Chapter II (1)

Cursory thoughts on the advantages of Biography.--Plan
and objects of the Pneumatic Institution.--Davy contracts
friendships during his residence at Bristol.--His first visit
to London.--His Letters to Mr. Davies Gilbert.--The publication
of the West Country Contributions, by Dr. Beddoes.--Davy's
Essays on Heat, Light, and Respiration.--His interesting
experiments on bonnet canes.--He commences an enquiry into
the nature of nitrous oxyd.--He publishes his chemical
researches.--A critical examination of the work.--Testimony of
Tobin, Clayfield, Southey, and others, respecting the powers
of nitrous oxyd.--Davy breathes carburetted hydrogen gas, and
nearly perishes from its effects.--His new Galvanic experiments
communicated in a Letter to Mr. Gilbert.

Having concluded the early history of the subject of these memoirs, and conducted it to that memorable day on which he left his native town, and bursting from obscurity, prepared to enter upon a wider field of usefulness and honour, I shall accompany him in his progress; and with the honest desire of affording instruction as well as amusement,--for history is useful only as it holds up the mirror of Truth,--I shall continue to point out the various circumstances that may have contributed to his success and scientific renown; and to offer such occasional reflections as may be likely to illustrate not only the superficial peculiarities which constitute the light and shade of character, but those deeper varieties of mind, upon which the superiority of intellect may be supposed to depend.

After all, the great end of biography is not to be found, as some would seem to imagine, in a series of dates, or in a collection of gossiping anecdotes and table-talk, which, instead of lighting up and vivifying the features, hang as a cloud of dust upon the portrait; but it is to be found in an analysis of human genius, and in the developement of those elements of the mind, to whose varied combinations, and nicely adjusted proportions, the mental habits, and intellectual peculiarities of distinguished men may be readily referred.

It has been stated that an arrangement had been concluded between Dr. Beddoes and Davy: it is but an act of justice to say, that it was of a liberal and honourable description; and let me also add in this place, that no sooner had Davy found himself in a situation which secured for him the necessaries of life, than he renounced all claims upon his paternal property, in favour of his mother and sisters.

By acceding to the proposal of Dr. Beddoes, he never intended to abandon the profession in which he had embarked; on the contrary, he persevered in his determination to study and graduate at Edinburgh, and his patron promised that every opportunity should be afforded him at Bristol for seeing medical practice: this part of the arrangement, however, was voluntarily abandoned by him, for he soon became so absorbed by the labours of the laboratory, as to leave little leisure for the clinical studies of the hospital.

The Pneumatic Institution was established for the purpose of investigating the medical powers of factitious airs or gases; and to Davy was assigned the office of superintending the various experiments.

It is now generally acknowledged, that the Art of Physic has not derived any direct advantage from the application of a class of agents which, undoubtedly, held forth the fairest promise of benefit; but it is too frequently the case, that in physic, theory and experience are in open hostilities with each other. The gases are now never employed in the treatment of disease, except by a few crafty or ignorant empirics, whose business it is to enrich themselves by playing on the credulity of mankind: indeed, we may say of popular remedies in general what M. de Lagrange has so wittily said of popular prejudices, that they are the cast-off clothes of philosophers, in which the rabble dress themselves.

The investigation, however, into the nature and composition of the gases paved the way to some new and important discoveries in science; so that, to borrow a Baconian metaphor, although our philosophers failed in obtaining the treasure for which they so eagerly dug, they at least, by turning up and pulverizing the soil, rendered it fertile. The ingenuity of the chemist will for ever remain on record; the phantoms of the physicians have vanished into air.

Davy was now constantly engaged in the prosecution of new experiments, in the conception of which, as he himself informs us, he was greatly aided by the conversation and advice of Dr. Beddoes. He was also occasionally assisted by Mr. William Clayfield, a gentleman ardently attached to chemical pursuits, and whose name is not unknown in the annals of science; indeed, it appears that to him he was indebted for the invention of a mercurial air-holder, by which he was enabled to collect and measure the various gases submitted to examination. He had also the advantages of some society of a highly intellectual cast: it is sufficient to mention the names of Edgeworth and James Tobin.

In reply to a letter of enquiry which was lately addressed to her, Miss Edgeworth observes, that "her father possessed much influence over Davy's mind;" and that "when he was a very young man at Clifton, unknown to fame, Mr. Edgeworth early distinguished and warmly admired his talents, and gave him much counsel, which sunk deep into his mind."

The present Lord Durham and his brother were also resident in the house of Dr. Beddoes, not only for their education, but for the benefit of his professional superintendence. Besides those who were residing at Clifton, the most distinguished in the circles of science and literature paid passing visits to Dr. Beddoes; with many of whom Davy contracted an acquaintance, with some an intimacy, and with a few a solid and permanent friendship. In examining the individuals composing this latter class, we find them differing so widely from each other in character and pursuit, that we are led to enquire upon what principles of affinity his regards could possibly have been attracted--the truth is, that there was more than one avenue to his heart; and the philosopher, the poet, the physician, the philanthropist, and the sportsman, found each, upon different terms, a more or less ready access to its recesses. The chemist who would aspire to his favour, could alone obtain it by laborious application and novel research; the philanthropist, by the practicability of his schemes for improving society, and increasing the sum of its happiness; but the fisherman instantly caught his affections by a hook and line. To be a fly-fisher was, in his opinion, to possess the capabilities of intellectual distinction, although circumstances might not have conspired to call them into action; whilst a proficiency in this art, when exhibited by an individual otherwise distinguished, gave him an additional claim to his attention and regard. The stern courage of Nelson, tempered as it was with all the kindly feelings of humanity, was sufficient to excite in the breast of Davy the most enthusiastic admiration; but the circumstance of his having been a fly-fisher, and continued the sport, even with his left hand, threw, in his opinion, a still brighter halo around his character.

