The Sun.
London, England, 1855-12-26 00:00:00

RETFORD WORKING MEN'S iSSOCIA

TION.

LECTURE ON " INTERESTING AND EVERY-
DAY THINGS IN SCIENCE."
The crowded state of our columns last week prevented
us from giving the Rev. H. C. Mitchinson's very useful
and interesting lecture at the above association on the
evening of the 12th instant. We to-day present to our
readers the rev. gentleman's remarks in their entirety.
It may be essential to premise that the lecturer gave ,
additional force to his remarks by many well-arranged I
appropriate illustrations ; and succeeded in rivetting the
attention and eliciting the frequent applause of a largo
and respectable attendance of members.
The CHAIRMAN (the Rev. Arthur Brook) having in-
troduced
The Rev. H. C. MITCHINSON, he spoke as follows :
I have thought since I gave a name to my subject that
I have given one rather liable to be misunderstood ;
and some persons, mistaking the use of the word
" interesting" may have thought me presumptuous.
Now I beg to explain, that I never meant to say that
my paper would be necessarily an interesting one, but
that the subjects of which it will treat are interesting in
themselves ; for it is possible to treat interesting things
in such a manner as to make them very uninteresting.
And with regard to the word " every-day," as applied
to some of the things I shall introduce, it is surprising
' how ignorant even well-educated people are of "common
things" in ecienoe ; and, it may be, we have often been
ashamed and vexed with ourselves at not being able to
answer the frequent " why" of our children about some
every-day occurrence. You have probably most of you
heard the tale of that king, who, though in many respects
a beautiful character, was rather weak in intellect ; I
mean George 111. It is told of him that he was ex-
gaoret
itnr es
fnid ee Iya perplexeddunlnlf
ng w iNt ho thevr I questiontnfnk
ahnoyw p
earpsop lne
ss
ignorant of things nearly as simple as this ; or if they
will not allow that—if they do not like to assent to
being as ignorant of the worthy king—l do think we
may all imitate his disposition to inquire into simple
understand.
subject to
It is
supposeperhaps v
ey
wellr
itnilinagdsdrtehsastinwgepdeo notrsons on any
little previous knowledge—to explain the very elements
and if there should be any here who understand science
in its various branches, they will excuse me if I seem to
give credit for very little previous knowledge ; they will
not sit impatiently when they remember that all have not
their abilities, or perhaps with equal if not superior
abilities, have not had their opportunities. I have
chosen a broad field of subjects, but my ranging that field
will be limited by the necessity of choosing, what requires
as little previous explanation as possible. I hops, too,
at intervals, as we pass along, to call your attention to
the wisdom and benevolence of God ;—his wisdom in the
admirable contrivance which marks his works, his bene-
volence in so contriving them as to promote man's happi-
ness. I will begin with the shape of the earth. You all
know it is a sphere or globe, i. e., round, not like a shilling,
but like an orange. But how can this be proved. As far as
you or I can tell,it is as flat as the floor of this room. Now
there are two or three ways in which this may be proved.
One is, if you are standing on the sea-shore and watch
a ship approaching, you see the topmast first, the hull er
body of the ship last. (Fig.) Another way by which it
is proved that the earth is round is this. The moon is
eclipsed When the earth comes between it and the sun
(fig.) ; the shadow of the earth is then cast upon the
moon, and in all positions that shadow is round ; accord-
ingly, the earth must be of the form of a globe, for that
is the only shape which will cast a round shadow in all
youmovesallkw
roundno tihtsaatxftsh.e sFuonr
astalonndgs
st
itmi positions.lle,
iatnwd tslh
though—as
uepapr tohste
you or I should—that the earth
stood still, and the sun and other heavenly bodies moved.
But if I give you an illustration you will see that the
appearance of things is the same to a man standing on the
earth; whether you suppose the earth to stand still and the
sun to move, or the earth to move and the sun to stand
still. If you are in a railway train which is moving and along
side on the other line of rails there is another train standing
still, if you watch the standing train it appears to be
moving, and the one you are in appears to stand still.
