Books: Five of Maxwell\'s Papers
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James Clerk Maxwell >> Five of Maxwell\'s Papers
When we shall be able to employ in scientific education, not only the
trained attention of the student, and his familiarity with symbols,
but the keenness of his eye, the quickness of his ear, the delicacy of
his touch, and the adroitness of his fingers, we shall not only extend
our influence over a class of men who are not fond of cold
abstractions, but, by opening at once all the gateways of knowledge,
we shall ensure the association of the doctrines of science with those
elementary sensations which form the obscure background of all our
conscious thoughts, and which lend a vividness and relief to ideas,
which, when presented as mere abstract terms, are apt to fade entirely
from the memory.
In a course of Experimental Physics we may consider either the Physics
or the Experiments as the leading feature. We may either employ the
experiments to illustrate the phenomena of a particular branch of
Physics, or we may make some physical research in order to exemplify a
particular experimental method. In the order of time, we should
begin, in the Lecture Room, with a course of lectures on some branch
of Physics aided by experiments of illustration, and conclude, in the
Laboratory, with a course of experiments of research.
Let me say a few words on these two classes of
experiments,--Experiments of Illustration and Experiments of Research.
The aim of an experiment of illustration is to throw light upon some
scientific idea so that the student may be enabled to grasp it. The
circumstances of the experiment are so arranged that the phenomenon
which we wish to observe or to exhibit is brought into prominence,
instead of being obscured and entangled among other phenomena, as it
is when it occurs in the ordinary course of nature. To exhibit
illustrative experiments, to encourage others to make them, and to
cultivate in every way the ideas on which they throw light, forms an
important part of our duty. The simpler the materials of an
illustrative experiment, and the more familiar they are to the
student, the more thoroughly is he likely to acquire the idea which it
is meant to illustrate. The educational value of such experiments is
often inversely proportional to the complexity of the apparatus. The
student who uses home-made apparatus, which is always going wrong,
often learns more than one who has the use of carefully adjusted
instruments, to which he is apt to trust, and which he dares not take
to pieces.
It is very necessary that those who are trying to learn from books the
facts of physical science should be enabled by the help of a few
illustrative experiments to recognise these facts when they meet with
them out of doors. Science appears to us with a very different aspect
after we have found out that it is not in lecture rooms only, and by
means of the electric light projected on a screen, that we may witness
physical phenomena, but that we may find illustrations of the highest
doctrines of science in games and gymnastics, in travelling by land
and by water, in storms of the air and of the sea, and wherever there
is matter in motion.
This habit of recognising principles amid the endless variety of their
action can never degrade our sense of the sublimity of nature, or mar
our enjoyment of its beauty. On the contrary, it tends to rescue our
scientific ideas from that vague condition in which we too often leave
them, buried among the other products of a lazy credulity, and to
raise them into their proper position among the doctrines in which our
faith is so assured, that we are ready at all times to act on them.
Experiments of illustration may be of very different kinds. Some may
be adaptations of the commonest operations of ordinary life, others
may be carefully arranged exhibitions of some phenomenon which occurs
only under peculiar conditions. They all, however, agree in this,
that their aim is to present some phenomenon to the senses of the
student in such a way that he may associate with it the appropriate
scientific idea. When he has grasped this idea, the experiment which
illustrates it has served its purpose.
In an experiment of research, on the other hand, this is not the
principal aim. It is true that an experiment, in which the principal
aim is to see what happens under certain conditions, may be regarded
as an experiment of research by those who are not yet familiar with
the result, but in experimental researches, strictly so called, the
ultimate object is to measure something which we have already seen--to
obtain a numerical estimate of some magnitude.
Experiments of this class--those in which measurement of some kind is
involved, are the proper work of a Physical Laboratory. In every
experiment we have first to make our senses familiar with the
phenomenon, but we must not stop here, we must find out which of its
features are capable of measurement, and what measurements are
required in order to make a complete specification of the phenomenon.
We must then make these measurements, and deduce from them the result
which we require to find.
This characteristic of modern experiments--that they consist
principally of measurements,--is so prominent, that the opinion seems
to have got abroad, that in a few years all the great physical
constants will have been approximately estimated, and that the only
occupation which will then be left to men of science will be to carry
on these measurements to another place of decimals.
If this is really the state of things to which we are approaching, our
Laboratory may perhaps become celebrated as a place of conscientious
labour and consummate skill, but it will be out of place in the
University, and ought rather to be classed with the other great
workshops of our country, where equal ability is directed to more
useful ends.
