The air seems to contain an acid, as appears from the regeneration
of vitriolic acid after the calcination of Vitriol, and from the
rusting of steel filings in a moist air; p. 10. A component part of
the acid of nitre, is derived from the air, which evidently contains
something necessary to the support of flame. But this aereal pabulum of
flame, is not air itself, for air remains when the confined taper is
extinguished: nor is it as vulgarly supposed, the salt called nitre, p.
12. But that these fire-air particles exist also in nitre is evident,
since this salt will support the combustion of sulphur in vacuo. Fill a
tube with gunpowder slightly moistened, and it will burn out in vacuo,
or with its mouth inverted over water. Hence the aereal part of nitre,
is the same with the fire-air particles of the atmosphere, and is one
component part of the acid spirit of nitre: the other being (like the
fixed part) obtained from the earth, p. 17. 18. The fiery particles
thus common to nitre and to the air, he denominates nitro-aereal. It
is these that give causticity to spirit of nitre, and occasion the
red fumes observed in distilling it, p. 18. They do not take fire of
themselves in nitre, because they are inveloped with moisture; but when
combined with salt of tartar, and thrown on the fire in a dry state
they inflame, p. 20.
CHAP. _3d. Of the nature of the nitro-aereal and fiery spirit._ Fire
he conceives to consist of these nitro-aereal particles set in violent
motion by means of sulphureous bodies, in the cases of culinary fire:
but by some other means, in the cases of the solar rays collected by a
burning glass, and of the celestial fires. The corrosive and caustic
nature both of fire and nitrous acid, seems to argue that it proceeds
in both from the nitro-aereal particles they contain, 22-24. That fire
is not of a sulphureous nature is evident, for nitre will not take fire
in an ignited crucible; but oil thrown in, takes fire immediately. So
if a piece of metal be held over a candle, the fire particles pass
through the metal, but the sulphureous smoke adheres to the under side.
p. 27.
That the heat occasioned by a burning glass, consists of these
nitro-aereal particles is evident, for diaphoretic antimony may be
made, either first by calcination with a lens, or secondly, by the
repeated affusion of nitrous acid, or thirdly, by the deflagration
of nitre on the antimony. Diaphoretic antimony made by calcination,
increases on weight,[44] by means of the nitro-aereal particles fixed in
it by the process. p. 28, 29.
[44] It was first observed by John Rey in 1630 that metals calcined,
gain weight by the absorption of air. See an account of his book by M.
Bayen Journ. de Rozier 1775 v. 1 p. 48. There are also some experiments
by Boyle that shew the accession of weight on the calcination of
metals, but he does not seem aware of the theory. Shaw’s Boyle, Fire
and Flame weighed v. 2 p. 394, &c.
CHAP. _4th. On the origin of acid liquors, and the earthy part of
Spirits of nitre._ From p. 34, it appears that he knew nothing of
the absorption and combination of his nitro-aereal particles in the
vitriolic acid, during the combustion of sulphur, but explains the
whole mechanically by the saline portion of the sulphur being broken
down into minute pointed particles, by the violent attrition of the
nitro-aereal particles, and so becoming fluid and sharpened. He seems
too, not to know that the colcothar of martial vitriol is no component
part of sulphur, p. 37. The same mechanical explanation he applies
to the formation of the ligneous acids, and to the impregnation
of the caput mortuum or colcothar of vitriol, with fresh acid by
exposure of air. In the succeeding paragraph, p. 39, he supposes that
marchasite (martial pyrites) imbibes the nitro-aereal particles from
the atmosphere, and thus acid is formed. In like manner he explains the
formation of acids produced by fermentation, by the collision between
the nitro-aereal, and the sulphureo-saline particles of the mass. p.
41. So also he supposes nitrous acid to be produced by the detention
of his nitro-aereal particles by the terrene saline particles found
in the earth, p. 43. Hence he concludes generally, p. 43, that acid
salts are formed from a saline basis brought into fusion or fluidity
by the nitro-aereal part of the air: and sums up his theory of nitre,
by stating it to be a triple salt, composed of nitro-aereal particles,
united to a terrene basis forming the acid, which then unites to the
fixed basis, supplied also by the earth.
CHAP. _5th. On Fermentation._ He gives in this chapter his theory
of fermentation, as arising from the conflict of his nitro-aereal
principle which he thinks may be termed mercury, and the sulphureous
principle: evidently meaning by the latter, the Phlogiston of Stahl:
and he states broadly, p. 60. that pure sulphur can never admit of
accension, but by means of the nitro-aereal particles obtained from the
atmosphere. The rest of his reasoning in this chapter, does not seem
deserving of further notice.
CHAP. _6th. On the nitro-aereal spirit as the cause of rigidity and
elasticity._ These he explains by the fixation and state of his
nitro-aereal particles in bodies endowed with these properties. In p.
69 he endeavours to account why boiled water freezes sooner than that
which has not been boiled; a fact which Dr. Black has made the subject
of a paper in the 45th vol. of the Philosophical transactions. But his
reasonings throughout this chapter are not calculated to add to his
reputation, or to the mass of knowledge of the present day.
CHAP. _7th. The elastic force of the Air depends on its nitro-aereal
particles. In what way exhausted air is reimpregnated with them. Of the
elements of Heat and Cold._ This chapter contains experiments to shew
that the elasticity of the air is owing to the nitro-aereal particles
contained in it: which may be destroyed by the burning of a candle or
other combustible substances, and also by the breathing of animals.
When the atmospheric air contained in a glass jar inverted over water,
will no longer support flame or animal life, the water rises in the
jar, owing to the diminished elasticity of the air, not being able to
counteract the pressure of the surrounding atmosphere on the water p.
100. He finds p. 101 that the diminution by burning a taper in a given
quantity of the air, is about one thirtieth of the whole, and by the
breathing of mice and other animals about one fourteenth. Thence he
concludes p. 106 that by means of respiration the elastic part of the
air enters into the blood, and that the sole use of the lungs is not as
some suppose, to break down the blood in its passage into very minute
particles. That combustion and respiration have similar effects on
atmospherical air, he concludes, p. 108, from the fact, that a candle
and a small animal inclosed together in a glass jar over water, the one
will not burn, nor the other remain alive above half the time that they
would if alone. Mayow however, did not consider his nitro-igneous and
elastic particles to be either pure air, or even a component part of
the common air, as air, notwithstanding the ambiguity of the passages
in p. 114 and 118; but as particles of a different nature, attached
to and fixed in the atmospheric particles; and detached (_excussas_)
by the means above mentioned, p. 118 and 121. His explanation of
elasticity generally in this chap. and of the difficulty arising from
the obvious resistance to the Atmosphere, and the expansibility of the
air in which a taper has been extinguished, or an animal died, seem
too obscure and unintelligible to merit transcribing. It is evident
however upon the whole from p. 123 compared with p. 100 and 135 that
he conceived the diminution of such air to arise from diminished
elasticity, but he supposes it to be denser than common air 123. In a
subsequent part of this chapter p. 128 et seq. he states his theory
of the manner in which deteriorated air recovers its loss, viz. that
the nitro-aereal particles being lighter than the atmospherical, float
abundantly in the higher regions; and that the part of the atmosphere
deprived of them below, being forced upward by the pressure of the
atmosphere above, obtains a renewal of these particles by mixture with
the strata where they abound.
The element of fire, he supposes to reside in the body of the Sun,
which is no other than a mass of nitro-aereal particles driven in
perpetual gyration with immense velocity. Cold, which he considers as
some thing positive (p. 130) he thinks consists in these particles
assuming a pointed form, and moving not in gyration but strait forward.
Much of his reasoning indeed throughout the book, savours greatly of
the mechanical and corpuscular philosophy prevalent in his day.
