Forgive me for going to be rude in displaying a large piece of text in reply to get a little headstart in such observations
.This wonderful series of lectures although a little dated by now, I personally think it still is given a nice view of some of the basics of physics . In my opinion Faraday has a wonderful way of transmitting knowledge gained from experimentation and like Tesla was not scared to get there hands dirty. Also one thing is that it reflects some insights into how forces can transform and interrelate, which seems present to the current subject. Also Faraday's researches into the electro-magnetic of course predate Maxwell and thus also the electron is not yet there in the considerations. Also it is made very clear by Faraday is the relation of electricity and magnetism.
For those who wish to find some more information, I will refer to the source of the text I used:
Also I could refer to Rudjer Boskovic (Boscovich, 1711-1787), as he was of influence on Faraday, Tesla and lots of others.
Once again apologies for the large text but I think it is the only way to do justice to a grand scientist and philosopher as I deem Faraday to be.
Let us now consider, for a little while, how wonderfully we stand upon this world. Here it is we are born, bred, and live,
and yet we view these things with an almost entire absence of wonder to ourselves respecting the way in which all this
happens. So small, indeed, is our wonder, that we are never taken by surprise; and I do think, that, to a young person
of ten, fifteen, or twenty years of age, perhaps the first sight of a cataract or a mountain would occasion him more
surprise than he had ever felt concerning the means of his own existence ; how he came here; how he lives; by what
means he stands upright; and through what means he moves about from place to place. Hence, we come into this world,
we live, and depart from it, without our thoughts being called specifically to consider how all this takes place; and were
it not for the exertions of some few inquiring minds, who have looked into these things and ascertained the very
beautiful laws and conditions by which we do live and stand upon the earth, we should hardly be aware that there was
anything wonderful in it. These inquiries, which have occupied philosophers from the earliest days, when they first
began to find out the laws by which we grow, and exist, and enjoy ourselves, up to the present time, have shown us that
all this was effected in consequence of the existence of certain forces, or abilities to do things, or powers, that are so
common that nothing can be more so : for nothing is commoner than the wonderful powers by which we are enabled to
stand upright they are essential to our existence every moment.
It is my purpose to-day to make you acquainted with some of these powers ; not the vital ones, but some of the more
elementary, and, what we call, physical powers ; and, in the outset, what can I do to bring to your minds a notion of
neither more nor less than that which I mean by the word power or force ?
Now, I want you to endeavour to comprehend that when I am speaking of a power or force, I am speaking of that which
I used just now to pull over this piece of paper. I will not embarrass you at present with the name of that power, but it is
clear there was a something in the shell-lac which acted by attraction, and pulled the paper over this, then, is one of
those things which we call power, or force; and you will now be able to recognise it as such in whatever form I show it
to you. We are not to suppose that there are so very many different powers ; on the contrary, it is wonderful to think
how few are the powers by which all the phenomena of nature are governed.
I now shall try to help your attention to what I may say by directing, to-day, our thoughts to one kind of power. You see
what I mean by the term matter -any of these things that I can lay hold of with the hand, or in a bag (for I may take hold
of the air by enclosing it in a bag) -they are all portions of matter with which we have to deal at present, generally or
particularly, as I may require to illustrate my subject. Here is the sort of matter which we call water it is there ice
[pointing to a block of ice upon the table], there water [pointing to the water boiling in a flask] here vapour you see it
issuing out from the top [of the flask]. Do not suppose that that ice and that water are two entirely different things, or
that the steam rising in bubbles and ascending in vapour there is absolutely different from the fluid water it may be
different in some particulars, having reference to the amounts of power which it contains ; but it is the same,
nevertheless, as the great ocean of water around our globe, and I employ it here for the sake of illustration, because if
we look into it we shall find that it supplies us with examples of all the powers to which I shall have to refer. For
instance, here is water it is heavy; but let us examine it with regard to the amount of its heaviness, or its gravity.
Now, that power which caused the water to descend in the balance which made the iron weight press upon and flatten
the bubble of air which caused the swinging to and fro of the pendulum, that power is entirely due to the attraction
which there is between the falling body and the earth. Let us be slow and careful to comprehend this. It is not that the
earth has any particular attraction towards bodies which fall to it, but, that all these bodies possess an attraction, every
one towards the other. It is not that -the earth has any special power which these balls themselves have not, for just as
much power as the earth has to attract these two balls [dropping two ivory balls], just so much power have they in
proportion to their bulks to draw themselves one to the other ; and the only reason why they fall so quickly to the earth
is owing to its greater size.