But we have no right to think thus of the unsearchable riches of
creation, or of the untried fertility of those fresh minds into which
these riches will continue to be poured. It may possibly be true
that, in some of those fields of discovery which lie open to such
rough observations as can be made without artificial methods, the
great explorers of former times have appropriated most of what is
valuable, and that the gleanings which remain are sought after, rather
for their abstruseness, than for their intrinsic worth. But the
history of science shews that even during that phase of her progress
in which she devotes herself to improving the accuracy of the
numerical measurement of quantities with which she has long been
familiar, she is preparing the materials for the subjugation of new
regions, which would have remained unknown if she had been contented
with the rough methods of her early pioneers. I might bring forward
instances gathered from every branch of science, shewing how the
labour of careful measurement has been rewarded by the discovery of
new fields of research, and by the development of new scientific
ideas. But the history of the science of terrestrial magnetism
affords us a sufficient example of what may be done by Experiments in
Concert, such as we hope some day to perform in our Laboratory.
That celebrated traveller, Humboldt, was profoundly impressed with the
scientific value of a combined effort to be made by the observers of
all nations, to obtain accurate measurements of the magnetism of the
earth; and we owe it mainly to his enthusiasm for science, his great
reputation and his wide-spread influence, that not only private men of
science, but the governments of most of the civilised nations, our own
among the number, were induced to take part in the enterprise. But
the actual working out of the scheme, and the arrangements by which
the labours of the observers were so directed as to obtain the best
results, we owe to the great mathematician Gauss, working along with
Weber, the future founder of the science of electro-magnetic
measurement, in the magnetic observatory of Gottingen, and aided by
the skill of the instrument-maker Leyser. These men, however, did not
work alone. Numbers of scientific men joined the Magnetic Union,
learned the use of the new instruments and the new methods of reducing
the observations; and in every city of Europe you might see them, at
certain stated times, sitting, each in his cold wooden shed, with his
eye fixed at the telescope, his ear attentive to the clock, and his
pencil recording in his note-book the instantaneous position of the
suspended magnet.
Bacon's conception of "Experiments in concert" was thus realised, the
scattered forces of science were converted into a regular army, and
emulation and jealousy became out of place, for the results obtained
by any one observer were of no value till they were combined with
those of the others.
The increase in the accuracy and completeness of magnetic observations
which was obtained by the new method, opened up fields of research
which were hardly suspected to exist by those whose observations of
the magnetic needle had been conducted in a more primitive manner. We
must reserve for its proper place in our course any detailed
description of the disturbances to which the magnetism of our planet
is found to be subject. Some of these disturbances are periodic,
following the regular courses of the sun and moon. Others are sudden,
and are called magnetic storms, but, like the storms of the
atmosphere, they have their known seasons of frequency. The last and
the most mysterious of these magnetic changes is that secular
variation by which the whole character of the earth, as a great
magnet, is being slowly modified, while the magnetic poles creep on,
from century to century, along their winding track in the polar
regions.
We have thus learned that the interior of the earth is subject to the
influences of the heavenly bodies, but that besides this there is a
constantly progressive change going on, the cause of which is entirely
unknown. In each of the magnetic observatories throughout the world
an arrangement is at work, by means of which a suspended magnet
directs a ray of light on a preparred sheet of paper moved by
clockwork. On that paper the never-resting heart of the earth is now
tracing, in telegraphic symbols which will one day be interpreted, a
record of its pulsations and its flutterings, as well as of that slow
but mighty working which warns us that we must not suppose that the
inner history of our planet is ended.
But this great experimental research on Terrestrial Magnetism produced
lasting effects on the progress of science in general. I need only
mention one or two instances. The new methods of measuring forces
were successfully applied by Weber to the numerical determination of
all the phenomena of electricity, and very soon afterwards the
electric telegraph, by conferring a commercial value on exact
numerical measurements, contributed largely to the advancement, as
well as to the diffusion of scientific knowledge.
But it is not in these more modern branches of science alone that this
influence is felt. It is to Gauss, to the Magnetic Union, and to
magnetic observers in general, that we owe our deliverance from that
absurd method of estimating forces by a variable standard which
prevailed so long even among men of science. It was Gauss who first
based the practical measurement of magnetic force (and therefore of
every other force) on those long established principles, which, though
they are embodied in every dynamical equation, have been so generally
set aside, that these very equations, though correctly given in our
Cambridge textbooks, are usually explained there by assuming, in
addition to the variable standard of force, a variable, and therefore
illegal, standard of mass.
Such, then, were some of the scientific results which followed in this
case from bringing together mathematical power, experimental sagacity,
and manipulative skill, to direct and assist the labours of a body of
zealous observers. If therefore we desire, for our own advantage and
for the honour of our University, that the Devonshire Laboratory
should be successful, we must endeavour to maintain it in living union
with the other organs and faculties of our learned body. We shall
therefore first consider the relation in which we stand to those
mathematical studies which have so long flourished among us, which
deal with our own subjects, and which differ from our experimental
studies only in the mode in which they are presented to the mind.
