker.

484, Action of a Rip-Saw. — The object of a
rip-saw is to cut or saw lumber lengthwise with
the grain. This type of saw has a different tooth
action from that of the cross-cut saw. The tooth
of the rip-saw (Fig. 197) has a straight front,
and its cutting edge strikes (Fig. 198) the fiber
of the wood at an angle of about 90°. It sepa-
rates the fiber at one place only and the front

Looking of the tooth wedges out the piece of wood. This

Edae^of ^ orm °* tooth does not sever the fibers because

Rip - Saw the line of the cutting edge runs lengthwise with

View) the fiber, instead of across it. The saw does not

HAND WOOD-WORKING TOOLS 421

entirely clear itself in the groove and therefore cannot
cut freely. While the cross-cut saw is better for ripping
lumber than arip-saw is for cross-cutting, ripping lumber
with a cross-cut saw is slow and arduous work.

486. Action of a Cross-cut Saw. — The purpose of the
cross-cut saw is to cut across the grain. The teeth are

Fio. 199.— Enlarged View of Cross-Cut Teeth.

practically V-shaped (Fig. 199) with the points set alter-
nately to the right and left. The front and back of each tooth
are sharpened and beveled. The outside edge of the front
of the saw-point (the portion set) does the cutting.

The action of the cross-cutting hand-saw is as follows:
An extremely light, short cut is made across the grain of the
lumber, so that the extreme points on both sides of the
cutting edge (Fig. 200) make parallel scorings, indicating the
width of the rip apart. This action, which is similar to the
fine cutting of a knife across the face of wood, starts the cut.
Pressure is then applied to the saw, and the teeth enter

422 APPLIED SCIENCE

deeper and deeper, gradually bringing into action
the cutting edge on the outside front of the points
of the saw. The forward motion of the saw blade
causes the points and cutting edges to strike the
fibers of the wood at a right angle to their length,
thus separating them from the main body of wood
on each side of the blade. A continuation of the
pressure or thrust carries the teeth in farther and
farther, until the full "bite" is taken. The saw
points are continually scoring the wood on each
stroke. The outside edges of the saw part the
fibers, and the beveled front edge of each tooth
in the cut acts like a chisel in crumbling and dis-
lodging the upper portion of the ridge of wood left
between the cutters. The pieces of wood are
carried out of the kerf by the throats or gullets at
each thrust of the saw, until the board is com-
pletely cut.

486. How to Handle a Saw. — A carpenter
should use his hand-tools so as to obtain the
greatest results with the least effort, and in this
manner conserve his energy. The saw should be
grasped by the handle with the thumb and fore-
finger extended, so that the handle fits in the
hollow of the hand and gives an easy "hang" to
the saw. It should be guided by the left thumb
F '°- 2 ??- — knuckle pressing against the blade. This move-

D o w n ment keeps it on the line and prevents it from

a£ai. jumping-

Saw (En- Beginners are ir.clined to grasp the saw with all

View). the fingers clasped around it. This tends to make

HAND WOOD-WORKING TOOLS 423

the grasp cramped, and control of the saw more difficult.
The cut should be started by making a few short and light
drawing strokes, so as to get the saw on the line. It should
then be moved steadily with long strokes and with the blade
at an angle of 90° to the work.

487. Cutting Action of the Chisel. — A chisel is a cutting
tool which cuts out pieces of stock in the form of shavings.

. Fia. 201.— Cutting Action of the Chisel.

The mechanical principle upon which it operates is that of
the wedge (Fig. 201). The cutting edge is broad and sharp
and the cut acts by a separating process, called "slitting,"
which is similar to the paring of a potato. The cutting edge
separates the fibers of the wood lengthwise with the grain by
raising the shaving or chip and tearing the wood fiber on the
side. The thickness of the shaving of the wood is deter-
mined by the angle at which the chisel is held, the amount
of bevel on the cutting edge, the force of the pressure exerted,

424 APPLIED SCIENCE

(!>,. HotTirui nf onftnoco /,i- Viarrlnocic ,if tin. wnnl Kainn

HAND WOOD-WORKING TOOLS 425

prevented from entering beyond this point because of the
thickness of its bevel or back. If considerable pressure is
applied so as to force the cutting edge into the wood, the
friction between the wood and knife becomes so great that
the blade is jammed or wedged in the board.

489. Cutting Action of Saw and Knife Compared. — In

cutting hard material, such as wood, sufficient material must
be displaced to allow the upper part of the cutting tool to
enter the wood. This allows the cutting edge of the blade
to be constantly in contact with the wood and prevents
side friction and binding. The side friction and binding
of the cutting edge may be reduced considerably by the
application of lard or a lubricant to the side of the tool.
The difficulty of cutting will then be greatly lessened. A
knife edge scores the wood; a chisel cuts by separating
and removing the material ; and a saw employs in a general
way the actions of both the knife and chisel; that is, the
saw in action removes successive portions of material by
the processes of cutting and tearing. The material is not
removed in the shape of long shavings, but in small particles,
commonly called sawdust.

490. Grinding of Wood-working Tools. — The cutting
edge of wood-working tools tends, of course, to become dull
after being in use for a time. This edge can usually be
sharpened by a whetstone, but after a number of whettings
it will be found necessary to use a grindstone. The whet-
stone removes the metal very slowly, while the grindstone
removes it rapidly. A blunt tool makes cutting hard and
does imperfect work, for when excessive force is necessary
the sense of direction is lost, $tnc} the tool slips or digs in,

426

APPLIED SCIENCE

'•

Wood-working tools should be ground on a grindstone of
medium fine grit to which water is freely supplied. The
water is used for two purposes: (1) to prevent the heating
of the tool (heating destroys the temper and causes the tool
to be "soft"); (2) to wash away the waste material which
collects between the fine pieces of grit of which the surface
of the grindstone is made up.

The grindstone should be frequently "trued up" by some
suitable device so as to keep its face perfectly round and
straight, and to break away the rounded projections and
present fresh, sharp projections for action.

491. The Brace and Bit. — The brace is a tool used to hold
and turn the various kinds of bits used in boring, drilling,
and countersinking, or in driving screws. Braces are of two
kinds — the ordinary brace and the ratchet brace. The
latter type is fitted with a ratchet in the grip, so that the bit
can be turned only in one direction. This mechanical fea-
ture is necessary where lack of space prevents a complete
revolution of the brace, and also when boring in hardwood,
or turning large screws.

The most common forms of bits used in the brace are the
following:

(a) The auger bit. This bit has a spur to draw the bit
into the wood, two nibs for cutting the fiber, and two lips to
remove the waste which is brought by the twist to the surface.