No one who knew him can accuse him of inconstancy in his friendships: amidst the excitements of his station, and the abstractions incident to his pursuits, he might not always have shown those little attentions which are received by the world as the indications of personal regard; but his heart beat not less warmly on that account: when the flame of affection had been once kindled, it burnt with a pure and steady light through life. This will be readily seen in the letters addressed to his several early friends, more especially to Mr. Poole of Nether Stowey, in Somersetshire, and to Mr. Clayfield of Bristol, from which I shall have occasion to present some interesting extracts.

Those who had become acquainted with him in early life, and were enabled to watch the whole progress of his career from obscurity to the highest pinnacle of fame, have declared that his extraordinary talents never at any period excited greater astonishment and admiration than during his short residence at Bristol. His simplicity of mind and manner was also at this time truly delightful. He scarcely knew the names of our best authors, much less read any of their works; yet upon topics of moral philosophy and metaphysics he would enter into discussion with acknowledged scholars, and not only delight them with the native energy of his mind, but instruct them by the novelty and truth of his conceptions. Mr. Coleridge lately expressed to me the astonishment he felt, very shortly after his introduction to him, on hearing him maintain an argument upon some abstruse subject with a gentleman equally distinguished for the extent of his erudition, and for the talent of rendering it available for illustration;--the contrast was most striking--it was the fresh and native wild flower, opposed to the elaborate exotic of the _Hortus Siccus_!

During this period he occasionally visited his friend Mr. Gregory Watt, at Birmingham; at which place his ambition was constantly excited by intercourse with congenial minds; and his letters to his mother and relations represent him as rejoicing in the success of his experiments, and as delighting in his association with kindred genius; but always casting a longing, lingering thought on the scenes of his boyhood, he spoke with joyful anticipation of the period at which he proposed to revisit his mother and family.

That he still continued to regard the practice of physic as the great end and object of all his pursuits, is evident from one of these letters, written in 1799, in which he says, "Philosophy, Chemistry, and Medicine, are my profession."

On the 1st of December 1799 he visited London for the first time, and remained about a fortnight; the friends with whom he associated upon this occasion were Coleridge, Southey, Gregory Watt, Underwood, James and John Tobin, Thomson, and Clayfield; all of whom vied with each other in their exertions to render his visit agreeable, conducting him to such persons and places as were deemed worthy of his notice.

Of all the letters placed at my disposal, those addressed to his early friend and patron, Mr. Davies Gilbert, are, in my judgment, the most interesting: it is true, that as specimens of epistolary style they have but slender pretensions, and are far less pleasing than those written to Mr. Poole and others, in later life; but let it be remembered that, as yet, their writer had never enjoyed the advantages of literary correspondence. For the defects, however, of style, there is more than sufficient compensation; they speak from the heart;--they carry with them internal evidence of the honest simplicity of his mind, and they throw a light upon the peculiarities of his genius, which without such aid might be less perfectly understood; above all, they evince an ardour which no difficulties could repress, and a confidence which no failures could extinguish. We clearly discern from his first letters, that he entered upon his career of experiment with an almost chivalrous feeling, flushed with the consciousness of native strength, and exulting in the prospect of destined achievements.

I am aware that there are those who still object, with Dr. Sprat, to the practice of publishing letters which were never intended for the public eye, and I experience the inconvenience, while I respect the delicacy, of such an opinion. I confess, on my own part, I have always considered, with Mr. Mason, that the objections urged by the learned historian of the Royal Society are wholly untenable. He talks of "the souls of men thus appearing undressed, or in a habit too negligent to go abroad in the streets, although they might be seen by a few in a chamber." But the undress he would condemn, is the nakedness of Truth--the negligent attire, the simple and unadorned expression of those natural and significant traits, whose value incomparably exceeds the premeditated and artificial exhibitions of mind and manner. "_Nam in ingenio quoque sicut in agro, quanquam alia diu serantur atque elaborantur, gratiora tamen quæ sua sponte nascuntur._"[18]

[18] Dialogus de Oratoribus,--_Tacit._

I cannot but suspect that Dr. Sprat was, upon this occasion, more anxious to display a metaphor, than to illustrate a truth. I have often thought a very curious book might be written to show how greatly, both in physics and in morals, the progress of truth has been retarded, and the judgment of men warped, by the abuse of metaphors; the most correct of which can be nothing more than the image of Truth reflected, as it were, from a mirror, and consequently liable to all the delusions of our mental optics. The figure by which Nature was represented as "_abhorring a vacuum_," kept us in ignorance of the true theory of the pump for two thousand years after the discovery of the weight, or gravity, of the atmosphere;[19] and the unfortunate P. L. Courier positively owed his conviction to a metaphor in the Judge's charge--"_Un écrìt plein de poison._"--Well might the defendant exclaim, "_Sauvez-nous de la Metaphore!_"

[19] Plutarch, in expressing the opinion of Asclepiades upon this
subject, represents him as saying, that the external air, _by
its weight_, opened its way with force into the breast. Seneca
also was acquainted with the weight and elastic force of the air;
for he describes the constant effort by which it expands itself
when it is compressed, and affirms that it has the property of
condensing itself, and of forcing its way through all obstacles
that oppose its passage.--Quæst. Nat. lib. v. c. v. and vi.

