312 
AMERICAN AGRICULTURIST. 
[August, 
hinted, varies greatly in different kinds of matter, and 
many of the properties of matter are due to strength 
with which the atoms are held together. If this force of 
Cohesion is so strong that the atoms are prevented from 
moving upon one another, 
THE BODY IS A SOLID ; 
but when the cohesion is much less, and while the atoms 
are still held together, the force is so weak that they 
freely move about upon one another, and the body has 
no form of its own, but takes that of surrounding bodies, 
WE HAVE A LIQUID. 
There are two forces; one tending to hold the particles 
together, aD attractive force, cohesion , and besides this 
another, which tends to separate or drive them apart, a 
repulsive force, or 
heat. In ice, we 
have a solid body, 
in which the atoms 
are held firmly to¬ 
gether ; by means 
of a slight amount 
of heat, the cohe¬ 
sion between the 
particles is weak¬ 
ened, and it be¬ 
comes water, or 
liquid, and with 
still more heat, the 
attraction of the 
Fig. 2. WATER AND STEAM. atoms is quiteover- 
come, and we have steam, an air-like or gaseous form, in 
which the atoms repel or fly off from one another. The 
difference in the space occupied by water in these two 
states, is seen in the diagram, figure 2. A cubic inch of 
water, when turned to steam, will occupy 1,700 times the 
space. But some of the peculiar and important effects 
of heat will be given in future talks. All that we wish 
to show now is, that heat is opposed to cohesion, and 
that nearly all forms of matter may be made to appear 
AS SOLID, LIQUID, OR GAS, 
by the use of that wonderful force known as heat. Co¬ 
hesion is a force that acts at distances so small that we 
can not conceive how minute they are. If we break a 
piece of glass or steel, it makes no 
difference how firmly we may press the 
broken surfaces together, they will not 
cohere. If we take two bullets and cut 
away apiece from each (fig. 3), to leave 
a smooth bright surface, and then 
forcibly bring these surfaces together, 
with a slight twist (fig. 4), they will cohere so firmly that 
yon will find it very difficult to pull them apart. The lead 
being soft, it allows us to bring some of the particles 
near enough together for the cohesive force to act. If 
the cohesion between the particles of a body is readily 
overcome by a blow, and it breaks readily, we say that 
IT IS BRITTLE ; BRITTLENESS 
then is a property of matter due to the strength of co¬ 
hesion; glass, ice. and sugar, are examples of brittle¬ 
ness. If the force of cohesion allows the body to be bent 
in any direction without breaking—of which we have 
good illustrations in lead or India-rubber, we say that 
IT HAS FLEXIBILITY, 
which is another property of matter. If a substance can 
be beaten into another shape without breaking, as can 
be done with iron, gold, or still easier, lead, it is 
SAID TO BE MALLEABLE, 
a long word that comes from Malleus, the Latin for ham¬ 
mer. If by pulling at a substance, as in working candy, 
we can draw it out without breaking, we say that it is 
ductile. Wires are made from iron, copper, or other 
metals, by drawing them through holes in a steel plate; 
these holes are smaller and smaller, so that starting with 
a piece of iron the size and length of 
a lead-pencil, and drawing it each time 
through a smaller hole, the iron will 
appear as a wire as fine as a thread, 
and several hundred feet in length. 
The cohesion between the particles 
being weak enough to allow this 
change of form to take place, and yet 
strong enough To prevent breaking. 
All these properties—Flexibility, Mal¬ 
leability, Ductility, and Tenacity—are 
due to degrees of the force of cohesion, 
and are only found in substances that are comparatively 
soft. Hardness is the opposite of softness, and we find 
that hard substances are brittle. Many bodies, when 
bent or pressed out of their usual shape, recover their 
form when left to themselves. This property 
IS CALLED ELASTICITY, 
and is the opposite of brittleness. A ball of ivory or 
glass when it falls upon a hard surface is thrown out of 
shape by the blow, but it at once recovers its shape, and 
in doing this rebounds ; a piece of steel or of whalebone 
are other examples of elasticity. The ability to change 
Fig. 4. 
Fig. 3. 
the strength of cohesion between the particles of a metal, 
and make it hard or soft, is of the greatest importance. 
