THE SAFETY LAMP.
Shortly after Davy’s return to England his sympathy was enlisted in a
cause which enabled him to display all the attributes of his genius,
and to achieve a triumph which, while greatly enhancing his popular
reputation, added no little to his scientific fame. To show him how
he might be useful, was at all times a certain method of securing his
interest; for, like Lavoisier, he was even more the friend of humanity
than of science, and to make science serviceable to humanity was, he
considered, the highest object of his calling.
During the early years of this century the country was repeatedly
shocked by the occurrence of a succession of disastrous colliery
explosions, especially in the north of England, attended by
great destruction of life and property and widespread misery and
destitution. The development of our iron-trade, the improvements in
the steam-engine, and the more general application of machinery to
industry had greatly stimulated the opening out of our coal-fields; and
the working of coal was being extended with a rapidity that greatly
aggravated the evils and dangers at all times inseparable from it.
In the early days of coal-getting, when the pits were shallow and
the workings comparatively near the shafts, fire-damp, although not
unheard of, was little dreaded, and explosions were rare--so rare,
indeed, that when they occurred they were thought worthy of mention
in the _Philosophical Transactions_ of the Royal Society. As the pits
became deeper, and the ways more extended, explosions became more
frequent, and at times it was impossible to work the coal, owing to the
accumulation of fire-damp and its liability to “fire” at the candles of
the miners. In 1732 attempts were first made to ventilate the pits by
“fire-lamps” or furnaces, and by mechanical means, so as to sweep out
the “sulphur” by means of fresh air. Carlisle Spedding, a little later,
invented the steel mill--a contrivance by which a disc of steel was
caused to revolve against a piece of flint, so as to throw off a shower
of sparks sufficiently luminous to enable the miner to carry on his
business.
In spite of the “spark-emitting wheel,” and of the systems of
ventilation introduced by Ryan, James Spedding, John Buddle, and
others, “the swart demon of the mine” grew more and more formidable,
and demanded a greater number of victims every year. Mechanical
science would appear to have spent itself, and the mining world was
gradually coming to look upon fire-damp with the fatalism with which
ignorant and superstitious people regard the plague. Some of the
great coal owners--powerless to do more, but afraid of the rising
tide of public opinion--used their influence with the newspapers
to suppress all allusion to these calamities. But many persons,
especially the physicians and clergymen in the mining districts, who
were witnesses of the suffering and distress which the “firing” of a
mine occasioned, kept public attention alive by means of pamphlets
and letters and notices to such journals as would insert their
communications. One colliery--the Brandling Main or Felling Colliery,
near Gateshead-on-Tyne--acquired an unenviable notoriety from the
frequency with which it fired. On May 25th, 1812, an explosion occurred
which killed ninety-two men and boys. No calamity of such magnitude
had ever happened before in a coal mine. Eighteen months afterwards
a second explosion took place by which twenty-three lives were lost.
In the following year explosions occurred at Percy Main, Hebburn, and
Seafield. In June, 1815, Newbottle Colliery exploded with the loss
of fifty-seven men and boys, and this was immediately followed by a
similar disaster at Sheriff Hill. The Rev. Mr. Hodgson--the historian
of Northumberland--in whose parish the Brandling Main was situated,
published a particular account of the first Felling Colliery Explosion.
This was widely circulated, and ultimately found its way into Thomson’s
_Annals of Philosophy_, which continued to print accounts of similar
accidents as they occurred. At length Mr. J. J. Wilkinson, a barrister
resident in the Temple, suggested the formation of a society to
investigate the whole subject and to seek for remedies. The Bishop of
Durham and the Rev. Dr. Gray, afterwards Bishop of Bristol, but then
Rector of Bishopwearmouth, led the way, and ultimately the society was
instituted on October 1st, 1813, with Sir Ralph Millbanke, afterwards
Sir Ralph Noel, as President. Its first report contains a letter
from Mr. John Buddle, the great authority on the ventilation of coal
mines, in which he expresses his conviction that mechanical agencies
are practically powerless to prevent explosions in mines subjected to
sudden bursts of fire-damp, and he concludes
“that the hopes of this society ever seeing its most desirable
object accomplished must rest upon the event of some method
being discovered of producing such a chemical change upon
carburetted hydrogen gas as to render it innoxious as fast as it
is discharged, or as it approaches the neighbourhood of lights.
