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MENTARY LESSONS

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PREFACE.

HE lack of literature relating to the physics of ag-

riculture in any form available for class instruction
has led to the preparation of these lessons to meet the
immediate needs of our Short Course students. They
are intended simply as a temporary expedient to be
used until time shall permit the preparation of a suit-
able text-book on the Physics of Agriculture.

The Articles on Farm Drainage and The Construc-
“tion and Ventilation of Farm Buildings were prepared
for other purposes, but are here appended to make

them available for reference.

MapiIson, WIS.

CONTENTS.

Page.
INTRODUCTION, - - - - - - - 3
ELEMENTS OF MACHINES, - - - - E 16
STRENGTH OF MATERIALS, - ~~ - - : : Lee
FLUIDS, - - - - : - . - 46
HEAT, - - - - - . - - eh eae
PROTECTION AGAINST LIGHTNING, - - - - 79
Sort PHysics, - : - - - - - 84
TILLAGE, - - - - - - - - 116
IMPLEMENTS OF TILLAGE, - = ~ 2 : = sale
Farm DRAINAGE, - - - - - - - 142
CONSTRUCTION AND VENTILATION OF FARM BUILDINGS, - - 157
TABLE OF RELATIVE HUMIDITIES, - - - - 178

INDEX, - - - - - - - - 180

INTRODUCTORY.

1. Physical and Chemical Changes.— When trees are
cut into stove wood or cut into dust with the saw, the
pieces which remain are wood still and such changes are
physical; but when the wood is placed in the stove and
burned changes take place which destroy the wood, as such,
and these are chemical changes. When a lump of sugar is
dissolved in water tho sugar is sugar still and may be re-
covered as such by evaporating the water, and the change
is a physical one; but when yeast and “mother of vinegar”
are added to the sweetened water and allowed to stand the
sugar is transformed, alcohol and then vinegar appear
in its stead, and the changes are chemical ones. The fall
of rain and snow to the ground, the flowing of streams to
the sea and the evaporation and return of the water to the
land again are all physical changes. The operations of
tillage, of drainage, the cutting and handling of farm prod-
uce and the making of butter are physical processes. The
running of farm machinery and the construction of farm
buildings involve the application of physical rather than
chemical laws.

Write a list of five physical and five chemical changes.

2. Matter and Foree.— The physical universe, so far
as we are able to comprehend it at present, appears to be
made up of two classes of agencies, one of which is active
and called force, while the other is passive, or acted upon,
and named matter. Water is matter, and gravity is the
unseen force or agency which causes it to flow to the sea
or to turn the water wheel; air is matter, but gravity is
the force which moves it in the wind when it drives the
ship or turns the wind-mill. Wood and oxygen are mat-
ter, but chemical affinity is the force which drives their
molecules into collision producing the intense heat and
light of the fire. |

3. Kinds of Matter.— Chemistry at present distin-
guishes about seventy kinds of matter which are known
as elements or elementary substances; oxygen, hydrogen,

4

nitrogen, carbon, iron, sulphur and phosphorus are seven
of these. Water is not one of the elements, for it can be
decomposed and shown to consist of oxygen and hydrogen. —
Sugar is not an element, but is made up of carbon, oxygen
and hydrogen. }

4. Constitution of Matter.—Each and every body or
mass of elementary substance, is composed of large num-
bers of minute units or individuals named atoms, which
various lines of experiment, observation and reasoning
show to be constant in weight and properties, so far as
we know them; and it is in consequence of this constancy
of weight and properties that chemistry is able to analyze
the various substances and tell us their composition,

The atoms of which all bodies are composed rarely exist
alone; they are bound into tiny clusters called molecules.
Some of these molecules are made up of two atoms, like those
of common salt containing one of chlorine and one of so-
dium; other molecules contain three atoms, like those of
water, two of hydrogen and one of oxygen; molecules of cane
sugar contain forty-five atoms, twelve of carbon, twenty-
two of hydrogen and eleven of oxygen. Commercial ana-
line violet possesses molecules of fifty-seven atoms of five
different kinds, and there are other atom clusters or mole-
cules more complex than these.

5. The Size of Molecules.—The size of molecules is
almost inconceivably minute. Sir William Thompson com-
putes the number of molecules in a cubic inch of any per-
fect gas having a temperature of 32° F. and under a pres-
sure of thirty inches of mercury, to be 10” or ten sextill-
ions.

We have many strong proofs of the extremely minute
size of molecules. If a grain of strychnine be dissolved in
one million grains of water, and if we place one grain of
the water containing the strychnine in the mouth, its bit-
ter taste is recognizable, and yet the volume of a grain of
strychnine is only about 355 of a cubic inch. <A cubic inch
of analine violet will impart its purple color to more than
eight million three hundred and eighty-four thousand cubic
feet of water. Nobert succeeded in engraving parallel
lines on glass at the rate of more then one hundred thou-
sand to the inch, and hence the point of his diamond must
have been much thinner than this, and the diameters of
the molecules which composed it smaller still.

By)

The fact that musk and other perfumes keep the air of
large apartments so charged with their molecules that we
are able to detect them in spite of the fact that the air is
constantly changing and the loss in weight of the per-
fume is extremely small indeed, is still another striking
proof of the minuteness of molecules, and, at the same
time, of our ability to recognize them.

6. Properties of Molecules. — Molecules possess mag-
nitude and weight and are divisible into atoms. When-
ever a chemical change takes place existing molecules are
transformed into new ones of a different kind and chem-
istry, as a science, deals with these changes, while physics
deals with the molecules and groups of them.

* Structure of Bodies. — The bodies or masses of
matter with which we are familiar are always composed of
molecules but these molecules are believed to be not in
contact with one another.

If a quantity of salt be placed in a vessel and then water
added so that the combined volume before solution fills the
vessel, when the salt dissolves the volume will be found to
be less.

The fact that bodies change their volume with changes of
pressure and of temperature also indicates that the mole-
cules which compose them are not in contact.

The mercury in a thermometer, for example, fills the bulb
at 212° F. and a certain portion of the stem also, but as the
temperature falls the mercury in the stem withdraws into
the bulb and yet the capacity of the bulb diminishes by
contraction at the same time, and this could not take place
were there not room in the bulb not occupied by the mole-
cules of mercury.

8. Molecules of Bodies Not at Rest.— Not only are
the molecules which constitute the various bodies around us
not in contact with one another, but a large number of facts
and observations indicate that they are not relatively at
rest. If a solution of sugar or salt be placed in the bot-
tom of a vessel and covered with water the molecules of
sugar and salt travel upward and those of the water down-
ward until, finally, a uniform mixture of the two liquids
has resulted. The same fact is also observed where two
gases are brought su contact — diffusion takes place. So,
if a solid lump of sugar or of salt be placed in water, the

6

molecules travel away and disperse themselves through the
whole mass. The molecules of fragrance from fruits and
flowers are constantly traveling away from their respect-
ive places of origin. Molecules of camphor leave the solid
lump and travel through the surrounding air, and snow
disappears into the atmosphere without melting on the
coldest of winter days.

The pressure which steam exerts upon the: head of the
piston when driving the engine is regarded as due to the
collision of the molecules against its face; and the pressure
exerted by all gases is explained in the same way. The
temperature of bodies is also an expression of the degree
of molecular agitation within them. When we place the
fingers upon a warm body the motion of its molecules is
communicated to the molecules of the cuticle, and this in
turn to the nerve endings, and onward through the nerves
to the nerve centers in the brain, giving rise to the sen-
sations denominated hot, warm, cool or cold.

The mean distance traveled without collision by a mole-
cule of hydrogen at ordinary temperature and pressure is
computed by Crooks at zoooo MM., OF z5xo00 In., while the
velocity is at the rate of about six thousand feet per sec-
ond. The heavier the molecules are the slower they move,
the rates being inversely as the square roots of their
weights. Thus the oxygen molecule, being sixteen times
as heavy as the hydrogen molecule, moves under like con-
ditions, only one-fourth as rapidly.

If it is difficult to think of a body like a horse-shoe or a
hammer maintaining its form when its molecules are
neither in contact nor relatively at rest, it may be helpful
to turn to the solar system, consisting of the sun, planets,
satellites and asteroids, together with comets and meteors,
all of which are in constant and rapid motion, separated
by immense distances, and yet as a whole constituting one
great body, maintaining a definite form and size as it
travels through space.

9. Kinds of Foree.—The falling of leaves, of rain-drops
and of unsupported bodies generally, is a constant re-
minder of an influence which the earth, as a whole, exerts
upon bodies at its surface. The strength and rigidity of -
solids as compared with fluids; the union of two boards
by means of glue; the rise of oil in a lamp-wick, and its

7

destruction by burning, with the appearance of heat and
light, all convince us of influences of some sort which the
molecules of bodies exert upon one another.

It has been customary to speak of these influences as due
to the action of different kinds of force, and they have re-
ceived distinctive names.

10. Gravitation is the action which any one molecule
exerts upon every other molecule, tending to draw them to-
gether no matter how great the distance may be between
them. The intensity of this attraction is directly propor-
tional to the mass and inversely proportional to the dis-
tance between the molecules.

The weight of a load of hay or of a bushel of wheat is
the sum of the attractions of every molecule of the earth
upon all the molecules of the load of hay or bushel of
wheat.

11. Molecular Forces.—When molecules are brought
very close to one another, so that the distances between
them become inappreciable, their tendency to come together
or their resistance to separation are spoken of as due to
molecular attraction, and three varieties are designated,
viz., cohesion, adhesion and chemical affinity.

12. Cohesion.—When water is cooled below 32° F. the
rate of molecular motion and the mean distance between
the molecules so diminishes that the force of cohesion be-
gins to bring them into new relations and to bind them
more firmly together, so that a solid body results. The
same force comes strongly into action when melted iron,
copper or other metal changes from a liquid to a solid
state.

When finely ground graphite is subjected to extreme
pressure in moulds, after having been first thoroughly
cleaned, the molecules of the separate fragments are brought
so closely together that they unite into solid cakes, from
which the leads of pencils are sawed. Where molecules of
the same kind are thus bound together the acting force is
named cohesion.

13. Adhesion.—When the smooth, plane surfaces of
two pieces of wood are coated with a paste of glue and
brought firmly together they are held very secur ely when
dry. In this case the action between the molecules of glue
and the molecules of wood on either side serves to make a
single body of the three. The action seems to be essen-

8

tially the same as that of cohesion, but because it occurs
between molecules of different kinds the term «adhesion is
used to designate this distinction. The coating of walls
with whitewash, paint, varnish and the like are other
manifestations of the same force.

14. Chemical Affinity. —When the temperature of
wood is raised to a sufficiently high point in the presence
of air an action occurs between the molecules of wood and
those of the oxygen of the air, which results in the com-
plete breaking down of both sets of molecules and the
formation of new ones of entirely different kinds in their
stead. This sort of molecular action, as in the case of ad-
hesion and cohesion, takes place only across insensible dis-
tances, and the agency which brings it about is named the
force of chemical affinity. The rusting of iron, the heat-
ing of a manure pile or of a silo, the souring of milk and
the processes of digestion are all phenomena in which this
force is operating to form new molecules from old ones.

15. States of Substances.—-It is common to speak of
substances as existing, under different conditions, in a
solid, liquid or gaseous state. A critical study of these
states, however, shows that no absolute distinction exists
between them, and that, by insensible gradations, one
state may shade into another. The substance water we
know as solid ice, liquid water and gaseous steam. Iron
at ordinary temperatures we think of as a solid, but as its
temperature is raised it gradually becomes more and more
soft until it passes by insensible shades into the condition
of a true liquid.

The ideal solid is a body which, if brought under a force
which tends to change its form, responds, if at all, to the
force, and then remains unchanged so long as that condi-
tion of stress may exist. The steel spring, when loaded,
changes its form, and then remains constant until the load
is removed, or rather appears to when rough measurements
only are applied as a test; but if more than a certain load
is applied, the form keeps changing so long as the load acts.

The ideal liquid is the body which constantly changes its
form whenever a force is made to act more intensely upon
one portion of it than upon another. We think of water as
a perfect fluid, and yet a comparatively heavy load may be
placed upon a Grop of water resting upon a dusty surface
without its changing form, except a definite amount at first.

Jv

On the other hand, we think of sealing-wax as a solid, and
yet if a bullet be placed upon it, it will, by its own weight,
gradually sink through it. But jelly, even when rather
soft, will keep its form under the same load which will
sink throvgh the sealing-wax; the sealing-wax conforms to
the law of liquids and the jelly to that of solids.

In the gaseous state the molecules of the substance have

attained so large a range of motion that the molecular at-
tractions appear entirely overcome, and the molecules con-
tinually separate from one another unless some confining
surface or wall prevents them. No vessel can be half filled
with a gas as it can with a solid or a liquid, for the mole-
cuies travel to and fro from side to side or from top to
bottom, thus occupying the whole space, no matter whether
the number of molecules be ten or ten millions.
- 16. Work.— When a force, like that exerted by a horse,
acts upon a quantity of matter and changes its position in
any direction, work is done, and the amount of it is meas-
ured by the product of the force and the space through
which the mass has been moved.

WorkForce x Space.

If a horse exerts an average tension of twenty pounds
through the whippletree upon the carriage and moves it
through ten thousand feet the work done is

20 lbs. x 10,000 =200,000 foot-pounds,

meaning the equivalent of two hundred thousand pounds
lifted one foot in opposition to gravity.

So if the horse exerts a tension of one hundred pounds in
raising a forkful of hay and carries it through a height of
forty feet the work done is

100 Ibs. x 40=4000 ft.-lbs.

Simple pressure is not work. The load must move be-
fore work is done. The man who stands still under a sack
of grain does no work on the load he holds.

The mean rate of doing work is the whole work done di-
vided by the time required to do it, and 550 foot-pounds
per second is called a Horse-power by engineers. This,
however, is more work than the average horse can do, this
being estimated by General Morin at 26,150 foot-pounds
per minute or 455.8 foot-pounds per second.

10

A taborer lifting dirt with a spade has been found able
to do 470 foot-pounds per minute, and on a tread power,
raising his own weight, 4,230 foot-pounds per minute; the
first being .J18 of an animal horse-power and the latter
16 or a little less than one-sixth.

17. Energy. —Energy is the ability of a moving body
to do work. If a twenty-pound weight, suspended by a
cord, be drawn to one side and then allowed to fall, it will
rise on the opposite side of the line of rest to a height
nearly equal to that from which it fell. This height would
exactly equal that from which it falls if the air and the
suspending cord offered no resistance. Here the moving
weight, on reaching its lowest level, has acquired an
amount of energy equal to that which has been’ expended
in raising the weight to the point from which it fell.

When a hammer is brought to rest on the head of a nail
it is the energy of the moving hammer which does the
work of forcing the nail into the wood.

The wind blowing through the wind-mill has its velocity
reduced, and so much of its energy is transformed into
motion of revolution in the wheel. The same is true of
water in flowing through a water-wheel, the water loses
energy by imparting it to the wheel.

When the spring of a clock or watch is wound up its
molecuies are drawn out of positions of rest, as with the
weight referred to, and in falling back to their positions
of rest again their energy is imparted to the train of
wheels to which the spring is attached.

18. Energy and Matter Indestructible.-—No discov-
ery of modern science is more fundamental and far-reach-
ing than that of the indestructibility of both matter and
energy, and equally fundamental is the other fact that
neither of them can be created.

One form of energy can be transformed into another
form and one kind of substance can be decomposed and
others made from the components, but in these transfor-
mations there is never either annihilation or creation,
The few bushels of ashes left from the winter’s supply of
coal or wood seem to point to a destruction of matter, but
their weight added to the weight of the products which
escaped through the chimney is actually greater than that
of the original fuel, for oxygen from the air has united
with it. So when the energy of eight or ten horses is be-

11

ing expended in the threshing of grain it looks as though
energy were being annihilated, but it is simply changed
into heat, sound and energy of position, not lost: We
appear to realize in the waste products of domestic ani-
mals and the increase of their bodies a very much smaller
weight of matter than they have consumed, but this is be-
cause so large a weight passes off in an invisible form
through the skin and lungs. Something is never, so far as
we know, reduced to nothing; neither is something created
from nothing.

19. Machines not Generators of Energy.— When,
through the aid of a machine, a man or a horse is able to
move a load which he could not otherwise handle, the ma-
chine is not a source of energy, it is simply a device which
enables their energy to be transmitted and used more ad-
vantageously; but there is always. some loss in the ma-
chine, no matter what that machine may be. Some energy
is required to overcome the necessary friction of the mov-
ing parts of the machine so that the useful work accom-
plished never quite equals the energy expended.

20. Inertia of Matter.— Newton’s first law of motion
may be stated as follows: Every body tends to persevere in
its state of rest or of uniform motion in a straight line un-
less acted upon by some external force, or briefly, matter has
inertia. There are many unmistakable illustrations of this
law. The sudden starting of a wagon tends to throw a
standing person backward because his feet take on the mo-
tion first and are carried out from under him. In beating
a carpet the carpet is driven forward away from the dust.
In driving a nail the suddenness of the blow forces the
wood aside and in front of the nail before the motion can
spread to the surrounding weod.

When a horse, in rapid motion, suddenly turns a corner,
the rider must lean in the direction of turning until his.
tendency to fall exactly balances his tendency to move on
in a straight line. It is the principle of inertia which
enables the rider to sit securely on the bicycle while it is
in motion; the same principle explains the standing of the
top while in motion, and the constant parallelism of the
earth’s axis during its revolutién about the sun. The
rider on the bicycle is moving rapidly in one direction, and
for him to fall either to the right or the left would require
him to change his direction of motion at a right angle,

12

which is the same thing as trying to turn a corner when
at full speed —a thing practically impossible. 1t is this
law of inertia which makes it possible for the penman to
make his smooth curves only by rapid movements of the
hand.

21. Centrifugal Force.— Centrifugal force, so called,
is another manifestation of the law of inertia. The stone
twirled about the head with a String, because of its tend-
ency to move always in a straight line, exerts a constant
tension upon the string, and if the rate of motion is great
enough the string will be broken.

It is this manifestation of inertia in circular motion
which lies at the foundation of all rotary forms of cream-
separators and extractors and of several forms of fat-tests
for milk.

In the Babcock and Beimling “milk-tests” the rapid
revolution of the bottles which ;
contain the fat to be sepa-

tated irom the liquid:with which: ===
. e . a :

1t is mixed, throws the heavy ===

liquid to the bottom of the bot- B= ===
tles, which reacts upon the fat,

hl

forcing it toward the center of
the circle, where the velocity
is least. The fat, like the heav-
ier liquid, in consequence of its
own inertia, tends to go to the
bottom of the bottles also and
is simply prevented from doing
So by the greater inertia of the Rigi
heavier liquid.

22. The Gravity Method of Creaming.— To under-
stand the reason for the more rapid and perfect separation
of cream by the centrifugal methods over the simple gravity
methods we need to get first the principle of creaming by
gravity. ;

It is this: If a block whose weight is but one-half that
of an equal volume of water be immersed in water it
will be lifted by a force equal to the difference between the
weight of the block and that of an equal volume of water,
as shown in Fig. 1.

Regarding the water of the vessel divided into cubes ex-
actly equal in volume to the bicck of wood, and the block

‘

gil
sal

13

just half as heavy as an equal volume of water, then the
weight of column A equals

24+2+41=5,
while the weight of column B is
24+24+2=6.

Now, as column B exerts a pressure upward on the column
A equal to its own weight, the block in column A must be
pushed upward by a force equal to the difference in the
weight of the two columns, or of

6—5=1.

A comparison of columns B and C will show that it
makes no difference where the block is placed in the liquid,
the force which tends to lift it to the surface is always the
same. If the attraction of the earth were just twice as
strong as it is then the cubes of water and the block in
column A would weigh

4+4+2=10,
and the cubes of water in column B would weigh

4+4+44=12)
and the lifting force on the block would be

12-10=2, *

or just twice what it now is; so if the force of gravity
were made one hundred times what it now is, the lifting
force acting upon the immersed block would be increased
one hundred fold.

23. Centrifugal Creaming.— The centrifugal methods
of creaming are applications of the same principle as the
gravity methods, the only difference being in the substitu-
tion of a stronger force in the place of gravity, and by so
doing of shortening the time and securing a more complete
separation. This is done by transforming the energy of
an engine or of some other form of motion into the energ)
of rapid rotation in the milk, giving rise to a strong out-
ward pressure, which acts exactly as gravity, does in the
old method of creaming.

24. To ‘Compute the Centrifugal Force,— The
strength of centrifugal force in a milk separator may be
computed as follows:

weight of milk x (velocity in feet .
Centrifugal Force= weight of milk x ( y per sec

14
Suppose the mean diameter of thet circie through which
one pound of milk is made to revolve is ten inches, and
that the centrifuge is given seven thousand Fevonutiens per
minute. In this case the

10 x 3.1416x7000
Velocity= 305-4,

1 lb. x (305.4),

then centrifugal foree=—— Soe
BE Pierce

==9650
and this means that the creaming force would be six thou
sand nine hundred and fifty times as great as by the old
gravity method.
25. Strength of the e Prurmoe Force.— Since the
mean specific “oravity of milk fat at 85° to 90° F. is about
.9L and that of milk serum 1.034, ae creaming force must
be the difference between the two specific oravities, as
shown in 22, or

1.034—.91—.194:

that is, if a ball of butter-fat weighing .91 pounds were
placed in milk serum, the lifting force of gravity upon it
would be .124 pounds, but if placed in milk serum in the
centrifuge under the conditions of 24 the creaming force
would be

6950 x .124=861.8 lbs.

This enormous creaming force seems unnecessarilv large,
and so it would be if the fat globules were large enough to
weigh .91 of a pound each, as in the problem assumed, for
then creaming by the gravity method would be practically
instantaneous, whereas, under existing conditions, it re-
quires about twelve hours,

The actual diameter of the average fat globule in milk
is not far from ee of an inch, while a sphere of butter-
fat weighing one pound would have a diameter of about
3.87 inches.

Now as the volumes of spheres are to each other as the
cubes of their diameters, the pound of fat should contain
about seven trillion two hundred and forty-five billion of
fat globules, But the surfaces of spheres are to each other
as the squares of their diameters, and hence the surface of
the pound spbere will contain the surface of the fat glob-

15

ule about three hundred and seventy-four million four
hundred and twenty-two thousand five hundred times; and
this being true, the aggregate surface of the seven trillion
two hundred and forty-five billion fat globules, whose ag-
gregate volume equals that of the pound sphere, must be
. 72450000( 0000
~ 374422500
times the surface of the pound sphere; and when we re-
member that the friction increases with the surface, and
that more force is required for rapid creaming than for
slow, we can see that a much stronger creaming force is
really needed.

26. Storing Energy.—In many forms of machinery
where the work to be done, like that of sawing wood with
a buzz saw, is not a steady draught upon the source of
power, a fly-wheel, or its equivalent, is very useful in al-
lowing the power generator to store energy when work is
not being done and give it out again as needed. The wind-
mill in pumping water, with most pumps, does work only
half the time, and so there is often attached to the pump
an air-chamber which acts like a sprirg in which the mill
stores energy by compressing air which is given out dur-
ing the reverse stroke. A constant stream is thus main-
tained and the pump enabled to be worked with lighter
winds than would otherwise be possible.

In the animal mechanism the walls of the arteries are
elastic and act like springs. They are stretched by the
powerful, quick contractions of the heart, and then, while
the heart is resting, the blood is forced on by the steady
return of the stretched arterial walls, and continuous cur-
rents of blood are thus moving through the tissues of the
body.

27. Momentum,—When a body weighing ten is moving
with a velocity of ten, the quantity of motion is

10 x 10=100,
and this is called its mcmentum. If the mass of the body
is one thousand and its velocity is five, then
1,000 x 5=5,000,
the quantity of motion, or momentum, of that body. So a
body having a mass of five and a velocity of one hundred
has the same momentum as a body weighing ten, having
a velocity of fifty, for
5 x 100=500 and 50 x 10=500.

— 19,350

ELEMENTS OF MACHINES.

28. The Mechanical Powers.—The simple machines
known by the names lever, wheel and axle, inclined plane,
screw, wedge and knee find an explanation of their action in
the fact that they simply transmit motion with an altered
velocity or direction, the quantity remaining always the
same, except as it is diminished more or less by the fric-
tion and weight of the parts of the machine itself.

29, The Lever.—The lever may be any bar sufficiently
rigid to retain its form when forces are applied to it. The
terms used in speaking of the action are the fulcrum, power
arm and weight-arm: these are represented in Fig. 2.

Power AIR W. Arvin
Fulerum

There are three classes of levers, named First, Second
and Third, according to the relative positions of the ful-
crum to the points where the power and weight are ap-
plied; these are represented in Fig. 3.

P F W 374 Claks Fr

pet class ze 2x4 Class
PIGS

The mechanical advantage of the crow-bar, in moving a
heavy object, lies in the fact that it enables the muscles
to generate energy at their usual relatively rapid rate,
and transform it into so slow a velocity in the load to be
moved that a heavy weight is required to balance the
smaller more rapidly acting power. Suppose we have a
crow-bar sixty inches long, and the fulcrum is placed at
two inches from one end when it is being used as a lever
of the first class. In this case, as shown in Fig. 4,

17

both the power and the weight travel on the circumferences
of circles, the power circumference having a radius of fifty-
eight inches, and the weight circumference having a radius
of two inches.

LEE a

Now the circumferences of these two circles have the same
relative lengths as their radii do, and since the lever does
not bend, the weight can have a velocity only % or zs as
great as that of the power, and since the power is ten and
its velocity twenty-nine times that of the weight, its mo-
mentum must be

10x 29 == 290;
and this being true, the weight, in order to just balance
the power, must have mass enough so that, with a velocity
of one the amount of motion shall exactly equal that of the
power, and hence we have

1 x 290 = 290,
as the load which ten will balance on a lever acting as rep-
resented.

When the crow-bar is used as represented in Fig. 5, it
becomes a lever of the second class, with the power-arm
sixty inches long, while the weight arm is still two inches.
In this case a power of thirty pounds will balance a load
_ of nine hundred pounds.

When the power is applied to the lever between the weight
and the fulcrum, as represented in Fig. 6, the case becomes

18

a lever of the third class, and a power of nine hundred be-
comes necessary to move a load of thirty.

The relation of power to weight in the case of any lever
is expressed by the equation below, where P. equals power,
W. equals weight, P. A. equals power-arm and W.
weight-arm :

P. xP aA, SW OW

When any three terms in this equation are known the
fourth may readily be found.

How great a load may be moved by a power of thirty
pounds acting on a lever having a power-arm of twenty
and a weight-arm of three?

Pox Ph We eA
30 x 20 = W. x 3.
600 =3 W.

W.= 200. Ibs.

30. The Two-horse Evener.—This is a lever of the
second class where the whippletree clevis-pin acts as the
fulcrum for each horse, the weight or load being carried
by the center pin. As ordinarily constructed this instru-
ment is designed to divide the work of moving the load
equally between the two horses. This, however, is not
done at all times unless the three holes lie in the same

straight line.

When the holes are bored as shown in Fig. 7 the load is
divided equally only when one horse is not behind the other.

19

The figure shows that when the near horse falls behind
the other the effective length of his lever arm is dimin-
ished more than is that of the off horse, and consequently
he must pull a larger share of the load.

When the hcles are bored in the same straight line the
possibility of this inequality is avoided, as shown in Fig.
8, because the changes in the effective lengths of the lever
arms are always equal no matter which horse falls behind.
This latter form, although the best so far as dividing the
labor evenly between the two horses, is rarely adopted in
practice, owing chiefly to the possibility of more cheaply
constructing the evener the other way.

Where heavy loads are to be moved, like pulling stones
or stumps, or hauling a load out of a rut or out of the mud,
the second type of evener will always allow a matched
team to pull a larger load, because the horse which hap-
pens to be thrown behind, in attempting to start the load,
is placed at a disadvantage and the other horse can only
pull enough to hold his end against the one placed at
a disadvantage. So, too, in doing heavy work, where
one horse is naturally a little freer or stronger than the
other, the tendency is always to throw more than half the
work upon the slower or weaker horse.

31. “Giving One Horse the Advantage.’’—The fre-
quent practice, where the two horses of a team are not
equally strong, of “giving one horse the advantage” is
based upon the principle that the amomut of work done

20)

by each horse is inversely proportional to the length of the
lever arm upon which he works. Suppose it is desired to
so modify an evener that three-eighths of the work will
fall upon one horse and five-eighths upon the other. In
this case the horse which is to do five-eighths of the work
must have his end of the evener shortened until its length
is just three-fifths as long as that of the horse which is to
do three-eighths of the work. If the distance from 1 to 2
in Fig. 8 is forty-eight inches, then in order to require
the near horse to do five-eighths of the work the power-
arm of his lever will be ~

2+ in.=38.4 inches.

;

This is given by substituting the numerical values in
the general equation of the lever.
PSP AS Wee ore,

By substituting, } x P. A. =

hee
Whence, P. A. = nu in. = 38.4 in.
3

This length of 38.4 inches will be secured by setting the
clevis 9.6 in. nearer the center.

How far in must the clevis be set to give the other horse
an advantage of one-eighth? of one-sixteenth? of one-
thirty-second?

Taking the first of these examples one horse must pull
nine-seventeenths and the other eight-seventeenths of the
whole load; in the second case they draw respectively seven-
teen-thirty-thirds and sixteen-thirty-thirds.

70 7
Fig. F P=2
SVP Lesent

32. Platform Scales. — Levers are often used in com-
bination when it is desired to balance a very heavy load
by a small weight, and such combinations are spoken of
as compound levers. The various forms of platform scales
are examples of such combinations. In the case of hay
scales, four thousand to six thousand pounds are balanced
or lifted by a tew pounds.

Phe =pr inciple by which such combinations of levers give

21

these great mechanical advantages will be understood from
Fig 9.

Phat hoes are wulerume, of the-levers I, It Lil av.
and their power-arms are each ten while their weight-arms
are each one, then a power of two pounds at P. will balance
a load of twenty thousand pounds at W. This must be so,
for -two pounds at P. will cause lever IV to exert a pres-
sure of twenty pounds upon the long arm of lever III, the
twenty pounds pressure of lever III] will cause a pressure
of two hundred pounds on lever II; lever Il transmits a
pressure of two thousand pounds to the end of lever I, and
this pressure will sustain a load of twenty thousand pounds
placed at W.

For levers in combination the continued product of the
power and power-arms is equal to the weight into the con-
‘tinued product of the weight-arms.

P.x P. Arms=W. x W. Arms.
or, 2x 10x10 x 10x 10=20,000 x Lx1x1x1.

In the platform scales the platform is supported at its
four corners by bearings which rest upon four levers, the
ends of which are joined by means of a vertical rod to the
short end of the graduated scale beam. The accuracy and
-sensitiveness of such scales depend upon the exactness with
which the lever arms are constructed and the delicacy and
durability of the bearings and fulerums which transmit
the pressure to the levers.

33. The Locomotion of Animals. — Most of the higher
animals which travel by means of appendages to their
bodies propel themselves with a system of levers which are
operated by sets of very powerful muscles.

The mechanism of muscles and their method of contrac-
tion make it possible for them to move through only very
small distances, and hence where considerable movements
are to be executed the results are secured by attaching
them to the short arms of levers. In the forearm, for ex-
ample, the biceps muscle acts upon a lever whose power-
arm is only one-sixth as long as the weight-arm, and
hence when a weight of fifty pounds is held as represented
in Fig. 10 the muscle must exert a tension of three hun-
dred pounds.

The triceps muscle which extends the forearm is a more
powerful one than the biceps, and in order to accomplish

22

its much more rapid movements it works upon a relatively
much shorter lever arm, the relative lengths of the two
arms being about as one to twenty or twenty-four. Now

it is possible for the triceps muscle to exert a force upon
a spring-balance exceeding twenty-four pounds, and hence,
since
Bx POA. == Wx mt,
we have P. x 1 = 24 x 20,
and P. == 480;

which proves that the triceps muscle can exert a tension
of four hundred and eighty pounds. It is this powerful
muscle acting upon the hammer which enables nails to be
so readily driven.

The great tension which some of the muscles of horses
must exert in pulling heavy loads, acting as they do at the
short ends of levers, is almost beyond belief.

23

34. The Wheel and Axle.— With the lever only a
small amount of motion can be communicated to a body at
once, further movements only being possible after revers-
ing its action. The wheel and axle, represented in Fig.
11, enable power to be applied continuously in one direc-
tion to the load or resistance to be overcome.

The relation of power to weight in this element of ma-
chines is expressed by the equation.

Power x Power-Radius = Weight x Weight-Radius,

or, briefly,
Pxx PER Wx Wes,

and by substituting the numerical values given in Wott
we get.
10) x: 10; tx 100:

The relation of power to weight may also be represented
in terms of the diameters or circumferences of the wheel
and axle, thus:

P. x P. R= W. x W. R.
P. x P. Diam.— W. x W. Diam.
Px PS Cir Wee We Cir.

This mechanical power has by far the most extended use
of any in mazhinery.

35. Trains of Wheels and Axles.—Wherever a great
rotary velocity is desired, as in the case of the wood saw,
in the cylinder of a threshing machine, in the fan of a
fanning mill, or in the much higher speed of centrifuges,
several wheels and axles are joined in a train by means of
belts, gears, or friction pulleys; such systems are analo-
gous to compound levers.

The relation of power to weight both in intensity of ac-
tion and in relative velocities is expressed by these equa-
tions:

1. For intensity of action:

Power x Continued product of P. R.= Weight x Continued
product of W. R.
P. x P. Radii = W. x W. Radii.
2. For velocity:
P, x P. Velocity = W. x W. Velocity.

24

36. The Sweep Horse-power.——This machine is an ex-
ample of a train of wheels and axles whereby the slow
walk of the horses is converted into the extremely rapid
rotation of the cylinder of the thresher, feed-cutter or feed-
mill, the sweeps to which the horses are attached consti-
tuting radii of the first wheel in the train. Here the
small amount of work required of the machines at any one
instant makes a high speed of execution desirable.

37. The High Speed of Centrifuges.— This is se-
cured by a combination of wheels and axles connected with
belts. Suppose the diameter of the fly-wheel of the engine
is twenty-four inches and it makes two hundred and
twenty revolutions per minute. If this is belted to a six-
inch axle or pulley on the driving-shaft, then the number
of revolutions made by the wheel on the driving-shaft will
be

990 x 24=880.

If the shaft-pulley connecting with the axle of the inter-
mediate pulley has a diameter of ten inches while the axle
has a diameter of five inches, then the wheel of the inter-
mediate pulley will make

880 x 1.1760.

revolutions, and if the wheel*of the intermediate pulley
has a diameter of twelve inches while the axle of the cen-
trifuge is three inches, then the centrifuge will make

1760 x 42-=7040.
revolutions per minute.

Change the diameter of a wheel or axle so as to give the
centrifuge four thousand revolutions; six thousand revolu-
tions; five thousand revolutions.

38. Exertion of Great Power.— When the exertion
of a great lifting force is required at the expense of speed,
this may be done by reversing the action of a train of
wheels such as is considered in 37. In that case, if the
power were applied at the centrifuge and the work done at
the other end of the series, a load would be lifted very
slowly indeed, but its weight cculd be very great.

39. The Inclined Plane.— This mechanical power is a
rigid surface inclined to the line of the force or resistance
which it is to overcome, and is represented in Fig. 12:

When the power moves parallel with the length or face

25

of the plane, as in A, the relation of power to weight is
given by the equation
: Power x Length of Plane=Weight x Height of Plane,
or 200 x 15=600 x 5.

But when the power moves in a line parallel with the base
of the plane, as in B, then the relation of power to weight
is given by the equation
Power x Length of Base=Weight x Height of Plane,
or 20 x 1040 x 5.

P=308 Base =10

40. The Tread Power.— This method of transferring
energy is a practical application of the inclined plane, and
the amount which can be transmitted by it depends upon
the height of the plane as compared with its length.

If the length of the tread is eight feet and it is given a
slant of one foot in eight feet, then from the equation

P. x Length=W. x Height

we get, with two thousand four hundred pounds as the
weight of two horses,
P. x 8=2400 x1,
whence P.—300 lbs.,

as the intensity of the power exerted, diminished, of course,
by whatever friction there may be.

What would be the power if the slant were made one foot
in seven feet? one foot in six feet? one foot in five feet?

41. Traction on Common Roads.— The power re-
quired to draw a wagon over common roads varies with the
character and condition of the road. Experiments in Eng-
land with a four-wheeled wagon have given the following
results for level roads as indicated by a dynamometer:

Or cubical bloGke pavement). 3. 2h.6 2c. ke ee 28 to 44 lbs. per ton.
te WaCHCIAT POG Ao ete oe oy as bec aes 5d to 67 lbs. per ton.
GMPERVEL TOG cece a teas cokiegs Cline weve Secs 125 Ibs. per ton,
Rin Plan FOR: S tis ee ae So ak te bee ys 27 to 44 lbs. per ton.
Pn common dirt T6BWS 255.9 Obes cas. chee 179 to 268 lbs. per ton.

42. Traction Power of a Horse.— According to the
most reliable data available at present, which is certainly

26

far short of what could be desired, a horse in good condi-
tion, well fed, and weighing not Jess than one thousand
pounds, when actually walking at the rate of two and one-
half miles per hour during ten hours per day, can exert a
traction of one hundred pounds on a level road or a circular
horse-path like that of the sweep powers. In order that a
horse may exert his force most advantageously on a sweep-
power the track should have a diameter of thirty to thirty-
five feet,—never less than twenty-five.

