The development of the atomic theory

THE

DEVELOPMENT

OF THE

ATOMIC THEORY

BY

ANDREW NORMAN MELDRUrt, I.E.S,

Fellow of the Bombay University

HUMPHREY MILFORD
OXFORD UNIVERSITY PRESS
LONDON, BOMBAY, MADRAS

THE

DEVELOPMENT

OF THE

ATOMIC THEORY

BY

ANDREW NORMAN AiELDRUM, I.E.S.

Fellow of the Bombay University

HUMPHREY MILFOKD
OXFORD UNIVERSITY PRESS
LONDON, BOMBAY, MADRAS

PREFACE

It is now widely recognised that a science cannot be fully
understood without a study of its history. At the same time,
research into the history of the sciences is carried on under
serious disadvantages. There is no special periodical for the
publication of original work in this direction, at least none in
Britain. It is often difficult to obtain the papers that are
published, and difficult to obtain information regarding them.
Even if a paper on the history of chemistry, for instance,
is noticed in the Abstracts of the Chemical Society, one does not
find that the space taken up by the abstract is always directly
proportional to the importance of the paper.

Again, the Universities rarely supply genuine instruction
in the history of science although this is part of the history of
civilisation. A worker on the history of a science is rarely put
in a position to teach what he knows, whilst anyone with an
experimental knowledge of a science is at liberty to discourse
on its history as he may find or make occasion. In this respect
the president of a scientific society is a " chartered libertine."

The consequences of all this, in the history of chemistry at
least, are that original work when published is largely ignored ;
that there is hardly any critical examination of results; and that
errors which were exposed fifty years ago are still rampant.

Some of these observations are illustrated in the following
pages.

A. N. MELDRUM.

MADHAVLAL RANCHHODLAL SCIENCE INSTITUTE,

AHMEDABAD,
BOMBAY PRESIDENCY, INDIA.

THE DEVELOPMENT OF THE ATOMIC THEORY

" What is the good of giving yourself so much trouble and
of composing a history when all you need do is to copy the best
known ones in the usual way ? . . . . Historians copy from one
another. Thus they spare themselves trouble and avoid the
appearance of presumption. Imitate them and do not be origi-
nal. An original historian is the object of distrust, loathing and
contempt from everybody." — Anatole France, Penguin Island.

The fact that the address delivered to a society by its
president, on grounds of etiquette, is not discussed at the time
of delivery, affords a strong reason for regarding it as open to
discussion later. A presidential address to a scientific society
at least, if and when it is put on record, becomes as much open
to comment, and, if need be, to criticism and challenge as any
other scientific publication. This is demanded by the freedom
of science.

The Presidential Address to the Chemical Society (Trans.
1917, 111, 288) declares that "chemistry is an experimental
science aiming at proving all things and holding fast to that
which is good." Whilst this is true, it is not the whole truth.
An experimental science has a history that lies open to study.
The injunction — " prove all things, hold fast that which is
good " — is to be obeyed in studying even the history of an
experimental science.

The Presidential Address just cited is in part taken up
with the treatment of various questions in the history of chemis-
try, and the opinions that it offers, particularly on the develop-
ment of the atomic theory, invite and require examination. It
is said that in ancient times the atomic theory was studied first
by the Hindus and later by the Greeks, and was derived by
the Greeks from the Hindus, (loc. cit., p. 290). This view is
not universally adopted by the Greek scholars of Europe,
and the question where the atomic theory comes from is only a
part of an immense problem, namely, the origin of the Hindu
and Greek civilisations.

In considering this problem an experimental chemist is
of course at a loss : he must be content simply to learn the
opinions of Sanskrit and Greek scholars, whatever these opinions
may be, and however they may alter ffom time to time. The
Presidential Address relies on Daubeny, whose book on the

420223

history of the atomic theory, in its latest edition, was published
in the year 1850. Sir P. C. Ray, who knows Sanskrit as well as
chemistry, inclines to the view that the Hindus did communic-
ate the atomic theory to the Greeks. He does not himself
go into the merits of the question, and he relies on the authority
of others — Max Muller, Colebrooke, H. H. Wilson, . Macdonell —
who, with but one exception, are not representative of modern
Sanskrit scholarship. — (A History of Hindu Chemistry, 2nd
ed., 1903, Vol. 1, Chap. I).