The first of the letters to which I have alluded appears to have been written rather more than five weeks after his arrival at Clifton.

TO DAVIES GIDDY, ESQ.

Clifton, November 12, 1798.

DEAR SIR,

I have purposely delayed writing until I could communicate to
you some intelligence of importance concerning the Pneumatic
Institution. The speedy execution of the plan will, I think,
interest you, both as a subscriber and a friend to science and
mankind. The present subscription is, we suppose, nearly adequate
to the purpose of investigating the medicinal powers of factitious
airs; it still continues to increase, and we may hope for the
ability of pursuing the investigation to its full extent. We are
negotiating for a house in Dowrie Square, the proximity of which to
Bristol, and its general situation and advantages, render it very
suitable to the purpose. The funds will, I suppose, enable us to
provide for eight or ten patients in the hospital, and for as many
out of it as we can procure.

We shall try the gases in every possible way. They may be condensed
by pressure and rarefied by heat. _Quere_,--would not a powerful
injecting syringe,[20] furnished with two valves, one opening into
an air-holder and the other into the breathing chamber, answer
the purpose of compression better than any other apparatus? Can
you not, from your extensive stores of philosophy, furnish us
with some hints on this subject? May not the non-respirable gases
furnish a class of different stimuli? of which the _oxymuriatic
acid gas_ would stand the highest, if we might judge from its
effects on the lungs; then, probably, _gaseous oxyd of azote_, and
_hydro-carbonate_.

I suppose you have not heard of the discovery of the native
_sulphate of strontian_ in England. I shall perhaps surprise you by
stating that we have it in large quantities here. It had long been
mistaken for _sulphate of barytes_, till our friend Clayfield,
on endeavouring to procure the _muriate of barytes_ from it by
decomposition, detected the strontian. We opened a fine vein of it
about a fortnight ago, at the Old Passage near the mouth of the
Severn. It was embodied in limestone and gypsum, the outside of
the vein, a striated mass; the internal parts finely crystallized
in cubes, of the Sp. Gr. 4·1. Clayfield has been working at it for
some time. We have persuaded him to publish his analysis in the
first volume of the Western Physical Collection.

I have made with him the phosphuret of barytes and of strontian:
they possess, in common with that of lime, the property of
producing phosphorized hydrogen gas; the phosphuret of strontian,
it appears, in a more eminent degree.

We have likewise attempted to decompose the boracic and muriatic
acids, by passing phosphorus, in vapour, through muriate, and
borate of lime, heated red. Phosphate of lime was found in the
experiment on the boracic acid; but, as no pneumatic apparatus was
employed, the experiment was uncertain. We shall repeat them next
week.

We are printing in Bristol the first volume of the 'West Country
Collection,' which will, I suppose, be out in the beginning of
January.

Mrs. Beddoes hopes that Miss Giddy received her letter, and desires
me to certify that she wrote almost immediately after the reception
of her epistle. She is as good, amiable, and elegant as when you
saw her. Believe me, dear Sir, with affection and respect,

Truly your's,
HUMPHRY DAVY.

[20] Here the reader will recognise the force of early
associations.

The work announced in the above letter was published in the commencement of the year 1799, under the title of "Contributions to Physical and Medical Knowledge, principally from the West of England; collected by Thomas Beddoes, M.D."

The first two hundred pages, constituting very nearly half the volume, are the composition of Davy, and consist of essays "On Heat, Light, and the Combinations of Light." "On Phos-oxygen, or Oxygen and its Combinations;" and "On the Theory of Respiration."

His first essay commences with an experiment, in order to show that light is not, as Lavoisier supposed, a modification, or an effect, of heat, but matter of a peculiar kind, _sui generis_, which, when moving through space, or in a state of projection, is capable of becoming the source of a numerous class of our sensations.

A small gunlock was armed with an excellent flint, and, on being snapped in an exhausted receiver, did not produce any light. The experiment was repeated in carbonic acid, and with a similar result. Small particles were in each case separated from the steel, which, on microscopic examination, evidently appeared to have undergone fusion. Whence Davy argued, that light cannot be caloric in a state of projection, or it must have been produced in these experiments, where heat existed to an extent sufficient to fuse steel. Nor, that it can be, as some have supposed, a vibration of the imaginary fluid ether; for, granting the existence of such a fluid, it must have been present in the receiver. If, then, light be neither caloric in a state of projection, nor the vibration of an imaginary ether, it must, he says, be a substance _sui generis_.

With regard to caloric, his opinion that it is not, like light, material, has been already noticed. In the present essay he maintains the proposition by the same method of reasoning as that by which he attempts to establish the materiality of light, and which mathematicians have termed the "_reductio ad absurdum_."

In his chapter on "Light and its Combinations," he indulges in speculations of the wildest nature, although it must be confessed that he has infused an interest into them which might almost be called dramatic. They are certainly highly characteristic of that enlightened fancy, which was perpetually on the wing, and whose flight, when afterwards tempered and directed by judgment, enabled him to abstract the richest treasures from the recesses of abstract truth.

Taking it for granted that caloric has no existence as a material body, or, in other words, that the phenomena of repulsion do not depend upon the agency of a peculiar fluid, and that, on the contrary, light is a subtle fluid acting on our organs of vision _only when in a state of repulsive projection_, he proceeds to examine the French theory of combustion; the defects of which he considers to arise from the assumption of the imaginary fluid _caloric_, and the total neglect of _light_. He conceives that the light evolved during combustion previously existed in the oxygen gas, which he therefore proposes for the future to call PHOS-OXYGEN.[21]

[21] Brugnatelli considered that oxygen, in certain cases of
combination, entered into union with different bodies, without
parting with its _caloric_; and in that state he gave it the
name of THERM-OXYGEN; so that Davy had a precedent for his
nomenclatural innovation.