(6) The drill bit. Bits of this kind are sharpened only
at the end of the twist. They are made of tempered steel,
and are used in boring either hardwood or iron.

(c) The countersink bit. This bit has a T-shaped cutting
end for enlarging screw holes, so that the screw head is
drawn down even with or below the surface.

HAND WOOD-WORKING TOOLS 427

(d) The screw-driver bit. This bit is like the blade end
of a screw-driver, and is used for driving large screws.

The mechanical principle underlying the brace and bit
is that of the wheel and axle. The circle (called the sweep)
formed by a complete revolution of the brace corresponds to
the wheel, and the circle made by the revolution of the bit
corresponds to the axle.

492, Description of Plane. — Another important tool is
the plane, and since it "cuts" its mechanical principle is that
of the wedge. The first planes used were comparatively
crude and were little more than heavy, thick wedge-shaped
cutters. The plane has been improved, however, until today
it is a very delicate tool consisting of a body in the bottom
of which there is a slit, called the throat, through which the
cutting piece, called the plane iron or blade, projects. The
end of the plane iron is sharpened on a bevel to a cutting
edge. A flat, curved piece of steel, called a cap iron, is
fastened against the plane iron about iV in. from the cutting
edge by a short, heavy screw, called the plane iron screw.
The cap iron serves to stiffen the plane iron, and also bends
and breaks the shaving, thereby preventing a splitting action
in front of the cutting edge. Just back of the throat of the
plane is the frog, fastened to the bottom by screws. The
object of the frog is to hold the plane and cap iron in place,
and to carry the thumb-screws by which the plane iron is
adjusted. The plane iron and cap iron are held firmly in
place against the front by means of a clamp worked by a
cam. The vertical adjustment of the blade regulates the
thickness of the shaving and is made by means of a thumb-
screw on the underside of the frog; the horizontal adjustment
of the plane iron is made by a lever just under the plane iron«

428

APPLIED SCIENCE

: 'i

1' ! '

493. Kinds of Planes. — Planes are made in different
sizes and lengths to suit different kinds of work. The jack
plane is about 13 in. long and is used for removing large
quantities of rough wood, leaving the piece fairly smooth.
The smooth plane is used for smoothing material which has
already been roughly smoothed and straightened. The
jointer plane is often 2 ft. or more in length, and is used
for straightening long and uneven material. The block
plane is about 6 in. long, and is used in planing the end
grain of wood, when there is no vise handy for holding the
piece.

A considerable degree of skill is required to sharpen and
adjust these planes properly for different classes of work.
The metal parts of wooden planes must be kept bright, and
the wooden soles true and free from grooves which may be
made by nails or particles of dirt. Iron planes, which
rust easily, must be kept well oiled, especially in damp
weather.

494. Chisels and Gouges. — Chisels are of two types — the
framing chisel, which has the handle fitted into a socket on
the end of the chisel; and the firmer chisel which has a tang
upon the handle. The framing chisel is used for heavy work
and the firmer chisel for light work. Chisels of varying
widths are used for cutting joints and are among the most
useful of the carpenter's tools. In striking the handle of a
chisel, a mallet should be used, as the hammer will cause it
to split. Chisels and all edged tools should be kept sharp and
free from rust, as a matter of economy of time and labor, and
of quality of workmanship. Gouges are similar to chisels,
except that their cutting edges are curved, and have an
inside or an outside bevel.

HAND WOOD-WORKING TOOLS 429

495. Description of Squares. — Squares are of two general
types— the framing square and the try-square. The fram-
ing square (Fig. 203) consists of a long arm, usually 24 in.
long, called the blade, and a short arm, usually 18 in. long,
called the tongue, both of which are made

from one piece of metal. One side of the
square is graduated to inches and frac-
tions of an inch; the other side bears a
board measure scale on the blade, and a
rafter measure table on the tongue. The
framing square is used in measuring
boards, testing corners, and setting the
bevel of boards and tools to various angles.
The try-square (Fig. 204) consists of
the blade, and a beam handle of wood or
steel, so attached that the edge of the
beam forms a right angle with the edge
of the blade. The blade is graduated into
inches and fractions of an inch. The try-
square is used in testing the end or edge
of a piece of material to see that it is
square with the adjoining surface, and also
to test the thickness of the piece.

Fig. 203.— St eel Fram-
ing Square.

496. Gauges. — The marking gauge is

a measuring instrument consisting of a beam over which a
head slides. The beam is graduated to inches and fractions
of an inch. In the head is a thick end for holding a marking
point, a pencil, or a spur of metal. The marking point or
pencil is used for laying out lines along the grain of the wood.
The spur, known as a slitting gauge is made sharp and strong
enough to cut through thin material. It is used to lay out

430 APPLIED SCIENCE

lines across the grain of wood. In some cases the gauge is
constructed with a handle like that of a plane.

Other tools in the use of which
the carpenter must acquire mani-
pulative skill are the spoke shave,
for smoothing curved surfaces; the
mallet, for driving chisels in heavy
cutting; the bevel, with movable

n. ™. t- a blade used in getting angles for

Fig. 204.— Try-Square. ° ° °

cutting rafter ends and other ma-
terial; screw-drivers of various types, such as ratchet and
spiral; hammers, flat and bell-faced; miter boxes; levels;
wrenches; awls; nail sets; rules; files; rasps; pliers; hatchets;
bench axes; and vises.

Questions

1. What is the meaning of "working face" in wood -working?

2. Explain the meaning of the term "working edge."

3. Describe the carpenter's saw.

4. How are saws classified?
6. How is a saw made?

6. What is the set of a saw? Why is it important?

7. What is a kerf?

8. What is the pitch of a saw?

9. Why is it necessary to use different pitches lor different
kinds of wood?

10. Explain the operation of a saw.

11. Explain the action of a rip-saw.

12. Describe the tooth of a rip-saw.

13. Describe the action of a cross-cut saw.

14. Explain the mechanical principle involved in handling a saw.

15. How does a shaving made by a saw differ from one made by
a chisel?

16. Name some of the factors that determine the thickness of
the shaving.

HAND WOOD-WORKING TOOLS 431

17. Describe the cutting action of a knife.

18. Why is it not possible to saw a board with a knife?

19. Compare the cutting action of a knife and a saw.

20. When should wood-working tools be ground?

21. Describe the kind of stone upon which wood-working tools
should be ground.

22. Why is it necessary to have the grindstones frequently tried?

23. Describe the brace and bit. What is the mechanical prin-
ciple involved?

24. Explain a wood plane.

25. Name the different kinds of planes.

26. Describe the kinds of chisels. Why should chisels be kept
clean?

27. Why is it necessary to use squares?

28. What is a gauge?

CHAPTER XXXV
POWER WOOD-WORKING MACHINES

497. Kinds of Machines. — Wherever possible, hard work
is done by machinery. This is particularly true in the manu-
facture of the movable parts of a building, such as doors,
gashes, window-frames, etc. Most work of this kind is per-
formed by means of band and circular saws, jointers, planers,
lathes, and machines for sandpapering and for making mold-
ings and tenons. The more simple machine processes consist
of such operations as " knocking out cores," i.e., cleaning the
mortises or slots made by the mortising machine; wiring slats
on rods for blinds; "coring out" or boring holes for blind
slats; making slats and small moldings for door paneling;
and so on.

