CHAPTER VII.

The unfair rivalry of Philosophers.--Bonaparte the Patron

of Science.--He liberates Dolomieu.--He founds a Prize for

the encouragement of Electric researches.--His letter to the

Minister of the Interior.--Proceedings of the Institute.--The

Prize is conferred on Davy.--The Bakerian Lecture of 1807.--The

Decomposition of the Fixed Alkalies--Potassium--Sodium.--The

Questions to which the discovery gave rise.--Interesting

Extracts from the Manuscript Notes of the Laboratory.--Potash

decomposed by a chemical process.--Letters to Children, and

Pepys.--The true nature of Potash discovered.--Whether Ammonia

contains Oxygen.--Davy's severe Illness.--He recovers and

resumes his labours.--His Fishing Costume.--He decomposes the

Earths.--Important views to which the discovery has led.

It must be confessed that there has too frequently existed amongst

philosophers a strange and ungenerous disposition to undervalue

the labours of their contemporaries. If a discovery be made, its

truth and importance are first questioned; and should these be

established, then its originality becomes a subject of dispute.

Truth, although she may have been rarely held fast, has been

frequently touched[69] in the dark: it is not extraordinary,

therefore, that evidence may be often strained from the writings of

philosophers in support of prior claims to late discoveries; but

upon a candid review, these loose statements, or obscure hints,

will generally be found wholly destitute of the pretensions which

an unfair spirit of rivalry has too often laboured to support. Many

of such hints, indeed, so far from advancing the progress of truth,

had never even attracted notice, until after the discoveries to

which they have been supposed to relate.

[69] A most remarkable illustration of this fact occurs in the

history of Locke, who certainly came as near to an important

discovery as any philosopher who ever caught a glimpse of a truth

without seizing it; but his statement did not, in any degree,

hasten the developement of that new branch of science which was

reserved for the genius of Dr. Black to investigate, and who a

century later, by the discovery of fixed air, changed the whole

face of Chemistry. The passage to which I allude is extracted

from the Life by Lord King, and is so curious, that I shall give

it a place in this note. "M. Toinard produced a large bottle of

Muscat: it was clear when he set it on the table; but when he

had drawn out the stopper, a multitude of little bubbles arose,

and swelled the wine above the mouth of the bottle. It comes

from this, that the air, which was included and disseminated

in the liquor, had liberty to expand itself, and so to become

visible, and, being much lighter than the liquor, to mount with

great quickness.--_Quere_, Whether this be air new generated, or

whether the springy particles of air in the fruit, out of which

these fermenting liquors are drawn, have, by the artifice of

Nature, been pressed close together, and there by other particles

fastened and held so; and whether fermentation does not loose

these bands, and give them liberty to expand themselves again?

Take a bottle of fermenting liquor, and tie a bladder on the

mouth.--_Quere_, How much new air will it produce; and whether

this has the quality of common air?"

Another instance equally illustrative of the manner in which

important truths will sometimes elude notice, even after Science

has approached so near as to touch them, is presented in the

history of the Barometer. Toricelli, the pupil of Galileo, while

reflecting upon the phenomenon which had so greatly perplexed

his master, viz. that water could not be raised above thirty-two

feet in the body of a pump, rightly conjectured that the water,

under such circumstances, was not _drawn_, but _pushed up_ into

the barrel, and that it could only be so pushed up by the force

of the atmosphere. It then occurred to him, that if mercury were

used instead of water, being heavier, it would not be pushed

up so high by the weight of the air. So, taking a glass tube

of about three feet in height, made air-tight at one end, he

first filled it completely with quicksilver, and then closing it

with his finger, reversed it in a basin containing that metal;

when he had the gratification of seeing the liquid in the tube

descend, as he had anticipated. Here then was the discovery of

the BAROMETER; but it was reserved for another to find out that

such an instrument had been actually invented. Pascal first made

the remark, that the inference of Toricelli, if true, might

be confirmed by carrying the mercurial tube to a considerable

elevation; when the atmospheric column being diminished, that of

the mercury, which was supposed to be its balance, ought likewise

to be shortened in a corresponding proportion. It followed

then, that a measure of the weight of the atmosphere, in all

circumstances, had been obtained, and consequently that of the

height of any place to which the instrument could be carried. In

this manner was a discovery completed, which had for ages escaped

the greatest philosophers who had made the nearest approaches to

its developement.

Although the importance of Davy's Electro-chemical discoveries

could not for a moment be doubted; their claims to originality,

it would seem, were not admitted without some question. The works

of Ritter and Winterl, amongst many others, were quoted to show

that these philosophers had imagined or anticipated the relation

between electrical powers and chemical affinities; but Davy very

fairly observes, in a paper read before the Royal Society in 1826,

that in the obscurity of the language and metaphysics of both those

gentlemen, it is difficult to say what may not be found. In the

ingenious though wild views of Ritter, there are hints which

may more readily be considered as applying to _Electro-magnetism_

than to _Electro-chemistry_; while Winterl's _Miraculous Andronia_

might, with as much propriety, be considered as a type of all the

chemical substances that have been since discovered, as his view

of the antagonist powers (the acid and base) be regarded as an

anticipation of the _Electro-chemical_ theory.

It would be worse than useless to speak of other works, which refer

the origin of Electro-chemistry to Germany, Sweden, and France,

rather than to Italy and England; and which attribute some of the

views first developed by Davy, to philosophers who have not, nor

ever could have made any claim of the kind, since their experiments

were actually not published until many years after 1806, the date

of the Bakerian Lecture.

With regard to the judgment of posterity upon these points, but

little apprehension can be entertained. I well remember, in a

conversation with Davy, he observed, that "a philosopher might

generally discover how his labours would be appreciated in after

ages, from the opinion entertained of them by contemporary

foreigners, who, being unbiassed by circumstances of personality,

will reduce every object to its just proportions and value."

If we acknowledge the truth of such a standard, and submit the

posthumous fame of Davy to its measure, where is the philosopher,

in our times, whose name is destined to attain a higher eminence

in the history of Science? Let the reader only recall to his

recollection the bitter animosity which France and England

mutually entertained towards each other in the year 1807, and he

will be able to form some idea of the astounding impression which

the Bakerian Lecture must have produced on the Savans of Paris,

when, in despite of national prejudice and national vanity, it

was crowned by the Institute of France with the prize of the

First Consul! Thus did the Voltaic battery, in the hands of the

English chemist, achieve what all the artillery of Britain could

never have produced--A SPONTANEOUS AND WILLING HOMAGE TO BRITISH

SUPERIORITY!--But let not this observation convey the slightest

idea of disrespect, or be supposed to encourage any feeling to the

disparagement of the chemists of France; on the contrary, it is

even a question not readily answered, to which party the triumph

fairly belongs,--to him who won the laurel crown, or to those who

so nobly placed it on his brow? They have set an example to future

ages, which may as materially advance the progress of science,

as the researches which called it forth:--they have shown, to

adopt the language of an eloquent writer, that "the Commonwealth

of Science is of no party, and of no nation; that it is a pure

Republic, and always at peace. Its shades are disturbed neither by

domestic malice nor foreign levy; they resound not with the cries

of faction or of public animosity. Falsehood is the only enemy

their inhabitants denounce; Truth, and her minister Reason, the

only leaders they follow."

I shall avail myself of this opportunity to introduce the Report

drawn up by M. Biot, and made in the name of a Commission

appointed by the Institute to accomplish the intention of

Bonaparte, who, when First Consul, founded prizes for important

discoveries in Electricity or Galvanism.

It is an opinion very generally received, that despotism is hostile

to the progress of Philosophy--that the suspicion natural to

tyranny, and the fear that light should expose its deformity, have,

under such circumstances, inspired a dread of any thing approaching

to freedom of enquiry. The conduct of Napoleon, not only during his

Consulate, but even after he had assumed the Purple, is in direct

opposition to such an opinion. Now that the excitements of national

hostility have subsided, and the asperity of our feelings towards

that extraordinary man has been softened by time and prosperity, we

are enabled to discern the bright and sunny spots in his character.

Not to mention the immense plans which his genius suggested for the

internal improvement of France, the annals of the Institute would

furnish innumerable proofs of the zeal with which he encouraged

Science, and promoted its interests.

His liberation of Dolomieu from the dungeons of Tarentum was an

act not only remarkable for the considerate regard it displayed

for Science, but for the spirit and eagerness with which it was

effected. The French Government had repeatedly made the most urgent

demands for the liberty of one who had reflected so much credit

on his country;--the Danes had also directed the interference of

their Minister, and the King of Spain had added his solicitations

in vain:--no sooner, however, had the astonishing campaign which

terminated by the victory of Marengo, completely established the

French Republic, than Bonaparte, in making peace with Naples,

stipulated for the immediate deliverance of Dolomieu, as the first

article of the treaty.

The following letter from Bonaparte, addressed to the Minister of

the Interior, and by him transmitted to the Institute, expresses

the intentions of the First Consul, in founding prizes for

important discoveries in Electricity or Galvanism.