On the other hand, a modern authority on Greek says : —

" No one will now suggest that Greek philosophy came from
India, and indeed everything points to the conclusion that
Indian philosophy came from Greece." — (John Burnett, Early
Greek Philosophy, 2nd ed., 1908, p. 21). Again, "the Greeks
did not borrow either their philosophy or their science from
the East." (p. 27). "The chronology of Sanskrit literature
is an extremely difficult subject, but so far as we can see, the
great Indian systems are later in date than the Greek philo-
sophies which they nearly resemble." (p. 21).

The history of a science must in the main give an account
of the development of ideas : the history of chemistry must
consider the evolution of the atomic theory above all. and en-
deavour to show how the ideas of Leucippus took shape during
the centuries and became the molecular and atomic theory of
the present day. The Presidential Address disposes of this
task in the roundest way :— " The atomic theories of the

ancient philosophers present but little real analogy to that

enunciated by John Dalton more than a century ago." " It is
not possible to attach great weight to the opinions of Newton
and Boyle, ingenious as are their arguments, backed up by
intellects so acute."— (loc. tit., p. 290). " John Dalton 's ideas
were entirely his own " (p. 292). The effect of these statements,
taken together, is to say that John Dalton was the creator of
the modern atomic theory.

A denial that the atomic theory has been evolved, equally
with a denial of evolution in other directions, lies under the
disadvantage that it makes but little appeal to the modern
intelligence.

As will presently appear, the evolution of the atomic
theory in the last hundred and fifty years depended on two
things : — The existence of a prior atomic theory, and the
development of knowledge regarding gases.

THE PRIOR ATOMIC THEORY*

Boyle and Newton were not the only men in the seventeenth
century who concerned themselves with the atomic theory.
Bacon, Descartes, Gassend, Boyle, Hooke, Newton, Locke,
all men trained on the Greek and Latin classics, were interested
in it. One result of their study of the theory was the conclu-
sion that heat is a mode of motion, and Tyndall in his well-
known book, Heat — a Mode of Motion, has amply illustrated
this conclusion by quotation from seventeenth century writers.
Further, Newton's ideas regarding the disintegration of atoms,
derived as they are from Descartes, were thought important
enough by Clerk Maxwell for quotation in the Theory of Heat,
and are of special interest now that numerous scientific men
are actively engaged in the study of atomic disintegration.

The controversy that arose between Franciscus Linus and
Robert Boyle as to the nature of atmospheric pressure, bore
fruit in the discovery of Boyle's law — that the density of a
gas is proportional to the pressure. This law again led Newton
to the first quantitative conclusion ever formed about atoms.
He proved in the Principia that " if the density of a fluid which
is made up of mutually repulsive particles is proportional
to the pressure, the forces between the particles are reciprocally
proportional to the distances between their centres. And
vice versa, mutually repulsive particles, the forces between which
are reciprocally proportional to the distances between their
centres, will make up an elastic fluid, the density of which
is proportional to the pressure. " Newton goes on :— " Whether
elastic fluids do really consist of particles so repelling one
another, is a physical question. We have here demonstrated
mathematically the properties of fluids consisting of this kind,
that hence philosophers may take occasion to discuss that
question."— (Principia, Book II, Prop. 23).

Newton advanced the hypothesis of an elastic fluid, composed
of particles which repel one another in a definite way. This
hypothesis, when taken up by Bryan Higgins and William
Higgins and by John Dalton, was the germ of the atomic

* Many of the topics which are considered in what follows have been
treated already by the author in a series of papers on the development of
the atomic theory \-Manc h. Mem., 54,No.7, 55, Nos. 3, 4, 5, 6, 19 and 22.
(See also Brit. Ass. Rep., 1908, p. 668, and New Ireland Review, 1910,
pp. 275, 350). Where the Presidential Address treats of these topics it can
be regarded as written either without knowledge of, or in arswer to, the
above papers.

theory of the early nineteenth century. As will be seen, the
evolution of the theory can be explained in this way and
in no other.