CHAP. _8th. On the nitro-aereal spirit as inspired by animals._
Formerly he thought that in respiration the nitro-aereal particles
were rubbed or shaken off (_atterere_, _excutere_ 146) from the common
air by the action of the lungs, at present he thinks the air itself
enters the mass of the blood, is there deprived of these particles,
and of part of its elasticity. To prove this he produces an experiment
of the diminution of air by the vapours from iron dissolved in nitrous
acid: but the beautiful deductions of Dr. Priestley from a similar
experiment, never occurred to him; on the contrary he expressly states
that it is an Aura, but not Air p. 145 and though afterward in chap. 9
p. 163, 164 he inclines to doubt, yet again in p. 168 he denies it that
character.
In p. 146 he proceeds to state the uses of these nitro-aereal
particles, which (147) he considers as the principle of life and
motion both in animals and vegetables. By the mutual action of the
nitro-aereal, with the sulphureo-saline particles contained in the
blood, a fermentation is excited necessary to animal life, and to
the warm fluid circulation of the blood (_ad sanguinis æstum_.) To
these particles imbibed from the air, he attributes the difference
in colour between the venous and arterial blood; and he shews this,
from the numerous air bubbles arising in an exhausted receiver from
warm arterial blood: but his experiment to illustrate the difference,
from the colour produced by the nitrous acid with vol. alk. seems very
little to the purpose p. 150.
To the fermentation arising from this mixture of nitro-aereal particles
with the blood, he ascribes animal heat, and accounts satisfactorily
for the increased heat of the body during strong exercise, from the
more frequent inspirations occasioned by the exertion (p. 152, 306:)
but his replies to the objections of Dr. Willis, drawn from the
phenomena of fermenting mixtures, are very inconclusive.
CHAP. _9th. Whether air can be generated anew._ He repeats the
experiment of dissolving iron in dilute nitrous acid, and finds
that though some of the vapour be absorbed, a portion still remains
uncondensible even by severe cold. On substituting dilute vitr. for
nitr. acid he finds an aura which is hardly absorbed or condensed
at all. Hence he doubts whether these auræ be not entitled to the
appellation of air, especially as by subsequent experiment he shews
that they are equally expansible with common air. In making this last
experiment he exhibits the method of transferring air from one vessel
to another (Tab. 5. Fig. 5.) much in the manner afterwards described
by Mr. Cavendish in 1766.[45] From the inability of these auræ to
support animal life (Tab. 5. Fig. 6.) he concludes finally that they
are not air, though not very dissimilar p. 171. The succeeding five
chapters do not seem to contain any facts or conjectures that can add
to Mayow’s reputation. His Hypotheses are completely superceded by
the more accurate knowledge of the present day. In his tract on quick
lime p. 225 he seems to have forestalled the acidum pingue of Dr. Meyer
published exactly a century afterward. It may be noted that in his
treatise on the Bath waters p. 259, he describes fishes as collecting
vital air from the water, and respiring like land animals. (Aereum
aliquod vitale ab aquà, veluti aliàs ab aurà secretum et in cruoris
massam trajiciatur.) The air bladder he considers rather as a reservoir
of air to be inspired, than a receptacle for excreted air; though the
latter opinion is made probable by Dr. Priestley.[46]
[45] Boyle had invented an apparatus for transferring air from one
receiver of an air-pump to another, but not under water.
[46] See Nich. Journ. v. 3 p. 119 on the probability of fishes
separating oxygen from the water they inhabit.
The first part of his _Treatises on Respiration_ is chiefly anatomical.
In p. 300 et seq. he states more fully his opinion, that vital air,
is of a nitro-saline nature: that it is the principle of life, both
in Animals and Vegetables: that combined with the sulphureo-saline
particles in the blood, it is the stimulus to the muscular fibre, and
of course to the heart as a muscle, p. 305; but that the fermentation
occasioned by the introduction of these particles into the blood, is
not confined to the left ventricle of the heart, but commences, in the
passage of the blood through the lungs, and continues in the Arteries.
This evidently approaches the theory, advanced by Dr. Goodwyn in his
tract on the Connection of life with respiration about sixteen years
ago, viz. that the pure air combined with the blood is the stimulus
to the left ventricle of the heart, and produces the alternate
contraction, and dilation on which the circulation depends. Dr. Lower,
in his treatise de motu sanguinis, and Fracassati, and Dr. Frederick
Slare attributed the change of the colour of venous blood into a florid
red, to the combination of the air with it. Lower I believe preceded
Mayow, who quotes him, p. 148; the date of Fracassati’s and Dr.
Slare’s’ observations I have not been able to ascertain, but they must
have been near the time of Mayow. Lowth. Ab. v. iii. p. 237.
In his third treatise on respiration, he explains the Animal œconomy
of the fœtus in utero, by suggesting that the fœtus is supplied by
the placenta, not with venous, but with arterial blood brought
by the umbilical Arteries; so that the required stimulus of the
nitro-aereal particles being thus conveyed, supercedes the necessity
of the lungs for the purpose. This he ingeniously illustrates by the
known experiment, that a dog into whom arterial blood is infused,
though respiring with great difficulty before, hardly respires at all.
A similar theory he applies to the life of the chick in ovo. This
treatise seems to have suggested Dr. Beddoes’s illustration of his
theory of consumption from the state of pregnancy.
In a subsequent Essay on animal spirits, he conceives them to be, if
not the same with the nitro-aereal part of the atmosphere, yet to
consist of this, so far as they are necessary to the production of
muscular motion, which he attributes entirely as before to nitro-aereal
particles, p. 24 and 40, of chap. 4, on the animal spirits.
I do not observe any thing else in Mayow’s book worth noting on the
present occasion; or sufficiently connected with pneumatic Chemistry.
From the analysis thus given of[47] what Mayow has advanced, it
appears, that he clearly comprehended the atmosphere to consist of
a mixture of two parts, the one the efficient cause of life and of
combustion, the other not of itself necessary to either.
[47] At the time this was written neither Dr. Bostock’s treatise on
respiration or the books therein quoted p. 200 had arrived here. Nor
have I had an opportunity of consulting the references there made to
Prof. Robinson, Dr. Thompson, Dr. Yeates, or Fourcroy’s account of
Mayow.
That the vital part of the air, was also a constituent part of nitre,
the effects of both being in essential particulars the same.[48]
That the vital part of the atmosphere entering the blood through the
vessels in the lungs, is conveyed to the left ventricle of the heart,
and becomes the stimulus to the contractions of that muscle, and is
equally essential to the whole system of muscular contraction.
[48] Mr. Ray wrote “A dissertation (in 1696) about respiration,” in
which he supposes the air to pass from the bronchia and lungs into
the substance of the blood, and there (pabuli instar) it foments and
maintains the vital flame which he supposes to be in the sulphureous
parts of the blood, as the air foments the common flame of a candle,
and that the nitre has nothing to do with it. See Durham’s collection
of Ray’s letters.
That the vital part of the atmosphere thus combined with the blood
becomes also the source of animal heat.
That this vital part is equally necessary to the fœtus in utero as
to the adult, and that the use of the lungs in the former case is
superceded by the functions of the umbilical artery and placenta;
by means of which, blood already impregnated with the vital air, is
conveyed to the fœtus.
That the respiration of fishes, is dependant on the particles of air
mixed with watery element they inhabited.
That heat, flame, and combustion, depend on two universal principles,
and the gentleness or violence of their mutual conflict: the one being
a principle of inflammability universally diffused in combustible
bodies, and the other the vital or igneous part of the atmosphere.
These propositions evidently touch upon the most brilliant of the
pneumatic discoveries of the authors already quoted; and not a little
extraordinary it is, that they should have remained so long unknown,
unnoticed, and not understood.
