Copyright
Richard Green Parker.

A school compendium of natural and experimental philosophy : embracing the elementary principles of mechanics, hydrostatics, hydraulics, pneumatics, acoustics, pyronomics, optics, electricity, galvanism, magnetism, electro-magnetism, magneto-electricity, astronomy : containing also a description of online

. (page 24 of 38)
Online LibraryRichard Green ParkerA school compendium of natural and experimental philosophy : embracing the elementary principles of mechanics, hydrostatics, hydraulics, pneumatics, acoustics, pyronomics, optics, electricity, galvanism, magnetism, electro-magnetism, magneto-electricity, astronomy : containing also a description of → online text (page 24 of 38)
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the body in the same manner as from the prime conductor.
While the person remains insulated, he experiences no sensation
from being filled with electricity ; or, if a metallic point be pre-
sented to any part of his body, the fluid may be drawn off
silently, without being perceived. But if he touch a blunt piece
of metal, or any other conducting substance, or if he step from
the stool to the floor, he will feel the electric shock ; and the
shock will vary in force according to the quantity of fluid with
which he is charged.

997. THE TISSUE FIGURE. Fig. 146 is a
dgure with a dress of fancy paper cut into
narrow strips. When placed on the prime
conductor, or, being insulated, is connected
with it, the strips being all electrified will
recede and form a sphere around the head.
On presenting a metallic point to the elec-
trified strips, very singular combinations
will take place. If the electrometer be




ELECTRICITY. 271

removed from the prime conductor, and a tuft of feathers, 01
hair, fastened to a stick or wire, be put in its place, on turning
the machine the feathers or hair will become electrified, and the
separate hairs will rise and repel each other. A toy is in this
way constructed, representing a person under excessive fright.
On touching the head with the hand, or any conducting substance
not insulated, the hair will fall.

How is the 998. The Leyden jar may be charged by pre-
Leydenjar gen ting it to ^he prime conductor when the machine
is worked. If the ball of the jar touch the prime
conductor it will receive the fluid silently ; but, if the ball of
the jar be held at a small distance from the prime conductor, the
sparks will be seen darting from the prime conductor to the jar
with considerable noise.

999. The jar may in like manner be filled with negative elec-
tricity by applying it to the ball on the rubber-post, and con-
necting the chain with the prime conductor.

1000. If the Leyden jar be charged from the prime conductor
(that is, with positive electricity), and presented to the pith-balls
of the electrometer, they will be repelled ; but if the jar be
charged from the brass ball of the rubber-post (that is, with
negative electricity), they will be attracted.

1001. If the ball of the prime conductor be removed, and a
pointed wire be put in its place, the current of electricity flowing
from the point when the machine is turned may be perceived by
placing a lighted lamp before it ; the flame will be blown from
the point ; and this will be the case in what part soever of the
machine the point is placed, whether on the prime conductor or
the rubber ; or if the point be held in the hand, and the flame
placed between it and the machine, thus showing that in all
cases the fluid is blown from the point. Delicate apparatus
may be put in motion by the electric fl uid when issuing from a
point. In this way electrical orreries, mills, &c., are constructed.

1002. If the electrometer be removed from the prime con-



NATURAL PHILOSOPHY.



Fig. 147.




ductor, and a pointed wire be substituted for /t, a wire with
sharp points bent in the form of an S, balanced on it, will ba
made to revolve rapidly. In a similar manner the motion of
the sun and the earth around their common centre of gravity,
together with the motion of the earth and the moon, may be
represented. This apparatus is sometimes called an Electrical
Tellurium. It may rest on the prime conductor or upon an insu-
lated stand.

Describe 1003. A chime of small bells on a stand,
Fig. 147. Fig. 147, may also be rung by means of
brass balls suspended from the revolving wires.
The principle of this revolution is similar to that
mentioned in connection with the revolving jet,
j? 1 ig. 98, which is founded on the law that action
and reaction are equal and in opposite directions.

1004. If powdered resin be scattered over
cotton-wool, loosely wrapped on one end of the

; ointed discharger, it may be inflamed by the discharge of the
battery or a Leyden jar. Gunpowder may be substituted for thf
resin.

1005. The universal discharger is an instrument for
directing a charge of electricity through any substance,
with certainty and precision.