In following up this question, he would seem to consider Light as the _Anima Mundi_, diffusing through the universe not only organization, but even animation and perception.

_Phos-oxygen_ he considers as capable of combining with additional proportions of Light, and of thus becoming '_luminated Phos-oxygen!_'--from the decomposition of which, and the consequent liberation of light, he seeks to explain many of the most recondite phenomena of Nature.

We cannot but admire the eagerness with which he enlists known facts into his service, and the boldness with which he ranges the wilds of creation in search of analogies for the support and illustration of his views. He imagines that the _Phos-oxygen_, when thus _luminated_, must necessarily have its specific gravity considerably diminished by the combination, and that it will therefore occupy the higher regions of the atmosphere; hence, he says, it is that combustion takes place at the tops of mountains at a lower temperature than in the plains, and with a greater liberation of light. The hydrogen which is disengaged from the surface of the earth, he supposes, will rise until it comes into contact with this _luminated Phos-oxygen_, when, by its attracting the oxygen to form water, the light will be set free, and give origin to the phenomena of fiery meteors at a great altitude.

The phenomenon termed '_Phosphorescence_,' or that luminous appearance which certain bodies exhibit after exposure to heat, is attributed by this theory to the light, which may be supposed to quit such substances as soon as its particles have acquired repulsive motion by elevation of temperature.

The Electric Fluid is considered as Light in a condensed state, or, in other words, in that peculiar state in which it is not supplied with a repulsive motion sufficiently energetic to impart projection to its particles; for, he observes, that its chemical action upon bodies is similar to that of Light; and when supplied with repulsive motion by friction, or by the contact of bodies from which it is capable of subtracting it, it loses the projectile form, and becomes perceptible as Light. It is extremely probable, he adds, that the great quantity of this fluid almost everywhere diffused over our earth is produced by the condensation of Light, in consequence of the subtraction of its repulsive motion by black and dark bodies; while it may again recover the projectile force by the repulsive motion of the poles, caused by the revolution of the earth on its axis, and thus appear again in the state of sensible light; and hence the phenomenon of the _Aurora Borealis_, or Northern Lights.

In considering the theory of Respiration, he supposes that _phos-oxygen_ combines with the venous blood without decomposition; but that, on reaching the brain, the light is liberated in the form of Electricity, which he believes to be identical with the nervous fluid. On this supposition, sensations and ideas are nothing more than motions of the nervous ether; or light exciting the medullary substance of the nerves and brain into sensitive action!

He thinks it would be worth while to try, by a very sensible electrometer, whether an insulated muscle, when stimulated into action, would not give indications of the liberation of electric fluid, although he suspects that in man the quantity is probably too small, and too slowly liberated, to be ascertainable. In the torpedo, and in some other animals, however, it is unquestionably given out perceptibly during animal action.

When any considerable change takes place in the organic matter of the body, so as to destroy the powers of life, new chemical attractions and repulsive motions take place, and the different principles of which the body is composed enter into new combinations. In this process, which is called putrefaction, Davy, in pursuance of this theory, thinks that in land-animals the latent light of the system enters into new combinations with oxygen and nitrogen, but that in fish no such combinations occur, and hence the luminous appearance which accompanies their putrefaction.

Such is the outline of these extraordinary Essays. They stand upon record, and therefore, as a faithful biographer, I was bound to notice them; nor are they devoid of interest or instruction: I am not quite sure that, amidst all the meteors of his fancy, there may not be a gleam of truth. I allude to his theory of Respiration: it certainly does not square aôwith the physiological opinions of the day; nor did that of Newton, when he conjectured that water might contain an inflammable element; but it was the refraction of a great truth, at that time below the horizon.

It was a very ancient opinion, that life, being in its own nature aëriform, is under the necessity of renewing itself by inspiring the air. Modern chemistry, by teaching us the nature of the atmosphere, has dispelled many fanciful theories of its action, but it has not yet explained why respiration, the first and last act of life,[22] cannot be suspended, even for a minute, without the extinction of vitality. When we reflect upon this fact, it is scarcely possible not to believe that the function has been ordained for some greater purpose than that of removing a portion of carbon from the circulating blood. Is it unreasonable to conclude that some principle is thus imparted, which is too subtle to be long retained in our vessels, and too important to be dispensed with, even for the shortest period? "I offer this opinion," as Montaigne says, "not as being good, but as being my own."

[22] Breath and life are synonymous. In the Greek, the most
philosophically constructed language with which we are
acquainted, this _first_ and _last_ act is expressed by a verb
composed of alpha and omega--[Greek: aô]. In the Latin, the
connexion between _spiro_ and _spiritus_, breath and life, is
evident.

By these observations, I am not to be supposed as wishing, for a moment, to uphold the wild hypotheses which I have just related; it must be admitted that the theory of _phos-oxygen_ and _luminated phos-oxygen_ has scarcely a parallel in extravagance and absurdity; and I happen to know that, in after life, Davy bitterly regretted that he had so committed himself; any allusion to the subject became a source of painful irritation. It is to be remarked, that in every course of lectures, although Davy did not refer to these theories, he frequently alluded to the unphilosophic spirit that had given origin to them; as if he had imposed upon himself this penance as an atonement for his early follies. The following note was taken at one of his lectures:--"After what has been said, it will be useless to enter upon an examination of any of those theories, which, assuming for their foundation the connexion of life with respiration, have attempted to prove that oxygen is the principle of life, and that the wonderful and mysterious phenomena of perception arise from the action of common gravitating substances upon each other. Such theories are the dreams of misemployed genius, which the light of experiment and observation has never conducted to truth, and are merely a collection of terms derived from known phenomena, and applied by loose analogies of language to unknown things."