43. Increased Speed Diminishes the Traction
Power.— If the horse walks more rapidly than two and
five-tenths miles per hour, or at a slower pace, the force
which he can exert changes also and is less or greater than
one hundred pounds. Experience seems to indicate that
at speeds between three-quarters of a mile and four miles
per hour, and continued .ten hours per day, the traction
will be given by the following equation:

2.5 miles x 100 =n miles x Traction.
Thus, at two miles per hour the traction would be:

2.5%: 100 —— 2 x" Praction:
whence, Traction = 23° or 125 lbs.

What would be the traction at one mile per hour? at
three miles? at four miles?

44. Diminishing the Number of Hours of Work
per Day Increases the Traction.— When the speed re-
mains the same, experience has shown that, between five
and ten hours per day, diminishing the time increases the
possible traction in about the same ratio, or

10 hours x 100 = n hours x Traction.

Thus, if the horse is to be worked only five hours the
traction he may exert will be

10 x 100 = 5 x Traction,
whence Traction == 199° = 200 lbs.

"What may the traction be when the horse works six
hours? seven hours? eight hours? nine hours?

45. Traction Power Diminished by Up-Grades .—
When a horse is forced to draw a load up a hill his power
of traction is diminished by being forced to lift his own
body at the same time. If he is going up a hill which
rises one in ten he must expend a force of one hundred

27

pounds per one thousand pounds to overcome the force of
gravity on his own body, and if the load he was drawing
weighed one thousand pounds the force of gravity would
require another one hundred pounds to overcome the tend-
ency of the load down the hill, leaving all resistance out
of consideration. Now if a loaded wagon weighs two
tons, and the hauling of a ton on a level road of the same
character as the hill requires one hundred and fifty pounds,
then the force necessary to carry the load up the hill ris-
ing one in ten would be, for a span of horses:

EAE LW OO MOTSOM in cite ae inst Mie sgt ee eh Rees wai ea 200 lbs.
Ee GAG CIN Wy OOH is < itt Lets cp sag. Gaene een aly oc ait a 400 *
sie LOM Lape LIOR OMe Sia 2 as ert pater Ae oe talee BeBe BuUOr
PIS" 2 RE Dw RRR a a ar ed SUR NS ew SY Cones Gh AMA Ory ee Aue! a ee kN 210 A as
MGENGTIE HOMAGS . 22 Road oe Set ee PGS cane ane eel 15) ) et

The rate at which the horses could move up the hill with
this load would be, by 43,

2.5 x 100= rate x 450;
whence, rate=729=—.55 miles per hour.

What would be the force required to move the same load
up a hill which rises one foot in twelve feet? one foot in
thirteen feet? one foot in fourteen feet? one foot in fifteen
feet?

46. Good Roads Make High Grades More Objection-
able.— It is evident that the better the road-bed is made,
thus reducing the traction on the level, the more objection-
able a hill becomes, because the force of gravity is just as
strong on a good road as on a bad one, and while a much
larger load may be hauled on the level, when the hill is
reached it cannot be drawn up. It was shown, in 45, that
-where the traction was one hundred and fifty pounds per
ton, a grade of one foot in ten feet added to that traction
one hundred pounds per one thousand pounds of load, in-
cluding the weight of the team. Now if the road-bed were
improved so as to reduce the traction to seventy-five
pounds per ton, double the load could be brought to the
hill, but unless the grade were also lessened, it could not
be moved over it. |

47. Soft and Uneven Roads.—The reason why the
traction is so heavy on soft and uneven roads will be read-
ily seen from a study of Fig. 13.

28.

At A, where the wheel is continually cutting into the
eround, it is, in effect, constantly tending to rise up a
hill which is steadily breaking down, and whose gradient
varies with the size of the wheel and the depth to which
it sinks into the ground. <A wheel four feet in diameter
which sinks two inches into the ground is constantly
tending to move up a hill which rises about one inch in
five and one-third inches. If the wheel has a less diameter
than four feet, not only does it sink more deeply into the
ground with the same load, but, for the same depth, it is
forced to tend. to rise up a steeper grade.

So, too, in raising the load over an obstruction, as
shown at B, there is, in a measure, the effect of rolling the
load up an inclined plane which is steeper in proportion as
the height of the obstruction is large and the diameter of
the wheel small. This case may, however, be more exactly
compared to lifting a load with a bent lever of the first
class, where the obstruction is the fulcrum, the distance
af the weight-arm and the distance )f the power-arm.
The higher the obstruction, and the smaller the wheel, the
more nearly equal are the lever arms. It is this fact
which explains, in part, why heavy loads may be moved
more easily over uneven roads on large wheels.

48. Wide and Narrow Wagon Tires.—The same fact
which makes a large wagon wheel more advantageous on
soft ground makes a wide wagon tire better than a nar-
row one, under the same conditions. It presents more
surface to bear the load, and hence does not sink as deeply.
into the ground as the narrow one does, and, this being
true, the load is moved with less traction. So far as
lightness of draft is concerned, broad tires are best adapted
to field hauling, but, for hard roads, there appears to be
but little advantage in this particular. On soft roads the

29

broad tires would be of advantage, provided all wagons
using the road were of this character, for then the cutting
of the roads would be less and the draught lighter. There
is, however, one serious disadvantage of wide tires on an
_ improperly drained road composed of sticky soil: during
wet times the wheels so fill with mud between the spokes
that the wagon becomes a load in itself.

49. The Telford System of Road Construction.—
The essential features of the system followed by this great
English road-engineer may be briefly stated to consist in
first leveling and thoroughly draining the road-bed, then
to lay upon it a solid pavement of large stones, these cov-
ered with a layer of stones carefuliy broken, and the whole
then covered with a layer of gravel or other fine material.
This was the system he foilowed in the highlands of Scot-
land: |

But where much heavier traffic was to be provided for,
the middle of the road-bed was made as firm as _ possible
by forming a pavement of large stones which were care-
fully laid by hand on a bed formed to the proper shape of
the road and previously well drained. All inequalities
were broken off the tops of these stones and the cavities
filled in, the size of the stone being 7 x 3 inches. Over this
paving was placed a layer of whinestone — a hard basaltic
rock — seven inches in thickness, the pieces being broken
so that none should exceed six ounces in weight and all
be able to pass through a circular opening two and one-
half inches in diameter. This layer was again covered
with binding gravel sufficient to fill up all the cavities.
Great attention was paid to this road until it became
thoroughly settled and then it stood the heavy traffic be-
tween Carlisle and Glasgow for six years, nothing being
required beyond cleaning the dirt off during that time.

50. The Macadam System of Road Construction .—
This differed from the Telford system in that it aimed to
secure, instead of the hard unyielding surface of that sys-
tem, a certain amount of elasticity. Macadam, after pre-
paring his road-bed essentially as described in the Telford
system, laid upon it several inches of angular fragments
broken from the hardest rock he could find, preference be-
ing given to granite, greenstone or basalt. This layer was
carefully watched by men, and as ruts appeared they were

a0.

raked full and fresh material added until a hard, even sur-
face was secured.

51. Road Drainage .—Perfect drainage is one of the
first requisites of a good road, and in some places both
surface and under drainage may be required. If the con-
tour of a road is such that the water of rains may stand
upon it in places, at all such points the road-bed softens
and ruts are cut more or less deeply into it. In the con-
struction of a road, therefore, the aim should be to give
the surface such a contour that all rain is shed completely
from it, and, at the same time, to depart as little from the
horizontal section as possible. In Fig. 14 is given a pro-
file of the Telford road-bed.

Lg. 14

The section adopted by Telford is quite flat and more
nearly a portion of the side of a flat ellipse than the arc
of a circle. It will be seen that in a road-bed thirty feet
wide the fall, in the first four feet from the center, is only
half an inch, in nine feet two inches, and in fifteen feet
-six inches. The aim is to have the road-bed as nearly flat
as may be in the central eighteen feet so as not to tilt the
load and force the traffic to follow one line. The tendency
is to get the surface too sloping, and when this is done
the weight of high loads is thrown more upon’ the lower
set of wheels, which tends ty» develop ruts on that side;
there is also a tendency to slide, so that the wear on the
road-bed and upon the wagon-tire is increased. The ridge,
upon the two sides, is intended to keep stones and dirt
from being thrown into the side drainage ditches. The
road-bed is often made only eighteen feet wide and the two
level strips used, one as a foot-path and the other as
storage ground for crushed rock and gravel to be used in
repairing the road.

Where underdrainage is needed, two lines of tile are
laid, one on each side “just outside of the road-bed but in-
side of the side ditches as shown in Fig. 15.

ol

The two lines of tile are used to prevent water from
running under the road-bed from either side to soften up
the ground, the surface, when properly made and kept in
repair, keeping water from entering from above.

52. Resuits of General Morin’s Experiments in
France. —General Morin, after a series of experiments car-
ried on at the expense of the French government, reached
the following general conclusions regarding roads and car-
riages:

1. The traction is directly proportional to the load, and
inversely proportional to the diameter of the wheel.

2. Upon a paved or bard macadamized road the traction
is independent of the width*of the tire when it exceeds
three to four inches.

3. At a walking pace the traction is the same for car
riages with springs as for those without springs.

4. Upon a macadamized or paved road the traction in-
creases with the speed above a velocity of two and one-
quarter miles per hour.

9. Upon soft roads of earth or sand the traction is inde-
pendent of the velocity.

6. The destruction of the road is in all cases greater as
the diameters of the wheels are less, and it is greater by the
use of carriages without springs than of those with them.

d3. The Pulley.— This mechanical power consists of a
wheel, having a grooved circumference through which a cord
or chain may pass, and so mounted as to revolve freely
about an axis. Pulleys are spoken of as either fixed or
movable, according as the axis of revolution is stationary
or travels with the load it carries. The two types are rep-
resented in Fig. 16.

At A is represented a simple fixed pulley in which the
power must be equal to the weight, because, in this case,
the pulley may be regarded as a lever of the first class,
where the axle of the pulley becomes the fulcrum, and then

oo

fs Ps)

the two arms are of equal length, each being a radius of
the pulley. At B the lower pulley is movable, traveling
upward with the load, and here we have the equivalent of
a lever of the second class, with the fulerum at the side of
the pulley in contact with rope 2. As the load hangs
from the axis of the pulley the power-arm is the diameter
of the pulley and the weight-arm is the radius, giving us
the equation:

Pixs? ASW Ww. Ag
or bx 3— 10 x1.

At C. D and E are combinations of several movable and
fixed pulleys. In C we have a system with several sepa-
rate cords, and in this the relation of power to weight is
expressed by the equation

P.x 2" =W.,,
where n equals the number of movable pulleys, or in C,
Pos WS

whence, 4 x2 x 2= 16.

In D and E we have two systems of pulleys where a
single continuous cord is used. It ~nakes no difference
whether the pulleys are arranged side by side, as in D, or
one above the other, as in E, the relation of power to
weight is expressed by the equation:

P. x No. cords supporting W.= W.,
whence for D, 4x4—16
. and for E, 4x 6=24.

These equations always suppose no loss due to friction
or in bending the ropes. There is, however, always a
large and variable loss, so the actual lifting power is less
than the theoretical.

35

54. The Horse-fork and Pulley.—The horse-fork and
carrier are used in lifting hay, as represented in Fig. 17.
The mechanical advantage is that of pulley B, Fig. 16,
diminished, of course, by the friction.

When no pulley is used next to the fork, the traction
exerted by the horse must always considerably exceed the
weight of hay lifted, so that a single horse is fully tasked
in freeing from the load and raising from two hundred to
three hundred pounds of hay.

| 9 fat =

55. Using the Pulley to Raise Heavy Stone Out of
the Ground.— The pulley may frequently be used to ad-
vantage in raising heavy stone out of the ground, and in
pulling stumps, as shown in Fig. 18.

.

1f a pulley is fixed to the chain in either of the above
cases, and the team draws upon a rope passing through it
to a fixed attachment, as shown, two horses will exert the
traction of four upon the stump or stone, diminished by

34°

the friction of the pulley. If the chain is attached to the
stone, and so passed over the top as to roll, instead of
drag, it from its place, the mechanical advantage will be
still greater.

56. The Serew.— This mechanical power is practically
a combination of the inclined plane and the lever. The
threads of the screw, and of the nut also, represent in-
clined planes free to slide one upon the other, One or the
other of these inclined planes is fixed while the other is
moved by means of a lever of some form, the movable one
carrying the load.

When the distance between the threads of a screw is
one fourth of an inch and the circumference described by
the end of the lever to which the power is applied is three
feet, the theoretical i lifted by a power of one hundred
pounds is

100 x 3x 4 x 12 = 14,100.

But the friction is so variable, and so great with very
heavy loads, that it is practically impossible to calculate,
from theory, the load which may be thus moved. None of
the mechanical powers can be so compactly constructed as
this, and at the same time allow so small a force to exert
so great a pressure. It is on this account that the screw
is so much used in the construction of vices, lifting-jacks
and presses. :

57. Friction Between Solids.— When one surface
rests upon another the roughness or inequalities of the
one fit, to a greater or less extent, into those of the other,
so that in order that one may be moved upon the other
either the two bodies must be, to some extent, separated,
or else the interlocking roughness must be broken away.
We have seen that molecules are not in contact in bodies,
and also that they are very small; from this it follows
that no matter how smooth two surfaccs may appear there
are always present inequalities of surface and always a
resistance which opposes sliding," and this is called
Friction.

58. The Friction of Rest or Static Friction Be-
tween Solids.— When two surfaces have been at rest with
reference to each other for a time there is developed the
maximum amount of interlocking, and hence the greatest
amount of friction. This is analogous to a load standing
upon a wagon over night, causing the wheels to become

OF
oo

depressed in the surface upon which they rest. The load
is started with greater difficulty because the wheels must
be rolled out of depressions, and this illustrates the condi-
tion of static friction. On the other hand, if the wagon
moves rapidly with its load, especially if over soft ground,
the wheels do not have time to form deep depressions in
the surface, and the resistance to forward progress is
smaller, and this is, in a measure, analogous to friction of
motion.

99. The Friction of Motion or Kinetic Friction Be-

tween Solids.—When two surfaces are sliding rapidly
one over the other there is not time to change direction
and develop the interlocking which is possible with a state
of rest, and consequently less power is lost when one solid
slides rapidly over another.

60. Influence of Pressure on the Friction of Solids.
—When other things remain the same, increasing the pres-
Sure increases the friction, and the amount of friction is
directly proportional to the pressure. Thus if one hun-
dred pounds produce a friction of two pounds, one thous-
and pounds will develop a friction of twenty pounds, and
this is independent of the amount of surface bearing the
load provided the pressure is not great enough to crush or
tear the surfaces.

61. Friction Between Liquids and Solids.—In this
case the amount of friction follows a different law, for it
increases with the amount of surface and also with the
square of the velocity of sliding motion. It is, however,
less than that between solids and* solids, and because of
this fact the oiling of the bearings of machinery dimin-
ishes very much the loss of effective energy through fric-
tion.

Where the velocities of revolution are slow, thick oils,
like castor oil, develop but little friction, but as the speed
is increased the friction increases very rapidly, and this
fact makes a thick viscous oil inapplicable as a lubricant
where high velocities, like those of the bowls of centri-
fuges, are required. On the other hand, when a very thin
fluid is used as a lubricant for slow motions there is time
for such freely-flowing fluids to be crowded out of inequali-
lies and thus allow the interlocking of solid surfaces to be
partially set up and develop a high friction for these low
speeds which the thick slow-flowing oils prevent; but for

36

very high speeds the thin fluid is able to maintain the de-
pressions of the solid surfaces full, and the much smaller
internal friction of the thin oil gives rise to a relatively
lower friction for such speeds.

It is upon this same principle, in part, that a thick
grease serves SO well the purpose of a lubricant to lessen
friction in the slow sliding which obtains in the axles of a
wagon.

62. Bad Effects of Dirt in Journals.—When grit of
any kind becomes entangled in the lubricants of any journal
or friction surface these particles bridge across or cut the
two films of oil which closely adhere to the two sliding
surfaces, so that friction is set up between solids rather
than between liquids as it should be, and there re-
sults not only a great loss of energy transmitted by the ma-
chine, but also an excessive wearing of the bearings, which
quickly destroys the fit so essential to steady, easy and
economical motion. Scrupulous cleanliness of the friction
surface of farm machinery should therefore be adhered to
as well as ample lubrication.

63. Belting.— The transmission of power by means of
belting is a useful application of the friction between solid
surfaces. In order that power may be _ economically
transmitted by this means the belt must be so tight that
little slipping takes place, and for leather belts this is
least when the pulley is covered with leather, hair side out,
and the belt runs upon this, hair side in. When the belt
is running at a high speed the tension may be less in pro-
portion to power transmitted, the activity of belting being
expressed by the equation:

Activity=Tv,

where v is the velocity and T the effective tension. When
the velocity is very great the tension may evidently be
small, and yet the activity or horse-power remain large, It
is on this account that small wire cables may be used at
very high velocities in transmitting very large amounts of
energy.

It is in consequence of this principle, too, that light
rope are successfully used in transmitting energy to the
centrifuge.

64. Sliding Friction in Machinery is Lost Energy.—
The sliding of the inequalities of friction’surfaces over one

37

another sets the molecules constituting them into a to-and-
fro motion, and all such motions represent energy lost either
in the form of heat or of sound; and it is because no ma-
chine can be so constructed as to run absolutely friction-
less that they, one and all, fail to transmit all the energy
which is imparted to them, and hence it is that perpetual
motion is an impossibility.

65. Friction in the Churn.— In all forms of churns the
agitation of the cream results in friction between the
molecules of milk and between the milk and the parts of
the churn, and this causes a transformation of the energy
brought to the churn from the source of power largely into
heat in the milk, which causes its temperature either to act-
ually rise or else prevents it from cooling as rapidly as
it would otherwise do. Now, if churning is begun with
the cream at too high a temperature and the surrounding
atmosphere is also too high, bad results must necessarily
follow.

STRENGTH OF MATERIALS-

66. A Stress.—When a post is placed upon a founda-
tion and a load of two thousand pounds set upon it, the
post is undergoing or opposing a stress of two thousand
pounds. When arope is supporting a load of one thousand
pounds in a condition of rest it is subject to a_ stress of.
one thousand pounds. ‘The joists under a mow of hay are
subjected to a stress measured by the tons of hay which they
carry.

67. Kinds of Stress,—Solia bodies may be subjected to
three classes of stresses which tend to break them and will
do so if the stress is great enough. These are:

1. A crushing stress, where the load tends to crowd the
molecules closer together, as when kernels of corn are
erushed between the teeth of an animal.

2. A stretching stress, as where a cord is broken by a
load hung upon it.

3. A twisting stress, as where a screw is broken by try-
ing to force it ‘into hard wood with a screw-driver.

68. Strength of Moderately Seasoned White and

Yellow Pine Pillars.—Mr. Chas. Shaler Smith has de-
duced, from experiments conducted by himself, the follow-
ing rule for strength of moderately seasoned white and
yellow pine pillars:
Divide the square of the length in inches by the
square of the least thickness in inches; multiply the quotient
by .00O4 and to this product add 1; then divide 5,000 by this
sum, and the result is the strength in pounds per square inch of
area of the end of the post. Multiply this result by the area
of the end of the post in inches, and the answer is the
strength of the post in pounds.

In applying this rule in the construction of farm buildings
the timbers should not be trusted with more than one-sixth
to one-fourth of the theoretical load they are computed to
carry, because the theoretical results are based upon aver-
ages, and there is a wide variation in the strength of in-
dividual pieces.

TABLE OF BREAKING LOAD, IN TONS, OF RECTANGULAR PILLARS
OF HALF SEASONED WHITE OR YELLOW PINE FIRMLY FIXED
AND EQUALLY LOADED, COMPUTED FROM C. S. SmITH’s

FORMULA.
a , DIMENSIONS OF RECTANGULAR PINE PILLARS IN INCHES.
ae 4x4 | 4x6 | 4x8 } 4x10] 4x12) 6x6 | 6x8 ol 6x12} 8x8 | 8x10} 8x12 10x10! 10x12
tons.\tons.|tons. tons.|tons.|tons.| tons. A tons.|tons.| tons.| tons.| tons.
8 | 12.1] 18.1] 24.2, 30 2) 86 3] 44.5] 59.3) 74 1) 88.9]101.7/126.9) 152.3] 182.7] 219.2
10 8.7| 13.0 17.4! 21.7| 26.1) 34.6} 46.2) 57.7] 69.2} 84.2/105.3) 126. 3] 158 6; 190 3
12 6.5] 9.7) 12.9] 16.1) 19.4) 27.2) 36.3) 45.4) 54.4) 69.7) 87.1] 104 5| 136 7 164.0
14 5.0} 7.4] 9.9) 12.4) 14 9) 21.7) 29.0) 36.2) 43.5] 57.9] 72.3) 86.8) 117.4] 140.9
16 3 9H 9) SL 88) L171, 00 235) -29).4) 35:3) 48) 41-6026) 972 271" 1010). 121-2
Sy | ees eer ahte srchol ier 3 DE ik al epee 2 14.6) 19.4] 24.3] 29.1] 40.8) 51.0} 61.2] 87.2} 102.6
20 12 2) 16.2} 20.3) 24.3) 34.8) 43.4] 521] 75.7] 90.8
Feel igh uel A AT Ce RR ee a 10.3) 13.7) 17 2] 20.6) 29.9] 37.4) 44.8) 65.8] 79.0
PENS Agee] lamas at EERE IG aes eae 8.8] 11.7 eel 17.6] 25.9] 32.3) 388.8} 57.9] 69.4

69. Tensile or Stretching Strength of Timber.—
The tensile strength of materials is measured by the least
weight which will break a vertical rod one inch square
firmly and squarely fixed at its upper end, the load hang-
ing from the lower end. Below are given the results of
experiments with different varieties of wood, but the
strengths vary greatly with the age of the trees, with the
part of the tree from which the piece comes, the degree of
seasoning, etc.

ea oes hacen apes oe SPI apc eee ar Ne OA 6,000 Ibs. per. sq. in.

PPLE SAVE YE os sek pred cog tars oe ane sg 11 000

IE Shee BIST, Ue ors ona SIA ee Rn ee A ae ies 10,000 Here eae

Oak, white and red......... PRR te iaus Neat tec ae a LOOGGP RS SE SR ae

LE TTILEN Qo 6 Re Ree gi ce Oct Sea pt I COL gt Bel Re BR A OO gS taa> SE sg Re

PUNKS, PING 27515... .2 : RS EOP a 068 0 eet at ah
70. Tensile or Cohesive ‘Streieth of Other Materi-

als. —

7M MRC ae 25 8 I a a a 16,000 to 28 000 Ibs. per sq. in.

Wrought iron wire, annealed. .... 30. 000 to 60,000 s cy

Wrought iron wire, hard.. Pete 50, 000 to 100, Ae Sir oo cece es
Wrought iron wire ropes, per sq. in. of rope 38, 10

Leather belts, 1,500 to 5,000, good........... SON 85. BAL AS aes
Rope, manilla, Buses “Gusta t aha et 12,000 cB ate
Rope, hemp, best..........-....... eRe A ets S170 8 RL Sate ah

71. Transverse Strength of Materials. — When a
board is placed upon edge and fixed at one end as_ repre-

40)

sented at A, Fig. 19, a load acting at W puts the upper
edge under a stretching stress.

We know from experience that in case the board breaks
under its load when so situated the fracture will occur
somewhere near 5-6. Now in order that this may take
place, there must be, with white pine, according to 69,
a tensile stress at the upper edge of ten thousand pounds
to the square inch, and if the board is one inch thick the
upper inch should resist a stress of ten thousand pounds at
any point from 5 to 1; but we know that no such load will
be carried at W. The reason for this, and also for its
breaking at 5 rather than at any other point, is found in
the fact that the load acts upon a lever arm whose length
is the distance from the point of attachment of the load to
the breaking point, wherever that may be, and this being
true the greatest stress comes necessarily at 5.

If the board in question is 48 inches long and 6 inches
wide, it will, in breaking, tend to revolve about the cen-
ter of the line 5-6, and the upper three inches will be put
under the longitudinal strain, but according to 69, is ca-
pable of withstanding
, 3x 10,000 Ibs. = 30,000 lbs.

without breaking; but in carrying the load at the end, as
shown, this cchesive power is acting at the short end of a
bent lever whose mean length of power-arm is one-half of
4—5 or 1.5 inches, while the weight arm is _ forty-eight
inches in length. It should, therefore, only be able to hold
at W. 937.5 pounds; for
as Px PLAS = Wx Wo,
we have, 3,000 x 1.5— W. x 48,
whence W. = 222°° = 937.5 lbs.
When a board, in every respect like the one in A, -¥Fig.
19, is placed under the conditions represented in either B

4]

or C, Fig. 19, it should require just four times the load to
break it, because the board is practically converted into
two levers whose power-arms remain the same, but whose
weight-arms are only one-half as long each.

72. The Transverse Strength of Timbers Propor-
tional to the Squares of their Vertical Thicknesses.—
Common experience demonstrates that a joist resting on
edge is able to carry a much greater load than when ly-
ing flatwise. If we place a 2x4 and a2x8, which differ
only in thickness, on edge, their relative strengths are to
each other as the squares of 4 and 8, or as 16 to 64. That
is, the 2x 8, containing only twice the amount of ]umber
as the 2 x 4, will, under the conditions named, sustain four
times the load. The reason for this is as follows: In Fig.
20 let A represent a 2x4 and Ba2x8.

L

In each of these cases the load draws lengthwise upon
the upper half of the joist, acting through a weight-arm
F. W. ten inches in length, to overcome the force of co-
hesion at the fixed ends, whose strength, according to 69,
is ten thousand pounds per square inch, or a total

of 2 x2.x 10,000 lbs.=40,000 lbs. in the 2x 4 joist,
and of 2 x 4 x 10,000 lbs.=80,000 lbs. in the 2 x 8 joist.
These two total strengths become powers acting through
their respective power-arms F, P., whose mean lengths
are, in the 2x 4 joist, one inch, and in the 2 x8 joists, two
inches.
Now we have, from 29,

Pre. as We WA,

42

and substituting the numerical values, in the 2 x 4 joist, we
get
4x 10,000 x 1 = W. x10,
or 4x10,000=10 W.,
and W =4,000.

Similarly, by substituting numerical values in the case of
the 2 x 8 joist, we get

8 x 10,000 x 2—=W. x 10,
or 16x 10,000=10 W.,
and W.=16,000.

It thus appears that the loads the two joists will carry
are to each other as four thousand is to sixteen thousand,
or as one is to four; but squaring the vertical thickness of
the two joists in question we get for the 2 x4 joist

4x4—16,
and for the 2x8 joist
2x 667:

but sixteen is to sixty-four as one is to four, which shows
that the transverse strengths of similar timbers are propor-
tional to the squares of their vertical diameters.

73. The Transverse Strength of Materials Dimin-
ishes Directly as the Length Increases.—lIt will be
readily seen from an-inspection of Fig. 20, that lengthen-
ing the pieces of joists, while the other dimensions re-
main the same, lengthens the long arm of the lever, while
the short arm remains unchanged; and since the force of
cohesion remains unaltered, the load necessary to overcome
it must be less in proportion as the lever arm upon which
it acts is increased. Thus, if the 2x 8 in Fig. 20 is made
twenty inches long, we shall have, from 29.

P= Pt AS Wee Wee
and by substituting the numerical values we get
80,000 x 2= W. x 20.
hence
W.=8,000,
instead of sixteen thousand, as found in 72.
74. The Constants of the Transverse Breaking

Strength of Wood.—Since the laws given in 71, 72 and
73 apply to all kinds of materials, it follows that the act-

43

ual breaking strength of different kinds of materials will de-
pend upon the cohesive power of the molecules as well as
upon the form and dimensions of the body which they
constitute. The breaking strength of a beam of any mate-
rial is always in proportion to its breadth, multiplied by
the square of its depth, divided by its length, or,

Breadth x the square of the depth

ee Pe ae lenge:

and if the breadth of a piece of white pine in inches is four,
its depth in inches ten, and its length in feet ten, we shall
have, taking the length in feet,

4x10x 10

sm) asa
Now if we find by actual trial, by gradually adding weights
to the center of such a beam, that it breaks at eighteen
thousand pounds (including half its own weight), the ra-
tio between this and forty will be

18,000
40

=4(,

=—Z0YU,

and as this ratio is always found for white pine, when the
breadth and depth are taken in inches and the length in
feet, no matter what the dimensions of the timbers may
be, four hundred and fifty is called its breaking constant for
a center load,

For other materials this constant is different, and has
been determined by experiment and given in tables in va-
rious works relating to such subjects. The following are
taken from Trautwine:

745. Breaking Constants of Transverse Strength of
Different Materials .—

WOODS.
TEVA Ve EEG een Ce et Sem Ey Gs BCE Po Peet) 650 Ibs.
Beri nee we Ne eon ey tai ghe Fo NA ALE 600 *
Or or ROTIDRIY BirCr occ si FO ee Oe. S50... *
American Hickory and Bitter-nut..... 2... 0 oie cee ence 800 *
OA TAC PMT CIO cu Satan aE ee te 400 *
rece Ug AI ga Sao Se ra RRS a ee 750 *
American White Pine............ FN SA eg ce Ee ae a Baty +
A MGPLenr: VOMMw iE ING Oo nalts. 2 ls Soe eee See 5005:
US TRIES gel 6, ait, PA cf NGI PIs ea eS 550“
A CRTD AT WY TUE A ME te dae) os! sis bine cach ne ocak ch cu 6O00'.™

BOE TSEC eT MTOR TS Si SRS ESE en 800? *§

44

METALS.
CCE) eMtW Wn 11 Wepre alte Se ce PSN ches GR 1 PRR ed 65 es 1,500 to 2,700 Ibs.
Wrought Tron bendsyahae fey) ook oen.u Newent tees 1,900 to 2,600 lbs.
Brass. ov os sche aac en ety Grae sme SAL a aes 850 Ibs.

76. To find the Quiescent Center Breaking Load of
Materials having Rectangular Cross-sections when
Placed Horizontally and Supported at Both Ends .—
In placing joists and beams in barns it is important to
know the breaking load of the timbers used. This may be
determined with the aid of the following rule and the table
of constants given in 79:

Roie.—Multiply the square of the depth in inches by the
breadth in inches and this by the breaking constant given in
753 divide the result by the clear length in feet, and the re-
sult is the load in pounds.

But in the case of long, heavy timbers and iron beams
one-half of the clear weight of the beam must be deducted
because they must always carry their own weight.

Square of }
depth ‘| x Breadth in inches x Constant
in incbes \
Brea’ ing load=-
Length in feet.

What is the center breaking load of a white pine 2 x 12
joist twelve feet long?
pan EES e410 ena ie.

12

What is the breaking load for the same ten feet long?
fourteen feet long? sixteen feet long? eighteen feet long?

Solve the same problems for other woods.

77. General Statements Regarding the Quiescent
Breaking Loads of Uniform Horizontal Beams .—ltt
the center quiescent breaking load be taken as J, then,
when all dimensions are the same, to find the breaking
load:

(1) When the beam is fixed at both énds and evenly
loaded throughout its whole length, multiply the result
found by 76 by two.

(2) When fixed at only one end and loaded at the other,
divide the result obtained by 76 by four.

(3) When fixed only at one end and the load evenly dis-
tributed, divide the result obtained by 76 by two.

(4) To find the breaking load of a cylindrical beam, first

Breaking load=

45

find the breaking load of a square beam having a thickness
equal to the diameter of the log and multiply this result
by the decimal .589.

78. Breaking Load of Rafters.—In finding the
breaking load of timbers placed in any oblique position as
Show in Fig. 21, take the length of the rafter equal to the
horizontal span AC and proceed as in 76 and 77,

79. Table of Safe Quiescent Center Loads for Hor-
izontal Beams of White Pine Supported at Both
Ends.— In this table the safe load is taken at one-sixth
of the theoretical breaking load. This large reduction is
made necessary on account of the cross-grain of timbers
and joists and the large knots which weaken very materi-
ally the pieces. Where a judicious selection is made in
placing the joists, lay-
ing the inherently weak
pieces in places where
little strain can come
upon them, much _ sav-
ing of lumber may be

Fig.2/ made.
===
= | Span 10 feet. || Span 12 feet. || Span 14 feet. Span 16 feet.
Eien n= Ai VN Tota ®
is |
Z BREADTH. BREADTH. BREADTH. BREADTH.
z i |
& /2 in /4 in./6 in.|/2 in.|4 in.|6 in.|/2 in, 4 in./6 in.|l2 in,|4 in.'6 in.
=

—___— ee” nn s”| | | | | |

|
lbs. | lbs | lbs. || lbs. | lbs. | lbs. lbs. Ibs. | lbs. lbs. | lbs. | Ibs.
4| 240) 480) 720 200; 400' 600 172) 344 516} 150 3uU| 450
6 540) 1080) 1620 450 900} 1350 386 772| 1158 336 672) 1008
8 960} 1920 is) 800 1609} 2400 686] 1372} 2058 | 600} 1200! 1800
0 ~
9

1500} _ 3000} 4500}! 1250° 2500 3750|| 1072] 2144) 3216

C 2808
2160} 4320! 6480 1800) 3600} 5400;| 1544] 3088 | 1350} 27

4050

BREADTH. BREADTH. BREADTH. BREADTH.

|
8 in./10 in|/12 in||8 in.|10 in 12 in 8 in,/10 in'12 in||/8 in. 10 in|/12 in

——

lbs _| lbs. | Ibs. lbs. | lbs. | lbs. lbs. | lbs. | lbs Ibs. | Ibs. | lbs.

4) 960] 1200} 1440/| 800} 1000 1200'! 688 86c. 1032] 600| 750/ 900. -
6} 2160; 2700) 3240], 1800] 2250 2700] 1544] 1930|- 2316)! 1344/1680! 2016
8} 3840} 4800} 5760!| 3200 4000) 4800 2744) 3430! 4116|| 2400) 3000) 3600
10) 6000; 7500| 9000/] 5000; 6250] 7500] 4288) 5260) 6432|| 3744) 4680 5616
12| 8640, 10800 12960) |

tad! en 10800 6176 7720) 9264 ney sai 8100

ee ee
————————————— — SsSsoo_—SS—S—SSS_—_,

FLUIDS.

SO. Surface Tension of Liquids.—The molecules of
liquids exert an attractive force upon one another, but this
is most manifest at their surfaces because the interior
molecules, being pulled equally on all sides by surround-
ing molecules, have their tendency to move balanced in
every direction. The surface conditions, however, are dif-
ferent, as will be seen from Fig.
22, where the arrows at A and
B show the direction of the ac-
tion of molecular forces on the
interior and surface molecules
respectively. The unbalanced
condition of forces between the
surface molecules of liquids
causes them to act like a thin
elastic membrane or skin,upon the liquid within. It is the
tension of these films which causes rain drops, and the shot
from the shot towers to assume the spherical form when
falling. The same action gives this form to the fat glob-
ules of milk, to dew drops on cabbage leaves and to drops
of water on a dusty surface. It is the same surface ten-
sion which sustains a fine needle on the surface of water
and which enables certain insects to walk upon water.

Sl. Strength of Surface Tension.—The strength of
the tension of fluid surfaces is different for different liquids,
and it varies with the surfaces which are in contact. The
following table gives the relative surface tensions in cer-
tain cases:

Between clear water and air................. ie vest beko Ge, HO@Rnim
Between olive ol} and aire. 23 Solos Da ees > Sk Sateen 37, nearly.
Between chloroform ane ger ec ee ee Wik wis Kin 31, nearly.
Between water and olive oil.......... aitaRva lund Sraer oak Gears 21, nearly.
Between water and chloroform............. ee tes er ne 30, nearly.

These differences of tension give rise to a great variety
of phenomena. When oil is placed on water it tends to
spread out indefinitely in a thin sheet. On the other
hand, if a little water is placed upon chloroform it tends

47

to draw it into asphere or drop. The reason for these facts
will be understood from Fig, 23.

Fig. 28.

In A, on the circumference, where the drop of oil, air
and water meet the surface molecules are actuated by three
sets of forces represented in direction by the arrows and
in intensity by the numbers, and it is evident that the
molecules so affected must move in the direction of the
stronger force, and as the surface tension of the water-air
surface is strongest, the oil is drawn out indefinitely until
an extremely thin film results. It is on this account that
so small a quantity of oil put overboard by a vessel at
sea, in times of storm. covers so large an area as often to
effectually protect the vessel from the dangers of wave-
action. It is in accordance with the same principle that
water and other fluids spread out over the surfaces of solids
which they will wet.

In the case of B, where a drop of water is placed upon
chloroform, the conditions of A are reversed and the water
at first tends to draw up into a sphere. It is in the same
manner also that water on a dusty floor or on cabbage
leaves is drawn up into drops.

82. Capillary Action.— When slender glass and other
tubes, whose adhesive force for water is greater than the
attraction of the molecules of water for one another, are
placed vertically in water, the water is seen to rise in
them and come to rest above the level of the water in the
surrounding vessel. It will also be observed that the height
attained by the water in different tubes varies inversely
as their inside diameters. The rise of liquids in slender
tubes is in accordance with the principle illustrated in Fig.
23 A, the chief difference being that the movement is in
opposition to the force of gravitation and that the rise is
checked when the down pulling forces balance the surface
tension.

