James Prescott Joule was born at Salford, on Christmas Eve of the year
1818. His father and his grandfather before him were brewers, and the
business, in due course, descended to Mr. Joule and his elder brother,
and by them was carried on with success till it was sold, in 1854.
Mr. Joule's grandfather came from Elton, in Derbyshire, settled near
Manchester, where he founded the business, and died at the age of
fifty-four, in 1799. His father, one of a numerous family, married a
daughter of John Prescott of Wigan. They had five children, of
whom James Prescott Joule was the second, and of whom three were
sons--Benjamin, the eldest, James, and John--and two daughters--Alice
and Mary. Mr. Joule's mother died in 1836 at the age of forty-eight; and
his father, who was an invalid for many years before his death, died at
the age of seventy-four, in the year 1858.
Young Joule was a delicate child, and was not sent to school. His early
education was commenced by his mother's half sister, and was carried
on at his father's house, Broomhill, Pendlebury, by tutors till he was
about fifteen years of age. At fifteen he commenced working in the
brewery, which, as his father's health declined, fell entirely into the
hands of his brother Benjamin and himself.
Mr. Joule obtained his first instruction in physical science from
Dalton, to whom his father sent the two brothers to learn chemistry.
Dalton, one of the most distinguished chemists of any age or country,
was then President of the Manchester Literary and Philosophical Society,
and lived and received pupils in the rooms of the Society's house. Many
of his most important memoirs were communicated to the Society, whose
_Transactions_ are likewise enriched by a large number of communications
from his distinguished pupil. Dalton's instruction to the two young men
commenced with arithmetic, algebra, and geometry. He then taught them
natural philosophy out of Cavallo's text-book, and afterward, but only
for a short time before his health gave way, in 1837, chemistry from his
own "New System of Chemical Philosophy." "Profound, patient, intuitive,"
his teaching must have had great influence on his pupils. We find Mr.
Joule early at work on the molecular constitution of gases, following in
the footsteps of his illustrious master, whose own investigations on the
constitution of mixed gases, and on the behavior of vapors and gases
under heat, were among the most important of his day, and whose
brilliant discovery of the atomic theory revolutionized the science of
chemistry and placed him at the head of the philosophical chemists of
Europe.
[Illustration: JAMES PRESCOTT JOULE.]
Under Dalton, Mr. Joule first became acquainted with physical apparatus;
and the interest excited in his mind very soon began to produce fruit.
Almost immediately he commenced experimenting on his own account.
Obtaining a room in his father's house for the purpose, he began by
constructing a cylinder electric machine in a very primitive way. A
glass tube served for the cylinder; a poker hung up by silk threads, as
in the very oldest forms of electric machine, was the prime conductor;
and for a Leyden jar he went back to the old historical jar of Cunaeus,
and used a bottle half filled with water, standing in an outer vessel,
which contained water also.
Enlarging his stock of apparatus, chiefly by the work of his own hands,
he soon entered the ranks as an investigator, and original papers
followed each other in quick succession. The Royal Society list now
contains, the titles of ninety-seven papers due to Joule, exclusive of
over twenty very important papers detailing researches undertaken by him
conjointly with Thomson, with Lyon Playfair, and with Scoresby.
Mr. Joule's first investigations were in the field of magnetism. In
1838, at the age of nineteen, he constructed an electro-magnetic engine,
which he described in Sturgeon's "Annals of Electricity" for January
of that year. In the same year, and in the three years following, he
constructed other electro-magnetic machines and electro-magnets of novel
forms; and experimenting with the new apparatus, he obtained results
of great importance in the theory of electro-magnetism. In 1840 he
discovered and determined the value of the limit to the magnetization
communicable to soft iron by the electric current; showing for the case
of an electro-magnet supporting weight, that when the exciting current
is made stronger and stronger, the sustaining power tends to a certain
definite limit, which, according to his estimate, amounts to about
140 lb. per square inch of either of the attracting surfaces.
He investigated the relative values of solid iron cores for the
electro-magnetic machine, as compared with bundles of iron wire; and,
applying the principles which he had discovered, he proceeded to the
construction of electro-magnets of much greater lifting power than any
previously made, while he studied also the methods of modifying the
distribution of the force in the magnetic field.
In commencing these investigations he was met at the very outset, as he
tells us, with "the difficulty, if not impossibility, of understanding
experiments and comparing them with one another, which arises in general
from incomplete descriptions of apparatus, and from the arbitrary and
vague numbers which are used to characterize electric currents. Such a
practice," he says, "might be tolerated in the infancy of science; but
in its present state of advancement greater precision and propriety are
imperatively demanded. I have therefore determined," he continues,
"for my own part to abandon my old quantity numbers, and to express my
results on the basis of a unit which shall be at once scientific and
convenient."