Now, it is not very easy to make these things quite clear at the outset, and I must take care not to leave anything
unexplained as I proceed, and, therefore, I must make' you clearly understand that all bodies are attracted to the earth,
or, to use a more learned term, gravitate. You will not mind my using this word, for when I say that this penny-piece
gravitates, I mean nothing more nor less than that it falls towards the earth, and if not intercepted, it would go on falling,
falling, until it arrived at what we call the centre of gravity of the earth, which I will explain to you by and by. I want
you to understand that this property of gravitation is never lost, that every substance possesses it, that there is never any
change in the quantity of it.
There is another point I want in the next place to draw your attention to. I have here a quantity of shot; each of these
falls separately, and each has its own gravitating power, as you perceive when I let them fall loosely on a sheet of paper.
If I put them into a bottle I collect them together as one mass, and philosophers have discovered that there is a certain
point in the middle of the whole collection of shots that may he considered as the one point in which all their gravitating
power is centred, and that point they call the centre of gravity; it is not at all a bad name, and rather a short one the
centre of gravity.
As we proceed, I intend to write upon the board behind me certain words so as to recall to your minds what we have
already examined ; and I put the word FORCES as a heading, and I will then add beneath the names of the special
forces according to the order in which we consider them ; and although I fear that I have not sufficiently pointed out to
you the more important circumstances connected with this force of GRAVITATION, especially the law which governs
its attraction (for which, I think, I must take up a little time at our next meeting), still I will put that word on the board,
and hope you will now remember that we have in some degree considered the force of gravitation that force which
causes all bodies to attract each other when they are at sensible distances apart, and tends to draw them together.
LII
Do me the favour to pay me as much attention as you did at our last meeting, and I shall not repent of that which I have
proposed to undertake. It will be impossible for us to consider the Laws of Nature, and what they effect, unless we now
and then give our sole attention, so as to obtain a clear idea upon the subject. Give me now that attention, and then I
trust we shall not part without your knowing something about those Laws, and the manner in which they act. You
recollect, upon the last occasion, I explained that all bodies attracted each other, and that this power we called
gravitation. I told you that when we brought these two bodies [two equal-sized ivory balls suspended by threads] near
together, they attracted each other, and that we might suppose that the whole power of this attraction was exerted
between their respective centres of gravity ; and, furthermore, you learned from me that if, instead of a small ball I took
a larger one, like that [changing one of the balls for a much larger one], there was much more of this attraction exerted ;
or, if I made this ball larger and larger, until, if it were possible, it became as large as the Earth itself or, I might take the
Earth itself, as the large ball that then the attraction would become so powerful as to cause them to rush together in this
manner [dropping the ivory ball]. You sit there upright, and I stand upright here, because we keep our centres of gravity
properly balanced with respect to the earth ; and I need not tell you that on the other side of this world the people are
standing and moving about with their feet towards our feet, in a reversed position as compared with us, and all by
means of this power of gravitation to the centre of the earth.
I must not, however, leave the subject of gravitation, without telling you something about its laws and regularity; and
first, as regards its power with respect to the distance that bodies are apart. If I take one of these balls and place it within
an inch of the other, they attract each other with a certain power. If I hold it at a greater distance off, they attract with
less power, and if I hold it at a greater distance still, their attraction is still less. Now this fact is of the greatest
consequence ; for, knowing this law, philosophers have discovered most wonderful things. You know that there is a
planet, Uranus, revolving round the sun with us, but eighteen hundred millions of miles off; and because there is
another planet as far off as three thousand millions of miles, this law of attraction, or gravitation, still holds good, and
philosophers actually discovered this latter planet, Neptune, by reason of the effects of its attraction at this
overwhelming distance. Now I want you clearly to understand what this law is. They say (and they are right) that two
bodies attract each other inversely as the square of the distance, a sad jumble of words until you understand them ; but I
think we shall soon comprehend what this law is, and what is the meaning of the " inverse square of the distance."
