An Introduction to the History of Science1. Theology or Religion } Taught by Nature.
Ethics or Moral Virtues } by Revelation.
2. Geography.
3. My Profession-- 1. Botany. 2. Pharmacy. 3. Nosology. 4. Anatomy.
5. Surgery. 6. Chemistry.
4. Logic.
5. Language, etc.
A series of essays which Davy wrote in pursuing his scheme of self-culture proves how rapidly his mind drew away from the superst.i.tions which characterized the ma.s.ses of the people among whom he lived. He had as a boy been haunted by the fear of monsters and witches in which the credulous of all cla.s.ses then believed. His notebook shows that he was now subjecting to examination the religious and political opinions of his time. He composed essays on the immortality and immateriality of the soul, on governments, on the credulity of mortals, on the dependence of the thinking powers on the organization of the body, on the ultimate end of being, on happiness, and on moral obligation. He studied the writings of Locke, Hartley, Berkeley, Hume, Helvetius, Condorcet, and Reid, and knew something of German philosophy.
It was not till he was nineteen that Davy entered on the experimental study of chemistry.
Guided by the _Elements_ of Lavoisier, encouraged by the friendship of Gregory Watt (a son of James Watt) and by another gentleman of university education, stimulated by contact with the Cornish mining industry, Davy pursued this new study with zeal, and within a few months had written two essays full of daring generalizations on the physical sciences. These were published early in 1799. Partly on the basis of the ingenious experiment mentioned in the preceding chapter, he came to the conclusion that "Heat, or that power which prevents the actual contact of the corpuscles of bodies, and which is the cause of our peculiar sensations of heat and cold, may be defined as a peculiar motion, probably a vibration, of the corpuscles of bodies, tending to separate them." Other pa.s.sages might be quoted from these essays to show how the gifted youth of nineteen antic.i.p.ated the science of subsequent decades, but in the main these early efforts were characterized by the faults of overwrought speculation and incomplete verification. He soon regretted the premature publication of his studies. "When I consider," he wrote, "the variety of theories that may be formed on the slender foundation of one or two facts, I am convinced that it is the business of the true philosopher to avoid them altogether. It is more laborious to acc.u.mulate facts than to reason concerning them; but one good experiment is of more value than the ingenuity of a brain like Newton's."
In the mean time Davy had been chosen superintendent of the Pneumatic Inst.i.tution at Bristol by Dr. Beddoes, its founder. It was supported by the contributions of Thomas Wedgwood and other distinguished persons, and aimed at discovering by means of experiment the physiological effect of inhaling different gases, or "fact.i.tious airs," as they were called.
The founding of such an establishment has been termed a scientific aberration, but the use now made in medical practice of oxygen, nitrous oxide, chloroform, and other inhalations bears witness to the sanity of the sort of research there set on foot. Even before going to Bristol, Davy had inhaled small quant.i.ties of nitrous oxide mixed with air, in spite of the fact that this gas had been held by a medical man to be the "principle of contagion." He now carried on a series of tests, and finally undertook an extended experiment with the a.s.sistance of a doctor. In an air-tight or box-chamber he inhaled great quant.i.ties of the supposedly dangerous gas. After he had been in the box an hour and a quarter, he respired twenty quarts of pure nitrous oxide. He described the experience in the following words:--
"A thrilling, extending from the chest to the extremities, was almost immediately produced. I felt a sense of tangible extension highly pleasurable in every limb; my visible impressions were dazzling, and apparently magnified; I heard every sound in the room, and was perfectly aware of my situation. By degrees, as the pleasurable sensations increased, I lost all connection with external things; trains of vivid visible images rapidly pa.s.sed through my mind, and were connected with words in such a manner, as to produce perceptions perfectly novel. I existed in a world of newly connected and newly modified ideas: I theorized, I imagined that I made discoveries. When I was awakened from this semi-delirious trance by Dr. Kinglake, who took the bag from my mouth, indignation and pride were the first feelings produced by the sight of the persons about me. My emotions were enthusiastic and sublime, and for a minute I walked round the room perfectly regardless of what was said to me. As I recovered my former state of mind, I felt an inclination to communicate the discoveries I had made during the experiment. I endeavored to recall the ideas: they were feeble and indistinct; one collection of terms, however, presented itself; and with the most intense belief and prophetic manner, I exclaimed to Dr.
