terrestrial tortoises. The order of batrachians has but one fossi species: the gigantic salamander of Eningen, or the pretended fossil man-the homo diluvii testis of Scheuchzer. The order of reptiles which presents the most extraordinary fossil species is that of the saurians. In the first place, most of them were gigantic. A first species, the great saurian of Manheim-the lacerta gigantea of Sommering, the geosaurus of M. Cuvier-was twelve or thirteen feet in length; a second, the mosasaurus, the great saurian of the quarries of Maestricht, long taken for a crocodile, was more than twenty-four; and a third, truly gigantic, the megalosaurus, was more than seventy. Here, then, we have a lizard which surpassed the largest crocodiles, and in size even approached the whale. This, it is known, was discovered by Dr. Buckland, in the oolitic beds of Stonesfield, near Oxford. M. Cuvier further makes known some remains of the fossil monitors of Thuringia, of a great saurian at Honfleur, of a gigantic saurian in the quarries of Caen, &c.

The genus of pterodactyls, or flying lizards, though not remarkable for its size, is eminently so for its singular structure: a very short tail, a neck very long, a bird's beak, a finger of the anterior extremity prodigiously elongated, and thus elongated to support a sort of wing. There are two species of pterodactyls: one of the size of a bat, the other rather larger. It is needless to add that the genus is wholly extinct. But something still more strange in point of structure, is that presented by two other genera of saurians, both likewise extinct: the ichthyosaurus and plesiosaurus; the former uniting at once the snout of a dol phin, the teeth of a crocodile, the head and sternum of a lizard, paws of the cetacea, but to the number of four, and the vertebræ of a fish; the latter joining to these paws the head of a lizard, and a neck of such inordinate length that more than thirty vertebræ are counted therein. Both these extraordinary animals were found for the first time in England, but have since been discovered in Germany and France. The discovery of the first of these genera was due to Sir Everard Home; that of the last to Mr. Conybeare. Already four species of the ichthyosaurus are known, and five of the plesiosaurus.

These reptiles, so numerous and so varied, crocodiles, tortoises, the vast salamander, the strange or gigantic saurians, joined with crustacea, mollusks, zoophytes, fishes, marine mammals formed the first animal colonists which occupied the globe; the second were those of the epoch of the palæotherium ; the third, those of the epoch of the mastodon; the fourth are those of the actual epoch. Without counting the last, there have been three distinct eras of animal life that of the reptiles, that of the palæotheriums, that of the mastodons; and after each successive family of living beings, the sea has returned to repossess itself of the land, retreating afterwards in favor of a new order of creatures; for marine strata constantly succeed to the terrestrial strata, and animals which have lived in the sea constantly succeed to animals which have lived on dry land. Such is the assemblage of fossil species, reconstructed by M. Cuvier. We have seen the precise laws on which this reconstruction is founded. The highest of these laws is the principle of the correlation of forms; a principle by means of which we are enabled, to a certain point, to determine from each part all the others; for each part has a necessary relation to all the others, and all to each. Thus, and to cite again a new example of this great law of organic correlations, the form of the teeth, and even, in certain cases, the form of a single tooth, gives that of the condyle of the jaw; the form of this condyle gives that of the glenoid cavity which receives it; this condyle, this cavity, give the zygomatic arch, the temporal foss, in which the muscles are attached which move the jaw. The form of all these parts, that is to say, the mode of manducation, gives the stomach, the intestines, that is to say, the mode of digestion; this again gives the mode of prehension, or the form of the feet; for if the animal is herbivorous, it has no need of the feet except to support its body, it will suffice for it to have hoofs; and if it is carnivorous, it will necessarily require, on the contrary, divided feet, that is to say digits for seizing its prey and tearing it.

By proceeding thus from one part to another, we apprehend the relations which bind each of them, first to that which follows, and then nearer and nearer to all the others, even to the most remote, without the chain of relations being ever at any part broken or detached. From each part, and even in appearance the most insignificant part, we may therefore infer all the others, and the entire animal itself.

For example: that claw of the pangolin, found in the Palatinate, huge as it is, demonstrates of itself a lost species; and from this claw alone we might infer, as M. Cuvier well says, all the revolutions of the globe. In effect, this claw necessarily gives us a toe, and this toe a limb, and this limb a trunk, and this trunk a cranium, a head, proportionate all with one another; that is to say a gigantic pangolin, consequently a lost species, consequently revolutions, subversions experienced by the earth, and which have destroyed that species. But I confine myself here to recalling those great laws on which I have dwelt at more length elsewhere, and which astonish us less, perhaps, by their extent than by the amount of evidence which they carry with them.

MEMOIR OF OERSTED.

