Transcriber's note:
This book was published in two volumes, of which this is the second.
The first volume was released as Project Gutenberg ebook #45394,
available at http:www.gutenberg.org/ebooks/45394. Italic text
has been marked with _underscores_. Please see the end of this
Project for further notes.
THE LIFE
OF
SIR HUMPHRY DAVY,
BART. LL.D.
LATE PRESIDENT OF THE ROYAL SOCIETY, FOREIGN ASSOCIATE
OF THE ROYAL INSTITUTE OF FRANCE,
&c. &c. &c.
BY
JOHN AYRTON PARIS, M.D. CANTAB. F.R.S. &c.
FELLOW OF THE ROYAL COLLEGE OF PHYSICIANS.
IN TWO VOLUMES.
VOL. II.
LONDON:
HENRY COLBURN AND RICHARD BENTLEY,
NEW BURLINGTON STREET.
M DCCC XXXI.
CONTENTS.
CHAPTER X.
Mr. Faraday's introduction to Sir H. Davy.--A renewed correspondence
on the subject of the Gunpowder Manufactory.--Davy
obtains permission from Napoleon to visit the Continent.--He embarks
in a Cartel from Plymouth.--Is arrested at Morlaix.--Arrives
at Paris.--Visits the Louvre.--His extraordinary conduct
upon that occasion.--Inspects the Colossal Elephant, and is introduced
to M. Alavair, its architect.--The discovery of the dungeons
of the Bastile.--Davy's interesting letter to M. Alavair.--He attends
a meeting of the Institute.--Is visited by all the principal savans
of Paris.--The adventure which befell Lady Davy in the Thuilleries'
Garden.--Anniversary dinner of the Philomatic Society.--The
junior Chemists of France invite Davy to a splendid entertainment.--How
far Davy is entitled to be considered the discoverer
of the true nature of Iodine.--Napoleon's unlucky experiment
with the Voltaic battery.--Davy is presented to the Empress
Josephine.--An account of the Court ceremony at Malmaison.--Remarks
on the conduct of Davy during his visit to Paris.--He quits the
capital of France, and proceeds by way of Lyons, to Montpellier.--Is
assisted in experiments on sea-weed by M. Berard.--Crosses
the Alps.--Arrives at Genoa.--Institutes experiments on
the Torpedo.--Visits Florence, and accomplishes the combustion
of the diamond, by the great lens in the cabinet of Natural
History.--Experiments on Iodine.--He examines the colours used by
the Ancients.--Visits all the celebrated Philosophers of Italy and
Switzerland, with whom he works in their laboratories.--Returns
to England 1
CHAPTER XI.
Collieries of the North of England.--Fire-damp.--The dreadful
explosion at Felling Colliery described.--Letters from the Bishop
of Bristol to the Author.--A Society is established at Bishop-Wearmouth
for preventing accidents in coal mines.--Various projects
for ensuring the miner's safety.--The Reverend Dr. Gray, the present
Bishop of Bristol, addresses a letter to Sir H. Davy, and
invites his attention to the subject.--Sir H. Davy's reply.--Farther
Correspondence upon the possibility of devising means of security.--Sir
H. Davy proposes four different kinds of lamp for the purpose.--The
Safe-lamp--The Blowing-lamp--The Piston-lamp--The
Charcoal-lamp.--His investigation of the properties of fire-damp
leads to the discovery of a new principle of safety.--His
views developed in a paper read before the Royal Society on the
9th of November 1815.--The first Safety-lamp.--Safety-tubes superseded
by Safety-canals.--Flame Sieves.--Wire-gauze lamp.--The
phenomenon of slow combustion, and its curious application.--The
invention of the Safety-lamp claimed by a Mr. Stephenson.--A
deputation of Coal-owners wait upon Sir H. Davy, in order to
express to him the thanks of the Proprietors for his discovery.--Mr.
Buddle announces to Dr. Gray (now Bishop of Bristol) the intention
of the Coal-trade to present him with a service of plate.--The
Resolutions are opposed, and the claims of Stephenson urged,
by Mr. W. Brandling.--A dinner is given to Sir Humphry, at which
the plate is presented to him.--The President and Council of the Royal
Society protest against the claims still urged by Mr. Stephenson's
friends.--Mr. Buddle's letter in answer to several queries
submitted to him by the Author.--Davy's Researches on Flame.--He
receives from the Royal Society the Rumford Medals.--Is
created a Baronet.--Some observations on the apathy of the State
in rewarding scientific merit.--The Geological Society of Cornwall
receives the patronage and support of Sir Humphry 58
CHAPTER XII.
Sir Humphry Davy suggests a chemical method for unrolling
the ancient Papyri.--He is encouraged by the Government to
proceed to Naples for that purpose.--He embarks at Dover.--His
experiments on the Rhine, the Danube, the Raab, the Save, the
Ironzo, the Po, and the Tiber, in order to explain the formation of
mists on rivers and lakes.--His arrival and reception at Naples.--He
visits the excavations at Herculaneum.--He concludes that it
was overwhelmed by sand and ashes, but had never been exposed
to burning matter.--He commences his attempt of unrolling the
Papyri.--His failure.--He complains of the persons at the head of
the department in the Museum.--He analyses the waters of the
Baths of Lucca.--His return to England.--Death of Sir Joseph
Banks.--He is elected President of the Royal Society.--Some
remarks on that event.--He visits Penzance.--Is honoured by a
public dinner.--Electro-magnetic discoveries of Oersted extended
by Davy.--He examines Electrical Phenomena in vacuo.--The
results of his experiments questioned.--He enquires into the state
of the water, and aëriform matter in the cavities of crystals.--The
interesting results of his enquiry confirm the views of the
Plutonists 160
CHAPTER XIII.
The Liquefaction of Chlorine Gas first effected by Mr. Faraday,
and witnessed by the Author.--Sir H. Davy continues the
investigation.--His paper on the application of Liquefiable Gases as
mechanical agents.--Other probable uses of these bodies.--He
proposes several methods to prevent the fumes which arise from
Smelting-furnaces.--Importance of the subject.--His Letters to
Mr. Vivian.--The Government solicit the advice of the Royal Society
on the subject of protecting the Copper Sheathing of Ships
from the action of sea-water.--Sir H. Davy charges himself with
this enquiry.--He proposes a plan of protection founded on Voltaic
principles.--His numerous experiments.--He embarks on board
the Comet steam-vessel bound to Heligoland, in order to try his
plan on a vessel in motion.--He arrives at Mandal, lands, and
fishes in the lakes.--The Protectors washed away.--He teaches
the inhabitants of Christiansand to crimp fish.--He remains a few
days at Arendal.--A Norwegian dinner.--The Protectors are examined
and weighed.--Results of the experiment.--The steam-vessel
proceeds up the Glommen.--He visits the great waterfall.--Passes
into Sweden.--Has an interview with the Crown Prince of
Denmark, and afterwards with Prince Christian at Copenhagen.--He
visits Professor Oersted.--He proceeds to Bremen to see Dr.
Olbers.--Returns to England.--His third paper read before the Royal
Society.--Voltaic influence of patches of rust.--A small quantity
of fluid sufficient to complete the circuit.--He receives from the
Royal Society the Royal Medal.--The Progress of Voltaic discovery
reviewed.--The principle is of extensive application.--The
Author's researches into the cause of the solution of Lead in spring
water.--An account of the numerous trials of Protectors.--Failure
of the plan.--Report of the French on the state of the protected
frigate, La Constance.--Dr. Revere's new plan of Protection 208
CHAPTER XIV.
The failure of the Ship protectors a source of great vexation to
Davy.--His Letters to Mr. Poole.--He becomes unwell.--He
publishes his Discourses before the Royal Society.--Critical Remarks
and Quotations.--He goes abroad in search of health.--His
Letter to Mr. Poole from Ravenna.--He resigns the Presidency
of the Royal Society.--Mr. Gilbert elected _pro tempore_.--Davy
returns to England, and visits his friend Mr. Poole.--Salmonia, or
Days of Fly-fishing.--An Analysis of the Work, with various
extracts to illustrate its character 283
CHAPTER XV.
Sir H. Davy's Paper on the Phenomena of Volcanoes.--His
experiments on Vesuvius.--Theory of Volcanic action.--His reception
abroad.--Anecdotes.--His last Letter to Mr. Poole from
Rome.--His paper on the Electricity of the Torpedo.--Consolations
in Travel, or the Last Days of a Philosopher.--Analysis of the
work.--Reflections suggested by its style and composition.--Davy
and Wollaston compared.--His last illness.--Arrival at Geneva.--His
Death 341
A GENERAL REVIEW OF THE HISTORY OF CHEMICAL SCIENCE,
AND OF THE REVOLUTIONS PRODUCED IN ITS DOCTRINES BY
THE DISCOVERIES OF SIR HUMPHRY DAVY 415
APPENDIX--Will of Sir Humphry Davy 457
THE LIFE
OF
SIR HUMPHRY DAVY,
BART. &c. &c.
CHAPTER X.
Mr. Faraday's introduction to Sir H. Davy.--A renewed
correspondence on the subject of the Gunpowder
Manufactory.--Davy obtains permission from Napoleon
to visit the Continent.--He embarks in a Cartel from
Plymouth.--Is arrested at Morlaix.--Arrives at Paris.--Visits
the Louvre.--His extraordinary conduct upon that
occasion.--Inspects the Colossal Elephant, and is introduced
to M. Alavair, its architect.--The discovery of the dungeons
of the Bastile.--Davy's interesting letter to M. Alavair.--He
attends a meeting of the Institute.--Is visited by all the
principal _savans_ of Paris.--The adventure which befell
Lady Davy in the Thuilleries' Garden.--Anniversary dinner
of the Philomatic Society.--The junior Chemists of France
invite Davy to a splendid entertainment.--How far Davy is
entitled to be considered the discoverer of the true nature
of Iodine.--Napoleon's unlucky experiment with the Voltaic
battery.--Davy is presented to the Empress Josephine.--An
account of the Court ceremony at Malmaison.--Remarks on
the conduct of Davy during his visit to Paris.--He quits
the capital of France, and proceeds, by way of Lyons, to
Montpellier.--Is assisted in experiments on sea-weed by M.