In this view of the subject, it is to scientific men only that we
must look up for assistance in providing a cheap and effectual
remedy.”
The society received a number of suggestions, for the most part wholly
impracticable, and generally of the character of that of Dr. Trotter,
who proposed to flood the mines with chlorine. A variety of air-tight
or insulated lamps were suggested by Clanny, Brandling, Murray, and
others, much on the same lines as that devised by Humboldt, but none of
them appears to have been seriously tried.
Under these circumstances it was decided to ask for the co-operation of
Davy, and with that object Mr. Wilkinson called upon him at the Royal
Institution, in the autumn of 1813, but found he had left for Paris.
A few months after his return the Rev. Dr. Gray wrote to him on the
subject, and received the following letter in reply:--
“_August 3, 1815._
“....
“It will give me great satisfaction if my chemical knowledge can
be of any use in an enquiry so interesting to humanity, and I beg
you will assure the committee of my readiness to co-operate with
them in any experiments or investigations on the subject.
“If you think my visiting the mines can be of any use, I will
cheerfully do so.
* * * * *
“I shall be here ten days longer, and on my return South, will
visit any place you will be kind enough to point out to me, where
I may be able to acquire information on the subject of coal gas.”
Dr. Gray, in reply, referred him to Mr. John Buddle, of the Wallsend
Colliery.
On August 24th, 1815, Mr. Buddle wrote to Dr. Gray:--
“Permit me to offer my best acknowledgments for the opportunity
which your attention to the cause of humanity has afforded me of
being introduced to Sir Humphry Davy.
“I was this morning favoured with a call from him, and he was
accompanied by the Rev. Mr. Hodgson. He made particular enquiries
into the nature of the danger arising from the discharge of the
inflammable gas in our mines. I shall supply him with a quantity
of the gas to analyze; and he has given me reason to expect that
a substitute may be found for the steel mill, which will not fire
the gas. He seems also to think it possible to generate a gas,
at a moderate expense, which, by mixing with the atmospheric
current, will so far neutralise the inflammable air, as to
prevent it firing at the candles of the workmen.
“If he should be so fortunate as to succeed in either the one
or the other of these points, he will render the most essential
benefit to the mining interest of this country, and to the cause
of humanity in particular.”
After spending a few days in the district with Mr. Hodgson and Dr.
Gray, in the course of which he saw and experimented with Dr. Clanny’s
lamp, he went on a round of visits in Durham and Yorkshire, and arrived
in London at the end of September. Early in October a quantity of
fire-damp was sent to him by Mr. Hodgson, the receipt of which he
acknowledged on the 15th, saying:--
“My experiments are going on successfully and I hope in a few
days to send you an account of them; I am going to be fortunate
far beyond my expectations.”
Four days afterwards he again wrote to Mr. Hodgson stating that he had
discovered
“that explosive mixtures of mine-damp will not pass through
small apertures or tubes; and that if a lamp or lanthorn be made
air-tight on the sides, and furnished with apertures to admit the
air, it will not communicate flame to the outward atmosphere.”
On the 25th October he gave an account of his work to the Chemical
Club. On October 30th he wrote to Dr. Gray and to Mr. Hodgson, giving a
description of three forms of _safe lamps_. His letter to Dr. Gray was
as follows:--
“As it was the consequence of your invitation that I endeavoured
to investigate the nature of the fire-damp, I owe to you the
first notice of the progress of my experiments.
“My results have been successful far beyond my expectations. I
shall enclose a little sketch of my views on the subject; and I
hope in a few days to be able to send a paper with the apparatus
for the committee. I trust the _safe lamp_ will answer all the
objects of the collier.
“I consider this at present as a private communication. I wish
you to examine the lamps I have had constructed, before you give
any account of my labours to the committee.
“I have never received so much pleasure from the result of any of
my chemical labours; for I trust the cause of humanity will gain
something by it.”
Mr. Hodgson’s letter was shown to several persons, and appears to have
been copied by some, on or about November 2nd, and an extract from it
appeared in Dunn’s “View of the Coal Trade.”
On November 9th Davy read his first paper on the subject before the
Royal Society; it was entitled “On the fire-damp of coal mines, and
on the methods of lighting the mines so as to prevent its explosion.”