Explain 1006. It consists of two sliding rods, A B and C

tg. 14. j^ terminating at the extremities, A and B, with b r ass
balls, and at the other ends which
rest upon the ivory table or stand
E, having a fork, to which any
small substance may be attached.
The whole is insulated by glass
legs, or pillars. The rods slide
through collars, by which means their distance from one anoth* r
may be adjusted.

1007. In using the universal discharger one of the rods 01
Slides must be connected by a chain, or otherwise, with the out



Fig. 148.




ELECTRICITY* JJY'j

mde, and the other with the inside coating of ftie jar or battery.
By this means the substance through which tke charge is to b<i
sent is placed within the electric circuit.

1008. By means of the universal discharger, any small metal-
lic substance may be burnt. The substance must be placed in
the forks of the slides, and the slides placed within the electric
circuit, in the manner described in the last paragraph. In the
san.6 manner, by bringing the forks on the slides into contact
with a substance placed upon the ivory stand of the discharger,
such as an egg, a piece of a potato, water, c., it may be illu
minated.

1009. Ether or alcohol may be inflamed by a spark communi-
cated from a person, in the following manner : The person stand-
ing on the insulating stool receives the electric fluid from the
prime conductor by touching the conductor or any conducting
substance in contact with it; he then inserts the knuckles of
his hand in a small quantity of sulphuric ether, or alcohol, held
in a shallow metallic cup, by another person, who is not insu-
lated, and the ether or alcohol immediately inflames. In this
case the fluid passes from the conductor to the person who is
insulated, and he becomes charged with electricity. As soon
as he touches the liquid in the cup, the electric fluid, passing from
him to the spirit, sets it on fire.

1010. The electrical bells are designed to show the effects
of electrical attraction and repulsion.

1011. In some sets of instruments, the bells are insulated on a
separate stani ; but the mode here described is a convenient mode
of connecting them with the prime conductor.

1012. They are Fig. 149.



Fig.



plied: The ball
B of the prime conductor, with
its rod, is to be unscrewed, and
the rod on which the bells are
suspended is to be screwed in its



1



'274 NATURAL PHILOSOPHY

place. The middle bell is to be connected by a chain with
the table or the floor. When the machine is turned, the balls
suspended between the bells will be alternately attracted and
repelled by the bells, and cause a constant ringing. If the bat-
tery be charged, and connected with the prime conductor, the
bells will continue to ring until all the fluid from the battery
has escaped.

It may be observed, that the fluid from the prime conductor
passes readily from the two outer bells, which are suspended by
chains; they, therefore, attract the two balls towards them
The balls, becoming electrified by contact with the outer bells,
are repelled by them, and driven to the middle bell, to which
they communicate their electricity ; having parted with their
electricity, they are repelled by the middle bell, and again
attracted by the outer ones, and thus a constant ringing is
maintained. The fluid which is communicated to the middle
bell, is conducted to the earth by the chain attached to it.

Explain what 10 * 3 - SPIRAL TUBE. The passage of the
Fig. 150 rep- electric fluid from one conducting substance to
resents. another, is beautifully exhibited by means of a

^lass tube, having a brass ball at each end, and coated in

Fig. 150.



\he inside with small pieces of tin-foil, placed at small dis-
tances from each other in a spiral direction, as represented in
F?g. 150.

1014. In the same manner various figures, letters and words, may
be represented, by arranging similar pieces of tin-foil between two
pieces of flat glass. These axperiments appear more brilliant in a
darkened room.

1015. THE HYDROGEN PISTOL. The hydrogen
ig. pi s t l is made in a variety of forms, sometime?
ID the exact form of a pistol and sometime? iu



ELECTEICITT.



276



Fig 151



Explain Fig.
152.



Fig. 152.



the form of a piece of ordnance. The form in
Fig. 151 is a simple and cheap contrivance, and
is sufficient to explain the manner in which the
instrument is to be used in any of its forms.
It is to be filled with a mixture of hydrogen
and oxygen, or hydrogen and air. When
thus prepared, if the insulated knob K be pre-
sented to the prime conductor, it wUl immediately explode.

1016. A very convenient and economicai
way of procuring hydrogen gas for this and
other experiments, is by means of the hydrogen

%as gejierator, as represented in Fig. 152, It consists of a gla&*
vessel, with a brass cover, in the centre of which is
a stop-cock; from the inside of the cover another
glass vessel is suspended, with its open end down-
wards. Within this a piece of zinc is suspended by
* wire. The outer vessel contains a mixture of sul-
phuric acid and water, about nine parts of water to
one of acid. When the cover, to which the inner
glass is firmly fix*ed, is placed upon the vessel, the
acid, acting upon the zinc, causes the metal to
absorb the oxygen of the water, and the hydrogen,
the other constituent part of the water, being thus
disengaged, rises in the inner glass, from which it expels the
water ; and when the stop-cock is turned the hydrogen gas may
be collected in the hydrogen pistol, or any other vessel. In the
use of hydrogen gas for explosion, it will be necessary to dilute
the gas with two or three times as much air.

