68 
AMERICAN AGRICULTURIST, 
[February, 
HOTS <k miLS 9 ©miTMHSo 
TSie Boctor’s Talks. 
Last month we were t? ing about Inertia, and it was 
there mentioned that a body set in motion can not stop 
of itself, any more than it can start of itself. That a 
marble set in motion by rolling on the floor would con¬ 
tinue to roll, were it not stopped in part by the resistance 
offered by the air, and in part by that presented by the 
floor. Let us take, for illustration, besides a boy’s mar¬ 
ble. also a square block of marble, of the same weight, 
and the smooth table instead of the floor. You know, 
without trying it, that if you give both the ball and the 
block a push with the same hand, that the marble will 
roll quite across the long table, while the block will move 
but a few inches. If you think why this is, you will at 
onoe see that the block touches a very much larger part 
of the surface of the table than the ball, and that the 
rubbing of the two prevents it from going far. This ob¬ 
stacle to motion by the rubbing together of two surfaces 
IS CALLED FRICTION, 
a word that comes from the Latin word frlcare, to rub. 
You know that the block will slide easier upon the smooth 
table than it will if there is a cloth upon the table, and 
more readily upon ice than upon the smooth table. In 
the case of the round marble, friction helps step that, as 
you know that it will roll farther on the smooth table 
than on the table-cloth, and upon smooth ice much far¬ 
ther than on the table. There are then too kinds of fric¬ 
tion, Sliding Friction and Rolling Friction. Suppose 
you try to push a long wooden box along the bare floor. 
If this box weighs 100 pounds, you will have to push 
against it with a force equal to about 50 pounds before 
you can start it You think that by turning the box 
upon its smaller end, which will presentless surface, you 
can move it easier. Try it. Not a pound easier will it 
move. The amount of friction does not depend upon the 
size of the surface, but upon the pressure. That is one 
of the laws of sliding friction. There are others laws 
concerning friction, but we will not give them now. 
THE IMPORTANCE OF FRICTION 
will be seen when we consider that one-third of the pow¬ 
er of machinery is used in overcoming friction. Hence 
to reduce friction to the least possible, various contriv¬ 
ances are used. There is more friction between two sur¬ 
faces of the same metal than between different metals. 
An iron shaft will run in a bearing of brass with less fric¬ 
tion than in an iron one. If the wheel of our wagon does 
not run readily, we know that there is friction at the 
hub ; we apply grease, and that diminishes the friction, 
the various articles used to reduce friction are called 
LUBRICATORS, 
Fig.l. —FRICTION 
WHEELS. 
a word which, like friction, comes from the Latin, and 
means, to make slippery. 'A number of lubricators are 
used: oil, lard, tallow, soap, black- 
lead, and even water. But in many 
cases, what are called “friction 
wheels” are used, though the better 
name would be anti-friction wheels. 
An axle of a large wheel is made 
to turn upon two wheels placed 
together as seen in figure 1, which 
shows an axle resting upon the rims of two wheels. 
As the axle turns, the wheels turn too, and the friction is 
only at the axles of these small wheels. It is common to 
hang a grindstone in this manner, as no doubt many of 
you have seen. Figure 2 shows the contrivance for a 
grindstone, the stone, however, is not there; whatmight 
be taken for the stone is two iron plates, which are 
made to screw up against the stone, one on each side; 
the friction wheels where the crank is are covered by a 
Fig. 2.— FRICTION WHEELS FOB A GRINDSTONE. 
guard to keep the clothing of the one who turns from 
catching, and also from getting soiled. The least known 
friction between two substances is between polished 
steel and some of the harder precious stones, from 
the cheap amethyst up to precious rubies and diamonds. 
“jewelled watches” 
are Dot watches ornamented with Jewels, but those in 
which the axles of the wheels run in jewelled bearings; 
even very common watches have some of the more im¬ 
portant bearings fitted with cheap jewels. Knowing that 
so much pains is taken to remove, or overcome it, you 
may be tempted to say I wish there were no friction. 