The reader, however, will be disposed to treat him with all tenderness when he remembers that the author of these Essays was barely eighteen years of age. If blame is to fall on any one, let it fall on Dr. Beddoes, who never should have sanctioned the publication: had he curbed the ardent and untamed imagination of the young philosopher, he would have acted the part of a wise man and of a kind friend. But the truth is, that much as Davy needed the bridle, Beddoes[23] required it still more; for, notwithstanding his talents, he was as little fitted for a Mentor as a weathercock for a compass; and had it not been for the ascendency which Davy gained over his mind, the ardour of his temperament would have continually urged him beyond the bounds of reason.

[23] The only pun Davy is said to have ever made was upon the
occasion of Mr. Sadler being appointed by Dr. Beddoes as his
successor. "I cannot imagine," said he, "why he has engaged
_Sadler_, unless it is that he may be well _bridled_."

Caught by the loosest analogies, he would arrive at a conclusion without examining all the conditions of his problem. In the exercise of his profession, therefore, he was frequently led to prescribe plans which he felt it necessary to retract the next hour. His friend Mr. T---- had occasion to consult him upon the case of his wife: the Doctor prescribed a new remedy; but, in the course of the day he returned in haste, and begged that, before Mrs. T---- took the medicine, its effect might be tried on a dog!

The following anecdote, which was lately communicated to me by Mr. Coleridge, will not only illustrate a trait of character, but furnish a salutary lesson to the credulous patron of empirics. As soon as the powers of nitrous oxide were discovered, Dr. Beddoes at once concluded that it must necessarily be a specific for paralysis. A patient was selected for the trial, and the management of it was entrusted to Davy. Previous to the administration of the gas, he inserted a small pocket thermometer under the tongue of the patient, as he was accustomed to do upon such occasions, to ascertain the degree of animal temperature, with a view to future comparison. The paralytic man, wholly ignorant of the nature of the process to which he was to submit, but deeply impressed, from the representations of Dr. Beddoes, with the certainty of its success, no sooner felt the thermometer between his teeth than he concluded that the _talisman_ was in full operation, and in a burst of enthusiasm declared that he already experienced the effects of its benign influence throughout his whole body:--the opportunity was too tempting to be lost--Davy cast an intelligent glance at Mr. Coleridge, and desired the patient to renew his visit on the following day, when the same ceremony was again performed, and repeated every succeeding day for a fortnight, the patient gradually improving during that period, when he was dismissed as cured, no other application having been used than that of the thermometer. Dr. Beddoes, from whom the circumstances of the case had been intentionally concealed, saw in the restoration of the patient the confirmation of his opinion, and the fulfilment of his most ardent hope--Nitrous Oxide was a specific remedy for Paralysis! "It were criminal to retard the general promulgation of so important a discovery; it were cruel to delay the communication of the fact until the publication of another volume of his '_Contributions_;' the periodical magazines were too slow in their rate of travelling,--a flying pamphlet would be more expeditious; paragraphs in the newspapers; circulars to the hospitals:"--such were the reflections and plans which successively agitated the physician's mind, when his eyes were opened to the unwelcome truth by Davy's confessing the delusion that had been practised.

A short time after the publication of the first volume of the "Contributions," Davy addressed to his friend the following letter:--

TO DAVIES GIDDY, ESQ.

Clifton, Feb. 22, 1799.

DEAR FRIEND,--for I love you too well to call you by a more
ceremonious name,--I have delayed writing to you from day to day,
expecting that some of our experiments would produce results worthy
of communication. Since I received your last very acceptable
letter, I have been chiefly employed in pursuing the experiments on
Heat, Light, Respiration, &c. Of these experiments I shall give you
no account, as you will see them in print. I sent you a copy of my
Essays last week; if you have not received them, I trust you will
find them at my mother's, or at Mr. Tonkin's.

In the same parcel were two small packets, one from Mrs. Beddoes
for your father, the other for Miss Giddy from Mrs. Willoughby.
About a fortnight ago I sent a few chemical instruments to Mr.
Penneck of Penzance; and inclosed with them were specimens of the
different varieties of sulphate of strontian addressed to you. If
you have not received them, you will get them by sending to Mr.
Penneck.

On looking over a box of minerals last week, which was sent to
Dr. Beddoes from Cumberland, I found two very fine specimens of
sulphate of strontian, marked by the collector _Laminated Shorl_. I
suspect this mineral is not scarce in calcareous countries; it is,
I dare say, often mistaken for sulphate of barytes.

I have succeeded in combining strontian with the oxygenated
muriatic acid. This salt possesses most astonishing properties;[24]
you will find an account of them in my Essay.

When you have perused my papers, I shall be very much obliged to
you for a criticism upon them. When I left Penzance, I was quite an
infant in speculation,--I knew very little of Light or Heat. I am
now as much convinced of the non-existence of caloric, as I am of
the existence of light. Independent of the experiments which appear
to demonstrate its non-existence directly, and of which you will
find an account in my Essay, the consideration of certain phenomena
leads me to suppose that there would be no difficulty in proving
its non-existence by reasoning. These considerations have occurred
to me since the publication of the work. I could now render it much
more perfect; but I hope soon to complete the investigation of the
combinations of Light, and to produce a much more perfect work on
the subject. I shall be infinitely obliged to you for any hints
or observations, as far as the detection of errors of any kind,
for it is no flattery to say that I pay greater deference to your
opinion than to that of any other philosopher.

