Davy makes a tour with Mr. Purkis, through Wales.--Beautiful
phenomenon observed from the summit of Arran Benllyn.--Letter
to Mr. Gilbert.--Journal of the Institution.--Davy's papers on
Eudiometry, and other subjects.--His first communication to the
Royal Society, on a new galvanic pile.--He is proposed as a
Fellow, and elected into the Society.--His paper on astringent
vegetable substances, and on their operation in tanning
leather.--His letter to Mr. Poole.--He is appointed Chemical
Lecturer to the Board of Agriculture.--He forms friendships
with the Duke of Bedford, Mr. Coke, and many other celebrated
agriculturists.--Attends the sheep-shearing at Holkham and
Woburn.--Composes a Prologue to the "Honey-Moon."
After the fatigues and anxieties of his first session, Davy sought
relaxation and repose amidst the magnificent scenery of Wales. The
following letter will serve more fully to exhibit the enthusiasm he
experienced in contemplating Nature in her wild and simplest forms.
TO SAMUEL PURKIS, ESQ.
Matlock, August 15, 1802.
MY DEAR FRIEND,
Had I been alone, and perfectly independent as to my plans, I
should probably have written to you long ago. I should have begged
you to hasten your departure, so that we might have rejoiced
together in Wales, under the influence of that moon which is now
full in all its glory; for Derbyshire, taken as a whole, has not
pleased me. A few beautiful valleys, placed at the distance of many
miles from each other, do not compensate for the almost uniform
wildness and brown barrenness of the hills and plains; and in the
watering places, there is little amongst the _living beings_ to
awaken deep moral feelings, or to call the nobler powers of the
mind, which act in consequence of sympathy, into existence.
I have longed for the mountain scenery, and for the free
inhabitants of North Wales; and even the majestic valleys of the
Wye and the Derwent have been to me but typical of something more
perfect in beauty and grandeur.
Whenever it shall seem fitting to you, I shall be prepared
for our long contemplated journey, and do not delay your
departure;--_before_ the 21st would be more agreeable to me than
_after_ that period; and then we shall be able to view the horns of
the next moon, where they are most beautiful.
I have enquired much concerning Dove-dale, since I have been here,
and, from the most accurate accounts, I am inclined to believe that
it is inferior, in point of sublime scenery, to _Chee Tor_, near
Bakewell, and in beauty, to the valley of the _Great Tor_, in which
I am now writing. On the whole, I think your best plan will be to
meet me at Matlock, which you must see, and then, in our route to
Buxton, we can visit the valley of the Wye, and the most noble
_Chee Tor_.
Concerning the excursion of Dove-dale, I am undecided, and it
shall depend upon you to determine with regard to it.
As one great object in our excursions is to view Nature and man
in their most simple forms, and to gain a temporary life of new
impressions, I submit to you whether it will not be best to steer
clear of _towns_, _cities_, and _civilized society_, in which, for
the most part, we can see what we have only seen before.
If we visit Sir Joseph Banks, it certainly should be only _en
passant_: and to see that most excellent personage, and to be
obliged to quit him immediately, will be at least painful; for the
respectful feelings he produces in the mind are always modified by
affection.
I have no room to give you the quantity of information that I
have gained concerning the places and people of Wales; this shall
serve for our Derbyshire chat. I thank you much for your last kind
letter, which gave me high pleasure. You possess the true spirit of
composition, which embodies facts in words.
I am, &c.
H. DAVY.
I am informed by Mr. Purkis, that in the latter end of this summer,
he made a pedestrian tour with Davy, through North and South
Wales, and he has transmitted to me the following account of this
excursion.--"We visited every place possessing any remains of
antiquity, any curious productions of nature or art, and every spot
distinguished by romantic and picturesque scenery. Our friend's
diversified talents, with his knowledge of Geology, and Natural
History in general, rendered him a most delightful companion in a
tour of this description. Every mountain we beheld, and every river
we crossed, afforded a fruitful theme for his scientific remarks.
The form and position of the mountain, with the several _strata_
of which it was composed, always procured for me information as
to its character and classification; and every bridge we crossed
invariably occasioned a temporary halt, with some appropriate
observations on the productions of the river, and on the diversion
of angling.
"In one of our morning excursions in North Wales, we ascended the
summit of _Arran Benllyn_, a celebrated mountain, inferior only to
Snowdon and Cader Idris, a few miles from the lake of Bala. Here
we were fortunate in beholding a scene of extraordinary sublimity,
seldom witnessed in this climate. From the top of this mountain
we looked down, about mid-day, on a deep valley eight or ten
miles in length, and as many in breadth, the whole of which, for
a considerable height from the surface of the ground, was filled
with beautiful clouds, while the atmosphere around the summit on
which we stood was perfectly clear, and the sky above us of a deep
blue colour. The clouds in the valley were in irregular, gentle
undulations, dense, compact, and continuous, of that kind which is
denominated by Meteorologists _cirro-cumulus_, and by the vulgar,
_woolpack_ clouds, such as are often seen in the higher regions
on a fine summer's day. The sun shone with great brilliancy, and
illumined their various forms with silver, grey and blue tints of
exquisite beauty. As there was scarcely a breath of air stirring
below the mountain, this aggregation of clouds, probably occasioned
by some electrical agency, remained fixed and stationary, as
if identified with the valley. The higher parts of most of the
surrounding hills were enveloped in mist, above which the tops
of _Snowdon_ and _Cader Idris_ towered distinctly visible, and
appeared like small islands rising out of the sea. This scene
altogether was one of inexpressible magnificence and grandeur,
filling the mind with awe and rapture. We seemed to feel ourselves
like beings of a higher order in a celestial region, looking down
on the lower world with conscious superiority.
"After sitting and ruminating on this sublime spectacle for two or
three hours, we left the summit of the mountain with reluctance,
and, slowly descending, rested at intervals, and often cast a
longing, lingering look behind.
"On reaching our comfortable inn at Bala, while waiting for dinner,
Davy walked about the room, and, as if by inspiration, broke out
in a beautiful impassioned apostrophe on the striking scene we
had so recently witnessed. It was in a kind of unmeasured blank
verse, highly animated and descriptive, at once poetical and
philosophical. At the conclusion of this eloquent effusion, I
endeavoured to recollect and commit it to writing, but I could not
succeed, and Davy was too modest to assist my memory.