"I intend, Citizen Minister, to found a prize, consisting of a

Medal of three thousand francs, (about one hundred and twenty

pounds sterling,) for the best experiment which shall be made in

the course of each year, on the Galvanic fluid.

"For this purpose, the Memoirs containing the details of the said

experiments shall be sent before the First of _Fructidor_, to the

Class of the Mathematical and Physical Sciences, which in the

complimentary days shall adjudge the prize to the author of that

experiment which has been most useful to the progress of Science.

"I also desire to give, by the way of encouragement, the sum of

sixty thousand francs to the person who, by his experiments and

discoveries, shall, according to the opinion of the Class, advance

the knowledge of Electricity and Galvanism as much as Franklin and

Volta did.[70]

"Foreigners of all nations are admitted to the competition.

"I beg you will make known these dispositions to the President of

the First Class of the National Institute, that it may give to

these ideas such developement as may appear proper; my particular

object being to encourage philosophers, and to direct their

attention to this part of philosophy, which, in my opinion, may

lead to great discoveries.

"(Signed) BONAPARTE."

[70] "À celui qui, par ses expériences et ses découvertes, _fera

à faire à l'Electricité et au Galvanisme un pas comparable à

celui qu'ont fait faire à ces Sciences Franklin et Volta_."

My French correspondent adds, "Ces soixantes mille francs n'ont

pas été adjugés, _le pas n'ayant point été fait_."

Upon the presentation of this letter, a Committee was appointed

to consider the means for accomplishing the intentions of the

First Consul; and after expatiating upon the extensive agencies of

Electricity, their Report concludes in the following manner:--

"To fulfill the intention of the First Consul, and to give to the

competition all the solemnity which the importance of the object,

the nature of the Prize, and the character of the Founder require,

the Commissioners unanimously propose as follows:

"The Class of the Mathematical and Physical Sciences of the

National Institute opens the general competition required by the

First Consul.

"All the learned of Europe, and the Members and Associates of the

Institute, are admitted to the competition.

"The Class does not require that the Memoirs should be immediately

addressed to it. Every year it will crown the author of the best

experiments which shall come to its knowledge, and which shall have

advanced the progress of the science.

"The present report, containing the letter of the First Consul,

shall be printed, and serve as a programme.

"Done at the National Institute, Messidor 11, year 10.

"(Signed) LAPLACE, HALLE, COULOMB,

HAUY. BIOT, Reporter."

It was not until twelve months after the publication of his

first Bakerian Lecture, that Davy received the intelligence

that the prize of three thousand francs had been awarded him by

the Institute of France, for his discoveries announced in the

Philosophical Transactions for the year 1807.

Mr. Poole, in a late communication, informs me that he was in

London soon after the letter communicating this gratifying

intelligence had been received from France; and that Davy, upon

showing it to him, observed, "Some people say I ought not to

accept this prize; and there have been foolish paragraphs in the

papers to that effect; but if the two countries or governments

are at war, the men of science are not. That would, indeed, be

a civil war of the worst description: we should rather, through

the instrumentality of men of science, soften the asperities of

national hostility."

After Davy had been elected Secretary to the Royal Society, he

appears to have been confined to town during the autumn of 1807,

when he wrote the following letter.

TO THOMAS POOLE, ESQ.

August 28th, 1807.

MY DEAR POOLE,

I am obliged to be in the neighbourhood of town during the greater

part of the summer, for the purpose of correcting the press for

the Philosophical Transactions.

I made a rapid journey into Cornwall for the sake of seeing my

family; and it was not in my power, had I received your letter at

Lyme, to have accepted your kind invitation.

If C---- is still with you, will you be kind enough to say to him,

that I wrote nearly a week ago two letters about lectures, and not

knowing where he was, I addressed them to him at different places?

I wish very much he would seriously determine on this point. The

Managers of the Royal Institution are very anxious to engage him;

and I think he might be of material service to the public, and

of benefit to his own mind, to say nothing of the benefit his

purse might also receive. In the present condition of society,

his opinions in matters of taste, literature, and metaphysics,

must have a healthy influence; and unless he soon become an actual

member of the living world, he must expect to be hereafter brought

to judgment 'for hiding his light.'

The times seem to me to be less dangerous, as to the immediate

state of this country, than they were four years ago. The extension

of the French Empire has weakened the disposable force of France.

Bonaparte seems to have abandoned the idea of invasion; and if our

Government is active, we have little to dread from a maritime war,

at least for some time. Sooner or later, our Colonial Empire must

fall in due time, when it has answered its ends.

The wealth of our island must be diminished, but the strength of

mind of the people cannot easily pass away; and our literature,

our science, our arts, and the dignity of our nature, depend little

upon our external relations. When we had fewer colonies than Genoa,

we had Bacons and Shakspeares.

The wealth and prosperity of the country are only the _comeliness_

of the body--the fulness of the flesh and fat;--but the spirit is

independent of them; it requires only muscle, bone, and nerve, for

the true exercise of its functions. We cannot lose our liberty,

because we cannot cease to _think_; and ten millions of people are

not easily annihilated.

I am, my dear Poole, very truly yours,

H. DAVY.

While the Electro-chemical laws, developed in the last chapter,

are fresh in the recollection of the reader, I shall proceed to

the consideration of his second Bakerian Lecture, which was read

in November 1807; and in which he announces the discovery of the

metallic bases of the fixed alkalies,--a discovery immediately

arising from the application of Voltaic electricity, directed in

accordance with those laws;--thus having, as we have seen in the

first instance, ascended from particular phenomena to general

principles, he now descends from those principles to the discovery

of new phenomena: a method of investigation by which he may be said

to have applied to his inductions the severest tests of truth, and

to have produced a chain of evidence without having a single link

deficient.

Since the account given by Newton of his first discoveries in

Optics, it may be questioned whether so happy and successful an

instance of philosophical induction has ever been afforded as that

by which Davy discovered the composition of the fixed alkalies.

Had it been true, as was most unjustly insinuated at the time,

that the discovery was accidentally effected by the high power of

the apparatus placed at his disposal, his claims to our admiration

would have assumed a very different character: in such a case,

he might be said to have forced open the sanctuary of Nature by

direct violence, instead of having discovered and touched the

secret spring by which its portals were unclosed. The justice of

these remarks will best appear in the examination of his memoir:

the highest eulogy that can be conferred on its author will be a

faithful and plain history of its contents.

It will be remembered that, in his preceding lecture of 1806, he

had described a number of decompositions and chemical changes

produced in substances of known composition, by the powers of

electricity, and that in all such cases there invariably subsisted

an attraction between oxygen and the _positive_ pole, and between

inflammable matter and the _negative_ pole of the pile: thus,

in the decomposition of water, its oxygen was transferred to

the former, and its hydrogen to the latter. Furnished with such

data, Davy proceeded to submit a fixed alkali to the most intense

action of the Voltaic apparatus, well convinced that, should the

electrical energy be adequate to effect its decomposition, the

elements would be transferred, according to this general law, to

their respective poles.

His first attempts were made on solutions of the alkalies; but,

notwithstanding the intensity of the electric action, the

water alone underwent decomposition, and oxygen and hydrogen

were disengaged with the production of much heat, and violent

effervescence. The presence of water thus appearing to prevent the

desired decomposition, potash, in a state of igneous fusion, was

in various ways submitted to experiment; when it was evident that

combustible matter of some kind, burning with a vivid light, was

given off at the negative wire. After numerous trials, during the

progress of which the difficulties which successively arose were

as immediately combated by ingenious manipulation, a small piece

of potash sufficiently moistened, by a short exposure to the air,

to give its surface a conducting power, was placed on an insulated

disc of platina, connected with the negative side of the battery in

a state of intense activity, and a platina wire communicating with

the positive side, was at the same instant brought into contact

within the upper surface of the alkali.--Mark what followed!--A

series of phenomena, each of which the reader will readily

understand as it is announced,--for it will be in strict accordance

with the laws which Davy had previously established:--the potash

began to fuse at both its points of electrization: a violent

effervescence commenced at the upper, or positive surface; while

at the lower, or negative one, instead of any liberation of

elastic matter, which would probably have happened had hydrogen

been an element of the alkaline body, small globules, resembling

quicksilver, appeared, some of which were no sooner formed than

they burnt with explosion and bright flame.--What must have been

the sensations of Davy at this moment!--He had decomposed potash,

and obtained its base in a metallic form.

The gaseous matter developed, during the experiment, at the

positive pole of the apparatus, he very shortly identified as

oxygen. To collect, however, the metallic matter, in a quantity

sufficient for a satisfactory examination, was by no means so easy;

for, like the _Alkahest_ imagined by the Alchemist, it acted more

or less upon every body to which it was exposed; and such was its

attraction for oxygen, that it speedily reverted to the state of

alkali by recombining with it.

After various trials, however, it was found that recently distilled

naphtha presented a medium in which it might be preserved and

examined, since a thin transparent film of this fluid, while it

defended the metal from the action of the atmosphere, did not

oppose any obstacle to the investigation of its physical properties.