THE DEVELOPMENT OF KNOWLEDGE
REGARDING GASES

The Presidential Address offers the following summary
of the work that led up to the formation of a chemical atomic
theory ; — " The quantitative experiments of Black, Wenzel,
Richter and Lavoisier undoubtedly prepared the way for a
real atomic theory." — (loc. cit., p. 291).

Here the names of Wenzel and Richter are open to challenge
and the Presidential Address proceeds with an account of
Wenzel's work to which strong exception must be taken.

" Wenzel's experiments, which were remarkably accurate,

showed that when two neutral salts decompose each other,
the resulting compounds are also neutral Richter, follow-
ing on those lines, drew up a table of acids and bases which
respectively neutralised each other to form salts."

This account of Wenzel is unfortunate, because it is simply
the vestige of an error that originated with Berzelius and that
has been repeatedly exposed by the historians of chemistry,
(e. g. , Anrus Smith, Memoir of John Dalton and History of the
Atomic Theory, 1856, pp. 160-166 ; Soderbaum, Berzelius.'
Werden and Wachsen. 1899, pp. 138-9). In short, it has been
known for many years that Wenzel, having studied the problem
of the mutual decomposition of salts, came to the wrong conclu-
sion. His work, however, is far from being negligible. He
was the forerunner, not of Richter and Proust and Dalton,
but of Berthollet, of Wilhelmy, of Guldberg and Waage. He
had a glimpse of the law of mass action, and his work can
be understood from this point of view, and from this point of
view only.f

Richter, who also studied the problem of the mutual
decomposition of salts, came to the right conclusion. Even so,
he had very little influence, if any, on the formation of the
atomic theory. His work was done and published too late to
influence William Higgins, and it had little influence on John

t See, for instance, Mellor, Chemical Statics and Dynamics, 1914.
pp. 4, 19, 29, 128, 178f

3

Dalton. Roscoe and Harden have shown from Dalton's
note-books that his chemical atomic theory was formed in the
year 1803, and that the earliest reference to Richter in the
note-books bears the date April 19th, 1807. — (Roscoe and
Harden, New View of the Origin of Dalton's Atomic Theory,
pp. 46, 79, 91).

Thus, of the workers named in the Presidential Address
as having prepared the way for an atomic theory, there are
left for consideration only two — Black and Lavoisier. It is
said that " the experiments of Black on " Magnesia Alba "
marked a new departure in the mode of attacking chemical
problems."— (loc. cit., p. 291). The Address goes on to quote a
passage from Black which makes it plain that, instead of claiming
to have made a departure in chemical method, Black regarded
himself as having proceeded on the same lines as previous

workers. " Chemists have often observed that part

of a body has vanished from their senses and they

have always found upon further inquiry, that subtle part to
be air, which having been imprisoned in the body, under solid
form, was set free, and rendered fluid and elastic by the fire.
We may therefore safely conclude that the volatile matter
lost in the calcination of magnesia is mostly air."

Black, in studying the mild and caustic alkalies, used the
balance mainly as an indicator of loss or gain of carbon dioxide.
He made no effort to attain extraordinary accuracy, and he
did not use his results to arrive at the composition of the
carbonates by weight.

Because Black made an advance in knowledge of the
carbonates one need not infer that he was the first chemist
to buy a balance. The opinion that it was Black who introduced
the use of the balance into chemistry is just as false as the
opinion that it was Lavoisier. This has already been pointed
out in the Alembic Club Reprint of Black's paper :< — " The

introduction of the quantitative method into chemistry

did not by any means originate with Black. "—(Alembic
Club Reprints, No. 1, Preface by L. D.). Quantitative
experiments on combustion had been made a hundred
years before the time of Black. The Essai of the year
1630, in which Jean Rey surmised that a metal increases
in weight because the "air is thickened and rendered
adhesive to the metal," indicates that Rey made few if any
experiments of his own on the subject. Forthe fact of increase of
weight on calcination he relied chiefly on the work of others —

6

Brun, Garden, Scaliger, Fachsius, Caesalphms, Poppius,
Libavius, and some of these workers had observed the fact many
years before. (Alembic Club Reprints, No. 11, pp. 5, 36, 37, 39,
41, 43, 49).