We do this, by the aid of heat, in the operations 
OF ANNEALING AND TEMPERING. 
If a piece of steel be heated red-hot, and then suddenly 
plunged into water, it will be very hard and brittle. If 
it be heated in the same manner and allowed to cool 
slowly, it will be soft and flexible, and have the other 
properties that accompany softness. A skillful worker 
in metals will, by a proper management of the heating 
and cooling, bring steel and other metals to tho hardness 
or softness, required for various uses_The terms 
COHESION AND ADHESION ' 
do not mean exactly the same; Cohesion is the force that 
holds together particles of matter of the same kind. 
Adhesion is the force 
that holds particles of 
a different kind to¬ 
gether. We can not 
make two pieces of 
wood or two bits of 
paper cohere; but if 
we put a thin film of 
glue between the pieces 
of wood, that adheres 
to each and holds both 
together. So we use 
mucilage or paste to 
make two pieces of 
paper adhere. Quick¬ 
silver will not adhere 
Fig. 5.—CAPILLARY TUBES. 
to the smooth surface of a plate, but the drops will 
roll about; while drops of water or of oil will ad¬ 
here to the plate or wet it at once. The adhesion be¬ 
tween a liquid and a solid—or between some liquids and 
some solids—is shown by placing a small glass tube in 
water, or other liquid that will adhere to, or wet the glass. 
If the tube, a , figure 5, is one-twelfth of an inch in diame¬ 
ter, and is placed in water, the -liquid will rise in it a 
quarter of an inch; if the lube, b , has a bore only half 
that of a, the water will rise twice as high, or half an 
inch, and so on, the smaller the tube, the higher the liquid 
will rise. This adhesion between the liquid and the 
inner surface of the tube above illustrated is called 
CAPILLARY ATTRACTION. 
The word capillary comes from the Latin capillus , a 
hair, as it is the strongest in very minute or hair-like 
tubes. It is a real force, able to overcome the attraction 
of gravitation, and raise the liquid a considerable dis¬ 
tance above the surface of that in the dish. Because this 
was first noticed in small tubes, it keeps the name 
“ capillary attraction,” but it is exercised by flat surfaces, 
Fig. 6 .— CAPILLARY PLATES. 
and, but for the difficulty of changing names “surface 
attraction” would better describe it. You can try a 
place where it is burned, by the wick, and by capillary 
attraction. The cotton fiores of the wick present a 
great number of surfaces very close together, and the oil 
rises between these, just as it does through fine glass 
tubes, or between the plates of glass. But there are 
still other important applications of Capillary At¬ 
traction, which I must leave until another time. 
Tl»e Doctor’s Correspondence. 
“WHO IS UNCLE HAL?” 
do you ask. He is of course “Uncle Hal,” and we call 
him so, because he is an uncle, and his name is Hal. 
Though he has nephews and nieces, he is not an old fel¬ 
low like myself—in fact, he is rather a young uncle, and 
not so very many years have passed since he was a 
farmer’s boy, that he has forgotten how farmers’ boys 
feel and act. In fact he is’ as you will find out, up to all | 
the ways of a boy’s country life, and while I would not 
have you by any means forget the “ Old Doctor,” I want 
you to take kindly to the “Young Doctor,” for he is a 
doctor as well as an uncle, and I am sure he will prove an 
excellent uncle to our many Boys and Girls. 
I 
THE SIZE OF CITIES. 
“ T. Z. S.” writes from Conn, that she and another have 
a dispute as to the relative size of London (Eng.) and 
Yedo, or Jeddo (Japan), and that they have decided to 
leave the matter to me. I have a poor memory for 
figures, but in this case I can appeal to the authorities. 
The latest edition of Chamber’s Encyclopiedia (1877) says 
that the population of London was at the last census 
(1871) 3,251,804. As to the population of Yedo or Jeddo— 
it being written both ways—we have no census but only 
estimates. Its population has been stated at all the way 
from 1,500,000, to 3,000,000. and some writers think that 
even the lowest of these figures is too high. The proba¬ 
bilities are that London is much the largest, but here are 
the statements from the best source that I have at hand, 
and my young friends must “ decide ” for themselves. 