Thus provided, he proceeded to enquire into the nature of the

new and singular body, to which he afterwards gave the name of

POTASSIUM, and which may be described as follows.

Its external character is that of a white metal, instantly

tarnishing by exposure to air; at the temperature of 70° Fah.

it exists in small globules, which possess the metallic lustre,

opacity, and general appearance of quicksilver; so that when a

globule of the latter is placed near one of the former, the eye

cannot discover any difference between them: at this temperature,

however, the metal is not perfectly fluid; but when gradually

heated, it becomes more so,--and at 150°, its fluidity is so

perfect that several globules may be easily made to run into

one. By reducing its temperature, it becomes, at 50°, a soft and

malleable solid, which has the lustre of polished silver, and is

soft enough to be moulded like wax. At about the freezing point of

water it becomes hard and brittle, and exhibits, when broken, a

crystallized structure of perfect whiteness, and of high metallic

splendour. It is also a perfect conductor both of electricity and

heat. Thus far, then, it fulfills every condition of a metal;

but an anomaly of a most startling description has now to be

mentioned--the absence of a quality which has been as invariably

associated with the idea of a metal, as that of lustre, viz. great

specific gravity. Whence a question has arisen, whether, after

all, the alkaline base can with propriety be classed under that

denomination? Instead of possessing that ponderosity which we

should have expected in a body otherwise metallic, it is so light

as not only to swim upon the surface of water, but even upon that

of naphtha, by far the lightest liquid in nature. Davy, however,

very justly argues, that low specific gravity does not offer a

sufficient reason for degrading this body from the rank of a metal;

for amongst those which constitute the class, there are remarkable

differences with respect to this quality; that platina is nearly

four times as heavy as tellurium. In the philosophical division

of bodies into classes, the analogy between the greater number of

properties must always be the foundation of arrangement.[71]

[71] The propriety, and even the necessity, of such a compact

become daily more apparent, as our knowledge of bodies

extends. If we were to degrade a substance from its class, in

consequence of the absence of some one quality which enters

into its more perfect examples, we should soon find ourselves

involved in paradoxes.--What idea, for instance, could we form

of an acid?--Its sourness?--Prussic Acid--Arsenious Acid, are

not sour.--Its tendency to combine with an alkaline or earthy

base?--If so, sugar is an acid, for it combines with lime. I

remember a chemist having been exposed to much ridicule from

speaking of a _sweet_ acid--Why not?

So inseparable however, by long association, are the ideas of

ponderosity and metallic splendour, that the evidence even of the

senses may fail in disuniting them.[72] This is well illustrated

by the following amusing anecdote. Shortly after the discovery of

potassium, Dr. George Pearson happened to enter the laboratory in

the Royal Institution, and upon being shown the new substance, and

interrogated as to its nature, he, without the least hesitation, on

seeing its lustre, exclaimed, "Why, it is metallic, to be sure,"

and then, balancing it on his finger, he added, in the same tone of

confidence, "_Bless me, how heavy it is!_"

[72] In the language of Darwin, we should say, that the simple

ideas of weight and lustre, which form the complex idea of a

metal, have become so indissoluble, that they can no longer be

separated by volition. The principle admits of many familiar

illustrations, and is the source of numerous fallacies. When any

one voluntarily recollects a Gothic window, which he had seen

some time before, the whole front of the Cathedral occurs to him

at the same time: in like manner, the taste of a pine-apple,

though we eat it blindfold, recalls the colour and shape of it.

Coleridge has made a good remark upon this subject. He says, "It

is a great law of the imagination, that a likeness in part tends

to become a likeness of the whole." It is thus that we trace

images in the fire, castles in the clouds, and spectres in the

gloom of twilight.

When thrown upon water, potassium instantly decomposes that fluid,

and an explosion is produced with a vehement flame: an experiment

which is rendered more striking if, for water, ice be substituted;

in this latter case, it instantly bums with a bright rose-coloured

flame, and a deep hole is made in the ice, which will afterwards be

found to contain a solution of potash.

It is scarcely necessary to state, that these phenomena depend

upon the very powerful affinity which the metal possesses for

oxygen, enabling it even to separate it from its most subtle

combinations.[73]

[73] If we are disposed to enter into a more critical examination

of the subject, we shall find that, although the above is a

general expression of the change produced, there are subordinate

actions of a more complicated nature: the metal, in the first

place, decomposes a portion of the water, in order to combine

with its oxygen, and form potash, which in its turn has a

powerful affinity for water; the heat arising from two causes,

decomposition and combination, is sufficiently intense to produce

the inflammation. Water is a bad conductor of heat; the globule

swims exposed to air; a part of which is dissolved by the heated

nascent hydrogen; and this gas, being capable of spontaneous

inflammation, explodes and communicates the effect of combustion

to any of the bases that may be yet uncombined. The manner in

which the potassium runs along the surface of water may be

compared to a drop of water on red-hot iron; in the one case the

hot potassium, in the other the cold water, is enveloped in an

atmosphere of steam.

One of the neatest modes of showing the production of alkali,

in the decomposition of water by the basis of potash, consists

in dropping a globule of potassium upon moistened paper tinged

with turmeric. At the moment that it comes into contact with the

water, it burns and moves rapidly upon the paper, as if in search

of moisture, leaving behind it a deep reddish-brown trace of its

progress, and acting upon the test paper precisely as dry caustic

potash.

From these observations, the reader will immediately perceive,

that the decomposition of the fixed alkalies has placed in the

hands of the experimentalist a new instrument of research, scarcely

less energetic, or of less universal application, than the power

from which the discovery emanated. Davy observes upon this point,

that "it will undoubtedly prove a powerful agent for analysis,

and having an affinity for oxygen, stronger than any other known

substance, it may possibly supersede the application of electricity

to some of the undecompounded bodies." So strong indeed is its

affinity for oxygen, that it discovers and decomposes the small

quantities of water contained in alcohol and ether; and in the

latter case, this decomposition is connected with an instructive

result. Potash is insoluble in that fluid: when therefore its base

is thrown into it, oxygen is furnished, hydrogen gas disengaged,

and the alkali, as it is regenerated, renders the ether white and

turbid.

But perhaps the most beautiful illustration of its deoxidizing

power is afforded by its action on carbonic acid gas, or fixed

air: when heated in contact with that gas, it catches fire, and by

uniting with its oxygen, becomes potash, while the liberated carbon

is deposited in the form of charcoal.

As I have already exceeded the limits originally prescribed to

myself, I shall not enter into the history of Davy's experiments

on the other fixed alkali, soda, farther than to state that, when

it was submitted to Voltaic action, a bright metal was obtained,

similar in its general characters to potassium, but possessing

sufficiently distinctive peculiarities as to volatility,

fusibility, oxidability, &c. To this body Davy assigned the name of

SODIUM.[74]

[74] In his Bakerian Lecture of 1810, he informs us that he

obtains Sodium by heating common salt, which has been previously

ignited, with Potassium--an immediate decomposition takes place,

and two parts of Potassium produce rather more than one of Sodium.

In support of the metallic characters of these alkaline bases,

it may be necessary to state that they combine with each other,

and form alloys; the properties and habitudes of which are very

interesting, and are fully described by their discoverer.

No sooner had these results been made known to the scientific

world, than a question arose, both in this country and abroad, as

to the real nature of the bodies which had been thus obtained from

the fixed alkalies, and which presented an aspect so obviously

metallic. At first, it was conjectured by a few, that they might be

compounds of the alkali with the platina used in the experiments;

but this was at once disproved by Davy having obtained the same

results when pieces of copper, silver, gold, plumbago, or even

charcoal, had been employed for completing the Voltaic circuit.

The effect which this and his subsequent discoveries produced, in

revolutionizing the theory of Chemistry, will form an interesting

subject for discussion in a future part of the present work: I

shall therefore only remark in passing, that the fact of oxygen,

the acknowledged principle of acidity, existing in combination with

a metallic base, and imparting to it the properties of an alkali,

was no sooner announced, than its truth was strenuously denied. It

was an attack upon opinions sanctioned by the general suffrage

of the scientific world;--it was, in fact, storming the very

citadel of their philosophy: no wonder, then, that the agitator

should have been assailed with a full cry for his revolutionary

plans.[75] M. Curadau read a paper before the French Institute,

in which he endeavoured to prove, _first_, that the conversion of

the alkalies into metals was not a deoxidation of those bodies,

but a combination of them with new elements;--_secondly_, that the

affinity of the alkaline metals for oxygen was merely a chemical

illusion, occasioned by some body the presence of which had not

been suspected;--_thirdly_, that carbon was one of the elements

of the alkaline metals, since it could be separated from them at

pleasure, or converted into carbonic acid;--and _fourthly_, that if

the specific gravities of the new substances were less than that of

water, it was because hydrogen was associated with carbon in the

combination.