Kinglake, '_Nothing exists but thoughts! The universe is composed of impressions, ideas, pleasures and pains!_'"
Davy aroused the admiration and interest of every one who met him. A literary man to whom he was introduced shortly after his arrival in Bristol spoke of the intellectual character of the young man's face. His eye was piercing, and when he was not engaged in conversation, its expression indicated abstraction, as though his mind were pursuing some severe train of thought scarcely to be interrupted by external objects; "and," this writer adds, "his ingenuousness impressed me as much as his mental superiority." Mrs. Beddoes, a gay, witty, and elegant lady, and an ardent admirer of the youthful scientist, was a sister of Maria Edgeworth. The novelist's tolerance of Davy's enthusiasm soon pa.s.sed into a clear recognition of his commanding genius. Coleridge, Southey, and other congenial friends, whom the chemist met under Dr. Beddoes'
roof, shared in the general admiration of his mental and social qualities. Southey spoke of him as a miraculous young man, at whose talents he could only wonder. Coleridge, when asked how Davy compared with the cleverest men he had met on a visit to London, replied expressively: "Why, Davy can eat them all! There is an energy, an elasticity in his mind, which enables him to seize on and a.n.a.lyze all questions, pushing them to their legitimate consequences. Every subject in Davy's mind has the principle of vitality. Living thoughts spring up like turf under his feet." He thought that if Davy had not been the first chemist he would have been the first poet of the age. Their correspondence attests the intimate interchange of ideas and sentiments between these two men of genius, so different, yet with so much in common.
In 1801 Davy was appointed a.s.sistant lecturer in chemistry at the Royal Inst.i.tution (Albemarle Street, London), which had been founded from philanthropic motives by Count Rumford in 1799. Its aim was to promote the application of science to the common purposes of life. Its founder desired while benefiting the poor to enlist the sympathies of the fashionable world. Davy, with a zeal for the cause of humanity and a clear recognition of the value of a knowledge of chemistry in technical industries and other daily occupations, lent himself readily to the founder's plans. His success as a public expositor of science soon won him promotion to the professorship of chemistry in the new inst.i.tution, and through his influence an interest in scientific investigation became the vogue of London society. His popularity as a lecturer was so great that his best friends feared that the head of the brilliant provincial youth of twenty-two might be turned by the adulation of which he soon became the object. "I have read," writes his brother, "copies of verses addressed to him then, ... anonymous effusions, some of them displaying much poetical taste as well as fervor of writing, and all showing the influence which his appearance and manner had on the more susceptible of his audience."
His study of the tanning industry (1801-1802) and his lectures on agricultural chemistry (1803-1813) are indicative of the early purpose of the Royal Inst.i.tution and of Davy's lifelong inclination. The focus of his scientific interest, however, rested on the furtherance of the application of the electrical studies of Galvani and Volta in chemical a.n.a.lysis. In a letter to the chairman of managers of the Royal Inst.i.tution Volta had in 1800 described his voltaic pile made up of a succession of zinc and copper plates in pairs separated by a moist conductor, and before the end of the same year Nicholson and Carlisle had employed an electric current, produced by this newly devised apparatus, in the decomposition of water into its elements.
In the spring of the following year the _Philosophical Magazine_ states: "We have also to notice a course of lectures, just commenced at the inst.i.tution, on a new branch of philosophy--we mean Galvanic Phenomena.
On this interesting branch Mr. Davy (late of Bristol) gave the first lecture on the 25th of April. He began with the history of Galvanism, detailed the successive discoveries, and described the different methods of acc.u.mulating influence.... He showed the effects of galvanism on the legs of frogs, and exhibited some interesting experiments on the galvanic effects on the solutions of metals in acids." In a paper communicated to the Royal Society in 1806, _On Some Chemical Agencies of Electricity_, Davy put on record the result of years of experiment. For example, as stated by his biographer, he had connected a cup of gypsum with one of agate by means of asbestos, and filling each with purified water, had inserted the negative wire of the battery in the agate cup, and the positive wire in that of the sulphate of lime. In about four hours he had found a strong solution of lime in the agate cup, and sulphuric acid in the cup of gypsum. On his reversing the arrangement, and carrying on the process for a similar length of time, the sulphuric acid appeared in the agate cup, and the solution of lime on the opposite side. It was thus that he studied the transfer of certain of the const.i.tuent parts of bodies by the action of electricity. "It is very natural to suppose," says Davy, "that the repellent and attractive energies are communicated from one particle to another particle of the same kind, so as to establish a conducting _chain_ in the fluid. There may be a succession of decompositions and recompositions before the electrolysis is complete."