1017. ELECTRICAL SPORTSMAN. Fig. 158
Describe the Elec- represents the Electrical Sportsman, From tht
Incal Sportsman.

larger ball of a Leyden jar two birds, made of

pith (a substance procured in large quantities from the corn-
stalk, the whole of which, except the outside, is composed of
ptfk\ are suspended by a linesn thread, silk, or hair. When the
jar is charged, the birds wil rise, as represented iu the figure,
12




276



NATURAL PHILOSOPHY.



on account of the repul-
sion of the fluid in the jar.

1018. If the jar be then
placed on the tin-foil of the
stand, and the smaller ball
placed within a half inch
of the end of the gun, a
discharge will be produced,
and the birds will fall.



Kg







Explain Fig.
154.



Fig. 154.



n



1019. If images, made of pith, or small
pieces of paper, are placed ut,der the insulated
stool, and a connection be made between the
prime conductor and the top of the stool, the images will be
alternately attracted and repelled ; or, in other words, they wii>
first rise to the electrified top of the stool, and thus becoming
themselves electrified, will be repelled, and fall to the ground,
the floor, or the table ; where, parting with their
electricity, they will again be attracted by the
stool, thus rising and falling with considerable
rapidity. In order to conduct this, experiment
successfully, the images, &c., must be placed
within a short distance of the bottom of the
stool.

1020. On the same principle light figures
may be made to dance when placed between two
discs, the lower one being placed upon a sliding
stand with a screw to adjust the distance, and

the upper one being suspended from the prime conductor, as in
Fig. 154.

1021. A hole may be perforated through a quire of paper,
by charging the battery, resting the paper upon the briss ball
of the battery, and making a communication, by means of the
jointed discharger, between the ball of one of the jars, and the
brass ball of the box. The paper, in this case, will be between
the ball of the battery and the end of the discharger.




KLECTK1UITY. 277

1022. Gold-leaf may be forced into the pores of glass by
placing it between two slips of window-glass, pressing the slips
of glass firmly together, and sending a shock from a battery
through tdem.

If gold-leaf be placed between two cards, and a strong charge
be passed through them, it "will be completely fused.

1023. When electricity enters at a point, it appears in
the form of a star ; but when it goes out from a point, it
puts on the appearance of a brush.

1024. The thunder-house, Fig. 155, is de-
/)escnei Fig. s i gne< j to s h ow the security afforded by light-
ning-rods when lightning strikes a building
This is done by placing a highly-combustible material in th
inside of the house, and passing a
charge of electricity through it. On
the floor of the house is a surface of
tin-foil. The hydrogen pistol, being
filled with hydrogen gas from the
gasometer, must be placed on the floor
of the thunder-house, and connected
with the wire on the opposite side.
The house being then put together, a chain must be connected
with the wire on the side opposite to the lightning-rod, and the
other end placed in contact either with a single Leyden jar or
with the battery. When the jar, thus situated, is charged, if a
connection be formed between the jar and the points of the
lightning-rod, the fluid will pass off silently, and produce no
effect. But, if a small brass ball be placed on the points of the
rod, and a charge of ele^tncity be sent to it from the jar or
the battery, the gas in the pistol will explode, and throw the
parts of the house asunder with a loud noise.

1025. The success of this experiment depends upon the proper con-
nection of the jar with the lightning-rod and the electrical pistol.
On the side of the house opposite to the lightning-rod there is a
wire, passing thrrugh the side, and terminat?iig on the outside in a




278 NATURAL x-HILOSOPilY.

hook ^ 'hen the house is put together, this wire, ir the inside-
must touch the tin- foil on the floor of the house. The hydrogen
pistol must stand on the tin-foil, and its insulated knob, or wire, pro-
jecting from its side, must be connected with the lower end of the
lightning-rod, extending into the inside of the house. A communi-
cation must then be made between the hook on the outside of the
house and the outside of the jav, or battery. This is conveniently
done by attaching one end of a chain to the hook, and holding the
other end in the hand against the side of a charged jar. By pre-
senting the knob of the jar to the points of the lightning- rod no
effect is produced ; but if a brass ball be placed on the points at P,
and the knob of the jar be presented to the ball, the explosion will
take place. If the charged jar be very suddenly presented to the
points, the explosion may take place ; and the jar may be silently
discharged if it be brought very slowly to the ball. The thunder-
house is sometimes put together with magnets.