Now, if you cannot perfectly recollect this when you go home, get a candle and throw a shadow of something your
profile, if you like on the wall, and then recede or advance, and you will find that your shadow is exactly in proportion
to the square of the distance you are off the wall ; and then if you consider how much light shines on you at one
distance, and how much at another, you get the inverse accordingly. So it is as regards the attraction of these two balls,
they attract according to the square of the distance, inversely. I want you to try and remember these words, and then you
will be able to go into all the calculations of astronomers as to the planets and other bodies, and tell why they move so
fast, and why they go round the sun without falling into it, and be prepared to enter upon many other interesting
inquiries of the like nature.
Let us now leave this subject which I have written upon the board under the word FORCE GRAVITATION and go a
step further. Allbodies attract each other at sensible distances. I showed you the electric attraction on the last
occasion (though I did not call it so); that attracts at a distance; and in order to make our progress a little more gradual,
suppose I take a few iron particles [dropping some small fragments of iron on the table]. There, I have already told you
that in all cases where bodies fall, it is the particles that are attracted. You may consider these then as separate particles
magnified, so as to be evident to your sight ; they are loose from eachother they all gravitate they all fall to the earth for
the force of gravitation never fails. Now, I have here a centre of power which I will not name at present, and when these
particles are placed upon it, see what an attraction they have for each other.
How can we make this attraction of the particles a little more simple ? There are many things which if brought together
properly will show this attraction. Here is a boy's experiment (and I like a boy's experiment). Get a tobacco-pipe, fill it
with lead, melt it, and then pour it out upon a stone, and thus get a clean piece of lead (this is a better plan than scraping
it scraping alters the condition of the surface of the lead). I have here some pieces of lead which I melted this morning
for the sake of making them clean. Now these pieces of lead hang together by the attraction of their particles, and if I
press these two separate pieces close together, so as to bring their particles within the sphere of attraction, you will see
how soon they become one. I have merely to give them a good squeeze, and draw the upper piece slightly round at the
same time, and here they are as one, and all the bending and twisting I can give them will not separate them again ; I
have joined the lead together, not with solder, but simply by means of the attraction of the particles.
This however is not the best way of bringing those particles together we have many better plans than that, and I will
show you one that will do very well for juvenile experiments. There is some alum crystallised very beautifully by nature
(for all things are far more beautiful in their natural than their artificial form), and here I have some of the same alum
broken into fine powder. In it I have destroyed that force of which I have placed the name on this board COHESION, or
the attraction exerted between the particles of bodies to hold them together.
Now how curiously our ideas expand by watching these conditions of the attraction of cohesion ! -how many new
phenomena it gives us beyond those of the attraction of gravitation ! See how it gives us great strength. The things we
deal with in building up the structures on the earth are of strength we use iron, stone, and other things of great strength ;
and only think that all those structures you have about you think of the Great Eastern if you please, which is of such size
and power as to be almost more than man can manage are the result of this power of cohesion and attraction.
Now, I have shown you these things for the purpose of bringing your minds to see that bodies are not merely held
together by this power of cohesion, but that they are held together in very curious ways. And suppose I take some things
that are held together by this force, and examine them more minutely.
Now I want you to understand a little more how this is and for this purpose I am going to use the electric light again.
Light is a thing which is, so to say, attracted by every substance that gravitates (and we do not know anything that does
not). All matter affects light more or less by what we may consider as a kind of attraction.
Here I have the rays once more bent on to the screen, and you see how wonderfully and beautifully that piece of glass
not only bends the light by virtue of its attraction, but actually splits it up into different colours. Now, I want you to
understand that this piece of glass [the prism] being perfectly uniform in its internal structure, tells us about the action
of these other bodies which are not uniform which do not merely cohere, but also have within them, in different parts,
different degrees of cohesion, and thus attract and bend the light with varying powers.
Ah ! these points show the position of the strain in these parts the force of cohesion is being exerted in a different
degree to what it is in the other parts, and hence it allows the light to pass through. How beautiful that is howit makes
the light come through some parts and leaves it dark in others, and all because we weaken the force of cohesion
between particle and particle. Whether you have this mechanical power of straining, or whether we take other means,
we get the same result, and, indeed, I will show you by another experiment that if we heat the glass in one part it will
alter its internal structure, and produce a similar effect. Now you see how beautifully the light goes through those parts
which are hot, making dark and light lines just as the crystal did, and all because of the alteration I have effected in its
internal condition; for these dark and light parts are a proof of the presence of forces acting and dragging in different
directions within the solid mass.