[75] Many years afterwards, when Davy was travelling on the

Continent, a distinguished person about a foreign court, enquired

who and what he was; never having heard of his scientific

fame. Upon being told that his discoveries had revolutionized

Chemistry, the courtier promptly replied--"I hate all

revolutionists--his presence will not be acceptable here."

It is scarcely necessary to state, that the presence of carbon was

readily traced to sources of impurity. The hypothesis which assumed

the existence of hydrogen as an element, was not so easily refuted.

It was espoused by MM. Gay Lussac, Thénard, and Ritter, on the

Continent, and by Mr. Dalton in England. The former derived their

inference from the action of potassium upon ammonia, by which

they obtained a fusible substance that yielded by heat more

hydrogen than the ammonia contained; the latter contended that

potassium and sodium are proved to be _hydrurets_, by the very

process employed for their production; for, since common potash is

a _hydrat_, and oxygen is produced at one surface, and potassium

at the other, by Voltaic action, he conceived that the former

arose from the decomposition of water, and that the hydrogen

must therefore unite with the potash to form potassium. It is a

curious fact, that Berthollet, in the very sentence in which he

insisted upon the excessive quantity of hydrogen disengaged in

his experiment, as a proof that potassium must be a _hydruret_,

should have stated that the addition of water to the residuum was

necessary for obtaining his result. How could it have happened

that he overlooked so obvious a source of hydrogen? Mr. Dalton, as

well as Ritter, considered the low specific gravity as favouring

the idea of their containing hydrogen; but Davy observes that they

are less volatile than antimony, arsenic, and tellurium, and much

less so than mercury. Besides, sodium absorbs much more oxygen

than potassium, and, on the hypothesis of hydrogenation, must

therefore contain more hydrogen; and yet though soda is said to be

lighter than potash, in the proportion of thirteen to seventeen

nearly, sodium is heavier than potassium, in the proportion of

nine to seven at least. On the theory of Davy, this circumstance

is what ought to have been expected. Potassium has a much stronger

affinity for oxygen than sodium, and must condense it much more;

and the resulting higher specific gravity of the combination is

a necessary consequence. In this manner did Davy entangle his

opponents in their own arguments, and establish, in the most

triumphant manner, the truths of his original views.

Thus then was a discovery effected, and at once rendered

complete, which all the chemists in Europe had vainly attempted

to accomplish. The alkalies had been tortured by every variety of

experiment which ingenuity could suggest, or perseverance perform,

but all in vain; nor was the pursuit abandoned until indefatigable

effort had wrecked the patience and exhausted every resource of the

experimentalist. Such was the disheartening, and almost forlorn

condition of the philosopher when Davy entered the field:--he

created new instruments, new powers, and fresh resources; and

Nature, thus interrogated on a different plan, at once revealed her

long cherished secret.

In his Bakerian Lecture, Davy observes, that "a historical detail

of the progress of the investigation of all the difficulties that

occurred, and of the manner in which they were overcome, and of all

the manipulations employed, would far exceed the limits assigned

to a Lecture." But to the chemist, every circumstance, however

minute, connected with a subject of such commanding importance, is

pregnant with interest; I therefore considered it my duty to search

into the archives of the Institution, in the hope that I should

discover some memoranda which might supply additional information.

In examining the Laboratory Register, I have so far succeeded as to

obtain some rough and imperfect notes, which will, to a certain

degree, assist us in analysing the intellectual operations by which

his mind ultimately arrived at the grand conclusion.

It appears from this register that Davy commenced his enquiries

into the composition of potash on the 16th, and obtained his great

result on the 19th of October 1807.[76] His first experiments,

however, evidently did not suggest the truth: he does not appear

to have suspected the nature of the alkaline base until his last

experiment, when the truth flashed upon him in the full blaze of

discovery. His first note, dated the 16th, leads us to infer that

he acted on a solid piece of potash, under the surface of alcohol,

and several other liquids in which the alkali was not soluble; and

that he obtained gaseous matter, which he called at the moment

'_Alkaligen Gas_,' and which he appears to have examined most

closely, without arriving at any conclusion as to its nature. On

the following day, he, for the first time, would seem to have

developed potassium by electric action on potash under oil of

turpentine, for the note records the fact of "_the_ globules giving

out gas by water, which gas _burnt in contact with air_;" and then

follows a query--"Does _it_" (the matter of the globules) "not form

gaseous compounds with ether, alcohol, and the oils?" Here, then,

he evidently imagined, that the matter of the globules, which he

had never obtained from potash, except when acted upon under oil of

turpentine, had formed gaseous compounds with the ether, alcohol,

and oils in his previous experiments, and given origin to that

which he had termed '_Alkaligen Gas_.'

[76] On the same day he decomposed Soda with somewhat different

phenomena.

He then leaves the consideration of this gas, and attacks the

unknown globules, which probably did not present any metallic

appearance under the circumstances in which he saw them, for they

must have been as minute as grains of sand. I rather think that he

commenced his examination by introducing a globule of mercury, and

uniting it with a globule of the unknown substance, for his note

says, "Action of the substance on Mercury,--forms with it a solid

amalgam, which soon loses its _Alkaligen_ in the air." And from

the note which succeeds, he evidently considered this _Alkaligen_

(potassium) volatile, as he says "it soon flies off on exposure to

the air."

October 19.--It is probable that, in consequence of the property

which the unknown substance displayed of amalgamating with mercury,

he devised his experiment of the 19th. He took a small glass tube,

about the size and shape of a thimble, into which he fused a

platinum wire, and passed it through the closed end. He then put a

piece of pure potash into this tube, and fused it into a mass about

the wire, so as entirely to defend it from the mercury afterwards

to be used. When cold, the potash was solid, but containing

moisture enough to give it a conducting power; he then filled the

rest of the tube with mercury, and inverted it over the trough:

the apparatus being thus arranged, eurêka he made the wire and the

mercury alternately positive and negative. And now, conceiving

that I have sufficiently explained his brief notes, the reader

shall receive the result in his own words: for this purpose I have

obtained an engraving of the autograph, which is here annexed;

but as it may not be very readily deciphered, I shall first give

the substance of it in print.--"When potash was introduced into a

tube having a platina wire attached to it--so--and fused into the

tube so as to be a conductor, _i. e._ so as to contain just water

enough, though solid, and inserted over mercury, when the platina

was made negative, no gas was formed, and the mercury became

oxydated, and a small quantity of the _alkaligen_ was produced

round the platina wire, as was evident from its quick inflammation

by the action of water. When the mercury was made the negative,

gas was developed in great quantities from the positive wire,

and none from the negative mercury, and this gas proved to be

pure oxygene--A CAPITAL EXPERIMENT, PROVING THE DECOMPOSITION OF

POTASH." The Reviewer of the Institution Journal well observes that

those who knew Davy will best conceive the enthusiasm with which

this hasty record of his success was dashed off, and will instantly

recognise [Greek: eurêka] in his "CAPITAL EXPERIMENT."

From this same Register, it appears that, in the preceding month,

he was deeply engaged in experiments on '_Antwerp blue_,' which he

found to consist of _Prussiate of Iron_ and _Alumina_, "probably

in the proportion of two-thirds of the former to one-third of the

latter."

On the 6th of October, we learn from the same source, that he

performed a beautiful experiment, that of producing the vegetation

of the carbon of the wick of a candle, by placing it between the

wires of the battery.

On the 12th of the preceding September he addressed a letter to

Mr. Gilbert, which is curious, as it shows that very nearly up to

the time of the decomposition of the alkalies, his mind had been

engaged on very different subjects.

TO DAVIES GIDDY, ESQ.

September 12, 1807.

MY DEAR SIR,

I inclose Mr. Carne's paper, which, when you have read, and Mr.

Carne revised, I will thank you to inclose to me, and that as soon

as possible, for the completion of the volume.

I have been a good deal engaged, since my return, in experiments on

distillation, and I have succeeded in effecting what is considered

of great importance in colonial commerce, namely, the depriving rum

of its empyreumatic part, and converting it into pure spirit.

I mention this in confidence, as it is likely to be connected with

some profitable results; and it may be beneficial in a public point

of view, by lessening the consumption of malt.

I have heard of no scientific news; this, indeed, is little the

season for active exertion.

With best respects to your father, and to Mr. and Mrs. Guillemard,

I am, my dear Sir,

Always very faithfully yours,

H. DAVY.

Few notes have conveyed information of such importance to the

scientific world, as that which follows, announcing, at the same

time, the decomposition of the fixed alkalies, and the formation of

the Geological Society, of which it would thus appear that Davy was

one of the founders.

TO WILLIAM HASLEDINE PEPYS, ESQ.

November 13, 1807.

DEAR PEPYS,

If you and Allen had been one person, the Council of the Royal

Society would have voted to you the Copleian Medal;[77] but it is

an indivisible thing, and cannot be given to two.

We are forming a little talking Geological Dinner Club, of which I

hope you will be a member. I shall propose you to-day. Some things

have happened in the Chemical Club, which I think render it a less

desirable meeting than usual, and I do not think you would find any

gratification in being a member of it. Hatchett never comes, and we

sometimes meet only two or three. I hope to see you soon.