What is light- 1026. The phenomena of lightning are
ning and thun- caused by the rapid motion a; vast quanti-
ties of electric matter. Thunder is the noise
which accompanies the passage of electricity through the
air.

What is sup- 1027. The aurora borealis (or northern
posed to be the lights) is supposed to be caused by the electric

cause of the fluid pass i ng through highly-rarefied air ; and

northern lights? 9 . J

most of the great convulsions of nature, suca

as earthquakes, whirlwinds, hurricanes, water-spouts, &c., are
generally accompanied by electricity, and often depend upon it

1028. The electricity which a body manifests by being brought
near to an. excited body, without receiving a spark from it, is
said to be acquired by induction. When an insulated but un.
electrified conductor is brought near an insulated charged con-
ductor, the end near to the excited conductor assumes a state
of opposite electricity, while the farther end assumes the same
kind of electricity, that is, if the conductor be electrified
positively, the unelectrified conductor will be negative at the
nearer end, and positive at the further end, while the middle
point evinces neither positive nor negative electricity. [See
No. 993.

1029. The experiments which have now been described exem-



ELKOTKIOITY.

all the elementary principles of the science of electricity
hese experiments may be varied, multiplied, and extended in innu-
merable forms, by an ingenious practical electrician. Among other
things with which the subject may be made interesting, may be
mentioned the following facts, &c.

1030 A number of feathers, suspended by strings from an insu-
lated conducting substance, will rise and present the appearance of
a flight of birds. As soon as the substance is discharged, the
feathers will fall. The experiment may be varied by placing the
sportsman on the prime conductor, without the use of the Leyden
jar, to which the birds are attached.

1031. Instead of the Leyden jar, a plate of common glass (a pane
of window-glass, for instance) may be coated on both sides with
tin- foil, leaving the edges bare. A bent wire balanced on the edge
of the glass, to the ends of which balls may be attached, with an
image at each end, may be made to represent two persons tilting, on
the same principle by which the electrical bells are made to ring.

1032. Miniature machinery has been constructed, in which the
power was a wheel, with balls at the ends of the spokes, situated
within the attractive influence of two larger balls, differently electri-
fied. As the balls on the spokes were attracted by one of the larger
balls, they changed their electrical state, and were attracted by the
otb^r, which, in its return, repelled them, and thus the motion being
ghen to the wheel was communicated by cranks at the end of the
axle to the saws above.

1033. When the hand is presented to the prime conductor, a
spark is communicated, attended with a slightly painful sensation.
But, if a pin or a needle be held in the hand with the point towards
the conductor, neither spark nor pain will be perceived, owing tc
the attracting (or, perhaps, more properly speaking, the receiving.)
power of the point.

1034. That square rods are better than round ones to conduct
electricity silently to the ground, and thus to protect buildings ;
may be proved by causing each kind of rod to approach the
prime conductor when charged. It will thus be perceived that,
while little effect is produced on the pith-balls of the electrom-
eter by the near approach of the round rod, on the approach
of the square one the balls will immediately fall. The round
rr.d, also, will produce an explosion and a spark from the ball
r.f the prime conductor, while the square one will draw off the
fluid silently.

103.^. The effects of pointed conductors upon clouds charged
with electricity may be familiarly exemplified by suspending a
small fleece of cotton-wool from the prime conductor, and



280 NATURAL rillLOSOPilY.

other smaller fleeces from the upper one, by small filaments.
On presenting a point to them they will be repelled, and all
drawn together ; but, if a blunt conductor approach them, they
will be attracted.

1036. From a great variety of facts, it has been ascertained,
that lightning-rods afford but little security to any part of a
building beyond twenty feet from them ; and that when a rod is
painted it loses its conducting power.

What are the 1037. The lightning-rods of the most ap-
best kinds of proved construction, and in strictest accordance
with philosophical principles, are composed of
*maR square rods, similar to nail-rods. They run over the
building, and down each of the corners, presenting many
elevated points in their course. At each of the corners, and on
the chimneys, the rods should be elevated several feet above the
building. If the rods are twisted, it will be an improvement,
as thereby the sharp surfaces presented to collect the fluid will
point in more varied directions.