There is no reason to think that the use of the balance
made the difference between the old chemistry and the new.
The balance was used for centuries without much light being
thrown on chemical problems. Lavoisier, who used it and
reached a point in his work at which a knowledge of oxygen
became indispensable, did not discover oxygen.

Hopkins, in pointing out the importance of qualitative
knowledge in biological chemistry, remarks : — " We all know
that to arrive at the mathematical form is the ultimate goal
of all real scientific knowledge ; but at a given moment in the*
history of a science, qualitative knowledge maybe as important
as the consolidation of other knowledge in a mathematical
form." (Chem. Soc. Ann. Rep., 1916, 13, 193).

Chemists might make quantitative experiments, but in
the absence of knowledge regarding the gases, oxygen above
all, they were simply groping in darkness. The prologue to the
systematic study of the gases is found in the work of Hales,
albeit Hales was greatly indebted to Mayow and to Muschen-
broeck. " His experiments," says Priestley, " are so numerous
and varied that they are justly esteemed to be the solid founda-
tion of all our knowledge of this subject. " (Experiments
and Observations on different Kinds of Air, 2nd ed., 1775, p. 4).
He showed that gas is given off in numerous chemical changes,
and he concluded that the gas had been present, — " fixed, "
using Mayow '9 expression — in the original substances. In
his experiments he produced carbon dioxide, nitric oxide,
hydrochloric acid, ammonia, oxygen, etc., the remarkable
thing being that he never realised that one gas is a distinct
substance from another.

Hales was the " father in chemistry " of Black and of
Priestley. Black showed in the year 1755 that by depriving a
mild alkali of " fixed air " a caustic alkali is formed, and that by
combining a caustic alkali with " fixed air " a mild alkali is
formed. Thus he proved that in well known chemical changes
a particular gas takes part. For many years chemical thought
had been poisoned by the confusion of one gas with another,
and of all gases with ordinary air. The general effect of Black's
work was to show the importance of studying gases. He says
this himself :•— " Curious chemists tried to produce new airs,

as they were called, by every possible means, in the expectation
of singular results and discoveries. And thus has arisen a new
species of Chemistry which may be called Pneumatic Chemistry."
Black left the development of the subject to others. Cavendish
had measured the volume of the gas given off by the action of
acids on carbonates and the density and solubility of the gas.
The subsequent work of Cavendish on gases is well known, as
well as the work of Rutherford, Scheele and Priestley.

Priestley studied specially nitric oxide, hydrochloric
acid, ammonia and oxygen gases, each of which Hales had had
under observation. His discovery of oxygen in the year
1774, as a gas in which a candle burns vigorously, was the
starting point of modern chemistry. He happened to communi-
cate this observation almost at once to Lavoisier, and Lavoisier
was in a better position than any other man in the world to
see its importance. The qualitative chemist had come to the
aid of the quantitative. In Priestley's discovery Lavoisier
found the clue to his own patient and exact work. Hence-
forth his task as a chemist consisted in the study of oxygen,
in showing that oxygen plays in nature, on a vast scale, the part
that carbon dioxide plays in the chemistry of the mild and
caustic alkalies. " Vast intellectual and material continents
lay for the first time displayed, opening fields of thought and
fields of enterprise of which no one could conjecture the limit."

THE CHEMICAL ATOMIC THEORY

Speculation is excited by a striking discovery, and speculat-
ions concerning the nature of matter have often arisen from
discoveries regarding the gases. As has already been shown,
Newton, in order to account for Boyle's law, was led to form
the hypothesis of an elastic fluid composed of particles which
repel one another in a definite way, this hypothesis being the
earliest known instance of the exact treatment of the atomic
theory.