I have decomposed and recomposed the fixed alkalies, and discovered

their bases to be two new inflammable substances very like metals;

but one of them lighter than ether, and infinitely combustible. So

that there are two bodies decomposed, and two new elementary bodies

found.

Most sincerely yours,

H. DAVY.

[77] He alludes to a Paper, entitled "On the Quantity of

Carbon in Carbonic Acid, and on the Nature of the Diamond; by

William Allen, Esq. F.R.S. and William Hasledine Pepys, Esq."

Communicated by Humphry Davy, Sec. R.S. M.R.I.A. Read June 16,

1807.

In the year 1808, MM. Gay Lussac and Thénard succeeded in

decomposing potash by chemical means; for which purpose it is

only necessary to heat iron turnings to whiteness in a curved

gun-barrel, and then to bring melted potash slowly in contact

with the turnings, air being excluded; when the iron, at that

high temperature, will take the oxygen from the alkali, and the

potassium may be collected in a cool part of the tube. It may

likewise be produced by igniting potash with charcoal, as M.

Curaudau showed in the same year.

In the following letter, Davy gives an account of his repeating

the experiment of MM. Gay Lussac and Thénard; mixing together, as

usual, science and angling.

TO J. G. CHILDREN, ESQ.

London, July 1808.

MY DEAR SIR,

I have this moment received your kind letter, and I have written

to Pepys to propose to him to be with you on Sunday or Monday. I

hope for his answer to-morrow morning, and I will write to you

immediately.

I will procure all the fishing tackle you have proposed, and am

most happy to find you in so determined a spirit for piscatory

adventure.

I have had some letters from France; but nothing new, except an

account of the gun-barrel experiment tolerably minute. I have

tried it since, and procured potassium, but it was lost from

some moisture passing into the aperture of the barrel. All that

is necessary for the process is a gun-barrel bent thus, thus,

B\______/\_/A.---- B represents the part where the touch-hole is

closed; here dry potash is introduced; and the middle, which is to

be strongly ignited, contains the filings; the potash is gradually

fused and made to run down upon the ignited iron; the potassium

collects in A.

If you should be able to procure the apparatus for this experiment,

I should like to assist in repeating it; and could we procure a

large quantity of the basis, we may try its effects, on a great

scale, on the undecompounded acids. I will bring some _dry boracic

acid_. A copper or platina tube, if you have one, will be proper

for trying the experiment in. We may likewise try its action upon

the earths, and upon diamond.

I have metallized Ammonia,[78] without the application of

Electricity. When an amalgam of potassium and mercury is brought

in contact with an ammoniacal salt, the potassium seizes upon the

oxygen, and the hydrogen and nitrogen unite to the quicksilver.

I had an opportunity of giving an account, on Friday, to the

scientific men assembled at Greenwich, of your magnificent

experiments and apparatus.[79] Sir Joseph Banks, Mr. Cavendish,

Wollaston, &c. all expressed a strong wish that the results should

be published. I am most happy you have drawn up the account.

I regard the days I have passed in your society, as some of the

pleasantest of my life. I look forward with a warm hope to our next

meeting. Be pleased to assure your father of my highest respect,

and of my gratitude for his kindness.

I am, my dear Sir,

Very sincerely yours,

H. DAVY.

[78] He here alludes to a train of research, which will be

considered hereafter.

[79] This observation relates to the magnificent battery

constructed by Mr. Children, of which he presented an account to

the Royal Society, in a Paper read in November 1808, entitled,

"An Account of some Experiments, performed with a view to

ascertain the most advantageous Method of constructing a Voltaic

Apparatus, for the purpose of Chemical Research. By John George

Children, Esq. F.R.S." The great battery described in this Paper

consisted of twenty pairs of plates, each plate being four feet

high by two feet wide: the sum of all the surfaces was ninety-two

thousand one hundred and sixty square inches, and the quantity of

liquid necessary for charging it, one hundred and twenty gallons.

At the same time he constructed another battery, which consisted

of two hundred pairs of plates, each being only two inches

square. In the one case, then, he commanded extent of surface,

in the other, extent of number; and by a series of comparative

experiments, he fully established the theory of Davy (page 246),

that the _intensity_ of Electricity increases with the _number_,

and the _quantity_ with the _surface_.

It is impossible to reflect upon the chemical processes by which

potassium may be obtained, without feeling surprised that the

discovery should not have long before been accomplished. It is

evident that the substance must have been repeatedly developed

during the operations of chemistry; alkalies had been frequently

heated to whiteness in contact both with iron and charcoal, and in

some instances the appearance of a highly combustible body, which

could have been no other than potassium, had even been observed

as a result of the process, and yet no suspicion, as to its real

nature, ever crossed the mind of the experimentalist; he satisfied

himself with designating such a product, whenever it occurred, by

the term _Pyrophorus_.[80] I remember the late Mr. William Gregor

informing me that, in the course of his analytical experiments

with potash and different metals, he had repeatedly observed a

combustion on removing the crucible from the furnace, and exposing

its contents, which he could never understand. How admirably do

such anecdotes illustrate the remark made in the commencement of

the present chapter, that truth may be often touched, but is rarely

caught, in the dark!

[80] The Pyrophorus of Homberg, of which a description is to

be found in the _Mémoires de l'Academie_, for 1711, was made

by mixing together any combustible body, as gum, flour, sugar,

charcoal, &c. and alum, and then, after roasting the mixture till

it was reduced to a dry powder, exposing it in a matrass to a red

heat. In this process, the theory of which was first explained by

Davy, the potash of the alum is converted into potassium, which,

by its absorption of oxygen from the atmosphere, generates heat,

and sets fire to the charcoal contained in the powder.

The facility of the combustion of the bases of the alkalies, and

the readiness with which they decomposed water, offered Davy the

ready means for determining the proportions of their constituent

parts: and in comparing all his results, he thinks that it will be

a good approximation to the truth, to consider potash as composed

of about six parts base and one of oxygen; and soda, as consisting

of seven base and two of oxygen.

The discovery of potassium led to that of the true nature of what

had been long familiar to chemists by the name of _pure Potash_,

but which ought to have been called the _hydrat_, for the _pure_

alkali was not known until after the discovery of Davy. The

experiments of MM. Gay Lussac and Thénard have shown this substance

to be a _Protoxide_. It is difficult of fusion; it has a grey

colour and a vitreous fracture, and dissolves in water with much

heat. The _Peroxide_ is procured by the combustion of potassium at

a low temperature; it had been observed by Davy in October 1807,

but at that time he supposed it to be the oxide containing the

smallest proportion of oxygen: it has a yellow colour, and when

thrown into water effervesces, and gives out oxygen gas.[81] When

heated very strongly upon platina, oxygen is also expelled from it,

and there remains the _protoxide_, or pure potash.

[81] The 'Potassa Fusa' of our Pharmacopoeia generally contains a

small proportion of the peroxide, and will therefore effervesce

when thrown into water.

It was a great object with Davy, to show that the product resulting

from the combustion of potassium, was a pure oxide free from

water; for it is evident that had potassium been a _Hydruret_, its

combustion must have produced a _Hydrat_. This he accomplished by a

series of experiments which he performed in the laboratory of Mr.

Children, and which are published in his Bakerian Lecture of 1800.

Having discovered the presence of oxygen in the fixed alkalies, he

was naturally led by analogy to enquire whether ammonia might not

also contain it. It was true that the chemical composition of that

body had been considered as satisfactorily settled, and that the

conversion of it into hydrogen and nitrogen, in the experiments of

Scheele, Priestley, and Berthollet, had left nothing farther to be

accomplished. All new facts, however, are necessarily accompanied

by a new train of analogies; and Davy, in perusing the accounts of

the various experiments to which ammonia had been submitted, tells

us that he saw no reason for considering the presence of oxygen

as impossible; for, supposing hydrogen and nitrogen to exist in

combination with oxygen in low proportion, this latter principle

might easily disappear in the analytical experiments by heat and

electricity, in the form of water deposited upon the vessels

employed, or dissolved in the gases produced.

Under this impression, he commenced a series of experiments by

which, he says, he soon became satisfied of the existence of oxygen

in the volatile alkali. By means of the Voltaic battery, he ignited

perfectly dry charcoal in a small quantity of pure ammoniacal

gas, and he produced carbonate of ammonia; which could not have

happened, had not oxygen been furnished by the volatile alkali

to the carbon. In the next place, by an ingenious arrangement of

apparatus, he submitted ammonia to a high temperature, and effected

its decomposition, when a quantity of water appeared as one of the

products. It will be useless to enter into farther details upon

this occasion, as we shall presently perceive the subject assumed

a different aspect, and led the experimentalist into a new line of

enquiry.

At the conclusion of his Bakerian Lecture of 1807, he speaks of the

probable composition of the earths, and considers it reasonable to

expect that they are compounds of a similar nature to the fixed

alkalies--"peculiar highly combustible metallic bases united to

oxygen;"--but, as yet, this theory was sanctioned only by strong

analogies; it was his good fortune, at a subsequent period, to

support it by conclusive facts.

