Another fine display of the aurora commenced about 10 P. M. Sept. 1st, and lasted until near daylight the next morning. A dusky red, like the reflection of an immense conflagration, overspread almost the entire heavens, beyond the zenith, far down towards the southern horizon.

24. Observations at Sea (lat. 28° 30', long. 79° 30'), Barque Pride of the Sea.

Sept. 2d, at 12h 35m A. M., a bright spot or cloud appeared in the N.W. which shot up rays resembling the aurora, and in thirty or forty minutes formed an arch across the horizon from N.W. to N.E., which became lighter as it arose, and at 1h 15m A. M. it was light enough to read the smallest print without a light. At the time the horizon was cloudy, but overhead was clear, the larger stars being just seen. At 2h 15m the arch passed over to the southward, when it became dark again.

25. Observations at Key West (lat. 24° 32'), from a Journal. A brilliant exhibition of the aurora was witnessed at this place Aug. 28th, and a still more brilliant one on the morning of Sept. 2d. The whole northern half of the heavens was tinged with crimson, red as blood. Occasional flashes of blue and white light shot up towards the zenith and then slowly melted

away.

26. Observations at Havanna, Cuba (lat. 23° 9′), by M. ANDREAS POEY.

In his former communication (Am. Jour., vol. xxviii, p. 406) Mr. Poey stated that during the auroras of Aug. 28th and Sept. 1st he was unable to obtain any indications of atmospheric elec tricity. In a later communication he states that neither at the time of these auroras, nor on the preceding or following days, was there the smallest interruption or disturbance experienced on the electro-magnetic telegraph lines of Cuba.

27. Observations at Inagua, Bahama Islands (lat. 21° 18'), from the New York Journal of Commerce.

The aurora of Aug. 28th was distinctly seen from this place, and was supposed to have been a large fire in the neighborhood. It was remarkably brilliant, but was not attended by that flashing appearance which is sometimes noticed in higher latitudes. 28. Observations at Cohe, Cuba (lat. 20°), by GEORGE F. ALLEN.

On the night of Sept. 1st a Spanish mechanic who worked for me called me out of bed to see the great light in the northern sky. He was much struck with it, and said the people in St. Jago de Cuba would think the end of the world was at hand.

I found a display which would have been considered more than ordinary even in the latitude of New York. It resembled the auroral displays occasionally seen in New York when more than usually brilliant. The same rosy light, on a darker horizon, fading off into yellower and whiter as it spread upwards, variegated occasionally with white streamers. It extended horizontally, according to my rough estimate, about one-third or twofifths of the horizon, and upwards about two-fifths of the arch of the visible heavens. It was a very brilliant display, and surprised me much by its brilliancy in that latitude.

29. Observations at Kingston, Jamaica (lat. 17° 58'), from the New York Herald.

An extraordinary light appeared in the north on the night of Sept. 1st and the morning of Sept. 2d. It appeared as if there was a colossal fire on earth which reflected its flames on the heavens. The whole island was illuminated. The light was seen at Montego Bay (lat. 18° 21') at 10 P. M., but it was not ob served at Kingston until 1 A. M. Sept. 2. It continued until 5 A. M., when it gradually disappeared. It looked as if Cuba was on fire, and many believe that a portion of this island had been destroyed by a conflagration. Other persons were of opinion that the light was that of an aurora, but the aurora has never before been seen in this latitude. A similar fire was observed on the north side of Jamaica Aug. 28th.

30. Observations at Guadeloupe, West Indies (lat. 16° 12′), from L'Institut.

On the 2d of September, from 14h till daylight, an Aurora Borealis was seen at Guadeloupe to the great astonishment of the population. Its ruddy light was noticeable in the interior of the houses. At the centre of this vast conflagration were noticed two rays of whitish light which rose parallel to each other, passing a little to the left of the pole star. The aurora attained its maximum of brightness at 3 A. M.

