ANNALS

OF

PHILOSOPHY.

JULY, 1824.

ARTICLE I.

Biographical Account of Assessor John Gottlieb Gahn.

AMONG the many illustrious names which have adorned the annals of chemistry during the last fifty years, there are few entitled to a more distinguished place than that of Gahn. Born in the most favoured district of a country which was in the fullest enjoyment of its freedom,-the pupil of Bergmann, and the friend of Scheele, he is alike distinguished as a patriotic citizen, and as a profound philosopher. Identified with the fame of these two celebrated men will Gahn's descend to posterity, for it was in their publications that his greatest discoveries made their first appearance; and in the hearts of all his countrymen will his memory live embalmed, by the recollection of his general philanthropy and public virtue. Nor was he less amiable in private life; but, with the generosity of a liberal mind, he freely and frankly communicated on all occasions the boundless store of information which he had acquired, or the practical application of the discoveries which he had made. By his improvements in the arts of mining and metallurgy, he increased the wealth, not less than the glory of his country; and at this day, there is no name more admired, and at the same time more beloved, in Sweden, than that of John Gottlieb Gahn.

On the 17th of August, 1745, at the Woxna Iron Works, in South Helsingland, was born J. G. Gahn, son of Hanns Jacob Gahn, Treasurer to the Government of Stora Kopporberg. In his 15th year he had completed his preparatory education at the Gymnasium of Westeras, and early in the year 1760, he commenced his scientific studies in the University of Upsala. His mind seems already, even at this period, to have received the bias towards those pursuits which continued the study of his manhood and of his age, and which will long preserve his memory from decay. The wide fields of mineralogy and chemistry, of mathematics and mechanical philosophy, here New Series, VOL. VIII. B

engaged his young and eager spirit. He was one whose ardour, while it bore him rapidly forward, did not permit him carelessly to pass over any thing; and that vivacity of disposition which directed his attention to so many and various objects in rapid succession, was but a guide to him, though it must have bewildered others. He was one of the few who can run and read, and turn to account, accidents, and even blunders, of the most fortuitous description.

Thus it happened to him, while yet a pupil in the Academy, that a specimen of crystallized carbonate of lime dropped from his fingers. It was of the variety which mineralogists term dog'stooth spar, and the fall shattered it into fragments. While gathering these up, Gahn's attention was arrested by the appearance which one of them presented, and in which a portion of the original nucleus had been developed by the accident. This hint, which another might have neglected or misunderstood, he immediately followed up; nor did he rest satisfied until he had extracted by cleavage the rhomboid which constitutes the primitive. form of this mineral, from a great variety of its secondary crystals. Bergmann, to whom this observation and discovery were communicated, published, immediately afterwards, a Dissertation on the Forms of Crystals, which called forth the well-merited admiration of men of science. But while Bergmann reaped this honour from his Essay, he had omitted to mention, that it was the discoveries of the pupil, which had furnished the basis of all the reasonings of the master.

The next important service which the subject of this memoir rendered to science, was the investigation of the nature of the earth of bones. In this discovery accident had no share; yet it too yielded the first-fruits of reputation to another than the true owner. It is indeed to be regretted that in too many instances, Gahn suffered others to claim and to enjoy the reputation of improvements which they had never made, and of merit which they had never earned. In this he was so negligent during his life, that, it is to be feared, many of his discoveries are at this moment ascribed to others, and can now never be vindicated for their real author. For this strange indifference to fame, permitting others to reap where they had never sown, it is not easy to account; though we have an instance of something similar in the conduct of another celebrated chemist, Dr. Black, who, after finding the tract, and clearing the way, to a most fascinating field of discovery, contented himself with sitting down at the barrier which his genius had overthrown, while others passed by, and gathered an easy harvest of reputation. Previously to this period, the earth of bones had been universally considered to be sui generis and peculiar. Gahn, however, succeeded in analyzing it, and in establishing it to be a neutral salt, composed of phosphoric acid and lime. This is a disco

very, the value and difficulty of which, none but chemists thoroughly acquainted with the practical department of their science can appreciate. It reflects, however, no little honour on the sagacity of its author; and it has happened, at a period long subsequent to the time when the composition of this earth, as appearing in the animal kingdom, had become familiar to chemists, that the same substance, occurring in the mineral kingdom, has been again and again mistaken for a new and simple earth, by analysts of considerable celebrity.

Just about this time, Scheele had completed his investigation of fluor spar and its acid, and at the conclusion of the treatise which he published on this subject, he informed his readers, that "in addition to the discovery of a new earth, it was also in his power to announce to them that the earth of bones, instead of being an uncompounded substance, is phosphate of lime." The general and ambiguous nature of this allusion to the disco very of Gahn, although wholly unpremeditated on the part of Scheele, was the cause of the credit of it being immediately attributed to him; especially as Gahn had not then so far completed his experiments as to consider them deserving of being laid before the public in a separate memoir. Nor did such a production of his ever after appear; for it was one of the characteristics of his comprehensive genius, that he was ever reluctant to commit any of his opinions or discoveries in a crude state to the press, and where others imagined that little material remained to be investigated, he saw further, and still experienced a painful sense of imperfection.