Since machinery is so extensively used in carpentry work,
a knowledge of the construction and operation of wood-
working machines is very necessary to the wood-worker.

498. Power Saws. — Power saws may be classified under
three heads — circular, band, and scroll or jig. The circular
saw is used for sawing off, ripping, and the cutting of various
angles. The blade is held on a spindle or arbor which is
driven direct by a belt pulley fastened to the same shaft.
The arbor is usually supported by a frame, which in turn
supports the saw table.

The band saw is used entirely for sawing curves and irregu-
lar shapes of various kinds. It consists of an endless band

432

POWER WOOD-WORKING MACHINES 433

*
of steel with teeth cut into one or both edges and is generally

about iV to \ in. in thickness. The width ranges from
about { to 14 in. The band saw is operated over two rubber-
faced wheels placed directly one above the other. Between
the wheels is a saw table in which there is an opening through
which the saw runs.

The jig saw is used for sawing scrolls and curves that can
not be cut on a band saw. It consists of an upright blade
to which a reciprocating motion is given by a crank and
connecting rod, the saw frame sliding in vertical guides.
The great convenience of this machine is that the blade can
be removed and replaced in a very short time. By first
boring a hole through the piece to be cut, for instance, the
saw may be passed through the opening and refastened.
The cut can then be started in any desired direction.

499. Wood-Planer and Jointer. — The wood-planer is a
machine for smoothing rough boards or for cutting boards
to a required thickness. It consists of rapidly revolving
cutters, which chip off the surface of the board in minute shav-
ings as it is passed under the cutter by a suitable feeding
device. The feeding device usually consists of two rollers
placed a little closer together than the thickness of the
board.

The jointer consists of a table and a cylindrical cutter
over which the work is passed. It is used entirely for straight-
ening, smoothing, and beveling the edges of boards.

600. Turning Lathe.— The turning lathe (Fig. 205) is
used for drilling and turning articles of wood into round or
oval shapes. The way in which it is made may be under-
stood by reference to the figure. It has a solid frame of iron,

434 APPLIED SCIENCE

called a bed, supported on legs. On the left-hand side of the
bed is the head-fltock and on the right-hand side the tail-
stock. A belt passes around the cone pulley of the counter-
shaft and connects with the cone pulley of the head-stock,

fta. 205.— Wood-Turning Lathe.

causing the latter to turn round very fast. The power is
transmitted from the main shaft to the countershaft and
then to the machine. The tail-stock can be moved along
the slot in the top of the frame and fastened tight in any
place by screwing up the nut beneath it. The wood to be
turned is held in place by a chuck which turns very rapidly.
The workman rests his chisel on the rest, and holds it firm-
ly against the wood, which turns around against it; thin
screwing are thus pared off the wood until it is cut to
the shape wanted. A steady arm and hand and much care
are needed in turning, especially when hardwood is to be
cut.

POWER WOOD-WORKING MACHINES 435

501. Miscellaneous Machines. — Other wood-working
devices which may be briefly mentioned are the molding
machine, the shaper, and the boring machine. The molding
machine is used for cutting various kinds of ornamental
moldings for interior and exterior finishing. The work is
fed to the different shaped cutters by rollers.

The shaper is used for finishing edges in irregular shapes.
The cutters are interchangeable and thus are capable of
making a great variety of shapes.

The boring machine is used for drilling or boring holes
through wood. An augur or drill is fastened with a holder
in a revolving spindle which is operated by an automatic
feed or hand-lever.

The mortising machine is used for cutting mortises or
slots for the reception of tenons or ends which are shaped
to fit into such slots. The wood is placed upon the table of
the machine and the slot or mortise is cut by a drill arranged
in a chisel-shaped cutter. The drill removes most of the
stock, and the edges are squared and finished by the cutter.
This machine is operated by a foot-lever and can be set to
cut any depth or width of mortise.

The tenon machine is used only for cutting tenons. It
consists of four heads — two for roughing and two for finishing.
Very accurate work can be done with it.

The sandpapering machine consists of revolving cylinders
covered with sandpaper which polish the surfaces of boards
passed between them. There are, too, various automatic
machines used for grinding and sharpening saws and other
edged tools.

502. Prevention of Accidents. — The machinery used in
wood-working is exceedingly dangerous. It is important

436 APPLIED SCIENCE

therefore that the utmost care be exercised in its operation
and that all practicable safeguards be utilized. Since such
machinery is run at a high speed, the commonly exposed
positions of the belts are a constant source of danger to the
machine operators. Their loose clothing may easily catch
on these belts or on the pulleys over which the belts run,
and be the cause of a serious, even fatal, accident.

The greater number of such belts and pulleys can, however,
be readily guarded, as can exposed gears, sprockets, and
chains. Where it is necessary for the machine parts to be
readily accessible, the guards may be constructed so as to
be removable.

Because of the smoothness of the floors in wood-working
shops, the machine hand is always in danger of slipping and
falling on the machine he is operating. A rubber mat placed
in front of the machine and secured to the floor is one of the
best safeguards against such an accident. The mat should
be kept free from sawdust and renewed when torn or badly
worn, else it will fail to accomplish the purpose for which
it is provided.

503. Ordinary Saw-Guards.— A saw-guard is a device
designed to prevent the operator's hand from coming in
contact with the saw in case either the work or his hand
should slip.

504. Guards for Swing and Circular Saws. — There should
invariably be a cast iron or sheet metal guard over the top
of a swing saw, as well as acounterbalance on the swing bar
to throw the saw back from the workman. There should
be a positive stop at the end of the swing bar so that the
counterbalance, which is generally made adjustable, cannot

POWER WOOD-WORKING MACHINES 437

slip off. The slipping off of a counterbalance, due to a set
screw working loose, recently cost a workman his right hand.