Or if you are sailing in a boat, you could, by looking at
the bank, fancy it was gliding in an opposite direction,
and that the boat was stationary. Galileo discovered
that the earth goes round the sun. And perhaps we
shall not so much wonder that he was denounced as a
heretic and blasphemer, placed in a dungeon, and brought
to take his trial before the Inquisition, for he seemed to
be setting up his opinion against the Word of God, In
the Book of Joshua we read, that God allowed Joshua to
work a miracle, which is thus described :—" And the
sun stood still, and the moon stayed until the people
had avenged themselves on their enemies." Now if this
had been described by the inspired historian now, he
would have said that the earth ceased to revolve upon, its
axis a whole day, so that that part of it on which the
-Jews were did not pass out of reach of the rays of the
sun. And it was perfectly reasonable that, he should
describe the miracle aecording to the then knowledge of
astronomy and the appearance of things. Every one
has observed how much larger the sun and moon seem at
their rising and setting. It is explained in this way ;
objects look larger through the medium of mist : and
at setting or rising the sun is more horizontal to us,
and therefore seen through the vapours that cover the
earth. This leads me to tell you a little about light.
Light travels so fast that it would go eight times round
the earth while a person counts one. In fact, some of
the fixed stars ars so distant, that if they were quenched
their rays for three years after would continue to reach
us, and would make it appear in its usual place. Sight
is produced by rays from the sun, moon, or any source
of light, reflected from objects we look upon, striking
and picturing themselves upon our eye. Thu,, some
sub tances are very brilliant, because they are peculiarly
suited to reflect light (as glass, steel) ; others, like lead,
are dull because they abiorb a great deal of light. You
all know that when you leave the gas-light of a town, or
d
srruct
itcap,
sheahehlrlreemomenefli
nesnwi
aaaordrtot
tsyrenvrnet.kotuesee:
rympdnnnesuaesAeoab:wa:
flattened,
teodsi
upon
aahbha
adapting
distancetaot
dh
birdsigui
nneegtgahp:.
wgeatr
etoi
any light in a house, how dark it appears at first, .sei
the principle that the pupil of the eye is so constituted
as to contract very much when we are in a powerful
light, otherwise it would allow the optic nerves to be
overloaded with rays ; acc)rdingly when we go into the
dark, the pupil of the eye is at first too much contracted
to collect sufficient rays from the dark objects around ;
but by degrees it dilates, adjusts itself to the quantity
of light, admits more rays, and wo begin to say it is not
so very dark after all. Hence cats and owls sleep most
of the day, because the pupils of their eyes are broad, se
they close their eyes for relief; whereas at night they can
see very well, bemuse the broadness of their pupil astmits
rays plentifully. I will here endeavour to explain to
you short and long sight. A short-sighted person can
only ace an object near his eye. A long-sighted person
cannot see things near, but distant objects. Now vision
consists in a picture being formed on the network
which lines the back of the eye—this network is
called the retina.—[The rev. gentleman here exhibited
drawings illustrative of this part of his subject.]—You
writing
Ttl
anhnpgeye
rttehehpafel
anything
reason
theyhai
sen, ntt ththweoe
ahyrnuehtmaadotv,
to examine,
humours
seon
xooaaft
mdt
hiitheirsneteiar,
distance
ecysoeper
from
rac
are
uhbscdoepiiuf
rrsorordncmoento,
emshrattrnhrahotiaeeneshwani
dert,rgnoeeerbtooyobi
oerneoefns
.afdhhery
voobinsbroAnydi
itoettnlnnahtdphleeteadeehoraoiesrtnibortets
isoaefstenfi
IcronGottefaehbetujeiaiiei
fromeronya ei
wouldgdsre.