After describing the manner in which his attention had been specially
called to the subject, he states that he first made experiments with
a variety of phosphori (Kunckel’s, Canton’s, and Baldwin’s), and also
with the electrical light in close vessels, in the hope that they
might be found to afford the requisite amount of illumination; but the
results were not encouraging.
After an account of the chemical characters of the fire-damp sent to
him by Mr. Hodgson, he describes the results of experiments on its
combustibility and explosive nature, and on the degree of heat required
to explode it when mixed with air. In respect of its combustibility
fire-damp was found to differ most materially from the other common
inflammable gases in that it required a far higher temperature to
effect its inflammation or explosion. Moreover, it was found that the
flame formed by the union of air and fire-damp would not pass through
tubes of a certain minimum diameter;
“and in comparing the power of tubes of metal and those of glass,
it appeared that the flame passed more readily through glass
tubes of the same diameter; and that explosions were stopped
by metallic tubes of one-fifth of an inch when they were an
inch and a half long; and this phenomenon probably depends upon
the heat lost during the explosion in contact with so great
a cooling surface, which brings the temperature of the first
portions exploded below that required for the firing of the other
portions. Metal is a better conductor of heat than glass; and it
has been already shown that fire-damp requires a very strong heat
for its inflammation.”
The observation that mixtures of air and coal-gas would not explode
in very narrow tubes had been previously made, unknown to Davy, by
Wollaston and Tennant. Davy likewise found that explosions would not
pass through very fine wire sieves or wire gauze. He also noted that
an admixture of carbonic acid and nitrogen, even in small proportions,
with explosive mixtures of fire-damp greatly diminished the velocity of
the inflammation.
“... It is evident then, that to prevent explosions in coal mines
it is only necessary to use air-tight lanterns, supplied with
air from tubes or canals of small diameter, or from apertures
covered with wire-gauze placed below the flame, through which
explosions cannot be communicated and having a chimney at the
upper part, as a similar system for carrying off the foul air;
and common lanterns may be easily adapted to the purpose by being
made air-tight in the door and sides, by being furnished with the
chimney and the system of safety apertures below and above. The
principle being known, it is easy to adapt and multiply practical
applications of it.”
[Illustration: DAVY’S EXPERIMENTAL SAFETY LAMPS.]
He then devised a number of lamps on this principle, and subjected
them to trial with explosive mixtures in various ways. The plate
on page 199, copied from the original paper in the _Philosophical
Transactions_, shows the successive forms through which the lamps
passed.
[Illustration]
On January 11th, 1816, he read a second paper to the Royal Society,
entitled, “An account of an invention for giving light in explosive
mixtures of fire-damp in coal mines by consuming the fire-damp,” in
which he shows that the tubes or canals as well as the sides of the
lanterns may be replaced by cages or cylinders of wire gauze. The
inflammable mixture will readily pass through the meshes of the gauze
and will burn within it, filling the cylinder with a bright flame, but
no explosion will pass outwards, even although the wire becomes heated
to redness.
A fortnight later he read a third paper to the Society, “On the
Combustion of Explosive Mixtures confined by Wire Gauze, with some
Observations on Flame,” in which he gives the results of further
inquiries respecting the limits of the size of the apertures, and of
the wire in the metallic gauze required to shield the flame of an
oil-lamp, and describes a number of illustrations of the action of
the gauze in lowering the temperature of the explosive mixture below
the point of ignition. Some of these illustrations are now among the
stock experiments of the lecture theatre. He offers some observations
concerning the essential nature of flame, and concludes by informing
the Society that his “cylinder lamps [_i.e._ lamps of which the flames
are enclosed within a cylinder of gauze: see Fig. 11, p. 199] have been
tried in two of the most dangerous mines near Newcastle with perfect
success.”
The form which the lamp finally took in the hands of Mr. Newman, the
instrument-maker, is seen on p. 200.
The trials above referred to were first made by Mr. Matthias Dunn and
the indefatigable Mr. Hodgson in the Hebburn Colliery, and shortly
afterwards by Mr. John Buddle in the Wall’s End Colliery. Mr. Buddle
has placed on record his impressions of his first experience.
“I first tried it,” he says, “in an explosive mixture on the
surface; and then took it into a mine; ... it is impossible for
me to express my feelings at the time when I first suspended the
lamp in the mine and saw it red hot.... I said to those around me
‘We have at last subdued this monster.’”
Some months afterwards Davy accompanied Mr. Buddle into the pit and saw
his lamp in actual use.