The dangers incident to the use of circular saws are too
well known to require description. A "riving knife," or
"spreader," when properly attached to the table immediately
back of the saw, will spread the cut sufficiently to prevent
cramping. It is very important that cramping shall not
take place, as this usually stops the saw and throws the belt
off, or throws the work back on the operator, often with
serious results.

The riving knife is simply a piece of sheet steel mounted
in a vertical position back of the saw and preferably curved
to conform somewhat to its outline. The edge near the saw
should be a little thinner than the saw itself, so that the
saw cut will slide over it easily. The opposite edge should
be at least the thickness of the saw, or even of a slightly
greater thickness. The length of the knife will, of course,
depend upon the size of the saw with which it is used.

Another very simple device to prevent the work being
thrown back in case of cramping, consists of a board 4 or 5
in. in width, fastened perpendicularly to the ceiling directly
over the saw, and of such length that its lower end will just
clear the saw. The plane of the board should be at right
angles to that of the saw.

If a saw without a guard is permitted to run while the
operator is away, a small oblong wooden box placed over it
will serve as a safeguard to persons passing the table. If
practicable, this box or cover should have, in each end, a
dowel pin fitted in the table.

505. Jointer Guards. — The hand-planer or jointer is a
most dangerous machine when operated without a guard.

438

APPLIED SCIENCE

In using it, accidents often occur in unexpected ways. A
change in the grain of the wood, the striking of a knot, or
too heavy a cut may hurl the piece from the machine and
throw the workman's hands into the knives. Yet it may
be simply and easily guarded, so as to render it safer than
many other wood-working machines.

A workman should always try a jointer before using it,
for the knives may be set to take too heavy a cut. In such
a case the piece would be hurled back on him. In using a
jointer, the operator should not allow his hands to rest on
the portion of the stock which is over the knives if it is
possible to avoid doing so.

Questions

1. Why is machine-work more economical than hand-work?

2. Name the different kinds of power saws. How do they differ?

3. Describe the action of a band-saw.

4. What is a wood-planer?

5. What is a wood-jointer?

6. Trace the power from the main shaft to the parts of a turn-
ing lathe.

7. Describe a wood-turning lathe.

8. Describe briefly the following power machines: the shaper,
boring mill, mortising machine, and tenon machine.

9. Why is it possible to run wood-working machines faster
than metal-working machines?

10. Why must great care be exercised in running wood-vorking
machines?

11. Name some of the guards used on machines.

CHAPTER XXXVI
PATTERNS, CORES, FLASKS, AND MOLDS

506. Descriptions and Use of Patterns. — A pattern is a
wooden or metallic model of an article, made to size, from
which a mold is formed in sand. Pattern-making is the
art of making these wooden models. The cavity correspond-
ing to the pattern is subsequently filled with fluid molten
metal, which, when it has cooled and become solid, retains
the shape of the original pattern.

507. Method of Making Patterns. — The first step in
making a large or complicated pattern is to provide a full-
sized working drawing for the mechanic. Next comes the
selection of the proper wood, which should be of the best
grade, close-grained and well seasoned, so as to stand hard
usage in the foundry. After the wood is selected it is run
through a planer, then cut to size and shape by a hand-, cross-
cut-, or rip-saw. If necessary, the lathe is used for turning up
the necessary parts. After being cut to approximate shape
and size, the different parts are assembled by the use of
brads, screws, and glue. The hand-tools now come into
use, and the model is made to the exact size and shape desired.
It is then sandpapered all over to a finished surface, and the
core prints are placed in position. The pattern is next
varnished with gum shellac dissolved in alcohol. One coat
is applied and smoothed off with a piece of partly used sand-
paper, after which two other coats are given to make a hard,

439

440

APPLIED SCIENCE

smooth surface. The surface is sandpapered again, after
which shellac varnish is applied to give a hard, smooth finish
and to fill the pores. This last process helps the pattern to
withstand the action of the damp sand and the hard usage
to which it is subjected in the foundry.

Core boxes, corresponding to the interior of the finished
casting are next made. These boxes must be so constructed
as to facilitate the work of the core-maker. They must
possess a high degree of durability and they must be accurate,
or the casting when finished will not have the proper thick-
ness of metal.

Patterns are usually made from seasoned white pine.
When many castings are to be made in the same mold,
however, mahogany or cherry are preferable. Mahogany,
having a hard, dense surface, is invaluable for small, fragile
patterns or for patterns which are in constant use. Though
more difficult to work than pine, it will stand much more
abuse. Cherry, another durable wood, is cheaper than
mahogany and preferable for some kinds of work.

508. Flasks and Cores. — The box in which the sand is
molded from the pattern is called a flask. It consists of
two or more parts, open at top and bottom. Its purpose is
to hold in position the sand of the mold during the operation
of molding. The lower or bottom part of the flask is called
the drag and the top or upper part the cope (Fig. 206), while
any intermediate parts are termed cheeks. The parts of
the pattern are also known as the drag, cheek, or cope accord-
ing to the portion of the flask in which they were molded.
If a special pattern is to be constantly used in manufacturing
a certain line, it is well to make both the flask and the pattern
of metal for the sake of wear and durability.

PATTERNS, CORES, FLASKS, AND MOLDS 441

A core ie the baked sand part of the mold and is made in
a separate device termed a core-box. The baked sand is
usually somewhat coarser than that of the mold, and con-
tains clay, flour, oil, sour

beer, or some other bind- l

ing materials to prevent I

it from falling apart when
baked dry. A core-print
is that part of the pattern
designed to make an im-
pression in the sand in Fiu.206.— Copeand Dragof sPattem.
which the core is held.

A Bprue is an opening in the cope, through which the metal
is poured. A gate is a channel cut from the sprue to the
impression of the pattern in the mold.

609. Constructions of Patterns. — Patterns may be built
up in two ways: (1) in a solid mass, as in the case of a small
cylinder pattern; and (2) in the form of segments, as in the
case of the rim of a pulley. All excepting very small patterns
are built up of several pieces of wood, even if it is possible
to find material large enough to make them in one piece,
because the shrinkage and checking of large timbers would
render the work valueless. Const rucl ing the pattern with
small pieces of wood not only prevents w;irping and checking,
but also makes a much stronger article, provided the gluing
of the pieces is well done. This method of construction also
allows the rim to work more easily, localise the direction
of working is always with the grain, and not partly on end
grain as would be the ease with a solid ].ieie of wood.

In building up in segments, all pieces must be sawed with
the grain of wood and never across the grain, as cross-grain

442

APPLIED SCIENCE

sawing weakens the pattern. The joints of the different
layers or courses of segments should be so arranged that the
segments of one course will tie together those of the course
immediately below it.