The discovery by Faraday of the law of electro-chemical equivalents
had induced him to propose the voltameter as a measurer of electric
currents, but the system proposed had not been used in the researches
of any electrician, not excepting those of Faraday himself. Joule,
realizing for the first time the importance of having a system of
electric measurement which would make experimental results obtained
at different times and under various circumstances comparable among
themselves, and perceiving at the same time the advantages of a system
of electric measurement dependent on, or at any rate comparable with,
the chemical action producing the electric current, adopted as unit
quantity of electricity the quantity required to decompose nine grains
of water, 9 being the atomic weight of water, according to the chemical
nomenclature then in use.
He had already made and described very important improvements in the
construction of galvanometers, and he graduated his tangent galvanometer
to correspond with the system of electric measurement he had adopted.
The electric currents used in his experiments were thenceforth measured
on the new system; and the numbers given in Joule's papers from 1840
downward are easily reducible to the modern absolute system of electric
measurements, in the construction and general introduction of which
he himself took so prominent a part. It was in 1840, also, that after
experimenting on improvements in voltaic apparatus, he turned his
attention to "the heat evolved by metallic conductors of electricity and
in the cells of a battery during electrolysis." In this paper, and those
following it in 1841 and 1842, he laid the foundation of a new province
in physical science-electric and chemical thermodynamics-then totally
unknown, but now wonderfully familiar, even to the roughest common sense
practical electrician. With regard to the heat evolved by a metallic
conductor carrying an electric current, he established what was already
supposed to be the law, namely, that "the quantity of heat evolved by
it [in a given time] is always proportional to the resistance which it
presents, whatever may be the length, thickness, shape, or kind of the
metallic conductor," while he obtained the law, then unknown, that
the heat evolved is proportional to the _square_ of the quantity of
electricity passing in a given time. Corresponding laws were established
for the heat evolved by the current passing in the electrolytic cell,
and likewise for the heat developed in the cells of the battery itself.
In the year 1840 he was already speculating on the transformation of
chemical energy into heat. In the paper last referred to and in a short
abstract in the _Proceedings of the Royal Society_, December, 1840, he
points out that the heat generated in a wire conveying a current of
electricity is a part of the heat of chemical combination of the
materials used in the voltaic cell, and that the remainder, not the
whole heat of combination, is evolved within the cell in which the
chemical action takes place. In papers given in 1841 and 1842, he pushes
his investigations further, and shows that the sum of the heat produced
in all parts of the circuit during voltaic action is proportional to the
chemical action that goes on in the voltaic pile, and again, that the
quantities of heat which are evolved by the combustion of equivalents
of bodies are proportional to the intensities of their affinities for
oxygen. Having proceeded thus far, he carried on the same train of
reasoning and experiment till he was able to announce in January, 1843,
that the magneto-electric machine enables us to _convert mechanical
power into heat_. Most of his spare time in the early part of the year
1843 was devoted to making experiments necessary for the discovery of
the laws of the development of heat by magneto-electricity, and for the
definite determination of the mechanical value of heat.
At the meeting of the British Association at Cork, on August 21, 1843,
he read his paper "On the Calorific Effects of Magneto-Electricity,
and on the Mechanical Value of Heat." The paper gives an account of an
admirable series of experiments, proving that _heat is generated_ (not
merely _transferred_ from some source) by the magneto-electric machine.
The investigation was pushed on for the purpose of finding whether a
_constant ratio exists between the heat generated and the mechanical
power_ used in its production. As the result of one set of
magneto-electric experiments, he finds 838 foot pounds to be the
mechanical equivalent of the quantity of heat capable of increasing the
temperature of one pound of water by one degree of Fahrenheit's scale.
The paper is dated Broomhill, July, 1843, but a postscript, dated
August, 1843, contains the following sentences:
"We shall be obliged to admit that Count Rumford was right in
attributing the heat evolved by boring cannon to friction, and not (in
any considerable degree) to any change in the capacity of the metal. I
have lately proved experimentally that _heat is evolved by the passage
of water through narrow tubes_. My apparatus consisted of a piston
perforated by a number of small holes, working in a cylindrical glass
jar containing about 7 lb. of water. I thus obtained one degree of heat
per pound of water from a mechanical force capable of raising about 770
lb. to the height of one foot, a result which will be allowed to be very
strongly confirmatory of our previous deductions. I shall lose no time
in repeating and extending these experiments, being satisfied that the
grand agents of nature are, by the Creator's fiat, _indestructible_, and
that wherever mechanical force is expended, an exact equivalent of heat
is _always_ obtained."
This was the first determination of the dynamical equivalent of heat.