“Sir Humphry was delighted,” says Mr. Buddle, “and I was
overwhelmed with feelings of gratitude to that great genius which
had produced it.”
Further testimony of Mr. Buddle’s appreciation of this memorable
invention may be seen from the following extract from a letter by him
to Davy. It is not only interesting in view of Davy’s remark that “the
evidence of the use of a practical discovery is of most value when
furnished by practical men,” but also as showing the rapidity with
which the discovery was taken advantage of:--
“Walls End Colliery, Newcastle, _June 1st, 1816_.
“After having introduced your safety lamp into general use
in all the collieries under my direction, where inflammable
air prevails, and after using them daily in every variety of
explosive mixture, for upwards of three months, I feel the
highest possible gratification in stating to you that they have
answered to my entire satisfaction.
“The safety of the lamps is so easily proved by taking them
into any part of a mine charged with fire-damp, and all the
explosive gradations of that dangerous element are so easily and
satisfactorily ascertained by their application, as to strike the
minds of the most prejudiced with the strongest conviction of
their high utility; and our colliers have adopted them with the
greatest eagerness.
“Besides the facilities afforded by this invention to the
working of coal mines abounding in fire-damp, it has enabled
the directors and superintendents to ascertain, with the utmost
precision and expedition, both the presence, the quantity, and
the correct situation of the gas. Instead of creeping inch
by inch with a candle, as is usual, along the galleries of a
mine suspected to contain fire-damp, in order to ascertain
its presence, we walk firmly in with the safe lamps, and with
the utmost confidence prove the actual state of the mine. By
observing attentively the several appearances upon the flame of
the lamp, in an examination of this kind, the cause of accidents
which have happened to the most experienced and cautious miners
is completely developed; and this has been, in a great measure,
matter of mere conjecture.
“I feel peculiar satisfaction in dwelling upon a subject which
is of the utmost importance, not only to the great cause of
humanity, and to the mining interest of the country, but also
to the commercial and manufacturing interests of the United
Kingdom; for I am convinced that by the happy invention of the
safe lamp large proportions of the coal mines of the empire
will be rendered available, which otherwise might have remained
inaccessible, at least without an invention of similar utility,
which could not have been wrought without much loss of the
mineral, and risk of life and capital.
“It is not necessary that I should enlarge upon the national
advantages which must necessarily result from an invention
calculated to prolong our supply of mineral coal, because I think
them obvious to every reflecting mind; but I cannot conclude,
without expressing my highest sentiments of admiration for those
talents which have developed the properties, and controlled
the power, of one of the most dangerous elements which human
enterprise has hitherto had to encounter.”
This letter is only one of many received by Davy from practical men,
all telling the same story of wonder and astonishment “that so simple
a looking instrument should defy an enemy heretofore unconquerable”;
and all expressing the deepest gratitude to him as its inventor, often
in language which gains in force, and even in eloquence, from its very
homeliness and simple pathos.
The following address from the Whitehaven colliers was among the papers
lent to me by Dr. Rolleston:--
“_September 18, 1816._
“We, the undersigned, miners at the Whitehaven Collieries,
belonging to the Earl of Lonsdale, return our sincere thanks to
Sir Humphry Davy, for his invaluable discovery of the safe lamps,
which are to us life preservers; and being the only return in
our power to make, we most humbly offer this, our tribute of
gratitude.”
The names of eighty-two miners are appended--the majority of
them--viz. forty-seven--with their mark (+) affixed.
What the learned world thought may be judged from the following
extracts from an article in the _Edinburgh Review_--a periodical not
always characterised by a just appreciation of the work of the Royal
Institution professors, for the literature of science contains few
things more disingenuous or more spiteful than the attack of “the young
gentleman from Edinburgh”--afterwards known as Lord Brougham--on Thomas
Young when he first made known the undulatory theory of light. In the
_Review_ for February, 1816, Mr. Playfair begins his article on Davy’s
discovery by pointing out that--
“The safe lamp is a present from philosophy to the arts, and to
the class of men furthest removed from the influence of science.
The discovery is in no degree the effect of accident; and chance,
which comes in for so large a share in the credit of human
inventions, has no claims on one which is altogether the result
of patient and enlightened research....