The Presidential Address never mentions Priestley, whose
work not only was the starting point of Lavoisier's system of
chemistry, but gave a stimulus to the formation of a chemical
atomic theory. In the first place a preliminary atomic theory
arose out of Priestley's discovery that hydrochloric acid and
ammonia can exist as gases. Bryan Higgins, who was a student
of Newton's works, applied the doctrine of " particles mutually

8

repulsive " to the case of these two gases. He thought that on
combination with one another the gases must unite particle
with particle, and in this way only. He reasoned that two
particles of ammonia could not combine with one of acid, for, if
the three were to meet, the two of ammonia must repel one
another and one of them must be driven away from the acid
atom. For a similar reason, two atoms of acid could not
combine with one of ammonia.

Bryan Higgins attempted to explain other facts in terms
of this theory. He took it as a general rule that when a salt
crystallises from water which contains acid, the salt does not
carry down acid with it. The cause was, he thought, that the
particles of acid in the salt repel the particles of acid in the
water. This, right or wrong, illustrates the fact that Bryan
Higgins, as a follower of Newton, had formed precise views
about the combination of atoms.

Once Lavoisier knew how to prepare oxygen the fate of
the phlogiston theory was sealed. Bryan Higgins, however,
continued for years to believe in the theory and thus, of
necessity, he was confined to incorrect views regarding the
composition of matter and prevented from improving his
atomic theory. His nephew, William Higgins, whom he trained
in chemistry, became an early convert to Lavoisier's doctrines
and published in the year 1789 a book entitled A Comparative
View of the Phlogistic and Antiphlogistic Hypotheses. This
book has two remarkable features : it expounds Lavoisier's
teaching against phlogiston, and it contains a much
improved atomic theory. The Presidential Address disparages
the atomic theory of William Higgins :• — " His suggestions
were involved and hidden in much phlogistic matter, apparently
without any clear ideas underlying them as to the nature of
compounds " — (loc. cit., p. 292). These words encourage the
suspicion that they are based on an imperfect acquaintance
with the book referred to, for they make the suggestion that
Higgins was an ignorant believer in phlogiston. On the contrary,
William Higgins deserves all the credit of having written the
earliest book in the English language against the phlogiston
theory. Further, he found the germ of an atomic theory in his
uncle's work, and Lavoisier's teaching enabled him to develop
the theory from the germ. The nephew's theory was an
improvement on the uncle's, and both were based on Newton's
doctrine of an elastic fluid composed of mutually repulsive
particles.

It is all in the natural order of things. The Presidential
Address justly says that " the numerous and accurate experi-
ments of Lavoisier gave abundant data and prepared

the ground for theoretical explanation. " William Higgins,
learning from Lavoisier that the element oxygen may combine
with another element in more than one proportion, supposed
that these elements tend to combine first in the proportion
atom to atom. The next possible combination was two atoms
of oxygen to one of the other element, then three to one and
so on. Because like atoms repel one another, the most stable
combination was 1 to 1, then 2 to 1, then 3 to 1, and so on. His
views as to water can be expressed in the formula OH, as to
oxides of sulphur by OS and 02S, as to the oxides of nitrogen
by ON, O2N, O3N, O4N, OSN. It was unfortunate for
chemistry that the importance of William Higgins' ideas regard-
ing atoms was not perceived at the time he published them.
His theory "fell on a heedless world", just as Newland's system
of the elements fell on a heedless Chemical Society.

John Dalton's chemical atomic theory was formed about
fourteen years later. The first known table of atomic weights,
as Roscoe and Harden have shown (op. cit., p. 28), appears
in Dalton's note-books under the date September 6th, 1803.
The atomic weight tables which he drew up later differ much in
details from the first, but they are based on the same principles.
Hence a full explanation of how this first table arose would
be an account of the origin of Dalton's chemical atomic theory.

Dalton had formed a physical atomic theory previ-
ously to the chemical ; it arose out of his study of the gases
that had been discovered in the atmosphere. The fact that
the gases in the atmosphere are uniformly mixed, although
they have different densities, had led to the almost universal
belief that they existed there in a state of chemical combination
with one another. Dalton's instincts and his experiments
led him to the contrary belief, that the atmosphere is a physical
mixture. In the year 1801 Dalton proved that the pressure
in a mixture of gases is the sum of the partial pressures, so that
each gas in a mixture exerts its own pressure as if the others
were absent. Other discoveries followed on this. Dalton
studied the vapour pressure of liquids, particularly of water,
and was thus enabled to explain evaporation and the dewpoint.
In 1802 he established the fact of gaseous diffusion, " that a
lighter gas cannot rest upon a heavier," which Priestley had
doubted.