The publication of this paper in 1806 attracted much attention abroad, and gained for him--in spite of the fact that England and France were then at war--a medal awarded, under an arrangement inst.i.tuted by Napoleon a few years previously, for the best experimental work on the subject of electricity. "Some people," said Davy, "say I ought not to accept this prize; and there have been foolish paragraphs in the papers to that effect; but if the two countries or governments are at war, the men of science are not. That would, indeed, be a civil war of the worst description: we should rather, through the instrumentality of men of science, soften the asperities of national hostility."
In the following year Davy reported other chemical changes produced by electricity; he had succeeded in decomposing the fixed alkalis and discovering the elements pota.s.sium and sodium. To a.n.a.lyze a small piece of pure potash slightly moist from the atmosphere, he had placed it on an insulated platinum disk connected with the negative side of a voltaic battery. A platinum wire connected with the positive side was brought in contact with the upper surface of the alkali. "The potash began to fuse at both its points of electrization." At the lower (negative) surface small globules having a high metallic l.u.s.ter like quicksilver appeared, some of which burned with explosion and flame while others remained and became tarnished. When Davy saw these globules of a hitherto unknown metal, he danced about the laboratory in ecstasy and for some time was too much excited to continue his experiments.
After recovering from a very severe illness, owing in the judgment of some to overapplication to experimental science, and in his own judgment to a visit to Newgate Prison with the purpose of improving its sanitary condition, Davy made an investigation of the alkaline earths. He failed in his endeavor to obtain from these sources pure metals, but he gave names to barium, strontium, calcium, and magnesium, conjecturing that the alkaline earths were, like potash and soda, metallic oxides. In addition Davy antic.i.p.ated the isolation of silicon, aluminium, and zirconium. No doubt what gave special zest to his study of the alkalis was the hope of overthrowing the doctrine of French chemists that oxygen was the essential element of every acid. Lavoisier had given it, indeed, the name oxygen (acid-producer) on that supposition. Davy showed, however, that this element is a const.i.tuent of many alkalis.
In 1810 he advanced his controversy by explaining the nature of chlorine. Discovered long before by the indefatigable Scheele, it bore at the beginning of the nineteenth century the name oxymuriatic acid.
Davy proved that it contained neither oxygen nor muriatic (hydrochloric) acid (though, as we know, it forms, with hydrogen, muriatic acid). He gave the name _chlorine_ because of the color of the gas (??????, pale green). Davy studied later the compounds of fluorine, and though unable to isolate the element, conjectured its likeness to chlorine.
He lectured before the Dublin Society in 1810, and again in the following year; on the occasion of his second visit receiving the degree of LL.D. from Trinity College. He was knighted in the spring of 1812, and was married to a handsome, intellectual, and wealthy lady. He was appointed Honorary Professor of Chemistry at the Royal Inst.i.tution. His new independence gave him full liberty to pursue his scientific interests. Toward the close of 1812 he writes to Lady Davy:--
"Yesterday I began some new experiments to which a very interesting discovery and a slight accident put an end. I made use of a compound more powerful than gunpowder destined perhaps at some time to change the nature of war and influence the state of society. An explosion took place which has done me no other harm than that of preventing me from working this day and the effects of which will be gone to-morrow and which I should not mention at all, except that you may hear some foolish exaggerated account of it, for it really is not worth mentioning...."
The compound on the investigation of which he was then engaged is now known as the trichloride of nitrogen.
