and if the posthumous fame of Davy be submitted to its measure, where is the philosopher in our times whose name will attain a higher eminence? Let our readers recal to their recollection the bitter animosity which France and England entertained towards each other in the year 1807, and they will form some idea of the astounding impression which the Bakerian Lecture must have produced on the philosophers of Paris, when, in despite of national prejudice and national vanity, it was crowned by the Institute of France with the prize of Napoleon. Thus did the Voltaic battery achieve what all the artillery of Britain could never have produceda spontaneous and willing homage to English superiority! But let not this observation be considered as intended to convey the slightest degree of disrespect, or to encourage any feeling to the disparagement of the French chemists; on the contrary, it is even a question not easily answered, to which party belongs the triumph-to him who won the laurel crown, or to those who so nobly placed it on his brow. They set an example to future ages which may as materially advance the progress of science, as the researches which called it forth; they proved, to adopt the language of the Edinburgh Review, that the commonwealth of science is of no party, and of no nation; that it is a pure republic, and always at peace. Its shades are disturbed neither by domestic malice nor by foreign levy; they resound not with the cries of factions or of public animosity. Falsehood is the only enemy their inhabitants denounce, Truth, and her minister, Reason, the only leaders they follow.

We proceed to consider the splendid discovery of the composition of the fixed alkalies, which was announced in Davy's second Bakerian Lecture, read before the Royal Society in 1807 and which was the direct result of an application of the laws of Voltaic decomposition, so admirably developed in his lecture of the preceding year. The memoir therefore affords a very happy instance of philosophical induction, the most brilliant results having been obtained through a chain of reasoning and experiment; and, with the exception, perhaps,

of Newton's account of his first discoveries in optics, the annals of science cannot boast of such another monument of transcendent genius. Had it been true, as was at the time insinuated with singular inconsistency, and equal unfairness, that the decomposition of the alkalies was accidentally effected by the high power of the apparatus placed at his disposal, Davy's claims to our admiration would have assumed a very different character: in such a case he might be said to have forced open the temple by direct violence, instead of having discovered and touched the secret spring by which its portals were unclosed.

The fixed alkalies, as well as the earths, had formerly been suspected to contain metallic bases; but as no proof, nor even experimental indication of the fact, could be obtained, the idea was by many entirely abandoned; and, with regard to the former of these bodies, the supposition of their being compounds of hydrogen was considered more plausible, inasmuch as they maintained a striking analogy in sensible qualities, as well as in chemical habitudes, to ammonia, whose composition had been fully established; while the supposed relations between hydrogen and oxygen, the acknowledged principle of acidity, added strength to the conjecture. Still, all the chemists in Europe had in vain attempted to effect their decomposition: they had been tortured by every variety of experiment which ingenuity could suggest or perseverance accomplish, but all in vain nor was the pursuit abandoned until indefatigable effort had wrecked the patience and exhausted every resource of the experimentalist. Such was the forlorn and disheartening position of the philosopher, when Davy proffered his assistance. He created new instruments, new powers, and fresh resources; and, interrogating Nature on a different plan, her long-cherished secret was revealed.

We have already explained the important fact, established by Davy, that during the developement of principles from their various combinations, by Voltaic action, an attraction invariably subsists between oxygen and the positive pole, and inflammable matter and the negative pole: thus, in the

decomposition of water, its oxygen was constantly transferred to the former, and its hydrogen to the latter. Furnished with such data, Davy proceeded to submit a fixed alkali to the most intense action of the Galvanic pile; believing that if it contained any hydrogen, or other inflammable basis, it would be separated at its negative extremity, and if any oxygen, that it would appear at the opposite end. His first attempts were made on solutions of the alkalies; but, notwithstanding the intensity of the electric action, the water alone was decomposed, oxygen and hydrogen being disengaged with violent effervescence, and transferred to their respective poles. The presence of water thus appearing to prevent the desired decomposition, potass, in a state of igneous fusion, was submitted to experiment; when it was immediately evident that combustible matter of some kind, burning with a vivid light, was given off at the negative wire. After various trials, during the progress of which the numerous difficulties which successively arose were as immediately combated by ingenious manipulation, a small piece of potass, sufficiently moistened by the breath to impart to it a conducting power, was placed on an insulated disc of platina, and connected with the negative side of the battery in a state of intense activity, and a platina wire communicating with the positive side, was at the same instant brought into contact with the upper surface of the alkali. What followed? What followed? A series of phænomena, in strict accordance with those laws which Davy had previously discovered. The potass began to fuse at both its points of electrization; a violent effervescence commenced at the upper or positive surface, while at the lower or negative, instead of any liberation of elastic matter, which must have happened had hydrogen been present, small globules having the appearance of quicksilver were disengaged, some of which were no sooner formed than they burnt with explosion and bright flame. What must have been the sensations of Davy at this moment! He had decomposed the alkali, and discovered it to contain a metallic basis. The gaseous matter developed at the positive pole, was soon identified as oxygen; but to collect