BY C. M. ÉLIE DE BEAUMONT,* PERPETUAL SECRETARY OF THE FRENCH ACADEMY OF

SCIENCES.

[Translated for the Smithsonian Institution by C. A. Alexander.]

Science, like nature, is one; the frontiers of states, the limits of populations, arrest not its propagation. In all civilized countries men calculate with the same figures, measure with the same instruments, avail themselves of the same classifications. Scientific bodies animated by a common spirit collect, by analogous means, the results of the general labor; and all these associations, to give a higher sanction to their mutual collaboration, have desired that the most eminent and celebrated of the savants of foreign countries should constitute a part of their official list.

Among the illustrious persons on whom the Academy has successively conferred the title, so justly coveted, of one of its eight foreign associates, few have better justified the distinction than he to whom we owe the knowledge that the mariner's compass and the lightning conductor present only different effects of identically the same physical agent.

Jean-Christian Oerstedt was born August 14, 1777, at Rudkjöbing, in the island of Langeland, one of the smallest of the archipelago of Denmark. His father exercised the profession of apothecary, and, although the town of Rudkjöbing then counted less than 1,000 inhabitants, he had full occupation. For fear that the young Christian should not be properly looked after in the paternal dwelling, he was sent every day to the house of a wig-maker, whose wife enjoyed the confidence of his parents. A brother, one year younger, who became in after life the celebrated jurisconsult André Sandöe Oersted, acccompanied him thither the following year. The wig-maker and his wife formed a warm attachment for the two brothers. The wife taught them to read; the husband instructed them in German, which was his mother tongue. The pupils made rapid progress, owing, perhaps, in reality more to a happy natural aptitude than to any talent in the teachers, but which sufficed to induce many other families to send their own children likewise to this improvised school where knowledge was imparted so quickly and so well. The wig-maker, transformed into schoolmaster, daily read to his pupils some pages of a German Bible, which was thus perused from beginning to end, and afterwards, in great part, read over anew. It was the daily task of the young Christian to translate word by word into Danish what had been read in German, and this exercise so far profited him that at the age of seven years he often embarrassed by his citations those who sought to put his 'sagacity to the test; whence the gossips of the vicinage used to say of him, This child will not live; he has too much smartness !

* Read at the annual public sitting of the Academy, December 29, 1862.

I write the name of Oersted as it has always been written in the publications of the Academy. In this the German orthography has been followed, while it would perhaps have been preferable to conform to the Danish orthography, in which the name is written Orsted, or without the majuscule Örsted. In Denmark it is pronounced Eursted, which is also the German pronunciation of the word Oersted, whence we are wrong in habitually pronouncing it as if it were written Ersted.

The wig-maker further taught him addition and subtraction; it was all he himself knew of arithmetic; but with a slight help from others, and a book found at his father's, the child was not slow in learning the rest as far as the rule of three, inclusive; no equivocal proof of unusual precocity of intellect. An extraordinary memory was early remarked in him, and was retained till death, equally with all the other happy endowments which he had received from nature.

When Christian had reached the age of 12, he and his brother, who was then 11, entered as apprentices the pharmacy of their father, whereby their secret wishes were at first contravened, for both had conceived the project of devoting themselves to the study of theology. The elder of the two, however, soon began to acquire a taste for pharmaceutical operations, and labored zealously in the paternal laboratory, reading at the same time all the books of chemistry and natural history which fell into his hands. Thus early was developed the inclination which led him to the study of nature. A student in theology daily devoted some hours to the instruction of the brothers in Greek and Latin. The elder applied himself moreover to the acquisition of the French, the younger to that of the English language. From this period the former evinced a decided taste for poetry, a taste which adhered to him all his life. He translated about this time several odes of Horace and a part of the Henriade into Danish.

These rather precarious means of instruction still bore happy fruits. In the spring of the year 1794, the brothers, aged respectively 17 and 16, were qualified to proceed to Copenhagen, where, after but a few months' preparation by a skillful master, who perfected them in the study of the ancient languages, they sustained with much honor an examination at their exit from the academy. Some two years afterwards Christian, who had in the mean time earned testimonials of distinction on all hands, bore off an academic prize for his reply to a question "On the shades to be observed in the choice of expressions, according as one writes in prose or in verse." Finally, during the autumn of 1799, he obtained the degree of doctor of philosophy upon the presentation of a thesis in metaphysics, (de forma metaphysices elementaris naturæ externæ.)