510. Arrangements of Parts. — In building up patterns,
the wood should be so arranged that its tendency to warp is
opposed in the different layers. This prevents the whole
mass from warping in one direction. Also it is not wise to
arrange one layer with the grain running across the grain of
the other layers, as is done in cabinet-making. A pattern
is used roughly and is exposed to the dampness of the mold-
ing sand. If two layers have the grain running lengthwise
and one layer crosswise, the two layers will swell in one
direction and the one in another at right angles to it. This
swelling practically ruins the pattern for the molder, as
the outside layers project beyond the middle layer on each
side, while the middle layer projects at each end. Not only
is the pattern distorted, but in many cases the drawing of
the casting is made impossible.

511. The Pouring of Metal into Mold. — All molten
metal when solidifying forms into crystals in lines at right
angles to the surface from which the heat is given off. This
tendency has no ill effect on a square, round, or flat surface
or object, but when a projection or corner is formed on some
casting it may lead to serious defects, especially if the corner
be particularly square or sharp. To prevent this defect,
it is customary to use round corners, called "fillets. " These
" fillets " may be of wood, leather, or wax. Sometimes they
are worked solid out of the material of the pattern, and at
other times they are glued or melted in, The "fillet" also

PATTERNS, CORES, FLASKS, AND MOLDS 443

prevents a weak corner which might occur because of the
shrinkage of the metal. In many cases this weakness does
not show on the outside, thus deceiving the founder and
rendering the machine, of which the casting is to be a part,
liable to break under strain.

512. Other Terms and Processes. — An opening from the
casting through the cope to the outside air is called a riser.
It is designed to carry the slag (which would otherwise form
part of the casting) into the iron forming in the riser. The
riser also serves as an escape for gas.

A feeder-head is an opening, somewhat larger than a riser,
used on large castings to feed fresh iron into the mold dur-
ing shrinkage. AH sprues, gates, risers, and feeder-heads,
which do not form parts of the casting proper but are merely
aids in getting a sound and smooth casting, are broken away
and remelted.

Venting a mold is the process of providing an escape
for the gas formed by the mixture of the molten metal with
the air in the mold. A vent wire about Y% in. thick is usu-
ally driven through the sand of the cope to within 3^ in. of
the pattern. It should never be driven entirely up to the*
opening, as it will then prevent the escape of gas.

A chaplet is a metal device used to support a core where
a print is not possible. Chaplets are of two kinds — stud
and steeple. The stud chaplet is formed with two heads,
the steeple has much the form of a wire nail. As the chap-
let becomes a part of the casting, great care must be exercised
to prevent rust from forming before the metal is poured.
Rust causes the metal to be agitated during the time
it is hardening or becoming set, and spongy or weak
places in the casting result. Rusting may be prevented

444

APPLIED SCIENCE

by coating the chaplet with a clay wash or by leaving it
tinned.

513. The Drawing of Patterns and Castings. — Since
patterns are entirely enclosed in sand, provisions must be
made for drawing them out. This process involves drafting
or tapering. Draw or draft is the amount of taper or bevel
given to the sides of projections and edges of patterns em-
bedded in the sand, so that when the pattern is drawn, after
the process of molding, the sand will not be broken above
the edges. Should the edges be broken it would be necessary
for the molder to "patch" the mold. Patching is unde-
sirable, not only because of the time consumed, but because
of the liability of leaving a weak place in the mold. The
draw may be from y$ in. to 1 in. per foot of length and is
usually indicated as }/g in., \i in., Y% in., 1 in., etc., draw,
the fact that this draw refers to one foot of length being
understood.

As much draw as possible, considering the machining of
the casting, should be used, for the greater the draw, the more
readily the pattern can be molded. Since a molder may
"make many impressions or molds each day from a single
pattern, the amount of draw should be carefully considered
in designing it.

While the draw on the pattern may, and does, vary, that
on the core-prints is constant. Although no universal draw
has been formulated, it is the custom in each shop to have
a constant draw, so that the cores made and pointed in
core machines may always fit the impression of the core-print.

A safe rule for tapering core-prints is to give the drag-
print a draw of Y% in. for each inch of length, and the core
print % in. draw for each inch of length.

PATTERNS, CORES, FLASKS, AND MOLDS 445

514. Difficulties in Pattern-Making. — For the same
reason that it is necessary to have a constant draw, making
it possible to transfer prints from one pattern to another,
it is necessary that the dowels by which the prints are attached
to the patterns should be of constant diameter, usually A
or 3^ in. It is often possible to make one pattern serve
for many castings by this method. For example, certain
diameters may be desired with different diameters of holes
for the shaft. While the diameter and width of the face
are constant, the different diameters of the holes in the hub
for the shaft may be obtained by simply changing the core-
prints to those of the required diameter.

For convenience in molding, as well as from necessity,
many patterns are made of two or more parts doweled to-
gether, so that the parts may be retained in their positions
during the process of molding. Very often these joints
are made where different parts of the mold separate to with-
draw the pattern, and are called the "parting lines."

Owing to the difficulty of drawing some patterns from the
sand, it is sometimes necessary to draw them in sections.
To do this, one or more parts are attached to the pattern by
wire pins from the outside, so that the pin may be withdrawn
after the parts are supported in place by the sand. Such
parts arc termed "loose pieces."

Questions

1. What is pattern-making?

2. Is it a wood-working or metal-working trade?

3. Explain the steps in making a pattern.

4. Why is a pattern varnished with gum shellac cut with alcohol?

5. What are core-boxes?

6. Of what wood are patterns usually made?

446

APPLIED SCIENCE

7. When are mahogany and cherry used?

8. What is a flask?

9. What is the lower part called?

10. What is the upper part called?

11. What is the drag, cheek, or cope part of a pattern?

12. When is a metal flask and pattern used?

13. What is the core?

14. What is a core-box?

15. What is molding sand? Name the different kinds. Why
are they used?

16. What is a core-print?

17. What is a gate?

18. Why are patterns built up of pieces of wood rather than
one piece?

19. Name the two methods of building
advantages of each method.

20. What is a fillet? Why is it used?

21. Why are some patterns made in sections?

22. How are patterns taken from the mold?

23. What is a riser? Why are they used?

24. What is a feeder-head?

25. What is meant by venting a mold?

26. What is a chaplet? Why is it used?

patterns. State

INDEX

Acceleration, gravity, 56
Acids, 135

importance of, 136

mineral, 137

nature of, 136

nomenclature, 140

organic, 137
Action, chemical, 131
Adhesion, 3
Air,

dry, absorbs moisture, 110

moisture contained by, 91

pneumatic tools, 94

properties of, 90

pumps, 93

use in sand blast, 96
Alkalies, 135, 136

formation of, 139

nomenclature, 140
Ammeter, 179
Ampere, 172
Analysis, chemical, 129
Aneroid barometer, 90
Arc lamp, 117
Area, rules for finding, 18
Armature, 192, 193
Ash, 394, 409
Atomic weight, 128