But that would be a hasty wish ; if it could be granted 
there would be a queer state of things. Our wooden 
buildings and interior woodwork would fall apart, as it 
is only held together by the fric¬ 
tion between the wood and the 
nails; you could not walk with¬ 
out slipping up ; the vessels could 
not go to sea, for all their ropes 
would untwist; the locomotives 
could no longer pull their trains 
—indeed, the difficulties we some 
times find on an icy morning 
would be as nothing to it. This 
world is very well arranged as it 
is.... When you strike a ball that 
is at rest with your bat, the mo¬ 
tion of the bat is imparted to the 
ball, aud off that goes. If you 
strike with the bat a ball that is 
thrown towards you, you not on¬ 
ly stop the ball, but, if you hit it 
hard enough you send it ofl’ in an 
other direction. This is one of the 
many instances that illustrate the 
COMMUNICATION OF MOTION. 
If yon place on the table one of 
two ivory balls of equal size, or 
even two marbles, and roll the 
other against it, if the halls strike 
fairly the one that is hit will move 
on, while the one that gives the 
blow will stop, it having given 
up its motion to the other ball. 
The same thing may be shown 
by hanging the balls by strings. A still more striking ex¬ 
periment is to take several elastic balls, as shown in fig¬ 
ure 3. By drawing out the ball, h. to a short distance, 
and letting it drop to strike g, it will give up its motion 
to g, but that can not move, so it imparts its motion to 
/, but that is prevented from moving, and the motion 
goes on through all the balls until the last one in the 
row, k, is reached, and being free to do so, that flies oft' 
as far from the others as h was raised before it was 
let fall. Glass marbles are often used by boys, and these 
answer well for this experiment; as boys can not readily 
attach strings to the marbles, they can show the action 
nearly as well by placing two square straight-edged 
sticks near enough together for their edges to form a 
groove for the marbles to roll along; as the marbles will 
only touch the corners of the sticks there will be but 
little friction. But this experiment, figure 3, not only 
shows that motion is communicated by one moving body 
to another, hut it is one method of showing one of the 
important laws of motion, that 
ACTION AND REACTION ARE EQUAL. 
If you strike the table with the hand, the table reacts, 
returns the blow with a force that makes it unnecessary for 
you to repeat the experiment. If yon fire a bullet from a 
gun, the force of the gases formed by the burning powder' 
pushes the bullet out with great force, but it also pushes 
the gun back with equal force agaiqjt the shoulder, or 
as is commonly said 
THE GUN KICKS. 
By making the gun heavier, the powder has to react 
upon so much more matter, the motion is felt but little.— 
If the gun be held firmly pressed to the shoulder, the re¬ 
coil seldom hurts much; but if it has any distance to 
move back before striking the shoulder, it acquires a 
strong force, and strikes a much greater blow, just as a 
hammer pushed against a nail has little effect, but if 
moved a little through the air it acquires a strong 
momentous force, and drives the nail into the board. 
A Curious Time Trick. 
Here is a rather neat trick, and one quite new to us. 
Let a person tell when he ate his dinner, and another, 
with certain conditions, can know when the same person 
took his breakfast, or arose in the morning, etc. Suppose 
Mr. A. had his breakfast at a certain .hour, as at seven 
o’clock, which he does not tell; but gives the hour that 
he ate his dinner, as at two in the afternoon. Add 12 to 
the hour given—in this case the sum will be 14. The 
person is then requested to count back on the dial of the 
watch or clock (it may be done in the head), beginning 
with the number or hour that he had his breakfast, and 
which he has not told. In this particular case it will bo 
7, and as he counts to 14 he stops at the hour of break¬ 
fasting. Let us try it again. The boy rose at 8 o’clock 
(not very early for a smart boy), and had his dinner as 
late as 3 o’clock. Both of these hours are indicated by 
the hands on the dial. Being ashamed of his rising, we 
will suppose, he only 
tells when he had his 
dinner. Twelve is add¬ 
ed to the 3, and we 
have 15. He begins at 
3, with the rising hour 
in mind (8), and counts 
back on the dial until 
15 is counted, and this 
comes to 8, the hour of 
rising, and his tardiness 
is exposed. The count¬ 
ing back is indicated by 
the figures outside of the dial. If you try it in all pos¬ 
sible ways, the truth will out, no matter what the hour 
in mind is or the hour selected. 