Berard.--Crosses the Alps.--Arrives at Genoa.--Institutes
experiments on the Torpedo.--Visits Florence, and accomplishes
the combustion of the diamond, by the great lens in the cabinet
of Natural History.--Experiments on Iodine.--He examines the
colours used by the Ancients.--Visits all the celebrated
Philosophers of Italy and Switzerland, with whom he works in
their laboratories.--Returns to England.
It is said of Bergman, that he considered the greatest of his
discoveries to have been the discovery of Scheele.[1] Amongst the
numerous services conferred upon Science by Sir Humphry Davy, we
must not pass unnoticed that kind and generous patronage which
first raised Mr. Faraday from obscurity, and gave to the chemical
world a philosopher capable of pursuing that brilliant path of
enquiry which the genius of his master had so successfully explored.
[1] See Note at page 42, vol. i.
The circumstances which first led Mr. Faraday to the study of
chemistry, and by which he became connected with the Royal
Institution, were communicated to me, by himself, in the following
letter.
TO J. A. PARIS, M.D.
MY DEAR SIR, Royal Institution, Dec. 23, 1829.
You asked me to give you an account of my first introduction
to Sir H. Davy, which I am very happy to do, as I think the
circumstances will bear testimony to his goodness of heart.
When I was a bookseller's apprentice, I was very fond of
experiment, and very averse to trade. It happened that a
gentleman, a member of the Royal Institution, took me to hear
some of Sir H. Davy's last lectures in Albemarle Street. I took
notes, and afterwards wrote them out more fairly in a quarto
volume.
My desire to escape from trade, which I thought vicious and
selfish, and to enter into the service of Science, which I
imagined made its pursuers amiable and liberal, induced me at
last to take the bold and simple step of writing to Sir H.
Davy, expressing my wishes, and a hope that, if an opportunity
came in his way, he would favour my views; at the same time I
sent the notes I had taken at his lectures.
The answer, which makes all the point of my communication, I
send you in the original, requesting you to take great care of
it, and to let me have it back, for you may imagine how much I
value it.
You will observe that this took place at the end of the year
1812, and early in 1813 he requested to see me, and told me
of the situation of assistant in the Laboratory of the Royal
Institution, then just vacant.
At the same time that he thus gratified my desires as to
scientific employment, he still advised me not to give up
the prospects I had before me, telling me that Science was
a harsh mistress; and, in a pecuniary point of view, but
poorly rewarding those who devoted themselves to her service.
He smiled at my notion of the superior moral feelings of
philosophic men, and said he would leave me to the experience
of a few years to set me right on that matter.
Finally, through his good efforts I went to the Royal
Institution early in March of 1813, as assistant in the
Laboratory; and in October of the same year, went with him
abroad as his assistant in experiments and in writing. I
returned with him in April 1815, resumed my station in the
Royal Institution, and have, as you know, ever since remained
there.
I am, dear Sir, very truly yours,
M. FARADAY.
The following is a note of Sir H. Davy, alluded to in Mr. Faraday's
letter:
TO MR. FARADAY.
SIR, December 24, 1812.
I am far from displeased with the proof you have given me
of your confidence, and which displays great zeal, power of
memory, and attention. I am obliged to go out of town, and
shall not be settled in town till the end of January: I will
then see you at any time you wish.
It would gratify me to be of any service to you. I wish it may
be in my power.
I am, Sir, your obedient humble servant,
H. DAVY.
I must now recall the reader's attention to the affair of the
gunpowder manufactory, to which some allusion has been already
made. It is far from my wish to intrude upon the public any account
of a private transaction; but the circumstances to which I must
refer are already well known, and I believe, moreover, that they
have been the subject of misrepresentation.
The letters I shall introduce appear to me highly interesting; and
by the warmth of feeling with which they repel the bare suspicion
of his prostituting science to the acquisition of wealth, to
develope a feature in his character too important to be omitted in
a memoir of his life.
From the following letter, it would appear that Davy's alarms, with
respect to his responsibilities, were first awakened by a sight of
the labels, in which his name was introduced.[2]
[2] I am here bound to state, from a careful examination of all
the original documents, that his name was introduced in the very
words which he suggested, and which I have at this moment before
me in his own handwriting:--so differently, however, does the
same sentence strike the eye in print and in manuscript, that an
author frequently does not recognise his own composition.
TO JOHN GEORGE CHILDREN, ESQ.
MY DEAR CHILDREN, Rokeby, July -- 1813.
I am very sorry you did not come to Cobham, as the party was
very pleasant.
Your apparatus was magnificent, worthy an Imperial Institute:
there were some swine however for the pearls; at least, there
was one,--you cannot suppose I mean any other than----.
I have been much disturbed and vexed by enquiries respecting
the price of _my_ gunpowder, which from the labels I find is
supposed to be _sold_ by me. These labels must be altered, so
as to put in a clear point my relations to the manufacture;
and it must be understood by the public that I have given my
gratuitous assistance and advice only.
I have written to Mr. Burton by post, giving two forms. I shall
do you more good if these are adopted than I can now; and I
wish them to be adopted speedily, as it may otherwise get
abroad that I have nothing to do with the powder, and that my
name is used in a manner which does not meet my approbation.
In the labels in the windows, it should not be _under my
directions_, for this implies that I am a superintendent
in the manufactory; but it should be--"RAMHURST GUNPOWDER,
manufactured by Messrs. B. C. and Co. In the composition of
this powder, the proprietors have been assisted by the advice
and assistance of Sir H. Davy."
A fair statement will do the manufacture good. Misapprehension
will do it much harm.
I am now at Rokeby; we shall be in a few days at Braham Castle,
Lord Mackenzie's, near Dingwall, where we shall stay for a
week. After that we shall go to the Marquis of Stafford's,
Dunrobin, near Goldspie.
I am, my dear Children,
Very truly and affectionately yours,
H. DAVY.
TO THE SAME.
MY DEAR CHILDREN, Edinburgh, July 22.
I wrote to you from Rokeby. I expressed my feelings respecting
the gunpowder. I have been in extreme harass and anxiety from
the idea of the use of my name, without the proper explanation,
and I certainly expected that no use would have been made
of it without my sanction. I never saw the label for the
canister till it came to me upon one of them, and I immediately
expressed that I was not satisfied with it.
I told Mr. Burton expressly, that in all cases in which my name
was used it must be in my own way. He is now at the head of
your firm; but it is to _you_, and not to _him_, that I have
given, and shall give my assistance.
Every feeling of friendship and affection prompts my wishes to
be useful to you; I have not the same relations to Mr. Burton.
I am very sorry to give you any trouble on this business, but I
am sure you cannot wish me to remain in a state of anxiety; and
all the friends with whom I have consulted think it absolutely
necessary for my reputation, that, when my name is used, a
clear statement should be given of the true nature of the
connexion.
I think it will be more useful to you, and increase your
influence and power in the partnership, if my assistance is
stated as given to you, and to you only--in this way: "RAMHURST
GUNPOWDER, manufactured by Messrs. Burton, Children, and
Co. after an improved process, founded upon experiments and
investigations made by Sir H. Davy, and communicated by him to
Mr. J. G. Children, under whose immediate superintendence the
gunpowder is made."
I have fully made up my mind on this matter: and if you approve
of the above form, I will state it to be the only one to which
I will consent.
If the gunpowder is called Sir H. Davy's powder, it must be
stated in all cases where my name is used, that it is so called
in honour of my discoveries in chemistry, and because I have
given my gratuitous assistance in making the experiments and
investigations on which the process is founded.
I have resolved to make no profit of any thing connected with
science. I devote my life to the public in future, and I must
have it clearly understood, that I have no views of profit in
any thing I do. I am, my dear Children,
Very affectionately yours,
H. DAVY.
In subsequent letters, which it is not necessary to publish,
Davy dwells upon the necessity of his engagements as a partner
being legally cancelled, as he cannot endure the idea of his
philosophical repose and usefulness being disturbed by the
cares of business, or the trouble of litigation.
It is scarcely necessary to add, that all the parties concerned
in this transaction most readily and cheerfully met Davy's
wishes, all erroneous impressions were effaced, and the affair
was adjusted amicably and satisfactorily; and he prepared
to quit England with a mind relieved from all the fears and
anxieties which had so unfortunately oppressed it.
* * * * *
After the Emperor of the French had sternly refused his
passport to several of the most illustrious noblemen of
England, it was scarcely to be expected that Sir H. Davy would
have been allowed to travel through France, in order to visit
the extinct volcanoes in Auvergne, and afterwards to examine
that which was in a state of activity at Naples.
No sooner, however, had the discovery of the decomposition of
the alkalies and earths, and its probable bearings upon the
philosophy of volcanic action, been represented by the Imperial
Institute to Napoleon, than, with a liberality worthy of the
liberator of Dolomieu, and consistent with his well-known
patronage of science, he immediately and unconditionally
extended the required indulgence.
In consequence of this permission, Sir Humphry and Lady Davy,
the former accompanied by Mr. Faraday as secretary and chemical
assistant, and the latter by her own waiting-maid, quitted
London on the 13th of October 1813, and proceeded to Plymouth;
at which port they immediately embarked in a cartel for Morlaix
in Brittany.
On landing in France, they were instantly arrested by the
local authorities of the town, who very reasonably questioned
the authenticity of their passports, believing it impossible
that a party of English should, under any circumstances, have
obtained permission to travel over the Continent, at a time
when the only English in France were detained as prisoners.
They were accordingly compelled to remain during a period of
six or seven days at the town of Morlaix, until the necessary
instructions could be received from Paris. As soon, however, as
a satisfactory answer was returned, they were set at liberty;
and they reached the French capital on the evening of the 27th
of the same month.
Shortly after his arrival, Davy called upon his old friend and
associate Mr. Underwood, who, although one of the _détenus_,
had during the whole war enjoyed the indulgence of residing in
the capital.
The expected arrival of Davy had been a subject of conversation
with the French _savans_ for more than a month. Amongst those
who were loudest in his praises, was M. Ampère, who had for
several years frequently expressed his opinion that Davy was
the greatest chemist that had ever appeared. Whether this
flattering circumstance had been communicated to the English
philosopher I have no means of ascertaining; but Mr. Underwood
informs me that the very first wish that Davy expressed was
to be introduced to this gentleman, whom he considered as the
only chemist in Paris who had duly appreciated the value of
his discoveries; an opinion which he afterwards took no care
to conceal, and which occasioned amongst the _savans_ much
surprise, and some dissatisfaction. M. Ampère, at the time of
Davy's arrival, was spending the summer at a place a few miles
from Paris, in consequence of which the introduction so much
desired was necessarily delayed.