10

In 1803 Henry showed that the amount of a gas which
dissolves in a liquid is proportional to the pressure, and Dalton
followed at once with the observation that in a mixture of
gases exposed to a liquid each gas dissolves according to its
partial pressure.

In the year 1801 Dalton advanced a theory of mixed gases
which he stated as follows :• — " When two elastic fluids, denoted
by A and B, are mixed together, there is no mutual repulsion
amongst their particles, that is, the particles of A do not repel
those of B, as they do one another." This theory, as being
an obvious attempt to extend Newton's hypothesis regarding
a single elastic fluid to the case of a mixture, proves that Dalton
was a Newtonian.

When his chemical theory is examined Dalton is found
to be a Newtonian still. The fundamental rule of this theory
is that different atoms tend to combine in the proportion
of atom to atom. When only one compound of two elements
was known it was presumed to be binary, e.g., water was
formed by the union of one atom of oxygen with one of hydrogen,
ammonia by the union of one of hydrogen with one of nitrogen.

Afterwards, when Dalton was challenged to justify this
rule, he pointed out that if an element A unites with an element
B, the repulsion of the atoms of B for one another must tend
to the formation of a binary compound. " Binary compounds
must first be formed, then ternary, and so on, till the repulsion
of the atoms of B refuse to admit any more." —
(Nicholson's Journal, 1811, 29, 147). Thus Dalton 's physical
theory and his chemical theory have a common basis in Newton's
doctrine of mutually repulsive atoms. Although the Presi-
dential Address says that "it is not possible to attach great
weight to the opinions of Newton" and that " Dalton's theory
was entirely his own," there is no room for doubt that Dalton
was a Newtonian, as Bryan Higgins and William Higgins were
before him.

THE RECEPTION GIVEN TO DALTON'S
CHEMICAL THEORY

The Presidential Address says " the new theory was very
rapidly welcomed and adopted in this country especially,
and owes its rapid acceptation very largely to the energy and
enthusiasm of Professor Thomas Thomson. . , the great

11

influence possessed by W. H. Wollaston contributed

largely to its immediate acceptance amongst scientific men."
— (he. tit., p. 294).

There is confusion of thought here in two directions. In
the first place the Presidential Address ignores the distinction
between law and theory, — between the law of combination in
multiple proportions and the theory based upon it. Wollas-
ton was a believer in the law and he adduced in the year 1808
cases of it which he had observed amongst salts. But he ought
not to have been named as a direct supporter of the atomic
theory. Like Davy, he was sceptical about atoms, and he was
the advocate of " equivalents " instead.

Again, the Presidential Address ignores the difference
between making a theory known to scientific men, and inducing
them to embrace it. Thomas Thomson's enthusiasm over the
theory was genuine and his efforts to make it known were
successful, yet Dalton and he remained for many years the only
chemists in Britain who proved their faith in the theory by
work.

The address says that Dalton, " having clearly stated the
theory, proceeded to establish it on a thoroughly sound experi-
mental basis." — (loc. cit., p. 293). This statement is ambiguous.
It is true as a statement of what Dalton attempted to do. If it
means that Dalton succeeded in his attempts, this is the precise
opposite of what all people who know about him believe. Thom-
son, again, was not happy in his attempts to establish Prout's
hypothesis regarding atomic weights. In fact, Dalton was a
much less accurate worker than Thomson, and Thomson a much
less accurate worker than Berzelius. It was Berzelius who,
by the exercise of energy, skill and judgment, put the atomic
theory on a thoroughly sound experimental basis, and thereby,
far more than any other chemist, brought about its acceptance
in the scientific world.