Our l*nzzle-1tox. 
NUMERICAL ENIGMA.—BIBLICAL PROVERBS. 
1. I am composed of 80 letters; 
The 12, 23, 49, | 77, 44, 61, | 18, 3, 23, 34,38, | 48,62, 76, | 
6, 26, 32, 33, | 5, 64, | 29, 70, 46, is a proverb of truth. 
The 67, 2, 20, 27, 37, | 40, 63, 14, | 43, 19, 49, 11, 16, 32, 1, 
I 78, 1, | 65, 8, 71, 66, 17, 22, 70, 4, is a proverb of caution. 
The 28. | 1, 45, 33, 42, 13. 1 24, 73, 32, 20, 21, 69, 75, | 10. 
54, | 45, 50, 2. 9, 25, 29, 48, 14, 39, 8, 40, | 15, 63, | 18, 35, 36. 
I 33, 66. 56, 7, is a proverb of honesty. 
The 80, 60, 28, 55, 21. | 23, 72. 1 31, 1 69, 19, 79, 32, 30, | 5, 
62. | 15, 35, 51, | 4, 59, 49, | 38, 63, | 6, 44, 78, 23, &3, 52, | 41, 
2, | is a proverb of education. 
The 59, I 41, 8, 63, 58, | 21. 73, 47, 57, | 10, 27, | 74, 20, 34, 
19, 68, 22. I 37, 70. | 12. 13, I 69, 35, 78, 42, 16, 29, j 43, 38, 
28, 40, | 41, 3, 26, 31, 46, | 17, 25, 69, 44, 36, 54. is a proverb 
of reputation. 
The whole is a proverb of Solomon. Isola. 
NUMERICAL ENIGMAS. 
2. I am composed of 40 letters : 
My 2, 9, 36. 7, 14, 5, 12, 20, was one of the greatest of 
military men. 
My 38, 31, 16, 9. 8, 33, 40, 21, 17, came from a foreign 
land to fight for American liberty. 
My 18, 11, 23, 3, 29, 20, 23, 1, 31, 38, will long be re¬ 
membered. 
My 10, 22, 20, 19, 9, is the birth-place of the discoverer 
of America. 
My 35, 4, 17. 36,9. 30, 24, we often think of with sadness. 
My 18, 28, 15, 23, 9, is one of the oldest nations on the 
earth. 
My 18, 14, 39, 6, 37, 34, was the founder of France. 
Mv 19, 13, 32, means away. 
My 16, 25, 26, 27, is a member of the body. 
My whole is an adage that all young folks ought to re¬ 
member. Ken. C. Hill. 
CHARADE. 
A very little word, my first. 
Used constantly each day; 
A simple pronoun names my next. 
Though ’tis not “ you ” or “ nay." 
And now from out some sacred spot 
Rises my solemn whole. 
To calm and fill the heart with peace. 
Or elevate the soul. 
A Picture Puzzle is a double one; it usually contatns a scene in nature, 
with the lines so arranged, that after a little looking—or it may be that it will 
require a good deal of inspection—the object intended comes out, and ever after 
you can not look at the picture puzzle without seeing it. The one here pre¬ 
sented, is perhaps too evident “on the face of it,” to be much of a study; but 
nevertheless, it shows how the artist can, in some measure, hide one thing be¬ 
hind another, and it will serve very well to show how such pictures are made. 