On the 30th he was conducted by Mr. Underwood to the Louvre.
The English philosopher walked with a rapid step along the
gallery, and, to the great astonishment and mortification of
his friend and _cicerone_, did not direct his attention to a
single painting; the only exclamation of surprise that escaped
him was--"What an extraordinary collection of fine frames!"--On
arriving opposite to Raphael's picture of the Transfiguration,
Mr. Underwood could no longer suppress his surprise, and in a
tone of enthusiasm he directed the attention of the philosopher
to that most sublime production of art, and the chef d'oeuvre
of the collection. Davy's reply was as laconic as it was
chilling--"Indeed, I am glad I have seen it;" and then hurried
forward, as if he were desirous of escaping from any critical
remarks upon its excellencies.
They afterwards descended to view the statues in the lower
apartments: here he displayed the same frigid indifference
towards the higher works of art. A spectator of the scene might
have well imagined that some mighty spell was in operation, by
which the order of nature had been reversed:--while the marble
glowed with more than human passion, the living man was colder
than stone! The apathy, the total want of feeling he betrayed
on having his attention directed to the Apollo Belvidere, the
Laocoon, and the Venus de Medicis, was as inexplicable as it
was provoking; but an exclamation of the most vivid surprise
escaped him at the sight of an Antinous, treated in the
Egyptian style, and sculptured in _Alabaster_.[3]--"Gracious
powers," said he, "what a beautiful stalactite!"
[3] The celebrated Italian antiquary Visconti has so denominated
it.
What a strange--what a discordant anomaly in the construction of
the human mind do these anecdotes unfold! We have here presented
to us a philosopher, who, with the glowing fancy of a poet, is
insensible to the divine beauties of the sister arts! Let the
metaphysician, if he can, unravel the mystery,--the biographer has
only to observe that the Muses could never have danced in chorus at
his birth.
On the following morning, Mr. Underwood accompanied him to the
Jardin des Plantes, and presented him to the venerable Vauquelin,
who was the first scientific man he had seen in Paris. On their
return they inspected the colossal Elephant which was intended
to form a part of the fountain then erecting on the site of the
Bastile. Davy appeared to be more delighted with this stupendous
work than with any object he saw in Paris: to its architect, M.
Alavair, he formed an immediate attachment. It has been observed
that, during his residence in this city, his likes and dislikes to
particular persons were violent, and that they were, apparently,
not directed by any principle, but were the effect of sudden
impulse.
In the course of removing the foundations, and in digging the
canal, the subterranean dungeons of the Bastile were discovered;
they were eight in number, and were called _Les Oubliettes_. As
they were under the level of the ditch of the fortress, any attempt
to escape from them by piercing the wall, must have inevitably
drowned the unhappy prisoner together with all those who inhabited
the contiguous cells; one of which was discovered with the entrance
walled up. Upon demolishing this wall there appeared the skeleton
of the last wretched person who had been thus entombed. In all
these discoveries Davy took the warmest interest.
Upon the construction of the Elephant, he wrote a letter to M.
Alavair, to which I am desirous of directing the attention of my
scientific readers. It derives its peculiar interest from the
opinion which he at that period entertained upon the subject of the
excitement of Voltaic action by the contact of different metals.
TO M. ANTOINE ALAVAIR.
SIR, November 1813.
It will give me much pleasure if I can repay your civility to
me by offering any hints that may be useful in the execution of
the magnificent work constructing under your directions.
Ten parts of copper to one of tin is an excellent composition
for a work upon a great scale, nor do I believe any proportions
can be better.
There is no fear of any decay in the armatures, if they can be
preserved from the contact of moisture; but if exposed to air
and moisture, the presence of the bronze will materially assist
their decay. Wherever the iron is exposed to air, it should, if
possible, be covered with a thin layer of bronze. When the iron
touches the foundation of _lead_, it should in like manner be
covered either by lead or bronze. A contact between metals has
no effect of corrosion, unless a Voltaic circle is formed with
moisture, and then the most oxidable metal corrodes; and iron
corrodes rapidly both with lead and bronze.
The cement which will probably be found the most durable will
be lime, fine sand, and scoria of iron. The materials should be
very fine and intimately mixed. The ancients always made their
cements for great works some months before they were used. I
have the honour to be, Sir, with much consideration,
Your obedient humble servant,
H. DAVY.
Davy took up his abode at the Hotel des Princes, Rue Richelieu;
whither the principal _savans_ of Paris hastened to pay their
respects; which they did with an alacrity and cheerfulness equalled
only by the courtesy of manner with which they expressed their
congratulations.
On the 2nd of November, Davy attended the First Class of the
Institute, and was placed on the right hand of the President, who
on taking the chair announced to the meeting that it was honoured
by the presence of "Le Chevalier Davy."
While Davy was at the meeting of the Institute, a curious adventure
occurred to Lady Davy, the relation of which, by showing the state
of surveillance in which the citizens of Paris were held at that
period, will enable us to appreciate the extent of the obligation
conferred upon Sir Humphry by the Emperor.
Her Ladyship, attended by her maid, had walked into the
Thuilleries' Garden. She wore a very small hat, of a simple
cockle-shell form, such as was fashionable at that time in
London; while the Parisian ladies wore bonnets of most voluminous
dimensions. It happened to be a saint's day, on which, the shops
being closed, the citizens repaired in crowds to the garden. On
seeing the diminutive bonnet of Lady Davy, the Parisians felt
little less surprise than did the inhabitants of Brobdignag
on beholding the hat of Gulliver; and a crowd of persons soon
assembled around the unknown exotic; in consequence of which, one
of the inspectors of the garden immediately presented himself, and
informed her Ladyship that no cause of '_rassemblement_' could be
suffered, and therefore requested her to retire. Some officers of
the Imperial Guard, to whom she appealed, replied, that, however
much they might regret the circumstance, they were unable to afford
her any redress, as the order was peremptory. She then requested
that they would conduct her to her carriage; an officer immediately
offered his arm, but the crowd had by this time so greatly
increased, that it became necessary to send for a corporal's guard;
and the party quitted the garden, surrounded by fixed bayonets.
November 3rd, Humboldt and Gay-Lussac paid their first visit of
compliment to Davy.
5th.--M. Ampère, who came to Paris expressly for the occasion,
was introduced to Davy by Mr. Underwood, and the two philosophers
appeared equally delighted with each other. Some years afterwards,
however, this feeling of friendly regard, on the part of Davy, was
turned into one of bitter aversion, in consequence, as it has been
supposed, of certain perfidious insinuations, by which some of the
_savans_, instigated by feelings of jealousy, had contrived to
prejudice his mind; and which even led him to exert all his efforts
to oppose the election of Ampère as a foreign member of the Royal
Society.
After Ampère's visit, Mr. Underwood accompanied Sir H. and his
lady to the Imperial Library in the Rue Richelieu, and afterwards
to the Cathedral of Notre Dame, where they inspected the crown
and imperial regalia. The splendour of the coronation mantle
of Napoleon may be imagined, when it is stated that its weight
exceeded eighty pounds, and that it was lined with the skins of six
thousand ermines.
6th.--They visited the Museum of French Monuments, in the Rue
des Petits Augustines, which contained the tombs and sculptured
ornaments preserved from the churches that were demolished during
the Revolution. This interesting collection, shortly after the
restoration of the Bourbons, was dispersed. It is a singular fact,
that Davy expressed more admiration at this inferior exhibition
of art, than he did at that of the Greek and Roman statues in
the Museum of the Louvre. Whether his taste had been vitiated by
the inspection of less perfect models in his earlier days, is a
question which I shall leave more competent judges to decide.
10th.--They dined with Count Rumford at Auteuil, who showed his
laboratory to Davy: this was exactly eight months before the poor
brokenhearted Count sank into the grave, the victim of domestic
torment, and of the persecutions of the French _savans_, instigated
by his wife, the widow of the celebrated Lavoisier.
13th.--The anniversary dinner of the Philomatic Society took place
on this day, at a restaurateur's in the Rue St. Honoré; M. Dumeril
in the chair. Although it was very unusual to invite any stranger
upon this occasion, Sir H. Davy and his English friend were
requested to favour the company by their presence. Thirty-three
members were in attendance, amongst whom were Ampère, Brogniart,
Cuvier, Chevreuil, Dulong, Gay-Lussac, Humboldt, Thénard, &c.
At this dinner various complimentary toasts were proposed: and
first, the Royal Society of London, for which Davy having returned
thanks, gave the Imperial Institute. The Linnæan Society of London,
and the Royal Society of Berlin, were given in succession. But
the circumstance which evinced the greatest feeling and delicacy
towards their English guest, was the company's declining to drink
the health of the Emperor. It placed their personal safety even in
some jeopardy; and not a little apprehension was afterwards felt
as to how far Napoleon might resent such a mark of disrespect, for
seven-eighths of the members present were placemen.
November 17th.--Mr. Underwood states that on this day he met
Humboldt at dinner at Davy's hotel; and he adds--"I do not know
whether you are aware that Sir Humphry had a superstitious dislike
at seeing a knife and fork placed crosswise on a plate at dinner,
or upon any other occasion; but I can assure you that such was the
fact; and when it occurred in the company of his intimate friends,
he always requested that they might be displaced; whenever this
could not be done, he was evidently very uncomfortable."[4]
[4] I repeat this as I received it: from my own personal
knowledge I can neither confirm nor refute it; although I
am inclined to believe that Davy was tinged with a degree
of superstitious feeling, or a certain undefined species
of credulity, which shelters itself under the acknowledged
inadequacy of human reason to connect causes with effects.
At about this period, but I am unable to ascertain the particular
day, the junior Chemists, with Thénard as their leader, gave Davy
a sumptuous dinner at one of the most celebrated restaurateurs in
Paris. The following persons formed a committee for that purpose:
Gay-Lussac, Thénard, Dulong, Chevreul, Laugier, Robiquet, and
Clement. As it was by the chemists only that this dinner was given,
neither Arago nor Ampère was included; but Berthollet, Chaptal, and
Vauquelin were invited.