The rise of water in soil and of oil in a lamp wick are
other instances apparently due to a closely allied, if not
identical action.

48

If on the other hand, the attraction between the liquid
and the walls of the tube is less than the attraction among
the molecules themselves, so that the walls are not wet by
it, the surface of the liquid in the tube is depressed, the
amount being greater as the diameter of the tube is less.
This depression is in accordance with the principle ex-

lained under B, Fig. 23.

S83. Influence of Surface Tension on Lactometer
Readings. — The rise of water on the sides of a tube float-
ing in it, as in the case of the lactometer, tends to draw it
more deeply into the liquid and thus gives it a higher read-
ing. On the other hand, if the liquid has its surface tension
weakened by being overspread with oil, or if the stem of
the lactometer is made greasy by handling or otherwise,
it will then be lifted out of the liquid and too low a read-
ing will be indicated, It is important, therefore, in de-
ter mining the specific gravity of milk by this method to
see that the lactometer is thor oughly clean.

S4. Solution of Solids in Liquids.—When salt is
placed in water the adhesion between the molecules of
water and salt is at first stronger than the cohesion
between the molecules of salt, and successive layers of salt
molecules are separated and disseminated through the
liquid. If the quantity of salt placed in the water be
large enough, there will come a stage when the quantity
of s salt dissolved in the water has so weakened its adhesive
power that it ceases to be strong enough to overcome the
molecular cohesion of the salt and at this stage further
solution is stopped.

In the majority of cases where solids are being dissolved
a rise of temperature so weakens the cohesive iorce that
solution may be carried still further. It is in part the
greater solubility of soil ingredients in water at high tem-
peratures than at low that makes a warm soil more con-
ducive of plant growth than a cold one.

85. Diffusion.—When a phial, nearly full of salt or
sugar, is placed in a vessel and the vessel carefully filled
with water so as to cover the phial, the salt or sugar will
in time be dispersed through the whole water. The rate
at which this diffusion takes place is different for different
substances, and in the table below, the numbers indicate
the relative lengths of time required for different substances
to travel the same distance in water under like conditions,

Hydrochloric acid ...... 6s ces. Seta t teaed Me kid eo ence Sod eek t
SS OE RE ee BRM AME Teens ss SAAC A Wid oS gol cle woke 2.33
RE a eR IN creat Oem Sele SAS wee thee. cumiecy vi
PROS HM RUD MEUG tf. Vee Clk ek td uae eae sete eectaes OM
RRR Na NIMS EE 1S Mth D. oe Gee IT ERIS ES Ge CaP ON d owas De Salk w ale, va'Ge ales 49

All substances diffuse more rapidly at moderate temper-
atures then at low ones, and here is another reason why
a warm soil is more conducive to plant growth than a cold
one, for the transfer cf food from soil to plant is partly a
process of diffusion.

If two gases are placed in two vessels and an opening
be made connecting them, the molecules of each kind of
gas will travel from their respective vessels and enter the
other until a uniform mixture results. We have seen that
the velocities with which molecules travel are inversely
porportional to their densities, and it is found that the
rate of diffusion of gases obeys the same law, the lighter
gas diffusing more rapidly.

Oxygen enters the air cells of our lungs and carbon
dioxide leaves them by this process of diffusion, and the
same thing is true of the intercellular air passages of
leaves into which the stomata lead.

S6. Osmosis.—Im case two liquids, which mix, are
placed on opposite sides of a porous membrane capable of
being wet by one or both of them, currents are estab-
lished in one or both directions. The membrane first be-
comes pentrated by the liquid having the strongest attrac-
tion for it, and on reaching the other side theliquid diffus-
ing into it causes its attraction for the walls to be les-
sened, and this allows this portion to be crowded out into
the liquid which has been approached and a stream thus
established. If the pores in the membrane have a diame-
ter exceeding aso inch, a return current of the second
liquid is established toward the first along the central por-
tion of the pores. It is by this process that the tissues of
plants and animals are nourished. Here again a warm
temperature makes the streams more rapid, and so still
another reason is found for having the soil in which the
roots grow sufficiently warm.

Osmose of gases as well as of liquids also takes place,
and it is by this process that animals get their supply of
oxygen and plants their supply of carbon dioxide.

87. Viseosity.—When the molecules constituting any
body are forced to move past one another their mutual mo

50

lecular attraction causes a dragging which sets the dis-
turbed molecules vibrating, and this molecular vibration
is at the expense of the energy which produced the move-
ment. This dragging effect of the molecules is called vis-
cosity, and the amount of energy transformed into heat in
consequence of it is a measure of the viscosity. The fat
globules in rising through milk serum encounter this vis-
cosity, and a part of the energy of the creaming force is
transformed into heat, causing the cream to rise more
slowly than it would if there were no viscosity.

Liquids, in flowing through pipes or other channels, are
retarded by viscosity so much that in long and slender
pipes the amount of water discharged is very much dimin-
ished. This fact makes it necessary, in tile draining and
in conveying water in pipes to pastures or other points,
+o use larger pipes than would otherwise be necessary. In
all those cases where the liquid wets the surface past which
it flows the friction is due wholly to the viscosity of the
fluid, for the layer in immediate contact with the sur-
face remains stationary while the other molecules move past
them. This is the case with oils used to diminish friction
in machinery.

When the inner surfaces of pipes are rough and uneven
the flow of liquids through them is further diminished by
the direction of the current being changed at these in-
equalities and thrown toward the center of the pipes
across the course of the central current. It is important,
therefore, in selecting tile to avoid those having rough in-
teriors, and also in laying them to avoid making shoulders
at the junctions of the many sections.

The viscosity of air and other gases is due to the pro-
miscuous traveling of the molecules, which causes those mov-
ing transverse to the stream to be caught in it and thus re-
tard the onward movement, acting much as the eddy-cur-
rents set up by inequalities in the surface of water pipes.

SS. Pressure of Fluids.—The great freedom of motion
of molecules in masses of liquids and gases causes them to
exert an internal and to transmit an external pressure equal
and uadiminished in all directions. The proof of this law
for liquids, is found in the fact that when two vessels are so
connected that water can flow from one to the other the
water will have the same height in both vessels, no mat-
ter what form or direction the communicating passage may

d1

take. The spherical form of a soap bubble in mid-air
proves the law true for air; for if the pressure from all
sides were not equal the form of the bubble would change
from that of a sphere.

89. Pressure of Liquids in Vessels.—The pressure
exerted by liquids on the walls of vessels which contain
them is due to their weight, and, for a given liquid, is
always proportional to the depth. In the following table
the weight of water per cubic foot and pressure per square
foot are given for different temperatures:

PRESSURE IN LBS. PER SQ. FT. AT DIFFERENT DEPTHS.

Tem. | Lbs. per
Fahr. cu, tb.

At 2 ft.| At 4ft.| At 8 ft./At 10 ft.| At 20 ft. | At 40 ft.

32° 62.417 124.83 243. 67 499 34 624.17 1248.34 2476.68

39° .2 62.425 124.85 249.70 499.40 624.25 1248.50 2497 .00
40° 62.423 124.85 249.69 499.38 624.23 1248.46 2496 92
50° 62 409 124.82 249.64 499 .27 624.09 1248.18 2496 36
60° 62.367 124.73 249.47 498.94 623 . 67 1247.34 2494.68
70° 62.302 124.60 249.21 498 42 623 02 1246.04 2492.08
80° 62.218 124.44 248.87 497 74 622.18 1244.36 2488 .72
$0° 62.119 124.24 248.48 496 95 621.19 1242.38 2484.76
212° 59.7 119.40 238.80 | 477 .60 597.00 1194 00 2388 .00

The pressure of the water on the bottom of. a vessel can
always be found by multiplying the area of the bottom in
Square feet by the depth of the water, and this product by
the weight of a cubic foot of water, which is nearly 62.42.

P. on bottom=area x depth x 62.42.

The lateral or side pressure is proportional to the depth,
following exactly the same law as that for the
pressure on the bottom. Since the depth at the surface is
zero, the lateral pressure is also zero, and since the depth
at the bottom of a vessel is the greatest, the lateral pres-
sure must there be at its maximum; these being true, the
mean pressure on the side of a vessel would be the pressure
at one-half the depth of the liquid, and, hence to find the
total pressure on the side of a vessel, we have

Raden le eldna: death & Goo.
‘Do taleten et ieee

~

What is the total pressure on the bottom and on the
sides of a reservoir 6 x 6 x 6 feet filled with water at
sooo tr at oo Bye

a2

What is the lateral pressure on the lower six inches of @
cylindrical tank ten feet in diameter filled with water to a
depth of ten feet?

If thispressure is to be sustained by an iron hoop composed
of one-eighth inch band iron, how wide should the hoop be?

90. Pressure of Grain in Bins.—The downward pres-
sure of grain in bins follows the same law as that of liquids,
but the lateral pressure is always less on account of the
friction between the kernels. When grain is heaped up on
a level surface it is found impossible to pile beyond a cer-
tain height without increasing the diameter of the pile at
the base. <A certain angle of slope is maintained, which
for wheat is about 31°, about 30° for shelled corn, and for
oats about 34°.

The friction of the kernels upon’one another is just great
enough to maintain this angle, but in filling a bin with
wheat, for example, introducing it at the center, after a
certain quantity has been added the base of the cone is
extended until it reaches the sides of the bin, and the ad-
dition of any further quantity brings into existence an
outward pressure on the walls of the bin tending to spread
them. The case is analogous to the retaining walls which
are often built to prevent sand or earth from caving or
sliding. The amount of this pressure and the method of
computing it will be understood from Fig. 24.

CMMC represents a section of a bin sixteen feet square
and eight feet deep filled with shelled corn. The cone
MOM represents the cone
of grain which exerts
no pressure on the sides
of the bin. The remain-
ing portion MOMCC has
its weight divided be-
tween the sides and the
bottom, the sides pre-
venting it from sliding
down the inclines OM,
OM. The pressure on the side CM, according to the
theory of retaining walls, is equal to the weight of
tCM, acting as a wedge between the surfaces tM and CM.
As the wedge is a movable inclined plane where the force
acts parallel to the base, the pressure may be computed
from the equation

D3

Power x base=weight x height.

The height, tC, is 4.5 feet, and the base CM, eight feet.
The weight is the weight of corn composing the wedge,
and is equal to

4.5x8x16x 1728 x56
2 x 2150.4

Substituting the numerical values in the equation of the

wedge above we get

==12958.72 Ibs.

Power x 8=12958.72 x 4.5, whence, power=7289.28 lbs.

as the total pressure on the side of the bin, which is an
average of 56.9 pounds per square foot.

91. The Principle of Flotation.—When a body is im-
mersed in a fluid it is pressed or lifted upward with a force
exactly equal to the weight of the fluid it displaces, and it
is because of this fact that stones can be moved so much
more readily under water than out of it. Thus, a stone
containing exactly one cubic foot will be lifted up, when
in water, “with a force of 62.42 pounds, and hence appears
that much lighter when moved under those conditions. It
is this principle which makes possible water navigation
and the ascension above the earth’s surface in balloons.

We Specific Gravity.— When the specific gravity of
cast iron-is spoken of as 7.2 the meaning is that a cubic
inch or a cubic foot of that body weighs just 7.2 times as
much as the same volume of water, and when the specific
gravity of white pine is given as .4 the meaning is that a
given volume of that wood weighs only .4 as much as an
equal volume of water; hence, for liquids and solids, we
have the equation

weight of body
weight of equal volume of water.

Specific gravity=

Air is taken as the standard of specific gravity for gases.

93. To Find the Specific Gravity of Solids. ~The
principle of flotation affords a very simple means of find-
ing the specific gravity of solids. Since any body immersed
in water displaces its volume of water, and since it is also
buoyed up by a weight equal to that of the water displaced,
it is only necessary to weigh the body whose specific grav-
ity is desired, both in air and in water, the difference in
weight giving always the weight of a volume of water the
size of the body whose specific gravity is sought. The

o+

weight of the body in air divided by this difference gives
the specific gravity, and hence the rule

ecttte gravity Neigh’ of solid in air
peciuc sravlly—joss of weight in water.

Suppose a body weighs ten in air and when immersed in
water only eight. In this case the weight of a volume of
water equal in size to that of the body is

10—8=2
and hence, by the rule above, we have

Specific gravity =19=5.

Find the specific gravity of a body weighing fifteen in
air and fourteen in water. What will be its specific grav-
ity if it weighs in water; three? one? four? six? seven?
ten? twelve?

94. Table of Specific Gravities and Weights per
Cubie Foot of Different Substances. —

Sp.gr. Weight.

Ashe Am: whitesdnys.cct-be Pays See ee he ieee ee “61 © 38..elbs:
Anthracite coal, moderately shaken.............. 58 \0 on
Brick common bard). 7.05 oc S54 6s ein tere sete eee RD VF Se
Carbon dioxide, referred tO air. 2.2 ce ene ae 15 x
@harcoal(pities dG) 0akS-.-00 5 to ace mec ahcaeens DNase
Olay, dry, in“lunmip, loose: ook oo aga kieseinin le iale waste Gane
Conk: 7 bitGninogs S040 02 taxwataehicy hae chemin telecine L Sb: eB aaa
Coal, bituminous, broken, loose......:.. ...-...- OOH?
Mopper, Lolleds oe. a esi ee sepie has ckeletendetan toes 8. O° bborea
Earth, clay loam, dry, nat. condition............. TONE a
Marth, clay loam, saturated. 5.22 sen). sues ates oe ae
Earth, reddish clay, dry, nat. condition........... 85a.
Harthreddish clay, caturated.e..<: os.e0.. -2os. 2 © 108. =
Barth, fine sand, nat: condition .>. 02. .%......... LOGE Fes
Earth, fine sand, saturated........... ptetiae innl hore ge
i ico bees by eee Ret them etr ene Scena a wanna Casein 00 Lion ee
Gypsum, ground, -loose..7 2. c,h een ee te OG;
CUPPA VOLE EWS cliche GON ee Wieser, Waren aie a wide eg sees te 106°> 545
Hemlock dry scdsa ese note: area ee eo Ee RE Oy ge
Pr eOTY ORY hadi ile sae tnelers «bas areie ola che Wy aioe niin 85 oer Sauaeaen
Tron. -Gast ANG Re Bee ew eye eke vei water are ee 7 2b 450 me:
dK Gs erat NIE STG EE ny Spe a: hr My PRR ERNE a ahs ME) Se it Ty 92. (bia
A ear an Ee Rice nee at oe cals ct iial are cc patie dapat “95: n@iars
1 OAT Vo Pe oe gare inc aA sO, Manis there Sv AAC Reh Oe 11°38. 70940)-5"
Himestone, brokennec vi ee cae aie ae oe eee Le 96%
Wisp les Ory Fs eit c acs see ste enlie'e be one oo atom cheng eed 19) AD ne
Oak, whitey Gry hie) Ge oss. Settee pis cep ienbens oat etta S77 ¢ Sie Ae

Oak. red; black, dry 20-55: abi TR AS ah Oe ee wie ca Bi eae

CE WMAND CS REEN Ee tae sd cloe ainsi A ote 6 ahve gdp a. He hai she 40 ->°25- Ibs:
ei Youows MOTLNErNy. <a cece Reg ieeeres Seca oo 343 “
SHIA ORIRBY Tt as oles ropesetene NPR rae aas wa.cte vavaie es Ae iG
Am ROTO Ss Sia asiakc, PRIN a Ser ee cl ento'o wea Maceiens BAD | DO ve $8
Pe iachaviedt HOGI TAALOTL OA on airititania ts hoo Ser’ 22. 2.6°iagee > Se
SHOW COMEPACLOG: Dy Batt) 2250) B60 aio 3) sialaco cles ieia Sid's 15.50 “
PERG eis tos ager, SRE Ee OMS eae a wikis Sis, hace, oie he 7.85 490 “*
Niet ie OA ON hay ose Ree Sir aaa Oe es hata PON rs ests falas g 1 62.35 “

95. To Find the Specific Gravity of Liquids.—The
principle of flotation stated in 9] also furnishes an easy
method of finding the specific gravity of liquids, which is
done as follows: Find the difference in weight of any con-
venient solid in air and in water and then in the liquid
whose specific gravity is desired. Suppose the solid se-
lected loses a weight of one in water and a weight of .75
in another liquid, then a volume of water, the size of the
body taken, weighs one, and an equal volume of the second
liquid weighs .75. Then by the rule we have:

96. The Lactometer.—The use of the lactometer in
determining the specific gravity of milk is also an appli-
cation of the principle of flotation, and is simply a modi-
fication of the method in 95. In this instrument, as shown
in Fig. 25, the slender and uniform stem is graduated so
as to give the specific gravity by direct reading.

97. Atmospheric Pressure.—The air which every-
where envelops the earth to a depth prob-
ably exceeding five hundred miles has
weight and exerts a pressure in all di-
rections upon all bodies in it. This
pressure at the level of the sea, is capa-
ble of sustaining a column of mercury
29.922 inches high on the average when
the temperature is at 32° F. and is
equal to a pressure of 14.73 pounds to
the square inch. The amount of this
pressure depends always upon the total
quantity of air that exists at the time
above the point where the pressure is
exerted. This being true, places situ-
ated above the level of the sea have a less pressure because
they are nearer the upper limits of the air.

fig. 26

Gs, -

98. Variations in Atmospheric Pressure.—The pres-
sure exerted by the air at any place is almost constantly
changing, so that it is rarely the same at any two con-
secutive moments: these changes are not as a rule very
large or very rapid. A change of one-half a pound to the
square inch in twenty-four hours is a large change, and a
change of one pound to the square inch never occurs during
short intervals, except when very violent storms are in
progress. These changes in pressure are due to the fact
that the air is disturbed by currents and waves which owe
their origin to various causes.

99. Soil Breathing.— When the atmospheric pressure
is heavy over a given locality the air is driven into the
air passages in the soil of that place, and then when the
pressure changes again, becoming lighter, the compressed
air expands and escapes; thus there is maintained an ir-
regular but constant breathing of the soil in consequence
of these changes in atmospheric pressure. The soil breath-
ing is further maintained, especially during the growing
season, by the daily changes in temperature which occur
in the upper thirty inches of soil. During the day
the expansion, due to heating, forces air out and then at
night the cooling causes the air left in the soil to contract
and the reverse action takes place. Just how important
this soil breathing is in the operations of tillage we do not
know. Its amount will be increased or diminished as we
increase or diminish the porosity of the soil and as we
modify the conditions which affect the diurnal changes of
temperature.

100. Effect of Atmospheric Pressure on _ Soil
Water.— When soil is nearly saturated with water, air
can neither enter nor escape from it readily except where
large openings or passages exist. In consequence of these
facts, when the air pressure over a region becomes less
the springs of such regions often discharge more water
and the water may. stand higher in the wells. The air
confined in the soil and unable to escape rapidly, expands
when the pressure falls and forces’ the water toward any
openings which may exist. The reverse action also takes
place when the air pressure increases, causing: the water
in the wells to be depressed and the same springs to dis-
charge more slowly. “Blowing wells” owe their character
also to the changes in atmospheric pressure.

Py
oi

101. The Suction Pump .— The common pump is one
of the applications of atmospheric pressure. It should be
understood, however, that the pressure of the air is in no
way a source of power, it originates no part of the energy
expended in pumping. Practically the only part the air
plays in pumping is that of crowding the water up into
the cylinder of the pump after the ‘lifting of the piston
has removed the pressure from the water in the suction
pipe. The height to which the atmosphere will sustain a
column of water at sea level is thirty-four feet; but a pump
producing a perfect vacuum could not raise water to that
height on account of the downward pressure exerted by
the vapor of water and the air contained in water rising
into the vacuum formed by the pump and exerting a pres-
sure downward upon the column of water raised: Com-
mon pumps are necessarily so imperfect in their action
that it is found impracticable to have the suction pipe
ionger than sixteen to twenty feet above the water to be
raised.

102. Size of the Piston.— The amount of water dis-
charged by a suction pump is determined by the length
of the stroke and the area of the piston; and these in turn
are determined by the strength of the pumping force and
the depth of the weil. In working a common pump a man
can exert a pressure of only fifteen to twenty pounds
comfortably upon the pump handle, and as the power-arm
of the lever is only from five to seven times the length
of the weight-arm the weight of water which can be lifted
at one stroke cannot much exceed seventy-five to one hun-
dred pounds. This being true, it is evident that pumps
to be placed in deep wells must have smaller pistons than
those placed in shallow ones. It was shown in 88 that
the pressure of water is proportional to its depth, and in
89 that water forty feet deep exerts a pressure of two
thousand four hundred and ninety-six pounds per square
foot when at a temperature of 50° F., or at the rate of
seventeen and one-third pounds per square inch, and hence
the area of the piston for the pump to lift water forty
feet should not exceed

100

a 5.78 square inches,

and this is given when the diameter of the piston is 2.7

d8

inches. On account of the friction of the piston and of
the water in the pipe and of the inertia of the water, a
piston of that size would work hard in a well of that
depth. In a well where the water is to be raised only
twenty feet the area of the piston could be twice, and for
ten feet four times, as great respectively; these would be
given by diameters of 3.8 and 5.4 inches; but, as in the
first case, they are too large for easy action. Three inches
would be large for twenty feet.

103. Rate of Pumping. —The rate of discharge by a
pump will be governed by the area of the piston, the
length of the stroke and the number of strokes per minute.
If the area of the piston is five square inches, the length of
stroke five inches and the number of strokes per minute
forty, then

5 x 40 = 1,000 cubic inches

or 4.3 gallons per minute.

104. Function of Air Chambers.— In all single-act-
ing pumps the power is able to do useful. work on the
piston only when it is moving in one direction. In deep
wells, where a long column of water must be quickly set in
motion and then allowed to come to rest again, the intermit-
tent action of common pumps is a serious objection, and to
avoid this, air chambers are sometimes attached. The
principle of their action will be understood from a study of
Fig. 26.

The air in the upper portion of the chamber, which can-
not escape, is compressed by the rapid action of the piston
and then during the reverse movement, it gradually re-
gains its original volume, forcing the water out in a nearly
continuous stream. The water, therefore, is obliged to flow
with only one-half the velocity of that which would be re-
quired with no air chamber, and consequently a pump
having an air chamber properly placed can be worked by a
wind-mill in a lighter wind than one without the air chamber.
The air chamber attached commonly to pump stalks has no
influence on the pumping except when the pump is used to
force water above the level of the air chamber. To render
the greatest service, an’air chamber should be placed at as
low a point as practicable in the well where there will be
but a short column of water between the piston ‘and_-the
air chamber.

d9

LAL

SSS SpDOLGS9§ ws S

Eran

2

2 a

Fig.

60

105. The Siphon.—The flow of water through the
siphon 1s maintained by a force represented by the difference
in pressure in the two arms, the siphon being kept full by
atmospheric pressure. The action of the siphon is ex-
plained as follows:

|
iwi

LAGE
When the siphon is filled with water the downward
pressure in the short arm is due to the upward pressure
of the air at d, Fig. 27 and the downward pressure of the
column of water @ 6, which, using the values in the figure,
gives a total of :

2+ 2+ 14.72 = 18.72
The downward pressure in the long arm of the siphon is
equal to the downward pressure of the column of water ad
and the downward pressure of the air on the water in the
vessel, or

(6 x 2)+14.72=26.72. :

As the two air pressures are equal and in opposite direc-
tions they balance each other, leaving the force which de-
termines the flow the difference in the pressure of the two
columns of water, or °

12 -4=8.

It is evident that the greater the difference in the length
of the siphon arms the greater will be the velocity of dis-
charge. ;

106 The Flow of Water.—When liquids move in a
stream the molecules do not become separated from one an-

61

other to any appreciable extent. The stream moves as a
whole, the density of the liquid remaining the same in all
its parts.

The flow of fluids is caused by a difference of pressure
within the mass caused either by increasing it at some
point or by diminishing it at another. Small velocities
are associated with small differences of pressure and large
velocities with large differences.

107. “ Head of Water.’’—The velocity with which
water issues from an orifice in a vessel is due to the pres-
sure of the liquid above the center of figure of the orifice
and this distance is called the head. If it were not for the
viscosity of the water, and the resistance offered by the
orifice itself, the velocity would be equal to that which a
body falling in a vacuum would acquire in falling through
the distance equal to the head. This is expressed: by the
equation

Velocity= 4 /2gH

where H is the head and g is the velocity the force of
gravity is able to produce in a falling body during a second
of time and is equal to 32.2 feet. If the head is ten feet,
then the velocity of discharge, leaving resistance out of
consideration, would be

Velocity=| (2.x 82.2 x 10=25.3.

What would be the velocity of discharge with a head of
two feet? four feet? six feet? eight feet? twelve feet?

108. Flow of Water in Pipes.—The quantity of water
discharged by pipes is very much modified by their diam-
eters, lengths, degree of roughness, and by the presence
or absence of curves or angies. Other things being the

same, the greater the head the greater the discharge; the

greater the length and the less the diameter the less
the discharge; the greater the number of bends or angles
the less the discharge.

There is no simple rule for computing the amount of
water a pipe of a given length and diameter will discharge
under a given head. To compute the discharge exactly
the velocity of discharge at the mouth of the pipe and the
area of its openings are required. Where the pipes range
from .75 inch to six inches in diameter, and their lengths

62.

lie between two hundred and two thousand feet, the equa-
tions beluw give the velocity in feet per second, but with
only a rough degree of approximation.

fy aa tect —40,/diam. of pipe in fect x head in feet
per second Y length in feet + 54x diam. in feet.

This may also be expressed as below, the dimensions all
being in feet:

1600 x diam. pipe x head

9 haat =
(2) Square of velocity in feet per second length + 54 times diam.

In case the length of the pipe is twelve hundred to two
thousand times the diameter, the factor fifty-four times di-
ameter may be omitted without affecting the result very
much. -In such cases if the diameter and head are ex-
pressed in inches the velocities may be more readily de-
termined by the following: 7

1600 x diam. x head

OVS" 19 x 19 x length.

If the diameter of a pipe is two inches, its length two
hundred feet and the head four feet, what is the velocity
of discharge?

By (1), v=404/ seas 404/12 _--9,959,

By 2 9 LOQO ie Pe Ue 103:
y= O00 54 xk eee?
whence, v=2.259 ft. per second.
, 1600 x 2x 48
By (3), V=Te x 1D x 200 = 8333
whence, v=—2.309 ft. per second.

The last formula gives a velocity of .05 feet per second
too large.

What is the velocity of discharge when the diameter of
the pipe is six inches, length two thousand feet, head four
feet?

To find the discharge of water in cubic feet per second,

multiply the velocity in feet by the area of a cross-section
of the pipe in feet.

Discharge = velocity x area of opening.

HEAT.

EE

109. Nature of Heat.—Heat is a form of molecular en-
ergy. When a hot body is brought into contact with a
cold one, the molecules comprising the hot body have their
velocities slowed down by collision with the slower-moving
molecules of the cold body and energy is transferred from
the hot body to the cold one; and, if the contact continues,
the transfer will go on until the molecular energy, per
unit of weight, is equal in the two bodies. If a hot ball
of iron is allowed to cool in the air, the cooling is the re-
sult of the ball doing work on the air. The molecules of
air which come in contact with the surface of the ball are
struck by the molecules of the ball and made to move away
with a higher velocity than they had before, just as a
ball approaching a bat is struck by it and flies to field
leaving the bat motionless, a nearly complete transfer havy-
ing taken place. When a cold iron is thrust into the forge
fire a part of the energy of the molecules of the burning
coal and of the products of combustions is transferred, by
collisions, to the molecules of iron, and the temperature of
the iron rapidly runs up.

110. Solar Energy.—When the sun rises the tempera-
ture of bodies upon which it shines becomes higher as a
rule, and when it sets the temperature again falis, and, as
a rule, continues to do so until the sun begins to shine on
them again. So too, as our days grow longer and longer
with the.approach of summer, the mean daily temperature
becomes higher, and then falls away again as the nights
become longer than the days. Such, and many other facts,
prove that the sun is a source of energy, and that in some
manner this energy is being transferred to the earth.
Since the earth travels entirely around the sun once each
year, and yet each day receives energy from it, it follows
also that solar energy is leaving the sun continually in all
the directions in the plane of the earth’s orbit, and is in
fact traveling away in every other direction.

111. How Solar Energy Reaches the Earth. —When
one stands on the shore of a small lake and agitates its

64

waters in any manner, waves start out from the place of
disturbance, traveling in all directions toward the bottom
and the distant shore lines. When these waves reach the
bottom, the shore and the air resting upon the lake, they
lose a part of their energy, the lost portion being ¢trans-
ferred to whatever foreign medium is struck by them.
The energy generated in the muscles of the person agitat-
ing the water is thus conveyed away from him in all di-
rections, and, sooner or later, is changed into the energy
of molecular motion known as heat. The person is there-
fore a source of energy, which is borne away from him in
the form of waves in the water and air, and this wave en-
ergy becomes changed to heat, and thus the person in a
small degree warms the pebbles lying on the distant mar-
gin of the lake, not by the heat of his body, but by the
waves he set up in the water. It was not heat which
traveled to the distant shore, but water waves which,
striking the sands and pebbles, gave a part of their en-
ergy to be transformed into energy of heat in them.

The sun is wholly immersed in a cold medium called
ether and the molecules of the sun’s surface beating against
this have their energy transformed into waves in it which
travel away in all directions just as waves of water spread
away from a disturbing body in it, but at a very much
more rapid rate, the velocity being one hundred and eigh-
ty-six thousand six hundred and eighty miles per second,
a speed which brings them to us in about eight minutes
after their origin at the sun’s surface. Sir Wm. Thomp-
son estimates that the sun is constantly doing work upon the
ether at its surface at the rate of one hundred and thirty-
three thousand horse power for each square meter of its
surface, and the ‘‘mechanical value of a cubic mile of sun-
shine”’ near the earth is placed at twelve thousand and
fifty foot-pounds, and, as this energy is approaching us at
the rate of one hundred and eighty-six thousand six hun-
dred and eighty miles per second, the amount which falls
upon a square mile of the earth’s surface in that time is

186680 x 12050 ft.-lbs.=2249494000 ft.-lbs,

and this is equivalent to about eighty foot-pounds per square
foot each second.

112. Kinds of Ether Waves.—The molecular oscilla-
tions or vibrations at the sun’s surface are not all of them

65

at the same rate and hence they set up waves of different
frequencies of vibration in the ether, the slowest known
being at the rate of one hundred and seven billions of
thrusts upon the ether each second and the most rapid at
about the rate of forty thousand billions per second. When
the wave frequencies lie between three hundred and ninety-
two billions and seven hundred and fifty-seven billions per
second, such waves, falling in the eye, produce the sensation
of light and we speak of them as /ight waves. Waves slower
than three hundred and ninety-two billions per second pro-
duce no sensation of light in the eye, but when absorbed
by the skin they cause the sensation of warmth and are
called dark heat waves. Waves more rapid than seven
hundred and fifty-seven billions per second, when they fall
upon the molecules of a photographer’s plate, or upon a
living green leaf, set up such intense vibrations in these
inolecules as to break them down, producing chemical
changes and hence these are called chemical waves. It
should, however, be kept distinctly in mind that there is
no light, no heat and no chemical action until the ether
waves have dashed against some molecular shore and have
been wrecked upon it. When any of these waves fall upon
what we call a b/ack substance, like a thick layer of lamp-
black, they are nearly all absorbed and the body becomes
heated. On the other hand, when they fall upon a pure
white substance, like snow, the waves rebound with nearly
their full vigor and there is very little of either heating or
chemical effect. When the waves fall upon what we call
green substances, like the chlorphyl of growing leaves, most
of the chemical waves and a portion of the light waves are
wrecked by it and the chemical changes natural to grow-
ing leaves are the result.

113. Work Done on the Earth by the Ether Wayes. —

‘It was stated in 11] that eighty foot-pounds of energy per

square foot reach the earth’s surface each second, This
seems like an enormous amount of work when it is figured
in horse power for a section of land, the amount being

2249494000
Greg Was 4089989 horse power,

and it is difficult at first to realize that it can be true.
To comprehend the situation we need to know that the
earth is traveling through a cold region having a temper-

66.

ature of absolute zero, or —273° C., with only the thin
atmosphere to protect it from that cold. If the mean an-
nual temperature of Wisconsin is 45° F. or 7° C., its tem-
perature is maintained by the sun at

FI ee 7 OOO.

higher than that of the space which surrounds it. The
earth is therefore rapidly sending ether waves back again
into space, and thus a large part of the energy which
comes to us is lost. The motions of the air, and of the
water in the ocean and to and from the land, represent
other portions of this energy transformed. Most of the
chemical changes occurring in growing vegetation repre-
sent other transformations of solar energy, as do the ac-
tivities of all forms of animal life; and when to these are
added the chemical and physical changes in soils and
rocks, due to it, it is plain that the amount needed to
maintain the earth in its present state of activity is really
very large.

114. Transfer of Heat.— When one portion of a
body is heated, as in the case of a poker thrust into the
fire, the heat-energy gradually spreads to the distant end.
This sort of transfer is known as conduction, and the rate
at which it occurs is very different with different mate-
rials. Metals and stone are among the best conductors,
while wood, glass, water and woolen fabrics are among
the poor conductors. The transfer of heat through air,
where currents are prevented, takes place very slowly,
and it is on this account that several thin garments are
warmer than the same weight of the same material as a
single garment. It is on this account also that sawdust,
in the walls of buildings and about ice, is so serviceable.
Hollow walls with dead air spaces utilize the same princi-
ple. as does the practice of using one or more thicknesses
of building paper in the construction of buildings which
-are designed to keep heat in or out. .

When heat is applied to the lower portion of liquids or
gases the conduction of heat to portions of the mass causes
it to expand and become relatively lighter than that not
affected, and it is, in consequence, forced to rise, thus es-
tablishing upward and downward currents. In such cases
the heating is by conduction, but the heated mass is then
transported, that not heated taking its place. The process

67

is named convection. The third method of transfer of heat
is by radiation, and has already been described in ]]1.
115. Draught in Chimneys.—The draught in chimneys
is due to two principles, one that of convection, and the
w@— Other that of «aspiration. In all properly
constructed chimneys there is a draught,
usually, even when there is no difference
of temperature of air inside and out, and
such draughts are strongest when the wind
blows hardest. Why this is so will be
readily understood from Fig. 28. The air,
in its rapid motion across the top of the
chimney, encounters the air molecules in
its very top and forces them out and on-
ward with it; this diminishes the weight of
air in the chimney, and the pressure from
below forces a new quantity into the mov-
ing stream which in turn is driven away.
The rapid forward motion of the outer air
prevents it from descending into the space left by the air
forced forward. When the fire is kindled the air in the
chimney is made specifically lighter and is forced out on
the principle of flotation (91). When the temper ue of the

air is raised one degree F. its volume is increased i of its

fig 28.

original volume, so that if air enters a stove at 70° F. and
has its temperature raised to 234° F. its volume would be
increased one-third and hence its weight diminished in the
same proportion, and the relative weights of air per cubic
foot inside and outside the chimney would be as two to
three. When these conditions exist, it is evident that the
higher the chimney is the greater will be the difference in
the weight of the two columns of air and the stronger the
draught. When the chimney has its top considerably ex-
tended above the surface it is placed in a region of more
rapidly moving air currents and the draft is made stronger
on this account also.

116. Transparency to Ether Waves.— When the
hand is placed near a pane of glass, through which the sun
is shining, the ether waves falling upon the hand are ab-
sorbed and so increase the molecular motion of the skin,
raising its temperature. The hand, in turn, sends out
ether waves toward the sun, but they are of the long sort

68

and cannot pass through the glass, but are reflected back
again upon the hand and join with those coming from the
sun to raise the temperature to a still higher point. The
glass is transparent to the short waves coming from the
sun but opaque to the long ones into which they have been
transformed in the hand.

This is the principle upon which the hot-bed is
constructed, which is practically an energy trap, allow-
ing it to enter from the sun and then preventing its ready
escape.

On the same principle, too, large windows in the south
side of dwelling-houses, especially if they are double, con-
tribute a very large amount of heat toward warming the
room in winter, and are really a great saving of fuel, be-
sides contributing so much to healthfulness. The amount
of heat which may enter a house in this manner during the
winter is much larger than can enter it in summer, be-
cause in winter the sun shines more perpendicularly upon
the windows, which has the effect of making them larger,
as explained in 1 ee

Our atmosphere acts practically in the same manner to-
ward the energy received from the sun and that radiated
back again by the earth. It is highly transparent to the
first and very opaque to the last. Clouds, fog and smoke
are still more opaque to terrestrial radiations, and this is
why frosts on a cranberry marsh or strawberry bed may
sometimes be prevented by producing a cloud of smoke
over it.

