in showing that he had arrived at the same results by original pro

cesses.

During the tempestuous years of the revolution, l'Huillier sought in Germany the retirement so necessary to his pursuits; and chose Tubingen as his residence. The fruit of his labours during this seclusion was a work almost wholly new, which appeared at Tubingen, in 1795, under the title Principiorum calculi differentialis et integralis expositio elementaris.

He was invited about this time, to the chair of the Higher Mathemathics in the University of Leyden; but his attachment to his native country was too deeply rooted to admit of his accepting this flattering offer and eventually, in June of the same year (1795), he attained the object of his highest ambition, by receiving, after a successful public competition, the appointment of Professor of Mathematics in the Academy of Geneva.

At a subsequent period he was associated with his friend and colleague Professor Prévost in the composition of several memoirs on the calculation of probabilities, which appeared under their joint names in the memoirs of the Berlin Academy. The questions treated of in these memoirs, although they do not reach the higher problems belonging to this department of mathematics, are yet resolved by methods remarkable for their perspicuity and elegance. L'Huillier published, in 1804, his Elémens raisonnés d' Algèbre publiés à l'usage des étudians; in 2 vols. 8vo, a work of considerable merit, as developing with clearness the true principles by which the understanding advances from that which is known to that which is unknown.

His last work, the Elemens d'Analyse Géométrique et Algébrique appliquées à la recherche des lieux géométriques, in 4to, appeared in the year 1809. It was dedicated to his former pupil, Prince Czartorynski, who was, at that time, minister of public instruction in the vast empire of Russia, but who has since become better known to Europe as the most illustrious of the exiled Poles.

The declining health of L'Huillier obliged him at length to resign a professorship which he had held during five-and-twenty years, and the duties of which he had ever discharged with the most undeviating regularity, and the most scrupulous exactness. Even while suffering acutely from a painful attack of sciatica, he insisted on being carried to his class, lest any detriment should arise to his pupils from an interruption to his lectures. Many of these pupils have subsequently distinguished themselves in their scientific career; among these may be cited one of our illustrious foreign members, Professor Sturm.

For the simplicity of his manners and the strict integrity of his character, L'Huillier was no less remarkable than for the vigour and extent of his mathematical powers: by these qualities he was endeared to his friends, and esteemed and respected by all, during a life protracted beyond the ordinary duration. His death occurred on the 28th of March, 1840, when he had nearly completed his 90th

year, with a constitution, however, which had some time previously been shattered and broken down by the infirmities incident to so advanced an age." *

FELIX SAVART, a philosopher distinguished more especially for his researches in the science of acoustics, was born on the 30th of June, 1791, at Mézières, the capital of the Department of the Ardennes, in France. He very early exhibited a decided turn for mechanical invention, and his greatest delight was to contrive and construct with his own hands musical instruments and apparatus illustrative of natural philosophy, a study of which he was passionately fond. His parents had been connected with the school of engineers at Mézières; and several of his relations having been distinguished as artists, he was himself educated with a view to the same destination. But the family afterwards removing to Metz, the path which had at first been marked out for him was abandoned, and he prepared himself for another profession, by directing his whole attention to medicine. In course of time he obtained the appointment of assistant-surgeon in the Military Hospital. Not satisfied with this probation, he, in 1814, repaired to Strasburg for the purpose of prosecuting his medical studies in the Military Hospital of that town; and he subsequently, in 1816, took a degree in medicine in the University. He then returned to his paternal roof at Metz, with the intention of settling, and of applying himself diligently to the practice of his profession. But on being restored to the scene of his youthful occupations, the renewed sight of those philosophical instruments to which so many delightful associations were attached, rekindled in full force the innate predilection for the physical sciences, which, during so long an interval, had lain dormant in his breast. The charms of science, arrayed in her most attractive colours, glittered before his imagination, and were contrasted, in his ardent mind, with the cares, the toils, and the anxieties of the profession in which he was embarking. He yielded to the powerful fascination, and disregarding all considerations of prudence, took the irrevocable step of abandoning the prospects. which were opening in a career to which his youth had been devoted, and by which alone it had, till then, been his ambition to earn fortune, reputation, and independence. Confiding in his knowedge of acoustics, which was ever his favourite study, and in which he conceived he had made discoveries, he quitted his provincial domicile, and repaired to the metropolis, as to the mart where his acquisitions would be best valued. He arrived in Paris with but scanty means of immediate support, without a friend, and unprovided with a single letter of recommendation. But fortune took him by the hand, and favoured his first endeavour to obtain notice. He presented