Other naturalists and experimenters about the same time were attempting
to compare the quantity of heat produced under certain circumstances
with the quantity of work expended in producing it; and results and
deductions (some of them very remarkable) were given by Séguin (1839),
Mayer (1842), Colding (1843), founded partly on experiment, and partly
on a kind of metaphysical reasoning. It was Joule, however, who first
definitely proposed the problem of determining the relation between heat
produced and work done in any mechanical action, and solved the problem
directly.
It is not to be supposed that Joule's discovery and the results of his
investigation met with immediate attention or with ready acquiescence.
The problem occupied him almost continuously for many years; and in 1878
he gives in the _Philosophical Transactions_ the results of a fresh
determination, according to which the quantity of work required to be
expended in order to raise the temperature of one pound of water weighed
in vacuum from 60° to 61° Fahr., is 772.55 foot pounds of work at the
sea level and in the latitude of Greenwich. His results of 1849 and 1878
agree in a striking manner with those obtained by Hirn and with those
derived from an elaborate series of experiments carried out by Prof.
Rowland, at the expense of the Government of the United States.
His experiments subsequent to 1843 on the dynamical equivalent of
heat must be mentioned briefly. In that year his father removed from
Pendlebury to Oak Field, Whalley Range, on the south side of Manchester,
and built for his son a convenient laboratory near to the house. It was
at this time that he felt the pressing need of accurate thermometers;
and while Regnault was doing the same thing in France, Mr. Joule
produced, with the assistance of Mr. Dancer, instrument maker, of
Manchester, the first English thermometers possessing such accuracy
as the mercury-in-glass thermometer is capable of. Some of them were
forwarded to Prof. Graham and to Prof. Lyon Playfair; and the production
of these instruments was in itself a most important contribution to
scientific equipment.
As the direct experiment of friction of a fluid is dependent on no
hypothesis, and appears to be wholly unexceptionable, it was used by Mr.
Joule repeatedly in modified forms. The stirring of mercury, of oil,
and of water with a paddle, which was turned by a falling weight,
was compared, and solid friction, the friction of iron on iron under
mercury, was tried; but the simple stirring of water seemed preferable
to any, and was employed in all his later determinations.
In 1847 Mr. Joule was married to Amelia, daughter of Mr. John Grimes,
Comptroller of Customs, Liverpool. His wife died early (1854), leaving
him one son and one daughter.
The meeting of the British Association at Oxford, in this year, proved
an interesting and important one. Here Joule read a fresh paper "On the
Mechanical Equivalent of Heat." Of this meeting Sir William Thomson
writes as follows to the author of this notice:
"I made Joule's acquaintance at the Oxford meeting, and it quickly
ripened into a lifelong friendship.
"I heard his paper read in the section, and felt strongly impelled at
first to rise and say that it must be wrong, because the true mechanical
value of heat given, suppose in warm water, must, for small differences
of temperature, be proportional to the square of its quantity. I knew
from Carnot that this _must_ be true (and it _is_ true; only now I call
it 'motivity,' to avoid clashing with Joule's 'mechanical value'). But
as I listened on and on, I saw that (though Carnot had vitally important
truth, not to be abandoned) Joule had certainly a great truth and a
great discovery, and a most important measurement to bring forward. So,
instead of rising, with my objection, to the meeting, I waited till it
was over, and said my say to Joule himself, at the end of the meeting.
This made my first introduction to him. After that I had a long talk
over the whole matter at one of the _conversaziones_ of the Association,
and we became fast friends from thenceforward. However, he did not tell
me he was to be married in a week or so; but about a fortnight later I
was walking down from Chamounix to commence the tour of Mont Blanc, and
whom should I meet walking up but Joule, with a long thermometer in his
hand, and a carriage with a lady in it not far off. He told me he had
been married since we had parted at Oxford! and he was going to try for
elevation of temperature in waterfalls. We trysted to meet a few days
later at Martigny, and look at the Cascade de Sallanches, to see if it
might answer. We found it too much broken into spray. His young wife, as
long as she lived, took complete interest in his scientific work, and
both she and he showed me the greatest kindness during my visits to them
in Manchester for our experiments on the thermal effects of fluid in
motion, which we commenced a few years later"
"Joule's paper at the Oxford meeting made a great sensation. Faraday was
there and was much struck with it, but did not enter fully into the new
views. It was many years after that before any of the scientific chiefs
began to give their adhesion. It was not long after, when Stokes told me
he was inclined to be a Joulite."
"Miller, or Graham, or both, were for years quite incredulous as to
Joule's results, because they all depended on fractions of a degree of
temperature--sometimes very small fractions. His boldness in making such
large conclusions from such very small observational effects is almost
as noteworthy and admirable as his skill in extorting accuracy from
them. I remember distinctly at the Royal Society, I think it was either
Graham or Miller, saying simply he did not believe Joule, because he had
nothing but hundredths of a degree to prove his case by."