117. Temperature.— The temperature of a molecule is
an expression of the amount of energy it contains, and all
molecules having the same temperatures are assumed to
possess the same amounts of energy of motion. When the tem-
perature of a given body is doubled its energy of molecular
motion is doubled. Could the molecules of a body be brought
entirely to rest, its temperature wouid be absolute zero, but
this is a condition of things very difficult if not practically
impossible to reach. é

118. Measurement of Temperature.— The common
method of measuring temperature is by noting the changes
in volume of a body which are associated with changes in
its temperature. The material of a thermometer may be
either solid, liquid or gaseous, and all three types are in
use. For ordinary purposes the mercurial thermometers

69

are the best. The mercury expands more regularly than
most other available liquids, thus making the graduation
of the stem simple; it boils at a high and freezes at a low
temperature ; it can be readily seen and it responds quickly.

The sensitiveness of the thermometer depends upon the
relative diameters of the bulb and tube; the finer the bore
of the tube and the larger the bulb the longer will be each
degree. Too large a bulb is objectionable because a longer
time is required for it to acquire the temperature of the
body whose temperature is desired, and too fine a bore has
the objection of not being readily seen. The long cylin-
drical, bulbs are better than the spherical ones because
they present a larger surface and therefore respond more
quickly, reaching a condition of rest sooner.

119. Testing a Thermometer.— The bulbs of most
thermometers shrink after they are made, and if the grad-
uation has been done before the shrinkage has occurred
the reading of the thermometer will be found too high or
will ultimately become so. To see whether the thermom-
eter is correct, in this regard, it should be immersed in
melting snow or crushed ice, from which the water formed
by melting may readily drain away, and allowed to re-
main until the mercury becomes Stationary.

If the thermometer is one of the dairy types, or has the
bulb exposed, its correctness at blood heat may be deter-
mined by placing the bulb under the tongue and keeping
the mouth closed over it for ‘about one minute, reading the
temperature while the bulb is yet in the mouth. If the
person is well the thermometer should indicate about
98. 8° F.

It is rarely true that the diameter of the tube of the
thermometer stem is uniform throughout, there being a
general tendency for the diameter to increase from one
end to the other. If the irregularity, of the tube is large,
it may be correct at the freezing and boiling points and
yet incorrect at intermediate points. If the tube grows
larger from the bulb the same amount of expansion in the
bulb will cover a shorter distance on the scale, and vice
versa. Large inequalities in the tube may be detected by
jarring the thermometer so as to Separate a short column
of the mercury, say three-fourths of an inch, and carefully
measuring its length by divisions of the scale in different
portions of the stem; if there is a large variation the

70

length of the column separated will vary as it is moved
from place to place.

120. Kinds of Thermometer Seales.—There are two
scales used in this country, the Fahrenheit and Centigrade.
The first places the freezing point of water at 32°, and the
boiling point at 212°, the second at 0° and 100° respect-
ively. The Fahrenheit scale, between 32° and 212°, is
divided into one hundred and eighty divisions called de-
grees, while for the Centigrade scale the number of divis-
ions is just one hundred. This being true,

180° Fahr.= 100 Centigrade.

oon Si0Ge 15%
Sosa Soe
and 1 C=100=5 F,

To convert the readings of a Fahrenheit scale into Centi-
grade degrees find the number of Fahrenheit degrees from
the freezing point and multiply this by ¢.

: 5)
No. of degrees F. from freezing Xg=No. degrees C.
To convert Centigrade degrees into degrees Fahrenheit
multiply the number of degrees by 3 and the result will
be the number of degrees F. above or below 32° F.

No. of degrees C. xS=N o. of degrees F.. above or below 32° F.

121. The Heat Unit.—It requires sixteen times as
much heat to raise the temperature of a pound of hydrogen
one degree as it does a pound of oxygen, and other ratios
are found to exist when other substances are taken. This
makes it necessary to select a certain substance as a stand-
ard when a unit of heat is desired. Wdter is taken as the
standard and one heat unit is the amount necessary to
raise a pound of water from 32° F. to 33° F.

122. Specific Heat.—When the amount of heat which
will raise the temperature of a pound of water from. 322°".
to 33° F. is applied to a pound of dry sand it will have
its temperature raised through about 10° F. (Oelmer), or
the same heat would raise the temperature of ten pounds

71

of sand one degree, and the specific heat of sand is said to
be .1, that of water being 1. With the exception of hy-
drogen, water possesses the highest specific heat known,
and this means that it warms more slowly than do other
substances; but the reverse is also true, and when once
heated it cools more slowly or gives out a larger amount
of heat. This is why large bodies of water make the
winters of the lands adjacent to them warmer and the
summers cooler.

123. The Specific Heat of Soils.—Different soils, like
other substances, have different specific heats, and hence
warm at different rates under the same sunshine, and it is
on account of this fact, in part, that one soil is warmer
than another. In the following table are given the number
of heat units necessary to heat one hundred pounds of water
and of varieties of soils from 32° to 33° F., and the tem-
perature each would have after one Hennes heat units had
been applied to them at a temperature of 32° F,

TABLE OF SPECIFIC HEAT OF Dry SOILs.
No. ofheat units re- Temperature of 100

quired to raise ibs. after the ap-
100 ibs. from 32° plication of 100
F. to 338° F. heat units.
Heat units. Degrees F.
WOT Dh bee tenis alta 100.00 33.00
MoGGr eARpie oo.) suk 22.15 36.51
POS eS RG ye a's o-3 20.86 36.79
Sandy humus......... 14.14 7 39 .07
Loam rich in humus.. 16.62 38 .02
Clayey humus ....... 1 at9 a8 .a0
LST 00S gegen teen ieee aa ana 14.96 38.65
PUES GlaAy sos. dea os. 4 Bis ea fo ame 39.28
SEN NCU Sa ear ieee aa 10.08 41.92

Pure eae Spee at ahs 18.48 37.41

These figures do not, in themselves, indicate the actual
differences in temperature the several soils named would
show under natural conditions because they are not only
never perfectly dry but they have different capacities for
holding water, and they differ also in their specific gravi-
ties, so that one hundred pounds of one soil covers more
surface, at a given depth, than another one does. We
have not yet the data needed for an exact comparison, by
volume, of the specific heat of soils. The higher the per
cent. of water any soil contains the more heat will be re-

wi?)

(a

quired to raise its temperature one degree; so, too, the
heavier the soil is per cubic foot the more heat will be re-
quired to raise its temperature a given number of degrees.
Sand has a less capacity for water than most other soils
and is, on-this account, naturally warmer, yet its higher
specific gravity tends to make it colder than other soils. A
cubic foot of dry sand weighs about one hundred and six
pounds, while one of clay loam is only about seventy
pounds. Saturated sand will contain, in the field, only
about eighteen per cent. of water, while the clay loam may
have as high as thirty-three per cent. Below are given the
number of degrees one hundred heat units will raise the
temperature of a cubic foot of sand and of clay :oam when
each is saturated with water, half saturated and dry

Saturated. Half saturated. Dry.
3.4° 2° F

iad eld ke Pe se ee oak 7) IB 9,92° FP.
lay loam: soe Se eet ” 998° F 449° F. 6.02° F.
Pitter anced ewe 49° B 51° F. 39° F

It is thus seen that the greater weight of the sand, per
unit volume, tends to offset the greater amount of water
held by the clay, giving the two a more nearly equal tem-
perature than they would otherwise possess. It will also
be seen that the difference in the per cent. of moisture a
soil may contain makes a relatively larger difference in the
change in temperature a given amount of heat absorbed
will produce. This is one reason why a well-drained soil
is warmer than a similar one not so drained.

124. ** Latent Heat.’’— When heat is applied to ice
at a temperature of 32° F., its temperature does not rise
until the melting is completed, the whole energy applied
being expended upon the molecules in moving them into
new relative positions against the force of cohesion which
binds them together in the crystalline arrangement of the
ice. The amount of heat required to melt a pound of ice
whose temperature is 32° F. is, in round numbers, one
hundred and forty-two units, or enough to raise the tem-
perature of one hundred and forty-two pounds of water
from 32° to 33° F. This fact may be demonstrated approx-
imately as follows:

Take equal weights of water at 32° F. and at 212° F. and
mix them. The two weights of water will then be found
to possess a temperature nearly equal to

If, on the other hand, equal weights of water at 2120 F.
and dry ice at 32° are placed together and the ice allowed
to melt, the resulting water will be found to have a tem-
perature of 51° F, The water has had its temperature
lowered

ai2°—5)°=-161" F.
while the ice has had its temperature raised only

ob“ 32 -=19° BF.
Now if one pound each of ice and water were taken for the
experiment it is evident that the number of heat units
consumed in melting the ice would be

161—19=142 heat units.

When water has been raised to the boiling point no fur-
ther increase of temperature can be effected so long as the
pressure upon it remains constant, the whole amount of
heat energy being now expended in converting the water
into steam at the same temperature.

If a pound of steam at 212° F. be condensed in DST
pounds of water at 32° F. there will then be 6.37 pounds
of water having a temperature of nearly 212° F. The
pound of steam in being converted into water has heated
9.37 pounds of water through

212°— 32°=180° F.
without having its temperature appreciably lowered. The

molecular energy of the one pound of steam which was ab-
sorbed by the 5.37 pound of water was therefore

180 x 5.357=966.6 heat units.

This large amount of molecular energy in steam explains
why a scald from steam _is so much more severe than one
from boiling water, and also why so small a quantity of
steam, by weight, is required to cook a barrel of potatoes
or feed.

125, Evaporation Cools the Soil.— We have seen that
one pound of steam in condensing into water generates
966.6 heat units, and the reverse statement is also true,
namely, to convert a pound of water into the gaseous
state, under the mean atmospheric pressure, requires the
absorption by that pound of 966.6 heat units. When one

74

pound of water disappears from a cubic foot of soil by
evaporation, it carries with it heat enough to lower its
temperature, if saturated sand, 32.8° F.; and if saturated
clay loam, 28.8° F.

To dry saturated sandy soil until it contains one-half of
its maximum amount of water requires the evaporation of
about 9.5 pounds to the square foot of soil surface when
this drying extends to a depth of one foot, while the simi-
lar drying of clay loam requires the evaporation of 11.5
pounds, and

11.5—9.5=2 lbs.

or the amount of Lae which must take place in the
clay loam to bring it to the same degree of dryness as the
sandy soil. But to evaporate two pounds of water re-
quires

966.6 x 2=1933.2 heat units,

and this, if withdrawn directly from a cubic foot of satu-
rated clay loam, would lower its temperature 57.6° F.
Here is one of the chief reasons why a wet soil is cold.

That the evaporation of water from a body does lower
its temperature may be easily proved by covering the bulb
of a thermometer with a close fitting layer of eS y muslin,
noting the temperature. If the muslin be now wet,
with aratee having the temperature noted, and the thos’
mometer rapidly whirled in a drying atmosphere its tem-
perature will rapidly fall, owing to the withdrawal of heat.
from the bulb by the ev aporation of water from the muslin.

126. Regulation of Animal Temperatures.— All of
our domestic animals require the internal temperature of
their bodies to be maintained constantly at a point vary-
ing only a little from 100° F., and this necessity requires
provisions both for heating the body and cooling it. The
cooling of the body is accomplished by the evaporation of
perspiration from the skin, and the amount of perspiration
is under the control of the nervous system. When the
temperature becomes too high, because of increased action
on the part of the animal, or in consequence of a high ex-
ternal temperature, the sweat glands are stimulated to
greater action and water is poured out upon the evaporat-
ing surfaces and the surplus heat is rapidly carried away;
each pound evaporated by heat from the animal withdraw-
ing about 966.6 heat units.

79

127. Bad Effects of Cold Rains and Wet Snows on
Domestic Animals.—When cattle, horses and sheep are
left out in the cold rains of our climate the evaporation of
the large amount of water which lodges upon the bodies,
and especially in the long wool of sheep, creates a great
demand upon the animals to evaporate this water. The
theoretical fuel value of one pound of beef fat is 16,331 heat
units, and that of average milk is 1,148 heat units. A
pound of beef fat may therefore evaporate

16331
966 .6
aud a pound of average ecow’s milk

=16.8 lbs. of water,

1143 =1.18 lbs. of water.

966 .6

On this basis, if a cow evaporates from her body four
pounds of rain she must expend the equivalent of the solids
of 3.39 pounds of milk.

A wet snow-storm is often worse for animals to be out in
than a rain storm, because in this case, the snow requires
melting as well as evaporating, and the number of heat
units per pound of snow is

142.65 + 966.6 =1109.25 heat units,

and the heat value of a pound of milk is barely sufficient
to meit and evaporate a pound of snow.
128. Cooling Milk with Ice and with Cold Water. —
Tf it is desired to cool one hundred pounds of milk fron 80°
F. down to 40° F. it is practically impossible to do
so with water in the summer season in Wisconsin. It is
difficult even to cool it as low as 48° F., for most of the
well and spring water has a temperature above 45 and
much of it is above 50° F. If lower temperatures than 48°
F. are desired during the warm season some other means
must be resorted to. Since it requires one hundred and
forty-two heat units to melt a pound of ice, one pound is
capable of cooling from 80° to 40° F.
1424+8
40

supposing the specific heat of milk to be the same as that
of water, which is not quite true. To cool one hundred

=3.75 lbs. of milk,

76

pounds of milk from 80° F. to 40° F. will require, there-
fore, about
100
3.75
supposing it to be used wholly in cooling the milk.

If the water has a temperature above 40° F. before the
milk and ice are placed in it, there will be required enough
more ice to cool the water down to the temperature desired
for the milk.

The greatest economy in the use of ice will be secured,
therefore, when the creamer contains just as little water
as will cover the cans and give the reedéd space for the
ice, and when the walls of the creamer are made of so poor
a conductor of heat as to admit as little as possible from
without.

129. Washing with Snow or Ice.—When ice or snow
are used in winter for washing purposes there is a large
loss of heat incurred in simply melting the ice and raising
the temperature of the water from 32° F. up to 45° F., the
temperature it may have in any well protected cistern.
To melt a pound of ice and raise its temperature to 45° F.
will require

=262 lbs. of ice,

142+-138=155 heat units.

If three hundred pounds of water are required for a
washing then the lost heat will be

300 x 155=46500 heat units.

The fuel value of one pound of water-free, non-resinous
wood, such as oak or maple, has been found to be 15,873
heat units; that of ordinarily dry wood, not sheltered,
containing 20 per cent. of water, is 12,272 heat units. At
this latter value it will require, supposing 50 per cent. of
the fuel value to be utilized in melting the ice and _ heat-
ing the water,

~

2 x 46500

—19979 =7.58 Ibs. of wood.

more than would be needed to do the same washing with
water at 45° F.; and if seventeen such washings are done
during the winter the total cost for fuel would be the
value of

17 x 7.58=128 lbs. of wood.

77

to say nothing of the expense of getting the snow or ice
and the unhealthfulness of handling it.

130. Burning Green or Wet Wood.—Whatever water,
wood or other fuel may contain when it is placed in the
stove, so much of the fuel as is required to evaporate this
water must be so expended and is prevented from doing
work outside of the stove. We have seen, 129, that when
wood contains 20 per cent. of water there is required

15873—12272=3601 heat units

per pound of wood to evaporate the water contained, which
is 22.7 per cent. of the total value. Wood, after being in
a rain of several days, contains more water than this,
and green wood much more, sometimes as high as 50 per
cent., while well-seasoned sheltered wood may contain less
than half that amount.

It is frequently urged that when some green or wet wood
is burned with that which is dry there is a saving of fuel.
There is some truth in this, especially in stoves having too
strong a draught and too direct a connection with the
chimney and if the radiating surface is small or poor. The
evaporation of the water prevents so high a temperature
from occurring in the stove, which makes the draught less
strong, and this gives more time for the heat to escape
from the stove before reaching the chimney, and hence
less is lost in this way. Then as the fire burns more
slowly there is not the overheating of the stove, at times,
which may occur with lack of care when very dry wood is
used, and a considerable saving occurs in this way. These
statements apply more particularly to heating stoves than
to cooking stoves. Dry wood is best for the kitchen stove
under most circumstances, the slower fire being secured
when needed by using larger sticks and by controlling the
draft:

131. High W inter Temperatures Associated with
Snow Storms.— ‘It is too cold to snow” is a common say-
ing, but the truth is it cannot snow and remain very cold.
Speaking in approximate terms, when a pound of w ater in
the form of aqueous vapor in the air is converted into
snow there is liberated

966.6 + 142—1108.6 heat units,

and, as the specific heat of dry air is only .2375, one heat’
unit will raise the temperature of one pound of air through

and 4.21 pounds of air through 1° F. This being true,
the freezing of one pound of aqueous vapor will liberate
heat enough to warm through 1° F.

1108.6 x 4.21 pounds=4667.2 pounds of air,

and as water at 32° F. is 773.2 times heavier than air at
the same temperature, the number of cubic feet of air raised
el AMUSsb. be

4667.2

62.417

173.2
which is equivalent to 5781.56 cubic feet raised 10° and
to 1806 cubic feet raised from 0° F. to 32° F. When a
snow fall of four to six inches occurs, over a large area,
there is, therefore, a very large volume of air heated by it.

= 57815.6 cu. ft. of air,

PROTECTION AGAINST LIGHTNING.

132. Nature of Electricity.—No very clear statement
is yet possible in regard to the real nature of either elec-
tricity or magnetism, but the strongest evidence points
to the conclusion that they are manifestations due to some
action of the all-pervading ether which we have seen, 1B ig
is the medium through which energy generated at the sun’s
surface reaches the earth. In the battery, on the telegraph
line, energy is generated by the chemical action there tak-
ing place and, by some action not vet clearly seen. the
ether pervading the space between and surrounding the
molecules of the telegraph wire conveys this energy to the
distant stations, where it is absorbed by the receiving in-
struments and converted into mechanical motions which
record or indicate the messages sent. In some manner
the molecules of a conducting wire prevent the escape of
energy to the outside ether as the walls of a speaking tube
confine the sound waves developed in them, preventing
them from being dissipated in the Surrounding air and al-
lowing them to travel to the end only slightly enfeebled.

When a glass rod is rubbed with a piece of silk or fur
the mechanical action develops a state in the ether of the
rod which is shown by the ability of the rod, in this con-
dition, to attract light objects to it. When a person
Speaks in front of a telephone the sound waves produced
by the vibration of his vocal cords set the metal plate,
near the end of the telephone magnet, swinging in unison
with the vocal cords, and the approaches and recessions of
this plate so disturb the ether of the magnet as to cause
it to take up a part of the energy of the vibrating plate
and then to transmit it to the ether of the wire wrapped
about the magnet and leading to the receiving station,
where, by another of those wonderful yet universal trans-
formations of energy, the action is reversed and the me-
chanical swing of the plate in the receiving telephone
gives back the words which set up the action at the send-
ing station.

80

133. Atmospheric Electricity.— What the origin is of
the intense electrical manifestations associated with thunder
storms as yet lacks positive demonstration, but the close
resemblances of these manifestations to the electrical man-
ifestations developed by friction, when combined with the
fact that the strongest atmospheric electrical displays are
associated with the most violent air movements where
rain or hail is present, has led to a general belief that
this electricity owes its origin to the friction of the air
currents upon the condensed moisture they are carrying.
Fig. 29 represents the general character of an electrical
discharge in the atmosphere.

Fig. 29.

154. Electrical Induetion.— When a body, which has
become charged with electricity, is brought near another
body which has not been electrified it exerts an influence
upon that body inducing electricity in it, and if the charge
is sufficiently intense and the distance is not too great the
electricity will break across from one body to the other,
and the act may be accompanied by a flash of light and a
report.

81

135. Positive and Negative Electricity.— It is im-
possible to throw a stone into water, making a depression
at any point, without raising a ridge around it which is equal
in magnitude to the depression, but extending in the op-
posite direction. When these two opposite phases are de-
veloped they tend to come together, and the tendency is-
stronger in proportion as the waves are higher. Somer
thing analogous to this state of things seems to occure
whenever and wherever electricity is generated. There
appears always to be engendered two equal and opposite
phases which tend to run together and obliterate each
other unless prevented from doing so. The one phase is
called positive and the other negative electricity.

136. Conductors and Non-conductors of E lecric-
ity.—There is a great difference in the ability of different
substances to convey electricity from one place to another ;
those which convey electricity readily are called conduct-
ors, and those which convey it poorly or not at all are
called poor conductors or non-conductors. The metals
generally are among the best conductors, and silver and
copper are the best of these. Glass, gutta percha and
dry air are among the poorest conductors.

137. Discharges from a Point.— When a body be-
comes charged with electricity the charge manifests itself
only on the outside surface. If the body is a sphere the
intensity of the charge will be uniform at all por-
tions of the surface. If, however, the body is conical or
has points upon it the charge will be most intense at the
points, and if a discharge takes place it will occur first
from the points, and it is this fact which has led to the
placing of points on lightning rods.

138. When an Object May be Struck by Lightning.—
When a cloud becomes so heavily charged that the air be-
tween it and an adjacent cloud or an object on the ground,
in which it has induced the opposite kind of electricity, is
no longer able to prevent the electricity from breaking
through, a discharge or stroke occurs. Usually the nearer
the charged cloud approaches an object the more intense
will be the charge induced by the cloud in the body ap-
proached and the greater will be the chances of a stroke.
The intensity of attraction increases as the square of the
distance decreases, and this is why, when other conditions

82

are the same, elevated objects, like buildings, are more
liable to a stroke than those which are lower.

Buildings standing upon wet ground are more liable to a
stroke than buildings in other respects similar but stand-
ing upon dry ground, the greater danger coming from the
possibility of a stronger charge being induced upon the
house in consequence of the better conduction of the wet
soil. Large trees near buildings have a tendency to pre-
vent strokes.

139. The Function of a Lightning-rod.— Lightning-
rods have two functions to perform, the first and chief one
being to discharge quietly into the air above, the electric-
ity which may be induced upon a building as rapidly as it
accumulates, and thus prevent a stroke from occurring; and
second, in case a stroke is inevitable, to diminish its in-
tensity and convey to the ground quietly as much of the
discharge as possible, thus reducing the damage to a
minimum,

140. Do Lightning-rods Afford Complete Protec-
tion ?2— There is now a general agreement among physicists
that properly constructed and mounted lightning-rods fur-
nish a large protection to buildings; they are divided in
opinion, however, as to whether complete protection is
possible. The rod may be called upon to protect against
discharges under two conditions: first, where a_heavily-
charged cloud comes siowly over the rod, giving it time to
discharge the induced electricity and thus prevent an ac-
cumulation; and second, where an uncharged cloud chances
to be over a rod when it instantaneously becomes charged
from some other cloud. When this occurs it is claimed by
some that the rod has insufficient time to afford any mate-
rial protection, and hence that it is hopeless to think of
protecting completely against this class of cases.

141. Essential Features of a Lightning-rod.-—For a
number of years past there has been a fairly unanimous
agreement in regard to the essential points of a light-
-ning-rod but some new discoveries in regard to the con-
duction, of rapidly alternating currents, and in regard to
electrical inertia, has led to a divergence again upon some
points. It may be said that practically all are agreed
that:

1. The rod should be of good conducting material, contin-

83

uous throughout, terminating in several points above, and
well connected with permanent moisture below the struct-
ure in the ground.

2. The rod should be in good connection with the building,
especially with metal roof and gutters, and should be carried
as high as the highest point of the structure to be protected.

3. The points need not be very fine, but should be coated
with some metal which will not rust,

4, An iron rod, everything considered, is better and
cheaper than one of copper, provided it is galvanized and
of sufficient size.

The fundamental point of disagreement at present is in
regard to the form of the rod; some claiming that, if a suffi-
cient area of cross-section is given the shape is immaterial so
far as conducting ability is concerned, the solid round rod
being the cheapest and most easily protected from rust;
others maintain that the larger the surface the rod pre-
sents the greater will be its conducting power and that
the flat ribbon is the cheapest and best.

The first view is founded on the fact that, for steady
currents, the conducting power is directly proportional to
the area of the cross-section. The second view is founded
upon what now appears to be the fact that very rapidly
alternating currents travel only through an extremely thin
layer of the surface of the conductor, and what also ap-
pears to be the fact, that lightning discharges are a series
of extremely rapid alternating currents. The settling of
this point of dispute is likely to require the testimony of
actual and extended practical tests with both forms of rods.

142. Danger to Stock from Wire Fences.— The in-
troduction of wire fences has to some extent increased the
danger from lightning to stock in pastures, owing to the
tendency of the wires to become charged and then give off
side sparks to the animals standing near. The danger is
less from the barbed wire than from the plain, and the
danger from both may be lessened by connecting the sev-
eral wires with the ground by means of other wires tacked
to the sides of the posts, the lower end being turned un-
der the point of the post when set. The staples should be
driven astride the two wires so as to hold them in close
contact. It is not possible to say just how close together
these discharging wires should be placed, but probably not
nearer than 15 to 20 rods.

SOT PHYSICS:

143. Nature of Soil.— The basis of all soil consists of
the undissolved remnants of the underlying rocks. Asso-
ciated with these remnants there is always a varying per
cent. of organic matter, resulting from the decay of vege-
table and animal remains; a certain amount of dust par-
ticles brought from varying distances by the winds, or
washed down by rain-drops and snowflakes which have
formed about those floating high above the earth’s sur-
face; and a considerable amount of saline substances
brought constantly to the surface by the upward move-
ment of capillary water, and left deposited when the water
evaporates.

144. Origin of Soil.—Al1l soils owe their origin to the
processes and agencies of rock destruction which have
been and still are taking place in three chief ways:

1. Many rocks have been mechanically broken into
larger or smaller fragments.

2. Other rocks have had their molecules separated by
simple solution as salt is dissolved by water, or the mole-
cules have first been changed chemically and then dis-
solved. .

3. Still other rocks have had some of their mineral con-
stituents dissolved out, leaving the remainder as an inco-
herent mass of fragments. In Fig. 30 are shown the stages
of transition from the underlyiug rock to the soil above as

‘
S
Ss Pa 5
rt

es

Ze
Vs:

r:

: is

% A

Sass

ao =

Fig. 30.
it occurs on limestone hills, while Fig. 31 shows the same
facts for a more level limestone surface. On examining

Pe 2

85

the rocks of almost any quarry they are found to be di-
vided into blocks of varying sizes by fissures or breaks

Fig. 31.
which owe their origin to a general shrinkage of the rocks
and to movements of the earth’s surface layers. These are
the first steps in soil formation, and are plainly shown in.
Figs. 32 and 33. They exert a great influence in rock
destruction and soil formation by furnishing easy access
for water and the roots of trees to their interior, where
the first by freezing and the second by growth expand and
break the blocks into smaller fragments. Moving ice, in
the form of glaciers, has done a vast amount of rock orind-
ing, the present soil of all except the southwestern portion
of our own state being the altered surface of a thick man-
tle of boulders, gravel, sand and clay formed, transported

Fig. 32. Fig. 38.

Fort Danger, Wis. Froma Photograph. Bee Bluff, Wis. From a Photograph, After

After Chamberlin, Chamberlin.

86

and spread out by glacial action and the waters from the
melting ice. Then there are many animals which have
contributed largely to
this rock grinding and
soil formation. Dar-
win, through a long
and careful study,
reached the conclusion
that in many parts of
England earth-worms
pass more than 10
tons of dry earth per
acre through their
bodies annually, and
that the grains _ of
sand and bits of flint
in these earths are
partially worn to fine
silt by the muscular
action of the gizzards
of these animals: this
Same work is going
on in our own soils,
where the holes bored ;
by angleworms repre- Fig. $4,

sent the volume of A tower-like casting ejected by a species 0 Dai

T r — worm, from the Botanic Garden, Calcutta: o
dirt they have passed natural size, engraved from a_ photograph.
through their bodies. After Darwin.

All seed- eating birds take into their gizzards and wear
out annually large quantities of sand and gravel, after
the manner of our domestic fowls.

The other two methods of soil formation depend mainly,
though not wholly, upon chemical changes wrought in the
rock minerals. Pure water has the power to dissolve,
without chemical change, greater or less quantities of most
rock minerals which are brought to the surface by capil-
lary action and become fine grains in the surface soil; but
the larger part of this work is brought about by the ac-

ion of “water in conjunction with oxygen, carbonic, nitric,
sulphuric, humic and other acids which it carries down

into the rocks where the work of solution goes on rapidly.
Mr T. M. Reade has estimated that the Mississippi alone
carries to the sea annually 150,000,000 tons of rock in so-

87

lution, and yet a large part of the water which enters the
soil is brought back again to the surface and evaporated,
leaving the materials it has dissolved as a contribution to
agriculture.

145. Soil-conveetion.— On the surface of a lake the
water which is at the top one moment is at another below
the surface, the molecules changing position continually
by convection currents due to changes of temperature.
There is a movement somewhat analogous to this taking
place in every fertile soil, though the movements are less

PANVEAY
aldo

seultwiaelilyneavabte devi ze
NG ale IU He

Yj YY

Fig. 36,
Section reduced to half natural scale, of the vegetable mould in a field drained anfl
reclaimed 15 years before. Showing turf, vegetable mould without stones,

eu with fragments of burnt mar], coal cinders and quartz pebbles. After
arwin.

rapid and are due to different causes. Earth-woxms, ants,
crayfish, gophers and various other burrowing animals
each season bring large amounts of the finer portions of
the lower soil and subsoil to the surface, forming systems
of galleries with openings leading out to the free air at

88

various places. Each heavy rain, especially during the
fall and spring, washes the finer cone soil into these
galleries, filling them up, and new excavations are again
made, thus keeping up a slow, but nevertheless a bertain
penuiation: which in some of its effects is like the fall and
spring plowing, but much of it extending to far greater
depths, the angleworms, ants and crayfish often going
down from fleck to five or more feet during dry seasons.
Darwin’s, observations have shown that thi rotation of
soil, which he attributes largely to the action of earth-
worms, tends to bury coarse objects, like flints, lying on
the surface, as time passes, and in Fig. 35 is represented
one of these cases as cited by him,

146. Soil Removal.—Pitted against these processes of
growth there is a powerful and universal set of agencies
constantly operating everywhere to transport from ‘higher
to lower levels and ret the land to the sea the eurfuce
soils, and the magnitude of bn action has been estimated
at not far from one foot each 3,000 years as an average
for the whole land surface, and] hence the superficial and ex-
hausted soils are being slowly removed and replaced by
new soil originating from the products of rock decay,
and brought to the surface by capillary action and that of
burrowing animals generally. The absolute amount of soil
removal can be appreciated when it is understood that the
summits of the bluffs represented in Figs. 36 and 37 show

the general level of the surrounding lower land at a former .

time and that, at times intervening between the present
and that earlier period, vegetation has grown on soils oe-
cupying all the levels between the two shown in the en-
eravings.

147. Surface Soil.— Soils proper comprise the sur-
face five to ten inches of fields and woodlands generally.
Oftentimes the depth of the true soil may be less than five
inches, and then again it may exceed a depth of ten inches
by varying amounts. It is the portion which has been
longest and most completely exposed to the disintegrating
and solvent action of rock-destroying agencies, and as a
result of this fact it contains a smaller per cent. of the
soluble minerals used by plants than the less altered sub-
soil below. Its chief ingredients are: -

1. Sand. )

2. Clay.

Composing about 90 to 95 per ct. of the dry weight;
3. Humus. \

89

which are commingled in varying proportions, giving rise
to different varieties according as one or another of these
ingredients predominates. The true soil, on account of
its more complete aeration and its higher temperature,. is
the chief laboratory in which the nitrogen compounds for
plant food ‘are elaborated.

Giant’s Castle, near Campo Douglass, Wis. Pillar Rock, Wis. From a Photograph.
From a Photograph. After Chamberlin. After Chamberlin.

148. Kinds of Surface Soil.—For practical purposes
soils are variously classified. When reference is had to
the ease or dilticulty of working the soil it is spoken of as

1. Light, or
2. Heavy;

: but these terms have no significance as regards actual
weights; for a sandy soil is spoken of as light, and yet it
is the heaviest of all soils, bulk for bulk. The greater
weight of the sandy soil is due more to the lack of large cav-
ities which are found in the clayey soils, than to the higher
Specific gravity of the soil constituents. It is the greater

90

adhesiveness of the clayey soils which causes the plow, hoe
or harrow to move with greater difficulty through them.
When reference is made to the temperature of soils, at
the same season, they are spoken of as
1. Warm, or
a. Cold.
according as the temperature of the soil is relatively high
or low. In this case the soils containing the greatest amount
of water are, when other conditions are similar, the colder
on account of the high specific heat, 123, of the water.
When the chief ingredients of soil are the basis of dis-
tinction they are frequently classified as :

Sand. Clay. Humus.

Pencent. Percent. Per cent.
1. Sandy soil, containing.......... 80 to 90 8 to 10 1t03
2. Sandy loam, pebued Dae OA Ee 60 to 80 10 to 25 3 to 6
3. Loam, te RE rt Ase ee 25 to 60 25 to 60 3 to 8
Aa OV, TORR: Sie a nie oe arate 10 to 25 ~=60 to 80 3 to 8
5. Clayey soil, FE Paaaiitr, Sat Sale hte 8to15 80'to 90 3 to 6

In peaty soils, or those of our low marshes and swamps,
there is often as high as 22 to 30 per cent. of humus. It
should be kept in mind that the sand, clay and humus of
soils are not plant food proper except in a small degree;
they are, except a part of the humus, what is left after
the plant food is removed. They serve, however, an im-
portant purpose in furnishing a proper feeding ground for
the roots and a means of supporting plants in their up-
right attitude.

149. Subsoil.— The subsoil is the real source of the
natural mineral constituents of plant food, while at the
same time it acts as a reservoir for water which is deliv-
ered at the surface by capillary action or held within its
mass until the penetrating roots remove it. The depth to
which roots penetrate the subsoil is really great, and I
believe the depth is determined primarily by the water
content of the soil, the roots traveling farther when the
supply is scanty. Wheat roots are recorded as observed
at a depth of seven feet in Rhenish subsoil of a sandy
loam. Corn roots with us commonly reach a depth of
three feet and often exceed four. It would appear, there-
fore, aside from the fact that the subsoil is the parent of
the true soil and that it acts as a water reservoir, that
the chemical composition and physical characters of the

91

subsoil may determine in a large measure the productive-
ness of land, unless it should be determined by future in-
vestigations that the deep-running roots are simply water-
gatherers,

150. Variation in Composition of Subsoils.— There
is a marked difference in the composition of those subsoils
of Wisconsin which are simply the residuary products of
the decay of rocks in place, such as those represented in
Figs. 30 and 31, and those which owe their origin to gla-
cial grinding and mixing. This difference is clearly
brought out in the table given below, which is compiled
from analyses of typical samples of residuary subsoils
from southwest Wisconsin and of glacial subsoils from the
vicinity of Milwaukee as given by Chamberlin & Salisbury
in the Sixth Annual Report of the United States Geolog-
ical Survey:

Residuary Glacial Differ-

Subsoils. Subsoils. ence.
Per cent. Percent. Per cent.

PTR Pd oe Foe rectal aan era aadopiat pe 55.73 44.52 = 11,23
PANU AL Oe com sei Sele ded oe 18.16 8.01 — 10.15
Lime, oe eR ede Ane PWN eae 99 13.74 + 12.75
df Vere) ap Ts ORR nye ie eR Tot 7.42 + 6.31
POCORN 2). 4s o ecate ra eeih aiacde Hohe 1.24 2.48 + 1.24
Phosphorus, Mees BAe ace hve gudsaiol ci viete 03 .O9 + .06
Carbon Dioxide, co, Be NS a lar ahatattane 9) 17.11 -+ 16.76
Lia) Bape oly ee © Fg papa aie pee Oh Ost eA Ra 10.57 2.68 — 7.89
Organic WI GWOL A ce ast aioe bata aman 9.86 2.33 —- 7.53
Other swbstances ole ge5 4 siles c cae 137 1.95 -+-.58

It will be seen that the insoluble sand, clay and iron
compounds predominate in the residuary subsoils, while
the lime, magnesia, potash and phosphorus compounds are
in excess in the glacial subsoils, and this at first thought

seems strange when it is remembered that the residuary

soils are derived directly from magnesium limestones and
that two of the four samples giving the average were
taken in contact with the limestone itself, but these soils
are what is left after the soluble carbonates are ieached aw ay.
The photo-engraving of a relief map of Wisconsin, Fig.
38, showing the olac iated and non- glaciated areas of the
state, also shows, in general, the dintrinudion of the glacial
and residuary subsoils, The area of rugged topography
in the west and southwest of the state is "ehs region cov-
ered by the residuary subsoils. It should not be. inferred,

92
however, that the composition of all of our glacial subsoils a
is fairly represented by the samples from the vicinity of
Milwaukee, for in the northern portion of the state there ,
were no large areas of limestone to be ground down by the
ice to contribute the large amounts of lime and magnesia
found in the locality cited.

Fig. 88.
Photo-engraving of a relief map of Wisconsin, showing the glaciated and non- 2
glaciated areas 0! the state. ~

151. Size of Soil Particles.—The size of soil particles
has very much to do with the value of a soil, this quality
determining, in some measure, its water capacity, its re-
tentiveness of fertilizers, its drainage, its aeration and the
way in which the soil works. In general the relative num-
ber of large grains as compared with the smaller ones is
greater at the surface than at some depth below; this dif-

93

ference is due largely to the tendency of rain to pick up
and carry away or to carry downward by percolation the
finer particles.

