The Stark County Democrat. [volume] (Canton, Ohio) 1833-1912, 1878-02-07
.Nlisrtllanfoas.
SCIENCE FOR CHILDREN.
A TNeture on the Subject Of "fieAt, Visible ana
INVISIBLE" by Professor Tyndall'

oently. the first of course OF lectures
adapted to Juvenile auditory, on the
subject of "Heat, Visible and Invisible"
Professor Tyndall said the existence oi
human beings on this earth might be
divided into two great periods-one be-
fore and one after man learned to write
or the prehistoric period and the historic
period. But before man had learned W
write, and while he was what we called
a savage he had learned many things,
spob as TO tame wild animals, the use OF
certain seeds, the building Of houses, and
he had also discovered fire. In the lake
dwellings of Switzerland men baked
bread, though writing was unknown
Learned men were all at sea as to when
fire was introduced on the earth Some
imagined that it might have been discov'
cred through the friction ofboughs sway
ed by the wind. Friction would GER
tainly cause FIRE, but he doubted whether
the friction of Boughs would produce II,
because he ethought the wind would carry
awav all the heat that was generated be-
fore IL had reached the intensity neces'
sarv for ignition. There were likelier
means of the discovery than that. dc
had himself stood on mountain top In
Switzerland and seen forests set on fire
by lightning, and savages seeing the same
thing might we'll have thought it would
be very comfortable to be able to produce
it for their own pleasure. But the real
origin of fire existed deep in the silence
of pre- historic time; and all explana-
tions of that origin were mere supposl-
tion. Another possible source was not
an unlikely one. Every boy and girl
knew something about those wonderful
flint implements which were found all
over the earth; they had been shaped
with great skill, and the sparks struck
out in working them might have been
the source of fire. In Terra del Fuegoo
the savages still used such a means OF
producing fire namely, piece Of iron
pyrites and pebble; and the ordinary
flint and steel used not very long ago IN
this country, was something OF the same
kind. The sparks were particles which
we're struck of, made nearly white hot
with the heat generated by the blow,and
burning in the air. Nothing was more
certain than that heat was produced by
friction, aud every school boy knew that
a button could be rubbed until 1t got too
hot to be held. A bullet struck with
hammer would become warm. The Pro-
fessor illustrated this part of his subject
by boiling sulphuriC ether in brass tube
which was made to rotate in his gloVed
hand, the friction of the tube against the
glove producing the heat, and causing,
by means of the twirling table, a stick OF
beech wood to rotate with great velocity
in hole in piece of mahogany, smoke
being almost Immediately produced, ana
flame bursting out when some combustl-
Bile dust was put into the hole. These
were The continued mechanical means
of generating heat; but heat could also
be produced chemically. Every child
had seen candles and coal burning, but
had the BOYS and girls ever asked them
selves what happened in the burning,a and
what became of the candles and the coaIy
They should learn to ask questions, and
to answer them with perfect truth. In
the first place, lighted candle, to burn,
required air. A lighted candle was here
placed under the receiver of an air pump
and the air was pumped out; as the air
became exhausted the candle burned
more and more dimly, and at last went
out, q spark remaining on the WICK. Oxy-
gen gas was then admitted into the re.
Ceiver, and the spark became larger and
brighter, and burst into fame
The air we breathed, continued Pro-
fessor Tyndall, was for the most part
composed of nitrogen gas and of oxygen
gas, the nitrogen being to the oxygen as
four to one in volume. The nitrogen did
nothing at all to help the combustion OF
coal or candles, but it was the little oxy..
gen contained in the air which caused
the Goals and candles to burn. With
pure oxygen, combustion would be far
more rapid and brilliant. A stream OF
oxygen was here turned into the fire in
the CRATE, causing fierce glow, and was
then turned on to an enber taken from
the CRATE, producing dazzling radiance
IT. continued Prof. Tyndall, the air were
of pure oxygen, the very bars OF the
crate would be burned away like the
coal When he heated rod of carbon,
and placed it in a jar Of oxygen, it would
be seen to burn very powerfully. The
experiment was shown. Now, a boy
would never dream that diamond was
anything like piece of coke, but it was.
Sir Isaac Newton supposed that the dia-
mond was con- bustible, and chemistry
showed that he was right, and that the
diamond was form of carbon. A dia-
moud, when heated and placed in jar
of oxygen gas, would be found to glow
like white star. Experiment shown ]
Faraday used to employ charcoal made
from the bark of wood; the bark was full
of little cells, and the cells were full OF
air, and when piece of burning bark
charcoal was put into jar of oxygen the
air expanded and exploded with sput-
tering sound, and series of sparks was
produced; a stream Of oxygen being di'
Yected into the jar, the sparks would be
driven round and round with beautiful
effect. [The experiment was shown,and
the display of sparks whirled round by
the stream of oxygen was surprisingly
beautiful But oxygen was also capable
of producing combustion when it was in
a solid form. Gunpowder would burn
in gunbarrel without the external air,
the oxygen contained in the saltpetre
burning up the charcoal and the sulphur,
and thus generating those gases which
produced the motion of the projectiles.
These were illustrations of the produc
ton of chemical heat Now, every boy
ought to be experienced in the power of
picturing things in the mind. Many
scientific men occupied more than half
their time in picturing, mentally, things
which never could be seen with the bod
lily eye, for the power Of the mind far
transeended that Ofthe organs of the SEN
ses. He wanted them to picture what
took place when the heated diamond
burned like white star in the oxygen