On the morning of the 23rd of November,[5] M. Ampère called upon
Davy, and placed in his hands a small portion of a substance which
he had received from M. Clement; and, although it had been in the
possession of the French chemists for more than twelve months, so
entirely ignorant were they of its true nature and composition,
that it was constantly spoken of amongst themselves as X, the
_unknown_ body.
[5] The date of this event is important; and Mr. Faraday, in
referring to his Journal, finds it to be correctly stated.
How far the suggestions of Davy led to the discovery of the
chemical nature of this interesting substance, which has been
since distinguished by the name of _Iodine_, is a question which
has given rise to much discussion on the Continent. It has been
moreover questioned, how far the love of science, and the fervour
of emulation, can justify the interference which Davy is said to
have displayed upon the occasion. He is accused of having unfairly
taken the subject out of the hands of those who were engaged in its
investigation, and to have anticipated their results.
As his biographer, I feel that it is not only due to the character
of Davy, but essential to the history of Science, that these
questions should be impartially examined; and I have spared no
pains in collecting facts for their elucidation. Mr. Underwood, who
was in the constant habit of associating with the parties concerned
in the enquiry, has furnished me with some important particulars,
and his testimony is fortified by published documents.
The substance under dispute was accidentally discovered by M.
Courtois, a manufacturer of saltpetre at Paris, but kept secret by
him for several years; at length, however, he communicated it to
M. Clement, who made several experiments on it, but without any
favourable result. On the 23rd of August 1813, Clement exhibited
to Mr. Underwood the beautiful experiment of raising it into a
violet-coloured vapour, and that gentleman assures me that this was
the only peculiar property which had at that time been recognised
as distinguishing it. A few days previous to this event, M. Ampère
had received a specimen of the substance, which he had carefully
folded up in paper, and deposited in his pocket, but on arriving
at home, and opening the packet, he was surprised to find that his
treasure had vanished. Clement, however, furnished him with another
supply, and it was this parcel that Ampère transferred into the
hands of Davy; and "for which," says Mr. Underwood, "he told me a
few days ago, that Thénard and Gay-Lussac were extremely angry with
him."
The first opinion which the French chemists entertained respecting
the nature of Iodine, was that it was either a compound of muriatic
acid, or of chlorine, since it formed with silver what appeared
to be a muriate, or a chloride of that metal; but Davy at once
observed that the substance so produced blackened too quickly in
the sun to justify that opinion. He, however, determined to submit
it to a more rigorous examination; and during the latter part of
November he worked upon it at his hotel with his own apparatus,
and on the 3rd of December in the laboratory of M. Chevreul, at
the Jardin des Plantes, with whom, it may be stated in passing,
he perhaps formed a stricter intimacy than with any other chemist
during his sojourn in Paris. Chevreul, however, be it known, was a
brother of the angle; and I understand that he still preserves, as
sacred trophies, some artificial flies with which Davy had supplied
him.
Having pointed out the channel through which Iodine first fell into
the hands of Davy, let us pursue its history. The first public
notice of its existence was read by Clement at the Institute, on
the 29th of November 1813. At the meeting of the 6th of December,
Gay-Lussac, who had only received some 'X' a few days previous to
this date, presented a short note, in which he gave the name of
_Iode_ to the body, and threw out a hint as to its great analogy to
chlorine, while he stated that two hypotheses might be formed as
to its nature, that it might be considered as a simple substance,
or as a compound of oxygen. On the 13th of the same month, a
letter addressed to M. le Chevalier Cuvier, and dated December
11th, was read from Davy to the Institute, in which he offered
a general view of its chemical nature and relations;[6] and on
the 20th of January 1814, he communicated to the Royal Society
of London, a long and elaborate paper, dated Paris, December 10,
1813, and entitled, "Some Experiments and Observations on a new
Substance, which becomes a violet-coloured gas by Heat." In this
paper, while the author assigned to Gay-Lussac all the credit to
which his communication of the 6th of December may be supposed to
entitle him, he evidently felt that some explanation was due to the
chemical world for his having pursued the enquiry. "M. Gay-Lussac,"
he observes, "is still engaged in experiments on this subject,
and from his activity and great sagacity, a complete chemical
history of it may be anticipated. But as the mode of procuring the
substance is now known to the chemical world in general, and as
the combinations and agencies of it offer an extensive field for
enquiry, and will probably occupy the attention of many persons;
and as the investigation of it is not pursued by the discoverer
himself, nor particularly by the gentlemen to whom it was first
communicated, I shall not hesitate to lay before the Royal Society
an account of the investigations I have made upon it; and I do
this with the less scruple, as my particular manner of viewing
the phenomena has led me to some new results, which probably will
not be considered by the Society as without interest in their
relation to the general theory of chemistry, and in their possible
application to some of the useful arts."
[6] See _Annales de Chimie_, tome 88, p. 322. It appears from Mr.
Faraday's Journal, that he worked upon Iodine with a borrowed
Voltaic pile, at his hotel, on the morning of the 11th; and the
results of his experiments are described at the conclusion of the
above letter.
It was not until August 1814, that Gay-Lussac read his paper on
the subject, which was subsequently published in the _Annales de
Chimie_.
After the above short, but I trust honest statement, can any
reasonable doubt exist, that, if Davy had not visited Paris, Iodine
would have remained at the end of the year 1814, as it had been for
two preceding years--the unknown X?
In a communication published in the first volume of the Royal
Institution Journal, Davy offers the following observations upon
this subject: "With regard to Iodine, the first I had of it was
from M. Ampère, who, before I had seen the substance, supposed that
it might contain a new supporter of combustion.
"Who had most share in developing the chemical history of that
body, must be determined by a review of the papers that have been
published upon it, and by an examination of their respective
dates. When M. Clement showed Iodine to me, he believed that the
hydriodic acid was muriatic acid; and M. Gay-Lussac, after his
early experiments, made originally with M. Clement, formed the
same opinion, and _maintained_ it, when I _first_ stated to him my
belief that it was a new and peculiar acid, and that Iodine was a
substance analogous in its chemical relations to Chlorine."
I was very desirous of ascertaining the feeling which at present
prevails amongst the French chemists upon this subject; and I
therefore requested Mr. Underwood to make such enquiries as might
elicit the required information. In a letter from that gentleman,
dated "Paris, August 22, 1830," he says, "Though Thénard and
Gay-Lussac retain great bitterness of feeling towards Davy, on
account of the affair of Iodine, Chevreul and Ampère are still, as
they ever were, of opinion, that such a feeling has its origin in
a misconception; that what Davy did, was from the honest desire of
promoting science, and not from any wish to detract from the merit
of the French chemists."
During his visit to Paris, Davy was not introduced to the Emperor.
Lady Davy observed to me, that, although Sir Humphry felt justly
grateful for the indulgence granted to him as a Philosopher, he
never, for a moment, forgot the duty he owed his country as a
Patriot; and that he objected to attend the levee of her bitterest
enemy. On the other hand, it is said that Napoleon never expressed
any wish to receive the English chemist; and those who seek in the
depths for that which floats upon the surface, have racked their
imaginations in order to discover the source of this mysterious
indifference; but I apprehend that we have only to revert to the
political state of Europe in the year 1813, and the problem will be
solved.
Amongst the reasons for supposing that the Emperor must have felt
ill disposed towards the English philosopher, the following story
has been told; which, as an anecdote, is sufficiently amusing;
and I can state upon the highest authority, that it is moreover
perfectly true.
It is well known that Bonaparte, during his whole career, was in
the habit of personal intercourse with the _savans_ of Paris, and
that he not unfrequently attended the sittings of the Institute.
Upon being informed of the decomposition of the alkalies, he
asked, with some impetuosity, how it happened that the discovery
had not been made in France?--"We have never constructed a Voltaic
battery of sufficient power," was the answer. "Then," exclaimed
Bonaparte, "let one be instantly formed, without any regard to cost
or labour."
The command of the Emperor was of course obeyed; and, on being
informed that it was in full action, he repaired to the laboratory
to witness its powers; on his alluding to the taste produced by
the contact of two metals, with that rapidity which characterised
all his motions, and before the attendants could interpose any
precaution, he thrust the extreme wires of the battery under
his tongue, and received a shock which nearly deprived him of
sensation. After recovering from its effects, he quitted the
laboratory without making any remark, and was never afterwards
heard to refer to the subject.
It is only an act of justice to state that Davy, during his
residence in the French capital, so far from truckling to French
politics, never lost an opportunity of vindicating with temper
the cause of his own country. At the Théâtre de la Porte Saint
Martin, a melodrame was got up, with the avowed intention of
exposing the English character to the execration of the audience.
Lord Cornwallis was represented as the merciless assassin of the
children of Tippoo Saib. Davy was highly incensed at the injustice
of the representation, and abruptly quitted the theatre in a state
of great indignation.
Whatever objections might have existed in his mind, as to his
attending a levee of the Emperor, they did not operate in
preventing his being presented to the Empress at Malmaison; but he
could not be prevailed upon to appear upon that occasion, in any
other than a morning dress; and it was not until after repeated
entreaty, and the assurance that he would not be admitted into
the _Salle de reception_, that he consented to exchange a pair of
half-boots that laced in front, and came over the lower part of his
pantaloons, for black silk stockings and shoes. His constant answer
to the remonstrances of his friends was, "I shall go in the same
dress to Malmaison as that in which I called upon the Prince Regent
at Carlton House."
The introduction of Sir Humphry and Lady Davy to the Empress
Josephine, took place at Malmaison on the 30th of November. The
only English present were, the Earl of Beverley, a _détenue_;
General Sir Edward Paget, a prisoner of war, taken in Spain,
and Mr. Underwood; and it was the first levee at which any of
our countrymen had been introduced, with the exception of Mr.
Underwood, who had been frequently in the habit of paying his court
to the Empress, and to whom, indeed, he was indebted for those
indulgences which have been already mentioned.
The persons present having arranged themselves in a semicircle, the
Empress entered the _Salle de reception_, and in her usual gracious
manner addressed each individual. After this court ceremony, her
Majesty retired, having previously signified to a select few, her
desire that they should follow her into the private apartment.
In the Boudoir, the conversation became general, and turned upon
certain works of art; and upon Lady Davy expressing, in very florid
terms, her admiration of some beautifully embellished cups of
Porcelain, which were stationed on the mantelpiece, her Majesty,
with that good-nature which ever distinguished her, immediately
presented her with a specimen.