CITIES ARE NOT SO LARGE 
as a general thing as people suppose. I came across not 
long ago a carefully prepared article on population, in 
which it was stated that there were in the whole world 
only 215 cities with over 100,000 inhabitants; 29 with a 
half a million or more, and only nine containing over a 
million, and of these nine, four are in China. In the 
order of their population they stand : London. Paris, New 
York (including Brooklyn), Vienna, Berlin, Canton, and 
three other Chinese cities. 
A STEAM WHISTLE PUTS OUT A FLAME. 
A correspondent in Ohio writes that he has upon the 
boiler in his factory a steam whistle, and that this, when 
blown, will put out the lamp in a lantern placed 20 or 39 
feet away from it. He writes to “The Doctor” to ask 
the reason why. If “ H. L. L.,” could see the air when the. 
whistle was blowing, he would observe that it was thrown 
into waves, much as the surface of water is disturbed 
when a stone is dropped into it. But while the waves in 
the water move horizontally only, those in the air move 
in every direction. This disturbance of the air may be 
sufficient to put out the lamp, just as a very slight put!' 
across the top of a lamp chimney will extinguish the 
flame. But there may be another cause. The lantern is 
surrounded by glass; that glass if struck will vibrate, and 
give off a sound ; if the note of the whistle has the same 
pitch as that of the glass, the glass will vibrate when the 
whistle is sounded, and its vibration so disturb the air 
within the lantern as to put out the flame. To find out if 
this is the cause, try other lanterns under like conditions. 
VERY PRETTY EXPERIMENT, 
showing at once the force of capillary attraction, and the 
fact that it takes place with flat surfaces, by means of 
two pieces of window glass. Take two pieces of clean 
glass of the same size, and place them as shown in figure 
6. They should quite touch at two edges, as seen at the 
left hand, and be a little apart at the other edges. By 
placing a small bit of stick to keep two edges open, and 
binding the pieces of glass together with a coarse thread 
or small twine, you will be able to keep them in place. 
In order to see the liquid plainly, it should be colored by 
adding a little ink. The glasses being set in a plate or 
other dish containing the colored water, the liquid will 
at once rise, as shown in the engraving, rising the high¬ 
est where the surfaces are the nearest together, and lower 
where they are farther apart, and forming a beautiful 
curve. Capillary attraction is shown whenever a porous 
body is placed in a liquid that will wet it; thus if a lump 
of sugar placed in a spoon has its lower part merely 
touched to your coffee or tea, those liquids will rise at 
once, by capillary attraction, and wet the whole lump. 
We make 
A FREQUENT USE OF THIS FORCE, 
and though a small affair, its application has much to do 
with our daily—or rather nightly—comfort. In our lamps 
the oil is burned at a point, often some inches, above 
the part of the lamp that holds it; it is brought up to the 
Our I*uzzIe-JBox. 
NUMERICAL ENIGMAS. 
J. I am composed of 19 letters : 
My 8, 9, 14, is a young animal. 
My 1, 0, 3, 4. is part of a house. 
My 7, 2, 11, 12. is a distance. 
My 13, 17, 10, is often a disagreeable answer. 
My 10, 5, 17, 15, is much to be dreaded. 
My 18, 12, 1, 19, is a reptile. 
My whole is the name of a celebrated poet. Emma. 
2. 1 am composed of 9 letters: 
My 0, 8, 7, 2, is a girl’s name. 
My 5, 4, 1. 9, is the name of a college. 
Mv 7, 9, 4, is a kind of drink. 
My 6, 9, 1, is a fish. 
My 3, 6,1, 7, is a thick fabric. 
My whole is the name of a well-known General. 
J. C. II. 
PUZZLE WITHIN A PUZZLE. 
Nhew yrn dirht snaphep ot eb vm nodecs eh yam veak 
ym strif papdile ot mih; ym lowlie si a drib. Hautboy, 
diamond puzzle. 
1. Part of a bowl. 2. A color. 3. Convenient. 4. To 
diminish. 5. A city. 6. Fractured and torn. 7. Heathen 
gods. 8. A number. 9. Part of a room. 
The central letters, read across and downward, form a 
city. Nip. 
CHARADE. 
My first is a verb, 
My second not jolly, 
My whole is a poem— 
One censuring folly. Wilks. 