The sulphur of Mayow is decidedly the Phlogiston of Stahl; the fire
air of the former is the fire air of Scheele, the dephlogisticated air
of Priestley, and the Oxygen of Lavoisier.
The combination of oxygen with the blood by means of respiration, first
discovered as was thought by Lavoisier, is clearly stated by Mayow; who
has also forestalled the elaborate theories of Crawford on animal heat,
of Goodwyn, on muscular stimulus, and of Beddoes on the succedaneum for
respiration in the fœtus.
Boyle, though he must certainly have known of Mayow, neither quotes
him, nor uses, or improves on his experiments; though as I have
already remarked, he seems to have had notions of the atmosphere much
like those adopted by Mayow. Whether this neglect arose from the
pride of birth, or the pride of knowledge, or the pride of age, (for
Boyle was almost twice the age of Mayow) or from jealousy of Mayow’s
abilities, cannot now be ascertained. From that time until Hales
published his statics in 1726, pneumatic experiments were neglected,
and the mathematical philosophy which Newton’s discoveries rendered
fashionable, absorbed for many years the attention of men of Science,
particularly in England. The way in which Lemery, Hales and Brownrigg
speak of Mayow, evidently shews that his theories were not understood,
nor his merits appreciated.
That Mayow was unknown to Black and Cavendish until of late years, is
highly probable at least, if not absolutely certain. Neither these
philosophers, nor Dr. Priestley, could have passed over Mayow’s book,
without being struck with his ideas, and publicly referring to them in
their chemical works.
That Dr. Priestley was unacquainted with Mayow is certain, from the
limited extent of his reading at the early period of his experiments
(from 1770 to 1776 or 1777,) in books of chemistry and theoretic
physiology: from Mayow, not being quoted by any of the writers whose
works Dr. Priestley would be likely to consult except Hales and
Brownrigg, and not by them in a manner to induce any farther curiosity:
from their being unnoticed by Black, Cavendish, Sir John Pringle,
and Lavoisier, in particular: from the custom that Dr. Priestley had
of acknowledging the sources of his ideas in all cases where they
originated from the discoveries of others, as in his references to
Hales, Brownrigg, Cavendish, &c; and from his making no mention of
Mayow in his express account of the labours of his predecessors on the
subject of animal respiration. That both he and Sir John Pringle before
the Royal Society in 1772 and 1776 should expressly treat the _history_
of discoveries in which Mayow bore so distinguished a part, and omit
noticing him altogether, had they known of his works, is incredible. It
is evident that he was then an obscure writer, and not in repute, or
he would have occurred to them; or some of their philosophical friends
would have suggested the propriety of referring to his publications.
Neither is it likely that Scheele would have been acquainted with
Mayow’s writings, though it is singular that he escaped the notice
of Lavoisier who I believe was employed under government in the
collection of essays on the theory and manufacture of saltpetre and
in the superintendance of the saltpetre works, especially as Mayow
was mentioned though disrespectfully by Lemery, in his paper on nitre
before referred to. But there certainly is no evidence that Lavoisier
obtained his ideas of oxygen and its combination with the blood from
Mayow, or his theory of metallic calcination from Jean Rey, though his
obligations to Dr. Priestley have not been always acknowledged with the
candour and liberality that men of science would expect from Lavoisier.
Mayow had more than ordinary discernment in comparing known facts,
and drawing conclusions from them, but he does not appear to have had
the talent of imagining decisive experiments, of varying them, of
observing and noting all the natural phenomena attendant upon them,
or sufficient industry in pursuing them. It is one thing to make
a plausible conjecture, and another to verify it. Those alone are
entitled to the honour of discoveries who not merely start the theory,
but take the pains of pursuing it by experiments and resting it on the
basis of well conceived and accurately ascertained facts, sufficiently
numerous and varied to obviate the most prominent objections. Mayow
has reasoned with great acuteness and conjectured with singular
felicity, but he added little to the mass of philosophical KNOWLEDGE
in his day. He composed and decomposed nitre and ascertained the
existence of vital air in this substance as well as in the atmosphere,
but he did not collect, exhibit, and examine it. He knew how to make
artificial air from nitrous acid and iron, but all the extraordinary
properties of this gas, remained unobserved by him as well as by others
until collected and imprisoned by Dr. Priestley, and exposed to the
question under his scrutinizing eye. Indeed as an experimentalist Dr.
Priestley stands unrivalled. The multiplicity of his experiments,
their ingenuity, their bearings upon the point in question, their
general importance, and their fidelity, were never equalled upon the
whole, before or since. Nor is it any detraction from their merit
with those who are accustomed to experiment, that they hold out no
pretensions to that suspicious accuracy, which has too often depended
more upon arithmetical calculations than upon actual weight and
measure. The many kinds of aeriform fluids discovered by Dr. Priestley,
the many methods of procuring them, the skilfull investigation of
their properties, the foundation he laid for the labours of others,
the simplicity, the novelty, the neatness, and the cheapness of his
apparatus, and his unequalled industry, have deservedly placed him at
the head of pneumatic Chemistry. Nor should it be forgotten that while
he thus outstripped his predecessors and contemporaries in the field
of experiment, it formed not as with them the business of his life,
but (among other branches of literature and philosophy successfully
cultivated) the occupation of his leisure hours, the relaxation from
what he deemed more important, more laborious, and more obligatory
pursuits.
Before his time (excluding Mayow) Boyle had discovered that air
might be generated, fatal to animal life. It was known that common
air would only serve a certain time for the purposes of combustion
and respiration. The mephitic exhalations from natural Grottoes had
been remarked. Inflammable air both natural and artificial had been
exhibited before the royal society. Hales had ascertained the presence
of air in a great number of substances where it was not commonly
suspected though he had not the skill to examine the properties of
the air produced. Black had ascertained the presence of fixed air in
limestone, and Brownrigg, Lane, and Venel had illustrated the theory
of mineral waters. But it was the paper of Cavendish in 1766 on fixed
and inflammable air produced from various substances by means of
acids, fermentation and putrefaction, that first introduced a stile
of experimenting in pneumatic chemistry, more neat, more precise, and
scientific than had hitherto been known.
The attention of Dr. Priestley, however to these subjects was not
originally excited by the works of his predecessors, but by the
_accident_ of his proximity to a brew-house at Leeds, where of course
fixed air (a subject that had attracted much attention about that time)
would be produced in a large way. It was thus that one experiment led
to another, until the fruits of his amusements were the discoveries on
which his philosophical reputation is principally founded. It is no
more than justice to his character to mention in this place, that of
all men living he was the freest from literary deception and the vanity
of authorship. He never claims the merit of profound investigation or
great foresight, for discoveries that might easily have been so stated
as if they had been the pure result of those qualifications, but which
were in reality the offspring of accident and circumstance. He excites
others to patient labour in the field of experiment, from observing
that success does not depend so much on great abilities or extensive
knowledge, as on patient attention, and perseverance; and that much of
his own reputation was owing to the discovery of facts that arose in
the course of his pursuits, the result of no previous theory, unlooked
for and unexpected. In v. 3 p. 282 of his experiments on air he says
“Few persons I believe have met with so much unexpected good success as
myself in the course of my philosophical pursuits. My narrative will
shew that the first hints at least of almost every thing that I have
discovered of much importance have occurred to me in this manner. In
looking for one thing I have general found another, and sometimes a
thing of much more value than that which I was in quest of. But none of
these unexpected discoveries appear to me to have been so extraordinary
as that I am about to relate (viz. the spontaneous emission of
dephlogisticated air from water containing a green vegetating matter)
and it may serve to admonish all persons who are engaged in similar
pursuits, not to overlook any circumstance relating to an experiment,
but to keep their eyes open to every new appearance and to give due
attention to it however inconsiderable it may seem.”[49] To this
candour of disposition, and the readiness with which he acknowledged
his mistakes and his oversights, even those who opposed his opinions
bear honourable testimony. “The celebrated Priestley himself (says M.