The above account is derived from a biographical notice by Professor De La Rive, which forms part of the Compte rendu de l'état de l'instruction publique de Genève pendant l'année scolaire, 1839-1840.

himself to Biot, and communicated to him his views, and the results of his researches in acoustics. He met with the kindest reception from that philosopher, who had himself been occupied with similar inquiries, and was well qualified to appreciate the merits of Savart. Biot was ever after his friend and patron, and it was chiefly through his influence that Savart was, in the year 1820, appointed Professor of Natural Philosophy in one of the institutions at Paris; an office which he continued to hold till the year 1827, when he was nominated a Member of the Academy of Sciences. Soon after this he was associated with Thénard, as Conservator of the Cabinet of Physics of the College of France. Thus raised to a state of independence, he had full leisure to devote himself to the science he had ever particularly cherished, and of which his labours have greatly extended the boundaries. His admirable researches on the laws of the vibrations of solid bodies of different forms and kinds, and in particular, of cords, of membranes, of rods, whether straight, or bent, or of an annular shape: of flat discs, and of solids of revolution, both solid and hollow, have furnished results of great value and importance. His investigation of the structure and functions of the several parts of the vocal organs, and his theory of the voice, both in man and in the lower animals, show great originality of research, and have thrown considerable light on a very difficult department of physiology.

Savart was elected, in the year 1839, a foreign member of the Royal Society, an honour which his unconquerable prejudice against the English, and everything emanating from England, prevented his ever acknowledging. His premature death, on the 16th of March, 1840, has, unfortunately for science, arrested the brilliant career of discovery, which he was pursuing with so much ardour and success, and will, it is to be feared, deprive the world of the fruits of many of his unfinished labours.*

• The materials for the above sketch were furnished by the funeral oration on Savart pronounced before the Royal Academy of Sciences of the Institute of France, by M. Becquerel, on the 18th of March, 1841.

The following is a list of memoirs by Félix Savart :

1. Mémoire sur la construction des instrumens à cordes et à archet. Paris, 1819.

2. Mémoire sur la communication des mouvemens vibratoires entre les corps solides. (Annales de Chimie, tome xiv.)

3. Recherches sur les vibrations des l'air. (Ibid. t. xxiv.)

4. Mémoire sur les vibrations des corps solides considérées en général. (Ibid. t. xxv.)

5. Recherches sur les usages de la membrane du tympan et de l'oreille externe. (Ibid. t. xxvi.)

6. Nouvelles recherches sur les vibrations de l'air. (Ibid. t. xxix.)

7. Mémoire sur la voix humaine. (Ibid. t. xxx.)

8. De l'influence exercée par divers milieux sur la nombre de vibrations des corps solides. (Ibid. t. xxx.)

9. Note sur la communication des mouvemens vibratoires par les liquides. (Ibid. t. xxxi.)

Description of a Thunder Storm as observed at Woolwich; with some Observations relative to the Cause of the Deflection of Electric Clouds by High Lands; and an account of the Phenomena exhibited by means of a Kite elevated during the Storm. By W. STURGEON.*

ON Saturday evening, June 14th, about eight o'clock, an electric storm passed partly over this place, exhibiting lightning the most splendid I ever beheld. The wind was pretty brisk from S. by W., about the first appearance of the storm, and if the electric clouds had obeyed the force of the wind only, the principal part of them would have come directly over us. This, however, was not the case, for instead of their being carried over Woolwich, in the direction of the wind, the most formidable group of them, and consequently the greatest fury of the storm, were deflected out of the wind's track before their arrival at Shooter's Hill, and were carried over the low lands on the other side of the hill, toward the Thames, in a direction nearly from W.S. W., to E.N.E.

The deflection of electrised clouds out of the wind's direction, though, perhaps, not much noticed, is a very common circumstance in the neihgbourhood of high lands, especially if those lands are

• From the Phil. Mag. Dec. 1834.

10. Mémoire sur la voix des oiseaux. (Ibid. t. xxxii.)

11. Note sur les modes de division des corps en vibration. (Ibid. t. xxxii.) 12. Note sur les sons produits dans l'expérience de M. Clement. (Ibid. t. xxxv.)