We intend next week to endeavour to ascertain, by the aid of a
delicate balance, the quantities of Light liberated in different
combustive processes. That there is a deficiency of weight, I am
convinced from many experiments.

The experiments on Light, &c. have prevented me from attempting
the decomposition of the undecompounded acids. We have ordered an
apparatus at the glass-house for this purpose, and I hope next
week we shall be able to carry on the investigation. Two modes
of effecting these decompositions have occurred to me:--first,
to bring phosphorus or sulphur, in the gaseous state, in contact
with the acid gases in a tube heated intensely; secondly, to send
sulphur in the gaseous state through muriate of copper or lead,
heated white. The attraction of sulphur for oxygen, of copper
for oxygen, and of sulphur for copper, will probably effect the
decomposition.

Our laboratory in the Pneumatic Institution is nearly finished, and
we shall begin the investigations in about a fortnight. We shall
begin by trying the gases in their simplest mode of application,
and gradually carry on the more complex processes.

I hope the gaseous oxide of azote will prove to be a specific
stimulus for the absorbents.

I was last week surprised by a letter from Mr. Watt, announcing
the success of their trial. When I was at Birmingham five weeks
ago, the family were in very low spirits. I spent nine or ten
days there, chiefly with Mr. Keir and Mr. Watt: I had a great
deal of chemical conversation with them. Mr. Keir is one of the
best-informed men I have ever met with, and extremely agreeable.
Both he and Mr. Watt are still phlogitians; but Mr. Keir altogether
disbelieves the doctrine of _calorique_.

What news have you in Cornwall? Has Mr. John Hawkins returned to
his native county? he will doubtless be a great acquisition to you.

Pray do you know whether the Zoophyta and marine worms are
susceptible of the galvanic stimulus? Experiments on them would
go far to determine whether the irritable or sensitive fibre is
primarily affected.

I know of little general scientific news. In the last volume of the
_Annales de Chimie_ is a curious paper by Berthollet on sulphurated
hydrogen: he makes it out to be an acid. I shall most anxiously
expect a letter from you, and I remain with affection and respect,

Yours,
HUMPHRY DAVY.

[24] The following is the account given in his Essay. "When
sulphuric acid was poured into a solution of this salt in water,
a beautiful and unexpected phenomenon took place. The room was
accidentally darkened at the moment this experiment was made, so
that we were enabled to perceive a vivid luminous appearance.
This experiment, independent of its beauty, is extremely pleasing
as affording an instance of true combustion, that is, the
production of Light and Heat by the mixture of two incombustible
bodies." It may be presumed, that this phenomenon arose from the
developement and decomposition of a portion of Euchlorine, a
compound which he subsequently discovered in 1811. In the year
1813, Chevreul announced, as a new discovery, that if strontian
be heated in contact with muriatic acid gas, the gas is absorbed,
and the earthy salt becomes red hot.--_See Annals of Philosophy_,
vol. ii. p. 312.

The letter which follows may be considered as a reply to one received from Mr. Davies Gilbert, which, it would appear, contained strictures upon his recently published Essays.

TO DAVIES GIDDY, ESQ.

April 10, 1799.

MY DEAR FRIEND,

The engagements resulting from the establishment of the Pneumatic
Institution, and from a course of experiments, to which I have
been obliged to pay great attention, have prevented me from
acknowledging to you my obligations for the very great pleasure I
received from your last excellent letter.

In experiments on Light and Heat, we have to deal with agents whose
changes we are unable directly to estimate. The most we can hope
for is such an arrangement of facts as will account for most of the
phenomena.

The supposition of active powers common to all matter, from
the different modifications of which all the phenomena of its
changes result, appears to me more reasonable than the assumption
of certain imaginary fluids alone endowed with active powers,
and bearing the same relation to common matter, as the vulgar
philosophy supposes spirit to bear to matter.

That the particles of bodies must move, or separate from each
other, when they become expanded, is certain. A repulsive motion of
the particles is directly the cause of expansion; and when bodies
are expanded by friction, under circumstances in which there could
be no heat communicated by bodies in contact, no oxidation and
no diminution of capacity, I see no difficulty in conceiving the
repulsive motion generated by the mechanical motion.

Your excellent and truly philosophic observations will induce me to
pay greater attention to all my positions. It is only by forming
theories, and then comparing them with facts, that we can hope to
discover the true system of nature. I will endeavour very soon to
give an answer to the remaining part of your excellent letter.

I have now just room to give you an account of the experiments I
have lately been engaged in, though they are not much connected
with light and heat.

_First._--One of Mr. William Coate's children accidentally
discovered that two bonnet-canes rubbed together produced a faint
light. The novelty of this phenomenon induced me to examine it, and
I found that the canes on collision produced sparks of light, as
brilliant as those from the flint and steel.

_Secondly._--On examining the epidermis, I found, when it was taken
off, that the canes no longer gave light on collision.

_Thirdly._--The epidermis, subjected to chemical analysis, had all
the properties of silex.

_Fourthly._--The similar appearance of the epidermis of reeds,
corn, and grasses, induced me to suppose that they likewise
contained silex. By burning them carefully, and analysing their
ashes, I found that they contained it in rather larger proportions
than the canes.