There is no more powerful method for introducing knowledge into the
mind than that of presenting it in as many different ways as we can.
When the ideas, after entering through different gateways, effect a
junction in the citadel of the mind, the position they occupy becomes
impregnable. Opticians tell us that the mental combination of the
views of an object which we obtain from stations no further apart than
our two eyes is sufficient to produce in our minds an impression of
the solidity of the object seen; and we find that this impression is
produced even when we are aware that we are really looking at two flat
pictures placed in a stereoscope. It is therefore natural to expect
that the knowledge of physical science obtained by the combined use of
mathematical analysis and experimental research will be of a more
solid, available, and enduring kind than that possessed by the mere
mathematician or the mere experimenter.
But what will be the effect on the University, if men Pursuing that
course of reading which has produced so many distinguished Wranglers,
turn aside to work experiments? Will not their attendance at the
Laboratory count not merely as time withdrawn from their more
legitimate studies, but as the introduction of a disturbing element,
tainting their mathematical conceptions with material imagery, and
sapping their faith in the formulae of the textbook? Besides this, we
have already heard complaints of the undue extension of our studies,
and of the strain put upon our questionists by the weight of learning
which they try to carry with them into the Senate-House. If we now
ask them to get up their subjects not only by books and writing, but
at the same time by observation and manipulation, will they not break
down altogether? The Physical Laboratory, we are told, may perhaps be
useful to those who are going out in Natural Science, and who do
not take in Mathematics, but to attempt to combine both kinds of study
during the time of residence at the University is more than one mind
can bear.
No doubt there is some reason for this feeling. Many of us have
already overcome the initial difficulties of mathematical training.
When we now go on with our study, we feel that it requires exertion
and involves fatigue, but we are confident that if we only work hard
our progress will be certain.
Some of us, on the other hand, may have had some experience of the
routine of experimental work. As soon as we can read scales, observe
times, focus telescopes, and so on, this kind of work ceases to
require any great mental effort. We may perhaps tire our eyes and
weary our backs, but we do not greatly fatigue our minds.
It is not till we attempt to bring the theoretical part of our
training into contact with the practical that we begin to experience
the full effect of what Faraday has called "mental inertia"--not only
the difficulty of recognising, among the concrete objects before us,
the abstract relation which we have learned from books, but the
distracting pain of wrenching the mind away from the symbols to the
objects, and from the objects back to the symbols. This however is
the price we have to pay for new ideas.
But when we have overcome these difficulties, and successfully bridged
over the gulph between the abstract and the concrete, it is not a mere
piece of knowledge that we have obtained: we have acquired the
rudiment of a permanent mental endowment. When, by a repetition of
efforts of this kind, we have more fully developed the scientific
faculty, the exercise of this faculty in detecting scientific
principles in nature, and in directing practice by theory, is no
longer irksome, but becomes an unfailing source of enjoyment, to which
we return so often, that at last even our careless thoughts begin to
run in a scientific channel.
I quite admit that our mental energy is limited in quantity, and I
know that many zealous students try to do more than is good for them.
But the question about the introduction of experimental study is not
entirely one of quantity. It is to a great extent a question of
distribution of energy. Some distributions of energy, we know, are
more useful than others, because they are more available for those
purposes which we desire to accomplish.
Now in the case of study, a great part of our fatigue often arises,
not from those mental efforts by which we obtain the mastery of the
subject, but from those which are spent in recalling our wandering
thoughts; and these efforts of attention would be much less fatiguing
if the disturbing force of mental distraction could be removed.
This is the reason why a man whose soul is in his work always makes
more progress than one whose aim is something not immediately
connected with his occupation. In the latter case the very motive of
which he makes use to stimulate his flagging powers becomes the means
of distracting his mind from the work before him.
There may be some mathematicians who pursue their studies entirely for
their own sake. Most men, however, think that the chief use of
mathematics is found in the interpretation of nature. Now a man who
studies a piece of mathematics in order to understand some natural
phenomenon which he has seen, or to calculate the best arrangement of
some experiment which he means to make, is likely to meet with far
less distraction of mind than if his sole aim had been to sharpen his
mind for the successful practice of the Law, or to obtain a high place
in the Mathematical Tripos.
I have known men, who when they were at school, never could see the
good of mathematics, but who, when in after life they made this
discovery, not only became eminent as scientific engineers, but made
considerable progress in the study of abstract mathematics. If our
experimental course should help any of you to see the good of
mathematics, it will relieve us of much anxiety, for it will not only
ensure the success of your future studies, but it will make it much
less likely that they will prove injurious to your health.
But why should we labour to prove the advantage of practical science
to the University? Let us rather speak of the help which the
University may give to science, when men well trained in mathematics
and enjoying the advantages of a well-appointed Laboratory, shall
unite their efforts to carry out some experimental research which no
solitary worker could attempt.