Bacteria, chemical, 149
Bacteriology, 1, 2
Ball bearings, 50
Barometer, 88-90

aneroid, 90

history of, 89

kinds of, 89

principle of, 88
Bases, 135 (See also "Alkalies")
Basswood, 408
Beauine* hydrometer, 83
Beech, 394, 408

Belting,

canvas, 285

fastening, 286

leather, 285

measure of coiled, 287

sag of, 286
Bichromate cell, 175
Birch, 394, 408
Bleaching, 161
Block and tackle, 35
Blue-print, 231
Boilers, 302-327

care of, 320

chimneys, 322

clearing, 319

construction of, 305

fire-tube, 303

firing, 321

joints, 306

of steam engines, 302

principal parts of, 310

pumps, 314-316

repairing, 310

return tubular, 303

safety valves, 311

terms used in calculations, 325

testing for defects, 309

thickness of plate, 307

water gauge, 313

water-heater, 318

water-tube, 304
Boiling point, 106
Bolts, 252-258
Boring machine, 435
Botany, 1, 2
Boyle's Law, 93
Brace and bit, 426
Brakes, 365
Bricks, 160
Brittleness, 3
B. T. U., 103
Buoyancy,

law of, 78

stability of ship, 79
Burnishing, 277

447

C Compound dynamo, 195
Compounds, chemical, 126

Calipers, 10 classes of, 135

Cams, 59 acids, 135

listening, 217 bases or alkalies, 135

Carbon, salts, 135

compounds of, 158 water, 135

INDEX

449

Dynamo, 190
action of, 193
alternating, 195
care of, 196

compound machine, 195
direct, 195

direct connected machine, 195
efficiency of, 200
principle of, 190
series machine, 194
shunt machine, 194
types of, 194-196

Earth, composition of, 150-152

Earthenware, 160

Ebony, 394

Ebullition, 143

Ejector, 3 17

Elasticity, 3, 167-224

Electrical energy, transmission of,

204-212
Electric cells,

arranged in parallel, 178

arranged in series, 177

battery, 174-178

bichromate, 175

Daniell, 175

dry, 175

gravity, 175

Leclanch6, 174

voltaic, 174
Electricity,

and magnetism, 167-183

electrical apparatus, 205

frictional, 184-189
loss due to, 185

generated chemically, 171

generated commercially, 190-
203

injuries possible in working
with, 211

inside wiring, 205

nature of, 168

outside wiring, 205

practical uses of, 204

requirement of trade, 206

size of wire, 210

static, 184-189
Electric motor, 197-200

kinds of, 198

railway, 199
Electric power, 173y
Electric transformers, 201
Electrolysis, 171
Electrolyte, 172
Electro-magnetic force, 170
Elements, chemical, 127

metallic, 127

non-metallic, 127
Elm, 409
Emery,

cloth, 270

wheels, 279
E. M. F., 172
Energy, 24

accumulated. 65

kinds of, 63

kinetic, 63

potential, 63

springs as source of, 64
Engines,

gas, 359-368

steam, 328-341
Erasers, 228

Evaporation, 110, 143, 144
Expansion,

heat and, 99-112

of metals, 107

of various substances, 108

Fahrenheit thermometer, 102
Fastening agents, 249-261

bolts, 252-258

nails, 249

screws, 249-251
Files, 266-270

kinds of, 266

methods of using, 269

shape of, 268
' teeth of, 267
Filling, 378
Filtration, 143, 145
Fir,

balsam, 410

Douglas, 406

white, 409
Fire extinguisher, chemical, 165
Fire, starting a, 342
Flame, 158
Flange-couplings, 285

■c

450

INDEX

Flasks, 439^446
Flexure, 234 235
Flues, 322
Foot-pound, 24
Force, 23

bending, 237 .

centrifugal, 59-61

centripetal, 60

effects of load of, on body, 233

electro-magnetic, 170

parallelogram of, 62
Friction,

ball bearings, 50

effect of, 49

measurement of, 50
Frictional electricity (See "Elec-
tricity, frictional ")
Fuse, 201

Galvanometer, 178

used in measuring heat, 182
Gas,

engines, 359-368 (See also "Gas
engines")

for heating, 347

lighting, 118

manufactured, 118

natural, 118
Gas engines, 359-368

operation of, 361

principles of, 359

types of, 360
Gases,

air, properties of, 90

barometer, 88

Boyle's Law, 93

expansion of, 87

noxious, 356

properties of, 86-98

use in industry, 86
Gassing, 164
Gauges,

marking, 429

water, 313
Gear-box, 366
Gears, 291-300

direction of, 296

object of, 291

parts identified, 297-299

principle of, 291-293

ratio of, 296

ratio of measurements, 299

relation of speed to diameter,
295

teeth of, 294

terms defined, 297-299

typ«s of, 293
Generation of steam (See"Steam M )
Geology, 1, 2
Glass, 159
Gouges, 428
Governor, 330, 365
Gravitation, 55
Gravity,

acceleration of, 56

cell, 175

specific, 80
Graining, 379
Grinding stones, 278-281

artificial development of, 280

corundum wheels, 279

development of, 278

emery wheels, 279
Grindstones, used for wood-work-
ing tools, 425
Gunpowder, 159

Hammers, 262
Hand-tools, 262-282
chisels, 263-266
drills, 27 1-274
files, 266-270
hammers, 262
scrapers, 270
wood- working, 417-431

brace and bit, 426

care of, 425

chisels, 423, 428

gauges, 429

knife, 424

plane, 427

saws, 417-423

squares, 429
Heart-wood, 390
Heat, 99-1 12
boiling point, 106
B. T. U., 103
generation of, 99
latent, 104