"In a tour through North Wales, where the few small inns have
seldom any spare rooms, different parties are often obliged to sit
in the same apartment, and to eat at the same table. Hence we were
occasionally introduced to characters of various descriptions,
some of whom gratified us by their agreeable qualities, while
others disgusted us by their ignorance and impertinence. On one
occasion, after a heavy shower of rain in the middle of August, we
were drying our clothes by the fire in the little Inn at _Tan y
Bwlch_, when the landlord requested us to admit a gentleman, who
was very wet. A young man, of pleasing appearance and manner, was
then introduced, and after some common-place observations, we sat
down to dinner. The stranger was evidently a man of education and
acquirements, and after the cloth had been removed, he began to
discourse very fluently on scientific subjects. He talked of oxygen
and hydrogen, of hornblende, and the _Grawacké_ of Werner, and
geologists, in the most familiar tone of self-complacency.
"Davy's youth, simplicity of manner, and cautious concealment
of superior knowledge, not exciting constraint, our companion
was naturally induced to deliver his opinions with the utmost
freedom and confidence on all subjects. We commenced on poetry and
painting; the sublime and beautiful; then proceeded to mineralogy,
astronomy, &c. and occasionally digressed on topics of mirth and
humour, so that the evening was passed with general satisfaction.
"When Davy had retired to rest, and I was left alone with our
companion, I enquired how he liked my friend, and whether he
considered him a proficient in science, and versed in chemistry
and geology? He answered coolly, that 'he appeared to be rather
a clever young man, with some general scientific knowledge.' He
then asked his name, and when I announced 'Davy, of the Royal
Institution,' the stranger seemed thunderstruck, and exclaimed,
'Good God! was that really Davy? How have I exposed my ignorance
and presumption!' It is scarcely necessary to add, that at the
breakfast table the next morning, he talked on subjects of science
with less volubility than on the preceding evening."
After Davy's return from this expedition, he wrote the following
letter.
TO DAVIES GIDDY, ESQ.
Royal Institution, Oct. 26, 1802.
MY DEAR SIR,
It is long since I have had the pleasure of hearing from you.
You probably received a hasty letter that I wrote to you in the
beginning of the summer. Since that period, I have been idling away
much of my time in Derbyshire and North Wales.
Till very lately, I had hopes of being able to spend a few weeks
of the autumn in Cornwall, but I now find that it will not suit
with my occupations. Not having it in my power to see you, you may
believe that I am most anxious to hear from you.
We hear, at this time, in London of comparatively few scientific
novelties. The wonders of revolutionized Paris occupy many of our
scientific men; and the summer and autumn are not the working
seasons in great cities. The rich and fashionable part of the
community think it their duty to kill time in the country, and
even philosophers are more or less influenced by the spirit of the
times.
In the last volume of the Manchester Memoirs, _i.e._ the fifth, are
some papers of Mr. Dalton on the Constitution of the Atmosphere;
on the expansive powers of Steam; and on the dilatation of Elastic
Fluids by Heat. As far as I can understand his subjects, the author
appears to me to have executed them in a very masterly way. I wish
very much to have your judgment upon his opinions, some of which
are new and very singular.
Have you yet seen the theory of my colleague, Dr. Young, on the
undulations of an Ethereal Medium as the cause of Light? It is not
likely to be a popular hypothesis, after what has been said by
Newton concerning it. He would be very much flattered if you could
offer any observations upon it, whether for or against it. The
paper is in the last volume of the Transactions.
I believe I mentioned to you in a former letter that _Terra
Japonica_, or _Extractum Catechu_, contained a very large
proportion of the tanning principle. My friend Mr. Purkis, an
excellent practical tanner, has lately tried some experiments upon
it in the large way. It answers very well, and I am now wearing
a pair of shoes, the leather of one of which was tanned with
oak-bark, and that of the other with _Terra Japonica_; and they
appear to be equally good. We are in great hopes that the East
India Company will consent to the importation of this article. One
pound of it goes at least as far as nine pounds of oak-bark; and it
could certainly be rendered in England for less than four-pence
the pound: oak-bark is nearly one penny per pound.
The _Zoonic acid_, which M. Berthollet supposed to be a peculiar
acid, has been lately shown by M. Thénard to be only acetous acid,
holding a peculiar animal matter in solution.
Gregory Watt is just returned from the Continent, where he has
passed the last fifteen months. He has been much delighted with his
excursion, but his health is at present bad. I trust, however, that
English roast-beef and English customs will speedily restore it.
We are publishing, at the Royal Institution, a Journal of Science,
which contains chiefly abridged accounts of what is going on in
different parts of Europe, with some original papers; and in hopes
that its diffusion may become more general, we have fixed its price
at one shilling. As soon as I have an opportunity, I will send you
the last numbers of it.
I am beginning to think of my Course of Lectures for the winter. In
addition to the common course of the Institution, I have to deliver
a few lectures on Vegetable Substances, and on the connection
of Chemistry with Vegetable Physiology, before the Board of
Agriculture. I have begun some experiments on the powers of soils
to absorb moisture, as connected with their fertility. I have, for
this purpose, made a small collection of those of the _calcareous_
and _secondary_ countries, and I wish very much for some specimens
from the _granitic_ and _schistose_ hills of Cornwall. If you
could, without much trouble, cause to be procured from your
estates different pieces of uncultivated soil, of about a pound
weight each, I should feel much obliged to you. They should be
accompanied by specimens of the stone or strata on which they lie.
I am, dear Sir, with affection and respect, yours,
H. DAVY.
Of the Journals alluded to in the above letter, it would seem that
Davy and Dr. Young were the joint editors. The former appears both
as a reviewer and an original writer, and in each capacity we
recognise the peculiarities of his genius: in the one case, by the
quickness with which he detects error; and in the other, by the
avidity with which he apprehends truth.
It will not be uninteresting to take a short review of his original
communications, especially as the work has become extremely scarce;
indeed, as it was published in numbers, it is very probable that
only a few copies have escaped the common fate of periodicals.