13. Recherches sur les vibrations normales. (Ibid. t. xxxvi.)

14. Mémoire sur un mouvement de rotation dont le systéme de parties vibrantes de certains corps devient le siége. (Ibid. t. xxxvi.)

15. Sur la décomposition de l'ammoniaque par les métaux. (Ibid. t. xxxvii.)

16. Recherches sur l'élasticité des corps qui cristallisent régulièrement. (Ibid. t. xl.)

17. Recherches sur la structure des métaux. (Ibid. xli.)

18. Mémoire sur la réaction de torsion des lames et des verges rigides. (Ibid. t. xli.)

19. Note sur la sensibilité de l'organe de l'ouïe. (lbid t. xliv.)

20. Note sur la perception des sons graves. (Ibid t. xlvii.)

21. Mémoire sur la constitution des veines liquides lancées pas des orifices circulaires en minces parois. (Ibid. t. liii.)

22. Mémoire sur le choc d'une veine liquide lancée contre un plan circulaire. (Ibid t. liv.)

23. Mémoire sur le choc de deux veines liquides animées de mouvemens directement opposés. (Ibid. t. lx.)

24. Recherches sur les vibrations longitudinales. (Ibid. t. lxv.)

25. Extrait d'un mémoire sur les modes de division des plaques vibrantes. (Ibid. t. lxxiii.)

26. Note sur les causes qui déterminent le dégre d'élévation des sons (Ibid. t. lxxv.)

27. Biot et Savart.-Sur la mesure de l'action exercée à distance sur une particule de magnétisme par un fil conjunctif. (Journal de Physique, t. xci.)

composed of materials which are bad conductors of electricity. For although they do not absolutely refuse the transmission of the electric matter driven to the surface of the hill from the lower strata of air* by the disturbing force of the condensed electric fluid in the clouds, the transfusion into the ground is too tardily performed to prevent accumulation on the surface, which consequently becomes charged in the same state as the clouds that are approaching it. A reaction immediately takes place, and a consequent repulsion or deflection of the clouds is produced. This electric force now operating in conjunction with the wind, gives the cloud a new direction of motion, and urges it over a tract of country composed of better conductors, which are more susceptible of being transpierced by the electric matter than those from which the cloud was deflected. Hence it is that electric storms are more frequent and more violent over marshy lands, rivers, &c., than over drier and more elevated tracts of country.†

These causes operated in a very beautiful manner in giving direction to the storm on Saturday evening. The principal group of clouds, as before stated, never reached Shooter's Hill, but was carried over the low wet lands, on the other side, to the Thames; and the foremost clouds were taken to the other side of the river, and over a considerable tract of the Essex marshes. At this period another direction was given to the storm, and the new combination of forces urged it in the direction of the river, a route which electric storms visiting this neighbourhood very frequently take.

Its progress down the river was exceedingly slow, owing, as I

The asperifolious plants, and the vegetable clothing of the land generally, especially at this season of the year, receive the electric fluid from the atmosphere in great abundance; and the myriads of vegetable points, sharp edges, &c., presented to the air, offer every facility for its reception on any emergency of pressure emanating from the repulsive force of a highly charged cloud. The surface of the land thus becomes charged at the expense of the air, each gradually resuming its natural electric equilibrium again, as the disturbing force withdraws its influence, by the progress of the cloud in its course. Thus new tracts of country become charged in succession as the cloud approaches them, and an electrical tide sweeps the face of the land by the floating influence above.

It is on this account that insulated kite-strings, exploring rods, &c., frequently become negatively electric at the approach, and during the transit, of clouds of this description. But if the kite or the exploring rod were to reach into the cloud, it is not likely that either of them would ever be found in a negative state. I am speaking of the principal influencing cloud, and not of those straggling thin patches in their vicinity, which frequently be came negative by a portion of the electric matter which they before possessed being driven out of them by the predominating electric force of the superior cloud. In the same manner, an insulated metallic rod furnished with fine points or sharp edges at its further extremity, may have its natural electric

+ Immense tracts of flat country, frequently become charged in the same manner and from the same cause as ranges of hills are charged; but the repulsive force from such places is directed vertically, and not so directly opposed to the horizontal direction of the cloud's motion as that proceeding from the side of a high bill.