the metallic matter at the opposite extremity, in a sufficient quantity for a satisfactory examination, was not so easy; for such was its attraction for oxygen, that it speedily reverted to the state of alkali by re-combining with it. After various trials, Davy found that recently-distilled naphtha presented a medium in which it might be preserved, by covering the metal with a thin transparent film of fluid, which defended it from the action of the air, and at the same time allowed an accurate examination of its physical qualities. Thus provided, he proceeded to investigate the properties of the body; giving to it the name of potassium, and which may be described as follows. It is a white metal, instantly tarnishing by exposure to air; at the temperature of 70° Fahrenheit, it exists in small globules, which possess the metallic lustre, opacity, and general appearance of mercury; so that when a globule of mercury is placed near one of potassium, the eye cannot discover any difference between them. At this temperature, however, the metal is only imperfectly fluid; but when gradually heated, it becomes more and more fluid; and at 150°, its fluidity is so perfect, that several globules may easily be made to run into one. By reducing its temperature, it bemalleable solid, which has the lustre of polished silver; it is soft enough, indeed, to be moulded like wax. At about the freezing point of water, it becomes hard and brittle, and exhibits when broken a crystallized texture of perfect whiteness and high metallic splendour. It is also a perfect conductor of both electricity and heat. Thus far, then, it fulfils every condition of a metal; but we have now to mention a quality which has been as invariably associated with the idea of a metal as lustre; and its absence, therefore, in potassium, has given rise to a question whether, after all, it can with propriety be classed under this denomination;—we allude to great specific gravity. Instead of possessing that ponderosity which we should have expected in a body otherwise metallic, it is so light as to swim not only upon the surface of water, but upon that of naphtha, by far the lightest fluid in nature. Thrown upon water, it instantly

comes at 50° a soft and

decomposes the fluid, and an explosion is produced with a vehement flame; an experiment which is rendered more striking if, for water, ice be substituted. In this latter case it instantly burns with a bright flame, and a deep hole is made in the ice, filled with a fluid, which is found to be a solution of potass. It is scarcely necessary to state that this phænomenon depends upon the very powerful affinity which the metal possesses for oxygen, enabling it even to separate it from its most subtle combinations. The evidence afforded of the nature of the fixed alkali, potass, is thus rendered complete. It is a metallic oxide, or, in other words, a body composed of oxygen, and a metal of the most singular description, so light as to swim upon water, and so inflammable as to catch fire by contact with ice!

From these observations it will be immediately perceived, that the decomposition of the fixed alkali placed in the hands of the experimentalist a new instrument of analysis, scarcely less energetic or of less universal application than the power from which the discovery emanated. So strong is the affinity of potassium for oxygen, that it discovers and decomposes the small quantities of water contained in alcohol and ether. But, perhaps, the most beautiful illustration of its deoxidizing power, is shown in its action on fixed air, or Carbonic Acid; when heated in contact with that gas, it catches fire, and by uniting with its oxygen becomes potass, while the liberated carbon is deposited in the form of charcoal.

Upon submitting soda to the electric battery, under circumstances such as those we have already described, a bright metal was obtained similar in its general character to potassium, but possessing distinctive peculiarities which it is not necessary to detail to this substance Davy gave the name of sodium.

These important discoveries were followed up by an investigation into the nature of the earths; and the results were communicated in a paper, read before the Royal Society on the 30th of June in the same year. It appears that this investigation required still more refined and complicated processes than those which had succeeded with the fixed alkalies,