When the importance and novelty of the results he obtained from the

fixed alkalies, and their influence upon the reigning theories,

are duly considered, it may be easily imagined how intense was

the curiosity to witness the production of the new metals, to

examine their singular qualities, and to question the illustrious

discoverer upon their nature and relations. Suppose it were

publicly announced that one of the greatest Astronomers of the

day had invented a telescope of new and extraordinary powers;

and that by its means a hitherto unsuspected system of heavenly

bodies might be seen, the character and motions of which were

wholly inconsistent with the Newtonian theory of the universe.

The surprise and eager curiosity which such an announcement would

create might possibly be more general, because a knowledge of

Astronomy is more widely diffused than that of Chemistry; but the

sensation would not be more intense than that which the discovery

of potassium produced. The laboratory of the Institution was

crowded with persons of every rank and description; and Davy,

as may be readily supposed, was kept in a continued state of

excitement throughout the day. This circumstance, co-operating with

the effects of the fatigue he had previously undergone, produced a

most severe fit of illness, which for a time caused an awful pause

in his researches, broke the thread of his pursuits, and turned his

reflections into different channels.

He always laboured under the impression that the fever had been

occasioned by contagion, to which he had been exposed in one of

the jails during an experiment for fumigating it. This impression

appears to have continued through life, for in his "Last Days" he

alludes to it in terms of strong conviction.

Other persons referred his illness to the deleterious fumes,

especially those of Baryta, to which his experiments had exposed

him: an opinion recorded in an Epigram,[82] which was circulated

amongst the members of the Institution after his recovery.

Says Davy to Baryt, "I've a strong inclination

To try to effect your deoxidation;"

But Baryt replies--"Have a care of your mirth,

Lest I should retaliate, and change _you_ to Earth."

[82] I received the above _jeu d'esprit_ from the late learned

Orientalist, Mr. Stephen Weston, only four days before his death.

Since its publication in the first edition of this work, a

chemical friend sent me the following improved version of it.

Says Davy to Baryt, "I feel strong temptation

To effect by my art your deoxidation;

And the money I've got in my pocket I'll bet all,

I prove you a true, though disguised lad of metal."

Says Baryt to Davy, "A truce to your mirth;

If you turn me to metal, I'll turn you to earth;

So moisten your clay, don't improve Science daily,

Nor treat me as you've treated poor Soda and Kali."

Upon conversing, however, with Dr. Babington, who, with Dr.

Frank, attended Davy throughout this illness, he assured me

that there was not the slightest ground for either of these

opinions; that the fever was evidently the effect of fatigue and

an over-excited brain. The reader will not feel much hesitation

in believing this statement, when he is made acquainted with the

habits of Davy at this period. His intellectual exertions were of

the most injurious kind, and yet, unlike the philosophers of old,

he sought not to fortify himself by habits of temperance. Should

any of my readers propose to me the same question respecting

Davy, as Fontenelle tells us was put to an Englishman in Paris,

by a scientific Marquis, with regard to Newton,--whether he ate,

drank, and slept like other people?--I certainly should be bound

to answer in the negative.

Such was his great celebrity at this period of his career, that

persons of the highest rank contended for the honour of his

company at dinner, and he did not possess sufficient resolution

to resist the gratification thus afforded, although it generally

happened that his pursuits in the laboratory were not suspended

until the appointed dinner-hour had passed. On his return in the

evening, he resumed his chemical labours, and commonly continued

them till three or four o'clock in the morning; and yet the

servants of the establishment not unfrequently found that he

had risen before them. The greatest of all his wants was Time,

and the expedients by which he economised it often placed him

in very ridiculous positions, and gave rise to habits of the

most eccentric description: driven to an extremity, he would in

his haste put on fresh linen, without removing that which was

underneath; and, singular as the fact may appear, he has been

known, after the fashion of the grave-digger in Hamlet, to wear

no less than five shirts, and as many pair of stockings, at the

same time. Exclamations of surprise very frequently escaped

from his friends at the rapid manner in which he increased and

declined in corpulence.

At the commencement of his severe illness in November 1807, he

was immediately attended by Dr. Babington and Dr. Frank; and

upon its assuming a more serious aspect, these gentlemen were

assisted by Dr. Baillie. Such was the alarming state of the

patient, that for many weeks his physicians regularly visited him

four times in the day, and issued bulletins for the information

of the numerous enquirers who anxiously crowded the hall of the

Institution. His kind and amiable qualities had secured the

attachment of all the officers and servants of the establishment,

and they eagerly anticipated every want his situation might

require. The housekeeper, Mrs. Greenwood, watched over him with

all the care and solicitude of a parent; and, with the exception

of a single night, never retired to her bed for the period of

eleven weeks. In the latter stage of his illness, he was reduced

to the extreme of weakness, and his mind participated in the

debility of the body. It may not perhaps be thought philosophical

to deduce any inference, as to character, from traits which

are displayed under such circumstances: I have little doubt,

however, but that the mind, like inorganic matter, will, in its

decay, frequently develope important elements, which under other

conditions were not distinguishable. Suppose pride and timidity

to exist as qualities in the same mind, the former might so far

predominate as to enable its possessor to face the cannon's

mouth; but diminish its force by moral or physical agency, the

natural timidity will gain the ascendency, and the hero be

converted into a coward. Such are my reasons for introducing

the following anecdote: I would not give to it a greater value

than it deserves, but it surely demonstrates the existence of

kindly affections. Youthful reminiscences, and circumstances

connected with his family and friends, were the only objects

which, at this period, occupied his thoughts, and afforded him

any pleasure. No Swiss peasant ever sighed more deeply for his

native mountains, than did Davy for the scenes of his early

years. He entreated his nurse to convey to his friends his ardent

wish to obtain some apples from a particular tree which he had

planted when a boy; and, unlike Locke with his cherries, he had

no power of controlling the desire by his reason, but remained

in a state of restlessness and impatience until their arrival:

at the same time, he expressed a wish to obtain several other

objects, especially an ancient tea-pot, endeared to him by early

associations.

The following Minute appears on the Journals of the Institution:--

"December 7, 1807.--Mr. Davy having been confined to his bed for

the last fortnight by a severe illness, the Managers are under

the painful necessity of giving notice, that the Lectures will

not commence until the first week in January next."

The Course was, at the time stated, opened by the Reverend Mr.

(now Dr.) Dibdin; and his introductory lecture was, by order of

the Managers, printed "for the satisfaction of those proprietors

who were not present." It thus commences:--"Before I solicit your

attention to the opening of those Lectures which I shall have

the honour of delivering in the course of the season, permit me

to trespass upon it for a few minutes, by stating the peculiar

circumstances under which this Institution is again opened; and

how it comes to pass that it has fallen to me, rather than to a

more deserving lecturer, to be the first to address you.

"The Managers have requested me to impart to you that

intelligence, which no one who is alive to the best feelings

of human nature can hear without mixed emotions of sorrow and

delight.

"Mr. Davy, whose frequent and powerful addresses from this place,

supported by his ingenious experiments, have been so long and so

well known to you, has for these last five weeks been struggling

between life and death;--the effects of those experiments

recently made in illustration of his splendid discoveries, added

to consequent bodily weakness, brought on a fever so violent

as to threaten the extinction of life. Over him, it might

emphatically be said, in the language of our immortal Milton, that

----'Death his dart

Shook, but delayed to strike.'

Had it pleased Providence to have deprived the world of

any further benefit from his original talents and immense

application, there certainly has been already enough effected

by him to entitle his name to a place amongst the brightest

scientific luminaries of his country. That this may not appear an

unfounded eulogium, I shall proceed, at the particular request of

the Managers, to give you an outline of the splendid discoveries

to which I have just alluded; and I do so with the greater

pleasure, as that outline has been drawn in a very masterly

manner by a gentleman of all others perhaps the best qualified to

do it effectually."

The Lecturer then proceeded to take a general and rapid view of

his labours, which it is unnecessary to introduce in this place,

and concluded as follows:--

"This recital will be sufficient to convince those who have heard

it of the celebrity which the author of such discoveries has a

right to attach to himself; and yet no one, I am confident, has

less inclination to challenge it. To us, and to every enlightened

Englishman, it will be a matter of just congratulation, that

the country which has produced the two BACONS and BOYLE, has in

these latter days shown itself worthy of its former renown by the

labours of CAVENDISH and DAVY. The illness of the latter, severe

as it has been, is now abating, and we may reasonably hope that

the period of convalescence is not very remote."

Fortunately for the cause of Science--fortunately for the

interests of the Institution, the prediction of the learned

Lecturer was shortly verified.

The Institution, indeed, had already suffered from the calamity;

for, in a Report to the Visitors, dated January 25, 1808, it is

stated, that "there has been an excess of expenditure beyond

the receipts. Among the causes of diminished income may be

mentioned the postponement of the lectures, in consequence of

the lamented illness of the excellent Professor of Chemistry;

and among the items of increased expenditure, the extra expense

of the Laboratory, in which have been produced Mr. Davy's recent

discoveries, so honourable to the Royal Institution, and so

beneficial to the interests of science in every part of the

world."