beak, it is necessary that they should be able to see
very near objects dFisatypinuctntlosyoilicelogNseoo
to fwloatnhge sight
ey
person
ioirisdtiinnagruyisheignhottng if
—hit o
oiwtbi jt emhc
ati
its
ssbeak.ee must be r
y to
neart Consequentlyh the
bird's
objects
eye
the
bird,when
distinctly, tn t
must
orderl
ut es st h
i have
ta tit
val pyet
short sight. On the other hand, from being often ele-
vated much above the ground, living in the air, and
moving
tsharfoeut
safety,
as it
wellw t hasgfruera
at
sssiwstiff
nt
gnestsh,
them
mhefyi
for
descry-
ingtheir their prey, a power of seeing at a great distance ; in
e as with
ordinary
, h
other words they ought to be long-sighted. Birds of
a ntdhelyon are.g.s i
ra-
pinele are surprising examples of this; indeed has it not
itnogbe eagle-eyed And
short-sighted so become a proverbial expression to speak of a person be-
gßteirdd-slbtohtli then, ought
ug
to
see things very close and at a great distance. They
have muscles so constructed that, on the one hand, they
can flatten their eye and so become long-sighted, and
view very distant objects ; on the other, they can make
the eye prominent, and so become short sighted, and
view very near objects. Is not this an admirable ar-
rangement ? Surely God doth all things well. I will
now pass on to tell you something about sound. In
the production of sound there are three things to be
noticed—a sounding
body, as a bell for instance ; a
conducting medium, as the air; and an organ of hear-
ing, as the ear. We have all of us been boys in our
time, and have most probably had a boy's propen-
sity to throw stones ; and we have observed the effect
of throwing a stone into water, how
tance the water is disturbed by circling ripples. This
will servo to illustrate sound ; a bell, suppose, is struck—
this causes vibrations or waves in the air which sur-
rounds it, and the waves come on and on, until one
strikes upon my ear and I hear it, and another strikes
upon yours and you hear it, and so every one hears it
who is near enough, whereas those far off do not, be-
cause the waves of sound, like the waves of water caused
by the stone, become weaker and weaker, and at last
imperceptible. And here I would explain why it is
that we see the flash of lightning before we hear the clap
of thunder. The flash and the sound really take place
at the same time, the thunder being caused by the com-
ing together of the air again after it has been parted
by the lightning flash. Why then do we not see the
flash and hear the clap at the same moment; because
light travels nearly a million times faster than sound ;
accordingly we see the flash almost the very instant
the discharge of electric fluid takes place; but we do
not hear the sound until some time after ; in fact,
sound and thunder takes a whole second to travel 300
yards. Some things conduct sounds better than others.
Wood is a good conductor, as may be
proved in this.
way—the ticking of a watch at one end of a piece of
timber is distinctly heard at the other. Sound is also
well conducted over still water and ice. All sounds
move with the same swiftness through the came medium.
For instance, in a long music-hall, all the sounds har-
monise upon the ear of a person at the further end from
the musicians. This would net be so unless all the
sounds travelled at the same pace. To exemplify what
I mean, suppose a fiddle, a flute, and a cornet were
all together, to play together the notes A, B, C, D,
consecutively in a piece of music ; unless all rounds
travelled (in same medium) at the same pace, we should
have some such result as this—when a person at a dis-
tance heard the last part of the note A from the fiddle,
the flute would be just sending upon the ear the com-
mencement of B, and so on, and an endless confusion of
sounds would at the same moment reach his ear. I
will here say something about echo. Whenever a

sound-wave strikes against any obstacle, as a wall, hill,
or mound of earth, it is thrown back, and this sound is I
called an echo. Small buildings where the walls are
near the speaker do not produce an audible echo, be-
cause the echo and original sound strike the ear at the
same time. But in a cathedral, where the walls are
some distance from the " thing giving sound," there is
an audible echo, because the sound does not return to
the ear until the first sound has died away. Sound
travels 380 yards in a second. I will suppose an object,
as a mountain for instance, is that distance from me ;
I shout ; I hear the shout directly by ono of the sound
waves striking on my ear. In two seconds I shall hear
the echo, that is, one of the sound waves sent back from '
the mountain ; two seconds, you observe—for it will
have taken a second to go the 380 yards, and a second
to return. suppose I were to play a line of music
containing 10 notes, each a second in length, and sup-
pose a reverberating surface (a mountain) 3,800 yards
off; when I have done the 10th note, the echo of the
first note will just be leaving the mountain to come
back to me, and in 10 seconds I shall hear it and all the
others following in regular order ; in fact the echo will
play the line of music through. If I suppose half the
distance, with the seine number of notes, the echo
would begin to play the line of music immediately I had
done. Brewer, in his " Guide to Science," gives a very
remarkable instance of echo. " Seventeen miles above
glasgow, in Scotland, is a very remarkable echo. If a
trumpeter plays a tune, the echo will begin the same
tune and repeat it all accurately ; as soon as this echo
has ceased, another will echo the same tune in a lower
tone ; and after the second has ceased, a third will suc•
ceed in a feebler tone." Deafness, I may here remark,
is often caused by the drum of the ear, i.e., the part
upon which the sound strikes, being injured. If you
make a hole in a tambourine, for instance, it will sound
very imperfectly. It is just so with the ear. When the
tympanum or drum of the ear is broken, it answers to
the waves or sound very imperfectly. Those of you
who visited the Groat Exhibition of 1851 call to mind
the sulky boy with his broken drum, and you have
before you an illustration of the cause of many a per-
son's deafness. I will now tell you a little about the air
we breathe. All air, when heated, ascends. Hence the
pulpit is a hotter place than the body a church ; the gal-
lery of any building is hotter than the floor. This prin-
ciple, that air when heated ascends, will explain to us
why a balloon goes up. When the cotton or sponge is
set fire to, this heats the air inside the balloon, which
thereby becomes light and ascends and takes up the bal-
loon with it ; when the spirit is burnt out, the air inside
the balloon becomes cold and heavy and descends, and
the balloon comes down too. Sense of you, I doubt not,
have visited the sea. Has it ever struck you as singular
that the breeze should always be towards the land ? The
reason of it is this : the earth and the air near it is more
heated than the sea and the air near it. The warmer air,
therefore, from the earth ascends, and cool air from the sea
comes to supply its place, and we on laud always feel a
breeze inland. Though I believe in the evening the breeze is
in the opposite direction, which is accounted for in this way,
that the earth cools down faster than the sea. Accord-
ingly a little time after sunset the air on land is cooler
than that at sea. The warm sea air ascends, the cold
land air goes out to supply its place. In the evening,
for a short time after sunset, the breeze is seawards.