His first paper is entitled, "An Account of a New Eudiometer," and
has for its principal object the recommendation of the solution of
the green muriate, or sulphate of iron, impregnated with _nitrous_
gas; the knowledge of the properties of which, in absorbing oxygen
gas, arose out of those experiments to which an allusion has been
already made.[40]
[40] See page 88.
This test is prepared by transmitting a current of nitrous
gas through a saturated solution of the salt of iron. As the
absorption of the gas proceeds, the solution acquires the colour
of a deep olive brown; and when the impregnation is completed,
it appears opaque and almost black. The process is apparently
owing to a simple elective attraction; in no case is the gas
decomposed; and under the exhausted receiver it resumes its elastic
form, leaving the fluid with which it was combined, unaltered in
its properties. The test, therefore, can only be regarded as a
convenient modification of that of Priestley, in which the nitrous
gas was presented to the atmospheric air to be examined, without
the intervention of any third body.
The only apparatus required for the application of the test, as
suggested by Davy, is a small graduated tube, having its capacity
divided into one hundred parts, and a vessel for containing the
fluid. The tube, after being filled with the air to be examined, is
introduced into the solution, and shaken in contact with it; when
the air will be rapidly diminished in volume, and the whole of its
oxygen, in a few minutes, condensed into nitrous acid.
By means of this test, Davy informs us that he examined the
atmosphere in different places, without being able to ascertain any
notable difference in the proportions of its component parts.
Twenty-eight years have elapsed since the publication of this
paper; and yet, amidst the rapid progress of discovery, Eudiometry
has not been able even to modify the results it has given us; but
the reader will be pleased to remember, that by these tests it is
only professed to show the relative proportions of oxygen in air;
the salubrity of an atmosphere depends upon many other causes,
especially its condition with regard to moisture, which, in a
variety of ways, exerts an influence upon the structures of the
body.
In this Journal we also find several original communications from
Davy on galvanic phenomena, which will be noticed on a future
occasion. There is likewise a paper of considerable interest,
entitled, "An Account of a method of copying Paintings upon Glass,
and of making Profiles, by the agency of Light upon Nitrate of
Silver, invented by T. Wedgwood, Esq.: with Observations by H.
Davy."
In the first place, he gives an account of the experiments of Mr.
Wedgwood, and then, with his usual sagacity, extends our knowledge
of the subject by his own researches.
Chemists had been long acquainted with the fact, that white paper,
or white leather, moistened with a solution of the _nitrate of
silver_, although it does not undergo any change when kept in
a dark place, will speedily change colour on being exposed to
daylight; and that, after passing through different shades of grey
and brown, it will at length become nearly black. These alterations
in colour take place more speedily in proportion as the light is
more intense. In the direct beams of the sun, two or three minutes
are sufficient,--in the shade, several hours are required, to
produce the full effect; and light transmitted through differently
coloured glass, acts upon it with different degrees of intensity.
It is found, for instance, that red rays, or the common sunbeams
passed through red glass, have very little action upon it; yellow
and green are more efficacious; but blue and violet produce the
most decided and powerful effects. Davy observes that these facts
were analogous to those which were long ago observed by Scheele,
and confirmed by Senebier.
To Mr. Wedgwood, however, belongs the merit of having first applied
them for the ingenious purpose of copying engravings, &c. His first
attempt was to copy the images formed by the _camera obscura_; but
they were found to be too faint to produce, in any moderate time,
the necessary changes upon the _nitrate of silver_. With paintings
on glass he was more successful; for the copying of which, the
solution should be applied on leather, which is more readily acted
upon than paper. When a surface thus prepared is placed behind a
painting on glass, exposed to the solar light, the rays transmitted
through the differently coloured surfaces produce distinct tints of
brown or black, sensibly differing in intensity, according to the
shades of the picture; and where the light is unaltered, the colour
of the _nitrate_ becomes deepest.
Besides this application of the method of copying, there are many
others. It may be rendered subservient for making delineations of
all such objects as are possessed of a texture partly opaque, and
partly transparent; such, for instance, as the woody fibres of
leaves, and the wings of insects; for which purpose, it is only
necessary to cause the direct solar light to pass through them, and
to receive the shadows upon prepared leather.
To Davy we are indebted for an extremely beautiful application
of this principle,--that of copying small objects produced by
means of the solar microscope. For the success, however, of this
experiment, it is necessary that the prepared leather should be
placed at a small distance only from the lens.
The copy of a painting, or the profile of an object, thus obtained,
must of course be preserved in an obscure place; for all the
attempts that have been made to prevent the uncoloured parts
of the copy from being acted upon by light, have hitherto been
unsuccessful. They have been covered with a thin coating of fine
varnish; and they have been submitted to frequent washings; yet,
even after this latter operation, it would seem that a sufficient
quantity of the active matter will still adhere to the white parts
of the surface, and cause them to become dark on exposure to the
rays of the sun. From this circumstance, Davy thinks it probable
that a portion of the metallic oxide abandons its acid, to enter
into union with the animal or vegetable substance, so as to form
with it an insoluble compound.
It will be remembered that Davy had made some early experiments on
the collision of flint and steel _in vacuo_:[41] we find in the
Royal Institution Journal a farther investigation of the subject;
when he admits that, although sparks are not produced under these
circumstances, yet that a faint light becomes visible. In many
instances, he refers the phenomenon to electricity excited by
friction, more especially in the instances of glass, quartz, sugar,
&c. which give out light when rubbed. In other cases, he considers
it probable that a species of phosphorescence may be occasioned
by the heat; and he thinks that there may occasionally take place
an actual ignition of abraded particles, in consequence of their
imperfect conducting power: a supposition which he thinks receives
strong support from an experiment of Mr. Wedgwood, who found that a
piece of window-glass, when brought into contact with a revolving
wheel of grit, became red hot at its point of friction, and gave
off luminous particles that were capable of inflaming gunpowder and
hydrogen gas.
[41] See page 67.
We shall also find in this volume an account of some observations
which he made upon the motions of small pieces of _acetate of
potash_, during their solution, upon the surface of water. After
the interesting and extraordinary observations of Mr. Brown, every
phenomenon of this kind is calculated to excite attention.