Berthollet in his reply to Kirwan on Phlogiston p. 124 of the Eng.
translation) often sets us the example, by rectifying the results of
some of his numerous experiments.”
[49] See also the 1st, vol. of his early edition of experiments on air
p. 29.
Numerous indeed those experiments were as well as important: far too
numerous to be particularised here; though it may not be improper to
call to the recollection of the reader some of the more interesting
facts which we owe to Dr. Priestley, and the times of their discovery
and communication.
The first of his _publications_ on pneumatic chemistry was in 1772,
announcing the method of impregnating water with fixed air, and on
the preparation and medicinal uses of artificial mineral waters; a
discovery that domesticated much of the knowledge that had heretofore
been disclosed only in the works of learned societies; and that
beautifully exemplified how much of the health and the pleasure of
common life, might depend on the ingenious researches of men of
science. Though this was the first publication of Dr. Priestley on
the chemistry of the airs, he had certainly commenced his experiments
in this branch of Science, soon after his arrival at Leeds, and as
early at least, as 1768. In the year 1771 he had already procured good
air from saltpetre; he had ascertained the use of agitation, and of
vegitation as the means employed by nature in purifying the atmosphere
destined to the support of animal life, and that air vitiated by animal
respiration was a pabulum to vegetable life; he had procured factitious
air in a much greater variety of ways than had been known before, and
he had been in the habit of substituting quicksilver in lieu of water,
for the purpose of many of his experiments. In his paper before the
Royal Society, in the spring of 1772, which deservedly obtained him the
honour of the Copley Medal, he gives an account of these discoveries.
In the same paper he announces the discovery of that singular fluid
nitrous air,[50] and its beautiful application as a test of the purity
or fitness for respiration of airs generally. In the same paper he
shews the use of a burning lens in pneumatic experiments, he relates
the discovery and properties of marine acid air; he adds much to
the little of what had been heretofore known of the airs generated
by putrefactive processes, and by vegetable fermentations, and he
determines many facts relating to the diminution and deterioration of
air, by the combustion of Charcoal, and the calcination of metals.
[50] Honestly referring to Dr. Hales and Mr. Cavendish for any idea that
might have remotely led to this discovery (See Obs. on air 1st ed. v. 1
p. 108) the discovery however was completely his own.
Dr. Priestley seems always to have thought nitrous air as convenient
a substance for eudiometrical experiments as any of the later
substitutes, viz. the liquid sulphurets and the combustion of
phosphorus. The foundation of Mr. Davy’s substitute, muriat or sulphat
of iron saturated with nitrous air, was as Mr. Davy acknowledges first
discovered by Dr. Priestley himself. See Nich. Journ. for Jan. 1802
p. 41. The different states of the solutions of iron in vitriolic
acid have been ingeniously applied to the analysis of mixed gasses by
Humboldt and Vauquelin.
Soon after this, in confirmation of Sir John Pringle’s theory of
intermittents and low fevers being generally owing to moist miasma
when people are exposed to its influence, he ascertained by means of
his nitrous test that the air of marshes was inferior in purity to the
common air of the atmosphere.[51]
He had obtained very good air from saltpetre in 1771, but his full
discovery of dephlogisticated air, seems not to have been made until
June or July, 1774,[52] when he procured it from precipitate per se,
and from red lead. This was publicly mentioned by him at the table
of Mr. and Madame Lavoisier, at Paris, in October 1774, to whom the
phenomena were until then unknown. The experiments on the production of
dephlogisticated air, he made before the scientific chemists at Paris
about the same time, at Mr. Trudaine’s. This hitherto secret source
of animal life and animal heat, of which Mayow had but a faint and
conjectural glimpse, was certainly first exhibited by Dr. Priestley,
and about the same time, (unknown to each other) by Mr. Scheele of
Sweden. For the honour of science, it were much to be wished that the
pretensions of Mr. Lavoisier were equally well founded. He has done
sufficient and been praised sufficiently for what he has done, to
satisfy a mind the most avaricious of fame; he is deservedly placed
in the first rank among the philosophers of his day, and he ought not
to have thrown a shade over his well earned reputation, by claiming
for himself the honour of those discoveries which he had learned from
another.
[51] Phil. trans. v. 54 p. 92.
[52] See Doctrine of Phlog. established p. 119.
From this brief account of the first stage of Dr. Priestley’s chemical
labours, it appears that during the short period of two years, he
announced to the world more facts of real importance, and extensive
application, and more enlarged and extensive views of the œconomy of
nature, than all his predecessors in pneumatic Chemistry had made known
before.
In 1776 his observations on respiration were read before the Royal
Society; in which he clearly discovered that the common air inspired,
was diminished in quantity, and deteriorated in quality, by the action
of the blood on it _through the blood vessels of the lungs_; and that
the florid red colour of arterial blood, was communicated by the
contact of air through the containing vessels. His experiments on the
change of colour in blood confined in a bladder, took away all doubt
of the probability of this mode of action. I cannot help thinking
that the circumstance of Dr. Priestley’s mind being so much occupied
with the prevailing theory of Phlogiston, was the reason why he did
not observe that the diminution of the air, and the florid colour of
the arterial blood was owing to the absorption of the pure part of the
atmosphere, _rather_ than to any thing emitted from the blood itself.
This part of the theory of respiration Mr. Lavoisier has certainly
established; though it is by no means ascertained as yet whether the
vital part of the atmosphere inspired, is wholly and alone absorbed,
or whether in reality something is not contributed in the lungs to the
formation of the fixed air found after expiration.[53]
[53] That azote is absorbed during respiration as Dr. Priestley supposed
contrary to Mr. Lavoisier’s opinion, is made extremely probable by the
experiments of Mr. Davy, whose accuracy is well known. Researches,
p. 434. The formation of water in this process, is certainly no more
than conjecture as yet. Dr. Bostock has lately published a very useful
and laborious history of discoveries relating to respiration, both
anatomical and pneumatical.
In 1778 Dr. Priestley pursued his experiments on the property of
vegetables growing in the light to correct impure air, and the use
of vegetation in this part of the œconomy of nature. A discovery
which was announced to several men of science in England previous
to the publication of the same ideas by Dr. Ingenhouz.[54] Indeed
from its having been communicated to M. Magellan whose pleasure
and whose occupation it was, to give information of new facts to
his philosophical correspondents, and of this in particular to Dr.
Ingenhouz then engaged in similar researches, there is hardly a doubt
but the latter knew of the experiments then pending on the subject by
Dr. Priestley.
[54] Doctrine of Phlogiston established, p. 107, et. seq. The theory
of the amelioration of impure air by the absorption and excretion of
vegetables growing in the light, has been doubted by Dr. Darwin in his
Phytologia, and opposed by Count Rumford in a paper published in the
transactions of the Royal Society, for 1787: also by Dr. Woodhouse of
Philadelphia, Nicholson’s Journal, for July 1802, and by Mr. Robert
Harrup, Nicholson’s Journal, for July 1803.
It is painful to notice these aberrations from propriety in the conduct
of men highly respectable in the philosophical world, arising from an
over anxious avarice of literary fame, and an improper jealousy of
the reputation of another. Not that it derogates from the character
of a philosopher to wish for the applause of those who know how to
appreciate his merit, or who are benefited by his exertions; such
an anxiety is laudable when it does not lead to encroachments on
the literary rights of others; nor is it at all desireable under
the present circumstances of human nature, to expect from men of
science an attention to their pursuits arising from motives of pure
benevolence alone, and excluding all views, hopes, and expectations of
the gratifying tribute of public approbation. I believe no man ever
laboured with a more single eye to public utility than Dr. Priestley.