The Empress then proposed that Lady Davy should on this occasion
visit her conservatories, upon which it is well known she had
lavished large sums, and was ambitious to be thought to possess
all that was rare and curious. Lady Davy having expressed some
apprehensions as to the coldness of the day, and appearing to
be but thinly clad, one of the Dames du Palais was commanded
to provide cloaks; and in a short time, Mr. Underwood says, a
_mountain_ of the most costly and magnificent furs, that probably
ever appeared even in a Regal Palace, were displayed before her;
the splendid trophies, we may conclude, of the Royal conciliation
at Tilsit.
It was on the 13th of December 1813, that Davy was elected a
corresponding member of the First Class of the Imperial Institute;
there were forty-eight members present, and he had forty-seven
votes: Guyton de Morveau being the only person who opposed his
election.
Nothing ever exceeded the liberality and unaffected kindness and
attention with which the _savans_ of France had received and
caressed the English philosopher. Their conduct was the triumph
of Science over national animosity,--a homage to genius, alike
honourable to those who bestowed, and to him who received it;
and it would be an act of ingratitude, a violation of historical
justice, on the part of the English biographer, did he omit to
express the pride and admiration with which every philosopher in
his country continues to regard it. It would have been fortunate
for the cause of Science, and fortunate for the historian, could he
have terminated the subject with these remarks; but the biographer
has an act of justice to perform, which he must not suffer his
friendship to evade, nor his partialities to compromise.[7]
[7] In offering these observations, the reader may readily
suppose it has not been without much pain that I have made this
sacrifice of personal feeling to principle. I am, however, bound
to observe, that Sir Humphry's sentiments towards France for the
liberal indulgence granted to him were both grateful and kindly;
and so strongly does Lady Davy participate in that feeling, that
I perhaps owe it to her to state that neither her Ladyship's
journals or information have been used upon this occasion.
It would be an act of literary dishonesty to assert that Sir H.
Davy returned the kindness of the _savans_ of France, in a manner
which the friends of Science could have expected and desired. There
was a flippancy in his manner, a superciliousness and hauteur in
his deportment, which surprised as much as they offended. Whatever
opinions he might have formed as to the talents of the leading
chemists, it was weakness to betray, and arrogance to avow them.
He had, by a single blow, fatally mutilated the system which was
the pride and glory of their nation: it was ungenerous to remind
them of his triumph. It required but little tact to have reconciled
the French philosophers to the revolution he had effected; but,
unfortunately, that cannot be said of Davy, which was so wittily
observed of Voltaire,--that if he trod upon the toes of their
prejudices, he touched his hat at the same time: even the affair
of Iodine, had it been skilfully managed, would never have left an
angry feeling. It was not his success, but the manner in which he
spoke of it, that rendered it so offensive. He should have acted
according to the judicious advice given to a member of the clerical
profession, upon his consulting a friend as to the propriety of
continuing his field-sports, should he become a dignitary of the
Church--"You may hunt, but you must not holla."
It may be supposed that the unguarded conduct of Davy reached the
ear of the Emperor; for in a conversation with one of the leading
members of the Institute, Napoleon took occasion to observe, that
he understood the young English chemist held them all in low
estimation.
Having thus candidly avowed the errors of Davy, I may be justified
in claiming from the reader his confidence in the sincerity with
which I shall attempt to palliate them. From my personal knowledge
of his character, I am inclined to refer much of that unfortunate
manner, which has been considered as the expression of a haughty
consciousness of superiority, to the desire of concealing a
_mauvaise honte_ and _gaucherie_--an ungraceful timidity, which
he could never conquer. The bashful man, if he possess strong
passions, will frequently force himself into a state of effrontery,
by a violence of effort which passes amongst ordinary observers
for the sallies of pride, or the ebullitions of temper; whereas
if, on the contrary, his temperament be cold and passionless, he
will exhibit traits of the most painful reserve. This proposition
cannot, perhaps, be more forcibly illustrated than by a comparison
of the manners of Davy and Cavendish, whose temperaments were
certainly as much opposed to each other as fire is to ice: the
latter, however, was shy and bashful, to a degree bordering upon
disease; and nothing so much distressed him as an introduction to
strangers, or as his being pointed out as a person distinguished
in science. On one of the Sunday evening _soirées_ of Sir Joseph
Banks, he happened to be conversing with his friend Mr. Hatchett,
when Dr. Ingenhouz, who was rather remarkable for pomposity of
manner, approached him with an Austrian gentleman in his hand, and
introduced him formally to Mr. Cavendish. He recounted the titles
and qualifications of his foreign friend at great length, and
concluded by saying, that he had been particularly anxious to be
introduced to a philosopher so universally celebrated throughout
Europe as Mr. Cavendish. As soon as Dr. Ingenhouz had finished, the
Austrian gentleman began; he assured Mr. Cavendish that one of his
principal inducements in coming to London, was to see and converse
with one whom he considered the most distinguished chemist of the
age. To all these high-flown addresses, Mr. Cavendish answered not
a single word, but stood with his eyes cast down upon the floor,
in a state of the most painful confusion. At length, espying an
opening in the crowd, he darted through it with all the speed he
could command, and never stopped until he reached his carriage,
which immediately drove him home.
From the same cause, probably, arose Davy's inattention and
carelessness in those little observances of etiquette, which many
may treat as empty and unmeaning ceremonials, but which the members
of a polished community regard as the delicate expressions of
feeling, and the language of sentiment.
It is said, that on conversing in the chamber of the Institute, he
received one of its most distinguished and venerable members, who
approached him with the air of salutation, without rising from his
seat; a circumstance perhaps in itself of very trifling importance,
but it was considered as a mark of disrespect, which is not readily
forgiven, when a spirit of rivalry may be supposed to sharpen the
affront. It will be remembered that Cæsar might date his loss of
popularity to the fact of his having received the Senate while
sitting in the porch of the temple of Venus, and that it formed
one of the chief pretences of those who organised the conspiracy
against his person.
There were, besides, other sources of unpopularity, which we are
bound in fairness and candour to impute to the excellencies,
rather than to the defects, of his character. If we believe with
Johnson, that men have sometimes gained reputation from their
foibles, we may certainly admit the converse of the proposition,
that they have occasionally lost it from their virtues. Davy, as
we have seen, possessed from his earliest years a frankness of
disposition which endeared him to all his friends, but in after
life it unquestionably exposed him to various annoyances, which
by a little reserve he would have certainly escaped. It is quite
surprising how much a little mystery, judiciously managed, will
achieve. Seven veils converted the fragment of a tile, ploughed
up in the neighbourhood of Florence, into an object of awful
devotion.[8]
[8] Gray's Letters.
Although it must be admitted that our philosopher lost some
popularity during his visit to the French metropolis, the _savans_
did not the less respect his talents, or admire his discoveries.
They appear to have been impressed with the same sentiment as that
which animated Voltaire, when he asked whether the discovery of
Racine's weakness made the part of Phædra less admirable.
M. Dumas, who is certainly by no means distinguished for the
readiness with which he is disposed to pay homage to British
talent, has declared that Davy was the greatest chemical genius
that ever appeared.
In fact, the more the researches of this great experimentalist are
studied, the more they must be admired: every attempt to depreciate
their intrinsic importance will only serve to display their exalted
merits; every attempt to falsify their results will only tend to
demonstrate their accuracy. It is by an elaborate examination
only, that the full evidence of their truth can be displayed;
there are points which the keen eye of genius will discern, that
are invisible to a grosser sense: the coldness of criticism then
will only make them glow the brighter; like his own potassium, the
contact even of ice, so far from extinguishing, will light them up
in splendour.
Sir Humphry left Paris on the morning of the 29th of December, and
proceeded by the way of Lyons to Montpellier, where he remained
for a month, and became acquainted with M. BERARD, who afterwards
filled the chemical chair in that university, and in whose
laboratory he worked upon the subject of Iodine, and examined many
of the marine productions of the Mediterranean, with the view of
determining whether they contained that body. M. Berard directed
a considerable quantity of the species of _Ulva_, which abounds
on the coast of Languedoc, to be burnt for him; and although the
ashes consisted for the most part of common salt, he obtained
traces of Iodine in the lixivium. From the general results of
his experiments, however, he concludes, that the ashes of the
_fuci_ and _ulvæ_ of the Mediterranean afford it in much smaller
quantities than the sea-weed, from which soda is procured; and it
was only in a very few instances that he could derive any evidence
of its existence. In the ashes of the corallines and sponges, he
could not obtain the slightest indication of its presence. During
this period he also extended his enquiries respecting the chemical
agencies of Iodine, and the properties of several of its compounds,
especially of those in which he believed it to exist in triple
combination with alkalies and oxygen, and for which he proposed the
name of _Oxy-iodes_.[9]
[9] These are the _Iodates_ of the present day; but Davy, it
would seem, resisted the conviction of Iodic acid being an
_oxy-acid_, upon the same grounds that he opposed the views of M.
Gay-Lussac with regard to the nature of Chloric acid.
While at Montpellier, Davy witnessed the procession of the Pope
on his return to Rome. His Holiness appeared in a state of great
humiliation, and, on being supplicated by a poor woman to cure her
child, he replied, that she must propitiate Heaven by her prayers,
for that he was himself a mere mortal, without power to heal or to
save.
He quitted Montpellier on the 7th of February, and, accompanied
by M. Berard, visited the fountain of Vaucluse; he afterwards
continued his route to Nice, crossed the Col de Tende, to Turin,
and arrived at Genoa on the 25th of February; from which place the
following letter is dated.
TO MR. UNDERWOOD.
MY DEAR UNDERWOOD, Genoa, March 4.
I have not received the letter you announced to me in the
street, concerning Ampère's note, nor any others since I left
Paris. The note came to me through the Prefect of Nice, with an
indorsement by M. Degerand.
I crossed the Alps by the Col de Tende, stayed at Turin three
days, and came here through snow and ice, over the Bochetta,
where I have been waiting for a fair wind for Tuscany. We have
had no impediments except from the snow and the east winds.
If you can hear any thing of the destination of the letters
I have twice missed, I shall thank you to let me know by
addressing me at Rome at the _Posta_. I shall be most happy
to hear some news of you here, and shall always feel a lively
interest in your plans, and in your welfare.