Chamberlin and Salisbury, as a result of their studies
bearing upon the sizes of soil particles constituting resid-
uary earths, say: “Out of 158,522 measured particles from
several representative localities, only 929 exceeded .005
mm in diameter. A fairly illustrative example from near
the rock surface at Mt. Horeb, Wis., gave, in a single
miscroscopie field, the following showing;

Particles less than .00285 mm in diameter.................. 15,152
Particles between .00285 mm and .005 mm in diameter...... 208
Particles more than .005 mm in diameter.................. 54

None of the 54 particles reached so great a diameter as .01
mm,” that is, the largest of the 54 large ones had a diam-
eter so small that 25,400 of them placed side by side
would be required to span a linear inch.

Many of the soils which tend so strongly to clog the
plow are of this extremely fine-grained type, and a partial
explanation may be found in the minute particles wedg-
ing into the microscopic cavities due to the grain or text-
ure of the material of the mold-board.

152. Needs of Soil Aeration.—The necessity for a
considerable circulation of air in the soil actively support-
ing vegetation is generally recognized, and the demand
for this circulation is three fold:

1. To supply free oxygen to be consumed in the soil.

2. To supply free nitrogen to be consumed in the soil.

3. To remove carbon dioxide liberated in the soil.

Prominent among the demands for oxygen in the soil
may be mentioned:

The respiration of germinating seeds.

The respiration of growing roots.

The respiration of nitric acid germs.

The respiration of free-nitrogen-fixing germs.

5. The respiration of manure fermenting germs.

It has been abundantly demonstrated that when oxygen
is completely excluded from seeds, placed under otherwise
natural conditions for germination, growth does not take
place; if the germination is allowed to commence and then
oxygen is withdrawn further development will cease.
When the air surrounding a sprouting seed contains only

He CO BO

O4.

zy of the normal amount of oxygen the germination will go
on, but the rate is retarded and a sickly plant is likely to
result. Experience abundantly proves that when soil
bearing other than swamp vegetation is flooded with water,
or even kept in an oversaturated state, the plants soon
sicken and die, and this, too, when they may be in full
leaf and abundantly supplied with nourishment, sunshine
and warmth. The difficulty is the lack of root-breathing.
Oxygen in sufficient quantity cannot reach the roots to
maintain life. The plants are suffocated. This explana-
tion is apparently disproved by the fact that seeds of vari-
ous kinds may be germinated in a float of cotton resting
on the surface of water, and may even be made to mature
seeds if the water in which the roots are immersed is kept
supplied with the proper foods in solution. The floating
gardens of the Chinese, consisting of basket-work made
strong enough to carry a layer of soil in which crops are
matured with their roots immersed constantly in water,
is another apparent disproof that wet soils kill the plants
by depriving them of oxygen. The two classes of cases
are, however, very different. In the cases of water cult-
ure the free water is subject to strong convection and
other currents which rapidly bring the water exhausted of
its free oxygen to the surface, where it becomes charged again.
In the water-soaked soil, with a relatively much smaller
quantity of water, all possibility of convection currents is
prevented by the cohesive power of the soil and the rate
of diffusion in such cases must evidently be extremely
slow, so that, viewed in this light, the two sets of cases
stand in strong contrast.

The natural nitrates, so essential to fertile soils, owe
their origin to a minute germ closely related to the
“mother of vinegar” and called in olden times the “mother
of petre.” This ferment germ produces the nitric acid of
soils which, after uniting with some of the bases contained
in the soil, is absorbed by the plants as food. When the
production of saltpetre was a considerable industry in
Europe one of the conditions necessary to rapid formation
was to keep the rich soil well aerated by frequent stirring
and by the introduction of gratings to increase the air
spaces. Oxygen is one of the essentials to the life of these
important germs, and herein lies, in part at least, the ad-
vantage of cultivation and of properly drained soils.

95

While we have, as yet, less positive knowledge in re-
gard to the respiratory needs of the free-nitrogen-fixing
germs, now coming rapidly into recognition, there is no
reason to doubt the beneficial effects of a properly aerated
soil upon them.

In regard to the manure fermenting germs we have abun-
dant proof of the need of ventilation from their action in
the strong heating of the well ventilated coarse horse ma-
nure when contrasted with the absence of heating in the
close cow dung free from coarse litter.

Not only must oxygen and nitrogen be introduced into
the soil, but the large amounts of carbon dioxide liberated
by the fermenting processes and by the decomposition of
the bicarbonates contained in soil-waters must be passed
out in order to make room for the other gases to enter in a
sufficiently concentrated form to answer the conditions of
life going on there.

153. Methods of Soil Aeration.— Most field soils,
when in their natural undisturbed condition and nearly
saturated with water, are impervious to such air currents
as the greatest differences of atmospheric pressure and
temperature in a given locality can produce. It is un this
- account, in part, that earth-worms come to the surface in
such great numbers during and after heavy rains. The many
perforations made by earth-worms constitute so many
chimneys in and out of which the air moves with every
change of atmospheric pressure and temperature. Culti-
vation as soon as possible after rains aerates the soil at
the time when it contains an abundance of moisture at
the surface and is in the best possible condition for the
rapid action of the nitre germs, which need plenty of air,
moisture and warmth.

Harrowing winter grain in the spring tends to make the
aeration of the soil more perfect by breaking up the crust
formed by the deposit of saline substances brought up by
capillary action.

Drainage, by carrying off the water more rapidly and to
a greater depth, opens the pores of the soil, making its
breathing more perfect.

Strong-rooted crops, like the red clover, which send their
roots deeply into the subsoil, leave it so channeled by the
decay of those roots that a more perfect circulation of air
is thus secured.

Ly

96

154. Soil Moisture.— The moisture contained in soils
is of the utmost importance agriculturally, for without it all
growth is impossible. Some of its chief functions may be
stated as follows:

1. By its solvent power it facilitates and promotes chem
ical changes in the soil.

2. By its expansive power when freezing it mechanically
divides the coarser soil particles into finer ones.

3. By its capillary movements it conveys food to the
roots of plants.

4. By its osmotic power it transports plant fccd tohe
leaves for assimilation.

5. By the same power it conveys the assimilated food to
the tissues for growth.

6. By its osmotic power it swells the seed and ruptures
the seed coats preparatory to germination.

7. By the pressure it is under in the plant it gives suc-
culent tissues much of their rigidity.

8. By its high specific heat it prevents the soil temper-
atures from becoming too high by day and too low during
the night.

155. Amount of Water Consumed by Plants.—Hell-
riegel found, by experiments conducted in Prussia, that
the amounts of water drawn from the soil and given to
the air by various plants under good condition of growth,
for each pound of dry matter produced by the crop in com-
ing to maturity, were as stated in the table below:

NUMBER OF POUNDS OF WATER TRANSPIRED BY PLANTS IN PRO-
DUCING ONE POUND OF Dry MATTER.

Water. Water.
Lbs. Lbs
Harley tees. oot eek ek ee 310 Horse beans’ 3 72e85.. ssk 282
SUMUNEPUPYO Lake ewe ee ys B08 POSS ihc Sect c oes 273
Chath BO eR eee re 376 Red cloveri22ic2 aa ae
DuUMmer wheat e2 se 6.2 6046 338 Buckwheat.3= 2: (cee 363

This, it will be seen, is at an average rate of more than
325 tons of water for each ton of dry matter when grow-
ing under the climatic conditions of Prussia.

For Wisconsin the writer has found results given in the
following table:

ate

NUMBER OF PouNDS OF WATER REQUIRED FOR ONE Pounp or Dry
MATTER AND THE NUMBER OF INCHES OF RAIN PER TON OF
Dry MATTER.

Water. Water.

Lbs. Inches.
PSM EHOOTT A eee ate eke us Aad de ease 309.8 2.64
| SULCUS fag GAC ahd RRM 2 Bt et GAN RT RAL 233 .9 2.14
BPOVOR fic eR err Se ND An eRe, 8! 452.8 4.03
PLO, 5 han steps RBM CON calc Gs BE cae Sk ek C E Ss 392.9 3.43
LUTE TERRES Ries" OT Ege RAE EN DIE ie RY oe a aN 522.4 4.76
LEO ARE Pees aor gat ch te Ban tO bo ere Sa me oe a 477.4 4.21
LGU UTENIO le Baa a ata ic. fy i Rea Rn ge 42.7 ote

The results in this table include not only the water
which passes through the plant, but also that which was
euaporated from the soil upon which the plants grew ana
hence indicate the amount of water the crops reported
were able to use. These amounts, both for Europe and
this country, seem enormous, but there can be no question
but that the quantity needed is very large and necessarily
so because practically all of the dry matter of the plant
requires to be in solution when in transit to the place
where it is finally deposited as a part of the structure.

156. Position and Attitude of the Water-Table.—
The water-table is the surface of standing water in the
soil. The distance the water-table lies below the surface
exerts a marked influence upon the yield of crops per acre.
If the water lies too close to the surface, drainage is re-
quired to secure the best yields; when the water-table lies

does alii yyy

LY
Sal
Fig. 39.
too low, none of that water is available for plant growth.
Permanent ponds and lakes are continuations of the
water-table above the surface of the ground, and their
levels lie at varying distances below the level of the water
in the ground, the water-table rising usually as the dis-
tance from these bodies of water increases and as the

ground rises, as shown in Fig. 39.

o 5o -/00 29°F}
Seale, é.

Fig. 40.

Contour map of area occupied by wells. Figures in lines give height of contours
above the lake in feet, other figures indicate number of wells.

Fig. 41.
Contour map of ground-water surface on June 20, 1892. Figures in lines give
heights of contours above lake in feet; other figures indicate number of wells.

100

157. Wells and Ground-Water.—There are very few
localities on the earth where water can not be found be-
neath the surface, but the distance varies between very
wide limits. Then, too, there are many localities where
water-bearing layers are separated by those which are im-
pervious to water and in which none is found.

On the great majority of farms in our state the water
supply of wells is that which percolates into the soils of
the immediate or closely immediate neighborhood from the
local rains and snows.

The level at which this water can be found is generally
farthest from the surface on the highest ground, and near-
est to it on the lowest ground, but the level of the water
under the high ground is almost always /igher than that
in the low ground; and when the farm borders on a lake,
it by no means follows that wells must be sunk to the
level of this lake in order to procure water. On the
campus of the university there-is a well where the surface
of the ground is 88 feet above Lake Mendota about 1,250
feet distant, but the water in this well is some 52 feet
higher than that of the lake.

In Figs. 40 and 41 are shown, by means of lines of equal
level, the relation which standing water in the ground
holds to the surface above on the Experiment Station Farm
and these serve to illustrate the kind of variations which
occur in most localities where the surface of the ground is
not level. It will be seen from these two plates that the
water surface really has its hills and valleys like the land
and in the same places but differing in relative height.

158. The Lowering of Water in Wells.—One reason
why the level of water in the ground rises as you go
further back from the lakes and other natural outlets, 1s
because the friction of the water in flowing through the
soil increases the further it has to flow through it, and
this principle affects the supply of water in wells.
~ When a new well is dug, and considerable quantities of
water are being pumped from it, it becomes a new drain-
age outlet, and the surface comes to take the form indi-
cated in Fig. 42, and the level of the water in the well
takes a new height depending on the amount of water used
and the rate at which the water can flow through the soil.

159. How to Dig Wells That Will Not Give Out in

‘ Dry Times.—Referring again to Fig. 42, it will be seen

ad

101

that if the bottom of the well is at C, it is not ‘possible to
get as steep a slope down which the water can flow into
the well as would be possible if the well were sunk deeper,
as at E, and hence during a series of dry years the general
level of the ground mate would become so low tink the
water must “necessarily flow into the well very slowly, if
at all, whereas with a deeper well it is possible to pump
the surface down until, by making the slope steeper, the
rate of flow into the well remains constant, or nearly so.

100 90 50 70 60 50 40 30 20 10 Wel 10 20 30 40 50 66 70 $0 $0 100

Fig. 42.

Showing the effect of pumping on .he ground water surface.

Whenever a well is to be dug, therefore, there should be
made an estimate of the probable daily consumption of
water from it, and the larger the demand is, the deeper
the well should be sunk below the level at which water
stands in it at first. The'c capacity of a well, like the capac-
ity of a hay mow, is very greatly increased by adding a few
feet to the bottom of it, and it never can be done as ~ cheap-
ly at any other time as when it is being dug. The Gis-
tance the bottom of the well should be sunk below the sur-
face of the water will generally be greater the finer the
soil is through which the water must flow in coming to the
well. That is to say, if water is to be found in a coarse
gravel the bottom wiil not need lowering as far as if it is
found in fine sand or in clay with thin seams of sand or
gravel.

160. Percolation of Impure Water into Wells.—
There is a tendency, especially after heavy rains, for sur-
face water to percolate into wells, and if the well is so
situated with reference to the barn yards, the privy, or
places where slops are thrown from the house or where

102 ©

the drain from the kitchen leads into a dry well, there is
great danger that the well water may be polluted by the
‘ain taking up the surface impurities and carrying them
into the well. In very wet times, when the soil is full of
water at the surface, a well, whose walls are not water
tight, furnishes an easy outlet into which the water drains

BERBER AAR EAMes

ED Ds
f °
Leg A

Pere
ws o** =
eS. =
Nig ere =
ra rerte ts 8
ett ee
a Parerg?
Si Sereials
+ ® ete et
>a ae ie.
e og peg ON \ ,
wn Suen? Vitel a a vevee reat %
de epie es Cla g glte Jy: =
te si | . e ! > *
i Lone: of (Soil.
Fd te e e e > . Ra ey
. °°. = 7. CR >
e SUC As © yes EG ‘ e
: . > 2g. a
‘Sain which’.
ty as ee rare MNS oe aitOn eres . 8 * Pet
5 Sip Skea! ae uO Sirauety * ta . = . oie
hat erie okt erat . . ans . poet etiee aC e ° ests
. e'3 - Sid
Ser eo ee we ee - One ° . Opa a f RE rieer
NT ate A iba ew PT gre ase ke Ate, ae ce
se hay . .

eile wl:
aK eee ek .

nen = ll: ~

Showing the percolation of water into and out of wells.
in the manner illustrated in Fig. 45, causing the water to
rise rapidly, sometimes from one to three feet. In such
cases the air in the soil below the very wet surface pre-
vents the water from moving downward until the air-can
first escape and open walled wells furnish an easy escape
for the soil-air at such times, and this results in the water

ey

103

following the soil-air into the well as shown in the figure.
Wherever it is practicable to do so, farm wells should
be provided with water tight curbing of some sort extend-

before water is reached.

From the standpoint of pure water the five or six inch
iron tubing now used in drilled wells and the smaller sizes
used in drive-wells are among the best safeguards against
surface contamination.

Wells where the supply comes from nearer the surface
than 10 ft. ought generally to be avoided as a source of
drinking water. In such localities the well should be sunk
deeper and the surface vein cut off by a water-tight curb-
ing if it is practicable to do so.

Pugs yy
Showing changes in the surface of the water-table under alternate fallow plats and
plats of growing corn. The straight lines connect the water-levels of wells 1

and 7 on the dates specified at the right, and the broken line joins the water
surfaces of wells 2, 3, 4, 5 and 6 on the same dates.

161. Fluctuations in the Level of the Water-Table.
—The level of the water in the ground is not constant, but
stands higher after a series of wet years and falls again
with a succession of dry seasons. There is also an annual
rise and fall of the water-table, the water standing lowest
toward the latter part of fall or early winter and highest
in the spring. In those cases where the water-table lies near
the surface it is frequently raised by single heavy rains.

e

Even changes in atmospheric pressure affect slightly the

104.

level of water in wells, causing it to rise with a falling
barometer and fall with a rising barometer.

The growth of crops appears also to affect the height of
the water-table when it lies near enough the surface to
come within range of root action. This “effect is shown in
Fig. 44, The same figure also shows to what extent ‘the
water-table fell during a growing season.

162. Best Height of the Water-Table.—It is a matter
of great importance, as bearing upon all questions of land
drainage, to know at just what distance below the surface
of the ground the water-table should lie to interfere least,
and at the same time to contribute most, to plant growth.
In European cultivation it is held that the tillage of moors
and bogs can only be successful when the water-table is
maintained at least three feet below the surface in summer
and 2 feet in winter. For light and gravelly soils in good
condition a depth of 4 to 8 feet is held to be best for the
majority of crops. The problem is manifestly a complex
one which cannot be simply stated. The case must vary
with the character of the soil, with the season, and with
the habit of the cultivated crop, as to whether it is natur-
ally a shallow or a deep-rooted one.

163. The Vertical Extent of Root-Feeding.—Just
how deeply root-feeding may extend below the general
limit of root growth must depend upon the vertical dis-
tance through which capillary action is able to pass water
upward into the root zone. In the fall of 1889 it was
found that clover and timothy, growing upon a rise of
ground some 28 to 30 foot above the water-table, had re-
duced the water content of sand, at a depth of 5 feet, to
4.92 per cent. of the dry weight, when its normal capac-
ity was about 18 per cent., and this seems to be a case of
strong root-feeding to a depth of more than 5 feet.

In the table below are given the percentages of water in
the soils of closely contiguous localities bearing different
crops; the distance between the two most distant localities
not exceeding twelve rods and the ground nearly level:

105

SHOWING DepTH OF ROOT-FEEDING Aas INDICATED BY THE WATER
CONTENT OF THE Sort Avuaustr 24, 1889.

Clover in Timothy and Corn. Fallow

Depth of Sample. Pasture. Blue Grass. Ground.

Per cent. Percent. Percent. Per cent.
MEWNIK iG meta «ls ogrcce ore 8.39 6.55 6:97 16.28
GENE eac st Sntete chs 8.48 7.62 7.80 17.74
10.9 ols eae eae eae LA 5 11.49 11.60 19.88
Meroe et SE 13.27 13.58 11:98 19 84
Seem MIN eats givin: oh 13.52 13 26 10.84 18.56
0 Sor 2 AW En 9.53 18.51 4.17 15.90

Distance of lower sam-

ple above water-table 2.36 ft. BOT it: Bel Dit: 2.22 ft.

This table shows clearly that root-feeding, in the case of
both clover and corn, extended to a depth of at least four
feet, and that the corn had fed deeper than the clover. It
also shows that the timothy and blue grass had exhausted
the soil moisture near the surface more than either of the
other crops, but that the depth of feeding was less.

The strong difference which is shown to exist between
the amount of water in the fallow ground and the ground
bearing crops shows in a marked manner the strong dry-
ing influence of growing vegetation upon the soil.

164. Capacity of Soil to Store Water. —The rainfall
of our state during the summer season is rarely enough to
meet the demands of vegetation during the growing pe-
riod, but the soil acts as a reservoir, retaining consider-
able quantities of that which falls at other times. All
soils, however, have not the same storage capacities, and
hence on fields receiving the same rainfall the water sup-
ply for crops may be very unequal.

Klenze makes the following general statements in re-
gard to the water capacity of different soils:

1. The saturation capacity of a given kind of soil in-
creases as the size of the smallest particles decreases.

2. The capillary capacity of a given soil containing only
capillary spaces decreases as it is made more close and
firm.

3. The saturation capacity of soils is decreased by in-
creasing the number of cavities which are larger than the
capillary spaces.

4. The saturation capacity of soil decreases as the tem-
perature increases. 7

106.

In the following table are given the percentage and ab-
solute capillary capacity of a section of soil 5 feet deep,
as found by experiment, the soil being in its natural con-
dition:

Percent. Pounds Inches

of of of
Water. Water. Water.

Surface ft. of clay loam contained..... o2.2 23.9 4.59
Second ft. of reddish clay contained... 23.8 22.2 4.26
Third ft. of reddish clay contained.... 24.5 22.7 4.37
Fourth ft. of clay and sand contained... 22.6 22.1 4.25
Fifth ft. of fine sand contained........ i A es 19.6 5 a bf
dl AC o's Ne CN aan § ta ets ep ee Rite eS, | OR oe? 110.5 21.24

These figures show that the actual storage capacity of 5
feet of soil is really very large, in the case in question,
agoregating

43560 x 110.5
2.00

and this, at the rate of 325 tons of “water per ton of dry
matter, is sufficient, were it all available, to give a yield
of

2406. 69 tons per acre.

2406.69
325

Fig. 45 represents the proportions by volume, of soil,
air and water in the above section,

The large storage capacity given to the soil in the last
section will be found true only at very wet times, or
where standing water in the ground is very near the sur-
face. In all sandy soils, and probably in all others, the
water slowly runsout downward and the morecempletely the
farther the surface is from standing water in the ground.
In Fig. 46 is shown both the method by which this fact
was proven for sand and the distribution of water in it
after all the water which would run out had done so.
There it will be seen that the upper 6 in. could retain but
1.93 per cent. of its dry weight of water while the lower
6 in. retained 18.17 per cent., or more than nine times as
much. |
165. Proportion of Soil-Water Available to
Plants.— Not all the water which soils contain is availa-
ble to plants, and considerable must remain unused if large
yields are expected; we have also seen that soil fully sat-
urated is not in a suitable condition to produce crops.

=7.405 tons of dry matter.

by
So
ee
Sa
re
—
an
SSS ee
—_—
ee

__£===

Fig. 46.
Showing the relative volumes of

water, air and soil in the upper
five feet of cultivated ground.

Fig. 46.

Showing method of determining the ca-
pacity of long columns of soil for
water, and its distribution.

108

Hellriegel concludes from observations of his own that
soils give the best results when they contain from 50 to
60 per cent. of their’ saturation amounts, but this, I think,
should be understood as applving strictly only to the up-
per 12 to 24 inches of soil because, as the season ad-
vances and the roots develop downward, the water of the
subsoil is drawn upon gradually as it is needed, and the
per cent. of saturation is reduced to the proper amount.

During the season of 1890 Litch Dent and White Aus-
tralian Flint corn grew side by side at the Experiment
Farm in a light clay loam underlaid with sand, the soil
coutaining at the time of planting 22.41 per cent. of
water, and at the time of cutting 15.45 per cent., the mean

saturation capacity being about 25 per cent. ‘The Dent
gave a yield of 9,875 pounds of dry matter per acre and
the Flint 6,000 pounds. -The amount of water lost by
transpiration, evaporation and drainage was at the rate of
456 pounds of water per pound of dry matter for the Dent
corn and of 610 pounds for the Flint.

An examination of the figures in 168 will show how
completely crops may reduce the water-content of soil dur-
ing dry seasons; those given there, for corn, being from
the same locality as the above for the year 1889.

166. Kinds of Soils which Yield Their Moisture
to Plants Most Completely .— The sandy soils yield their
moisture to plants much more completely than do the
clayey and other soils having a greater water capacity.
This is clearly shown in 163, where sand, at the bottom
under the corn, contains only 4.17 per cent., while the
clay with sand mixed, in the second foot of the same sec-
tion, contains an average of 11.79 per cent. The satura-
tion capacity of the first is about 18 per cent., while that
of the latter is about 26 per cent. The sand had given up
more than three-fourths of its water while the clay still
retained nearly one-half.

If we compare the absolute amounts 6f water given up
by each of the two soils in question we shall find that the
sand had yielded 13.83 pounds per cubic foot, while the
clay had yielded only 12.5 pounds. It thus becomes evi-
dent that while the percentage capacity of the sand is much
below that of clay its greater weight per cubic foot and
the greater freedom with which it yields water to plants

makes its practical storage capacity for water, so far as

’

109

crops are concerned, nearly as great as the loamy clays. It is
thus very clear that a sandy soil kept well fertilized has
many advantages over the colder, less perfectly aerated and
more obstinate clayey ones, which crack badly in excessively
dry weather and become supersaturated in wet seasons.

167. Movements of Soil Water.—The water in the
ground is subject to at least three classes of movements:

1. Those due to gravitation.

2. Those due to capillarity.

3. Those due to gaseous tension.

The direction of movement in each of these cases may
be either:

1. Downward.

2. Lateral.

_ 3. Upward.

The gravitational movements are the most rapid, most
extended and belong to two types:

1. Percolation movements.

2. Drainage or current movements.

The percolation movements are, as a rule, slower than
the drainage movements and are usually downward, being
only occasionally and locally upward; they consist of the
slow filtering of water through the smaller soil pores.
It is chiefly by percolation that ali water finds its way
into the ground.

The drainage currents consist of those portions of the
percolation waters which could not be retained in the sur-
face soil by capillary action. They move like streams of
water on the surface or like currents through pipes, giv-
ing rise to springs and flowing wells.

The capillary movements, 80 to 82, constitute the slow

creeping of water over the surface of soil particles and

root-hairs. In direction they are chiefly toward the
surface of the ground and toward the root-hairs, during
the time when these are in action; but after showers there
may be capillary movements downward provided there is
unsaturated soil below, but even under these conditions it
will not always occur.

The gaseous tension movements originate in the changes
in volume of the confined air due to changes of tempera-
ture and of atmospheric pressure referred to in 99 and 161.

168. Rate of Percolation.—The rate at which water
percolates through soil varies with its character and

110

physical condition. As a general rule the percolation is
more rapid through the coarse-grained soils than it is
through those of a finer texture, and it is on this account
that sandy soils leach so badly, Clayey subsoils, especially
if they are underlaid with sand, very often shrink and
break into great numbers of small cuboidal blocks leaving

numerous fissures between them which open down to the-

sand below; through these a large amount of percolation
may take place; and this effect is greatly intensified when
the surface of the ground becomes cracked, as it often does
when not prevented by cultivation. When in this condi-
tion such soils may leach even worse than sandy soil. The
perforations made by earthworms and other burrowing ani-
mals also exert a considerable effect upon the percolation
of water and the leaching of soils.

In case a winter sets in with fall rains insufficient to sat-
urate the soil and close up the shrinkage cracks and the
channels formed by burrowing animals, considerable water
finds its way into the ground after it has been deeply frozen.
During the winter rains and thaws which occurred in
1889, 1890 and 1891, there was a large amount of perco-
lation on the Experiment Farm made evident by the alter-
nate starting and stopping of the discharge of water in the
tile drains. These facts have a significance in their bear-
ing upon the practice of winter hauling aud spreading of
manure.

169. Rate of Capillary Movement. —The rate of cap-
illary movement in soils varies with the kind of soil, with
the physical conditions, and also with the amount of water
it contains. It appears to be more rapid in sand than it
is in clay, and more rapid in clay containing humus than
in that without. It is more rapid in a well firmed soil
than in one possessing large pores. The degree of close-
ness may, however, be so great as to impede the rate of
movement.

I have found that water may rise through 4 feet of fine
quartz sand at a rate exceeding 1.75 pounds per square
foot in 24 hours, and in a light clay loam at a rate greater
than 1.27 pounds per square foot. In these cases, how-
ever, the soil was devoid of all spaces except those pro-
duced by the form and size of the particles, and the rate
was measured by the amount of evaporation; but as the
soil remained wet at the surface throughout the experi-

ae.” eel

FUT

meat the possible capillary rates must exceed those stated
by undetermined amounts. I have found changes in the
water-content of the soils of fields which indicate that,
under these conditions, the rate of capillary movement,
when the soil is wet, may exceed 1.66 pounds per square
foot.

When the soil is perfectly dry the rate at which water
moves through it is relatively very slow, so slow that five
cylinders of soil, each 6 inches in diameter and 12 inches
high, standing in water one inch deep, and in a satu-
rated atmosphere, required the intervals stated below for
water to reach the surface in sufficient quantity to make it
appear wet.

Tn clay loam, time required to travel 1l inches..........- 6 days.
In reddish clay, time required to travel 11 inches........ 22 days.
In reddish clay, time required to travel 11 inches........ 18 days.
In clay with sand, time required to travel 11 inches..... » 6 days
In very fine sand, time required to travel 11 inches ...... 2 days.

These are very fundamental facts in their bearing on
the control of evaporation by surface tillage.

170. Translocation of Soil-Water.— It frequently
happens, in certain soils after rains and in most, if not
all, soils after rolling or firming, that water is brought up
into the surface stratum from the deeper layers; this
change of position is named translocation and has impor-
tant bearings upon questions of tillage.

The translocation caused by rolling or otherwise firming
the soil is due to the fact that reducing the non-capillary
pores in soil increases its capacity for water and the rate
at which water will move into it by capiilarity, and this
influence is sometimes felt to a depth of three to four feet.
The deeper soil-waters may in this way, therefore, be
brought to the surface or within the zone of root growth.

The translocation caused by wetting the surface depends
upon the principle that when the per cent. of water in a
soil has fallen below a certain limit its ability to take
water from another soil is decreased, and that when it has
risen above a certain limit this ability is then diminished,
that is, for each soil there is a certain water content at
which the water enters it at the most rapid rate. It there-
fore frequently happens that the water-content of the sur-
face soil is below that at which water enters it most rap-
idly, and when a rain comes which restores its strongest

112°

A

action again, water is also taken into it from the soil be-
low so that the surface stratum may, in consequence of a
rain, receive more water than actually fell, while the soil
below is, by translocation, rendered actually dryer than
before the rain. This fact has an important bearing upon
surface tillage immediately after showers, upon the trans-
planting and watering of trees and upon questions of irri-
gation. If the surface, after a rain, is allowed to remain
undisturbed, the rapid evaporation which occurs in such
cases may take away ina short time not only that which
had fallen, but also that which was brought up by capil-
larity from below, whereas simply stirring the surface, de-
stroying the capillary connection below, would allow the
surface only to dry and act as a mulch, retaining the bal-
ance in the eround for the use of the crop.

re. Influence of Topography on Percolation.— The
slope of the surface influences, sometimes in a marked
manner, the percolation of rain-water and the water-con-
tent of the soil. Whenever rains occur which are suffi-
ciently heavy to cause water to flow along the surface,
trom the hill-tops toward the lower and flatter areas, less
water is left to percolate on the highest sloping ground,
while the more nearly level areas may have not only the
water which falls as rain upon them, but a portion of that
which has fallen upon other ground. Nor is this all; as
the water-table is generally higher under the high ground,
156, there is a constant tendency for the water in the soil
itself to percolate from the high lands toward the low
lands, and so, when the water-table here lies within reach
of root action, to increase the water supply for the season,
sometimes to a disadvantageous extent, making drainage
necessary, where in the absence of the high land it would
not be needed.

In those cases where the water-table under the high land
is below the level of the surface of the low lands, and the
low lands remain long over-saturated, there is a tendency
for the water to percolate toward the higher ground, but
of course to return again at a later season.

172. The Lossof Water by Surface Evaporation.—The
loss of water by surface evaporation from the soil is very
large during the early portion of the season and especially
so if the surface of the ground is left long undisturbed.
The writer has shown by. experiments that a piece of un-

¥

x

1

es

115

plowed ground lost, in early May, during seven days, 9.13
lbs. of water per square foot from the upper four feet of soil,
or at the rate of 1.304 lbs, perday. And also that a clay
loam lost water in the upper three feet at the rate
of 6.45 lbs. in one case, and 5.69 lbs. in another
during four days, or at the mean rate pec day of
1.52 lbs. per square foot. During the present season,
six cylinders each 42 in. deep, and 18 in. in diameter,
were filled with soil saturated with water and placed in
the open field, sheltered from rains by a canvas awning
placed so as to allow about 12 in. of free space for the
circulation of air over their tops; under these condi-
tions there was evaporated from these surfaces an aggre-
gate of 226.7 lbs. of water during 34 days from June 27,
to July 31, or at the mean rate of .63 lbs. per square ft.
daily, and this was in the shade. The first two figures
given, 1.304 lbs. and 1.52 lbs. per day, give an average
loss per acre of 30.75 tons of water daily by surface evap-
oration when it takes place under the most favorable con-
ditions, while the last figure, .63 lbs. represents a loss by
surface evaporation of 13.72 tons daily which is less than
the average unless very careful and thorough tillage is
practiced.

At the larger figure, water is going away at a rate suffi-
cient for nearly a ton of dry matter of corn every 10 days
from each acre of ground, and at the slower rate still fast
enough to consume in 100 days the water required for 4.4
tons of dry matter of corn which is considerably more than
an average yield in Wisconsin for the best farming. Sure-
ly, then, here we have evidence ample to show that the
careful husbanding of soil moisture is an essential part of
successful farming in our climate.

173. Influence of Topography Upon Evaporation.—
It is a matter of common observation that the south-and

‘southwest slopes of steep hills are often simply grass-cov-

ered, while the north and northeast slopes may be heavily
wooded. This difference of verdure is due largely to a dif-
ference in soil moisture on the opposite slopes, which is
determined chiefly by the difference in the rate of evapo-
ration upon the two slopes.

Other things being the same, the rate of evaporation, in
our latitude, is greatest on hill-sides sloping to the south-

114

west and least on those sloping to the northeast. Several
conditions work in conjunction to produce this effect:

1. More air comes in contact with windward than with
leeward slopes, and as rapid changes of air over a moist
surface increase the amount of water taken up, the evapo-
ration is greater on the windward slope.

2. Our prevailing winds, during the growing season,
are southwesterly, and hence more air comes in contact
with southwest slopes.

3. Westerly and northerly winds are, with us, al-
most always drier than easterly and southerly winds, and
as evaporation is more rapid under dry than under moist
air the westerly slopes are drier than easterly ones.

4. Other things being the same, surfaces which are near-
est vertical to the sun’s rays receive most. heat, and for
this reason southward slopes, in the northern hemisphere,
become most heated, and as evaporation takes place more
rapidly at high than at low temperatures, southerly and
southwesterly slopes lose most moisture from this cause.
Fig. 47 shows how a surface inclined toward the south

s

Fig. 47.

must receive more heat per square foot than either the
level surface or on the one inclined northward. If A65B
is a section of a cylinder of sunshine falling upon the hill
AEB, it is evident that A64E, the portion falling on the
south slope, is greater than E45B, the portion falling on
the north slope. It will also be evident that the 20-degree

115

slope receives more heat than does the 5-degree slope, and
this more than the level surface.

The effect of the wind upon the evaporation from the
soil is at its maximum at the summit of a hill, because at
this place the wind velocity is greatest, no matter from
what direction it may be blowing.

174. Effect of Woodlands on Evaporation. — A piece
of woodland which lies to the southwest and west of a field
exerts a considerable effect upon the humidity of the air
which traverses that field, the tendency being to make the
air more moist. Taking a specific illustration, the air on
the leeward side of a second growth black-oak grove was
found, on one occasion, to contain 3.3 per cent. more moist-
ure than did that on the windward side at the same time;
and again, when the wind was in the opposite direction,
observations in the same localities showed 3.8 per cent.
more moisture on the leeward side, the observations in the
four cases being taken about 10 rods from the margin of
the grove. There was observed at the same time a differ-
ence of air temperature of 1.5° F., the leeward air being
this much cooler in the field 10 rods from the grove, the
width of the grove being about 30 rods and the trees from
20 to 30 feet high.

TILLAGE.

175. The Objects of Tillage.—The chief objects of till-
age may be briefly stated as follows:

1. To destroy undesired vegetation.

2. To place organic matter of various kinds beneath the
surface where it “will more readily ferment and decay and
be brought within the reach of root action.

3. To develop a loose, mellow and uniform texture in cer-
tain soils.

4. To control the water-content of soil.

5. To control the aeration of soil. 152 and 153.

6. To control the temperature of soil.

176. The Destruction of Undesired Vegetation.—In
securing this object of tillage we have two classes of vege-
tation to destroy, one, like the prairie grasses of a virgin
soil or like the cultivated meadow grasses, which must be
destroyed before there is root room for the desired crop, and
the other which is designated by the general term of weeds.

Plants spread out two broad surfaces, one in the air to
obtain carbon dioxide, oxygen and sunshine, and the other
in the soil to obtain water, nitrates and other food con-
stituents. It requires but little study to reveal the fact
that plants usually spread out their leaf surfaces in such a
manner that each leaf shall be forced as little as possible
to breathe the air of another leaf and that one shall shade
another as little as possible. In a dense forest or thicket
no fact stands out more prominently than the race each
plant makes to outreach its neighbor and get into bright
sunshine and free air. <A study of root development shows °
that the same law is followed beneath the surface. There
are times of scarcity of food, and each root and rootlet
tends to develop away from its neighbor into an unoccu-
pied territory. Such facts teach, with abundant evidence,
that there is no room for weeds in any soil where another
crop is expected.

When we remember that each pound of dry matter re-
quires more than 300 pounds of water taken from the soil,

al

and that in most soils there is usually a scant suply of
moisture at best, the importance of a weedless surface
should be appreciated.

The following definite case will serve to show how rap-
idly weeds may consume the water of soil.

On May 13, 1889, the water-content in the soil on ad-
joining margins of a field just planted to corn an _ one of
clover and timothy, was determined on the Experiment
Farm, with the results below:

Corn ground. Clover ground.
Per cent. of water. Per cent. of water
Surface to 6 in. contained. yo ee 95 9.59
12 to 18 in. contained..... Ss 14.79
18 to 24 in. contained..... 16.85 13.75

These figures illustrate in a very forcible manner the
great power vegetation has of withdrawing water from the
soil, how naked tillage conserves it, and the importance,
in all except the wettest seasons, of not allowing weeds to
occupy cultivated fields.

177. Plowing in Organic Matter.— The decomposi-
tion of most animal and vegetable tissues is the result of
a growth in and upon them of micro-organisms which, like
all other living things, require a bountiful supply of moist-
ure. Moisture is usually found in abundance at the sur-
face in the shade of dense forests, but in open cultivated
fields the stems of plants and coarse manures are too dry,
most of the time, to maintain the life of micro-organisms
unless they are buried a little distance below the surface
where the rate of evaporation will be checked, and where
there is a better capillary connection between them and
the water of the soil. In this condition, if the soil is
sufficiently aerated so that the respiration of the life going

on there is ample, the organic tissues are rapidly broken

down and quickly become available as food for crops.
178. Circumstances which Modify the Time and

Depth of Plowing in of Manure.— We are yet a long

way from being in possession of the rigid knowledge which
is needed to make specific and exact statements regarding
matters like these. There are some general statements,
however, which may be helpful in practice if not followed
too implicitly and without judgment.