Davy states that the fragments were agitated by very singular
motions during the time of their solution, sometimes revolving for
a second or two, and then moving rapidly backwards and forwards
in various directions. He considers the phenomenon as evidently
connected with the rapid process of solution, since the motions
became weaker as the point of saturation approached. The thinnest
film of oil, or of ether, wholly destroyed the effect. Those pieces
which were most irregular in their forms underwent, by far, the
most rapid motions; from which, he thinks, it would appear, that
the phenomenon was in some measure owing to changes in the centre
of gravity of the particles during their solution. The projectile
motions, however, would seem to depend upon the continual descent
of a current of the saline solution from the agitated particle,
in consequence of which, the surrounding water would press upon
different parts of it with different degrees of force. Besides
which, an increase of temperature, which was found to accompany the
solution of the salt, might in a degree modify the effect.
His first communication to the Royal Society was entitled "An
Account of some Galvanic Combinations, formed by an arrangement
of single metallic plates and fluids, analogous to the Galvanic
Apparatus of M. Volta."
It was read on the 18th of June 1801, and will be examined in a
future part of these memoirs.
The certificate, recommending him as a candidate for the honour
of a seat in the Royal Society, was read for the first time on
the 21st of April 1803; and having been duly suspended in the
meeting-room, during ten sittings of the Society, according to
the statute, he was put to the ballot, and elected on the 17th of
November in the same year.
As every circumstance connected with the progress of Davy will be
hereafter viewed with considerable interest, I shall here introduce
the form of the certificate, and record the names of those Fellows
who sanctioned it by their signatures.
"HUMPHRY DAVY, ESQ. Professor of Chemistry in the Royal Institution
of Great Britain, a gentleman of very considerable scientific
knowledge, and author of a paper in the Philosophical Transactions,
being desirous of becoming a Fellow of the Royal Society, we
the undersigned do from our personal knowledge recommend him
as deserving that honour, and as likely to prove an useful and
valuable member.
(Signed) MORTON,
R. J. SULLIVAN,
KINNAIRD,
CHARLES HATCHETT,
THOMAS YOUNG,
WEBB SEYMOUR,
W. G. MATON,
THOMAS RACKETT,
JAMES EDWARD SMITH,
W. G. JORDAN,
JOHN WALKER,
RICHARD CHENEVIX,
ALEXANDER CRICHTON,
HENRY C. ENGLEFIELD,
CHARLES WILKINS,
GIFFIN WILSON,
GILBERT BLANE,
EDWARD FORSTER."
On the 7th of July, in the same year, he was elected an Honorary
Member of the Dublin Society, having been proposed from the chair
by the Vice-President, General Vallancey.
It has been stated that, shortly after Davy's arrival at the
Institution, the Managers, being anxious to encourage all
investigations of a practical tendency, directed him to deliver
a series of lectures on the art of tanning. With this view, he
entered into a scientific examination of the subject, in which he
was encouraged by Sir Joseph Banks, the liberal patron and promoter
of all useful knowledge, who supplied him with various materials
for experiment.
The subject had recently attracted considerable attention, both at
home and abroad, but much still remained to be effected; and Davy
succeeded in adding many important facts to the general store.
In the Royal Institution Journal already noticed, we find several
communications from him, under the titles of "Observations on
different methods of obtaining Gallic Acid;"--"On the processes
of Tanning," &c. All the new facts however, discovered in the
course of his experiments, were embodied in a long and elaborate
memoir, which was read before the Royal Society on the 24th of
February 1803, and published in the Philosophical Transactions
for that year. It was entitled "An Account of some Experiments
and Observations on the constituent parts of certain astringent
Vegetables, and on their operation in Tanning. By Humphry Davy,
Professor of Chemistry in the Royal Institution. Communicated by
the Right Honourable Sir Joseph Banks, P. R. S."
Although Seguin and Proust had already examined many of the
properties of that vegetable principle to which the name of
_tannin_ had been given, yet its affinities had been but little
examined; and the manner in which its action upon animal matters
may be modified by combination with other substances, had been
still less considered.
His principal design in this enquiry was to elucidate the practical
part of the art of tanning skins, so as to form leather; but
in pursuing this object, he was necessarily led into chemical
investigations connected with the analysis of the various bodies
containing the tanning principle, and the peculiar properties and
value of each.
The vegetable principles that had been regarded as more usually
present in astringent infusions, are _tannin_, _gallic acid_,
and _extractive matter_. In attempting to ascertain the relative
proportions of _tannin_ contained in different infusions, Davy was
led, after various trials, to prefer the generally received method
of precipitating by means of _gelatine_ procured from isinglass. In
using this test, however, he discovered that several precautions
were necessary;--that the solution should be quite fresh,--that
it should be as much saturated as may be compatible with its
fluidity,--and that the precipitate obtained should be reduced to a
uniform degree of dryness.
It is evident that if the quantity of gelatine in the solution,
employed as the precipitant, be known, it will only be necessary to
ascertain the weight of the precipitate produced by it, in order to
learn the absolute proportion of tannin present in any specimen.
He next directed his attention to the discovery of some method
by which the _gallic acid_ might be separated from _extractive
matter_, in cases where they exist in combination, but the enquiry
was not successful; for, as he observes, it is difficult to render
the _extractive_ insoluble, so as to separate it, without at the
same time decomposing the gallic acid. It is true that æther will
dissolve the latter, without exerting much action upon the former;
but then, he adds, whenever the gallic acid is in large quantities,
this method will fail, "in consequence of that _affinity_ which is
connected with mass." Here then he adopts that celebrated theory of
Berthollet,[42] which he afterwards so vigorously and successfully
attacked.[43]
[42] Récherches sur les Lois de l'Affinité.--Mém. de l'Institut
National, Tome III. p. 5.