But consideration in society, and the respectability attendant upon
great talents, and great industry, successfully employed for the
benefit of mankind, is a motive to useful exertion so universal, so
honest, so laudable, and withal so powerful, that it is the common
interest, as well as the duty of society, to bestow it liberally where
it has been earned faithfully, and to concede it to those only, who
have really deserved this honourable reward.
From this period Dr. Priestley seems to have attended to his pneumatic
experiments as an occupation; devoting to them a regular portion of
his time. To this attention, among a prodigious variety of facts
tending to shew the various substances from which the gasses may be
procured; the methods of producing them; their influence on each other,
and their probable composition, we owe the discovery of vitriolic
acid air, of fluor acid air, of vegetable acid air, of alkaline air,
and of dephlogisticated nitrous air, or gazeous oxide of azote as
it has been called, the subject of so many curious experiments by
Mr. Davy. To these we may add the production of the various kinds of
inflammable air by numerous processes that had escaped the observation
of Mr. Cavendish; in particular the formation of it by the electric
spark taken in oils, in spirits of wine and in alkaline air; the
method of procuring it by passing steam through hot iron filings,
and the phenomena of that hitherto undetermined substance the finery
cinder, and its alliance to steel. To Dr. Priestley we owe the very
fine experiment of reviving metallic calces in inflammable air and
its absorption in toto, apparently at least, undecomposed. He first
ascertained the necessity of water to the formation of the gasses, and
the endless production of air from water itself.
Dr. Priestley’s experiments on this subject, to wit: the generation
of air from water, opened a new field for reflection, and deserves
more minute notice. No theory has yet been proposed adequate to the
explanation of the facts. He had before remarked that water was
necessary to the generation of every species of air, but the unceasing
product of air from water had never been before observed.
In his first set of experiments he procured air, by converting the
whole of a quantity of water into steam: then, to obviate the objection
to the water having imbibed air from the atmosphere he put the water
on mercury in long glass tubes immersed in mercury: in a third process
he used no heat, but merely took off the pressure of the atmosphere.
In all these cases a bubble of air was extricated from the water,
which being separated by inclining the tube, another bubble was again
produced on each repetition of the experiment. That this could not be
air imbibed from the atmosphere appeared from this, that though the
first portions were generally purer than atmospheric air, the next
became less pure, and at length wholly phlogisticated.
It did not appear that the addition of acids, enabled the water to
yield more air, nor did he succeed in attempting to convert the whole
of a given quantity of water into air, although exposing the water
confined over mercury to heat, and separating the air produced, it
still continued to produce more air for twenty or thirty repetitions
of the experiments. When a certain proportion of air was thus produced
at any one time, no continuance of the experiment would encrease the
quantity until it was separated. Hence he concludes that the longest
continuance of water in the state of vapour would not convert it
into air. The water used was pure distilled water previously boiled to
separate any adventitious air that might have been imbibed from the
atmosphere. The precautions he used, and the replies to such objections
as he foresaw the experiment would be liable to, are detailed in
the papers he published on the subject, to wit, a separate pamphlet
published in England in 1793, and a communication in the Am. Ph. trans,
v. IV. p. 11-20.
In the last mentioned paper, he proceeds also to give an account of
some experiments on the property of water to imbibe different kinds of
air, and the conversion of sp. of wine, into inflammable air.
This paper inserted in the American transactions, was read before that
society in Feb. 1796. In Ap. 1800 another paper was read before the
same society on the production of air by the freezing of water Am. Ph.
trans. v. V. p. 36. In this paper he recapitulates the general result
of his former experiments on the generation of air from water, namely
“that after all air had been extracted from any quantity of water by
heat or by taking off the pressure of the atmosphere, whenever any
portion of it was converted into vapour, a bubble of permanent air
was formed, and this was always phlogisticated. The process with the
Torricellian vacuum (he says) I continued for some years and found the
production of air equable to the last. The necessary inference from
this experiment is, that water is convertible into phlogisticated air,
or that it contains more of this air intimately combined with it than
can be extricated from these processes in any reasonable time.”
He proceeds to state his imperfect attempts to procure air from water
by freezing, until he procured cylindrical iron vessels seven or eight
inches high and near three inches wide at the bottom, the upper orifice
closed with a cork and cement, in the centre of which was a glass tube
about one fifteenth of an inch in diameter. In this apparatus the water
in the iron vessel was frozen by means of snow and salt, the vessel
being immersed in mercury, and the water contained over the mercury.
The quantity of water was about three ounces. The experiment was
repeated nine times without changing the water, and the last portion of
air procured in this manner was as great as any of the preceding; so
that there remained no reasonable doubt but that air might be produced
from the same water in this manner ad libitum. Having obtained near
two inches of air in the glass tube, Dr. Priestley put an end to the
experiment, and examining the air found it wholly phlogisticated, not
being affected by nitrous air, and having nothing inflammable in it.
The inference drawn by the Doctor from those experiments is, that
water when reduced by _any means_ into the state of vapour, is in part
converted into phlogisticated air; and this is one of the methods
provided by nature for keeping up the equilibrium of the atmosphere,
as the influence of light on growing vegetables is the means of
recruiting the other part; both of them being subject to absorption
and diminution in several natural processes. And he thinks that they
strengthen also the opinion, that water is the basis of every kind
of air, instead of being itself a compound of hydrogen and oxygen
according to the new theory. At all events the experiments themselves
must be considered as extremely curious, as well as new.
The water and the salt thus made use of gave rise to another experiment
of the most important nature to the present theory of chemistry, if it
should on future repetition be ultimately verified. This experiment
related by Dr. Priestley in a letter to Dr. Wiston is in substance
as follows. Having repeatedly used as above mentioned a freezing
mixture of common salt and snow, the experiment being finished, he
evaporated the snow water in an iron vessel and recovered the salt.
The salt thus recovered contained some calx of iron. He put it by in
a bottle and labelled it, according to his usual practice. In October
1803, he wanted to procure some marine acid, and took the salt thus
procured by evaporating the snow water, for the purpose. On commencing
the distillation, he was surprized to find the receiver full of the
characteristic red fumes of the nitrous acid. The vitriolic acid used
for the purpose was diluted with about an equal quantity of water. On
finishing the process, he took some of the acid in the receiver, and
dissolved copper in it, and thus procured good nitrous air. He was
himself perfectly persuaded that no nitre had been used in the freezing
mixture, nor had any by accident or design been mixed with the salt.
He was not unacquainted with the common mode of clearing black oil of
vitriol by the addition of nitre. So that no means of accounting for
this curious fact remained, but the snow or the iron: he seemed to
think that should this experiment be fully verified hereafter, it would
confirm the vulgar hypothesis of snow containing nitre, and account
for the fertilizing quality usually attributed to snow. He had no
opportunity in that winter of repeating the experiment as he died in
about three months after, and his previous illness had compelled him to
forsake his laboratory.
Of the almost discarded theory of Phlogiston Dr. Priestley to his death
remained the strenuous advocate, and almost the sole supporter; _ipse
Agmen_. Beautiful and elegant as the simplicity of the new doctrine
appears, many facts yet remain to be explained, to which the old
system will apply, and the French theory is inadequate. These are
collected with an ingenuity of arrangement, and a force of reasoning in
the last pamphlet published by the Doctor on the subject,[55] which no
man as yet unprejudiced can peruse, without hesitating on the truth of
the fashionable theory of the day.
[55] The doctrine of phlogiston established 1803.