Coarse manures, when plowed in, tend at -first, to cut
off the capillary connection with the soil-water below, and

118°

where the plowing occurs in the spring, certain crops are
liable to suffer from drought because of a lack of moisture
in the surface soil; this is especially liable to be the case
if the spring is dry. If heavy, soaking rains follow the
plowing in of such manure, the soil particies are washed
in between its straws and other litter and a good connection
establshed between the surface and the soil below. This is
what does happen usually in the case of fall plowing, and
explains why on many, if not most, soils, the fall plowing
in of such manures is preferable. It is evident that on
soils naturally too wet, and especially in wet seasons, the
spring plowing, in such cases, might be preferable.

If manure is plowed in too deeply, and especially if the soil
is close and fine, there is danger of too little air to permit
of roapid decay, and the effects of manure under such con-
ditions will be only partially felt the first season,

If the soil is a leachy one, plowing the manure in deep-
ly tends to increase the loss by underdrainage.

179. Effect of Manures on the Water Capacity of
Soils. — Humus stands foremost among the ingredients of
soil in its power to retain capillary water. The barnyard
manures, besides containing large quantities of saline fer-
tilizers, contain much undigested vegetable fiber, which,
when plowed into the soil, tends to decay into ordinary
soil humus and thus to increase the water capacity of the
lands to which they are applied; in this respect they have
a superior value, when compared with most commercial
fertilizers, especially if it shall be established that organic
matter, in contact with dry earth, does oxidize with a loss
of free nitrogen.

180. The Importance of Good Tilth. — It is a gener-
ally recognized fact that one of the chief objects of tillage
is to produce a mellow seed-bed of uniform texture, and
there are several desirable ends which are met wholly or
in part, by good tilth. ;
~ One of the strong recommendations of a rich sandy soil
is found in the evenness of its texture and the lack of ad-
hesion between its grains which permit of almost perfect
symmetry in the development of roots and allows the root.
hairs to occupy most completely the soil interspaces. When
this is true, not only is all the soil laid under tribute, but
each and every rootlet, with its numerous root hairs, is do-
ing fuli duty. If, on the other hand, the soil is uneven

119

and filled with hard lumps, a large portion of it is not
only unavailable but it stands as a positive hindrance to
root development, checking rapid root growth and making
a much gr eater actual length of roots necessary in order
to come in contact with a sufficient amount of soil. Noris
this all; during the process of cultivation the lumps tend
to work to the surface and become very dry; in this con-
dition they absorb a large percentage of the summer rains,
and, and as they are almost completely surrounded by free
air, they give back this moisture to the atmosphere and
thus prevent it from rendering any service.

On the principle of oxidation of nitrogenous compounds
with the liberation of free nitrogen the lumpy condition of
soil should be expected to bea large source of loss of that
important element of plant food.

Mellow soil favors root-development in being easily
crowded aside by the expanding roots, and this is a mat-
ter of some importance in all the succulent root crops,
like beets, parsnips, turnips and carrots, for the actual soil
displacement in an acre of these crops is very great, and the
conclusion seems irresistible that a hard soil must mechan
ically impede root-growth in such crops to a large extent
' A mellow, even textured soil is likely to be much better "
aerated than one not in this condition and better supplied
with moisture also.

181. Control of the Water-Content of Soils. —The
operations of tillage aiming to control the water-content
of soils proceed along one of three lines of action:

1. To conserve the water contained in the soil.

(a) By surface tillage.
(b) By flat culture.
(c) By mulching.
2. To reduce the quantity of water in the soil.
(a) By deep tillage.
(b) By decreasing the water emeety.
(c) By ridge culture.
(d) By surface drainage.
(e) By underdrainage.
({) By tree planting.
3. To increase the quantity of water in the soil.
(a) By increasing the water capacity.
(b) By irrigation.
(c) By firming the surface soil.

120

182. Conservation of Soil-Water.—On the great ma-
jority of cultivated lands there is, as a rule, an insufficient
supply of moisture to give the largest possible yield when
other things are favorable; and hence it becomes a matter
of importance to check the evaporation from the soil sur-
face and divert the water currents through the growing
crop.

183. Surface Tillage to Check Evaporation. —In one
of my experiments, where the rate of evaporation from the
undisturbed surface of clay loam had been going on at the
rate of .9 pounds per square foot in 24 hours, simply re-
moving the crust of salts brought to the surface and de-
posited there by evaporation, increased the rate of evap-
oration to 1.27 pounds per square foot in the same time,
and I found the same fact true for fine sand. These facts
have a bearing upon the practice of harrowing winter
erain in the spring, suggesting that the practice, may, in
some cases, cause a waste of water. ihe,

In the case of the fine sand referred to, the evaporation
had been taking place at the rate of .91 pounds per square
foot in 24 hours, just before the crust was removed; after
its removal the surface was cut in small squares with the
blade of a sharp knife held vertical to the surface, and then
the rate of evaporation rose from .91 pounds to 1.75 pounds
per square foot per day. On removing a thin layer of the
sand, and replacing it immediately, the rate of evapora-
tion fell to less than .5 pounds per square foot daily. It
is thus shown that one form of surface tillage may increase
the rate of evaporation while another form may check it in
a very decided manner.

A tool working like the disc harrow when the discs are
running at a small angle, simply slicing the surface as the
. knife did, increases the surface exposed to the air without
destroying the capillary connection with the soil below,
and tends to hasten rather than retard evaporation; but if
the tool completely removes a surface’ layer, leaving the
ground covered with a layer of loose soil, a mulch is pro-
vided which excludes the air, in a measure, and greatly
retards evaporation.

184. Influences of Early Spring Plowing. — A field
test was made of the influence of early spring plowing in
checking the loss of water from the soil. One piece of
ground was plowed on April 28, and sowed at once to oats.

121

The amount of water in this soil was determined, in one-
foot sections to a depth of four feet. Seven days later the
water in this ground was again determined, and also in

_another strip lying immediately alongside of it which had

not been plowed. The results showed that the upper foot
of soil on the plowed ground had lost only 4.65 tons per
acre; and the other three feet had gained enough from be-
low to leave the average unchanged, while the same depth
of soil on the ground not plowed had lost 198.9 tons per
acre. Nor was this all; the ground first plowed was in
perfect tilth, while that plowed six days later had devel-
oped in it such hard and large clods that it became neces-
sary to go over it twice with a loaded harrow, twice with
a disc harrow, and twice with a heavy roller, before it
was brought into a condition of tilth even approximating
what it would have had, had it been plowed six days earlier.
It is evident, therefore, that the early stirring of
soil in the spring not only saves the much-needed moisture,
but it also prevents the formation of clods, a condition of
soil which always greatly decreases its productiveness.
185. Effectiveness of Thin Soil Mulches.— Experi-
ments have shown that even very thin mulches exert an
appreciabie influence on the rate of surface evaporation.
As results of trials it was found that in still air stirring
the soil to a depth of one-half inch gave a daily evapora-
tion per acre of 5.73 tons as against 4.52 tons when stirred
to a depth of three-fourths of an inch, while the undis-
turbed surface lost water at the rate of 6.24 tons daily. In
the case of mulching with fine air-dry soil the results showed

a loss of 4.54 tons per acre for a layer one-half an inch

thick but only 2.4 tons when the layer was three-fourths
of an inch thick as against a loss of 6.33 tons where the
surface was not covered. These figures bring into strong
relief the great effectiveness of even a thin layer of fine
dry soil in checking surface evaporation and serve to em-
phasize the importance of keeping soil in good tilth and of
using tools which will leave the surface blanketed with a
fine, even coat of soil.

186. Influence of Cultivation on the Evaporation
of Soil Water.— Experiments in the field on fallow
ground have shown that frequent cultivation as compared
with no cultivation, saved water at the mean rate of 3.12
tons per acre during a period of 49 days.

L22h -

So cultivating three inches deep as compared with one
inch has been found to leave the ground 167.4 tons of
water per acre more moist at the end of the season, and
this under natural field conditions with corn as the crop.

187. Flat Cultivation.— When the surface of the
ground is thrown into ridges, as in hilling potatoes or corn,
the amount of surface exposed to the air is increased, and
this, other things being the same, tends to increase the rate
of evaporation from the surface and diminish the supply of
moisture for the crop. When three-foot rows are ridged
to a height of six inches the surface is increased more
than 5 per cent., and when ridged to the height of eight
inches, more than 9 per cent.

188. Deep Tillage to Increase Evaporation.— When
the ground is stirred to a considerable depth repeatedly
there is a large and rapid evaporation from the soil stirred,
and this is one of the chief objects of discing and harrow-
ing lands that are to be planted early in the spring. The
ground is cold from the low temperature of winter and
from the large volume of contained water which requires
a great amount of heat to warm it. Getting rid of this
moisture by deep tillage provides a warm and ‘mellow seed-
bed, well aerated, which also acts as a mulch to conserve
the deeper water of the soil until a time when it is
needed.

189. Firming the Ground to Control Moisture. —
Rolling or otherwise firming land, after it has been tilled,
may have two distinct objects as regards the control of
soil-water. These are:

ieee dry the soil as a whole.

2. To increase the moisture ot the seed-bed.

We have shown by two distinct lines of investigation
conducted in the fields of the Experiment Farm that roll-
ing tilled land tends to dry the soil, as a whole, the etfect
being measurable at a depth of at least four feet. This
drying effect is brought about —

1. By increasing the capillary power of the surface.

2. By increasing the surface temperature.

3. By increasing the wind velocity at the surface.

These three important effects tending to dry the soil may
be employed to secure the most rapid evaporation when re-
peated deep tillage and rolling follow each other at short in-
tervals. Stirring the soil deeply, exposes a large surface

123

of moist earth to the air which dries quickly, and if this is
rolled as soon as dry enough, the soil again becomes wet
at the expense of the deeper soil moisture, and this is soon
lost if deep tillage follows. Repetitions of these processes
are an excellent treatment for a seed-bed in too damp cold
soil.

When the soil of the seed-bed is too dry for the proper
germination of seeds, then firming the ground tends to in-
crease the moisture by bringing it from below to the place
where it is most needed, and the press-wheels used on va-
rious forms of drills and planters have this to recommend
them. They concentrate the moisture at the points where
it is most needed, leaving the remaining portion of the
field covered with a loose protecting mulch. In the case
of broadcast seeding, rolling is generally required, if the
seed-bed is too dry, and if this rolling is followed, in one
or two days, with a light harrow to develop a thin mulch,
it will check the surface evaporation without destroying
the good capillary connections produced by the rolling.

190. Puddled Soils.—All soils when completely or
nearly saturated with moisture become very plastic, and
when they are worked under these conditions the water and
air are crowded out of the larger interspaces and the soil
become much more compact. This is especially true of the
adhesive clayey soils whose particles, after such treatment,
become so firmly united as to develop into obstinate clods
so injurious to good tilth, Great care should always be
taken not to work soils when they are tooswet. The roller
should never be used when the soil will adhere to its sur-
face.

191. Advantages of a Warm Soil.—The advantages of a
warm soil are several, and may be briefly stated as follows:

1. Soil ingredients are more soluble in warm than in
cold water. ;

2. Root absorption is more rapid at warm than at cold
temperatures.

3. Germination is more rapid at moderately high than at
low temperatures.

4, Nitrification takes place most rapidly at about 90° F.

It is a general law with all living beings that their vital
processes can go on normally only within certain limits of
temperature, and the range is usually a comparatively
narrow one.

124

In our own case a change of a few degrees above or be-
low 98° F. in the body, as a whole, produces very serious
disturbances; and while these ranges are larger with
plants, yet they are not so wide but that the bounds may
frequently be crossed.

192. Best Soil Temperature in Certain Cases. —
Haberlandt found that the germination of wheat, rye, oats
and flax is best at 77° to 87.8° F., and that corn and pump-
kins germinate best between 92° and 101° F. He found,
for example, that when corn germinated in three days at
a soil temperature of 65.3° F., it required 11 days to ger-
minate at 51° F., and while oats germinated in two days
at a temperature of 65.3° F., 7 days were required when
the temperature was 41° F.

Sachs found that tobacco and pumpkin plants wilted
when the soil temperature fell much below 55° F., on ac-
count of a too slow root absorption, It is found that the
“mother of petre” develops niter at an appreciable rate
only above a temperature of 54° F., that its maximum
power is manifested at 98° F., and that at 113° F. its
power is less strong than at 59° F.

193. Control of Soil Temperature.— The tempera-
ture of soils may be increased in several ways as follows:
By diminishing the water capacity.

By diminishing the water content.

By diminishing the surface evaporation. 125.
By smoothing the surface.

By means of fermenting manures.

. By increasing percolation.

It has been shown, 122 and 125, that diminishing the
water in soil and lessening the surface evaporation favors,
in a marked degree, the production of high soil tempera-
_tures, while the reverse conditions tend in the opposite di-
VTeCELON,

Smoothing the surface, as in the case of rolling, has a
very appreciable effect in raising the soil temperature.
The results observed in a special case are given in Fig.
48. It will be observed that the air temperature over the
unrolled ground is higher than it is over the rolled, which
shows that this soil must be losing heat faster; and since
both surfaces must have been feceiving the same amounts
from the sun, it is plain that if the air is warmed more
over the unrolled ground the soil itself must be warmed less,

o> OUR wo bo

125

The air receives more heat from the unrolled ground for

two reasons.
1. Its many lumps present a much greater contact sur-

face.
2. The lumps being dry become warmer at the surface

than the more moist rolled soil.

| Time. |5~6 AM] | 42P Mn, || S-6 AM.
ro) = SIV

Warm Air

&
~
x
§
s

Ai 3 inches Z eee ENA OP Oe 3

5h Es = = 3 z= ra
| Sol , gern
Jemp, Ground Ralled. Ground hot Rolle d.

Fig. 48.

Showing differences of temperature of rolled and unrolled soil and associated air
temperatures.

Further than this, the lumps, being in poor connection
with the soil below, conduct their heat slowly downward,
while at the same time they shade the lower soil; and by
exposing a very large surface to the sky they cool rapidly
by radiation. ;

The measured differences of soil temperature due to this
cause have been as high as 6.5° to 10° F., the lower figure
having been observed at a depth of three inches and the
higher at 1.5 inches.

The heating effect of fermenting manures in the soil has
been observed to produce a rise in temperature of nearly 1° F.

In the case of well drained soil the percolation of warm
summer rains often carries rapidly and deeply into the
soil considerable heat and thus raises the temperature di-
rectly, and as this water must evaporate more slowly from
the drained soil, if at all, than from the undrained, it is
not cooled as much as it might have been had _ percolation
not occurred, thus leaving all the water to evaporate in a
short time.

126

194. Effect of Deep and Shallow Cultivation on
Soil Temperature.—Land cultivated three inches deep
does not warm so rapidly nor cool so quickly as when cul-
tivated to a less depth. I have found the following differ-
ences in cornfields cultivated 1.5 and 3 inches deep.

ist ft. 2ndft. asrdft. 4th ft.

1.5 inches deep........ 72.85° F. -70.88° F. €68.93° ¥. 65.94° P,
3 inches deep........ 72.45 10,22 67 .80 64.81
Differences. 23225 << .40 .66 1.13 13

Sudden changes in soil temperature tend to dry the soil
by expanding the air it contains, causing it to press upon
the deeper soil-water, forcing it deeper into the ground or
out into drainage channels. But a deep mulch diminishes
these sudden changes and hence saves some soil moisture
in this manner.

IMPLEMENTS OF TILLAGE

195. The Plow.—Foremost among the implements of
tillage unquestionably must be placed the plow. Historic-
ally, it is probably one of the oldest of farm tools, and
when viewed from the standpoint of evolution no instru-
ment has advanced more slowly or has been changed more
profoundly. It has grown from a natural fork formed by
the branches of a tree, as depicted on an ancient monu-
ment in Asia Minor, with the shorter limb simply sharp
ened and laboriously guided and awkwardly drawn through
the soil by the longer arm, to our present almost self
guiding twisted wedge of hardened steel susceptible of an
extreme polish.

196. The Work Done by a Plow.—The mechanical
principles which do or should dictate the construction of a
plow can be most easily comprehended when a clear notion
of the work a plow is expected to perform is first in mind.
Speaking simply of the sod and stubble plows, the first has
two functions: :

1. A cutting function.

2. An inverting function.

The stubble plow has three functions:

1. A cutting function.

2. A pulverizing function.

3. An inverting function.

With both plows the cutting is required in two planes,
one vertical and the other horizontal, to separate a furrow-
slice of the desired width and depth. The inversion of the fur-
row-slice, required in both cases, necessitates first a lift-
ing of the slice and then a rolling of it to one side, bottom
up. The pulverizing of the furrow-slice is most simply
done by bending the slice upon itself more or less abruptly
and then dropping it suddenly upon the ground.

MTT TA i

130

197. The Mechanical Principles of Plows.—The
plows under consideration are sliding three-sided wedges
having one horizontal plane face, called the sole; one ver-
tical plane face, called the /and-side, and a third twisted
and oblique face, one portion of which is called the share
and the other the mold-board. The two lines formed by the
meeting of the twisted oblique face with the land-side and
with the sole are cutting edges. This wedge is simply
shoved through the ground by a force applied to the
standard through the plow-beam, and is guided in its
course by a pair of levers in the form of handles.

A study of Figs. 49 to 54 will show that in these types
of plows, the cutting edges are very oblique to the direc-
tions in which they move, and that the obliquity is great-
est in the breaking type. It will also be seen that the
strong difference between the elevating and inverting sur-
faces of mold-boards, in these plows, consists in the steep-
ness of the inclined surface and the abruptness of the
twist in them, these being least abrupt in the breaking
plow, Fig. 54, and most abrupt in the full stubble, Fig. 49.

198. Advantage of Oblique Cutting Edges. — There
are several conditions which have led to placing the cut-
ting edges of plows oblique to the direction in which they
are drawn.

1. The shin, coulter and share free themselves from
roots, stubble and grass more perfectly.

2. The shin, coulter and share require less power to cut
roots.

3. The plow enters the ground more easily and runs
more steadily.

4. There is less friction of the furrow slice on the in-
verting surface.

When the coulter is placed with its cutting edge in a
nearly vertical attitude straw and roots tend to double
around the edge and clog under the beam, increasing the
draft and tending to draw the plow out of the ground. If
the coulter is dull and the roots are lorig and tough, they
fold over the edge and thus increase the draft by making
the edge in the soil thicker. When the cutting edge is
made to incline backward the roots tend to slide upward
and are severed by a partially drawing cut, and this re-
quires a less intense power than the straight chisel thrust.

The obliquity of the share, particularly in the sod plow

131

where a large part of its work consists in cutting roots,
materially lessens the draught by bringing a drawing cut
upon the roots by forcing them sidewise in its wedging
action and drawing the cutting edge across them while
they are under tension.

When hard spots in the furrow-slice are to be cut through
the more oblique the share is the greater distance will the
horses travel before it is cut off, and as the resistance is
overcome in a longer time less power is required per sec-
ond. Of course so much work must be done in plowing a
given length of furrow, but the oblique share tends to de-
velop an even, steady pull all the time, while the less ob-
lique form allows the inequalities of the soil to develop an
irregular draft which is more wasteful. It is, in effect,
like the triangular sections in a mowing machine, which
allow the horses to be cutting all the time.

199. Function of the Land-side.—The land-side is
made necessary by the inequalities of the soil and the tend-
ency of the horses to vary their course from a straight
line. When the oblique share is brought against a more
resisting spot of soil, a root or a small pebble, were it
not for the land-side the plow would run too far to land
and the furrow would become crooked. This side pressure
developed by the share produces friction between the land-
side and the edge of the furrow and the land-side should,
therefore, be of such a character as to move most easily
under this friction.

200. The Line of Draft.—There is a certain point, A,
Fig. 55, in the mold-board of the plow, to which if the
horses could be attached the plow would “swim free” in
the soil; and the attachment of the team to the bridle, B,
ot the plow should be in such a position that the point of
attachment, D, of the traces to the harness, shall lie in

the same plane with A, as represented by the line ABD.

If the attachment to the bridle is made at © the draft of
the team will draw the plow more deeply into the ground;
and should it be at some point below B, or, what would
amount to the same thing, should the horses be hitched
shorter, the draft would tend to run the plow out of the
ground. Not only is it important to adjust the plow so
that it will “swim free” vertically, but it should likewise
be adjusted to “swim free” from right to left. When this

132

is done, a properly constructed plow will almost hold itself
and will then move with the least possible draft.

If the plow requires any considerable power to be ap-
plied to the handles in guiding it, no matter in what di-
rection, not only is the work harder for the man, but the
draft is harder on the team and at the same time the plow
is wearing out more rapidly. So, too, the man who care-
lessly holds his plow, allowing it to waver from side to
side and run shallow and deep, is making not only more
work for himself and for his team, but is unnecessarily
wearing out his plow and at the same time producing a
seed-bed which will necessarily yield a smaller crop.

201. Draft of the Plow.— The records we have, thus
far, bearing upon the draft of plows are, in many respects,
very unsatisfactory, owing partly to inherent difficulties
in making measurements which represent the actual re-
sistance of the soil to the plow, partially because of unre-
liable methods of measurement, and again because the
varying percentage of water in soil greatly modifies its
plasticity and its weight.

Mr. Pusey, in 1840, in England, made some extended
trials of the draft of plows in soils of different kinds, and
the figures below show the average resu.ts ot trials with
ten plows, the total mean draft being given and also the
draft in pounds per square inch of a cross-section of the
furrows plowed:

-— ="

a

133

No.of Sizeof Draft. Draft per

Plows. furrow. sq. in.
Sipe SAMO. oi PTs eo ener 10 5x9 927 lbs. 5.04 lbs.
SENT Boek cE 1 Rg greg 10 5x9 250 8 Bp, =
PPE EENINC,. 2-5/5 Sere cs ce Ctemte ae ehele 10 5x9 DO eters fs
Peaeath SOI Gc. 2 eats ena as oc 10 5x9 AA. EY Oe
WRN CUA. oo 2 Scien sine weet es 10 5x Hols) 14. Gon
Sandy loam (J. C. Morton)..... 5 6x9 Bob. 10a
Stiff clay loam (N. Y. 1850)..... 14 7x10 AOI See

Prof. J. W. Sanborn has made extended trials of plows
recently in Missouri and Utah. The average of all his
trials, reported in Bulletin No. 2 of Utah Experiment Sta-
tion, is 5.98 pounds per square inch of furrow turned. If
we separate these trials historically we get, by leaving
the clay out of the English trials:

English trials, 1840, draft per sq. in. 7.41 lbs.
American trials, 1850, draft per sq. in. 5.81 lbs.
American trials, 1890, draft per sq. in. 5.98 lbs.

Both English and American experiments agree in show-
ing a decrease of power per square inch with increase of
width of furrow when the depth remains the same; but
this statement should not be construed as saying that a
wide furrow can be plowed with less total draft than a
narrow one.

The effect of depth on the draft is not so clearly shown
by the experiments on record, but they appear to indicate
an increase of power, per square inch, required with in-
crease of depth.

202. Effect of the Beam-wheel on the Draft of the
Plow. — If the wheel under the beam of the plow is so ad-
justed in height as not to bring the attachment of the horses
to the plow-bridle above the line of draft there is found a
material lessening of the draft of the plow with its use.

The reduction of the draft is occasioned by the more even

running of the plow, making it unnecessary for the plow-
man to be alternately pressing down upon the handles or
raising them, in order to maintain the desired depth of
furrow. If the wheel is so high as to bring the line of
draft in the condition represented by the line ACD, Fig.
55, a part of the power of the team is expended in produ-
cing pressure downward upon the wheel while the full re-
sistance of the plow still remains to be overcome. The
proper adjustment of this wheel is secured when it simply
rolls on even ground without carrying weight; when in

134

this condition it» will prevent the plow from entering too
deeply into the less resisting soils, and will act to force it
deeper into the harder portions.

°203. Draft of Sulky Plows.-— It ts generally claimed
by plow manufacturers that sulky plows are of lighter
draft,*‘relatively, than the free-swimming types, the claim
being based upon the assumption that the friction of the
sole and landside are transferred to the well-oiled axles of
the wheels and a rolling resistance secured instead of a
sliding one, which ordinarily, on bare ground, is much
less. The few records of trials we have seen do not ap-
‘ pear to show a material difference in the draft. There
seems to be no good reason, however, why a sulky plow,
when properly hung and with the line of the draft so ad-
justed that the power of the horses is not converted into a
downward pressure upon the wheels, should not lessen the
draft, and especially in the gang types. If a plow of the
requisite strength could be made’ so light that the up-
ward draft against the furrow-slice were sufficient to take
the weight entirely from the ground, and if the adjust-
ment for landing were perfect, there would remain only the
friction of the furrow-slice itself. In such a case the only
work left for wheels would be such as has been described
for the beam-wheel of the walking plow, but such a condi-
tion appears practically impossible.

204. Effect of Coulters on the Draft of Plows. —The
use of the coulter is chiefly confined to sod plowing, and in
this work it is simply indispensable in securing a proper
furrow-slice where there is any considerable turf. The
early English trials, and those of Gould, in New York, in-
dicate a saving of power by their use; but Professor San-
born, through his Missouri and Utah experiments, comes to
the conclusion that they increase the draft from 10 to 15
per cent. and advises farmers to dispense with them. This
position is surprising, in the face of general practice, and
I believe untenable. When the coulter is very thick, dull
and set in an improper place or attitude it will necessari-
ly increase the draft.

If the coulter is thick and set ahead of the lifting action
of the plow-point, and especially if it is dull, it offers a
large resistance by being forced to compress the soil and
cut the roots at the greatest disadvantage; but if it is so
placed, in the rear of the point, as to do its cutting and

t

13%

side-wedging above the place where the point and share
are lifting and cutting, the two wedging and cutting bodies
mutually assist each other; the roots in both cases are then
severed while under strain and to a greater extent, with a
drawing cut and, I believe, with an appreciable saving of
power. So, too, when the wheel coulter is dull and set far
forward, it becomes necessary to hitch to the plow-bridle
at so high a point, in order to force the coulter into the
ground, that there may be loss of power as there may be
with a beam-wheel; but when this form of coulter is sharp
and set well back where the beam of the plow acts with
leverage to force the coulter through the sod and where the
cutting occurs under the lifting strain of the point and
mold-board, there can but be a lessening of draft in tough
sod.

205. The Scouring of Plows.—There are certain soils
whose texture and composition are such that the most per-
fect plow surfaces fail to shed them completely. The par-
ticles of most such soils are extremely minute, 151, and
often contain much silica. In Fig. 53 is represented a type
of one of the most successful plows for this class of soils.
In form it resembles the breaking plow, and the surface of
the mold-board is very hard and susceptible of a high polish.
The hard surface in these plows appears to be demanded to
prevent it from becoming roughened by the scratching of
hard soil particles; the less abrupt curvature of the mold-
board diminishes the surface pressure and thus the liability
to scratching, while the fine polish furnishes the fewest
and shallowest depressions into which the extremely mi-
nute particles can be wedged by the pressure. It is a mat-
ter of great moment, in the care of such plows, that they
be kept from rusting, because this quickly destroys the
necessary polish.

206. Pulverizing Function of Plows.— The stubble
plows are constructed so as to pulverize the soil at the
time it is being overturned. This action of the plow can
best be appreciated by taking a thick bunch of paper, like
the leaves of a book, and bending it abruptly upon itself;
when this is done it will be observed that the leaves slide
upon one another, and through a greater distance the more
abruptly the bending takes place. The steep mold-board
of the full-stubble plow shown in Fig. 49 has this shearing

136

action upon the soil as one of its chief functions and this
necessarily increases its draft.

In selecting plows for the naturally mellow soils where
pulverizing is unessential, the type represented in Fig. 52
should be taken, as, other conditions being the same, its
draft will be lighter.

207. Care of Plows. —Next in importance to having
good tools to work with is the keeping of them in proper
working trim. It is extremely wasteful to purchase good
tools and convert them into poor ones by lack of care, and
in no case do these remarks apply with greater force than
to plows.

The John Deere Co., in their catalogues, make some re-
marks regarding the care of plow-shares, and through
their kindness I am permitted to use some of their illus-
trations. Figs. 56 and’57 represent a proper and an im-
proper form Tor point. A dull point may increase the

cto... Ee

il
SSS

eon

ier
in fiat

co
Sl

ne d6.

draft of a plow six to eight per cent. and more, besides
necessitating poorer work. The tendency of wear on the
point is to change it from the sharp, slightly dipping form
represented in Fig. 56 to the blunt up-turned form shown
In Pig Or:

Fig. 57.

The heel of the share, like the point, is especially sub-
ject to wear, and soon comes into an improper shape.
In case the ground is hard and dry, as is often the case
during fall plowing, the share-heel requires a set shown
in Fig. 58, dipping decidedly downward, preventing it
from lifting out of the ground and tipping the plow to
land. On the other hand, when the soil is mellow and

157

damp, the heel of the share should be given a more hori-
zontal attitude, as shown in Fig. 59, to prevent it from
sucking too deeply into the ground, and necessitating a

2

yi eee

ccc ccc
Fig. 58.

steady pressure at the handles toward the land. It should
be remembered that whenever the plow requires a steady
pressure at the handles in any direction in guiding it,
there is a defect somewhere that should be remedied; be-
cause a pressure of only a few pounds on the long handles,
working as levers, is transformed into friction, increasing
the draft on the team and the wear on the plow.

In taking the share to the shop for setting or sharpen-
ing, the land-side should accompany it, so the blacksmith
may have a guide in giving the proper set to it.

208. The Subsoil Plow. —One type of this instrument
is represented in Fig. 60. Its function is nominally to
loosen the ground to a greater depth than is practicable
with the ordinary plow, thus securing deeper tillage with-
out burying the humus-bearing soil too deeply below the
suriace. Its use requires great discretion, otherwise more
harm than good may result from it. Better aeration, bet-
ter drainage, deeper development of roots and less suffer-

ing from drought are advantages claimed for its use. For

large yields of root crops a deep loose soil is indispensable,
and one necessity for this is found in the fact that the
thick roots require so much space which can only be se-
cured by forcing the soil aside. There is great danger of
puddling the soil in the use of the subsoil plow, because

the surface may appear dry enough to work when the sub-
soil is too wet.

Fig. 60.

209. The Harrow.— As implements of tillage, har-
rows are used to secure several quite distinct ends:

1. To produce a shallow seed-bed.

2. To dry the soil preparatory to seeding.

3. To render the surface of the ground more even.

4. To pulverize the soil and secure a more even texture.

5. To cover seed.

6. To destroy young weeds.

7. To work manure into the surface soil.

8. To aerate the soil.

9. To check evaporation by developing a soil-mulch,

According as one or another of these ends is to be se-
cured, the character of the harrow should be different. In
Figs. 61, 62 and 63 are represented three of the strongly
marked types of harrows.

210. The Dise Harrow.— This harrow, Fig. 61, is
distinctly a seed-bed-preparing and soil-drying too] and,
in its adjustable types, may be made to work to a remark-
able depth in fall plowing and in corn ground in the
spring. An immense amount of work can be done with it
where there is the necessary power to move it, which, al-
though large when running deep, is really small- when
compared with the amount of soil moved. Its rolling,
concave, thin discs, when set obliquely, enable it to enter

fag

the soil and overturn it with less compression and rela-
tively less friction than almost any other tool. As a first
tool to loosen the soil and dry it rapidly it does excellent
work. It is also very effective in pulverizing sod and may
be used to advantage in covering sowed peas. This is also
an excellent tool to work in a surface dressing of manure.

211. The Acme Harrow.— This tool, so far as its ef-
fects upon the soil are concerned, is like the disc harrow,
but while it slices the soil and turns it over it does so with
more compression, more friction and less movement. Like
the disc harrow it can be used to cut sod, but has a greater
tendency to drag them out of place.

140

212. The Tooth Harrows.—These tools in their great
variety of forms, are best adapted to secure the ends 3 to
9 named in 209. The heavier types are, however, fair
drying tools, especially on the more mellow soils, and in
such situations, too, they give a sufficiently deep seed-bed
for most of the small grains. To kill weeds when just
emerging from the ground, in potato and corn fields, and

1}

j

Fig. 63.
in developing a light mulch to retard evaporation from the
soil, there is no tool more effective or rapid in its execu-
tion than the light, many-toothed harrows.

213. Cultivators.—We have much to learn yet in re-
gard to the real objects to be secured by summer tillage
or cultivation. Three chief objects appear to control pres-
ent practice; they are:

1. To kill weeds.

2. To lessen surface evaporation.

3. To cover the roots of plants more deeply.

I believe we shall find, however, that one of the most
important functions is

4, To secure better soil aeration.

When we remember that good aeration, plenty of moist-
ure, and a warm temperature are among the essentials
both to soil nitrification and root-growth, and that nature’s
ways of soil aeration are decidedly interfered with by our
methods of tillage, it seems but natural that some equiva-
lent should be supplied by our manner of working soil.

If soil aeration is conducive to its fertility it would appear
to be rational practice with corn, potatoes and similar
crops to adopt deep tillage during the early portion of the
season before the roots have come to occupy the soil, to
facilitate nitrification, and then to adopt purely surface

141

tillage, to check evaporation and kill weeds after the roots
are well developed.

214. The Roller.— The firming of land with the roller,
if used on the soil in the proper condition, has several
beneficial effects:

1. It makes the soil warmer, 193.

2. It increases the capacity of the surface soil for water
and its capillary power, 189.

3. In cases of broadcast seeding, the germination of seeds
is more rapid and more complete on rolled than on unrolled
ground.

4. It is maintained by many that larger yields are se-
cured from rolling land.

In cases where the soil is too damp and cold the alter-
nate use of the harrow and the roller will hasten its drying

‘very much. Many farmers advocate the use of the roller

on lands sowed to small grains after the grain is up, es-
pecially if a drought is threatened, the advantage claimed
being the formation of a mulch by crushing the surface
inequalities. It is one of those practices, however, which
demand careful study and experiment to ascertain to what
the advantage, if any, is due.

FARM DRAINAGE.

(Parts of a paper prepared for the Arkansas Geological Sur-
vey, 1891.)

The last twenty years have witnessed a large deve.op-
ment of the drainage method of land improvement in this
country, and in no state, perhaps, has this growth been
greater than in Illinois, where there are many exten-
sive tracts of very flat lands possessing no sufficiently
deep water-ways to furnish adequate outlets for drainage
systems. Notwithstanding these great natural obstacles
to the improvement of land by drainage, the citizens in
various sections of the state, by combining their energies,
have constructed extensive ditches which now serve as
outlets to the drains they desired to lay. One of these
systems, in Mason and Tazewell counties, begun in 1883
and completed in 1886, has a main ditch 17} miles long,
with a width of 30 to 60 feet at the top and a depth of
8 to 11 feet; while leading into this main channel there
are 5 laterals averaging 30 feet wide at the top and from
7 to 9 feet deep, the whole system embracing some 70
miles of open ditch.

A clearer idea of the character and magnitude of some
of these drainage systems may be gained from an inspec-
tion of Fig. 1, where the double lines indicate open ditches
and the single ones drain tiles, many of which it was
found necessary to lay very nearly level. This system was
begun in 1881 and completed in 1884, and its effect upon
the total yield of grain of all kinds is stated by Prof.
Baker as follows: ,

Total yield Of grain.in 186i" 3 ica ees Sees ee 26,057 bu.
Total yield: of ram in A882 oF 2G. eee eee & 58,647 bu.
Total yield: of; graininess Fiat ketene eerie = 92.360 bu.
‘Potalyieldso&- erat in: Lele ec icascte a temis ee ake 113,660 bu.
Potalyield jor grains ISSh ee acs iA ae reente 122,160 bu.*
Total yield of: grain im 1S86. oes ee ors 202,000 bu.

*400 acres of corn destroyed by a water spout.

143

Let these cases serve to indicate the attention which, at
present, is being given to the improvement of farm lands
by drainage in some sections of this country.

Fig. 0.

Plan of the drainage of Jands of the Ill. Agr. Co., Rontoul, Ills. After Prof. I. O.
Baker. The smal est squares represent 40 acres; double lines show open ditches;
single lines drain tile.

Necessity of drainage.— It should be understood that
no lands will produce other than swamp vegetation unless
they are more or less perfectly drained, and this is due to
the fact that imperfect drainage prevents the biologic
processes in the soil, which are necessary to cultivated
crops, from going forward normally because then:

1. The soil temperature is maintained too low.

2. There is inadequate soil ventilation.

_ 3. There is insufficient soil space in which the roots can
perform their functions.

Imperfect drainage of cultivated lands works disadvan-
tageously in two other ways:

1. By preventing early seeding, thus shortening the
growing season.

2. By increasing the labor of. tillage and at the same

, time decreasing the time in which it can be performed.
So thoroughly does the lack of drainage insure the diffi-
culties here enumerated and so effectively does perfect

144

drainage avert them that it becomes of prime importance
to realize the full significance of each.