At first it is probable that our principal experimental work must be
the illustration of particular branches of science, but as we go on we
must add to this the study of scientific methods, the same method
being sometimes illustrated by its application to researches belonging
to different branches of science.
We might even imagine a course of experimental study the arrangement
of which should be founded on a classification of methods, and not on
that of the objects of investigation. A combination of the two plans
seems to me better than either, and while we take every opportunity of
studying methods, we shall take care not to dissociate the method from
the scientific research to which it is applied, and to which it owes
its value.
We shall therefore arrange our lectures according to the
classification of the principal natural phenomena, such as heat,
electricity, magnetism and so on.
In the laboratory, on the other hand, the place of the different
instruments will be determined by a classification according to
methods, such as weighing and measuring, observations of time, optical
and electrical methods of observation, and so on.
The determination of the experiments to be performed at a particular
time must often depend upon the means we have at command, and in the
case of the more elaborate experiments, this may imply a long time of
preparation, during which the instruments, the methods, and the
observers themselves, are being gradually fitted for their work. When
we have thus brought together the requisites, both material and
intellectual, for a particular experiment, it may sometimes be
desirable that before the instruments are dismounted and the observers
dispersed, we should make some other experiment, requiring the same
method, but dealing perhaps with an entirely different class of
physical phenomena.
Our principal work, however, in the Laboratory must be to acquaint
ourselves with all kinds of scientific methods, to compare them, and
to estimate their value. It will, I think, be a result worthy of our
University, and more likely to be accomplished here than in any
private laboratory, if, by the free and full discussion of the
relative value of different scientific procedures, we succeed in
forming a school of scientific criticism, and in assisting the
development of the doctrine of method.
But admitting that a practical acquaintance with the methods of
Physical Science is an essential part of a mathematical and scientific
education, we may be asked whether we are not attributing too much
importance to science altogether as part of a liberal education.
Fortunately, there is no question here whether the University should
continue to be a place of liberal education, or should devote itself
to preparing young men for particular professions. Hence though some
of us may, I hope, see reason to make the pursuit of science the main
business of our lives, it must be one of our most constant aims to
maintain a living connexion between our work and the other liberal
studies of Cambridge, whether literary, philological, historical or
philosophical.
There is a narrow professional spirit which may grow up among men of
science, just as it does among men who practise any other special
business. But surely a University is the very place where we should
be able to overcome this tendency of men to become, as it were,
granulated into small worlds, which are all the more worldly for their
very smallness. We lose the advantage of having men of varied
pursuits collected into one body, if we do not endeavour to imbibe
some of the spirit even of those whose special branch of learning is
different from our own.
It is not so long ago since any man who devoted himself to geometry,
or to any science requiring continued application, was looked upon as
necessarily a misanthrope, who must have abandoned all human
interests, and betaken himself to abstractions so far removed from the
world of life and action that he has become insensible alike to the
attractions of pleasure and to the claims of duty.
In the present day, men of science are not looked upon with the same
awe or with the same suspicion. They are supposed to be in league
with the material spirit of the age, and to form a kind of advanced
Radical party among men of learning.
We are not here to defend literary and historical studies. We admit
that the proper study of mankind is man. But is the student of
science to be withdrawn from the study of man, or cut off from every
noble feeling, so long as he lives in intellectual fellowship with men
who have devoted their lives to the discovery of truth, and the
results of whose enquiries have impressed themselves on the ordinary
speech and way of thinking of men who never heard their names? Or is
the student of history and of man to omit from his consideration the
history of the origin and diffusion of those ideas which have produced
so great a difference between one age of the world and another?
It is true that the history of science is very different from the
science of history. We are not studying or attempting to study the
working of those blind forces which, we are told, are operating on
crowds of obscure people, shaking principalities and powers, and
compelling reasonable men to bring events to pass in an order laid
down by philosophers.
The men whose names are found in the history of science are not mere
hypothetical constituents of a crowd, to be reasoned upon only in
masses. We recognise them as men like ourselves, and their actions
and thoughts, being more free from the influence of passion, and
recorded more accurately than those of other men, are all the better
materials for the study of the calmer parts of human nature.
But the history of science is not restricted to the enumeration of
successful investigations. It has to tell of unsuccessful inquiries,
and to explain why some of the ablest men have failed to find the key
of knowledge, and how the reputation of others has only given a firmer
footing to the errors into which they fell.
The history of the development, whether normal or abnormal, of ideas
is of all subjects that in which we, as thinking men, take the deepest
interest. But when the action of the mind passes out of the
intellectual stage, in which truth and error are the alternatives,
into the more violently emotional states of anger and passion, malice
and envy, fury and madness; the student of science, though he is
obliged to recognise the powerful influence which these wild forces
have exercised on mankind, is perhaps in some measure disqualified
from pursuing the study of this part of human nature.