Similarly if you hold a candle at a crevice near the top
of a door, the flame will blow outwards, because the
warm air from the floor of a room has ascended there,
and is escaping ; whereas if you put it down near the
bottom of the door, the flame will blow inwards, be-
cause cold air is rushing in at the bottom to supply the
pla,c3 of the ascending warm air. I may pass on to
tell you a little about heat ; and first as to what is
called the conduction of heat. Now a poker made of
metal and made red hot will best show you what is
meant by the conduction of heat. If the poker is red
hot at one end, it will soon be hot all its length, be-
cause the heat of the red end has been communicated
or conducted throughout the whole poker. Now the
same will not take place if you heat a piece of wood
at one end, because wood is a bad conductor, i.e., will
not transmit heat through its extent. Hence it you have
a metal tea-pot, the handle will feel very hot, because it
will conduct or convey the heat to our hand ; whereas a
wooden handle, or the metal handle with a little piece of
wood or ivory between it and the body of the hot tea-
pot, would not feel it, the wood would not allow the heat
to be conveyed unto our hands to burn them. Hence
some cooking vessels are made with wooden hand,es—
kettle•holders, too, of wood or worsted material, which
are bad conductors. Now if a good conductor is warmer
than the thing it touches, it will impart heat to that
thing ; if it is colder, it will take heat Irons it. The hearth-
stone, which feels so cold, is really of the maims temperature
as the hearth rug, which foie so warm. And why ? Be-
cause the stone is a good conductor, and conducts heat
away from the bare feet if placed upon it, and makes them
feel cold ; but the hearth-rug is a bad conductor, and does
not conduct heat away. The earth is a bad conductor,and
herein we see the wisdom of God ; for were it a good
one, it would convey in the summer heat to dry up the
springs, and in the winter, cold to kill the roots of trees.
Hence water in a spring is cool in summer. Under-
ground cellars are warmer in winter than the air above-
ground, because the earth will not conduct the c )1d down
to them—on the contrary, they are cooler in sacener be-
cause the earth will not conduct the heat to them. Air
is a bad conductor; hence woollen garmeats are warm
they have a great deal of air entangled amongst the fibres
of the wool, and the air does not convey away war ntli
from the body. When the Psalmist says—" The Lord
giveth snow like wool," he means not only that it is white
as wool, but warm as wool, because air is entangled in
the crystals of snow, and being a bad conductor deer not
convey heat away from the body. Hence persons who
have been buried in snow have been discovered not only
alive, but quite warm. I would now say a little about ab-
sorption of heat. To absorb heat is to suck it up as a sponge
does water. The dark colours are found to absorb heat—
the light ones to throw it eff by reflnxion. Accordingly
a black hat is warmer than a white one ; the former
_ se _farreflects it. throws
urtun, will, it r may so speak, ho.ko Dimming to U 0 with
it. There is an old riddle, " Why does a miller wear a
white hat ?" the answer to which is, " to keep his bead
warm." We see, however, that some persons wear a
white hat to keep their head cool. But if black is a warm
colour, and white a cool one, how comes it that the in-
habitants of hot countries are black—those of cold coun-
tries white. Is not the God of nature at fault here ? No,
indeed not; for it is found that black will not blister,
white will. If you place a black cloth glove on one hand
when the sun is burning hot, and a white cloth one on
the other, you will find the hand which has the white
glove on cooler indeed, whereas the hand covered by the
black one will feel hotter, but will not be scorched. It
may be asked, too, why in the polar regions the bear is
white, if that is the coolest colour. I think this is the best
interpretation, and a satisfactory one, that God has so or-
dered it, that he may in some measure not afford so strik-
ing a mark for the hunters. Being the same colour as the
snow, he is not so easily distinguished. Apropos of co-
lour, did it ever occur to you what eves the reason that
anything blue looks green by candlelight. You know
that yellow and blue, mixed together, make green. The
dress is blue, the flame of the candle is yellow; and these
colours combining the dress appears green. And before
I leave the subject of heat, how is it that it is colder in
a thaw than in a frost ? When the waters of our ponds,
lakes, or rivers are frozen over, heat must be obtained
from some source before the ice can be converted into
water. Accordingly the heat of the air, instead of warm-
ing us, is employed in melting the ice. Similarly we
may explain why people often feel chill after eating.