Importance of the right soil temperature. — It is a
general law with all types of life that their vital processes
can go on normally only within certain narrow limits of
temperature. In our own case deviation of the general
temperature of the body a few degrees either side of 98.8°
F. results in the most serious disturbances. While vege-
tal life is less sensitive, as a rule, to small changes of
temperature than is animal life, yet no physiological law
is more surely established than that a fluctuation of tem-
perature above or below that normal to a given plant im-
pedes its growth. Haberlandt found, for example, that the
germination of wheat, rye, oats, and flax goes forward
most rapidly at from 77° to 87.8° F., and that corn
and pumpkins germinate best between 92° and 101° F. He
found that when corn germinated in three days at a tem-
perature of 65.39 F., it required 11 days to germinate
under a temperature of 51° F., and that when oats ger-
minated in two days at.a temperature of 65.5° F., it re-
quired seven days when the temperature fell to 41° F.

It has been shown that the “mother of petre” or nitric fer-
ment (Micoderma aceti) ceases to produce nitric acid from
humus at a temperature of 41° F.; that its action only be-
comes appreciable at 59° F., that it is most vigorous at
98° F., accomplishing in a short time results for which,
under other conditions, months would be required; but at
113° F. the activity again falls below that at 59° F.

Sachs found that, with plenty of moisture in the soil,
tobacco and pumpkin plants wilted at night, because of too
slow absorption by the roots, when the temperature fell
much below 55° F.

The advantages of warm soil temperatures are not wholly
due to their direct physiological effects upon the life pro-
cesses going on there, so essential to large crops, but some
of them are purely physical and chemical, but nevertheless
indirectly important and the several advantages of a warm
soil may be briefly stated as follows:

1. The soil ingredients of plant food are more soluble
in the soil-water thus enabling it to carry more food to the
roots.

2. The chemical reactions are more rapid in the produc-
tion of soluble minerals for the water to take up.

*

sie

345

3. The rate of diffusion of the newly forming substances
is more rapid and this hastens the chemical action.

4. The rate of root absorption is greater, making a more
rapid growth possible.

5. The rate of germination is more rapid and more vig-
orous, thus securing an earlier start and stronger plants.

6. The rate of nitrification is more rapid, thus supply-
ing a large quantity of an important plant food.

Influence of drainage on soil temperatures.— It
is a fact of common experience that a wet soil has a lower
temperature than the same soil similarly conditioned but
dryer. The following table gives a series of temperature
records taken by the writer the last of April, 1884, at
River Falls, Wis., two inches below the surface of the
soil on undrained and on well drained land.

Temp. of | Temp. of

Date. Time. Condition of the | Temp | grained | undrained| Diff.
weather. of air. soil. soil.
eS —— ee es —— . eee. ees ee —_——_— | Oooo OO) OSes |
Apr. 24. | 3:30to4P.M| Cloudy with brisk
east wind .. 60° F. 66.5° 54° 12) 5°
Apr. 25..| 3t03:30P.M| Cloudy with brisk
east wind .. 64° F. 7C° 58° 12°
Apr. 26. | 1:30to2P.M| Clouty, rain all
; the forenoon...| 45° F. 50° 44° 6°
Apr. 27..| 1:30to2 P.M} Cloudy and sun-
shine; wind
S. W., brisk 5ae) By 55° 50.75° 4.25°
Apr. 28..| 7to8:30A.Mj| Cloudy and sun-
shine; wind
N. W., brisk 45° BF. 47° 44.5° 2.5°
Apr. 29..| 4:30to5A.M| Clear; ground a

little frozen 34° BF. 35° 34 5° {be

—

It should be noted in connection with this table, that
the differences of temperature which were observed in favor
of the well drained soil occurred under conditions of cloudy
and rainy weather when these differences should, naturally,
be the smallest. It will also be seen that a difference per-
sisted through the entire night, and that the temperature
of the undrained soil did not reach the point at which the
nitre gems produce appreciable quantities of nitric acid.

To understand why the presence of water in the soil re-
tards the rise of its temperature two physical principles
require consideration:

1. A larger number of heat units must enter a given
weight of water to raise its temperature one degree than

146

is required to enter an equal weight of any soil to produce
an equal change of temperature in it, the relative changes,
in certain cases, being as stated below:

100 heat units will raise 100 lbs. of water at 32° F. to 33° F.
100 heat units will raise 100 lbs. of dry sand at 32° F. to 41.92° F.
100 heat units will raise 100 lbs. of dry clay at 32° F. to 39.28° F.

It is evident, from these figures, that undrained soils
must warm more slowly under the same sunshine than cor-
responding well drained sollss will «Ve oe aa ce

2. To evaporate one pound of water, under mean atmos-
pheric pressure without change of temperature, requires
the expenditure of 966.6 heat units and in this fact is to be
sought the chief cause of low temperature observed in wet
soils. If two similar thermometers are taken and the bulb
of one covered with a film of water and then both swung
at arms length to and fro in a drying atmosphere the ther-
mometer with the wetted bulb will be found to read several
degrees below its companion, if the reading is taken before
all the water has been evaporated, and the difference in
temperature may be found, with dry, warm air, greater
than 30° F.;'thus demonstrating the cooling effect of
evaporating water.

When a pound of water is evaporated from a cubic foot
of soil it carries with it heat enough to lower its mean
temperature, if saturated sand, 32.8° F.. and if saturated
clay loam 28.8°.; and in this connection it should be
abundantly evident that draining land of the water which
it cannot hold by capillary power will permit it to attain
a higher temperature.

There is still another manner in which thorough drainage
tends to permit higher soil temperatures to exist. It is
this: As the season advances and the surface foot of soil
becomes dry, its upper portion especially becomes very hot,
often above 100° F., and in such cases, when heavy rains
fall upon porous, well drained soil to such an extent that
percolation takes place, the warmth of the surface soil is
imparted to the percolating water and carried by it deeply
into the ground thus increasing the temperature of the soil
which is occupied by the deeper roots: but in undrained
soil this percolation is always less extended and less fre-
quent.

eR te Cte hae 7
ida a te 88 |
:

147

Importance of soil ventilation.—The necessity for a
considerable circulation of air in soils maintaining growing
vegetation is now generally recognized and the demands
for it are three-fold: :

1. To supply free oxygen to be consumed in the soil,

a. In the respiration of germinating seeds.

b. In the respiration of growing roots.

c. In the respiration of nitric acid germs.

d. In the respiration of free-nitrogen-fixing germs.
e. In the respiration of manure-fermenting germs,
f. In simple chemical oxidations.

2. To supply free nitrogen to be consumed and fixed for
the use of plants by free-nitrogen-fixing germs.

3. To remove carbon dioxide, liberated in the soil, thus
preventing excessive dilution of the oxygen and nitrogen.

It has been abundantly demonstrated that when free
oxygen is completely excluded from seeds, placed under
otherwise normal conditions for germination, growth does
not take place; if the germination is allowed to commence
and then the oxygen is excluded growth ceases. Germi-
nation will, indeed, take place in an atmosphere very poor
in oxygen but it has been shown that when the percentage
is reduced to zs of the normal amount the rate of growth
is retarded and sickly plants are likely to result.

Practical experience teaches that when a soil, bearing
other than swamp vegetation, is flooded with water or even
if it is kept long in a fully saturated condition the plants
soon sicken and die and this too when they are in full leaf
and abundantly supplied with nourishment, sunshine and
warmth. The difficulty is the lack of root breathing; oxy-
gen in sufficient quantity to maintain life cannot reach
them and actual suffocation occurs. It may be urged that
this explanation of the death of plants under these condi-
tions is disproved by the floating gardens of the Chinese
which consist of basket work made strong enough to carry
a layer of soil in which the crops grow with their roots
constantly immersed in tke water. The two cases, how-
ever are far from being parallel. In the cases of water
culture the free water is subject to strong convection and
other currents which bring the oxygen absorbed by the
water constantly to the roots of the plants; but in the soil
with less than half the volume of water per cubic foot of space
convection currents are wholly prevented, while simple dif-

148

fusion from the atmosphere downward into the soil is nec-
essarily much slower than it is in free water.

The nitrification of soils, so essential to their fertility,
and effected, as we have seen, by living germs, requires
an ample supply of oxygen; so large is this demand that,
when salt petre’ farming was practiced in parts of Hurope
the soil was kept well aerated by frequent stirring and by
the introduction of gratings to increase the air spaces and
promote better ventilation of the niter beds.

While we have as yet less positive knowledge in regard
to the respiratory needs of the free-nitrogen-fixing germs,
which have been shown to inhabit tubercles on the roots of
liguminous and other plants, and whose agricultural im-
portance is now coming rapidly into recognition, there is
no reason to doubt the beneficial effects of a well aerated
soil upon them. They -must certainly be supplied with
atmospheric nitrogen which it is their function to fix and
turn over to the hosts upon which they live.

In regard to the manure-fermenting germs, we have suf-
ficient evidence of the need of good ventilation in the strong
heating of the well aerated heaps of horse-manure, when
contrasted with the smaller amount of fermentation which
takes place in the close cow dung free from litter.

There are many purely chemical reactions essential to
soil production and soil fertility which demand a certain
measure of free oxygen for their continuance. Then again,
not only must oxygen and nitrogen be introduced into fer-
_tile soils, but the carbon-dioxide liberated by the processes
of fermentation and by the decomposition of bicarbonates
brought up by capillary soil waters, must be disposed of in
order that it may not prevent the entrance of oxygen and
nitrogen or make them too dilute for respiratory purposes.

Influence of drainage on soil ventilation. — Ample
drainage facilitates the aeration of soils in three chief ways:

1. By drawing off the water from all non-capillary spaces
in the soil, thus not only permitting but forcing, by down.
ward suction, the air to take its place.

2. By both permitting and inducing earth-worms and
other burrowing animals to extend their channels more
deeply into the ground.

3. By allowing the roots of plants to grow more deeply
where, after decaying, they te passages into which the
air may penetrate.

ee ee ee ee ee ee ae eee a ee
‘tel . - 5 7 rz . \
, d i ? :

149

All soils, when not saturated with water, are subject to
a small but irregular type of breathing due to expansions
and contractions of the soil-air resulting from changes of
atmospheric pressure and of soil temperature. The
amounts of air put out of and taken into the soil by the
maximum daily temperature changes can not much exceed
22 cu. in. to the square foot of soil surface and probably
average less than one half of this during the growing sea-
son, and yet these effects are larger than those due to
barometric changes. It is evident, therefore, that the chief
renovation of soil-air must result from the process of dif-
fusion which must necessarily be slow under the best of
conditions. I have found by experiments conducted in the
field that saturated clay and black marsh soils are practic-

‘ally impervious to air under a suction of one pound to the

Square inch; it is evident, therefore, that the diffusion of
air must also be very slight under these conditions. But
well drained soils very soon cease to be saturated and a
large amount of space only occupied by air and roots is
developed.

How drainage increases root-room and the amount
of available water.—That draining land to a depth of
three, four or five feet increases the amount of stored water
available to crops appears like a parodoxical statement and
yet it is strictly true. The depth of the root zone is lim-
ited by the downward extent of ample soil ventilation and
this, in turn, by the distance of saturated soil below the
surface. When standing water exists at three feet or less
below the surface the roots of cultivated plants can only
extend to a depth: of sixteen to twenty inches: and when
the root zone is so shallow the water, under the combined
action of the dense net-work of roots and surface evapora-
tion, is withdrawn more rapidly, during dry weather, than
capillary action can supply it from below. The result of
these conditions is the production of a very dry soil into
which the capillary movement is extremely slow even when
standing water is only twelve to eighteen inches below.

* * * * * : * ¥* * * *

When the soil is adequately drained the roots are ex-
tended deeply into it before the moisture is so thoroughly
exhausted and hence a larger amount of stored water be-
comes available, a much larger root-pasturage is secured and

150-

a more equable activity is maintained by all the roots.
But the most important gain as regards moisture, lies in
the fact that the surface soil, is maintained more moist
thus permitting soil nitrification to continue and at the
same time leaving moisture enough about the surface roots
to make the developing fertility available to the crop.
That is, under these conditions the deeper roots, pumping
water from far below the surface relieve the more super-
ficial ones from drawing as much and hence the upper foot
remains more moist than it would had the soil been un-
drained, first because the rate at which water is
removed from it is slower and second because the rate of
capillary flow into it from below is more rapid on account
of its not becoming excessively dry.

Lands likely to be benefited by drainage.—It is a
fortunate coincidence that most of the lands which are
likelv to be improved by artificial drainage become, when
reclaimed in this way, the richest of cultivated fields;
they are so first, because they often receive, through both
surface and underdrainage, much of the fertility developed
on surrounding areas, and second, because they are then
usually provided with what is much more important, a larger
water supply automatically controlled.

The majority of lands, when large areas are considered,
are sufficiently drainéd by natural processes and many in-
indeed are overdrained. Most of those which may be ma-
terially improved by artificial drainage fall under the fol-
lowing heads:

1. All lands where standing soil water is usually found,
at seeding time, not more than four feet below the surface.

A OV ERY, flat lands underlaid, at a depth less than.
four to six feet, with a stratum of highly impervious clay
or rock.

3. Ponds and sloughs generally.

4. Springy hillsides and cold springy lands of all kinds.

It is a fact well proven by practical experience that
many low lands, which require draining in order to bring
them under cultivation, and lying adjacent to higher areas,
become, when so treated, the most productive lands of the
locality, and while there are several conditions which
tend to render them so, the chief one is the water supply
naturally provided by the upward tendency of it under the
low lands coming from the supply of stored water in the

151

soil of the surrounding higher ground. This is because
the water level being higher, tends to lift, by hydrostatic
pressure, some water up into the soil of the lower fields,
that is to say, the lower fields are supplied from below
with water which falls upon the higher ground.

we te eee -om co eces

; 377 0455 LY): Ye

CET FE Erm mm OED LLL EEL

é GtGt 3-4: CZ TEAS VGLGLVEL MY kis LL

ig Ahe Drab yiggaiadiumy Wp lllil pp
Ls OTT

Showing the geologic structure favorable to natural subirrigation.

: Not all low lands adjacent to high areas are equally sub-
7 ject to the natural subirrigation referred to, for differences
in the structure of the soil necessarily modify the move-
ment of the rain which has entered the ground. The
Structure best suited to the storing of water in the high
lands and the giving of it out gradually to the adjacent
lower areas is represented in Fig. 2 where the surface of
the lower areas is covered to a depth of three to four feet
| with clay soil and subsoil; on the highland this mantle
passes, by degrees, through a porous, sandy and gravelly
clay into a sand and gravel or pure sand of considerable
depth into which the water percolates rapidly, and out of
which it flows laterally with comparative ease toward and
below the adjacent lower areas, This type of geological
structure is very common in many parts of Wisconsin
and other sections of the United States which are heavily
; _ mantled with the deposits of the glacial epoch. The ter-
minal morains of this and other states are water reservoirs
! of great extent and capacity into which the rains sink at
3 once and are there stored under conditions of the least
: possible loss by surface evaporation, to be given out grad-
: ually in restricted but innumerable areas. Heavy rains,
which in other sections are lost to agriculture in destruc-
tive floods, are here safely and economically stored and it
is these very many naturally subirrigated tracts to which

se

152

I wish to call attention as being so promising for the pur-
poses of market gardening and other types of intensive
farming.

Best depth for drains.— From what has been said in
regard to the importance of root-room it is evident that,
where it is possible, tile drains should be placed at a depth
of three to four feet. Inequalities of the surface and the
great increase in cost of digging ditches more than four
feet deep often make it necessary, in order to maintain the
proper grade; to place some portions of the drain nearer
to the surface than three feet, but permanency demands
that the tile should never be laid near enough the surface
to be destroyed by freezing. Indeed the cases should be
very rare where the tile are placed nearer the surface than
2.5 feet. It is often found necessary in draining flat land
to lay the main drains deeper tkan four feet in order to
secure a sufficient fall for the laterals.

Best distance between drains.— The deeper the drains
can be laid and the more open and porous the soil the
oreater may be the distance between the two lines.

SS>S>>SSS—S=—=————==saqS_mq_mEmraumEmE_
————=—BaBOo*OooaaaSSaSSS=
———_—_———S——=_===S==
——S—S—_{___[=_[_{[_[=_[——=_——S—S=
=——————S————=—=——====
st
—$<————————_—]
So S>>S>==
—oaoaaaa————————
SBS SS]

Showing how the distance between drains affects the depth of drainage. With
drains at A and C the surface of the water will be higher at B; but with drains at
A, D and CU thesurface of the water will be more nearly that of the lines A, E, D, F,C.

In many prairie soils and in light loams, where the tile
are laid at a depth of 3.5 feet, very excellent drainage is
secured with the lines placed 100 féet apart, but in the
heavy and stiffer clays and especially where the summer
rains are frequent and heavy 75, 50 and even 40 feet have
sometimes been found necessary. It should be said, how-
ever, that larger distances than 100 feet apart are fre-
quently adopted, sometimes as great even as 220 feet, and
150 feet is a distance often used for general farm drainage
in Illinois. If the drains are too far apart, and especially if

153

they are shallow, there is inadequate drainage midway be-
tween the lines. Why this must be so will be readily seen
from an inspection of Fig. 3, for the closer the soil and the
more distant the drains, the nearer the surface will the
undrained soil approach and the longer will that which is
affected remain too wet.

Hig. 4.
Showing the surface of ground-water between tile drains 48 hours after a
rain-fall of .87 inch.

Since writing the above the actual surface of the ground-
water 48 hours after a rain fall of .87 inches in a tile-
drained field at the Experiment Station which is shown in
Fig. 4, has been observed by the writer. In this instance
the drains are 33 ft. apart and lie in a medium orained
sand overlaid with clay. The height of water above the
tops of the tile, midway between the drains, varied at this
time, between 4 and 12 inches, and the mean rate of rise
was one foot in about 25 ft.; that is to say, in soil of this
character, when the drains are placed 50 ft. apart the
ground-water will stand midway between them 48 hours
after such a rain, 1 ft. nearer the surface than the drains
themselves, and if 100 ft. apart, then 2 ft. nearer the sur-
face. It is evident therefore, that the deeper the drains
are placed, the further apart they may be and that if tiles
are placed 100 ft. apart and 3 ft. deep, the land midway
between the lines would not be sufficiently drained because
then standing water might reach within 12 in. of the sur-
face in parts of the field.

It should not be understood that Fig. 4 represents the
permanent slope of the surface of standing water in the
field in question, for that surface is constantly changing,
and in Fig. 5 is shown just how the surface did change be-
tween the dates given in the cut, the three broken lines

154

representing the levels of the water on three different
dates.

woor-?*

et aed
<= —tain Dra wt

Fig. 5.
Showing change in the level of water between tile drains.

The grade of drains.— Securing a sufficient and
proper fall or grade for lines of tile is one of the most im-
portant problems of practical drainage. As a general rule
it is desirable to secure all the fall that is possible, and
this is especially true for all flat and large areas. The
greater the fall per 100 feet the more rapidly will the
water be removed, the less danger will there be of the tile
becoming clogged with silt and the smaller may be the
tile used. A fall of two inches in 100 feet, one foot in
600 feet or 36 rods, has been found very satisfactory where
the tile have been carefully laid; it is often necessary, if

draining is done at all, to adopt a less steep grade than

this, but higher grades are much safer and more effective
and should be secured where circumstances will permit.
When a particular grade has been decided upon it is a
matter of the greatest importance, in the laying of the
tile, to see that each and every piece is immovably placed
exactly on the grade line. If careless laying of the tile is
tolerated, which results in one section being placed above
the grade line while another falls below it, sediment will
tend to collect in the sags, and if the fall is slight, the
tile small, and the deviation from the grade line nearly
equal to the internal diameter of the tile, ultimate clog-
ging is almost inevitable. It is often absolutely necessary
to lay two or more sections of a line of tile on different
grades, and in such cases it is always best to have~ the
water pass froma less steep to a steeper grade, when this

155

is possible, but when this is impracticable a change to a
larger size of tile on the less steep grade will help to pre-
vent clogging.

The outlet of drains. — The securing of a proper outlet
for a drain is of scarcely less importance than laying the
tile true to grade. In any case where the mouth of the
drain is under stagnant water there is a tendency for the
mouth to become clogged and thus render the whole system
ineffective.

Fig. 6 represents a good and a defective outlet. In very
flat sections like that represented in Fig. 1, proper outlets
can only be secured by the construction of deep open
ditches. Where lateral drains are connected with main
lines, junction tile, represented in Fig. 6, should be used,
and it is important that the angle should be acute up-
stream, otherwise the velocity of the water in the main is
checked, and there is a tendency to clog both the main and
the lateral.

LTT
TILL

Pie dU gallate: Uh 1
A .
\ >
\Y \\\ \

BK . — QW
Ss SNS SN ——— D "AT ps NNN

Fig. 6.

Showing proper and improper outlets of drains. A, proper outlet; B. improper
outlet; C, proper junction of lateral with main drain; D, improper jnoction.

Obstructions to drains.— Where elm, willow, larch or
other water-loving trees are allowed to grow nearer than
75 feet to a drain they are very certain sooner or later to
extend their roots into the tile through the joints and
there branch out into a vast network entirely filling the
tile where, by retaining the silt brought by the water,
they effectually close up the drain. —~ * ij t *

Main drains and laterals.— In draiaing any consider-
able number of acres of land, one or more main drains with
systems of laterals leading into them are required. To
illustrate the manner of distributing and joining, | have
selected an actual case which represents a farm of 80
acres in Northern Illinois which has been drained under

% "S<"—-7 Fee

156

the supervision of Mr. C. G. Elliott, C. E., who describes
the soil as a rich black loam, approaching black muck in
the ponds and flats, underlaid with a yellow clay sub-soil
at a depth of 2.5 feet from the surface. The mains, Fig.
7, have a grade of two inches per 100 feet and the laterals
not less than this and sometimes more. In draining this
land the object was to fit it for growing corn, grass and
grain in all seasons.

SS
=
=~
ms)
~™
x)
1

By Ma
Showing the drainage system on an &0 acre farm in Northern Illinois after C. G.
Elliot, CE. Double lines represent mains; singles lines, iaterals. and the numbers
express the length ot drvins and the size of tile used.

It will be seen that the lateral drains are, where nearest,
150 feet apart; and it should be understood that this sys-
tem is not intended to provide perfect drainage but rather,
as good as would pay a fair interest on the investment
under the returns of general farming. ;

This figure may also serve to show how the sizes of tile
are selected and placed with reference to the amount of
work they are called upon to do.

THE CONSTRUCTION AND VENTILATION OF FARM
BUILDINGS.

(A lecture prepared under the direction of the United States De-
partment of Agriculture, Office of Experiment Stations, for the
exhibit at the World’s Columbian Exposition, 1893.)

In discussing the construction and ventilation of farm
buildings, since there are in fact such great variations in
the details even where the main objects to be attained are
the same, it will conduce to clearness and brevity if atten-
tion be given chiefly to those fundemental principles which
Should govern the construction of all buildings of this
class, whatever may be the specific use for which they are
intended.

FUNDAMENTAL .PRINCIPLES.

The construction of a shelter should in no way ser-
iously interfere with the bodily functions of the animals
housed; a shelter should provide ample ventilation, suffi-
cient light, and the required degree of warmth, cleanliness,
and comfort. The construction and the arrangement of
parts should be such as to reduce the labor of caring for the
animals to the smallest amount consistent with the largest
net profit and should require the smallest first net cost and
the smallest maintenance expense compatible with the

_ necessary accommodations.

THE NEED OF THOROUGH VENTILATION.

Now that farmers are coming to appreciate the advan-
tages of warm shelters for stock and are endeavoring to
provide tight, well built barns, the importance of under-
standing the need of ample ventilation and the best methods
of insuring it becomes very urgent.

The oxygen breathed by ourselves and by our domestic
animals is procured so unconsciously and so inevitably

158

under ordinary conditions that we rarely realize the im
portant part which it plays in the physiological processes
or the large quantity of it which is daily required.

Let me endeavor to impress upon your minds a notion
of the quantity of oxygen used daily by some of our do-
mestic animals. Experiments conducted for the purpose
have indicated that steers consume oxygen at the rate of
13.24 lbs. per every 1,000 lbs. of weight per day; horses
13.5 lbs. and sheep 11.75 lbs. Now airisa very light
substance and only about one-fifth of it is oxygen; neither
ean all of the oxygen contained in the air be removed from it
by the lungs when once breathed, and hence it has been
found that to obtain the 13.24 lbs. of oxygen needed in 24
hours. the 1,000 lb. steer must breathe 2,513 cubic feet of
air; the horse 2,552 cubic feet, and the sheep 2,222 cubic
feet, and these are the volumes of pwre air these animals
must take into and put out of their lungs for each 1,000
lbs. of weight, daily.

Now air once breathed contains less than the normal
proportion of oxygen and is really unfit for the mainte-
nance of animal life unless largely diluted with that which
is pure. This may be demonstrated before your eyes in a
very simple manner. Let me lower this lighted taper into
the jar before you. It burns brightly as it did before; but
now let me replace the air with that from mylungs. On
lowering the taper into it it is at once extinguished. Re-
filling the jar with fresh air the taper again burns
brightly in it, but on breathing into it the taper is again
extinguished, showing that it was by no accident that it
went out before.

Neither man nor his domestic animals can survive in
an atmosphere in which a candle will not burn; it follows,
therefore, from this experiment that air once breathed
should be rapidly removed and replaced by that which is
fresh even to permit life to exist.

Twenty cows should not be housed in a space much
smaller than 28 x 33 sq. ft. and 8 ft. ceilings. These cows
would breathe the volume of air represented by this room
in 3.3 hours: but, as the air once breathed is thrown di-
rectly back into the room so as to dilute the oxygen of the
unbreathed air, it follows that in order that the cows may
have air containing not more than 3.3. per cent. of that
once breathed it must be changed at the rate of 8.8 times

159

each hour. This would be accomplished by a ventilating
shaft 2x2 ft. in section through which the air moved at
the rate of three miles per hour. Forty cows would require
two such ventilators, 60 cows three, 80 cows four, and 100
cows five. These statements assume that the cows average
1,000 lbs. in weight. If they do average 1,200 lbs. or if
the space in which they are housed is smaller than that
assumed, then the rate at which the air is changed should
be relatively increased.

It should always be born in mind, too, that where ani-
mals are doing a relatively large amount of digestion work,
as in the case when animals are being fattened or when cows
are being fed high for milk production, much larger
amounts of oxygen are required than when simply a main-
tenance ration is being fed.

It has been found, with man, for example, that when
fasting and at rest only 1,627 cubic inches of oxygen was
consumed per hour, but while at rest during digestion,
that 2,300 cubic inches were consumed, or more than 57 per
cent. more oxygen. From analogy we should expect to
find the same relation to exist in the case of our domestic
animals; and from this it follows that with high feeding
should always be associated the best of ventilation. No
engineer thinks of increasing the output of his engine by
simply adding coal; he at the same time opens wider the
draught that more oxygen may also be supplied, knowing
well that if he does not increase the supply of oxygen his
fuel is wasted as smoke. Now, just as in this case, high
feeding with inadequate ventilation must of necessity re-
sult in loss of feed passed from the body unused or ina
diminished desire or capacity to eat on the part of the
animals so treated.

In a preliminary experiment on the influence of ventila-
tion on milk production conducted at the Wisconsin Agri-
cultural Experiment Station, it was found that, with 20
cows the milk production was 3.57 per cent. less where
the ventilating shaft had a cross section of 12 x16 inches
than when the ventilation was ample.

THE NEED OF THE RIGHT TEMPERATURE.

All animals are so constituted that the bodily functions
can go on normally only within certain narrow limits of
temperature and their nervous organization is such that

160-

they can increase or decrease the heat produced in the
body within certain limits; but it must be remembered
that work done in either one of these directions is at the
expense of food eaten and of the amount of useful product
sought.
It has been found with man, for example, that when fast-
ing and at rest and exposed toa temperature of 90° F. he
consumed 1,465 cu. in. of oxygen per honr but ander the same
conditions except that of being exposed to a temperature
of 59° F. the consumption of oxygen was 1,627 cu. in. or
13.3 per ceat. greater, and this increase in the consump-
tion of oxygen was associated with a corresponding in-
crease in the amount of carbon dioxide given off, which
means, of course, an increase in the waste of food eaten.
Now the same must be true of our domestic animals.
If they are sheltered in quarters in which the heat gen-
erated by the necessary vital processes does not suffice to
hold the temperature of the body up to the proper limit
then food eaten and oxygen breathed are both converted
into waste products for the sole purpose of securing the
necessary temperature and this can in no direct way con-
tribute to the production of milk, flesh, wool or eggs. So,
too if the necessary vital processes produce heat faster
than the surrounding temperature will allow it to escape
from the body, the system is forced to make a direct effort
to increase the perspiration for the purpose of carrying
away the surplus heat, and this, too, means a loss of feed

and a reduced capacity of the animals in useful directions.

THE CONSTRUCTION OF STOCK BARNS TO INSURE PROPER
VENTILATION.

Let us now consider the construction of a dairy barn in
which special attention has been paid to the proper ven-
tilation and warmth of the stable for the cows. In this
view, Fig. 1, is shown the exterior of the barn with a
dairy house attached. This barn accommodates 98 cows
and 10 horses, and has been in use for four years. Fig.
2 is a perspective drawing showing the plan of the base-
ment where the cows are arranged in two circular rows
facing one another about a central silo having a capacity
of over 300 tons. In this barn, as shown by the diagram,
every space between the studs of the silo wall constitutes

eS wr

“2

161

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ee
AEM UCL

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2 Ti

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162%

a ventilating flue 34 feet long, and the air is drawn into
these flues at the level of the stable floor instead of at the
ceiling. The latter is the usual method of ventilating a
stable where any effort is made in this direction at all.
By this faulty method not only the warmest but the purest
air is removed while the coldest and most impure air is
allowed to stagnate where the animals must breathe it not
only while feeding with their heads near the floor, but also
while lying down. By the better method, however, Fig. 2,
the air which has been warmed by the bodies of the ani-
mals and is relatively pure rises to. the ceiling where it
remains until it cools and falls to the floor to be drawn
off with the foul air which is breathed directly downward
by the animals and where it tends itself to settle because

it is heavier than pure air of considerably higher tempera-.

ture.

The combined capacity of these ventilating flues aggre-
gates more than 25 sq. ft. (Fig. 3), and they are secured,
it should be noted, without using either additional space
in the barn or one foot of extra lumber. The flow of air
through them, too, has been found by direct measurement
to exceed 3.5 miles per hour when there was only a mod-

erate wind and winter temperature outside: This strong .

ventilation is due not simply to the long flues, but also to
the fact that they are at the center of the building where
the air in them is not chilled by the outside low tempera-
ture. An effort has been made in the construction of
some barns to carry the air up along the outer wall and
between the rafters at the roof, but such flues must always
be less effective in the winter season because the air is so
much chilled by the cold outer wall.

A method of ventilating sheep barns which has been
found fairly effective, is illustrated in this photograph,
Fig. 4, where the white columns are ventilating flues made
_ of wood extending from near the floor up through the roof
near one side of the stable. Had these been extended up
through the ridge of the roof they would have been much
more effective, not only because of their greater length but
also because of the greater suction developed by the wind
in blowing across their tops.

VENTILATION OF A WARM BARN.

Where an effort is made to construct a warm shelter for
animals, provision should always be made for the entrance

TN:

eererereen

if

pais

{ itd i'd

= SNS

\

WSs

AY

\\

\\\

Fig. 4.

nt 2. ee re
Wg eal eae
we = 5 A

164

of fresh air from without as well as for the exit of the
foul air within, because unless there is ample provision for
air to enter from without there can be ouly inadequate
ventilation within, for air can leave a compartment no
faster than it enters it.

In this round barn, Fig. 2, entrance for air is provided
through a series of auger holes through the siding just
above the sill. The inside sheeting not shown in the
plan, on one side of the studding, and the siding on the
other constitute cold air flues through which the fresh air
rises and enters the stable at the ceiling as indicated by
these arrows. By this arrangement the cold air is min-

- gled with the warmest air of the stable and has the chill.

taken from it before it comes in contact with the cows be-
low. Of course it would not do to have the auger holes
through the siding at the level of the ceiling, for in this
case the warm air would always leave the stable on the lee-
ward side and cold air would blow in on the windward
side.

In my judgment the bad effects which have been attrib-
uted to basement barns for sheep on account cf “damp-
ness” are in reality usually due to imperfect ventilation.
Any well drained basement or cellar may be as dry as any
other compartment of the same structure if it is only
properly ventilated. Since the basements of barns have
usually tight outside walls and since there is rarely any
provision in them for the entrance of fresh air from with-
out, they are often very poorly ventilated and rendered
damp by the moisture thrown into the room from the lungs
and bodies of the animals housed. Now sheep suffer less
in a dry, cold, pure air than they do in one which is foul,
but the normal temperature of a sheep is high and
they have a thick coat of wool for the express purpose of
economically maintaining it, and a fairly warm stable with
ample pure air it would seem is what is needed for eco-
nomical maintenance. ;

ECONOMY IN FIRST COST.

Let us look now to the construction of buildings with a
view to economy of first cost. Here is the floor plan, Fig.
5, of what has been regarded as one of the best planned
horse barns in Ontario. It is convenient and commodious

eo, >,

165

iu its appointments but expensive on account of the rela-
tive dimensions adopted in its construction. it is 150 ft.
10 in. long and 30 ft. wide with 18 ft. posts. Now almost
identical appointments inside may be provided in a build-
ing only 75 ft. 10 in. long and 44 feet wide by placing the
stalls in two rows on each side of a common passageway
11.5 ft. wide, and in this arrangement only 18,709 sq. ft
of floor and outside surface would be required as against
21,759 sq. ft. in the structure in use, or 14 per cent. less.

ise COURT

ae 2
PASSAGE
GUTTER

”
Sia
oe 5/2 XI | | |

| | STALLS |
6 X 10}

FEED PAS SAGE

150 fF D. HARNESS CASE
S. SHOOTS
H. HYDRANTS
D D passage D OD
HARNESS _GUTTER___ GUTTER
STALL$ STALUS
= 5/2 X 10 5k Xil0 6X10
a a GS eS ee EE (SS Pe
1 = FEED PASSAGE as
a BOX STALLS ——
ux10 |12x10 [8x10 12x10} 6KIO
HARNESS GUTTER
i PASSAGE :
= = = = — = = =
Pig, 98:

The storage capacity for hay would be greater in the more
compact’ structure and it would be warmer and more
cheaply ventilated. The frame of the more compact struct-
ure would cost a little more but the total cost could not
excee d seven-eighths that of the present form.

Th en, again, where several buildings are made to do the
servi ce of a single larger one there is often a still greater
diffe rence in first cost. This difference you will more fully
reali ze after making a direct comparison.

Here is a group of three buildings, Fig. 6, on a dairy
farm, more than usually compact, which provides shelter
for 37 cows and 15 horses and has besides a granary 14 x
24 ft. There is no silo and the storage capacity for feed
is inadequate for the animals housed. Notwithstanding

166

these facts, the outside surface of these three buildings is -
only 269 sq. ft. less than that of this round barn, Fig. 1,
which shelters 56 more animals, contains a 325 ton silo,

me
ee a
1

Fig. 6,

storage space enough for all feed, a 16 x 40 granary and
a tool space of equal area. As indicated on this chart,
Fig. 7, with almost the same outside exposure the single
structure incloses a floor space exceeding that of the three
separate buildings combined by an area 87 x 87 ft. on a
side.

In another group of buildings, one of which is not shown
by a photograph, Fig. 8, shelter is provided in very much
too cramped quarters, for 114 cows and eight horses, but
with no tool house, and no provision for driving behind
the cattle in cleaning. As indicated on this chart, Fig. 7,
the outside surface of these buildings exceeds that of the
round barn by an area 64 feet on a siae while the total floor
space is less by an area 81.5 feet square.

Here is still another group of farm buildings, Fig. 9,
where the extreme of wastefulness of outside lumber and
paint has occurred. In the five of this group of nine
buildings which are used for the same purposes as those to

, hee

Oy

Tolal Outside Surfaces.
A (3089 LS 9 I t

Excess of floor- space
covered by the

D 16.048 -* Round Barn
B, 20210" Above A Above B
C,,35834° * ee : Y Z

LL

Total | loor-Space Eee Z My
A. 5736 Soft. Le
FA G66 °°.
Gant) 7 So Pg Teme

| 13300

46 fi Radius.
eo Sft Posts

which the round barn is devoted, and whose dimensions

are indicated on this chart, Fig. 9, we have an aggregate
floor space less by a square almost 40 ft. on a side and at
the same time an outside area greater than that of the
round barn by a square 140 feet on a side. That is to
say, these five buildings, without a silo and with a smaller
tool house and granary shelter only 36 more cows and four
more horses, but have an outside surface to keep painted
and exposed to the cold which will more than cover two
round barns each furnishing fair accommodations for 98
cows and 10 horses.

Fig. 8.

It should be evident from this presentation that, usually,
he more farm buildings can be consolidated, and the more
nearly equal the horizontal dimensions are made the less
lumber is required in the construction. The square barn
or the broad rectangular forms require iess lumber than

Fig. 9.
the long narrow ones do for the amount of space inclosed;

and whenever the rectangular type is to be departed from
the perfect circle permits of a cheaper, stronger and >

169

more convenient structure than the m
Such as is shown in this view, Fig. 10.

any sided forms do,

Fig. 10.