Certainly, it has not yet been sufficiently explained on the new
theory, what becomes of the Oxygen from the decomposed water in the
solution of metals in acids; nor why inflammable air is produced
when one metal in solution is precipitated by another; nor why
dephlogisticated air is hardly to be procured from finery cinder, if at
all; nor why this substance so abounding in oxygen according to the new
theory, will not oxygenate the muriatic acid; nor why it should answer
all the purposes of water in the production of inflammable air from
charcoal; nor why water in abundance should be produced when finery
cinder is heated in inflammable air, and none when red precipitate is
exposed to the same process; nor what becomes of the oxygen of the
decomposed water when steam is sent over red hot Zinc, and inflammable
air is produced without any addition in weight to the Zinc employed;
nor why there should be a copious production of inflammable air when
hot filings of Zinc are added to hot mercury in a hot retort and
exposed to a common furnace heat, which I believe is an unreported
experiment of Mr. Kirwan’s; nor why sulphur and phosphorus are formed
by heating their acids in inflammable air without our being able to
detect the oxygen which on the new theory ought to be separated, nor
why water should be produced by the combustion of inflammable air
with ,47 of oxygen, and nitrous acid when ,51 of oxygen is employed,
for this experiment can now no more be doubted than explained; nor
why on the new doctrine the addition of phlogisticated air, should
make no alteration in the quantity of acid thus obtained; nor why red
hot charcoal slowly supplied with steam, should furnish inflammable
air only and not fixed or carbonic acid air; nor why nothing but pure
fixed air should be produced by heating the carbonated Barytes in the
same way; nor why fixed air should be formed under circumstances when
it cannot be pretended that Carbon is present, as when gold, silver,
platina, copper, lead, tin and bismuth are heated by a lens in common
air over lime water; or why the grey and yellow calces of lead should
furnish carbonic acid and azote, and no oxygen; nor why the residuum
of red lead when all its oxygen is driven off by heat should be either
massicot or glass of lead according to the degree of heat, and not
lead in its metalline state; nor why plumbago with steam should yield
inflammable and not fixed air; nor why minium and precipitate per se
heated in inflammable air should produce fixed air; nor why on the
evaporation of a diamond in oxygen, the fixed air produced should far
exceed the weight of the diamond employed, if some of the oxygen had
not entered into the composition of the carbonic acid so formed; nor
why there should be a constant residuum of phlogisticated air (or
azote) after the firing of dephlogisticated and inflammable airs, if it
be not formed in the process; nor why phlogisticated air if a simple
substance, should be so evidently formed in the various processes
enumerated by Dr. Priestley in the 13th section of the pamphlet of
which I have made the foregoing abstract? whether the doctrine of
phlogiston is still to be used as the key to the gate of chemical
theory, or whether it be properly thrown aside for the elegant
substitute of the French chemists, can hardly be ascertained, until the
preceding difficulties are cleared up on the new doctrine, for on the
old theory they are sufficiently explicable. The summary of arguments
in favour of Phlogiston, published by Dr. Priestley, in 1803, are
evidently too important, and too difficult of reply, to be slighted by
those who adopt the opposite opinions. _Non nostri est tantas componere
lites._ Should the old theory ultimately fall, it maybe fairly said of
its respectable supporter, _si Pergama dextra defendi potuit, etiam hac
defensa fuisset_.
This was almost the last of Dr. Priestley’s chemical publications,[56]
through all which, his characteristic talent as an author has been
eminently preserved, that of not only adding greatly to the existing
stock of knowledge, but exciting others to exertion and reflection in
the same line of pursuit. Nor can I help thinking that much of the
labours of the French philosophers in this department of science would
never have been undertaken, if they had not been called forth by the
previous discoveries, not of Lemery, Margraaf, Bayen, Macquer, and
Beaumè, but of Hales, Black, and Macbride; of Cavendish and Priestley
and Scheele.[57] Would to God there were no other object of contest
between the rival nations of Great Britain and France, but which should
add most to the sum of human knowledge, and contribute most to the
means of human happiness.
[56] To the end of this Appendix will be subjoined a list of the
scattered papers on Philosophical subjects which Dr. Priestley
published in periodical collections, besides those which are inserted
in the Philosophical transactions.
[57] I do not mean to deny the tribute of praise to Marriotte and Venel,
any more than to Brownrigg and Lane, and it is certain that Lavoisier
was engaged in pneumatic experiments, previous to 1774.
It is impossible to conclude the preceding account better than by the
following extract of a letter to Mr. Lindsey from a man[58] well able
to appreciate the labours of Dr. Priestley; and the late testimony in
favour of his discernment by Dr. Bostock. “To enumerate Dr. Priestley’s
discoveries, would in fact be to enter into a detail of most of those
that have been made within the last 15 years. How many invisible fluids
whose existence evaded the sagacity of foregoing ages has he made
known to us? The very air we breathe, he has taught us to analyze,
to examine, to improve: a substance so little known, that even the
precise effect of respiration was an enigma until he explained it.
He first made known to us the proper food of vegetables, and in what
the difference between these and animal substances consisted. To him
Pharmacy is indebted for the method of making artificial mineral
waters, as well as for a shorter method of preparing other medicines;
metallurgy for more powerful and cheap solvents; and chemistry for such
a variety of discoveries as it would be tedious to recite: discoveries
which have new modelled that science, and drawn to it and to this
country, the attention of all Europe. It is certain that since the year
1773, the eye and regards of all the learned bodies in Europe have been
directed to this country by his means. In every philosophical treatise,
his name is to be found, and in almost every page. They all own that
most of their discoveries are due either to the repetition of his
discoveries, or to the hints scattered through his works.”[59]
[58] Richard Kirwan, Esqr.
[59] Vindiciæ Priestlianæ, p. 68.
“This is not the only instance” (says Dr. Bostock,[60] speaking of Mr.
Jurin’s opinion that azote was generated, instead of being absorbed,
in the process of respiration as Dr. Priestley, and after him Mr. Davy
had supposed,) “in which, after the conclusions of Dr. Priestley have
been controverted by his contemporaries, a more accurate investigation
of the question, has ultimately decided in his favour. The complicated
apparatus, and imposing air of minuteness which characterize the
operations of the French chemists, irresistibly engage the assent of
the reader, and scarcely permit him to examine the stability of the
foundation upon which the structure is erected. The simplicity of the
processes employed by Dr. Priestley, the apparent ease with which his
experiments were performed, and the unaffected conversational stile
in which they are related have, on the contrary been mistaken for the
effects of haste and inaccuracy. Something must also be ascribed to the
theoretical language which pervades, and obscures the chemical writings
of this Philosopher, in consequence of his unfortunate attachment to
the doctrine of Phlogiston.”
[60] Essay on respiration, p. 208.
When the operose experiment of the French chemists on the formation
of water, shall have been sufficiently repeated, and verified by
other experiments to the same point, less complex, less tedious, less
expensive, and easy to be repeated; when the water thus supposed to
be formed is sufficiently distinguished from the water absolutely
necessary to the generation of all airs, and attendant upon them[61]
both in a state of mixture and combination; and when the difficulties
enumerated a page or two back, as attendant on the modern theory shall
be explained on the new system, as well as on that of Stahl, then, and
not until then, will it be time to lament Dr. Priestley’s unfortunate
attachment to the doctrine of Phlogiston.
[61] Mr. Kirwan found that common inflammable air from iron, and
vitriolic-acid, contained about 2-3 of its weight of water mixed with
it; which might be separated from the air by means of concentrated
vitriolic-acid in a watch glass over mercury, without diminishing the
quantity or altering the characteristic properties of the air thus
treated.