I have been making some experiments here on the Torpedo, but
without any decisive results; the coldness of the weather
renders the powers of the animal feeble; I hope, however, to
resume them at Naples.
Tell M. Ampère, I hope he will not give up the subject of the
laws of the combination of gaseous bodies, which is so worthy
of being illustrated by his talents, and which offers such
ample scope for his mathematical powers, united as they are
with chemical knowledge:--tell him also that I hope he will
sometimes write to me, and that I shall always remember with
pleasure the hours I have passed in his society.
Pray tell me that you are well; and remember me to all that are
interested in me. My wife desires her kind remembrances. I am,
my dear Underwood,
Your very sincere friend,
H. DAVY.
Besides researches on the Torpedo, Davy made farther experiments on
the ashes of Sea-weed, which were collected for him by Professor
VIVIANI, of Genoa.
He left Genoa by water on the 13th, and arrived at Florence on the
16th of March. Here he worked in the laboratory of the Academia
del Cimento, on Iodine; but more particularly on the combustion of
the Diamond. The experiments on this latter body were performed by
means of the great lens in the cabinet of Natural History; the same
instrument as that employed in the first trials on the action of
the solar heat on the diamond, instituted by Cosmo III. Grand Duke
of Tuscany: upon this occasion, he was assisted by COUNT BARDI,
the Director, and SIGNIOR GAZZARI, the Professor of Chemistry at
the Florentine Museum.
I have been informed that the hasty, and apparently careless manner
in which he conducted his experiments, and which has been already
noticed[10] as being characteristic of his style of manipulation,
greatly astonished the philosophers of Florence, and even excited
their alarm for the safety of the lens, which on all occasions had
been used by them with such fastidious caution and delicacy.
[10] Vol. i. p. 144.
In the very first trials on the combustion of the diamond, he
ascertained a very curious circumstance that had not been before
noticed; namely, that the diamond, when strongly ignited by the
lens in a thin capsule of platinum, perforated with many orifices,
so as to admit a free circulation of air, will continue to burn
in oxygen gas after being withdrawn from the focus. The knowledge
of this circumstance enabled him to adopt a very simple apparatus
and mode of operation in his researches, and to complete in a few
minutes experiments which had been supposed to require the presence
of a bright sunshine for many hours.
The new facts obtained by the experiments on Iodine, which he had
commenced at Montpellier and carried on at Florence, he embodied
in a memoir, which was read before the Royal Society on the
16th of June 1814. It treated more particularly of the triple
compounds containing iodine and oxygen,--of the hydrionic acid,
and of the compounds procured by means of it,--of the combinations
of iodine and chlorine,--of the action of some compound gases
on iodine,[11]--and, lastly, of the mode of detecting iodine in
combinations. "If iodine," he says, "exists in sea water, which
there is every reason to believe must be the case, though in
extremely minute quantities, it is probably in triple union with
oxygen and sodium, and in this case it must separate with the first
crystals of common salt."
[11] The compounds which he supposed to be thus produced are of
a very questionable nature; with respect to that formed with the
Olefiant gas, he was evidently in error.
He quitted Florence on the 3rd, and having visited Sienna,
entered Rome on the 6th of April. The Continent having now become
accessible, he met with many of his English friends: but neither
the extended society by which he was surrounded, nor the classical
attractions of the city of the Cæsars, allured him from the
pursuits of Science. We find that, shortly after his arrival,
he renewed his researches on the combustion of different kinds
of charcoal, in the laboratory of the Academia del Lyncei, in
which he was assisted by SIG. MORRICHINI and BARLOCCI, Professors
of the College Sapienza at Rome. Having arranged the results
of this investigation, together with those relating to the
combustion of the diamond, which he had previously obtained at
Florence, he transmitted a paper to the Royal Society, entitled
"Some Experiments on the Combustion of the Diamond, and other
carbonaceous substances;" which was read on the 23rd of June, and
published in the Second Part of the Philosophical Transactions for
the year 1814.
No sooner had it been established by various accurate experiments,
that the diamond and common charcoal consumed nearly the same
quantity of oxygen in combustion, and produced a gas having the
same obvious qualities, than various conjectures were formed to
explain the remarkable differences in the sensible qualities of
these bodies, by supposing some minute difference in their chemical
composition. MM. Biot and Arrago, from the high refractive power
of the diamond, suspected that it might contain hydrogen. Guyton
Morveau inferred from his experiments that it was pure carbon, and
that charcoal was an oxide of carbon; whereas Davy was inclined
to believe, from the circumstance of the non-conducting power of
the diamond, as well as from the action of potassium upon it, that
a minute portion of oxygen might enter its composition, although
such a supposition would be at variance with the doctrine of
definite proportions; but more lately, in his account of some new
experiments on the fluoric compounds, he hazarded the idea that
it might be the carbonaceous principle combined with some new and
subtile element, belonging to the same class as oxygen, chlorine,
and fluorine, which has hitherto escaped detection, but which may
be expelled, or newly combined, during its combustion in oxygen.
"That some chemical difference," says Davy, "must exist between
the hardest and most beautiful of the gems and charcoal, between
a nonconductor and a conductor of electricity, it is scarcely
possible, notwithstanding the elaborate experiments that have
been made on the subject, to doubt: and it seems reasonable to
expect, that a very refined or perfect chemistry will confirm the
analogies of Nature, and show that bodies cannot be exactly the
same in composition or chemical nature, and yet totally different
in all their physical properties."
With these impressions, we may readily imagine the ardour with
which he availed himself of the use of the great lens at Florence.
He had in various ways frequently attempted to fuse charcoal,[12]
but without success. In a letter addressed to Mr. Children is the
following passage: "The great result to be hoped for is the fusion
of carbon; and then you may use diamond in the manufacture of
gunpowder."
[12] The supposed fusion of charcoal by Professor Silliman, by
means of Dr. Hare's galvanic deflagrator, was a fallacy arising
from the earthy impurities of the substance. See _American
Journal of Science_, vol. v. p. 108, and 361.
He tells us that he had long felt a desire to make some new
experiments on the combustion of the diamond and other carbonaceous
substances; and that this desire was increased by the new fact
ascertained with respect to iodine, which by uniting to hydrogen,
affords an acid so analogous to muriatic acid, that it was for
some time confounded with that body. His object in these new
experiments, was to examine minutely whether any peculiar matter
was separated from the diamond during its combustion, and to
determine whether the gas, formed in this process, was precisely
the same in its minute chemical nature, as that formed in the
combustion of common charcoal. By his experiments at Florence, he
satisfactorily accomplished his wishes, and established beyond a
question the important fact, that "the diamond affords no other
substance by its combustion than pure carbonic acid gas; and that
the process is merely a solution of diamond in oxygen, without any
change in the volume of the gas."
As one of the principal objects in these researches was to
ascertain whether water was formed during the combustion of the
diamond, with a view to decide the question of the presence of
hydrogen, every possible source of fallacy was excluded. In one
experiment there was an evident deposition of moisture, but it was
immediately discovered to have been owing to the production of
vapour from a cork connected with a part of the apparatus, during
the combustion.
In the progress of this research, he ascertained a fact, the
knowledge of which must not only be considered as important to the
present enquiry, but as highly valuable in excluding error from our
reasonings upon the delicate results of analysis[13]--I allude to
the extremely minute quantity of water which becomes perceptible
by deposition on a polished glass surface. He introduced a piece
of paper weighing a grain into a tube of about the capacity of
four cubical inches, the exterior of which was gently heated by a
candle; immediately a slight but perceptible dew appeared in the
interior of the upper part of the tube; the paper taken out and
directly weighed in a balance, sensible to 1-100th of a grain, had
not suffered any appreciable diminution. If, then, on burning 1·84
grains of diamond in oxygen gas, not even a barely perceptible
dew was produced, we may consider it as fully proved that this
gem cannot contain hydrogen in its composition: but to render the
demonstration, if possible, still more complete, he kept a small
diamond, weighing ·45 of a grain, in a state of intense ignition
by the great lens of the Florentine Museum, for more than half an
hour, in chlorine; but the gas suffered no change, and the diamond
underwent no alteration either in weight or appearance: now had
the smallest portion of hydrogen been developed, white fumes of
muriatic acid would have been visible, and a certain condensation
of the gas must have taken place.
[13] It has a more especial bearing upon that experimental
research by which the nature of chlorine was established, as
described at page 337, vol. i. to which I beg to refer the
chemical reader.
The general tenor of his results was equally opposed to the idea of
the diamond containing oxygen; for, in such a case, the quantity of
carbonic acid generated by the combustion, would, on comparison,
have indicated that fact. By combining the carbonic acid with lime,
and then recovering the gas from the precipitate by muriatic acid,
he found its proportion to be exactly that which was furnished by
an equal weight of Carrara marble similarly treated.
The enquiry next proceeds to the examination of other forms of
carbonaceous matter, such as plumbago, charcoal formed by the
action of sulphuric acid on oil of turpentine, and that produced
during the formation of sulphuric ether; and lastly, the common
charcoal of oak.
In all these bodies, he detected the presence of hydrogen, both by
the water generated during their combustion, and by the production
of muriatic acid, when ignited in chlorine. The chemical
difference then between the diamond and the purest charcoal, would
appear to consist in the latter containing hydrogen; but Davy very
justly asks whether a quantity of an element, less in some cases
than 1-5000th part of the weight of the substance, can occasion
so great a difference in physical and chemical characters? "It
is certainly possible," says he, "yet it is contrary to analogy,
and I am more inclined to adopt the opinion of Mr. Tennant,
that the difference depends upon crystallization." In support
of such an opinion, he farther adduces the fact, that charcoal
after being intensely ignited in chlorine, is not altered in its
conducting power or colour: in which case the carbon is freed from
the hydrogen, and yet undergoes no alteration in its physical
properties.
One distinction supposed to exist between the diamond and common
carbonaceous substance, the researches of Davy have certainly
removed, viz. its relative inflammability; for he has shown that
the former will burn in oxygen with as much facility as plumbago.
The experiments, then, which Davy conducted at Florence and Rome,
have removed several important errors with regard to the nature
of carbonaceous substances; and though they may not encourage the
labours of those speculative chemists who still hope to illustrate
the old proverb,[14] by manufacturing diamonds out of charcoal,
they certainty show that they are less chimerical than those of the
wild visionaries who sought to convert the baser metals into gold.