THE QUESTION OF PRIORITY BETWEEN HIGGINS
AND DALTON

The Presidential Address touches on the question of the
priority of Higgins over Dalton in the matter of the atomic
theory. It admits that Higgins' essay of the year 1789
" seems at first sight to contain and set forth a theory of
matter closely resembling that put forward 'by Dalton a few

12

years later. " — (loc. cit., p. 292). This admission is to be
taken for what it is worth : it amounts to first impressions,
and first impressions only, of a book that was published
more than a century ago. This is trifling with the question.
A man must have perfect mastery of a question if he can
trifle with it and at the same time say the last word upon it.

The Address makes no attempt fully and finally to
assess Higgins' claims: it avoids this by proceeding to
deprecate " acrimonious and fruitless discussions as to
priority." After all, from the scientific point of view,
acrimony is merely irrelevant to discussion. Questions of
priority are essentially intellectual. Chronology is the
indispensable basis of history, and the history of science
turns on matters of piiority. Questions of priority in
science might be discussed absolutely without feeling, if
human nature would allow scientific papers to be published
anonymously,

People go into the questions that interest them. In the
address the President asserts his own priority on two matters : —
(1) The atomic weight of nitrogen, which, in a paper read in
1901, he showed to be exactly 14 (14-000 or 13-999) ; (2) the
atomic weight of iodine which he found to be higher than
Stas' value. " Still more remarkable was the publication
five weeks afterwards * by Ladenburg, who arrived at a number

almost identical with that given by me the higher

value has been thoroughly established by work on other ratios
by Baxter and others of the Harvard school." — (loc. cit., p. 3(-8).

Thus a president can make use of his position to assert his
own priority and to deprecate discussion regarding the priority
of a worker who cannot speak for himself. It is to be noted
that stress is laid on a priority of five weeks over Ladenburg,
whilst the interval between Higgins' atomic theory and Dalton's
— fourteen years at least — is alluded to as " a few years. "

The controversy which arose over the claims of Higgins and
Dalton to the chemical atomic theory, and which continued
between the years 1810 and 1818, did not prove entirely fruit-
less. W. H. Wollaston took the side of Higgins at the time,
and after the controversy had died down other men of weight,
Thomas Graham and Sir John Herschel, for instance, took
occasion to assert the priority of Higgins. Herschel intro-
duces the subject in his dialogue On Atoms. (Popular Lectures
on Scientific Subjects, 1868, p. 453).

* The italics are in the original.

13

Hermione. — " Do tell me something about these
atoms. I declare it has quite excited me ; specially
because it seems to have something to do with the atomic
theory of Dalton."

Hermogenes. — " Higgins, if you please."

Coward and Harden in a recent paper afford proof that the
essential identity of Higgins' theory and Dalton's can no
longer be denied. The object of their paper is to give an
account of the lecture-sheets that Dalton prepared to illustrate
the atomic theory. The authors describe " Sheet 12" thus : —
" Five oxides of nitrogen, represented as compounds of one
atom of nitrogen with one, two, three, four and five atoms of
oxygen." On this they make the following comment :< — " It
is improbable that Dalton himself ever adopted these formulae
for the oxides of nitrogen. The sheet was perhaps used to

illustrate some contemporary views on the subject or

possibly even those of William Higgins, A Comparative View
of the Phlogistic and Antiphlogistic Hypotheses, 1789,
pp. 132-5."— (Manch. Mem., 1915, 59, No. 12, p. 52).

Evidently, then, the doctrine of chemical combination
in multiple proportions is embodied in William Higgins' atomic
theory of the year 1789. Coward and Harden make the admis-
sion, intentional or unintentional, that Higgins' and Dalton's
chemical atomic theories are essentially the same. Hence it
follows that Higgins forestalled Dalton.

The resemblance between William Higgins' ideas and
John Dalton's is indeed so complete that it can be accounted
for only on one or other of two suppositions : — (1) That Dalton
plagiarised from Higgins. There is, however, no necessity
for adopting this supposition. (2) That Higgins and Dalton
each started from the same hypothesis, namely, Newton's
doctrine of an elastic fluid composed of mutually repulsive
particles, followed much the same train of thought and reached
essentially the same conclusions.

Printed by G. W. and A. E. Claridge at the Caxton Works, Frere Road,

Bombay.

—

-17°'