_Of Dr. Priestley’s other Scientific Works._
The other philosophical labours of Dr. Priestley consist of his history
of electricity, his history of the discoveries relating to light and
colour, and his popular introductions to perspective, electricity and
natural philosophy.
It appears that after the publication of his history of electricity,
he intended to have pursued the plan, by composing similar histories
of every branch of science: a magnificent idea, and which none but
a man conscious of uncommon powers could have contemplated. Few men
indeed were so capable of such an undertaking as Dr. Priestley; for
independant of his habits of patient and regular industry in his
literary pursuits, and the wide field of his attention to scientific
objects, he had a facility of perusing, abstracting, and arranging the
works of others, not commonly attendant even upon equal abilities in
other respects. This great undertaking of Dr. Priestley to embrace
the various departments of philosophy, appears a labour sufficient
for one life; and had due encouragement been afforded, this projected
series of histories would in all probability have been compleated,
usefully to the world, and reputably to himself. But he proposed this
undertaking laborious as it was, without designing that it should
occupy the whole or the principal portion of his time, but his leisure
hours only; for at no period did he postpone his professional duties,
or his theological studies, to any other object whatever. The life of
Dr. Priestley is almost a perpetual illustration of a seeming paradox,
respecting mental energy, that men of talents, uncommonly laborious,
and who appear to get through more business than one person could be
supposed equal to, have usually more leisure time at their disposal,
than those who have little to do: so much does the habit encrease
the power of exertion. Nor was any man less averse to the innocent
pleasures of social enjoyment than Dr. Priestley, or better calculated
as well as more inclined to contribute to the common stock of amusing,
and instructive conversation. It cannot indeed be truly said of him,
as Dr. Johnson[62] once related of himself, that he had never refused an
invitation to dinner on account of business but once in his life, yet
no man more readily found leisure for social intercourse. This arose
from his habit of dividing his time into certain portions appropriated
to his respective pursuits, and determining to perform a certain
quantity of literary duty, within the assigned period.
[62] On that day, (Dr. Johnson said) as it was an unusual deprivation,
he found himself disinclined, and unable to attend steadily to the work
that led him to refuse the invitation. He walked about his library
occasionally looking over first one book and then another until about
four o’clock when weary of staying within he went to a tavern to dine.
Dr. Johnson had for a long time a dislike to Dr. Priestley who bore two
of the characters most in disrepute with Dr. Johnson, that of a whig
and a dissenter. Dr. Priestley’s pursuits also consisting so largely
of heterodox theology, which Dr. Johnson abominated, and experimental
philosophy which he heartily despised, they had hardly a common point
of union. Toward the latter part of Johnson’s life, they met; and upon
the friendly terms that ought to obtain between two men, who, each in
their way, deserved so well of the republic of letters.
The first edition of his history of Electricity, was in 1767: it
went through another edition in 1769, and a third in 1775. It was
published at a very happy time, when electricity was a favourite object
of attention to many respectable men of science then living, and it
contributed in a great degree to turn the public attention toward
the study of these phenomena. Very much of what has been done since
may be fairly attributed to the popularity given to this branch of
experimental philosophy by Dr. Priestley. Nor did he confine himself to
a mere narration of the labours of others; the second volume contains
many new experiments of his own, and some of them form very curious
and important additions to the stock of electrical knowledge.[63]
The discoveries of the last thirty years, particularly including
those of Galvanic Electricity, are so numerous, and so dispersed in
volumes difficult to be procured, that a continuation of this history
is a desideratum in the scientific world; at one time there was an
expectation of seeing it from the pen of Mr. Nicholson, whose general
knowledge, and industry, as well as his attention to this branch of
philosophy in particular, render him peculiarly qualified for the task.
But the proposals he communicated to Dr. Priestley, on the subject,
were not pursued to effect.[64]
[63] Dr. Priestley among his other experiments on electricity first
ascertained the conducting power of charcoal and the calcination and
vitrification even of the most perfect metals by the electric spark. He
seems first to have used large batteries, which M. Van Marum and his
associates have carried to such extent.
The solutions of the metals, the gasses produced and the circumstances
which accelerate and prevent these effects in Galvanic processes with
the pile of Volta, as detailed by Dr. Priestley in his paper on this
subject in Nich. Journ. for March 1802 p. 198 form very important
additions to the mass of knowledge respecting the Galvanic fluid. Nor
are his discoveries in pneumatic electricity, of the conversion of
oils, spirit of wine and the alkaline gass into inflammable air or
hydrogen of less moment.
[64] Dr. Bostock, who seems to have many requisites to qualify him as
the historian of particular branches of science, has published a good
attempt toward the history of Galvanism in Nicholson’s Journal.
These histories of detached branches of Science, would not only be
highly useful, but they may be considered as in some measure necessary
to the accurate pursuit, and advancement of science itself. They are
not only useful for the purpose of shewing the discoveries that have
been made, and the time of their publication, the ideas that appear to
have suggested them, the persons to whom we are indebted for them, and
their effect on the spirit of enquiry at the time, but they prevent a
man of science from being led into mistakes, from doing what has been
already done, from suggesting what has been already published, and
from ignorantly claiming to himself the merit due to the labours of
a predecessor. Books are now so multiplied, in languages so various,
obtained with so much difficulty, and at an expence so far exceeding
the usual means of scientific men, that those who like Dr. Priestley
fully and faithfully execute a work of this description are real
benefactors to mankind.[65]
[65] The transactions of the various academies and philosophical
societies in Europe amount at least to 1000 volumes in quarto. The
royal society of England in 1665 led the way to similar institutions.
The history of ELECTRICITY was composed by Dr. Priestley in one year.
The three editions of the work in less than eight or nine years
sufficiently shew that, in the opinion of men of science, it was well
composed: otherwise the celerity of its composition, would no doubt
derogate from, instead of adding to, the well earned reputation of
the author; and rather tend to shew that he was too careless or too
conceited to take the necessary pains and employ the necessary time to
make it fit for public inspection. Every man owes to the public, that
if he professes to instruct them, he should dedicate as much labour as
the subject demands, or at least as much time as it is in his power to
devote to it. I fully accede to the ingenious correction of the _nonum
prematur in Annum_, suggested by the witty Dr. Byrom of Manchester; but
something of the _Limæ Labor_, respect for the tribunal of the public
demands of every man who appears before them in the character of an
author. Dr. Priestley has in more instances than one, been accused of
unnecessary if not of culpable rapidity in his literary compositions:
but he never professed to be a fine writer; he never sought after the
beauties of stile; and his common language was sufficiently neat and
expressive, to communicate the facts and the arguments upon which
it was employed. It is also to be remarked, that the facility of
composition which he acquired from long practice, made that labour
light to him, which would have been too much for a less skilful and
a less experienced composer. In many instances indeed of his rapid
publications, he had not to _seek_ for arguments, but to express in his
unornamented and unaffected manner, the ideas that forced themselves
upon him relating to a subject previously considered and upon which he
had long made up his mind.
The History of Discoveries respecting LIGHT and COLOURS published
in 1772 was a more difficult task, nor did it meet with equal
encouragement. Sir Isaac Newton’s important labours in this branch
of science, could not be fully comprehended without a portion of
mathematical knowledge not even then so common as formerly, among
the philosophers of the day. Mathematical studies seem to have in
themselves very little to interest, compared with other literary
pursuits; although by long attention and habit, that interest may be
excited and kept up. It was about this time that the popular phenomena
of chemistry and electricity more decidedly took their stand in the
field of science, and irresistably seized hold on the attention of the
world: phenomena, highly amusing in themselves, strongly attractive
from their novelty, of evident and immediate application, and that
promised an incalculable harvest of honourable and useful discovery,
to such as would become their votaries. Little had been done in this
department of philosophy, little previous knowledge was required to
comprehend all that was known, and those who were unable to read a
page of Sir Isaac Newton with profit, could easily mix an acid and an
alkali, or turn the wheel of an electrical apparatus.