[43] The masterly manner in which he combated the successive
arguments of Berthollet upon this question is admirable. In the
first place, he attacked the theory upon general principles, and
then exposed the fallacy of the several experiments adduced in
its support. "Were the proposition correct, that _in all cases
of decomposition in which two bodies act upon a third, that
third is divided between them in proportion to their relative
affinities, and their quantities of matter_, it is quite evident
that there could be scarcely any definite proportions: a salt
crystallizing in a strong alkaline solution would be strongly
alkaline; in a weak one, less alkaline; and in an acid solution
it would be acid." With regard to glasses and alloys, adduced
by M. Berthollet as compounds of indefinite proportions, Davy
answers--"It is not easy to prove, in such cases, that the
elements are chemically combined, for the points of fusion of
alkali, glass, and certain metallic oxides, are so near to each
other, that transparent mixtures of them may be formed." The
experiment upon which M. Berthollet laid great stress, viz.
that a large quantity of potash will separate a small quantity
of sulphuric acid from sulphate of baryta, Davy invalidates in
a most complete manner. He says--"This experiment was made in
contact with the atmosphere, in which carbonic acid is always
present; and carbonate of potash and sulphate of baryta mutually
decompose each other."
As general tests of the respective quantities of these two
principles (gallic acid and extractive matter), he employed the
solutions of the salts of alumina and those of the peroxidated
salts of iron. The former of these precipitates _extractive_,
without materially acting upon _gallic acid_, which is thrown down
by the latter: the greatest care, however, must be taken not to add
the iron in excess, as in that case the black precipitate formed
will be redissolved, and an olive-coloured and clear fluid be only
obtained.
He details the results of a number of experiments made upon galls,
and ascertains the relative proportions of their several elements;
and he proves that tannin may exist in such a state of combination
in different substances as to elude the test of gelatine; in which
case, to detect its presence, it is necessary to have recourse to
the action of the diluted acids.
Sir Joseph Banks had concluded, from the sensible properties of
_catechu_,[44] or _terra Japonica_, that it was rich in tannin:
Davy confirmed this opinion by experiment. The leather tanned by
it appeared to possess the same qualities as when tanned in the
usual manner; and although this substance contains a small portion
of extractive matter, yet the increase of weight of the skin was
rather less than when solutions of galls were used.
[44] Catechu is an extract obtained from the wood of a species
of the _Mimosa_ that grows in India, by boiling and subsequent
evaporation. It is of two kinds; one from Bengal, the other from
Bombay. The former contains rather less, the latter rather more,
than half its weight of tannin. The remainder in both cases is a
peculiar extractive matter mixed with mucilage.--P.
In examining different barks, he was not able to procure from them
any free gallic acid, but their infusions gave, on evaporation,
tannin and extractive. The greater number of his experiments were
made on the barks of the oak, the Leicester willow, the Spanish
chestnut, the elm, and the common willow. The largest quantity of
tannin he found to be contained in the interior, or white cortical
layers; and the largest quantity of extractive matter in the
exterior layers; the epidermis, or rough outward bark, did not
contain either the one or the other.
From his general observations he is inclined to suppose that, in
all the astringent vegetables, the tannin is of the same species,
and that all the differences attributed to it depend upon its state
of combination with other principles.
In applying the results of his experiments to the theory of
tanning, he considers the process as simply depending upon the
union of the tannin with the matter of the skin, in such a manner
as to form with it an insoluble compound. Gallic acid, he feels
assured, does not produce any notable effects in the process; but
he thinks that the quality of the leather depends, in some degree,
upon the quantity of extractive matter it may imbibe.
Skin, combined with extractive matter only, would be increased in
weight, become coloured, and be extremely flexible, but it would
not be insoluble in water; and were it combined with tannin alone,
it would be heavier and less supple than when both these principles
enter into the compound.
He examines with great acuteness and precision some of the more
popular opinions entertained by tanners, and brings his science to
bear very satisfactorily upon several of their processes.
The grand secret, on which the profit of the trade mainly depends,
is to give the hides the greatest increase of weight in the least
possible time. To effect this, various schemes have been proposed,
many of which, from the ignorance of the operators, instead of
promoting, have defeated the object. Different _menstrua_ have been
suggested for expediting the process, and amongst them lime-water
and the solutions of pearl-ash; but, as he has clearly shown,
these two substances form compounds with tannin which are not
decomposable by gelatine; whence it follows that their effects must
be pernicious; and there is very little reason to suppose that any
bodies will be found which, at the same time that they increase
the solubility of tannin in water, will not likewise diminish its
attraction for skin.
His experiments having proved that the saturated infusions of
astringent barks contain much less extractive matter, in proportion
to their tannin, than those which are weaker, it follows, that by
quickly tanning the skin, we render the leather less durable. These
observations show that there is some foundation for the vulgar
opinion of workmen, concerning what is technically called the
_feeding_ of leather in the slow method of tanning.
Such is an outline of this interesting paper, in which the author
has displayed the talent so characteristic of his mind--that of
bringing science and art into useful alliance with each other.
It forms, at this day, the guide of the tanner; and those who
previously carried on the process by a routine of operations, of
which they knew not the reasons, are now capable of modifying it,
without the risk of spoiling the result. Many of those expedients
which have been brought forward as novelties in later years, may
be found in this paper; or, at least, have arisen out of the
principles disclosed during his investigations.
It has been stated that, shortly after Davy's successful _début_
as a lecturer, his manners underwent a change, and that, to the
regret of his friends, he lost much of his native simplicity. On
the 5th of February 1802, he had dined with Sir Harry Englefield
at his house at Blackheath; and eighteen years afterwards, the
worthy Baronet alluded to his interesting demeanour upon that
occasion, in terms sufficiently expressive of his feelings--"It was
the last flash of expiring Nature." It was natural that his best
friends, on perceiving this change of manner, should entertain some
apprehensions as to the deeper qualities of his heart. Mr. Purkis
has placed in my hands the following letter addressed to him by Mr.
Coleridge; it will interest the reader by the force and truth with
which its talented writer characterises the perils which beset the
elevated path of the young philosopher at the commencement of his
career.
TO SAMUEL PURKIS, ESQ.
Nether Stowey, Feb. 17, 1803.
MY DEAR PURKIS,
I received your parcel last night, by post, from Gunville, whither
(crossly enough) I am going with our friend Poole to-morrow
morning. I do from my very heart thank you for your prompt and
friendly exertion, and for your truly interesting letter. I shall
write to Wedgwood by this post; he is still at Cote, near Bristol;
but I shall take the _Bang_ back with me to Gunville, as Wedgwood
will assuredly be there in the course of ten days. Jos. Wedgwood is
named the Sheriff of the County. When I have heard from Wedgwood,
or when he has tried this _Nepenthe_, I will write to you. I have
been here nearly a fortnight; and in better health than usual.