Is it not the case that if you go out into the cold after
a good dinner, you often feel cold ? The reason is
that the heat of our frames leaves the surface of the
body, and is employed within in digesting our food.
You will tee how important heat is for promoting
digestion, if you remember what effect it has in
putrifyiug and rotting meat. I shall, before 1 On-
elude, explain a few "every-day" things, which I can•
not exactly classify under any particular heads. First,
blowing bubbles : soap water is always used—why ?
Because soap makes the water sticky, and prevents the
bubbles from bursting as soon as they are formed. But
why should they ascend ? Because they are filled with
warm brsath, which is lighter than air. Again, why do
water pipes burst in cold weather ? Because water, un-
like other things, expands by cold. In fact, nine cubic
inches of water, when frozen into ice, becomes ten cubic
inches, and, of course, the water, when frozen, wantiny
more room, pushes at the ; pipes and they burst just as
a growing boy bursts his jacket. Again, why should an
egg get hard by being allowed to stand with the shell
unbroken—whereas if you break the top it does not ? In
this way, cooking an egg, whether by boiling or poach-
ing, has a tendency to make the liquid inside solid.
This is partly done on the fire ; then if the egg is taken
out, and the shell unbroken, the heat is confined, and
the cooking process goes on within, and it becomes
harder and harder—whereas if you break the shell the
heat escapes, and the cooking ceases. Again, you are
most of you acquainted with those toys to show what
sort of weather there is likely to be ; a man coming out
in wet weather and a woman in dry. This is explained
as follows : wet shortens string, catgut, Sec. ; accordingly
some catgut is so twisted that when it is shortened by
the moisture in the air the man is forced out—when it is
lengthened again by the dryness of the air it sends the
woman out. Similarly fiddle-strings snap in wet wea-
ther, because, having a tendency to "run up, and the
screws preventing it, they break. I will not trespass
further on your attention with "every-day things in
science," lest from tediousness they should prove unin-
teresting. In conclusion, I would say that my object
has been to excite an interest in those who have not yet
dabbled in science—in fact, my own knowledge of it is
so limited that I could hardly hope to interest those
who probably know more than I do. I say my object
has been to excite inquiry on such matters. In fact I may
not unaptly compare myself to one of those men who
stand outside a show at a fair, and not only proclaim the
clever performances that are to be seen within, but prio-
duce a few outside, to whet the appetite of the admiring
crowd—hoping they will seek their full gratification
within. I, my friends, may compare myself to the man
dressed in spangles, and endowed with a loud voice. I,
this evening, as it were, stand on the stage, outside the
theatre of science. I have shown you a sample of the
rnystelies which are performed within its ample and capa-
cious apartments. And though I cannot say to you, as I
have heard those showmen say, "if you are not satisfied,
you shall have your money returned"—forshould you find
n
olytyyhtooomh
euuul
Chemistry,e
arri
rhnysnit mvodaAeneseenwioy)t
dofsa
hbtoscs
auakt:
Scientific
ndketbtrolebi
effieyaai
en
itt
scienceDrhs
oeul
tgaohgfaseoertstgUsewurdi
eeneeyod: ,
cannot,
words
enoolsnuaneyincri
Health
ftpuuti
library;
d not compensate
you—yet, I will say, I am confident you will not want
yerwraaveri
nreml eydlnp ifind
oeyoyuaaohoul utnuhh.
,tiAto t visit
andnbat deost
somewlsat cursorily, examine the course of nature without
laying of every creation of God what the Psalmist said

of man, that "It is wonderfully made ;" and such an in-
vestigation will, when made in a right spirit, excite ad-
miration of the wisdom, and gratitude for the benevo-
lence of that Being who "created all things, and by