In the autumn of 1813 Sir Humphry and Lady Davy, accompanied by Michael Faraday, who on Davy's recommendation had in the spring of the same year received a post at the Royal Inst.i.tution, set out, in spite of the continuance of the war, on a Continental tour. At Paris Sir Humphry was welcomed by the French scientists with every mark of distinction. A substance which had been found in the ashes of seaweed two years previously, by a soap-boiler and manufacturer of saltpeter, was submitted to Davy for chemical examination. Until Davy's arrival in Paris little had been done to determine its real character. On December 6 Gay-Lussac presented a brief report on the new substance, which he named _iode_ and considered a.n.a.logous to chlorine. Davy, working with almost incredible rapidity in the presence of his rivals, was able a week later to sketch the chief characters of this new element, now known by the name he chose for it--_iodine_.
We have pa.s.sed over his investigation of boracic acid, ammonium nitrate, and other compounds; we can merely mention in pa.s.sing his later studies of the diamond and other forms of carbon, of the chemical const.i.tuents of the pigments used by the ancients, his investigation of the torpedo fish, and his antic.i.p.ation of the arc light.
It seems fitting that Sir Humphry Davy should be popularly remembered for his invention of the miner's safety-lamp. At the beginning of the nineteenth century the development of the iron industry, the increasing use of the steam engine and of machinery in general led to great activity and enterprise in the working of the coal mines. Colliery explosions of fire-damp (marsh gas) became alarmingly frequent, especially in the north of England. The mine-owners in some cases sought to suppress the news of fatalities. A society, however, was formed to protect the miners from injury through gas explosions, and Davy was asked for advice. On his return from the Continent in 1815 he applied himself energetically to the matter. He visited the mines and a.n.a.lyzed the gas. He found that fire-damp explodes only at high temperature, and that the flame of this explosive mixture will not pa.s.s through small apertures. A miner's lamp was therefore constructed with wire gauze about the flame to admit air for combustion. The fire-damp entering the gauze burned quietly inside, but could not carry a high enough temperature through the gauze to explode the large quant.i.ty outside. To one of the members of the philanthropic society which had appealed to him Davy wrote: "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."
Davy was elected President of the Royal Society in 1820, and retained that dignity till he felt compelled by ill health to relinquish it in 1827. "It was his wish," says his brother, "to have seen the Royal Society an efficient establishment for all the great practical purposes of science, similar to the college contemplated by Lord Bacon, and sketched in his _New Atlantis_; having subordinate to it the Royal Observatory at Greenwich for astronomy; the British Museum, for natural history, in its most extensive acceptation."
Sir Humphry Davy, after a life crowded with splendid achievements, died at Geneva in 1829 with many of his n.o.blest dreams unfulfilled.
Fortunately in Michael Faraday, who is sometimes referred to as the greatest of his discoveries, he had a successor who was fully adequate to the task of furthering the various investigations that his genius had set on foot, and who, to the majority of men of mature mind, is no less personally interesting than the Cornish scientist, poet, and philosopher.
REFERENCES
John Davy, _Works of Sir Humphry Davy_.
John Davy, _Fragmentary Remains, literary and scientific, of Sir Humphry Davy, Bart._
Bence Jones, _Life and Letters of Faraday_.
John Tyndall, _Faraday as a Discoverer_.
E. v. Meyer, _History of Chemistry_.
S. P. Thompson, _Michael Faraday; his Life and Work_.
Sir Edward Thorpe, _Humphry Davy, Poet and Philosopher_.
CHAPTER XIV
SCIENTIFIC PREDICTION--THE DISCOVERY OF NEPTUNE
Under this heading we have to consider a single ill.u.s.tration--the prediction, and the discovery, in 1846, of the planet Neptune. This event roused great enthusiasm among scientists as well as in the popular mind, afforded proof of the reliability of the Newtonian hypothesis, and demonstrated the precision to which the calculation of celestial motions had attained. Scientific law appeared not merely as a formulation and explanation of observed phenomena but as a means for the discovery of new truths. "Would it not be admirable," wrote Valz to Arago in 1835, "to arrive thus at a knowledge of the existence of a body which cannot be perceived?"
The prediction and discovery of Neptune, to which many minds contributed, and which has been described with a show of justice as a movement of the times, arose from the previous discovery of the planet Ura.n.u.s by Sir William Herschel in 1781. After that event Bode suggested that it was possible other astronomers had observed Ura.n.u.s before, without recognizing it as a planet. By a study of the star catalogues this conjecture was soon verified. It was found that Flamsteed had made, in 1690, the first observation of the heavenly body now called Ura.n.u.s.