Tranquillity, warm rooms, and a dear old friend, are specifics for
my complaints. Poole is indeed a very, very good man. I like even
his incorrigibility in small faults and deficiencies: it looks
like a wise determination of Nature to let well alone; and is a
consequence, a necessary one perhaps, of his immutability in his
important good qualities. His journal, with his own comments, has
proved not only entertaining but highly instructive to me.
I rejoice in Davy's progress. There are three Suns recorded in
Scripture:--Joshua's, that stood still; Hezekiah's, that went
backward; and David's, that went forth and hastened on his course,
like a bridegroom from his chamber. May our friend's prove the
latter! It is a melancholy thing to see a man, like the Sun in the
close of the Lapland summer, meridional in his horizon; or like
wheat in a rainy season, that shoots up well in the stalk, but does
not _kern_. As I have hoped, and do hope, more proudly of Davy than
of any other man; and as he has been endeared to me more than any
other man, by the being a Thing of Hope to me (more, far more than
myself to my own self in my most genial moments,)--so of course my
disappointment would be proportionally severe. It were falsehood,
if I said that I think his present situation most calculated,
of all others, to foster either his genius, or the clearness
and incorruptness of his opinions and moral feelings. I see two
Serpents at the cradle of his genius, Dissipation with a perpetual
increase of acquaintances, and the constant presence of Inferiors
and Devotees, with that too great facility of attaining admiration,
which degrades Ambition into Vanity--but the Hercules will strangle
both the reptile monsters. I have thought it possible to exert
talents with perseverance, and to attain true greatness wholly
pure, even from the impulses of ambition; but on this subject Davy
and I always differed.
When you used the word "gigantic," you meant, no doubt, to give
me a specimen of the irony I must expect from my Philo-Lockian
critics. I trust, that I shall steer clear of almost all offence.
My book is not, strictly speaking, metaphysical, but historical.
It perhaps will merit the title of a History of Metaphysics in
England from Lord Bacon to Mr. Hume, inclusive. I confine myself
to facts in every part of the work, excepting that which treats of
Mr. Hume:--_him_ I have assuredly besprinkled copiously from the
fountains of Bitterness and Contempt. As to this, and the other
works which you have mentioned, "have patience, Lord! and I will
pay thee all!"
Mr. T. Wedgwood goes to Italy in the first days of May. Whether I
accompany him is uncertain. He is apprehensive that my health may
incapacitate me. If I do not go with him, (and I shall be certain,
one way or the other, in a few weeks,) I shall go by myself, in the
first week of April, if possible.
Poole's kindest remembrances I send you on my own hazard; for he
is busy below, and I must fold up my letter. Whether I remain in
England or am abroad, I will occasionally write you; and am ever,
my dear Purkis, with affectionate esteem,
Your's sincerely,
S. T. COLERIDGE.
Remember me kindly to Mrs. Purkis and your children. T. Wedgwood's
disease is not painful: it is a complete _tædium vitæ_; nothing
pleases long, and novelty itself begins to cease to act like
novelty. Life and all its forms move, in his diseased moments, like
shadows before him, cold, colourless, and unsubstantial.
From the tone of the following letter, it may be presumed also,
that Mr. Poole, to whom it is addressed, had expressed some anxiety
upon the dangers to which his flattering station exposed him.
TO THOMAS POOLE, ESQ.
London, May 1, 1803.
MY DEAR POOLE,
Have you no thoughts of coming to London? I have always recollected
the short periods that you have spent in town, with a kind of mixed
feeling of pleasure and regret.
In the bustling activity occasioned in cities by the action and
re-action of diversified talents, occupations, and passions, our
existence is, as it were, broken into fragments, and with you I
have always wished for unbroken intercourse and continuous feeling.
* * * * *
Be not alarmed, my dear friend, as to the effect of worldly society
on my mind. The age of danger has passed away. There are in the
intellectual being of all men, permanent elements, certain habits
and passions that cannot change. I am a lover of Nature, with an
ungratified imagination. I shall continue to search for untasted
charms,--for hidden beauties.
My _real_, my _waking_ existence is amongst the objects of
scientific research: common amusements and enjoyments are necessary
to me only as dreams, to interrupt the flow of thoughts too nearly
analogous to enlighten and to vivify.
Coleridge has left London for Keswick; during his stay in town, I
saw him seldomer than usual; when I did see him, it was generally
in the midst of large companies, where he is the image of power and
activity. His eloquence is unimpaired; perhaps it is softer and
stronger. His will is probably less than ever commensurate with
his ability. Brilliant images of greatness float upon his mind:
like the images of the morning clouds upon the waters, their forms
are changed by the motion of the waves, they are agitated by every
breeze, and modified by every sunbeam. He talked in the course of
one hour, of beginning three works, and he recited the poem of
Christobel unfinished, and as I had before heard it. What talent
does he not waste in forming visions, sublime, but unconnected with
the real world! I have looked to his efforts, as to the efforts of
a creating being; but as yet, he has not even laid the foundation
for the new world of intellectual forms.
When my Agricultural Lectures are finished, I propose to visit
Paris, and perhaps Geneva. How I regret that circumstances had not
enabled us to make the same tour at the same time! I think, at
all events, I shall see you before the Autumn, on your own lands,
amidst your own images and creations.
Your affectionate friend,
HUMPHRY DAVY.
TO THE SAME.
Royal Institution.
MY DEAR POOLE,
Often, very often, in the midst of the tumults of the multitude in
this great city, has my spirit turned in quietness and solitude
towards you.
I hope soon to see you in Somersetshire, where we may worship
Nature, and the spirit that dwells in Nature, in your green fields
and under your tranquil sky. My communications with you and
Coleridge and Southey, and other ornaments of the great existing
Being, have excited feelings which cheer me in the apathy of
London, and which make me love human nature.
* * * * *
Your account of the young man who murdered his wife, I read with
deep interest. It is from such narratives of the conduct of common
persons, that the laws of simple human nature must be deduced.