LIII
We have already gained a knowledge of the manner in which the particles of bodies of solid bodies attract each other,
and we have learnt that it makes calcareous spar, alum, and so forth, crystallise in these regular forms. Now let me
gradually lead your minds to a knowledge of the means we possess of making this attraction alter a little in its force ;
either of increasing, or diminishing, or apparently of destroying it altogether.
Here is the water which we have produced by destroying some of the attraction which existed between the particles of
the ice, for below a certain temperature the particles of water increase in their mutual attraction and become ice; and
above a certain temperature the attraction decreases and the water becomes steam. And exactly the same thing happens
with platinum, and nearly every substance in nature; if the temperature is increased to a certain point it becomes liquid,
and a further increase converts it into a gas. Is it not a glorious thing for us to look at the sea, the rivers, and so forth,
and to know that this same body in the northern regions is all solid ice and icebergs, while here, in a warmer climate, it
has its attraction of cohesion so much diminished as to be liquid water. Well, in diminishing this force of attraction
between the particles of ice, we made use of another force, namely, that of heat; and I want you now to understand that
this force of heat is always concerned when water passes from the solid to the liquid state.
Now we have discovered a means, by great care and research into the properties of various bodies, of preparing a
solution of a salt which if shaken or disturbed will at once become a solid; and as I explained to you just now (for what
is true of water is true of every other liquid), by reason of its becoming solid, heat is evolved and so we learn this
beautiful law of our philosophy, that whenever we diminish the attraction of cohesion we absorb heat and whenever we
increase that attraction heat is evolved. This, then, is a great step in advance, for you have learned a great deal in
addition to the mere circumstance that particles attract each other. But you must not now suppose that because they are
liquid they have lost their attraction of cohesion.
I am now going to lead you a step beyond this consideration of the attraction of the particles for each other. You see we
have come to understand that, if we take water as an illustration, whether it be ice, or water, or steam, it is always to be
considered by us as water. Well, now prepare your minds to go a little deeper into the subject. We have means of
searching into the constitution of water beyond any that are afforded us by the action of heat, and among these one of
the most important is that force which we call voltaic electricity.
Here, then, we have two things, neither of them being water alone, but which we get out of the water. Water is therefore
composed of two substances different to itself, which appear at separate places when it is made to submit to the force
which I have in these wires, and if I take an inverted tube of water and collect this gas (H), you will see that it is by no
means the same as the one we collected in the former apparatus (fig. 24). That exploded with a loud noise when it was
lighted, but this will burn quite noiselessly it is called hydrogen; and the other we call oxygen that gas which so
beautifully brightens up all combustion, but does not burn of itself. So now we see that water consists of two kinds of
particles attracting each other in a very different manner to the attraction of gravitation or cohesion, and this new
attraction we call chemical affinity, or the force of chemical action between different bodies ; we are now no longer
concerned with the attraction of iron for iron, water for water, wood for wood, or like bodies for each other as we were
when dealing with the force of cohesion ; we are dealing with another kind of attraction, the attraction between particles
of a different nature one to the other. Chemical affinity depends entirely upon the energy with which particles of
different kinds attract each other. Oxygen and hydrogen are particles of different kinds, and it is their attraction to each
other which makes them chemically combine and produce water.
Now when water is opened out in this way by means of the battery ; which adds nothing to it materially, which takes
nothing from it materially (I mean no matter, I am not speaking of force) ; which adds no matter to the water ; it is
changed in this way the gas which you saw burning a little while ago, called hydrogen, is evolved in large quantity, and
the other gas, oxygen, is evolved in only half the quantity; so that these two areas represent water, and these are always
the proportions between the two gases.
LIV
WE shall have to pay a little more attention to the forces existing in water before we can have a clear idea on the
subject. Besides the attraction which there is between its particles to make it hold together as a liquid or a solid, there is
also another force, different from the former ; one which, yesterday, by means of the voltaic battery, we overcame,
drawing from the water two different substances, which, when heated by means of the electric spark, attracted each
other, and rushed into combination to reproduce water. Now I propose to-day to continue this subject, and trace the
various phenomena of chemical affinity.
You now understand that we can have particles of very different kinds, and that they can have different bulks and
weights ; and there are two or three very interesting experiments which serve to illustrate this.