In the year last named, and those immediately following, he published divers short dissertations and critical analyses, which were generally inserted in the periodical collections. He thus evinced in turn the tendency of his mind to literature, to poetry, and to philosophy. These formed, indeed, only an accessory occupation; but, apart from his natural predisposition, favorable circumstances rendered these momentary efforts of singular advantage in the development of his faculties. His brother, with whom he always lived in the most cordial intimacy, had chiefly devoted himself to the study of philosophy, and the habit, which was maintained during life, of a daily interchange of ideas, led our physicist to a profitable participation in the same pursuit. Having become familiar with the writings of Kant, Fichte, Schelling, he caught sight of a great general law of unity in the physical world, which continued always to be one of the habitual subjects of his meditation. Struck at the same time with the beauty of natural laws, he became sensible of something profoundly poetic in nature, on which his innate taste for poetry seized with avidity.

His first essays, which had fixed the attention of the citizens of Copenhagen, placed him on terms of friendly intimacy with most of his young cotemporaries who were rising into distinction, particularly with Oelenschläger, who, as a poet, achieved some years afterwards so brilliant and well-merited a reputation. This attractive intercourse impelled him to the study of belles-lettres. To no important production of Danish or German literature, or of the elder French literature, was he a stranger. His admirable memory was garnished with the choicest passages, which, even at an advanced age, he was wont to cite with singular appositeness. Nor did he fail sometimes to exercise his own poetic powers, and, in the eyes of persons competent to judge of Danish verse, an Ode to the French, which he composed about this time, appeared to give indications of genuine talent. A

happy concurrence of circumstances brought Oersted also into intercourse with Steffens, and the two brothers Mynster, with whom he long continued to maintain philosophical and even theological discussions, which, whatever their vivacity, were never permitted to interfere with the claims of a reciprocal friendship.

The rectitude of his judgment always prevented these accessory exercises of thought from impairing the progress of his scientific studies; but they did not a little contribute to draw general attention to him; a kindly attention which greatly facilitated the development of his subsequent career.

Of that career positive science, was always the basis, and his success was rapid. At his examination in pharmacy, May 20, 1797, he astonished his judges by the extent of his knowledge, and one of them, on goiug away, having met with Professor Manthey, proprietor of the pharmacy in which Oersted had labored, addressed him in these words: "What a candidate is this you have sent us; he knows more than all of us together!" The following year Oersted obtained a new prize from the Academy; this time on a question of medicine. In 1800 Professor Manthey, being about to travel abroad, devolved on him the direction of his pharmacy, and nominated him to supply his place, during absence, in the lecture-room of the Academy of Surgery. The same year Oersted was received as adjunct of the faculty of medicine.

At this epoch he occupied himself very actively with chemistry. The researches of Wintrel on the simple galvanic chain had already led to the conception of an electro-chemical theory, and Ritter had inferred, from the ordinary chemical and electrical facts, the identity of the forces whieh produce them. The labors of Berthollet on the laws of affinities had also introduced new general views on chemical forces. Herein lay the subjects of Oersted's investigations during the years 1799 and 1800. Earlier studies had prepared him for these general views, and efforts to surmount certain lines of demarcation established in science by distinctions too decisive, had even directly revealed to him some of them. An analysis of the chemical philosophy of Foureroy, read by Oersted in 1799 to the Scandinavian society, and printed the following year in its bulletin, is unfortunately the sole trace which remains for the public of these first essays. We find there the alkalis and earths already ranged in a single series, which, commencing with the most energetic alkalis, terminates with a body rather acid than alkaline, silicium preceded by aluminium.

But, in 1800, the discovery of the electric pile by Volta threw all the chemists into commotion. Throughout Europe there was a desire to witness its effects.. Everywhere were constructed similar piles or columns formed of pairs composed each of a disk of copper and a disk of zinc, pairs superposed on one another and separated by a piece of moistened cloth. Soon, every one, in the modish as in the learned world, knew by experience the strange shocks and sensations felt in the wrists, in the elbows, when in each hand is held a metallic wire terminating at one of the two opposite poles of the pile, and one is thus placed in the course of the electric current to which the pile gives rise. Oersted was not among the last to make experiments with this wonderful instrument. Having applied it especially to the decomposition of divers saline solutions, he gave expression to this first law, that the quantities of alkalis and acids set at liberty in a solution, by the action of the pile, are in proportion to their respective capacities of saturation. Here, then, was a step in the career in which he was destined one day to immortalize himself.

Oersted was now 23 years of age; the time had come for him to travel, as, in their youth, the German and Scandinavian savants almost always do. He set out in 1801, and his absence extended to two and a half years. Every where he found with the learned a reception which surpassed the hopes of his friends. His natural animation, joined to a candid and unaffected self-reliance, stood him in better stead than the strongest letters of recommendation. His countenance seemed to announce a certain timidity, but no sooner did any subject awaken in