Gahn next succeeded in demonstrating the metallic nature of manganese, which he effected by exposing its oxide along with charcoal powder to an intense heat. This discovery, however, with many others of inferior moment respecting the more recently known metals, was never published by himself, but appeared originally in the chemical dissertations of Bergmann. Nor is there any one trait in the whole character of our chemist more remarkable than that to which we have already alluded, his indifference to celebrity. He rarely, even in private, narrated in an unreserved manner the progress of any of his discoveries, and the person to whom such a communication was made might regard it as the strongest evidence of his full and confiding friendship. The feeling of how much remained to be done, appearing full before his penetrating eye, seems to have overpowered too much the satisfaction and complacency which ought to have resulted from what had been accomplished. And so forcibly did this sense of imperfection oppress him, that a morbid delicacy has in too many instances deprived the world of the results of his unwearied research during the long period of fifty years. In all this time, scarcely any publication of his appeared until he had almost literally obeyed the injunction of

the poet, in revolving it again and again in his mind, year after year. Yet advantageous as the severe rule of "nonum prematur in annum" may be to poets and their productions, it is by no means applicable to philosophers and their discoveries; and if the friends of Gahn had but been more generous in acknowledging whence they drew their own information, we must have been more heartily grateful to them for communicating it to others, and thereby, not unfrequently, securing a benefit which might else have perished.

Besides those discoveries which resulted from the investigations of Gahn, he conferred a favour of yet greater practical importance on science, in the improvements which he made as the means of prosecuting research. During his youth, the blowpipe was little used by men of science, and its advantages were less understood. That instrument, by which they are now enabled to make microscopic analyses in the dry way, with a degree of precision then wholly unexpected, was in its rude state at that period, more used by the mechanic than by the chemist. Cronstedt and Engerstrom first discovered its importance in distinguishing minerals by their various degrees of fusibility, and their several habitudes with fluxes. Next, Bergmann, by his excellent Dissertation de Tubo Ferruminatorio, extended the knowledge of the instrument more widely, and explained its uses more fully to the learned world. Gahn had been employed by this philosopher to make the greater part of the experiments detailed in the Dissertation, and, from that period, the improvement of every thing connected with the nature or management of the blowpipe, became one of his most favourite occupations. He enlarged, and at the same time defined, the uses of the several reagents; he added some new ones of great importance to their number; he invented or improved the various apparatus accompanying the instrument; and by his almost intuitive sagacity in detecting the characteristics both of simple bodies and of compound minerals, he was enabled to point out at once the plainest and most efficacious means by which they may be discovered and discriminated. A concise summary of directions for using the instrument was drawn up by him, and published in the second volume of Berzelius's Elements of Chemistry.

Another important facility contributed by Gahn to the prosecution of research, deserves to be classed with that just mentioned, and is, perhaps, scarcely inferior to it in value. This was the invention of a balance, not more remarkable for its extreme delicacy, than for the simplicity of its construction. The latter quality it possesses in so remarkable a degree, that it may be easily constructed by any workman of even very moderate qualifications; and thus this elegant and indispensable instrument was placed generally within the reach of all. A very copious description of it was written out by the inventor, a few

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months before his death, and was inser in the same work of Berzelius to whi Such are a few of the discoveries although these may, perhaps, be th his name abroad, they do not form the best known at home. To have a just idea be informed, that the sciences, however much fond pursuit, were not at any time his principal oc merely formed an agreeable relaxation, in which he oc indulged, when he could spare a few moments from his serious avocations. Let us now trace the course of his life a man of the world, and as a man of business, and glance at the public duties he had to discharge as a member of the representative body of Burghers in Sweden, and we shall then feel how surprising is his eminence as a man of science.

On the death of his father, he was left a young man, in narrow circumstances, which compelled him to direct his immediate and almost exclusive attention to the practice of mining and metallurgy. His mode of mastering his profession was characteristic of the man. He was not satisfied, like many others, with a mere theoretic knowledge of its processes, but determined to acquire a thorough acquaintance with them by personal experience. He, therefore, associated with the ordinary miners, dwelt with them, and accommodated himself to their habits, and took an active share in all their labours; nor did he relinquish this mode of life, until it ceased to make additions either to his knowledge, or to his experience.

In the year 1770, he defended at Upsala an academic thesis, entitled "Remarks on Regulations for an improved System of Management in Iron Founderies; " and in the course of the same year, he acquitted himself in the customary examinations respecting his metallurgic knowledge, with an ability which received the unqualified admiration of the judges. A few months after this, he was commissioned by the College of Mines to institute a course of experiments with a view to improve the method of melting copper at Fahlun. The consequence of this investigation was a complete regeneration of the whole system, so as to gain much time and save much expense by the change. Till this period, the old reverberatory furnace was everywhere in use, in which a large proportion of the fuel consumed was altogether wasted. Gahn recommended a new construction, by which this superfluous expenditure is avoided. It was immediately adopted, and continues at this day to be universally employed.

From the intimate acquaintance which he possessed with every subject connected with mining or with metallurgy, it may be imagined that Gahn now felt a strong desire to have the direction of a smelting work of his own. This, however, required a capital which he had not at command; but his reputa