Ultimately it was shown that there were at least seventeen similar observations prior to 1781.
It might naturally be supposed that these so-called ancient observations would lead to a ready determination of the planet's...o...b..t, ma.s.s, mean distance, longitude with reference to the sun, etc. The contrary, however, seemed to be the case. When Alexis Bouvard, the a.s.sociate of Laplace, prepared in 1821 tables of Ura.n.u.s, Jupiter, and Saturn on the principles of the _Mecanique Celeste_, he was unable to fix an orbit for Ura.n.u.s which would harmonize with the data of ancient and modern observations, that is, those antecedent and subsequent to Herschel's discovery in 1781. If he computed an orbit from the two sets of data combined, the requirements of the earlier observations were fairly well met, but the later observations were not represented with sufficient precision. If on the other hand only the modern data were taken into account, tables could be constructed meeting all the observations subsequent to 1781, but failing to satisfy those prior to that date. A consistent result could be obtained only by sacrificing the modern or the ancient observations. "I have thought it preferable," says Bouvard, "to abide by the second [alternative], as being that which combines the greater number of probabilities in favor of the truth, and I leave it to the future to make known whether the difficulty of reconciling the two systems result from the inaccuracy of ancient observations, or whether it depend upon some extraneous and unknown influence, which has acted on the planet." It was not till three years after the death of Alexis Bouvard that the extraneous influence, of which he thus gave in 1821 some indication, became fully known.
Almost immediately, however, after the publication of the tables, fresh discrepancies arose between computation and observation. At the first meeting of the British a.s.sociation in 1832 Professor Airy in a paper on the _Progress of Astronomy_ showed that observational data in reference to the planet Ura.n.u.s diverged widely from the tables of 1821. In 1833 through his influence the "reduction of all the planetary observations made at Greenwich from 1750" was undertaken. Airy became Astronomer Royal in 1835, and continued to take special interest in Ura.n.u.s, laying particular emphasis on the fact that the radius vector a.s.signed in the tables to this planet was much too small.
In 1834 the Reverend T. J. Hussey, an amateur astronomer, had written to Airy in reference to the irregularities in the orbit of Ura.n.u.s: "The apparently inexplicable discrepancies between the ancient and modern observations suggested to me the possibility of some disturbing body beyond Ura.n.u.s, not taken into account because unknown.... Subsequently, in conversation with Bouvard, I inquired if the above might not be the case." Bouvard answered that the idea had occurred to him; indeed, he had had some correspondence in reference to it in 1829 with Hansen, an authority on planetary perturbations.
In the following year Nicolai (as well as Valz) was interested in the problem of an ultra-Uranian planet in connection with the orbit of Halley's comet (itself the subject of a striking scientific prediction fulfilled in 1758), now reappearing, and under the disturbing influence of Jupiter. In fact, the probability of the approaching discovery of a new planet soon found expression in popular treatises on astronomy. Mrs.
Somerville in her book on _The Connection of the Physical Sciences_ (1836) said that the discrepancies in the records of Ura.n.u.s might reveal the existence and even "the ma.s.s and orbit of a body placed for ever beyond the sphere of vision." Similarly Madler in his _Popular Astronomy_ (1841) took the view that Ura.n.u.s might have been predicted by study of the perturbations it produced in the orbit of Saturn. Applying this conclusion to a body beyond Ura.n.u.s we, he continued, "may, indeed, express the hope that a.n.a.lysis will one day or other solemnize this, her highest, triumph, making discoveries with the mind's eye in regions where, in our actual state, we are unable to penetrate."
One should not pa.s.s over in this account the labors of Eugene Bouvard, the nephew of Alexis, who continued to note anomalies in the orbit of Ura.n.u.s and to construct new planetary tables till the very eve of the discovery of Neptune. In 1837 he wrote to Airy that the differences between the observations of Ura.n.u.s and the calculation were large and were becoming continually larger: "Is that owing to a perturbation brought about in this planet by some body situated beyond it? I don't know, but that's my uncle's opinion."