31. Observations at La Union, San Salvador (lat. 13° 18'), from the Gaceta del Estado.

On the night of Sept. 2d, a most extraordinary phenomenon was witnessed. About 10 o'clock, a red light illuminated all the space from north to west, to an elevation of about 30° above the horizon. The light was equal to that of day-break, but was not sufficient to eclipse the light of the stars. The sea reflected the color, and appeared as if of blood. This lasted until three in the morning, when a dense black cloud arose in the east, and commenced to spread over the colored portion of the heavens,

SECOND SERIES, VOL. XXIX, No. 86.-MARCH, 1860.

presenting a most curious spectacle; for in the parts where the cloud was not dense enough, the red light shone through, and formed a thousand fantastic figures, as if painted with fire on a black ground.

In the city of Salvador (lat. 13° 44') the same phenomenon was visible, occupying the same space in the heavens, and the red light was so vivid that the roofs of the houses and the leaves of the trees appeared as if covered with blood.

February, 1860.

ART. XXV.-Correspondence of Mr. Jerome Nicklès, dated Nancy, November 10th, 1859.

Biography-Cagniard-Latour.-We have already given some notice of this physicist, so lately lost to science; the following details are taken from an autobiography, which gives a very interesting account of the circumstances which led him to some of his discoveries. His researches may be classed under four heads; acoustics, mechanics, chemistry, and general physics having successively occupied his attention. His first invention (1809) was a pneumatic Archimidean screw, which is now in common use for conveying gases under liquids, and has received the name of the Cagniardelle. The ingenious inventor simply inverted the action of the ordinary screw of Archimedes, making it revolve from right to left. As Arago remarked in the chamber of deputies in 1844, during a discussion of the law of patents, although the Cagniardelle is nothing more than Archimedes' screw reversed, it is not less true that 2000 years had passed before any one conceived the idea of making this simple change and rendering it available in mechanics as a pneumatic machine.

The Siren (1819) as is well known, is an instrument for measuring the vibrations of the air which constitute sound. If, as had been supposed by physicists, the sounds produced by musical instruments are due to the regular succession of impulses given to the air by their vibrations, it was evident that a mechanism which would enable us to strike the air with the same rapidity and regularity should in like manner produce sounds. Reasoning in this manner, Latour was led to the invention of

this well-known and beautiful instrument.

In 1822 he published his experiments on the combined action of heat and pressure upon certain liquids, such as water, alcohol, ether and naphtha. He imagined that the dilation of a volatile liquid must have a limit beyond which, notwithstanding the compression, it would pass to the state of vapor, provided that the capacity of the vessel permitted the liquid to expand beyond its maximum of dilation. The remarkable results to which he was led by this reasoning are well known.

In 1837 he published with Mr. Demonferrand the description of an acoustic pyrometer, by which the authors proposed to render the measurement of all temperatures appreciable through the medium of sound. In the same year he examined the pressure to which the air in the trachea is exposed during the act of sounding. He had previously been employed

in investigating the pressure to which the air in the lungs is exposed when employed in sounding certain reed instruments, and had found it for the clarionette equal to the pressure of the atmosphere, plus a column of water of 30 centimeters. In order to extend these inquiries to the human larynx, it was necessary to find a person having an opening in the trachea, and yet able to produce vocal sounds at will. After long search, Cagniard-Latour found such a man, who was for his purpose as precious as the subject with the permanent gastric fistula became for the well-known experiments of Dr. Beaumont. In the same year he made known his chronometric balance, designed to measure the dynamic effects of machines in motion.

Next appeared a memoir on the alcoholic fermentation, of which these were the principal results:

1st. The yeast of beer is made up of little globular bodies, apparently vegetable, and capable of reproduction in two different manners. These bodies seem to act upon a solution of sugar only when in a state of life, and he hence conceived it probable that it is by a vital process that they transform the sugar into carbonic acid and alcohol. This investigation was suggested by a question long before proposed as the subject of a prize by the French Academy of Sciences, in the seventh year of the Republic, viz. What are the characters which distinguish among animal and vegetable matters, those which serve as ferments and those which are subject to fermentation?