This Report is succeeded by the following Minute:--

"February 22, 1808.--Mr. Davy attended at the request of the

Committee, and informed them that he should be able to commence

his course of Lectures on Electro-chemical science on Saturday

the 12th of March, at two o'clock; and those on Geology on

Wednesday evening, the 16th of that month."

The following letter to Mr. Poole announces the restoration

of his health, and communicates some other circumstances of

interest. Mr. Poole, it would appear, entertained doubts as to

whether Davy received the prize of France for his first or second

Bakerian Lecture, upon which point this letter sets him right.

TO THOMAS POOLE, ESQ.

March, 1808.

MY DEAR POOLE,

Many thanks for your kind letter. I have seen your friend Mr.

B---- for a minute, and, to use a geological term, I like his

_aspect_, and shall endeavour to cultivate his acquaintance.

I am exceedingly busy; my health is re-established; and I am

entering again into the career of experiment.

The prize which you congratulate me upon was given for my paper

of 1806, and not for my last discoveries, which will probably

excite more interest.

C----, after disappointing his audience twice from illness, is

announced to lecture again this week. He has suffered greatly

from excessive sensibility--the disease of genius. His mind is as

a wilderness, in which the cedar and the oak, which might aspire

to the skies, are stunted in their growth by underwood, thorns,

briars, and parasitical plants. With the most exalted genius,

enlarged views, sensitive heart, and enlightened mind, he will

be the victim of want of order, precision, and regularity. I

cannot think of him without experiencing the mingled feelings of

admiration, regard, and pity.

Why do you not come to London? Many would be happy to see you;

but no one more so than your very sincere friend, my dear Poole,

H. DAVY.

It is difficult to convey an adequate idea of the universal

interest which was excited by the lectures on Electro-chemical

Science, to which an allusion has been just made. The Theatre of

the Institution overflowed; and each succeeding lecture increased

the number of candidates for admission.

It is unnecessary, after what has been already stated, to

describe the masterly style in which he demonstrated and

explained those general laws which his genius had developed, or

to enumerate the beautiful and diversified experiments by which

he illustrated their application, in simplifying the more complex

forms of matter.

His evening lectures on Geology were equally attractive; and by a

method as novel as it was beautiful, he exhibited, by the aid of

transparencies, the structure of mountains, the stratification of

rocks, and the arrangements of mineral veins.

The Easter recess afforded him a few days of leisure, which from

the following note he appears to have devoted to his favourite

amusement.

TO W. H. PEPYS, ESQ.

April, 1808.

MY DEAR PEPYS,

Children has had the kindness to arrange our party, and we are

to meet him, at all events, on Tuesday at two o'clock, at Foot's

Cray.

I have proposed that we should leave town at about five or six

on Monday evening, sleep at Foot's Cray, and try the fly-fishing

there.

Will you arrange with Allen, whom we must initiate in the

vocation of the Apostles, as he wants nothing else to make him

perfect as a primitive Christian and a Philosopher?

I am, my dear Pepys,

Most affectionately yours,

H. DAVY.

Hitherto his passion for angling has only been noticed in

connection with his conversation and letters; I shall now present

to the reader a sketch of the philosopher in his fishing costume.

His whole suit consisted of green cloth; the coat having sundry

pockets for holding the necessary tackle: his boots were made of

caoutchouc, and, for the convenience of wading through the water,

reached above the knees. His hat, originally intended for a

coal-heaver, had been purchased from the manufacturer in its raw

state, and dyed green by some pigment of his own composition; it

was, moreover, studded with every variety of artificial fly which

he could require for his diversion. Thus equipped, he thought,

from the colour of his dress, that he was more likely to elude

the observation of the fish. He looked not like an inhabitant

o' the earth, and yet was on't;--nor can I find any object in

the regions of invention with which I could justly compare him,

except perhaps with one of those grotesque personages who, in the

farce of "The Critic," attend Father Thames on the stage, as his

two banks.

I shall take this opportunity of stating, that his shooting

attire was equally whimsical: if, as an angler, he adopted a

dress for concealing his person, as a sportsman in woods and

plantations, it was his object to devise means for exposing it;

for he always entertained a singular dread lest he might be

accidentally shot upon these occasions. When upon a visit to

Mr. Dillwyn of Swansea, he accompanied his friend on a shooting

excursion, in a broad-brimmed hat, the whole of which, with the

exception of the brim, was covered with scarlet cloth.

Notwithstanding, however, the refinements which he displayed in

his dress, and the scrupulous attention with which he observed

all the minute details of the art; if the truth must be told, he

was not more successful than his brother anglers; and here again

the temperament of Wollaston presented a characteristic contrast

to that of Davy. The former evinced the same patience and

reserve--the same cautious observation and unwearied vigilance

in this pursuit, as so eminently distinguished his chemical

labours. The temperament of the latter was far too mercurial:

the fish never seized the fly with sufficient avidity to fulfill

his expectations, or to support that degree of excitement which

was essential to his happiness, and he became either listless or

angry, and consequently careless and unsuccessful.--But it is

time to resume the thread of our chemical history.

It has been already stated, that Davy had no sooner decomposed

the fixed alkalies than he proceeded to effect an analysis of

the earths; but his results were indistinct: they could not,

like the alkalies, be rendered conductors of electricity by

fusion, nor could they be acted upon in solution, in consequence

of the strong affinity possessed by their bases for oxygen. The

pursuit of the enquiry then demanded more refined and complicated

processes, than those which had succeeded with potash and soda.

The only methods which held out any fair prospect of success

were those of operating by electricity upon the earths in some

of their combinations, or of converting them, at the moment

of their decomposition, into metallic alloys, so as to obtain

presumptive evidence of their nature and properties. Such, in

fact, was the line of enquiry in which Davy was deeply engaged,

when he received from Professor Berzelius of Stockholm a letter,

announcing the fact that he had, in conjunction with Dr.

Pontin, succeeded in decomposing baryta and lime, by negatively

electrising mercury in contact with them, and that, by such

means, he had actually obtained amalgams of the earths in

question.

Our philosopher immediately repeated the experiments, and with

perfect success. After which he completed a series of additional

experiments, which fully established the nature of these bodies,

and the analogies he had anticipated. These results formed the

subject of a memoir, which was read before the Royal Society on

the 30th of June 1808, and entitled, "Electro-chemical Researches

on the Decomposition of the Earths: with Observations on the

Metals obtained from them, and on the Amalgam of Ammonia."

He commences this paper by enumerating the several trials he

had made to effect the decomposition of these bodies; such as,

First, by electrifying them by iron wires under the surface of

naphtha, with a view to form alloys with iron and the metallic

bases of the earths. Secondly, by heating potassium in contact

with the alkaline earths, in the hope that this body might detach

the oxygen from them, in the same manner as charcoal decomposes

the common metallic oxides. Thirdly, by submitting various

mixtures of the earths and potash to Voltaic action, with the

idea that the potash and the earths might be deoxidated at the

same time, and entering into combination, form alloys. Fourthly,

by mixing together various earths with the oxides of tin, iron,

lead, silver, and mercury: a mode of manipulation suggested

by the results of his previous experiments on potassium, in

which he found that when a mixture of potash and the oxides of

mercury, tin, or lead, was electrified in the Voltaic circuit,

the decomposition was very rapid, and an amalgam, or an alloy of

potassium, was obtained; the attraction between the common metals

and the potassium apparently accelerating the separation of the

oxygen.

Supposing that a similar kind of action might assist the

decomposition of the alkaline earths, he proceeded to institute a

series of experiments upon that principle; and the results were

more satisfactory than those obtained by the preceding methods

of experimenting--a compound was obtained which acted upon water

with the evolution of hydrogen, producing a solution of the

earth, and leaving free the tin, or lead, with which its base may

be supposed to have been alloyed;--but in all such experiments

the quantity of the metallic basis produced must have been very

minute, and its character very questionable.

In this stage of the enquiry, Davy received the letter from

Professor Berzelius of Stockholm, the contents of which he

embodied in his memoir, accompanied with such observations as his

own information suggested.

"A globule of mercury, electrified by the power of a battery

consisting of five hundred pairs of double plates of six inches

square, weakly charged, was made to act upon a surface of

slightly moistened barytes, fixed upon a plate of platina. The

mercury gradually became less fluid, and after a few minutes was

found covered with a white film of barytes; and when the amalgam

was thrown into water, hydrogen was disengaged, the mercury

remained free, and a solution of barytes was formed.

"The result with lime, as these gentlemen had stated, was

precisely analogous.

"That the same happy methods must succeed with strontites and

magnesia, it was not easy to doubt, and I quickly tried the

experiment. From strontites I obtained a very rapid result; but

from magnesia, in the first trials, no amalgam could be procured.