And now, having brought you in the first place to the consideration of chemical attraction, I must enlarge your ideas so
as to include all substances which have this attraction for each other for it changes the character of bodies^ and alters
them in this way and that way, in the most extraordinary manner; and produces other phenomena wonderful to think
about.
There you see the result of the action of chemical affinity, overcoming the attraction of cohesion of the particles.
Observe this chemical affinity travelling about the mass, and setting it on fire, and throwing it into such wonderful
agitation!
I must now come to a few circumstances which require careful consideration. We have already examined one of the
effects of this chemical affinity but to make the matter more clear we must point out some others.
We have endless varieties of rapidity in chemical action. And here are two salts dissolved in water. As I mix them they
get thicker and thicker, and you see the liquid is hardening and stiffening, and before long I shall have it quite hard ; and
before' the end of the lecture it will be a solid stone a wet stone no doubt, but more or less solid in consequence of the
chemical affinity. Is not this changing two liquids into a solid body a wonderful manifestation of chemical affinity ?
There is another remarkable circumstance in chemical affinity, which is that it is capable of either waiting or acting at
once. And this is very singular, because we know of nothing of the kind in the forces either of gravitation or cohesion.
The substances wait until we do something which is able to start the action. Can anything be more beautiful than this
combustion of charcoal in oxygen ? You must understand that each of these little sparks is a portion of the charcoal, or
the bark of the charcoal, thrown off white hot into the oxygen, and burning in it most brilliantly, as you see. And now
let me tell you another thing, or you will go away with a very imperfect notion of the powers and effects of this affinity.
These are the lumps of lead which you remember we had the other day the two pieces which clung together. Now these
pieces, if I take them to day and press them together, will not stick, and the reason is that they have attracted from the
atmosphere a part of the oxygen there present, and have become coated as with a varnish by the oxide of lead, which is
formed on the surface, by a real process of combustion or combination.
Now that is nothing more than the common affinity always existing between very clean lead and the atmospheric
oxygen ; and the reason why this iron does not burn until it is made red hot, is because it has got a coating of oxide
about it, which stops the action of the oxygen, putting a varnish, as it were, upon its surface, as we varnish a picture
absolutely forming a substance which prevents the natural chemical affinity between the bodies from acting. I must now
take you a little further in this kind of illustration, or consideration, I would rather call it, of chemical affinity. This
attraction between different particles exists also most curiously in cases where they are previously combined with other
substances.
This affinity can thus act across substances, and I want you to see how curiously what we call combustion acts with
respect to this force of chemical affinity. (combustion being in all cases the result of chemical affinity).
It is by this kind of attraction of the different particles one to the other that we are enabled to trace the laws of chemical
affinity, and the wonderful variety of the exertions of these laws.
Now I want you to observe that one great exertion of this power which is known as chemical affinity is to produce
HEAT and light; you know, as a matter of fact, no doubt, that when bodies burn they give out heat, but it is a curious
thing that this heat does not continue the heat goes away as soon as the action stops, and you see thereby that it depends
upon the action during the time it is going on. It is not so with gravitation; this force is continuous, and is just as
effective in making that lead press on the table as it was when it first fell there. Nothing occurs there which disappears
when the action of falling is over; the pressure is upon the table, and will remain there until the lead is removed ;
whereas, in the action of chemical affinity to give light and heat, they go away immediately the action is over. This
lamp seems to evolve heat and light continuously, but it is owing to a constant stream of air coming into it on all sides,
and this work of producing light and heat by chemical affinity will subside as soon as the stream of air is interrupted.
What then is this curious condition of heat ? Why it is the evolution of another power of matter, of a power new to us,
and which we must consider as if it were now for the very first time brought under our notice. What is heat ? We
recognise heat by its power of liquefying solid bodies and vaporising liquid bodies, by its power of setting in action, and
very often overcoming, chemical affinity. Then how do we obtain heat? We obtain it in various ways ; most abundantly
by means of the chemical affinity we have just before been speaking about, but we can also obtain it in many other
ways. Friction will produce heat.
I am now going to show you that we can obtain heat not by chemical affinity alone, but by the pressure of air. It wants a
suddenness of pressure, or we shall not do what we require.
And now for the effects of this power. We need not consider many of them on the present occasion, because when you
have seen its power of changing ice into water and water into steam, you have seen the two principal results of the
application of heat. I want you now to see how it expands all bodies all bodies but one, and that under limited
circumstances.we have a perfect proof of this power of heat to contract and expand bodies.