Cagniard-Latour now resumed his researches upon vibrating bodies, and succeeded in producing a sound by causing a glass rod to oscillate easily between two metallic columns. The peculiarity in the sound thus obtained was that the number of vibrations indicated by it corresponded only to one-half the synchronous number of simple oscillations of the rod, although the apparatus was arranged in such a manner that each movement backwards and forwards should produce two strokes of equal intensity, by the alternate blows upon the two columns. The experiments made with this instrument enabled him to give the theory of the production of sounds by vibrating cords. During the same year (1840) he studied the production of grave tones, like those of the human voice, and made various researches to discover the mechanism of the human voice. In 1851 he laid before the Academy a memoir upon the moulinet à battemens, demonstrating some new acoustic phenomena. In two previous papers published in 1830 and 1831, upon the sounds produced by solid bodies turning with great velocity, he had shown certain facts relative to the musical tones produced by the friction of the axle of a wheel against its supports. Subsequently he conceived the idea that a solid of revolution, a cylinder for example, arranged so as to turn vertically around its axis upon two center-holes, might give rise to pulsating sounds (beatings), although moving with a feeble velocity, provided it received in the lower center-hole the friction of the revolving axis of a winch turning in an opposite direction to the cylinder. It was to the instru ments constructed according to these ideas that he gave the name of the moulinet à battemens.

We have also from Cagniard-Latour an investigation on the action of heat on different kinds of wood enclosed in hermetically sealed glass

tubes. Sir James Hall, in his experiments upon the saw-dust of pine wood and of horn in sealed gun-barrels, had observed that the mixture underwent fusion and was cemented into a sort of coal. Similar results were obtained by Latour with thick glass tubes.

These are not the only researches which we owe to this lamented phys icist; in our previous letter we mentioned that while connected with the Government powder works in 1814, he made some useful improvements in that department, especially in the glazing of powder. We also spoke of his very light, portable, and efficient flour-mill, which consisted of a steel rasp moving vertically with an alternating motion between two fixed rasps, also of steel. During the severe winter of 1816, the streams being all frozen and the mills stopped, Cagniard-Latour was directed to have an immense number of these hand-mills constructed, and thus in a few days the public were saved from the fears of a famine. We have also seen the part which he took in the establishment of gas-lighting in Paris. He was besides the constructer of an aqueduct, a model of its kind, suspended between two rocks, and formed of a single span 200 metres in length. When we consider these varied achievements, we learn with surprise that it was only in 1851 that he became a member of the Academy of Sciences.

The aurora borealis and its theory.-The late brilliant auroras have called attention to De la Rive's theory, of which we have formerly spoken, and which is explained at length in his Traite d'Electricité. Great perturbations were observed along the telegraphic lines over the European continent, similar to those remarked some years since by Matteucci in Tuscany, and Highton in England. The most remarkable fact in these electrical disturbances is that they were produced by a continuous current, while those of a thunder storm are instantaneous, and only mark points upon the paper in Morse's apparatus; the aurora of the 29th August traced continuous lines of greater or less length. These effects lasted for several days after the aurora.

*

It is fortunate that the aurora of the 29th was carefully studied by a man so competent as Coulvier-Gravier. This observer, who has studied the heavens for nearly 60 years, and has so much advanced the sciences of Cosmography and Meteorology, was found that night as usual at his post in the observatory which the government prepared for him twenty years since at the Luxembourg palace. The phenomenon was in all its splendor at 2h 45m A. M.; its extent included more than 100°, and M. Coulvier-Gravier declares that he had never seen it more beautiful during the long period of his observations.

The observations during the late auroras support the theory of De la Rive, which he has thus defined. The vapors constantly rising from the sea, and especially from the equatorial regions, carry with them to the higher regions of the air a great quantity of positive electricity, to which they serve as the vehicle, leaving the surface of the globe negatively electric. Borne to the poles by the currents which always prevail in the higher regions of the atmosphere, these vapors carry with them their electricity, and thus give to the whole atmosphere a positive electric condition, which diminishes from above downwards. This positive electricity tends unceasingly to combine with the negative electricity of the earth, *See p. 92, this volume.