SAVING LABOR 1N THE CARE OF ANIMALS.

Looking now
to the arrange-
ments of the
barn with a
view to the
Saving of labor
in the care of
the stock, let
us first study
the one whose
provisions for
ventilation
and warmth
have been not-
ed. In the first
place it will be
seen, Fig. 2,
that there is
stored 325 tons
of silage at the
center of the
group of 98
cows to be fed
where the si-
lage may be
dropped into
the basement

170

through this chute
and distributed to
the cows in the
shortest possible
time. As shown in
Fig, 3 too the dry
fodder is so placed
that it may be
dropped through
chutes directly into
the mangers at half
a dozen different
points. Provision
is also made _ for
taking ground feed
from the granary
through feed bins
opening at the floor
upon which the
cows stand, at a
point here near the
entrance door,

Fig. 12. In cleaning the
barn a double wagon or boat enters the stable here, Fig. 2,
and passes entirely around and out again at the same point;
it may also pass behind the inner row of cattle around the
silo and out again at the same door. Fig. 11 is an inte-
rior view showing a section of the outer row of stanchions
in this barn Fig. 12 is an interior view of the same
barn looking toward a nearly empty hay mow to the left
of the silo and shows how a loaded wagon may drive en-
tirely around the silo and out again.

It is much more difficult to make as convenient a dis-
tribution of the feed in the rectangular type of barn or to
arrange as nicely for the cleaning of the barn. It is, how-
ever, possible to make a close approximation of these con-
veniences as will be seen from this diagram Fig. 13, which
shows how it may be done in barns of two sizes, one pro-
viding for feeding 96 cows, and the other for feeding 56.
In these plans both the silage and the dry fodder may be
dropped directly into the mangers between the two double
rows of cows. The cleaning also may be done with team
and wagon or boat but three driveways and six outside

a P

171

doors are required. The silo in neither of these cases can
be permitted to reach the ground floor and hence must be
shallower and relatively more costly in construction. It
will be seen that the smaller barn differs from the larger
one only by omitting two of the bents.

SttO 16X30
24FT DEEP

HAYMOW
4SX60

0 0

BARN FLOOR
16X60

GRAIN SILO 16436

WAGON DRIVE

w
>
ec
a
z
°
)
<
r-4

BARN FLOOR
‘6X 60

° o

HAYMOW
i5X 60

BASEMENT SECOND FLOOR

Fig. 18.

In Figs. 14 and 15 are shown two views of a three-story
barn owned by Mr. Hiram Olmstead, Walton, N. Y., where
the plan of construction permits driving upon each of the
three floors. This allows both hay and silage to be unloaded
from the upper floor where it falls by gravity into place

Fig. £4.
rather than having to be lifted, thus saving labor and
time. A full description of this elegant barn may be
found in Hoard’s Dairyman for May 2, 1893.

Fig. 15. -

CONSTRUCTION OF THE SILO.

Wherever a silo can be built cylindrical in form as shown
in this photograph, Fig. 16, that form should be adopted as

173

it has been found to preserve the silage much better than
the rectangular types and is stronger and more cheaply
built. The depth, if possivle, never should be less than.

Fig. 16.

24 feet and 30 feet is better than 24. Wherever the silo is to
be built outside of a barn the rectangular type should rarely
be adopted, as in such situations, if the necessary depth is
provided, they are much more costly and never can preserve
the silage as well on account of the springing of the walls
under the great lateral pressure of the silage at first which
inevitably admits air to the silage no matter how tight the
walls may be. In the round silo there can be no spreading
when built of wood, as each board is a hoop and the strain
comes lengthwise of the grain. Except in silos having
diameters greater than thirty feet there is no occasion for
using studding larger than 2 x 4 inches, whereas nothing
smaller than 2x 10’s or 2 x 12’s can be safely used in rect-
angular silos unless placed inside of and partly supported
by the walls of another building.

Round silos may be built of wood, stone, brick or iron,
but at the present prices of materials wood is the cheapest
for the parts above ground.

Where drainage will permit of it the bottom of the silo

174

should extend two to three feet below the level of the floor
upon which the animals to be fed stand, and the stone wall
should be 18 inches thick and extend 12 inches above the
level of the ground outside to protect the woodwork from
decay.

This view, Fig. 17, shows the method of constructing
the walls of a round silo. The upper 8 inches of the
foundation wall should be beveled back to a thickness of
about 8 inches as shown here and should be thoroughly

Ahi

aS
a

a
‘

TOS ON ee ee eee

Pern SS SL, Se A
oe oe. ee ea ee ~

ee

Ss a el

1
yy

ul
AY)
és

~)
SS
V~
at
a

ro D eer
G Ens We fo ”, VW] WF, l=

TG LT:

Showing the construction of all wood round silo. Sills 2 x 4’s cut in sectionson a
radius of the silo circle, bedded in riortar and toe-nailed together. Plates the
same, \spiked to top of studding. Studding 2x4’s one fovt apart. Short lengths
may be used, lanpeu, to get the depth. 16’s and 14’s will give a silo 30 feet deep.
Lining made trom fencing ripped in two. Outside sheeting the same. Siding for
silos under 30 feet, outside diametar, common” siding rabbeted; for silos
more than 28 feet, outside diameter, common drop siding or ship lap may be used.
A, shows ventilators between studding. Auger holes are bored at bottom between
studding, and the boards lack two inches of reaching plate at top, inside Both
sets of openings are covered with wire cloth to keep out vermin. ‘There should be
a line of feeding doors from top to bottom, each 2 or 3 teet by 5 feet, and about 2.5
feet apart.

plastered with two coats of good cement to render it air-
tight, this being put on, however, after the silo is -other-
wise completed in order to make the joint between the sill
and the wall perfectly air-tight. Silage juices tend to

eS
vis
1m 4
” 7
ee
vss =
t

175

soften the best of cements and render them porous; to pre-
vent this it is a good plan to apply a good coat of white-
wash each year, this being found in practice to about neu-
tralize all of the acid which comes to the wall, and thus
protects it.

To prevent rats from burrowing under the wall and ad-
mitting air to the silage, it has oeen found desirable to
cover the bottom of the silo with a thick coat of grout as
shown here.

The walls of the silo above the stone work may usually
be built of 2 x 4 studding set one foot apart and- covered
inside with two or three thicknesses of half-inch boards
made from good fencing, sized to a uniform width, and
then split in two, the layers having a good quality of tar
paper between, as shown at this point (Fig. 17). Outside
there should be, in cold climates, another layer of the same
half-inch lumber and this covered with paper and finally
with ordinary beveled siding having the thick edge rab-
beted as shown in the figure here.

To prevent the lining and studding from rotting ample

ventilation must be provided and this may be done by bor-
ing holes through the siding just above the sills between
each pair of studs and covering them with wire netting to
keep out vermin as indicated, Fig. 17. At the top the
lining should not quite reach the plate, thus providing a
place for the air which enters below to escape, to keep the
lining dry. The openings of the silo should also be
guarded by netting to prevent silage from falling in be-
hind during filling.
’ The sills and plates are made by sawing 2 x 4’s in two
foot lengths on a bevel so that they will lie together in a
circle. The pieces which form the sill are toe-nailed to-
gether and bedded in mortar on the wall, while the pieces
for the plate are spiked down upon the tops of the stud-
ding. Only one thickness is required in either case.

The roof can best be built in conical form and covered
either with shingles or a good quality of roofing felt. If cov-
ered with the latter, the felt will be cut into lengths de-
termined by the slant height of the roof and these pieces
will then be cut in two diagonally lengthwise, running the
strips up and down on the roof lapping about four inches.

The roof boards may be put on in the manner shown in
Fig. 18, which shows the underside of the roof of a silo 16

176

feet in diameter. This is a circle five feet in diameter
made of two thicknesses of two inch stuff spiked together.
The roof boards are
pieces of fencing
sawed to the length
of the slant height
of the roof and then
ripped in two di-
agonally at the
mill. After fixing
the circle in place
the roof boards are
nailed directly to
it and to the plate
when the whole be-—
comes self-support- —
ing,

For larger silos
two or more circles
may be used and
the roof made with-
out rafters in the —
same way.

Every silo roof
should be provided

igo: with .a ventilator
This may be an ordinary cupola or it may be made of gal-
vanized iron, as shown in Fig. 16, and provided with a
damper to be closed during cold weather to protect the
silage from freezing. The ventilator is necessary in order
to insure a rapid drying of the walls and inside of the
lining as fast as the silage is removed so as to avoid de-
cay. ;

The feeding doors should form a series one above the
other placed about three feet apart as shown in Fig. 16.
They should be about two feet wide and three and one-half
to four feet high. The doors may be made and hung as
shown in Fig. 19. Here there are three thicknesses of
matched flooring with two layers of tar paper between
nailed to the two cleats. Each door swings on a pair of
six-inch T hinges, and is fastened shut by two strips of
band iron bolted to the cleats and shutting down over two
half inch bolts reaching through the wall of the silo at —

177

these points and provided with handle burrs like those upon
the rods to the end boards of wagons.

For silos less than 20 feet in diameter these cleats should
be cut to the curvature of the silo and the door made of

}
{

Fig. 19.

four-inch flooring with paper between, as in the case just
described. This avoids the shoulder formed by the flat
door.

When the doors are closed for filling, the leakage of air
about the doors may be prevented by tacking over the
joints, on the inside, strips of tar paper about six inches
wide, letting the silage come directly against these strips,
which are of course replaced each year,

Table for Determining the Relative

. . . . ] e a . . fe a . . s S
2 /2ighl oS 72 oe 2 |2 oP) £ = os = = 23 :
— = oe 3S = bo 3 =) es =] 2 |-as 2 2 oo)
5 = TS | 2 2 \538 2 BS) os > = B-5 Se 3 ¢
r/R iSe eb |S ies] e |B ise 2 | 2s £-\ 2 iss
A.|Flesll & 1 lesll & le ieel| & F laa|| A Bima
PAN, aerasil Rae, bee was :
32 | 37 | 33 | 14 38 | 22 a 30 = -
33 | 44 | 84 | 20 39 | 28 rae ble. “
35 | 66 4 | as oy 30 46 | 44 51 | 49- .
35 59 2 i. wy - 54 7
40 36) 68 37 | 38 42 | 45 = 50 e eS |
By ol cba 38 | 45 43 | 50 ie OS pronto
38 | 84 46 | 39 | 51 51 | 44 | 56 56 =| ae
39 | 92 40 | 58 45 | 62 pe eee
ay eae Pay ae Ae ae 52 | 7 57 | 78
32 | 31 42 | 72 || 47 | 7 =| a ae
33 { 38 43 | 79° |" 48 | 81 a ae a ae
34 | 46 44 | 85 || 49 | 87 oa ps ae
35 | 53 45 | 93 || 50 | 93 5 | 94 60 | 94
HR get gia a ae
Zagle _ 35 eri Nl = ; 5
39 | 84 36 | 23 || 41 | 35 46 | 40 Bt) 4
40 | 92 37 | 34 || 42 | 40 aes eo
~\"39- RET) a a 49 | 55 54 | 59
32 | 26 39 |
33 | 33 || 40 | 52 || 52 | 45] 57 || 59 5 61 62 55 os
34| 40 || 471 41 | 59 46 | 63 Bl | 66 56 | 69
35 | 47 || | 42 | 66 || - 47 | 69 pa sae
36 54 | 43 |}. 72 48 (43) Bd 3 59 84
42 | 37 61 | 44 | 79 49 | 81 Ae a ae
38 69 45 | 86 50 | 87 oe aes
39 | 77 46 | 93 51 | 94 Pa,
40 84 a ST) fp | eee | f Se | [tee fh ei aaa a 38
gis eae a 36:| 23 || rahe 46 | 37 ot | 42
ek eee 37 | 29 42 | 36 a 4 52 | 46
33 | 28 | 38 | 35 43 | 41 $0) 38 Bs a
51 a1 | | cs r 5 52 | 50 | 56 3 55 | 60 ‘
35 | 41 | | j 52 ||
gg | |) $8] 2] 8] 58) BS ol et) 68) ol
qr 55 | ¢ ” 2 6 6
43 38 | 62 43 | 66 | 48 | 69 4 re ee
39 | 70 44 | 7% 49.| % Sale Se
tie a ee a 56 | 89 61 | 89
1| 85 6
| ie | 47 | 93 | 52 | 94 b7 | 94 |] ce 5
—— | — = a a ar —S | | : 8
32 ot | | 36 | 19 41 | 27 a ae Bh nS
33 | 23 | 37 | 21 42 | 32 A 88 Sebo
34 | 29 38 | 30 43 | 37 ao | 2 She |
35 | 36 39 | 36 44 | 42 49 | 47 Sap .
.| 86 | 43 40 | 42 || 45 | 48 sO ee oie
371 49 | 41 | 48 46 | 53 | Bh Be ed | ie ;
44 \ 38/156 || 49 | 421 5f || 64 | 47 | 59 || 69 52 | 8 Bi | 5 ,
39 | 63 | 43 | 60 48 | 64 oan a
40 | 7% 44 | 67 49 | 7 aie ae |
41 | 78 | 45 | 7% 50 | 76 ae ee .
42 | 85 | 46 | 80 B1 | 82 ae ae |
43 | 92 47 | 86 52 | 88 ae ae
—| ——| —— 48 | 93 53| 94 58 4 ae |
38 | 18 ” | 24 42 | 28 ti S Sis
34 | 24 | 38 | 26 43 | 33 48 | 30 SRS: :
35 | 31 | 39 | 32 ||. 44 | 38 hs cae om
36.| 37 40 | 37 45 | 43 Bo: $8 ore
S| 60 cai ag ae ies 52 | 58 57 | OL
38 | 50 5
45 39 | 57 50 | 43 | 55 55 | 48 | 59 60 2 2 65 5
40 | 64 44 | 61 49 | 65 BA) 68 us
41 | 71 45 | 67 50 | 70 op (ae Pee
42 | 78 46 | 74 51 | 76 ee ae
44 | oe ie By a oa 58 | 89 63 | 90
hy te 49 | 98 54 | 94 59 | 94 64 | 95

is i i Find air tempera
:_ Notice the table is in three-column sections. dail
ical ate el opposite this is relative humidity. Example: Air peer
site 53° is 63, which is the per cent. of saturation.

Humidity in the Air of Curing Rooms,

So ae Be po | a bs hs ici aS fie Si Oe er
= =| ont ~ = — b= = Soe aa ss a | | —
2 flies] & | 2\5s|| B | 4 les|| |B les]| B | 4188

8 |28 ® |Se oe 21S | ayia es

Poa ee s|| 2 S5i\| BP | &igs|| PB | Plossl] P |e lag

A Ble A |Elma|| A |F imal A |F la@all 6 | Elma
53 | 40 58 | 45 63 | 48 68 | 51 73 | 54

54 | 45 59 | 4 64 | 52 69 | 54 || 74 | 57

55 | 49 60 | 52 65 | 55 70 | 58 | | 75 | 60

56 | 53 61 | 56 66 | 59 Me) Or 1 | 76 | 63

57 | 57 62 | 60 7 | 63 72 | 65 || | 77 | 67

Be S: 61 5 64 68 | 665 73 | 68 || 731 7
66 4) 68 9 | 70 74 | 72 79 | 73

60 | 71 a 65 | 72 ae 70 | 74 | oh 75 | 76 86 80 | 77

61 | 75 66 | 77 ab te 76 | 80 || 81 81

62 | 80 7 | 81 || 72 | 82 | 64s) 2 | 84

63 | 85 68 | 85 73 | 87 78 | 88 || 83 | 88

64 | 90 69 | 91 74 | 91 79 | 92 || 84 | 92

65 | 95 (0 | 95 75 | 95 80 | 96 | 85 | 96
oe | | | | ee ee ee |) fee SS | ——
54 | 41 59 | 45 64 | 49 69 | 52 74 | 54

55 | 45 60 | 49 65 | 52 70 | 55 w5 | 57

56 | 49 61 | 53 66 | 56 71 | 58 76 «60
57 | 53 62 | 57 67 | 59 72 | 62 77 | 64

| 58 | 58 63 | 61 68 | 63 "3 | 65 78 | 67
59 | 62 64 | 65 69 | 67 74 | 69 | 79 | 7

67 | 60 | 66 72 | 65 | 69 dir a re yea OI ME 87 | 80 | 74
61 | 71 66 | 7 (6 i a 76 | 76 || | 81 | 77

62 | 76 67.| 77 72 | 78 V7 | 80 || | 82) 81

63 | 80 68 | 82 73 | 83 78°| 84 83 | 84

64 | 85 69 | 86 7 7 | 79 | 88 | | 84 | 88

65 | 90 70 | 91 7 | 91 80 | 92 || 85 | 92

66 | 95 71 | 95 76 | 95 81, | 96 | 86 96

55 | 42 60 | 46 65 | 49 70 | 52 75 | 55

56 | 46 61 | 50 66 | 53 71 | 55 76 | 58

57 | 50 62 | 53 37 | «56 72 | 59 o7 | 61

58 | 54 63 | 57 68 60 72 | 62 | 78 | 64

59 | 58 64 | 61 69 | 63 74 | 66 | 79 | 67

60 | 63 65 | 65 70 | 67 75 | 69 80 | 7

68 | 61 | 67 73 | 66 | 69 Pei ele vt 83 | 76) 73 || 88} 81 | 7%
62 | 71 ft |¢ 2s 7 Zim (noe | g2| 7

63 | 76 68 | 7 73 | 79 78 | 80 83 | 81

64 | 81 69 | 82 74 | 83 79 | 84 || | 84] 85

65 | 85 70 | 86 75 | 87 80 | 88 | 85 | 88

66 | 90 71 | 91 76 | 91 81 | 92 92

67 | 95 #2 | 95 v7 | 96 82 | 96 || 7 | 96

56 | 43 61 | 47 66 | 50 71 | 53 | 76 55

BY | 47 62 | 50 |; 67 | 53 72 | 56 || 77 | 58

58 | 51 63 | 54 68 | 57 73 | 59 || 78 61

59 | 55 64 | 58 69 | 60 74 | 63 79 | 64

60 | 59 65 | 62 70 | 64 75 | 66 || 80 | 68

69 | 61 | 63 66 | 66 71 | 68 76 | 69 || 81 | 7
62 | 67 74.| 6 | 7 BO 72 ha? 84177 | 73 || 89] 82) 7

63 | 72 68 | 7% pe S|. Fas 83 | 7

64 | 7 69 | 7 "4 | 7 79 | 80 || {| 81
65 | 81 70 | 82 75 | 83 80 | 84 | | 85 | 85

66 | 86 71 | 86 7 Re 81 | 88 | 86 88

67 | 90 72| 91 v7 | 91 82 | 92 || 7 | 92

68 | 95 73 | 95 78 | 96 || 83 | 96 | 88 | 96

BT | 44 62 | 47 66 47 | 72 | 53 i7 | 56

58 | 48 63 | 51 v | 51 73 | 56 78 | 59

59 | 52 64 | 55 68 | 54 74 | 60 || 79 | 62

. 60 | 55 65 | 58 69 | 57 7 | 63 || 80 65
61 | 60 66 | 62 70 | 61 76 | 66 || 81 68

62 | 64 7 | 66 | 7 A 177 | 70 || | 82 | 71

70 | 63 | 68 75 | 68 | 7 80 | 72 | 68 85 | 78 | 7 90 | 83 | 7
64 | 72 69 | 7 B.1-% 79 | %7 || g4 | 7

. 65 | 77 70 | 7 74 | 75 80 | 80 | 85 | 81
. 66 | 81 71 | 82 75 | 79 81 | 84 || 86 | 85
67 | 86 72 | 87 76 | 83 82 | 88 | 7 | 88

68 | 90 73 | 91 v7 | 87 83 | 92 || 88 | 92

69 | 95 74.1 95 78 | 92 84 96 | 89 | 96

‘ure in first column, then find wet bulb temperature in second column, same divis-
ture is 60° in first column; wet bulb is £3° in second column, same division. Oppo-

INDEX.

Acme harrow, 139,

Adhesion, 7.

Advantage of a warm soil, 123.

te of soil, need ot, 93; methods
of, 95.

Affinity, chemical, 8.

Air, humidity of for curing rooms, 178:
warmed by snow storms, 77; once
breathed unfit for respiration, 158;
respired heavier than pure, 162;
si ewe used by horse, sheep, steer,

Air chamber, function of in pumps, 58.

Animals, locomotion of, 21;
of rain and snow on, 75.

Animal temperatures, regulation of, 74.

Atmosphere,
waves, 67.

Atmospheric pressure, 55; variations in,
56; effect of variations on soil-water,
56; on soil ventilation, 56, 149; action
in suction pumps. 57.

Axle, wheel and, 23; trains of wheels |

and, 23.
Babcock and Beimling milk tests, 12;

Baker, Prof., on effect of drainage on |

crops, 143.
Barns, construction of, 157;
right temperature in, 159; economy in

cost, 164; saving of labor in caring for |

animals, 169.

Beams, safe load for, 45. 4

Beam-wheel, effect on draft of plow, 133.

Belting, 36; activity of, 36.

Bins, pressure of grain in, 52

Bodies, structure of, 5.

Breaking, strength of wood, 42; con-
stants of materials, 43; load, 44, 45.

Building, economy in cost, 164.

Burning green or wet wood, 77.

Capacity of soil to store water, 105; ef-
fect of manure on, 118.

Capillary action, 47.

Capillary movement of water in soil,
rate of, 110.

Cement in silos, 174.

esha degrees reduced to Fahren-

eit. 70.

Centrifugal force, 12; to compute, 13;
creaming, 13.

Centrifuges, speed of, 24.

Chamberlin and Salisbury, size of soil |

ly 93; composition of subsoils,

Cheese curing rooms, humidity in, 178.
Chemical, changes, 3; waves, 65; affin-

ity, 8.
Chimneys, draught in, 67.

bad effects |

transparency to ether |

need for |

Churn, friction in, 37.

Cohesion, 7.

Cohesive strength of timber, 39; of other
materials, 39.

| Composition of subsoils, 91.

Conduction of heat, 66.

Conductors and non-conductors of elec-
tricity, 81.

| Constants, breaking, 42,43.
Conservation of soil- water, 120,121.

| Construction of a silo, 172; of farm build-
ings, 157.

Control, of water content of soils, 119;
ot moisture by firming the ground, 122;

| of soil temperature, 124.

| Convection of soil, 87.

Cooling milk, 75.

| Coulters, effect on draft of plows, 134.

Creaming, gravity method, 12; centrifu-
gal, 13; force, 14.

Crooks, motion of molecules, 6.

Cultivation, influence on evaporation,
123; flat, 122; deep and shallow, effect
on soil temperature, 126.

Cultivators, objects of, 140.

Surin rooms, table of humidity for,
17

[om

Deep and shallow cultivation, effect on
soil temperature, 126; effect on soil
moisture, 122, 126.

Deep tillage to increase evaporation, 122.

Depth, of root feeding, 104; of silo, 173;
ot drains, 152.

Diffusion, 5, 48.

ie daa more oxygen needed during,
159.

Dirt in journals, bad effect of, 36.

Dise harrow, 138.

Ditches, open for drainage of land, 142.

Doors of silo, 176, 177.

Draft, of plow, 132; effect of beam wheel
on, 133; of sulky plows, 134; effect of
coulters on, 134: on common roads, 25;
on uneven roads, 27; of horse, 25; on
up-grades, 26; with wide and narrow
tires, 28.

Drains, best depth for, 152; best distance
between, 152; grade of, 154; outlet of,
155; junction tile in, 155; obstructions
to, 155; mains an@ laterals, 155.

| Drainage, farm, 142: in Illinois, 142; ne-
cessity for, 143; influence on soil tem-
perature, 145; on soil ventilation, 95,
148; increases available water, 149; lands
likely to be benefited by, 150; road, 30.

Draught in chimneys, 67.

Earth-worms, in soil formation, 86; in soil
aeration, 95; in soil convection, 87.

18

Economy, iu cost of farm buildings, 164;
in labor of caring for animals, 16).

Electrical induction, 80.

Electricity, nature of, 79; atmospheric,
80; positive and negative, 81; discharges
from a point, 81; conductors and non-
conductors of, 81.

Elliott, C. G., tile drains, 156.

Energy, 10; and matter indestructible,
10; temperature a measure of, 68; lost,
sliding friction in machinery, 36; stor-
ing of, 15.

Energy, solar, how reaches the earth,
63; mechanical value of, 64, 65.

Ether waves, kinds of, 64; work done by,
65; transparency to, 67.

Evaporation, cooling effects of, 73; heat
units required for, 73; loss of water by
surface, 112; influence of cultivation
on, 120,.12i1; of topography on, 113; of
woodlands on, 115; deep tillage to in-
crease, 122; surface tillage to check,
120.

Evener, two horses, 18; giving one horse |

the advantage, 19. .

Fahrenheit degrees reduced to centi-
grade, 70.

Farm drainage, 142.

Fences, wire, danger of lightning from,
3"

Ferment, germs producing natural ni-
trates, 94.

Firming soil to control moisture, 122.

Floating gardens of the Chinese, 94.

Flotation, principle of, 53.

Flow, of water, 60; velocity of discharge
from pipes, 61; of air through venti-
lators, 162.

Fluids, 46; pressure of, 50; sp. gr. of, 55.

Foot-pounds, 9.

Force, kinds of, 6; matter and, 3; cen- |

trifugal. 12; to compute centrifugal,
13; strength of creaming, 14.

Forces, molecular, 7.

Friction, between solids, 34; influence of
pressure on, 35; between solids and
liquids, 35; of rest or static, 34; of mo-
tion or kinetic, 35; sliding, 36; in the
ehurn, 37.

Gaseous state, 9.

Germination, best temperature for, 124,
144; oxygen essential to, 93, 147.

Glacial subsoils, 91.

Grade of drains, 154.

Grain in bins, pressure of, 52.

Gravitation, 7.

Gravity, method of creaming, 12;

Si CMasy

(Green and wet wood, burning, 77.

Ground-water, contour map of surface,

spe-

99: and wells, 100; effect of pumping |

on, 100: fluctuations in level of, 103;
best height of, 104; surface of after
rain, 153, 154.

Grout, to keep rats out of siio, 175.

Haberlandt, best temperature for ger-
mination, 124, 144.

Harrow, uses of, 138; Acme, 139; Disc,
138; tooth, 140.

Head of water, 61.

Heat, nature of, 63;waves 65; transfer of,
66; unit, 70; units required to melt ice,

\

2

nd

73, 75; evaporate water, 73, 75; latent,
72; specific, 70; of soils, 71.

Hellriegel, amount of water used by
plants in Prussia, 96; best proportion of
soil saturation, 108.

Horse power, 9.

Horse. giving one the advantage, 19;
traction power of, 25.

Hot-beds, principle of construction, 68.

pee of air in curing rooms, table
O18).

Hydrogen molecules, distance traveled
without collision, 6.

Ice, heat units required to melt, 73, 75;
cooling milk with, 75; action in soil
formation. 85.

Illinois, drainage in, 142; yield of grain
increased by drainage, 142.

Inclined plane, 24.

Inertia, 11.

Irrigation, natural sub-, 151.

Journals, dirt in. 36.

Junction tile, 155.

Kinetic friction, 35.

ees water capacity of different soils,

oO.

Lactometer, 48, 55.

Landside of plow, function of, 131.

Lanes likely to be benefited by drainage,

50.

Latent heat, 72.

ee of ground water, fluctuations in,

Lever, 16.

Lightning, protection against, 80, 82;
when an object may be struck by, 81;
danger of from wire fences, 83; rods,
functions of, 82; essential features, 82.

Light waves, 65.

Liquids, ideal, 8; surface tension of, 46;
specifie gravity of, 55; osmose of, 49;
solution of solids in, 48; pressure of in
vessels, 51; and solids, friction be-
tween, 35.

Load, breaking, 44, 45; safe for horizon-
tal beams, 45; for posts, 39.

Locomotion of animals, 21.

ers of water by surface evaporation,

Lumpy soil, bad effects of, 119; effect on
temperature, 125.

Macadam system
tion, 29.

Machines, elements of, 16; not genera-
tors of energy, 11.

Manure, depth of plowing in, 117; effect
on water capacity of soils, 118.

Map, contour, of ground water surface,
99; of area occupied by wells, 98,

Materials, strength of, 38, 39, 42, 43.

Matter, kinds of, 3; constitution of, 4;
inertia of, 11: indestructible, 10; and
foree, 3.

Mechanical powers, 16.

Melting of ice and snow; 73, 75.

Milk, test, 12; cooling with ice and cold
water, 75; production, effect of -venti-
lation on, 159. e ri

Molecular forces, 7.

Molecules, 4; size of, 4; properties of, 5;
of bodies not at rest, 5; of hydrogen,
distance traveled without ¢oliision, 6.

of road construe-

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183

Momentum, 15.

Morin, Gen., experiments concerning
traction on roads, 31.

Morton, on draft of plows, 133.

Mulches, effect of thin soil, 121.

Muscle, force of triceps and biceps, 21.

Natural sub-irrigation, 151.

Nitrates, natural, 94.

Nitric ferment, 94; best temperature for,
124, 144; need of oxygen for, 94, 148.

Obstructions to drains, 155.

Oil, use of in machines, 35.

Organic matter, plowing in, 117.

Osmosis, 49.

Outlet of drains, 155.

Oxygen, essential to nitrification, 94,
148; essential to germination, 93, 147;
amount required by animals, 158; by
man, 159; during digestion, 159;
amount varies with temperature, 160;
uses in soil, 93, 147.

Percolation of impure water into wells,
101; rate of in field soil 109; influence
of topography on, 112; from long col-

_ umns of sand, 106.

Pillars, strength of pine, 38.

Pipes, flow of water in, 61.

Piston, size of, 57.

Plane, inclined, 24.

Plants, amount of water consumed by.
96, 97; proportion of soil-water avail-
able to, 106.

Plow, work done by, 127; mechanical
prinviples of, 130; advantage of oblique
eutting edges, 130; function of land-

side, 131; proper line of Graft of, 131; |

draft of in different soils, 132; effect of

beam-wheel on draft, 133; effect of

coulter ou draft of, 134; sulky, draft

of, 134; scouring of, 135; pulverizing

oe of, 135; care of, 186; subsoil,
(.

Plowing, early, saving of soil moisture
_ by, 113, 120; in of organic matter, 117;
depth of plowing in of manure, 117.

Pounds, foot-, 9.

Power, exertion of great, 24; horse-, 9;
traction, of a horse, 25; sweep, 24;
tread, 25. :

Powers, mechanical, 16.

Pressure, atmospheric, 55; of fluids, 50;
of liquids in vessels, 51; of grain in
bins, 52 >

Puddled soils, 123.

Pulley, 31; horse-fork and, 33; used to
raise stones, 33.

Pump, suction, 57.

Pumping, rate of, 58; from wells, effect
on ground-water surface, 100.

Pusey, on draft of plows, 132.

Radiation, 64.

Rafters, breaking load of, 45.

Rain and snow on domestic animals. ef-
fects of, 75; inches per ton of dry mat-
ter of crops, 97.

Rats in silos, to prevent, 175.

Roads, construction, Macadam system,
29; Telford system, 29; drainage of,
30; draft on, 25; good, make high
grades more objectionable, 27; Gen.
Morin’s experiments on draft on, 31;
soft and uneven, 27.

Rod, lightning, functions end features

of, 82.

Roller, effects of, 122, 141.

Roof of silo, 175; ventilator for, 176.

Root, breathing, 94; feeding, vertical ex-
tent of, 104; room, -how drainage in-
creases, 149.

Roots 0 trees obstruct drains, 155.

Sachs, plants wilting with low tempera-
ture, 144. :

Sandborn, Prof. J. W., draft of plows,
153; coulters, 134.

Seales, platform, 20.

Serew, 34.

Seed bed, rolling, 123.

Seeds, germination of, best temperature
Se 124, 144; oxygen essential for, 93,
> |

Sheep, ventilation of barns for, 162, 164.

Silage, lateral pressure of, 173; juices
soften cement, 175.

Sills and plates of silo, 175.

Silo, cement in, 174; doors. 176; best

depth, 173; round, 173, 174; construe-
tion of, 172; roof of, 175; sills and
plates, 175; size of studding needed in,
173; springing of walls of rectaug-
ular, 173; stone wallin, 174.

Siphon, 60.

Sliding friction in machinery, 36.

Snow, heat required to melt,
storms warm the air, 77.

Soil, capacity to store water, 105; effect
of manure on capacity to store water,
118; advantages of warm, 123, 144;
moisture, functions of, 96; drainage,
need for, 143; needs of aeration, 93;
methods of aeration, 95; breathing, 56;
149; convection, 87; cooling of by
evaporation, 73, 146; nature and origin,
84; particles, size of, 92; removal, 88;
surface, 88; kinds of, 89; kinds which
yield their moisture to plants most
completely, 108; puddled, 123; capillary
movement of water in, 110; control of
water content, 119.

Soils, specific heat of, 71.

Soil temperature, best, 124; control of,
124; effect of deep and shallow cultiva-
tion on, 126; effect of rolling on, 124,

' 125; effect of drainage on, 125, 145.

Soil-water, conservation of, 120, 121; ef-
fect of atmospheric pressure on, 56;
influence of cultivation on evaporation
of, 121; movements of, 109; proportion
of available to plants, 106; transloca-
tion of, 111.

Solar energy, 63; mechanical value of,
64, 65; work done by, 65.

Solids, friction between, 34; influence of
press1re on friction between, 35; solu-
tion in liquids, 48.

Solution, 48.

ee gravity, 53; to find, 53, 55; table
of, 54.

Specific heat,.70; of soils, 71.

Speed of centrifuges, 24.

Steam, latent heat of, 73.

Strength, of creaming force, 14; of ma-
terials, 38, 42,43; of pillars, 38; tensile,
of timbers, 39; tensile of other materi-
als, 39; transverse, of timbers, 41; trans-

Dy; 60s

184

verse, principles of. 39; of surface ten- | Topography, influence upon evapora-

sion, 46. tion, 113; influence upon percolation,
Stress, kinds of, 38. 112.
Studding, size needed in silos, 173. Traction, on common roads, 25; power

Sub-soil, 90; variation in composition of, of a horse, 25; increased speed dimini-

ile shes power, 26; power diminished by —

Sub-soil plow, 137; use of, 137. up-grades, 26; Gen. Morin’s experi-
Sub-irrigation, natural, 151. ments in France, 31
Substances, states of, 8. Tceanslocation of soil water, 111.
Suction pump, 57. Tread power, 25.
Sulky plow, draft of, 134. | Tree roots obstruct drains, 155.
Surface tension, 46; strength of, 46; in- | Unit of heat,70.

fluence on lactometer readings, 48. Velocity of flow, of water in pipes, 61,
Sweep horse-power, 24. 62; of air in ventilator, 162.

Ventilating flues, capacity of, 162, 159;
Table, traction on roads, %5; breaking for sheep barns, 162; for silo, 176.
load of rectangular pillars, 39; tensile | Ventilation, of barns, 160; correct
strength, 39; breaking constants, 43; method, 162; faulty method, 162; of
safe loads for beams, 45; water press- round barn, 162; need for, 157; effect
ure, 51; specific gravities, 54; specific on milk production, 159; of silo, needed,
heat of soils, 71; water per lb. of dry 176.
matter, 95, 97; capacity of soil to | Ventilation of soil, needed, 93; influence

store water, 106; draft of plows, 133; oc drainage on, 95, 148.

soil temperatures, 145; relative humid- | Viscosity, 49.

ities, 178. Wagon tires, wide and narrow, 28.
Telephone, 79. Water, head of, 61; flow of in pipes, 60,
Telford system of road construction, 29. | 61; consumed by plants, amount of,
Temperature, amount of oxygen used 96,97; impure percolating into wells, 101;

varies with, 160; best for germination, | capacity of soil to store, 105; rate of per-

124, 144; best for nitric ferment, 124, | colation of, 109; loss of by surface

144; control of, 124; etfect of rolling up- evaporation, 112; control of in soil, 119.

on in soil, 124; effect of deep and shal- | Water, capacity ot soils, 105; effect of
low cultivation upon, 126; influence of | manure on, 118.

drainage on in soil, 125, 145; need for | Water-table, position and attitude of, 97;
right, in barns, 159; measurement of, fluctuation in level of, 103; best height

68; regulation of in animals, 74; of, 104
Thermometer, testing a, 69; kinds of | Waves, ether, kinds of, 64.

scales, 70; wet bulb, 74; Weeds, importance of destruction of,
Tile, best depth, 152; best distance, 152; 116

grade of, 154; mains and laterals, 155; | Wells, and ground-water, 100; lowering
outlet of, 155; obstructions to, 155; ot water in, 101; percolatoin of impure
junction, 155. water into, 101.

Tillage, objects of, 116; implements of, | Wheel and axle, 23; trains of, 23.
127; deep to increase evaporation, 122; | Wind, effect on evaporation, 115.

surface to check evaporation, 120. Wire fences, danger of lightning from,
Tilth, importance of good, 118. 83.
Timbers, strength of, 39, 41. Woodlands, effect on evaporation, 115.
Tires, wide and narrow, 28. Work, 9; done by either waves, 65.

Le ee ae es ee a ee ee

RAR

ii