The friendship formed between Joule and Thomson in 1847 grew rapidly.
A voluminous correspondence was kept up between them, and several
important researches were undertaken by the two friends in common. Their
first joint research was on the thermal effects experienced by air
rushing through small apertures The results of this investigation give
for the first time an experimental basis for the hypothesis assumed
without proof by Mayer as the foundation for an estimate of the
numerical relation between quantities of heat and mechanical work, and
they show that for permanent gases the hypothesis is very approximately
true. Subsequently, Joule and Thomson undertook more comprehensive
investigations on the thermal effects of fluids in motion, and on the
heat acquired by bodies moving rapidly through the air. They found the
heat generated by a body moving at one mile per second through the air
sufficient to account for its ignition. The phenomena of "shooting
stars" were explained by Mr. Joule in 1847 by the heat developed by
bodies rushing into our atmosphere.
It is impossible within the limits to which this sketch is necessarily
confined to speak in detail of the many researches undertaken by Mr.
Joule on various physical subjects. Even of the most interesting of
these a very brief notice must suffice for the present.
Molecular physics, as I have already remarked, early claimed his
attention. Various papers on electrolysis of liquids, and on the
constitution of gases, have been the result. A very interesting paper
on "Heat and the Constitution of Elastic Fluids" was read before
the Manchester Literary and Philosophical Society in 1848. In it he
developed Daniel Bernoulli's explanation of air pressure by the impact
of the molecules of the gas on the sides of the vessel which contains
it, and from very simple considerations he calculated the average
velocity of the particles requisite to produce ordinary atmospheric
pressure at different temperatures. The average velocity of the
particles of hydrogen at 32° F. he found to be 6,055 feet per second,
the velocities at various temperatures being proportional to the square
roots of the numbers which express those temperatures on the absolute
thermodynamic scale.
His contribution to the theory of the velocity of sound in air was
likewise of great importance, and is distinguished alike for the
acuteness of his explanations of the existing causes of error in the
work of previous experimenters, and for the accuracy, so far as
was required for the purpose in hand, of his own experiments. His
determination of the specific heat of air, pressure constant, and the
specific heat of air, volume constant, furnished the data necessary for
making Laplace's theoretical velocity agree with the velocity of sound
experimentally determined. On the other hand, he was able to account
for most puzzling discrepancies, which appeared in attempted direct
determinations of the differences between the two specific heats by
careful experimenters. He pointed out that in experiments in which air
was allowed to rush violently or _explode_ into a vacuum, there was a
source of loss of energy that no one had taken account of, namely,
in the sound produced by the explosion. Hence in the most careful
experiments, where the vacuum was made as perfect as possible, and the
explosion correspondingly the more violent, the results were actually
the worst. With his explanations, the theory of the subject was rendered
quite complete.
Space fails, or I should mention in detail Mr. Joule's experiments on
magnetism and electro-magnets, referred to at the commencement of this
sketch. He discovered the now celebrated change of dimensions produced
by the magnetization of soft iron by the current. The peculiar noise
which accompanies the magnetization of an iron bar by the current,
sometimes called the "magnetic tick," was thus explained.
Mr. Joule's improvements in galvanometers have already been incidentally
mentioned, and the construction by him of accurate thermometers has been
referred to. It should never be forgotten that _he first_ used small
enough needles in tangent galvanometers to practically annul error from
want of uniformity of the magnetic field. Of other improvements and
additions to philosophical instruments may be mentioned a thermometer,
unaffected by radiation, for measuring the temperature of the
atmosphere, an improved barometer, a mercurial vacuum pump, one of the
very first of the species which is now doing such valuable work, not
only in scientific laboratories, but in the manufacture of incandescent
electric lamps, and an apparatus for determining the earth's horizontal
magnetic force in absolute measure.
Here this imperfect sketch must close. My limits are already passed. Mr.
Joule has never been in any sense a public man; and, of those who know
his name as that of the discoverer who has given the experimental basis
for the grandest generalization in the whole of physical science, very
few have ever seen his face. Of his private character this is scarcely
the place to speak. Mr. Joule is still among us. May he long be spared
to work for that cause to which he has given his life with heart-whole
devotion that has never been excelled.
In June, 1878, he received a letter from the Earl of Beaconsfield
announcing to him that Her Majesty the Queen had been pleased to grant
him a pension of £200 per annum. This recognition of his labors by his
country was a subject of much gratification to Mr. Joule.
Mr. Joule received the Gold Royal Medal of the Royal Society in 1852,
the Copley Gold Medal of the Royal Society in 1870, and the Albert Medal
of the Society of Arts from the hand of the Prince of Wales in 1880.