[14] "Carbonem pro Thesauro."
While at Rome, Davy was engaged for several successive days in
the house of Morrichini, for the purpose of repeating with that
philosopher his curious experiments on _magnetisation_. Mr. Faraday
was charged with the performance of the experiments, but never
could obtain any results.
On the 8th of May he entered Naples, and remained there for three
weeks, during which period he visited Mount Vesuvius, and the
volcanic country surrounding it. He describes the crater, at this
time, as presenting the appearance of an immense funnel, closed
at the bottom, with many small apertures emitting steam; while on
the side towards Torre del Greco, there was a large aperture from
which flame issued to a height of at least sixty yards, producing a
most violent hissing noise. He was unable to approach sufficiently
near the flame to ascertain the results of the combustion; but
a considerable quantity of steam ascended from it; and he says,
that when the wind blew the vapours upon him, there was a distinct
smell both of sulphurous and muriatic acids, but there was no
indication of carbonaceous matter from the colour of the smoke;
nor was any deposited upon the yellow and white saline matter
which surrounded the crater, and which he found to be principally
sulphate and muriate of soda, and in some specimens there was also
a considerable quantity of muriate of iron. At this period, when
the volcano was comparatively tranquil, he observed the solfaterra
to be in a very active state, throwing up large quantities of
steam, and some sulphuretted hydrogen.
At several subsequent periods he revisited Vesuvius; and I shall
hereafter take occasion to relate all the principal observations he
made, and the conclusions at which he arrived, with respect to this
the most interesting of all the phenomena of mineral nature.
He also took great interest in the excavations at that time going
on at Pompeii, under the direction of Murat, then King of Naples,
who placed at his disposal several specimens of art, which Davy
received with a view to investigate the chemical composition of the
colours used by the Ancients.
On the 25th of May he returned to Rome, and again quitted it on the
2nd of June.
I regret to say that the information I have received, as to the
future continental travels of our philosopher, is extremely meagre,
and will consist of little more than names and dates. Of this,
however, the reader may be assured, that nothing which relates to
his scientific researches has been omitted.
From Rome he proceeded to Terni, and thence to Bologna, where he
remained for three days; then to Mantua, Verona, and Milan. Whether
at this or at some subsequent period he went to Pavia, in order to
pay his homage to the illustrious Volta, I entertain some doubt;
but the time is immaterial to the point of the anecdote I am about
to relate.
Davy had sent a letter to Pavia to announce his intended visit;
and on the appointed day and hour, Volta, in full dress, anxiously
awaited his arrival. On the entrance of the great English
philosopher into the apartment, not only in _déshabille_, but in a
dress of which an English artisan would have been ashamed, Volta
started back in astonishment, and such was the effect of his
surprise, that he was for some time unable to address him.
From Milan, which he left on the 22nd of June, he went to Como,
Domo D'Ossola, and then over the Simplon, to Geneva, where he
arrived on the 25th of that month, and remained until the 18th of
September. During this visit he made various experiments on Iodine,
at the house of De Saussure, which was situated near the edge of
the Lake, and about three miles from Geneva. He also worked at M.
Pictet's house, on the subject of the heat in the solar spectrum.
Here also he met with a number of celebrated persons, whose society
he greatly enjoyed; amongst whom were Madame de Stael, Benjamin
Constant, Necker, and Talma. Lausanne, Vevay, Payerne, Berne,
Zurich, Schaffhausen, and Munich, were successively visited by
him. His route was then continued through Tyrol, Inspruck, Calmar,
Bolsenna, Trent, Bassano, Vicenza, Padua, to Venice; where having
remained two days, he returned to Padua on the 16th of October, and
then proceeded to Ferrara, Bologna, and Pietra-Mala; near which
latter place, in the Apennines, he examined a fire produced by
gaseous matter constantly disengaged from a schist stratum, and
from the results of its combustion, he concluded it to be pure
fire-damp. On again reaching Florence, he found that the Professors
had been dismissed, but he nevertheless resumed his researches,
first at home, and afterwards in the laboratory of the Grand Duke,
where he submitted to analysis some gas which had been collected
by his attendant Mr. Faraday, from a cavity in the earth, about a
mile from Pietra-Mala, then filled with water, and which from the
quantity of gas disengaged is called _Aqua Buja_. It was found to
be pure light carburetted hydrogen, requiring two volumes of oxygen
for its combustion, and producing a volume of carbonic acid gas.
"It is very probable," says he, "that these gases were disengaged
from coal strata beneath the surface, or from bituminous schist
above coal; and at some future period new sources of wealth may be
opened to Tuscany from this invaluable mineral treasure."
On the 29th he left Florence, and passing through Levano, Tortona,
and Terni, arrived again at Rome, on the 2nd of November, where he
remained till the 1st of March 1815.
During this winter he was engaged in an elaborate enquiry into
the composition of ancient colours; and also in experiments upon
certain compounds of iodine and of chlorine. Upon which subjects
he transmitted to the Royal Society three memoirs, viz. one
entitled, "Some Experiments and Observations on the Colours used in
Painting by the Ancients," which was read on the 23rd of February;
a second, "On a solid compound of Iodine and Oxygen," read April
10; and a third, "On the action of Acids on the Salts usually
called Hyper-oxymuriates, and on the Gases produced from them,"
read May 4, 1815; all of which were published in the Philosophical
Transactions for that year.
Although the paintings of the great masters of Greece have been
entirely destroyed, either by accident, by time, or by the
barbarian conquerors at the period of the decline and fall of
the Roman Empire, yet there is sufficient proof that this art
attained a very high degree of excellence amongst a people to whom
genius and taste were a kind of birthright, and who possessed a
perception, which seemed almost instinctive, of the dignified, the
beautiful, and the sublime.
Our philosopher observes, that the subjects of many of those
pictures are described in ancient authors, and that some idea of
the manner and style of the Greek artists may be gained from the
designs on the vases improperly called "Etruscan," which were
executed by artists of Magna Græcia, and many of which are probably
copies from celebrated works: of their execution and colouring,
some faint notion may be gained from the paintings in fresco found
at Rome, Herculaneum, and Pompeii; for, although these paintings
are not properly Grecian, yet at the period when Rome was the
metropolis of the world, the fine arts were cultivated in that city
exclusively by Greek artists, or by artists of the Greek school;
while it is evident, on comparing the descriptions of Vitruvius
and Pliny with those of Theophrastus, that the same materials for
colouring were employed at Rome and at Athens.
With regard to the nature of these pigments, we may obtain some
information from the works of Theophrastus, Dioscorides, Vitruvius,
and Pliny; but until the present memoir by Sir H. Davy, no
experimental attempt had been made to identify them, or to imitate
such of them as are peculiar.
His experiments, he informs us, were made upon colours found in the
Baths of Titus, and the ruins called the Baths of Livia, and in the
remains of other palaces and baths of ancient Rome, and in the
ruins of Pompeii.
By the kindness of his friend Canova, who was charged with the care
of the works connected with ancient art in Rome, he was enabled to
select, with his own hands, specimens of the different pigments
that were found in vases discovered in the excavations made beneath
the ruins of the palace of Titus, and to compare them with the
colours fixed on the walls, or detached in fragments of stucco;
and Signor Nelli, the proprietor of the "Nozze Aldobrandine,"[15]
permitted him to make such experiments upon the colours of that
celebrated picture, as was necessary to determine their nature.
[15] The most celebrated picture of antiquity rescued from the
ruins of Herculaneum. It represents a virgin on her marriage
night, with her female attendants. An engraving of it is to be
seen in Sir William Hamilton's work on Herculaneum.
Without entering into the chemical details of the subject, I shall
offer a general history of the nature of the colours he examined.
Of the red colours, he distinguished four distinct kinds, viz.--one
bright and approaching to orange, which he found to be _Minium_,
or the red oxide of lead; a second, dull red, which he ascertained
to be an iron ochre; a third, a purplish red, which was likewise
an ochre, but of a different tint; and a fourth, a brighter red
than the first, which was _Vermilion_ or _Cinnabar_, a sulphuret
of mercury. On examining the fresco paintings in the Baths of
Titus, he found that all the three first colours had been used, the
ochres particularly, in the shades of the figures, and the minium
in the ornaments on the borders. The fourth red had been employed
in various apartments, and formed the basis of the colouring of
the niche, and of other parts of the chamber in which the Laocoon
is said to have been found in the time of Raphael; a circumstance
which Davy considers as being favourable to the belief that such
apartments were intended for Imperial use, since vermilion, amongst
the Romans, was a colour held in the highest esteem, and was always
one of great costliness.
Of the yellows, the more inferior were mixtures of ochre and
different quantities of chalk; the richer varieties were ochres
mixed with the red oxide of lead.
The ancients had also two other colours, which were orange, or
yellow; the auripigmentum, or [Greek: arsenikon], said to approach
to gold in the brilliancy of its tint, and which is described by
Vitruvius as being found native in Pontus, and which Davy says was
evidently sulphuret of arsenic;--and a pale sandarach, said by
Pliny to have been found in gold and silver mines, and which was
imitated at Rome by a partial calcination of cerusse. He conceives
that this must have been _Massicot_, or the yellow oxide of lead
mixed with minium; I suspect, however, that Davy was mistaken in
supposing that the ancients always applied the term Sandarach
to minium; the [Greek: Sandarakê] of Aristotle was evidently an
arsenical sulphuret.
In his examination of the ancient Frescoes, he could not detect the
use of orpiment; but a deep yellow, approaching to orange, which
covered a piece of stucco in the ruins near the monument of Caius
Cestius, proved to be oxide of lead, and consisted of massicot
and minium. He considers it probable that the ancients used many
colours from lead of different tints, between the "_usta_" of
Pliny, which was our minium, and imperfectly decomposed cerusse, or
pale massicot.
The differently shaded blues, by the action of acids, uniformly
assumed the same tint; from which he concluded that the effect of
the base was varied by different proportions of chalk. This base
he ascertained to be a _frit_, made by means of soda and sand, and
coloured by oxide of copper.