LV
I wonder whether we shall be too deep to-day or not. Remember, that we spoke of the attraction by gravitation of all
bodies to all bodies by their simple approach. Remember, that we spoke of the attraction of particles of the same kind
to each other, that power which keeps them together in masses, iron attracted to iron, brass to brass, or water to water.
Remember, that we found, on looking into water, that there were particles of two different kinds attracted to each other ;
and this was a great step beyond the first simple attraction of gravitation ; because here we deal with attraction between
different kinds of matter. The hydrogen could attract the oxygen and reduce it to water, but it could not attract any of its
own particles, so that there we obtained a first indication of theexistence of two attractions.
To-day we come to a kind of attraction even more curious than the last, namely, the attraction which we find to be of a
double nature of a curious and dual nature. And I want first of all to make the nature of this doubleness clear to you.
Bodies are sometimes endowed with a wonderful attraction, which is not found in them in their ordinary state. For
instance, here is a piece of shellac, having the attraction of gravitation, having the attraction of cohesion, and if I set fire
to it, it would have the attraction of chemical affinity to the oxygen in the atmosphere. Now all these powers we find in
it as if they were parts of its substance ; but there is another property.
Remember that whenever we get an attraction of gravity, chemical affinity, adhesion, or electricity (as in this case), the
body which attracts is attracted also, and just as much as that ball was attracted by the shellac, the shellac was attracted
by the ball.
You see, therefore, what a difference there is between these two attractions, they are actually two kinds of attraction
concerned in this case, quite different to anything we have met with before ; but the force is the same. We have here
then a double attraction a dual attraction or force one attracting and the other repelling.
Concerned in this case, quite different to anything we have met with before ; but the force is the same. We have here
then a double attraction a dual attraction or force one attracting and the other repelling. You see clearly there are two
kinds of electricities which may be obtained by rubbing shellac with flannel or glass with silk.
Now, there are some curious bodies in nature (of which I have two specimens on the table) which are called magnets or
loadstones; ores of iron, of which there is a great deal sent from Sweden. They have the attraction of gravitation, and
attraction of cohesion, and certain chemical attraction ; but they also have a great attractive power, for this little key is
held up by this stone. Now, that is not chemical attraction, it is not the attraction of chemical affinity, or of aggregation
of particles^ or of cohesion, or of electricity (for it will not attract this ball if I bring it near it), but it is a separate and
dual attraction, and what is more, one which is not readily removed from the substance, for it has existed in it for ages
and ages in the bowels of the earth. Now we can make artificial magnets (you will see me to-morrow make artificial
magnets of extraordinary power). And let us take one of these artificial magnets, and examine it, and see where the
power is in the mass, and whether it is a dual power. It is not then the whole of the substance which attracts. Is it not
then very curious to find that there is an attractive power at the extremities which is not in the middle ! to have thus in
one bar two places in which this force of attraction resides.
We are now therefore dealing with two kinds of power, attracting different ends of the magnet a double power, already
existing in these bodies, which takes up the form of attraction and repulsion. And now when I put up this label with the
word MAGNETISM, you will understand that it is to express this double power.
I want you now to observe that although I have shown you in these magnets that this double power becomes evident
principally at the extremities, yet the whole of the magnet is concerned in giving the power. That will at first seem
rather strange, but the whole of the mass is really concerned in this force, just as in falling the whole of the mass is
acted upon by the force of gravitation.
Now, is not this power a most wonderful thing? And very strange, the means of taking it from one substance and
bringing it to other matters. I cannot make a piece of iron or anything else heavier or lighter than it is ; its cohesive
power it must and does have ; but, as you have seen by these experiments, we can add or subtract this power of
magnetism, and almost do as we like with it.
If I hold this cylinder of brass by the glass handle and touch the conductor with it I take away a little of the electricity.
You see the spark in which it passes, and observe that the pith-ball indicator has fallen a little, which seems to imply
that so much electricity is lost; but it is not lost, it is here in this brass, and I can take it away and carry it about, not
because it has any substance of its own, but by some strange property which we have not before met with as belonging
to any other force.
You see from the spark that I can transfer the power from the machine to this cylinder, and then carry it away and give
it to some other body. You know very well as a matter of experiment that we can transfer the power of heat from one
thing to another. So you see that some powers are transferable and others are not.