By this time too, it had been discovered, that there were other powers
in nature that must be called in to explain appearances, which the
mechanical and corpuscular philosophy had endeavoured to elucidate in
vain. Such were magnetism, electricity and chemistry. It began to be
found out, that the science of calculation, was but an aukward handmaid
to their sister branches of natural philosophy, while physiology,
laughed outright at the clumsy addresses of her mathematical admirers,
from Borelli to Keill.
The discoveries therefore relating to light and colours, at the time
when Dr. Priestley proposed his history, being intimately associated
with the study of the mathematics, and the profound investigations
of Sir Isaac Newton, were out of the beat of the less laborious, but
more fashionable philosophy of the day; and were not so generally
interesting to the Sciolists and Amateurs. Hence the work in question,
though treated in a very entertaining and popular manner, and by no
means crouded with reference to Diagrams or abstruse discussions, was
not popular even among that class of readers, who might reasonably be
calculated on, as the purchasers of such a performance. The subscribers
indeed were sufficiently numerous, and respectable, but by far the
majority were defaulters in respect of payment. It did not pay the
bookseller: and of course still less did it recompence Dr. Priestley in
a pecuniary point of view, especially as he had gone to considerable
expence with a view to the completion of his extended plan. To him
indeed, though pecuniary loss was a serious evil, pecuniary profit
was a consideration of small importance: his motives to literary
labour seem uniformly to have arranged themselves as follows, utility,
reputation, profit.
The work in question is certainly too brief, considering the importance
of the subject: many parts of it, the theory of Huygens, Euler, and
Franklin for instance, seem to have merited more discussion. That all
the phenomena of light depend on the Sun, as the reservoir, whence all
the emanations of that fluid to the various parts of the system are
supplied, the lighting of a candle is alone sufficient to refute. The
facts discovered to us by modern Chemistry will suggest a great many
other doubts of the doctrines respecting light, which were regarded
as well established when Dr. Priestley’s book was written. But it was
a faithful account of the knowledge of the day, and an unprejudiced
tribute to the reputation of those philosophers who had from time to
time extended the boundaries of science on the subjects treated of.
Not a little has been added to the mass of facts then published, by
the subsequent experiments of Dr. Priestley himself, and his fellow
labourers in the Chemistry of the Gasses: and notwithstanding the
experiments of Sir Isaac Newton and his predecessors, the theory of
light and colours is not yet rested upon facts sufficiently numerous,
and decisive to satisfy the enquiries dictated by the present state of
knowledge.
But with all these disadvantages, the work has nevertheless maintained
its ground, for we have no where else so systematic, and compleat,
though brief an account of what had been made known to the world on
this important branch of scientific inquiry. It will always remain a
valuable performance; and to the author an honourable one, from the
knowledge and ability required in its compilation, from the fairness
of the account it gives, and the entertaining statement of facts and
suggestions interspersed through the book.
It is greatly indeed to be wished, that these histories should be
continued on the plan which Dr. Priestley has adopted. So that all the
prominent facts should be collected in the order of their discovery,
and a full view be given of the ground already gone over. Abridgments,
do not answer this purpose; the theories that dictated the experiments
are not detailed, their truth or their fallacy cannot be judged of, and
sufficient merit is not attributed to the labours of the discoverer,
or the bearings of his facts on his theory, sufficiently explained. To
attain gradually to the summit of the temple of science, we must not
only build on the foundations of our predecessors, but know somewhat of
their intentions at the time of laying them.
The minor treatises of Dr. Priestley on electricity, perspective and
natural philosophy, have this discrimination of character, that they
are more calculated to allure young people to the study of those
subjects than almost any of the introductions which have either
preceded or succeeded. Philosophy is made, not an abstruse science, but
a delightful amusement. Indeed it was the fort of Dr. Priestley to make
knowledge intelligible and popular, and treat it in such a way, as to
invite rather than deter, those who were inclined to enter upon these
delightful pursuits. The plainness and simplicity of his syllabus,
the amusing complexion of the Phenomena, by which he illustrates his
doctrines, and the facility with which the one can be made, and the
other comprehended, affords a very useful example to those who may have
the same object hereafter in view. This was doubtless, owing to his
long experience as a teacher: and his success in that capacity among
his pupils, with the electrical machine, and the air pump, is full
evidence of the practical utility of his plans of instruction.
_Catalogue of Dr. Priestley’s smaller pamphlets and uncollected papers
on philosophical subjects._
_Nicholson’s_ }
_Journal._ }
_new series._ }
V. 1 p. 181. Reply to Mr. Cruikshank’s.
Ibid 198. Experiments on the Pile of Volta.
V. 2 p. 233. On the conversion of iron into steel.
V. 3 p. 52. On air from finery cinder and charcoal.
V. 4 p. 65. Farther reply to Mr. Cruikshank’s.
_Amer. Trans._
V. 4 p. 1. Experiments and observations relating
to the analysis of atmospherical
air.
V. 4 p. 11. Farther experiments relating to the
generation of air from water.
Ibid p. 382. Appendix to the above articles.
_Ib. Vol._ V. {p. 1. Experiments on the transmission
{ of acids and other liquors in the
{ form of vapours over several substances
{ in a hot earthen tube.
Republished {
{p. 14. Experiments on the change of
{ place in different kinds of air
{ through several interposing substances.
{ 21. Experiments relating to the absorption
{ of air by water.
{
{ 28. Miscellaneous experiments relating
{ to the doctrine of phlogiston.
together. {
{ 36. Experiments on the production of
{ air by the freezing of water.
{
{ 42. Experiments on air exposed to
{ heat in metallic tubes.
_New-York Med. Repos._ _Title and Date._
Vol. 1 p. 221. Considerations on the doctrine of
Phlog. and the Decomp. of water.
(Pamphlet) 1796.
Ibid p. 541. Part 2d of do. (Pamphlet 1797.)
Vol. 2 p. 48. (Pamphlet) to Dr. Mitchell.
Ibid p. 163. (Pamphlet) on Red Precipitate of
Mercury as favourable to the doctrine
of Phlogiston, July 20, 1798.
Ibid p. 263. Experiments relating to the calces of
metals communicated in a fifth letter
to Dr. Mitchell. October 11,
1798. (Pamphlet.)
Ibid p. 269. Of some experiments made with
ivory black and also with diamonds.
(Pamphlet) 11 October, 1798.
Ibid p. 383. On the phlogistic theory, January 17,
1799. (Pamphlet.)
Ibid p. 388. On the same subject. February 1,
1799.
Vol. 3 p. 116. A reply to his antiphlogistian opponents,
No. 1.
Vol. 4 p. 17. Experiments on the production of
air by the freezing of water.
Ibid p. 135. Experiments on heating Manganese
in inflammable air.
Ibid p. 247. Some observations relating to the
sense of hearing.
Vol. 5 p. 32. Remarks on the work entitled “A
brief history of epidemic and pestilential
diseases,” May 4, 1801.
Ibid p. 125. Some thoughts concerning dreams.
Ibid p. 264. Miscellaneous observations relating
to the doctrine of air, July 30,
1801.
Ibid p. 390. A reply to Mr. Cruikshank’s observations
in defence of the new system
of chemistry, 5 Vol. Nicholson’s
Journal p. 1, &c.
Vol. 6 p. 24. Remarks on Mr. Cruikshank’s experiments
upon finery cinder and
charcoal.
Ibid p. 158. Observations on the conversion of
iron into steel.
Ibid p. 271. Additional remarks on Mr. Cruikshank’s
experiments on finery cinder
and charcoal, November 15
1802.