The greens were, in general, combinations of copper; and it seemed
probable, that although they appeared in the state of carbonate,
they might originally have been laid on in that of acetate. The
purple of the ancients, the [Greek: porphora] of the Greeks, and
the _Ostrum_ of the Romans, was regarded as their most beautiful
colour, and was obtained from shell-fish. Vitruvius states that it
was prepared by beating the fish with instruments of iron, freeing
the purple liquor from the shell containing it, and then mixing it
with a little honey. Pliny says that, for the use of the painters,
_argentine creta_, (probably a clay used for polishing silver,)
was dyed with it, and both Vitruvius and Pliny state that it was
adulterated, or imitations of it made by tinging _creta_ with
madder; whence it would appear, that the ancients were acquainted
with the art of making a lake colour from that plant, similar to
the one used by modern painters.
Pliny informs us, that the finest purple had a tint like a
deep-coloured rose. In the Baths of Titus, there was found a
broken vase of earthenware, which contained a pale rose colour;
and Davy selected it as an appropriate subject for his analytical
experiments.
Where this colour had been exposed to the action of the air, its
tint had faded into a cream colour, but the interior parts retained
a lustre approaching to that of carmine. A diluted acid was found
to dissolve out of it a considerable quantity of carbonate of lime,
with which the colouring principle must have been mixed, as a
substance of a bright rose colour remained after the process. This
colouring ingredient was proved to contain siliceous, aluminous,
and calcareous earths, without any sensible trace of metallic
matter, except oxide of iron. Upon heating the substance, first in
oxygen, and then with hyper-oxymuriate of potash, Davy was induced
to consider the colouring matter itself as either of vegetable or
animal origin; the results, however, were so equivocal, that he
renounced the hope of determining its nature from the products of
its decomposition. If it be of animal origin, he thinks it is most
probably the Tyrian or marine purple, as it is likely that the
most expensive colour would have been employed in ornamenting the
Imperial baths.
He had not observed any colour of the same tint as this ancient
lake in the fresco paintings; the purplish reds in the Baths of
Titus he ascertained to be mixtures of red ochres and the blues of
copper.
The blacks and browns were mixtures of carbonaceous matter,
with the ores of iron or manganese. The black from the Baths of
Titus, as well as that from some ruins near the Porta del Popolo,
deflagrated with nitre, and presented all the character of
carbon. This fact agrees with the statements of all the ancient
authors who have described the artificial Greek and Roman black as
consisting of carbonaceous matter, either prepared from the powder
of charcoal, from the decomposition of resin, (a species of lamp
black,) from that of the lees of wine, or from the common soot of
wood fires. Pliny also mentions the inks of the cuttle-fish, but
adds, "_Ex his non fit._"
Davy informs us, that, some years before, he had examined the black
matter of the cuttle-fish, and had found it to be a carbonaceous
substance mixed with gelatine.[16]
[16] I find from a note addressed by Davy to Mr. Underwood, that
he was engaged in these experiments in October 1801.
Pliny, moreover, speaks of ivory black invented by Apelles; of a
natural fossil black; and of a black prepared from an earth of
the colour of sulphur. Davy is of opinion, that both these latter
pigments were ores of iron and manganese; and he observes that the
analysis of some purple glass satisfied him that the ancients were
well acquainted with the ores of manganese.
The _whites_ which he examined from the Baths of Titus, as well as
those from other ruins, were either chalk, or fine aluminous clay;
and he states that, amongst all his researches, he never once met
with cerusse.
This interesting account of the colours used by the ancients is
followed by observations on the manner in which they were applied;
and the paper is concluded with some general remarks of much
practical importance.
The azure, he says, of which the excellence is sufficiently proved
by its duration for 1700 years, may be easily and cheaply imitated:
he found, for instance, that fifteen parts of carbonate of soda,
twenty parts of opaque flint powdered, and three parts of copper
filings, by weight, when strongly heated together for two hours,
yielded a compound substance of exactly the same tint, and of
nearly the same degree of fusibility; and which, when powdered,
produced a fine deep sky-blue.
The azure, the red and yellow ochres, and the blacks, appear to
have been the only pigments which have not undergone any change in
the fresco paintings. The vermilion presents a darker hue than that
of recently made Dutch cinnabar; and the red lead is inferior in
tint to that sold in the shops. The greens are generally dull.
The blue frit above mentioned, he considers as a colour composed
upon the truest principles; and he thinks there is reason to
believe, that it is the colour described by Theophrastus as the one
manufactured at Alexandria. "It embodies," says he, "the colour in
a composition like stone, so as to prevent the escape of elastic
matter from it, or the decomposing action of the elements upon it."
He suggests the possibility of making other _frits_, and thinks it
would be worth while to try whether the beautiful purple given by
oxide of gold could not be made useful in a deeply tinted glass.
Where _frit_ cannot be employed, he observes that metallic
combinations which are insoluble in water, and which are saturated
with oxygen or some acid matter, have been proved by the testimony
of seventeen centuries to be the best pigments. In the red ochres,
for example, the oxide of iron is fully combined with oxygen and
carbonic acid; and the colours composed of them have never changed.
The carbonates of copper, which consist of an oxide and an acid,
have suffered but little alteration. Massicot and orpiment, he
considers as those which have been the least permanent amongst all
the mineral colours.
He next takes a view of the colours which owe their origin to the
improvements of modern chemistry. He considers the _patent yellow_
to be more permanent, and the chromate of lead more beautiful,
than any yellow possessed by the Greeks or Romans. He pronounces
_Scheele's green_ (arsenite of copper), and the insoluble muriatic
combinations of copper, to be more unalterable than the ancient
greens; and he thinks that the sulphate of baryta offers a white
far superior to any pigment possessed by the ancients.
In examining the colours used in the celebrated Nozze Aldobrandine,
he recognised all the compounds which his analytical enquiries had
established: viz. the reds and yellows were all ochres; the blues,
the Alexandrian frit; the greens, copper; the purple, especially
that in the garment of the Pronuba, appeared to be a compound
colour of red ochre and copper; the browns and blacks were mixtures
of ochres and carbon; while the whites were carbonate of lime.
"The great Greek painters," he adds, "like the most illustrious
artists of the Roman and Venetian school, were probably sparing in
the use of the more florid tints in historical and moral painting,
and produced their effects rather by the contrasts of colouring in
those parts of the picture where a deep and uniform tint might be
used, than by brilliant drapery.
"If red and yellow ochres, blacks and whites, were the pigments
most employed by Protogenes and Apelles, so they are likewise
the colours most employed by Raphael and Titian in their best
style. The St. John and the Venus, in the tribune of the Gallery
at Florence, offer striking examples of pictures in which all the
deeper tints are evidently produced by red and yellow ochres, and
carbonaceous substances.
"As far as colours are concerned, these works are prepared for that
immortality which they deserve; but unfortunately, the oil and the
canvass are vegetable materials, and liable to decomposition, and
the last is even less durable than the wood on which the Greek
artists painted their celebrated pictures.
"It is unfortunate that the materials for receiving those works
which are worthy of passing down to posterity as eternal monuments
of genius, taste, and industry, are not imperishable marble or
stone:[17] and that _frit_, or unalterable metallic combinations
have not been the only pigments employed by great artists; and that
their varnishes have not been sought for amongst the transparent
compounds[18] unalterable in the atmosphere."
[17] Copper, it is evident from the specimens in the ruins of
Pompeii, is a very perishable material; but modern science might
suggest some voltaic protection.
[18] Davy thinks that the artificial hydrat of alumina will
probably be found to be a substance of this kind; and that,
possibly, the solution of boracic acid in alcohol will form a
varnish. He also thinks, that the solution of sulphur in alcohol
is worthy of an experiment.
In his memoir "On a solid compound of Iodine and Oxygen," he
enumerates, amongst the agencies of that body, its singular
property of forming crystalline combinations with all the fluid
or solid acids. It will be unnecessary to follow him through this
investigation, since its results have been found to be erroneous.
M. Serullas[19] has lately shown that the crystalline bodies of
Davy are nothing more than the iodic acid, which being insoluble in
acids, is necessarily precipitated by them.
[19] Annales de Chimie, t. 43. p. 216.
His paper "On the action of Acids on Salts usually called
Hyper-oxymuriates," announced the important fact of chlorine
forming with oxygen a compound, in which the latter element exists
in a still greater proportion than in the body previously described
by him under the name of _Euchlorine_.[20]
[20] See page 330. vol. i.
Before finally quitting Italy, he spent three weeks at Naples,
during which period he experimented on iodine and fluorine in the
house of Sementini; he also paid several visits to Vesuvius, and
found the appearances of the crater to be entirely different from
those which it presented in the preceding year:[21] there was,
for instance, no aperture in it; it was often quiet for minutes
together, and then burst out into explosions with considerable
violence, sending fluid lava, and ignited stones and ashes, to a
height of many hundred feet in the air.
[21] See page 42. vol. ii.
"These eruptions," says he, "were preceded by subterraneous
thunder, which appeared to come from a great distance, and which
sometimes lasted for a minute. During the four times that I was
upon the crater, in the month of March, I had at last learnt to
estimate the violence of the eruption from the nature of the
sound: loud and long-continued subterraneous thunder indicated a
considerable explosion. Before the eruption, the crater appeared
perfectly tranquil; and the bottom, apparently without an aperture,
was covered with ashes. Soon, indistinct rumbling sounds were
heard, as if at a great distance; gradually, the sound approached
nearer, and was like the noise of artillery fired under our feet.
The ashes then began to rise and to be thrown out with smoke from
the bottom of the crater; and lastly, the lava and ignited matter
was ejected with a most violent explosion. I need not say, that
when I was standing on the edge of the crater, witnessing this
phenomenon, the wind was blowing strongly from me; without this
circumstance, it would have been dangerous to have remained in such
a situation; and whenever from the loudness of the thunder the
eruption promised to be violent, I always ran as far as possible
from the seat of danger.
"As soon as the eruption had taken place, the ashes and stones
which rolled down the crater seemed to fill up the aperture,
so that it appeared as if the ignited and elastic matter were
discharged laterally; and the interior of the crater assumed the
same appearance as before."
On the 21st of March, he quitted Naples, and
returned to England by the following route:
Rome--Narni--Nocere--Fessombone--Imola--Mantua--(March 30,)
Verona--Pero--Trente--Botzen--Brennah--Inspruck--Zirl--(April
4,) Reuti-Menningen--Ulm--(April 6,)
Stutgard--Heidelburg--Mayence--Boppert--Coblentz--Cologne--(April
14,) Leuch--Brussels--Ostend--Dover--London, April 23, 1815.