I must now take up a little of your time in showing you the manner in which these powers are transferred from one thing
to another ; for the manner in which force may be conducted or transmitted is extraordinary, and most essential for us to
understand. Let us see in what manner these powers travel from place to place. Both heat and electricity can be
conducted you will learn that the heat travels gradually through the copper. You will see that this is a very slow
conduction of power as compared with electricity. But with regard to the travelling of electricity from place to place its
rapidity is astonishing. And so you perceive how easily I can manage to send this power of electricity from place to
place by choosing the materials which can conduct the power.
You now see how it is that this power of electricity can be transferred from the matter in which it is generated, and
conducted along wires and other bodies, and thus be made to serve new purposes utterly unattainable by the powers we
have spoken of on previous days ; and you will not now be at a loss to bring this power of electricity into comparison
with those which we have previously examined, and to-morrow we shall be able to go further into the consideration of
these transferable powers.
LVI
WE have frequently seen, during the course of these lectures, that one of those powers or forces of matter, of which I
have written the names on that board, has produced results which are due to the action of some other force. Thus, you
have seen the force of electricity acting in other ways than in attracting; you have also seen it combine matters together
or disunite them by means of its action on the chemical force ; and in this case, therefore, you have an instance in which
these two powers are related. But we have other and deeper relations than these ; we have not merely to see how it is
that one power affects another how the force of heat affects chemical affinity, and so forth, but we must try and
comprehend what relation they bear to each other, and how these powers may be changed one into the other ; and it will
to-day require all my care, and your care too, to make this clear to your minds. I shall be obliged to confine myself to
one or two instances, because to take in the whole extent of this mutual relation and conversion of forces would surpass
the human intellect.
These are all cases of chemical affinity, and I show them to make you understand that we are about to enter upon the
consideration of a strange kind of chemical affinity, and then to see how far we are enabled to convert this force of
affinity into electricity or magnetism, or any other of the forces which we have discussed.
I havehere an apparatus (fig. 46) which Sir Humphry Davy constructed many years ago, in order to see whether this
power from the voltaic battery caused bodies to attract each other in the same manner as the ordinary electricity did. He
made it in order to experiment with his large voltaic battery, which was the most powerful then in existence. Now they
are attracting each other, long before the connection is complete, and there they go ! burnt up in that brilliant flash, so
strong is the force. You thus see, from the attractive force at the two ends of this battery, that these are really and truly
electrical phenomena. Now, let us consider what is this spark. I take these two ends and bring them together, and there I
get this glorious spark like the sunlight in the heavens above us. What is this ? It is the same thing which you saw when
I discharged the large electrical machine, when you saw one single bright flash ; it is the same thing, only continued,
because here we have a more effective arrangement. Instead of having a machine which we are obliged to turn for a
long time together, we have here a chemical power which sends forth the spark and it is wonderful and beautiful to see
how this spark is carried about through these wires. I want you to perceive, if possible, that this very spark and the heat
it produces (for there is heat), is neither more nor less than the chemical force of the zinc its very force carried along
wires and conveyed to this place.
That shows you what the affinity is when we come to consider it in its energy and power. And the zinc is being burned
in the battery behind me at a much more rapid rate than you see in that jar, because the zinc is there dissolving and
burning, and produces here this great electric light.That very same power which in that jar you saw evolved from the
actual combustion of the zinc in oxygen, is carried along these wires and made evident here, and you may if you please
consider that the zinc is burning in those cells, and that this is the light of that burning [bringing the two poles in contact
and showing the electric light] ; and we might so arrange our apparatus as to show that the amounts of power evolved in
either case are identical. Having thus obtained power over the chemical force, how wonderfully we are able to convey it
from place to place !
Now I want to show you that this power is still chemical affinity that if we call the power which is evolved at this point
heat, or electricity, or any other name referring to its source, or the way in which it travels, we still shall find it to be
chemical action.