INDEX

451

Heat — Continued

movement of, 99

specific, 105

thermometers, 100-103

units, 103

used in measuring work, 339

water, 318
Heating,

cause of air circulation, 348

exhaust steam, 345

gas, 347

hot- water, 347

indirect method, 344

low pressure steam, 346

main piping, 350

methods of, 342-353

radiators, 349

steam, 343
Hemlock, 407
Hickory, 394, 410
Horse-power, 325, 335
Hydraulic press, 71

use of, 72
Hydrocarbons, 158
Hydrogen, 132
Hydrometer, 82, 91

Beaume\ 83

Twaddell,83
Hygiene, 1, 2

Ice, manufacture of, 92-93
Illuminants, composition of, 114
Incandescent lamps, 1 16
Inclined plane, 24, 41-43

example of, 42
India ink, 231
Induction, 191
Industrial science, 1
Inertia, 3
Infusibility, 4

table of, 5
Injectors, 314, 317
Intensity of sound, 122

Jack screw, 46
Joints, of boilers, 306
Joules, 209, 339

Kalsomining, 380

Kilowatt, 210

Kilowatt-hour, 210

Knife,
compared with chisel, 425
cutting action of, 424

Larch, 408
Latent heat, 104
Laws of motion, 54-67
Lead pencils, 225-227
Leclanche* cell, 174
Length, unit of, 7
Leverage, 26-34
Levers, 24

compound, 30
problems, 31

first class, 28, 29

mechanical advantage, 26

moment of forces, 27

principle of, 26

second class, 29

shapes of, 32

third class, 30
Ley den jar, 184
Light, 113-120

and color, 119

arc lamp, 117

characteristics of, 1 13

Drummond, 117

gas, 118

importance of proper, 115

incandescent lamps, 116

Nernst lamp, 117

reflected, 113

refracted, 114

standard of, 115
Lightning, 186-189

cause of thunder, 188

danger from, 187

forms of, 187

rod, 188
Line of direction, 56
Linseed oil, 370
Liquids,

capacity of pipes, 73

hydraulic press, 71
use of, 72

452

INDEX

Liquids — Continued
mechanics of, 68-85
pressure, 69-70
properties of, 68
use in industry, 68
Lubricants,
greases, 152
object of, 152
•oils, 152

requirements of good, 154
solid, 153
Lumber, 396-411

cause of rottenness in, 415
classification of sources of, 404-

410
cutting boards, 400
cutting planks, 400
defects of, 412-416

case hardening, 414

checks, 414

knots, 412

warping, 414
effect of seasoning on strength,

416
felling timber, 398
figure, 399

forest trees make good, 396
grain, 399

methods of sawing, 399
seasoning of, 400-404

kiln-drying, 402-404

natural method, 401
shade trees, make poor, 396
source of commercial, 397
two types of trees, 396

Machines,
and tools, 22
centrifugal, 60
mechanical principles of, 22-

25
power,

measurement of, 47
wood-working, 432-438 (See
also " Wood- working ma-
chines")
why used, 22
Magnetic field, 190
Magnetism,

and electricity, 167-183

magnetic field, 167

nature of, 167
Magnets, shape of, 167
Mahogany, 394
Malleability, 4

table of, 5
Manufactured gas, 11&
Maple, 393, 405
Mariner's compass, 168
Mass, 10
Materials,

strength of, 233-248 (See also
''Strength of materials")
Matter,

indestructibility of, 5

properties of , 1-6

three states of, 86
Measure, 7-21

coiled belting, 287

electrical units of, 172

of distance, 8

of electric power, 173

of screw thread, 253

of stresses, 237

precision of, 17

table of, 12

units of, 7
Mechanical advantage, 26

cost of, 49
Mechanical drawing supplies, 225-
232

blue-print paper, 231

drawing paper, 227

erasers, 228

India ink, 231

lead pencils, 225-227

perspective drawing, 230

required, 225

tracing cloth, 230, 231

working drawing, 229
Mechanical principles, 24

of machines, 22-25
Mechanics of liquids, 68-85
Mercerizing, 164
Metals, weight per cu. in., 241
Metric system, 13-16
Mixtures, chemical, 126
Molding machine, 435
Molds, 439-446
Molecular weight, 130
Moment of forces, 27
Momentum, 55

INDEX

453

Morse, Samuel, 220, 222

alphabet, 223

numerals, 223

punctuation, 223
Mortar, 160
Mo tising machine, 435
Motion,

kinds of, 58

laws of, 54-67

three laws of, 54
Motor car, parts of? 362
Motor electric (See "Electric

motor")

Nails, 249
Natural gas, 118
Nernst lamp, 117
Neutralizes electric, 185

Oak, 393, 406
Ocher, 378
Ohm, 172
Ohm's Law, 173
Oil, linseed, 370
Osmosis, 392
Oxidation, 133
Oxygen, 133
Ozone, 133

Painting,

gold-leaf work, 382

graining, 379

hygiene of trade, 383-387
dangerous pigments, 383
poisonous vehicles, 386
safeguards against poisoning,
384-386

kalsomining, 380

object of, 369

operations of, 369

preparation for, 369

sign, 381
Paints, 369-389

bases, 370, 374

composition of, 370

colors, 37$

driers, 371

linseed oil, chief vehicle, 370

pigments, 376

red lead, 377

resins, 372

thinners, 371
turpentine, 372

vehicles, 370

white lead bases, 374

white lead process, 374

zinc bases, 377
Parallelogram of forces, 62
Patterns, 439-446

arrangement of parts, 442

chaplet, 443

construction of, 441

cope, 440

difficulties in making, 445

drag, 440

drawing of, 444

feeder-head, 443

flasks and cores, 440

method of making, 436

pouring metal into mold, 442

riser, 443

use of, 436

venting a mold, 443
Pear wood, 394
Pelton wheel, 76
Perspective drawing, 230
Perspiration, 356
Physico-chemical processes, 143-

155
Physics, 1
Pine, 393

white, 407

yellow, 404
Pipes,

capacity of, 73

for heating systems, 350

risers and returns, 351

steam engines, 333-335, 336,
337
Pitch, 122
Planes,

description of, 427

kinds of, 428
Plumb bob, mercury, 56
Pneumatic tools, 94
Polishing, 277
Poplar, 408
Porcelain, 160

454

INDEX

Porosity, 4
Power, 24

electric, measured, 173
horse-, 335
saws, 432
transmission of, 283-301

methods of, 283
weights as source of, 65
wood-working machines, 432-
438 (See also " Wood- working
machines")
Precipitation, 143, 144
Pressure, steam, 105
Printing on fabric, 162
Prony brake, 47
Properties of matter, 1-6
Pulleys, 24, 35-38, 288-291
compared with wheel and axle,

39
series of, 36
simple form, 35
size of, 290
speed of, 289
split iron, 288, 289 .
wood split, 288, 289
Pumps,
boiler, 314
measurement of capacity, 315
measurement of pressure, 315
measurement of water cyl-
inder contents, 316
Pyrometer, electric, 180-182