Beings acted on by few objects, awakening in them few but deep
passions, are the beings which Metaphysicians and Moralists ought
to study; not those who exist in general life, having their
energies and feelings so attached to multiplied and indefinite
things--so mixed up and connected with myriads of circumstances, as
to be imperceptible, unless by a microscopic moral eye.
I am, &c. &c.
H. DAVY.
From the former letter, we learn that Davy, at this period,
proposed delivering some lectures on the Chemistry of Agriculture.
From the memorandums of my late friend Mr. Arthur Young, the
celebrated Secretary to the Board of Agriculture, I have succeeded,
through the kindness of his daughter, in procuring the following
extracts; the only source from which I have been able to obtain any
correct information upon this point in his scientific life.--"May
15th, 1803. _Mem._ Two lectures by Mr. Davy have taken place, and
been very well attended; they intend retaining him by a salary of
a hundred pounds a year,--a very good plan."
Amongst the pamphlets at Bradfield Hall is a small quarto of
fourteen pages, entitled, "Outlines of a Course of Lectures on
the Chemistry of Agriculture, to be delivered before the Board
of Agriculture, 1803." It was evidently only printed for private
circulation amongst the members. At the same time, he printed a
small pamphlet, containing an explanation of the terms used in
chemistry, for the instruction of those amongst his audience who
had not particularly directed their attention to the science.
The first lecture was delivered on Tuesday, May the 10th, at twelve
at noon, and five others on the succeeding Tuesdays and Fridays.
In an address to the Board of Agriculture by Sir John Sinclair,
delivered in April 1806, in reviewing the various objects to which
the attention of the Board had been directed, he thus alludes to
the subject:--"In the year 1802, when my Lord Carrington was in the
chair, the Board resolved to direct the attention of a celebrated
lecturer, Mr. Davy, to agricultural subjects; and in the following
year, during the Presidency of Lord Sheffield, he first delivered
to the members of this Institution, a course of lectures on the
CHEMISTRY OF AGRICULTURE. The plan has succeeded to the extent
which might have been expected from the abilities of the gentleman
engaged to carry it into effect. The lectures have hitherto been
exclusively addressed to the Members of the Board; but to such a
degree of perfection have they arrived, that it is well worthy
of consideration, whether they ought not to be given to a larger
audience. If such an idea met with the approbation of the Board,
a hall might be procured for that purpose, or a special course of
lectures read in this room exclusively for strangers."
Davy would appear to have been very early impressed with
the importance of Chemistry, in its various applications to
Agriculture. Allusions are constantly made to it in his letters;
and at the conclusion of his "RESEARCHES," he glances at this
department of the chemistry of vegetation, and observes that,
"although it is immediately connected with the art upon which we
depend for subsistence, it has been but little investigated."
In his introductory lecture of 1802, he speaks more forcibly upon
the subject.
"Agriculture, to which we owe our means of subsistence, is an
art intimately connected with chemical science; for although the
common soil of the earth will produce vegetable food, yet it can
only be made to produce it in the greatest quantity, and of the
best quality, by methods of cultivation dependent upon scientific
principles.
"The knowledge of the composition of soils, of the food of
vegetables, of the modes in which their products must be treated,
so as to become fit for the nourishment of animals, is essential to
the cultivator of land; and his exertions are profitable and useful
to society, in proportion as he is more of a chemical professor.
Since indeed the truth has been understood, and since the
importance of agriculture has been generally felt, the character of
the agriculturist has become more dignified, and more refined;--no
longer a mere machine of labour, he has learned to think, and to
reason. He is aware of his usefulness to his fellow-men, and he is
become, at once, the friend of nature, and the friend of society."
His appointment, as chemical professor to the Board of Agriculture,
was accompanied with the obligation of reading lectures before its
members; which he continued to deliver every successive season for
ten years, modifying and extending their views, from time to time,
in such a manner as the progress of chemical discovery might render
necessary.
These discourses were collated, and published in the year 1813,
at the request of the President and members of the Board, and
they form the only systematic work we, at present, possess on the
subject. Its views, however, are too generally interesting to be
briefly dismissed; I shall therefore enter more fully into their
merits in a more advanced part of these memoirs.
His connexion with the Board necessarily brought him in contact
with the practical agriculturists and capitalists of the day, with
many of whom he formed friendships which lasted through life. With
Mr. Coke of Holkham he became well acquainted, and generally formed
one of the party at his annual sheep-shearing.[45] He was also a
frequent visitor at Woburn, and received from the Duke the means
by which he was enabled to submit to the test of practice various
theories which his science had suggested.
[45] In the 40th volume of the "Annals of Agriculture," an
account is given of the Holkham Sheep-shearing for 1803, and in
the list of the company is the name of "Mr. Professor Davy."--At
the meeting of 1808, he was also present, and is mentioned as the
great chemist, whose discoveries will immortalize his name. Mr.
Coke, in the course of his speech after dinner, alluding to the
question of long and short dung, said, "It is the opinion of a
friend of mine, who sits near me, Professor Davy, and upon whose
judgment, on account of his extensive chemical as well as other
scientific knowledge, I place the highest reliance, that the
manure carried immediately on the field, without being disturbed,
will have a greater effect in exciting rapid vegetation, and in
encouraging the growth of the turnip plant, than when applied
in the ordinary manner; for, under such circumstances, it will
not only be more moist and alkaline, but it will be protected
from a loss of substance, amounting very nearly to one-third of
its original bulk." Davy afterwards, in company with the Duke of
Bedford, Lord William Russell, Lord Thanet, Sir Joseph Banks,
and other agriculturists, inspected several farms.--In 1812, his
health was drunk at the Woburn Sheep-shearing by the Duke of
Bedford; and in the following festival it was proposed by Lord
Hardwicke.
In the print of the "Woburn Sheep-shearing," published by
Garrard, in 1811, No. 75 represents Davy; he is standing, in a
listening attitude, behind Mr. Coke, who is conversing with Sir
Joseph Banks, Sir John Sinclair, and Mr. Arthur Young.
In a letter to Mr. Gilbert, dated October 1803, he says: "I have
just quitted the coast of Sussex, where I have spent the last three
weeks with Lord Sheffield, the worthy biographer of Gibbon." In
fact, there was not a nobleman, distinguished for intellectual
superiority, who did not feel a pride in receiving him as a guest;
and he passed his vacations in the society of those exalted persons
who, in possessing rank, fortune, and talents, felt that they only
held such gifts from Providence, in trust for the welfare of their
fellow-countrymen.