I have here given you all the illustrations that time will permit me to show you of chemical affinity producing
electricity, and electricity again becoming chemical affinity. Let that suffice for the present ; and let us now go a little
deeper into the subject of this chemical force, or this electricity which shall I name first the one producing the other in a
variety of ways. These forces are also wonderful in their power of producing another of the forces we have been
considering, namely, that of magnetism, and you know that it is only of late years, and long since I was born, that the
discovery of the relations of these two forces of electricity and chemical affinity to produce magnetism have become
known. Philosophers had been suspecting this affinity for a long time, and had long had great hopes of success for in the
pursuit of science we first start with hopes and expectations; these we realise and establish never again to be lost, and
upon them we found new expectations of further discoveries, and so go on pursuing, realising, establishing, and
founding new hopes again and again.
Now observe this: here is a piece of wire which I am about to make into a bridge of force, that is to say, a communicator
between the two ends of the battery. It is copper wire only, and is therefore not magnetic of itself. We will examine this
wire with our magnetic needle (Jig. 51), and though connected with one extreme end of the battery, you see that before
the circuit is completed it has no power over the magnet. But observe it when I make contact ; watch the needle, see
how it is swung round, and notice how indifferent it becomes if I break contact again ; so you see we have this wire
evidently affecting the magnetic needle under these circumstances. Let me show you that a little more strongly. I have
here a quantity of wire which has been wound into a spiral, and this will affect the magnetic needle in a very curious
manner, because, owing to its shape, it will act very like a real magnet. The copper spiral has no power over that
magnetic needle at present ; but if I cause the electric current to circulate through it, by bringing the two ends of the
battery in contact with the ends of the wire which forms the spiral, what will happen ? Why one end of the needle is
most powerfully drawn to it ; and if I take the other end of the needle it is repelled ; so yoii see I have produced exactly
the same phenomena as I had with the bar magnet, one end attracting and the other repelling. Is not this then curious to
see that we can construct a magnet of copper? Further- more, if I take an iron bar, and put it inside the coil, so long as
there is no electric current circulating round, it has no attraction, as you will observe if I bring a little iron filings or
nails near the iron. But now if I make contact with the battery they are attracted at once. It becomes at once a powerful
magnet, so much so that I should not wonder if these magnetic needles on different parts of the table pointed to it. And I
will show you by another experiment what an attraction it has. This piece and that piece of iron and many other pieces
are now strongly attracted (fig. 52), but as soon as I break contact the power is all gone and they fall. What then can be
a better or a stronger proof than this of the relation of the powers of magnetism and electricity ? Again, here is a little
piece of iron which is not yet magnetised. It will not at present take up any one of these nails ; but I will take a piece of
wire and coil it round the iron (the wire being covered with cotton in every part it does not touch the iron), so that the
current must go round in this spiral coil I am, in fact, preparing an electro-magnet (we are obliged to use such terms to
express our meaning, because it is a magnet made by electricity, because we produce by the force of electricity a
magnet of far greater power than a permanent steel one). It is now completed and I will repeat the experiment which
you saw the other day, of building up a bridge of iron nails ; the contact is now made and the current is going through ;
it is now a powerful magnet ; here are the iron nails which we had the other day, and now I have brought this magnet
nearthem they are clinging so hard that I can scarcely move them with my hand (Jig. 53). But when the contact is
broken, see how they fall. What can show you better than such an experiment as this the magnetic attraction with which
we have endowed these portions of iron ?
I might give you an infinity of illustrations of this high magnetic power. There is that long bar of iron held out, and I
have no doubt that if I were to examine the other end I should find that it was a magnet. See what power it must have to
support not only these nails, but all those lumps of iron hanging on to the end. What then can surpass these evidences
of the change of chemical force into electricity, and electricity into magnetism ? I might show you many other
experiments whereby I could obtain electricity and chemical action, heat and light from a magnet, but what more need I
show you to prove the universal correlation of the physical forces of matter, and their mutual conversion one into
another ? And now let us give place as juveniles to the respect we owe to our elders ; and for a time let me address
myself to those of our seniors who have honoured me with their presence during these lectures. I wish to claim this
moment for the purpose of tendering our thanks to them, and my thanks to you all for the way in which you have borne
the inconvenience tjiat I at first subjected you to. I hope that the insight which you have here gained into some of the
laws by which the universe is governed, may be the occasion of some amongst you turning your attention to these
subjects; for what study is there more fitted to the mind of man than that of the physical sciences? And what is there
more capable of giving him an insight into the actions of those laws, a knowledge of which gives interest to the most
trifling phenomenon of nature, and makes the observing student find
"
tongues in trees, books in the running brooks,
Sermons in stones, and good in everything
"