Radiation, 349

measurement of heat, 350
Radiators, 349
Reaming, 274-276

kinds of reamers, 275

operation of, 274
Red gum tree, 405
Red lead, 377
Redwood, 405
Resins, 372
Resistance box, 200
Rheostat, 200
Rivets, 260
Rope drives, 287
Rosewood, 393
Rule,

folding, 9

machinists', 9

Safety,

factors of, 243

valve, 311

construction of, 312
Salts, 135

formation of, 137

nomenclature, 140
Sand, 159

blast, 96
Sandpapering machine, 435
Sap, 391
Sap-wood, 390
Saws,

carpenter's principal tool, 417

cross-cut, 417
action of, 421

guards for, 436

how to handle, 422

operation of, 420

rip, 417
action of, 420

setting, 419
Scrapers, 270
Screws, 25 t 45-47, 249-251

jack, 46

principle of, 45
Screw threads,

depth of, 255

kinds of, 255

measurement of, 253

parts of, 252

standard, 256-258
Series dynamo, 194
Shafting,

arrangement of, 283

bending and twisting, 285

formula for H. P., 284

setting line, 284
Shaper, 435
Shearing, 234, 235
Shunt dynamo, 194
Silencer, 364
Siphon, 96
Sizing, 163
Smoke, 323
Solution, 143
Sound, 122-123, 124

intensity of, 122

pitch of, 122

quality of, 122

INDEX

455

Spark-plug, 365

Specific gravity, 80 ..

Specific heat, 105

Spectrum, 119

Speed, 11

Spontaneous combustion, 164

Springs, 64

Spruce, 407

Squares, 429

Staining, 378

Starting box, 200

Starting handle, 363

Steam,

amount produced by specific
amount of water, 352

characteristics of, 302

exhaust heating, 345

generation of, 302, 327

heating, 343

low-pressure heating, 346

source of, 302

temperatures of, 324

valves, 351
Steam engine, 32&-341

alignment of pipes, 334

boiler of, 302

condensing, 333

corrosion of pipes, 336

crank, 331

governor, 330

history of, 328

installation of pipes, 333

piping material, 337

principal parts of, 329
Steam pressure, 105
Storage batteries, 176
Strains, effect of, 235
Strength of materials, 233-248

chains, 244

effect of seasoning on wood, 416

effects of load of force on bodv,
233

factors of safety, 243

need of knowledge of, 233

table of, 241

testing laws concerning, 239-241
Stresses,

kinds of, 234

measurement of, 237

of compression, 239

of elongation, 238
Sublimation, 143, 148

Sugar pine, 410
Switchboards,

power house, 206

telephone, 214
Synthesis, chemical, 130

Table of,

apothecaries' weight, 13

atomic weights, 129

avoirdupois weight, 12

circular measure, 12

colored lenses, 121

cubic measure, 12

dry measure, 13

ductility, 5

expansion of metals, 108

factors of safety, 244

general measure, 13

infusibility, 5

land measure, 12

linear expansion of solids, 109

liquid measure, 13

long measure, 12

malleability, 5

metric equivalents, 15

metric measurements, 14-16

quantities, 13

square measure, 12

strength of materials, 241

tenacity, 5

time measure, 13

troy weight, 12

weight and sp. gr. of liquids, 81

weight and sp. gr. of metals, 80

weight of metals per cu. in., 243
Tape, steel, 9
Taps, 258-260

determining size of, 259

teeth of, 259
Telegraph, 220-223

history of, 220

Morse code, 223

operation of, 221

parts of, 220
Telephone, 213-219

cables, 217

construction work, 219

distributing frames, 217

history of, 213

listening cam, 217

456

INDEX

Telephone — Continued

making a connection, 214-217

principles of, 213

supervising lamps, 217
Tenacity, 3'

table of, 5
Tenon machine, 435
Tension, 234, 235
Thermometers, 100-103

Fahrenheit and Centigrade,
102

manufacture of , 100

temperatures in industry, 101
Thread (See "Screw thread")
Thunder, 188
Time, unit of, 7
Tools, 22
Torsion, 234, 235
Toughness, 3
Tracing cloth, 230
Tracing paper, 231
Transformers, electric, 201
Transmission of power, 283-301
Trees, 390-395

annual rings, 392

characteristics of, 390

heart- wood of, 390

sap, 391

sap-wood of, 390

size of, 393

structure and growth, 391
Tuberculosis, 357
Tupelo, 410
Turbine,

steam, 338
action of, 338

water, 75
Turning lathe, 434
Turpentine, 372
Twaddell hydrometer, 83

Vacuum pan, 106
Valence, 131
Valves,

air, 351

of motor car, 363

safety, 311

construction of, 312

steam, 332, 351

Varnishes, 369-389

application of, 379

composition of, 373
Ventilation, 354-358

dust, 357

exhaust, 355

forced, 355

methods of, 354

noxious gases, 356

object of, 354

perspiration, 356

tuberculosis, relation to, 357

waste products, 356
Volt, 172
Voltaic cell, 174
Voltmeter, 179
Volume,

rules for finding, 18

unit of, 8

Walnut, 393, 410
Water,

gauge, 313

hard, 135

heater, 318

measurement of flowing, 77

needed to produce 1 cu. ft. of
steam, 352

power wasted, 76

pressure, 69

properties of , 135

soft, 136

storage of, 73

typical liquid, 68

weight of cu. ft. of, 69
Water wheels,

overshot, 74, 75

Pelton wheel, 79

turbine, 75

undershot, 75
Watt, 173

Watt, James, 24, 328
Wedge, 24, 44-45

application of principle of , 44
Weights, 7-21

atomic, 128

defined, 10

law of combined, 131

metals per cu. in., 242

INDEX

457

Weights — Continued

molecular, 130

relation to mass, 10

source of power, 65

table of, 12

unit of, 8
Wheel and axle, 24, 38-41

compared with pulley, 39
White lead process, 374
Wire, electric, 210
Wood,

defects of, 412-416 (See also
"Lumber, defects of")

uses in industry, 390

varieties of, 393
Wood-planer, 433
Wood-working machines, -£$2-438

boring machine, 435

jointer, 433

jointer guards, 437

kinds of, 432

molding machine, 435

mortising machine, 435

power saws, 432

prevention of accidents, 435-
438

sandpapering machine, 435

saw-guards, 436

shaper, 435

tenon machine, 435

turning lathe, 433

wood-planer, 433
Work, 23

measurement of, in heat units,
339
Working drawing, 229
Working edge, 417
Working face, 417

■H

v«"

YB 16027

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