1038. The removal of silk and woollen garments, worn during the
day in cold weather, is often accompanied by r. slight noise, resem-
bling that of sparks issuing from a- fire. A similar effect is pro-
duced on passing the hand softly over the V,ck of a cat. These
effects are produced by electricity.

1039. It may here be remarked, that the verms positive and nega-
tive, are merely relative terms, as applied to the subject of electric-
ity. Thus, a 'body which is possessed of its natural share of
electricity, is positive in respect to one that has less, and negative
in respect to one that has more than its natural share of the fluid.
3o, also, one that has more than its natural share is positive with
regard to one that has only its natural share, or less *lian its natu-
ral share, ,and negative in respect to one having a larger share
than itself.

1040. The experiments with the spiral tube connected with Fig
150 may be beautifully varied by having a collection of such tubes
placed on a stand ; and ajar coated with small strips, resembling a
brick wall, presents, when it is charged, a beautiful appearance ir,
she dark.

1041. The electric fluid occupies no perceptible space of time
in its passage through its circuit. The rapidity of its motion ha*
been estimated as high as 288,000 miles in a second of time. B
always seem? to prefer the shortest passage, when the conductors



ELECTKIC1TY. 2bl

ire equally good. Thus, if two, ten, a hundred, or a thousand or
more persons, join hands, and be made part of the chcuit of the fluid
in passing from the inside to the outside of a Leyden jar, they will
ill feel the shock at the same moment of time. But, in its passage,
the Quid always prefers the best conductors. Thus, if two clouds,
iifterently electrified, approach one another, the fluid, in its passage
iTom one cloud to the other, will sometimes take the earth in its
course, because the air is a bad conductor.

1042. In thunder-storms the electric fluid sometimes passes from
the clouds to the earth, and sometimes from the earth to the clouds
and sometimes, as has just been stated, from one chnid to the earth,
and from the earth to another cloud.*

What are 1043. It is not safe, during a thunder-storm, to

comparatively take shelter under a tree, because the tree attracts
safe and un- the fluid and the human body being a better con .
safe positions . *

during a ductor than the tree, the fluid will leave the tree

thunder-storm? an d p ass into the body.

It is also unsafe to hold in the hand edge-tools, or any sharp
point which will attract the fluid.

The safest position that can be chosen during a thunder-storm
is a recumbent posture on a feather bed ; and in all situations a
recumbent is safer than an erect position. No danger is to be
apprehended from lightning when the interval between the flash
and the noise of the explosion is as much as three or four sec-
onds. This space of time may be conveniently measured by the
beatings of the pulse, if no time-piece be at hand.

1044. Lightning-rods were first proposed by Dr. Franklin, to whoa,
is also ascribed the honor of the discovery that thunder and light-
ning are the effects of electricity. He raised a kite, constructed of a
silk handkerchief adjusted to two light strips of cedar, with a
pointed wire fixed to it ; and, fastening the end of the twine to a key,
and the key, by means of a piece of silk lace, to a post (the silk lace
serving to insulate the whole apparatus), on the approach of a

* Lightning appears under several different forms. That which appears
when the discharge takes place between two clouds at some distance apart,
or between a cloud and the earth, exhibits a bright zigzag narrow band of
light, and is called popularly o/iam-lightning. The irregular path is prob-
ably caused by the resistance offered Toy the air to the current or electrical
impulse. When two clouds slightly charged with different electrieitlos ap-
proach each other, the discharge is from a great many points at the same
time, and the appearance of a broad flash has entitled it to the name of
s7^-lightning. A third form of lightning is called JaZMightning ; no satis-
factory explanation of it has yet been given. It appears like a bright ball of
flame, moving no faster than a man can walk ; it explodes violently after a
few seconds.



282 NATURAL PHILOSOPHY.

thunder- cloud, he was able to collect sparks from the key, to charge
Leyden jars, and to set fire to spirits. This experiment established
the identity of lightning and electricity. The experiment was a
dangerous one, as was proved in the case of Professor Richman, of



Online LibraryRichard Green ParkerA school compendium of natural and experimental philosophy : embracing the elementary principles of mechanics, hydrostatics, hydraulics, pneumatics, acoustics, pyronomics, optics, electricity, galvanism, magnetism, electro-magnetism, magneto-electricity, astronomy : containing also a description of → online text (page 24 of 38)