“This is exactly such a case as we should choose to place before
Bacon, were he to revisit the earth, in order to give him, in a
small compass, an idea of the advancement which philosophy has
made, since the time when he had pointed out to her the route
which she ought to pursue. The great use of an immediate and
constant appeal to experiment cannot be better evinced than in
this example. The result is as wonderful as it is important. An
invisible and impalpable barrier made effectual against a force
the most violent and irresistible in its operations; and a power,
that in its tremendous effects seemed to emulate the lightning
and the earthquake, confined within a narrow space, and shut
up in a net of the most slender texture,--are facts which must
excite a degree of wonder and astonishment from which neither
ignorance nor wisdom can defend the beholder. When to this we
add the beneficial consequences and the saving of the lives of
men and consider that the effects are to remain as long as coal
continues to be dug from the bowels of the earth, it may fairly
be said that there is hardly in the whole compass of art or
science a single invention of which one would rather wish to be
the author.”
Davy was urged by several of his friends to protect his invention by a
patent. Among them was Mr. Buddle, who pointed out to him that he might
have received his five or ten thousand a year from it.
“My good friend,” was his answer, “I never thought of such a
thing: my sole object was to serve the cause of humanity; and
if I have succeeded, I am amply rewarded in the gratifying
reflection of having done so.... More wealth could not increase
either my fame or my happiness. It might undoubtedly enable me
to put four horses to my carriage; but what would it avail me to
have it said that Sir Humphry drives his carriage and four?”
The gratitude of some of the leading colliery proprietors for an
invention so unselfishly placed at their disposal found expression in
a letter from the chairman of a general meeting of the coal-owners
held at Newcastle on March 18th, 1816, conveying the terms of a vote
of thanks. A few months afterwards it was determined that their
appreciation should take a more substantial form, and a general meeting
of the coal-owners was held at Wallsend Colliery on August 31st, 1816,
at which it was resolved to make Davy a present of plate.
A note of opposition was at once sounded, and it came from one of the
proprietors of the Felling Colliery. Mr. W. Brandling urged that it was
not proved that Sir Humphry Davy was the first and true inventor of the
safety lamp, or even the discoverer of the principle on which it was
based.
“The conviction,” he said, “upon my mind is, that Mr. George
Stephenson, of Killingworth Colliery, is the person who first
discovered and applied the principle upon which safe lamps may
be constructed; for whether the hydrogen gas is admitted through
capillary tubes, or through the apertures of wire-gauze, which
may be considered as merely the orifices of capillary tubes, does
not, as I conceive, in the least affect the principle.”
The opposition thus started very quickly gathered strength, and by
appeals to local prejudice and to ignorance a degree of heat and
even animosity was imported into the question, which served no other
purpose than to confuse the true issue. At an adjourned meeting of the
coal-owners held on October 11th, 1816, Mr. William Brandling moved--
“That the meeting do adjourn, until by a comparison of dates it
shall be ascertained whether the merit of the safety lamp belongs
to Sir Humphry Davy, or to Mr. George Stephenson.”
Although Mr. Brandling failed to convince the meeting, it becomes
necessary in the interests of truth and justice to examine the grounds
upon which George Stephenson--a man of undoubted genius, and of an
integrity as blameless as that of Davy, and who, as the pioneer of
railway enterprise, subsequently acquired a fame as high and as
deserved as that of the great chemist--has claims to be regarded as an
inventor of the safety lamp. In equity, it must be admitted that the
question is not merely a question of dates, for in assigning merit in
a matter of this kind the calmer judgment of posterity is not wholly
swayed by priority of date; it looks to circumstances, conditions,
motives, and it apportions its meed of approbation accordingly. The
glory of Priestley as an independent discoverer of oxygen is in nowise
dimmed by the circumstance that Scheele is now known to have discovered
it before him. It cannot be truthfully asserted that Davy was not an
independent inventor of the safety lamp. What has to be determined is,
has George Stephenson any such claim?
Stephenson’s claim has been ably and temperately stated by Dr. Smiles
in his biography of George Stephenson, in “The Lives of the Engineers,”
but an unbiassed review of the evidence will convince most people that,
however certain it may be that the Killingworth engine-tenter was
an independent searcher after a method of protecting a flame, it is
equally certain that he was not the discoverer of the true principle on
which the safety lamp is constructed, and that the lamp associated with
his name, although it bears the impress of the crude ideas with which
he started, owes its real merit to the discoveries of Davy.