_Fifthly._--The corn and grasses contain sufficient potash to form
glass with their flint. A very pretty experiment may be made on
these plants with the blow-pipe. If you take a straw of wheat,
barley, or hay,[25] and burn it, beginning at the top, and heating
the ashes with the blue flame, you will obtain a perfect globule of
hard glass fit for microscopic experiments.

I made a discovery yesterday which proves how necessary it is
to repeat experiments. The gaseous oxide of azote is perfectly
respirable when pure. It is never deleterious but when it contains
nitrous gas. I have found a mode of obtaining it pure, and I
breathed to-day, in the presence of Dr. Beddoes and some others,
sixteen quarts of it for near seven minutes. It appears to support
life longer than even oxygen gas, and absolutely intoxicated me.
Pure oxygen gas produced no alteration in my pulse, nor any other
material effect; whereas this gas raised my pulse upwards of twenty
strokes, made me dance about the laboratory as a madman, and has
kept my spirits in a glow ever since. Is not this a proof of the
truth of my theory of respiration? for this gas contains more light
in proportion to its oxygen than any other, and I hope will prove a
most valuable medicine.

We have upwards of eighty out-patients in the Pneumatic
Institution, and are going on wonderfully well.

I shall hope for the favour of a letter from you, and in my answer
to it will fully inform you of our proceedings. I have just room to
add that I am

Yours, with affection and respect,
HUMPHRY DAVY.

[25] It is very common, after the burning of a hay-stack, to find
glass in the ashes. P.

I cannot suffer the experiments with the bonnet-canes to pass, without endeavouring to infuse into the reader a portion of that admiration which I feel in relating them. They furnish a beautiful illustration of that combination of observation, experiment, and analogy, first recommended by Lord Bacon, and so strictly adopted by Davy in all his future grand researches.

In alluding to this discovery--that siliceous earth exists generally in the epidermis of hollow plants--Davy observes in his agricultural lectures, that "the siliceous epidermis serves as a support, protects the bark from the action of insects, and seems to perform a part in the economy of these feeble vegetable tribes, similar to that performed in the animal kingdom by the shell of the crustaceous insects."

The circumstance that first led him to the investigation of the nature of _nitrous oxide_, or the _gaseous oxide of azote_, alluded to in the foregoing letter, has been thus recorded by himself. "A short time after I began the study of Chemistry, in March 1798, my attention was directed to the _dephlogisticated nitrous gas_ of Priestley (nitrous oxide) by Dr. Mitchell's theory of Contagion, by which he attempted to prove that _dephlogisticated nitrous gas_! which he calls _oxide of septon_, was the principle of contagion, and capable of producing the most terrible effects, when respired by animals in the minutest quantities, or even when applied to the skin, or muscular fibre.

"The fallacy of this theory was soon demonstrated by a few coarse experiments, made on small quantities of this gas procured, in the first instance, from zinc and diluted nitrous acid. Wounds were exposed to its action; the bodies of animals were immersed in it without injury; and I breathed it, mingled in small quantities with common air, without any remarkable effects. An inability to procure it in sufficient quantities prevented me, at this time, from pursuing the experiments to any greater extent. I communicated an account of them to Dr. Beddoes."

His situation in the "Medical Pneumatic Institution" in 1799, imposing upon him the duty of investigating the physiological effects of such aëriform fluids as held out any promise of useful agency, he resumed the investigation; a considerable period, however, elapsed, before he succeeded in procuring _nitrous oxide_ in a state of purity; he was therefore obliged to breathe it in mixture with oxygen gas, or common air; but as no just conclusion could be deduced from the action of an impure gas, he commenced an enquiry for the purpose of discovering a process by which it might be procured in an uncontaminated condition; when, after a most laborious investigation concerning its composition, properties, and combinations, enquiries which were necessarily extended to the different bodies connected with nitrous oxide, such as _nitrous gas_, _nitrous acid_, and _ammonia_, he was enabled, by a series of intermediate and comparative experiments, to reconcile apparent anomalies, and thus, by removing the greater number of those difficulties which had previously obscured this branch of science, to present to the chemical world the first satisfactory history of the COMBINATIONS OF OXYGEN AND NITROGEN.

Thus prepared, he proceeded to examine the action of nitrous oxide upon living beings, and to compare it with the effects of other gases upon man; and in this manner he completed its physiological, as he had already done its chemical history.

These interesting results were published in a distinct volume, in the year 1800, entitled, "Researches Chemical and Philosophical, chiefly concerning Nitrous Oxide, and its Respiration. By Humphry Davy, Superintendent of the Medical Institution."

It may be observed in passing, that the merits of this work could never have been inferred from the title-page, which its most sanguine admirers must admit to be as clumsy and unpromising an invitation as an author ever addressed to his scientific brethren.

Amongst Davy's letters to Mr. Gilbert, I find one written on a proof sheet of the chapter of contents of the above work, and which may not be uninteresting in this place.

TO DAVIES GIDDY, ESQ.

July 3, 1800.

That our feelings, as well as our actions, are rendered stronger
and more vivid by habit, is probable from many facts, and from no
one more so than that of procrastination. My much respected friend,
two months after my return,[26] I had formed the resolution of
writing to you; week after week this resolution was renewed and put
off to a future day, with the hope that this day, by presenting
something new, would enable me to make my letter more interesting.
In vain! the feeling of procrastination, thus increased by
association, at length became so strong as to prevent me from
writing at all.[27]

I have received your letter; it has awakened my duties, and has
been doubly welcome, as being unexpected and undeserved.