We can scarcely picture to ourselves a being upon whom fortune
ever showered more favours than upon Davy, during this golden
period of his career. Independent in an honourable competence, the
product of his genius and industry; resident in the centre of all
scientific information and intelligence; every avenue of knowledge,
and every mode of observation open to his unwearied intellect, he
must have experienced a satisfaction which few philosophers have
ever before felt,--the power of pursuing experimental research to
any extent, and of commanding the immediate possession of all the
means it might require, without the least regard either to cost
or labour. What a contrast does this picture afford to that which
has been too faithfully represented as the more usual fate of the
philosopher and man of letters, and which exhibits little more than
the unavailing struggles of genius against penury! Instead of a
life consumed in fruitless expectation of patronage and reward, we
behold Davy, in the full bloom of reputation, courted by all whom
rank, talent, or station, had rendered conspicuous.
His life flowed on like a pure stream, under a sky of perpetual
sunshine,--not a gust ruffled its surface, not a cloud obscured its
brightness. In the morning, he was the sage interpreter of Nature's
laws; in the evening, he sparkled in the galaxy of fashion; and
not the least extraordinary point in the character of this great
man, was the facility with which he could cast aside the cares of
study, and enter into the trifling amusements of society.--"_Ne
otium quidem otiosum_," was the exclamation of Cicero; and it
will generally apply to the leisure of men actively engaged in
the pursuits of science; but Davy, in closing the door of his
laboratory, opened the temple of pleasure. When not otherwise
engaged, his custom was to play at billiards, frequent the theatre,
or read the last new novel. In ordinary cases, the genius of
evening dissipation is an arrant Penelope; but Davy, on returning
to his morning labours, never found that the thread had been unspun
during the interruption.
The following anecdote is well calculated to illustrate that
versatility of talent of which I have frequently spoken, as
well as the power he possessed of abstracting himself, without
detriment, from the most elaborate investigations. A friend of the
late Mr. Tobin called upon him at the Institution, and found him
deeply engaged in the laboratory; their conversation turned upon
"The Honey Moon," which was to be brought out on the following
evening.[46] No sooner had Davy heard that, although pressing
applications had been made to several of the poets of the day, a
Prologue had not yet been written, than he instantly quitted the
laboratory, and in two hours produced that which was recited on the
occasion by Mr. Bartley, and printed in the first edition of the
comedy. I insert it in this place.
[46] "The Honey Moon" was produced at Drury Lane, on Thursday,
the 30th of January, 1805.
No uniformity in life is found:--
In ev'ry scene varieties abound;
And inconsistency still marks the plan
Of that immortal noble being,--Man.
As changeful as the April's morning skies,
His feeling and his sentiments arise;
And Nature to his wond'rous frame has given
The mingled elements of Earth and Heaven.
In diff'rent climes and ages, still we find
The same events for different ends design'd:
And the same passion diff'rent minds can move
To thoughts of sadness or to acts of love.
Hence Genius draws his novel copious store;
And hence the new creations we adore:
And hence the scenic art's undying skill
Submits our feeling to its potent will;
From common accidents and common themes
Awakens rapture and poetic dreams;
And, in the trodden path of life, pursues
Some object clothed in Fancy's loveliest hues--
To strengthen nature, or to chasten art,
To mend the manners or exalt the heart.
So thought the man whom you must judge to-night;
And as he thought, he boldly dared to write.
Not new the subject of his first-born rhyme;
But one adorn'd by bards of elder time;--
Bards with the grandest sentiments inspired--
Bards that in rapture he has still admired;
And tried to imitate, with ardour warm,
And catch the spirit of their pow'rful charm.
With loftiest zeal and anxious hope, he sought
To bring to modern times their strength of thought;
And, in their glowing colours, to display
The follies and the virtues of the day.
Whether his talents have his wish belied,
Your judgment and your candour must decide.
He, though your loftiest plaudits you should raise--
He cannot thank you for the meed of praise.
Rapture he cannot feel, nor fear, nor shame;
Connected with his love of earthly fame,
He is no more.--Yet may his memory live
In all the bloom that early worth can give!
Should you applaud, 'twould check the flowing tear
Of those to whom his name and hopes are dear.
But should you an unfinish'd structure find,
As in its first and rudest forms design'd,
As yet not perfect from the glowing mind,
Then with a gentle voice your censure spread,
And spare the living--spare the sacred DEAD!
Davy would appear to have frequently amused himself with writing
sonnets, and inclosing them in letters to his several friends: the
following letter will also show that he was ambitious of being
considered a poet.
TO SAMUEL PURKIS, ESQ.
MY DEAR PURKIS,
I inclose the little poem,[47] on which your praise has stamped a
higher value, I fear, than it deserves.
If I thought that people in general would think as favourably of my
poetical productions, I would write more verses, and would write
them with more care; but I fear you are partial: I am very glad,
however, that you like the little song; at some future period I
will send you another.
With kind remembrances, unalterably your sincere friend,
H. DAVY.
[47] The subject was "_Julia's Eyes_."
On examining the laboratory notes made at this period, many of
which, however, are nearly illegible from blots of ink and stains
of acid, it would appear that his researches into the composition
of mineral bodies were most extensive, and that he obtained many
new results, of which he does not seem to have availed himself
in any of his subsequent papers. To borrow a metaphor from his
favourite amusement, he treated such results as small fry, which
he returned to their native element to grow bigger, or to be again
caught by some less aspiring brother of the angle.
Had Davy, at this period of his life, been anxious to obtain
wealth,[48] such was his chemical reputation, and such the value
attached to his judgment, that, by lending his assistance to
manufacturers and projectors, he might easily have realized it; but
his aspirations were of a nobler kind--SCIENTIFIC GLORY was the
grand object for which his heart panted: by stopping to collect the
golden apples, he might have lost the race.
[48] I am assured by one of his earliest friends, that, at this
period, he did not appear even to have an idea of the value of
property. Any thing not immediately necessary to him he gave
away, and never retained a book after he had read it.