This controversy and the feeling it gave rise to greatly exasperated
Davy, and his anger is manifested in his letters at the time. The
action of the Brandlings he seemed to think was inspired by the most
unworthy motives. As to his rival, he says:--
“I never heard a word of George Stephenson and his lamps till
six weeks after my principle of security had been published; and
the general impression of the scientific men in London, which is
confirmed by what I heard at Newcastle, is, that Stephenson had
some loose idea floating in his mind, which he had unsuccessfully
attempted to put in practice till after my labours were made
known;--then, he made something like a safe lamp, except that it
is not _safe_, for the apertures below are four times, and those
above twenty times too large; but, even if Stephenson’s plans had
not been posterior to my principles, still there is no analogy
between his glass exploding machine, and my metallic tissue
permeable to light and air, and impermeable to flame.”
On the 25th of September, 1817, as Davy passed through Newcastle
on his return from Scotland, the coal-owners who had subscribed to
his testimonial invited him to a banquet and presented him with the
plate, which, in accordance with his wishes, took the form of a
dinner-service. “I wish,” he had said, “that even the plate from which
I eat should awaken my remembrance of their liberality, and put me in
mind of an event which marks one of the happiest periods of my life.”
The chairman--his friend Mr. Lambton, afterwards the Earl of Durham,
and who was with him under the care of Dr. Beddoes at Bristol--made
the presentation in an impressive and felicitous speech, and Davy
acknowledged it in terms worthy of himself and of the occasion. In a
subsequent speech, in response to the toast of his health, he dilated
upon the theme always uppermost in his mind, and to which he never
neglected the opportunity to give utterance, namely, the benefit of
abstract science to mankind. He had an admirable moral to which to
point, and it was driven home with all his wonted skill and power.
In what manner this plate, which was valued at about £2,500, was
subsequently made subservient to the interests of science will be seen
hereafter.
The friends of Stephenson were not wanting in the courage of their
convictions or in determination to give substantial proof of it. In the
following November they met and resolved that as in their opinion Mr.
G. Stephenson had been the first to discover the principle of safety
and to apply it, he was entitled to some reward. Whereupon Davy’s
friends again assembled in public meeting on November 26th, 1817,
and passed resolutions to the effect that in their opinion the merit
belonged to Sir Humphry Davy alone, and that Stephenson’s latest lamps
were evident imitations of those of Sir Humphry Davy; and they further
ordered that copies of their resolutions should appear in a number
of local, London, and Edinburgh papers, and be sent to the principal
owners and lessors of collieries upon the Tyne and Wear. Davy’s
friends in London also exerted themselves in his behalf, and a copy of
resolutions similar in purport to those passed in Newcastle, signed by
Sir Joseph Banks, P.R.S., Brande, Hatchett, and Wollaston, was sent to
the newspapers.
Mr. Brandling and his friends eventually collected about £800
(including 100 guineas which the meeting of October 11th had awarded
Stephenson as an acknowledgment of his efforts to construct a safe
lamp), and gave it, together with a silver tankard, to Mr. Stephenson
at a public dinner in January, 1818.
This is not the place to follow the subsequent history of the Davy
lamp, or to describe the various modifications which have grown out of
it, or even to show the dangers which a larger experience reveals as
latent in its original form. These dangers have in great measure arisen
from the development of the very system of ventilation which Buddle
himself instituted; and he who in his joy exultingly exclaimed, “At
last, we have subdued this monster!” has unwittingly contributed to the
maleficent activity of the monster in coping with the lamp as Buddle
knew it.
In the course of his numerous trials made to elucidate the principle
of the safety lamp, Davy observed certain peculiarities connected with
flame which led him to take up the general question. Hence arose a
series of investigations, which have contributed in no small degree to
our knowledge of a particularly difficult and intricate subject.
He proved, in the first place, that flame must be considered as an
_explosive mixture_ of inflammable gas or vapour and air, and that
the heat communicated by it must depend upon its mass. The different
appearance of a flame of coal gas burning in a jet in the open air, and
in his safety lamp mixed with common air, led him to investigate the
cause of luminosity in flame. He says:--
“In reflecting on the circumstances of the two species of
combustion I was led to imagine that the cause of the superiority
of the light of the _stream_ of coal gas might be owing to the
_decomposition_ of a part of the gas towards the interior of the
flame, where the air was in smallest quantity, and the deposition
of solid charcoal, which, first by its _ignition_, and afterwards
by its combustion, increased in a high degree the intensity of
the light.”