By continuing the process, however, for a longer time, and

keeping the earth continually moist, at last a combination of the

bases with mercury was obtained, which slowly produced magnesia,

by absorption of oxygen from air, or by the action of water.

"All these amalgams I found might be preserved for a considerable

period under naphtha. In a length of time, however, they became

covered with a white crust under this fluid. When exposed to

air, a very few minutes only were required for the oxygenation

of the bases of the earths. In the water the amalgam of barytes

was most rapidly decomposed; that of strontites, and that of lime

next in order: but the amalgam from magnesia, as might have been

expected from the weak affinity of the earth for water, very

slowly changed: when, however, a little sulphuric acid was added

to the water, the evolution of hydrogen, and the production and

solution of magnesia, were exceedingly rapid, and the mercury

soon remained free."

In order, if possible, to procure the amalgams in quantities

sufficient for distillation, he combined the methods he had

employed in the first instance, with those pursued by Berzelius

and Pontin. "A mixture of the earth with red oxide of mercury was

placed on a plate of platina, a cavity was made in the upper part

of it to receive a globule of mercury, the whole was covered by a

film of naphtha, and the plate was made positive, and the mercury

negative, by a proper communication with the battery of five

hundred."

The amalgams thus procured were afterwards distilled in glass

tubes filled with the vapour of naphtha; by which operation

the mercury rose pure from the amalgam, and it was very easy

to separate a part of it; but the difficulty was to obtain a

complete decomposition, for to effect this, a high temperature

was required, and at a red heat the bases of the earths instantly

acted upon the glass, and became oxidated.

In the best result which Davy obtained in this manner, the

barytic basis appeared as a white metal of the colour of silver,

fixed at all common temperatures, but fluid at a heat below

redness, and volatile at a heat above it. Unlike the alkaline

bases, it would seem to be considerably heavier than water.

In extending these experiments to alumine, silex, zircone, &c.

after a most elaborate investigation, such results were not

obtained as justified the conclusion that they were, like the

other earths, metallic oxides; although, as far as they went,

they added to the probability of such analogy.

It will be remembered that, after the fixed alkalies had been

found to contain oxygen, Davy was very naturally led to enquire

whether ammonia might not also contain the same element, or be

an oxide with a binary base. In the communication from Professor

Berzelius, and Dr. Pontin, already alluded to, a most curious

experiment is related on what they consider the deoxidation

and amalgamation of the compound basis of ammonia; and which

they regard as supporting the idea which Davy had formed of

the presence of oxygen[83] in the volatile alkali. A fact so

startling as the production of a metallic body from ammonia, or

from its elements, immediately excited in Davy's mind the most

ardent desire to pursue the enquiry; and, after repeating the

original experiments of the Swedish chemists with his accustomed

sagacity, he modified his methods of manipulation, in order, if

possible, to obtain this metallic body in its most simple form;

but, although he succeeded in producing the amalgam without

Voltaic aid, by the intervention of potassium, he could not so

distill off the mercury as to leave the basis, or imaginary

_ammonium_, free.

[83] See page 285.

The history of these researches into the nature of the ammoniacal

element concludes the lecture of which I have endeavoured to

give an outline. The subject of the amalgam is still involved in

mystery: if we suppose with Davy, that a substance, which forms

so perfect an amalgam with mercury, must of necessity be metallic

in its own nature, we cannot but conclude either that hydrogen

and nitrogen are both metals in the aëriform state, at the usual

temperatures of the atmosphere--bodies, for example, of the

same character as zinc and quicksilver would be at the heat of

ignition--or, that these gases are oxides in their common form,

but which become metallized by deoxidation--or, that they are

simple bodies, not metallic in their own nature, but capable of

composing a metal in their deoxygenated, and an alkali in their

oxygenated, state.

Before we venture, however, to entertain any opinions so

extravagant in their nature, and so wholly unsupported by analogy,

it would be well to enquire how far the change, which ammonia

and mercury undergo by Voltaic action, really merits the name of

amalgamation. Several chemists of the present day are inclined to

refer this change of form to a purely mechanical cause, by which

the particles of the metal become separated, and converted, as it

were, into a kind of _froth_ by the operation.[84]

[84] The late interesting experiments of Mr. Daniell "on the

action of Mercury on different Metals," which have been recently

published in the first number of a new series of the Journal

of the Royal Institution, appear to throw much light upon this

subject. By agitating a few grains of spongy platinum with

mercury in water acidified with acetic acid, he obtained an

amalgam of the consistence of soft butter, which retained its

consistence for many weeks, and greatly resembled that formed by

the electrization of mercury in contact with ammonia. When the

amalgam was laid upon filtering paper, the moisture was gradually

absorbed and evaporated, and the mercury returned to a fluid

state. By a more refined experiment, Mr. Daniell ascertained that

the process was accompanied by the evolution of hydrogen gas;

whence he very fairly concludes, that, when minutely divided,

platinum is agitated with mercury, and moisture is present, an

electrical action takes place, which, when heightened by the

addition of a diluted acid, or the solution of a neutral salt, is

sufficiently energetic to decompose water and evolve hydrogen:

the oxygen at the same time combines with the mercury, and a

solution is effected by the acetic acid, which its unassisted

affinity could not have produced. "It also appears," continues

Mr. Daniell, "that this electrical action communicates an

adhesive attraction to the particles of the metal, by which

the particles of liquid and aëriform bodies are entangled and

retained, a kind of _frothy_ compound formed, and the fluidity

of the mercury destroyed. The appearance of this amalgam is so

very like that of the ammoniacal compound formed by exposing a

solution of ammonia in contact with mercury to the influence of

the Voltaic pile, or when an amalgam of potassium and mercury is

placed upon moistened muriate of ammonia, that it is impossible

not to be struck with the resemblance. Mr. Daniell is therefore

inclined to believe that the production of the latter may be

explained upon the same principles as that of the former.

When the effect is produced by the direct application of the

electrical current, by means of the battery, it ceases the moment

the connexion between the poles is broken; and when brought about

by the agency of the amalgam of potassium, the electrical action

is doubtless excited by the contact of the two dissimilar metals,

and the frothy compound lasts no longer than the existence of the

potassium in the metallic state; whereas in the action between

mercury and finely divided platinum, the permanence of the metals

produces a much more lasting effect, and the soft amalgam may

therefore be preserved for a greater length of time.

Mr. Brande, in a late communication in the Journal of the Royal

Institution,[85] observes: "Shortly after the discovery of a method

of obtaining Morphia in a pure state, I remember that Sir Humphry

Davy suggested the possibility of its affording, when electrised

in contact with mercury, results corresponding with those which

Berzelius had observed in respect to ammonia. He thought that

the nascent elements of the morphia, as liberated by electrical

decomposition, might, under such circumstances, effect a similar

apparent amalgam of the mercury, and he spoke of the subject as

likely to throw some light upon the corresponding ammoniacal

combinations. He made, I believe, a few experiments upon the

subject; but as the results were not such as he had anticipated,

they were not placed on record."

[85] "On the Electro-chemical Decomposition of the

Vegeto-Alkaline Salts." In this communication, the Professor

gives an account of some experiments of his own, with a view

to ascertain whether the vegetable alkalies, if electrised in

contact with mercury, would impart any principle to the latter

metal. In experiments with morphia and cinchonia, in which the

mercury in contact with the vegetable base was rendered negative,

not the least change in the fluidity of the metal could be

perceived. When, however, a similar experiment was made with

quina, the metal became filmy, and acquired even a tendency to a

butyraceous appearance, but the phenomenon was found to depend

upon the presence of a minute portion of lime.

In the progress of our ascent, it is refreshing to pause

occasionally, and to cast a glance at the horizon, which widens

at every increase of our elevation. By the decomposition of the

alkalies and earths, what an immense stride has been made in the

investigation of nature!--In sciences kindred to chemistry, the

knowledge of the composition of these bodies, and the analogies

arising from it, have opened new views, and led to the solution

of many problems. In Geology, for instance, has it not shown that

agents may have operated in the formation of rocks and earths,

which had not previously been known to exist? It is evident that

the metals of the earths cannot remain at the surface of our globe;

but it is probable that they may constitute a part of its interior;

and such an assumption would at once offer a plausible theory in

explanation of the phenomena of volcanoes, the formation of lavas,

and the excitement and effects of subterranean heat, and might even

lead to a general theory in Geology.

The reader, for the present, must be satisfied with these cursory

hints: I shall hereafter show that our illustrious philosopher

followed them up by numerous observations and original experiments

in a volcanic country.

I remember with delight the beautiful illustration of his theory,

as exhibited in an artificial volcano constructed in the theatre

of the Royal Institution.--A mountain had been modelled in clay,

and a quantity of the metallic bases introduced into its interior:

on water being poured upon it, the metals were soon thrown into

violent action--successive explosions followed--red-hot lava was

seen flowing down its sides, from a crater in miniature--mimic

lightnings played around: and in the instant of dramatic illusion,

the tumultuous applause and continued cheering of the audience

might almost have been regarded as the shouts of the alarmed

fugitives of Herculaneum or Pompeii.