Since my return to the Pneumatic Institution in December, I have
been almost incessantly occupied, from January to April, in
completing a series of experiments on Gases, and their application;
and from April to the present time, in writing and printing an
account of them.

I have written this letter on the table of contents of a work which
will be published in the course of the month, and of which I shall
take the earliest opportunity to send you a copy. This table of
contents will give you a better idea of the nature and extent of
the investigation, than I could possibly have given in a letter.

We have been repeating the Galvanic experiments with success.
Nicholson, by means of a hundred pieces of silver and zinc, has
procured a visible spark. Cruickshank has revived oxidated metals
in solution, by means of the nascent hydrogen produced from the
decomposition of water by the shock; and both he and Carlisle have
absolutely resolved water into oxygen and hydrogen by means of
it, making use of silver and platina wires. An immense field of
investigation seems opened by this discovery: may it be pursued so
as to acquaint us with some of the laws of life!

You have, undoubtedly, heard of Herschel's discovery concerning
the production of heat by invisible rays emitted from the sun. By
placing one thermometer within the red rays, separated by a prism,
and another beyond them, he found the temperature of the outside
thermometer raised more than that of the inside one.

When I first heard of Mr. Tennant's discovery,[28] I was very much
struck by an observation which you long ago made to me, on the
fertility of the Cornish lands, in which there was decomposed,
_feltspar_ or _serpentine_.

Mr. Tennant spent a day here some time ago, when I mentioned
your observation to him, but he could not give any solution of
the phenomenon. _Quere._--As lime and magnesia are probably both
subservient to vegetation, only from supplying plants with carbonic
acid, may not lime, when mingled with magnesia, in the process of
vegetation, render it partially caustic, and thus enable it to
destroy them?

Your observation on the scale of numbers, and the fact relative
to it, are highly interesting. Reasoning on this subject would
literally form the logic of generalization, or the application of
one term to signify many terms, or many ideas, on which science
ultimately depends. _Quere._--How far have the first attempts
at generalization arisen from accident, and how far from the
resemblance between ideas?

Dr. Beddoes has always ridiculed the "_Tractors_," in common with
all other reasonable men. He is about to publish a new work on the
Nitrous Acid.

J. Wedgwood is returned, very little altered for the better.
Coleridge is gone to reside in Cumberland; he was here the week
before last, and spent much time with me, and often spoke of you
with the greatest interest. Clayfield is at this moment chiefly
engaged in commercial speculations. He has found a new mode of
making soda, which there is every reason to believe will turn out
profitable.

I hope some time in the autumn to see you, and to enjoy the well
remembered pleasure of your conversation; in the mean while, I
remain, with respects to your family,

Yours with sincere affection,
HUMPHRY DAVY.

[26] From his visit to London, as noticed at page 62.

[27] With respect to the metaphysical speculation contained in
this paragraph of his letter, had he not written it in haste, we
might presume he would have given a more exact expression to his
ideas. By the misapplied term "_Feeling of Procrastination_," he
doubtless meant to describe that aversion to labour which becomes
habit by indulgence, and the perception of which, so far from
increasing in vividness, actually languishes to obtuseness. To
borrow an expression from Dr. Johnson, Davy, in his metaphysical
speculations, not unfrequently trod upon the brink of meaning,
where light and darkness begin to mingle.

[28] Davy here alludes to the fact of magnesian earth being
prejudicial to vegetation.

In estimating the early genius of Davy, and his character as a philosopher, the style and matter of his "RESEARCHES" will afford us much assistance. The close philosophical reasoning,--the patient and penetrating industry,--the candid submission to every intimation of experiment, and the accuracy of manipulation, so remarkably displayed throughout this work, have been rarely equalled, and perhaps never surpassed.

There is scarcely to be found a more striking illustration of chemical genius, than that afforded by his chapter on the "Absorption of _Nitrous Gas by solutions of green Sulphate of Iron_."

The address with which he gradually disentangles the subject of its difficulties, and catches at every opening to truth, affords a study which may be safely recommended to the attention of every young experimentalist, as being no less instructive than it is beautiful.

The phenomena attending the absorption of _nitrous gas_ by solutions of _sulphate of iron_ had been examined by Vauquelin and by Berthollet, but the conclusions of these chemical philosophers were fatally infected by errors, arising from the neglected action of the atmosphere. Davy, by conducting his experiments over mercury, proved that, in the absence of air, the absorption was simply owing to a combination between the gas and the fluid; but that, on admitting air, the nitrous _gas_ became nitrous _acid_, a portion of which, together with a part of the water, subsequently underwent decomposition, and gave origin to _ammonia_, and ultimately to _nitrate of ammonia_, while the iron passed into the state of a _peroxide_.

We have also to admire in this work an ardour for investigation, which even the most imminent personal danger could not repress. He may truly be said to have sought the bubble reputation in the very jaws of Death. What shall we say of that spirit which led him to inspire nitrous gas, at the hazard of filling his lungs with the vapour of _aqua fortis_! or what, of that intrepid coolness which enabled him to breathe a deadly gas, and to watch the advances of its chilling power in the ebbing pulsations at the wrist!

These experiments, however, are far too interesting and important to be related in any other than the author's own words; but it is first necessary that his trials with the _nitrous oxide_ should be considered.

He found that this gas might be most conveniently, as well as most economically, prepared by the decomposition of a salt known by the name of _nitrate of ammonia_, by the application of a regulated heat; but, as the researches by which he arrived at this conclusion are recorded at length in his work, and as the most important of them are now embodied in every elementary system of chemistry, it would not only be tedious but useless, to enter into a detail of them upon this occasion.