The principle of the increase of the brilliancy and density of flame
by the production and ignition of solid matter explains the appearance
of the different parts of the flames of burning bodies, and of the
blow-pipe flame; it also explains the intensity of the light of those
flames in which fixed solid matter is produced in combustion, _e.g._
phosphorus and zinc in oxygen, potassium in chlorine; and, on the
other hand, the feebleness of the light of flames in which gaseous
and volatile matter is alone produced, _e.g._ hydrogen in oxygen,
phosphorus in chlorine. Davy’s theory has not been unchallenged, but
all subsequent research, when pushed sufficiently far, has shown that,
as regards all ordinary illuminating flames, _i.e._ carbonaceous
flames--_e.g._ coal-gas, oil, paraffin, candle--the presence of solid
incandescent carbon is a prime cause of their luminosity. It had
been observed that the rarefaction of a mixture of inflammable gases
diminishes its combustibility: Davy proved that this diminution was
not the result of the removal of pressure _per se_, but of the cooling
effect thus indirectly produced. Hence, the lower the temperature of
ignition of a gaseous mixture the more it may be rarefied without
becoming uninflammable. In like manner he shows that by heating the
gaseous mixture it may be caused to explode at a lower temperature,
and that when gases combine by sudden compression, the combination is
caused by the heat evolved. Also that the power of an indifferent gas
to prevent the explosion of a gaseous mixture depends upon its power
of abstracting heat, and that the higher the temperature of ignition
of the explosive mixture the less is the amount of indifferent gas
required to stop the explosion. He proved that it was quite possible
to effect the gradual combination of gases without flame--that is,
without the production of heat sufficient to raise the products to
incandescence; and he discovered the singular fact that platinum would
induce the combination of many inflammable gases and vapours, and on
this circumstance based the construction of his flameless lamp.
* * * * *
In the early summer of 1818, he thus wrote to his mother:--
“MY DEAR MOTHER,--We are just going on a very interesting
journey. I am first to visit the coal miners of Flanders, who
have sent me a very kind letter of invitation and of thanks for
saving their lives. We are then going to Austria, where I shall
show Vienna to Lady Davy, and then visit the mines; and lastly,
before I return, we are going to visit Naples.
“I have the commands of his Royal Highness the Prince Regent to
make experiments upon some very interesting ancient manuscripts,
which I hope to unfold. I had yesterday the honour of an audience
from his Royal Highness, and he commissioned me to pursue this
object in the most gracious and kind manner....
“We shall be absent some months. With kindest love to my sisters
and my aunts,
“I am, my dear mother,
“Your most affectionate son,
“H. DAVY.”
A few months after this visit to the Prince Regent he received the
intimation that he had been created a baronet.
He arrived at Naples in the autumn, and began his researches on the
Herculaneum manuscripts referred to in his letter. His first results
were sufficiently encouraging to induce him to make some prolonged
experiments with a view of discovering a method of unfolding them.
He found that the papyri had suffered not so much from fire, as was
believed, as from a gradual change in vegetable structure, similar
to that which accompanies the transformation of vegetable matter
into lignite. He managed to unroll a number, and an account of his
results was communicated to the Royal Society in 1821. But from the
fragmentary character of the papyri these were found to be of little
value to literature. Subsequently difficulties were put in his way by
the curators of the museum, and ultimately his investigations were
abandoned, not without some little exhibition of temper and resentment
on his part.
During his stay at Naples he again interested himself in the volcanic
phenomena of Vesuvius, and his observations constitute the material
of a paper which was published in the _Philosophical Transactions_
in 1827, and many of his personal experiences in connection with the
subject are referred to in his last work, “Consolations in Travel.”
He left Naples in the spring of 1819, and after a short stay at the
baths of Lucca he went for the summer and early autumn into the Tyrol,
whence he again proceeded to Lucca, and on the approach of winter
returned to Naples, where he arrived on December 1st. He quitted it
in the spring of 1820, and travelled slowly home by the south of
France and Bordeaux, arriving in England about the middle of June. On
the 19th of that month Sir Joseph Banks died, and so terminated his
forty-two years’ presidency of the Royal Society, to which position he
was elected before Davy was even born. Davy immediately announced his
intention of becoming a candidate for the vacant chair, and was elected
at the following anniversary meeting on November 30th.