Volume I Part 19 (1/2)
After having made astronomical observations with the same instruments, in our northern climates and in the torrid zone, we are surprised at the effect produced in the latter (by the transparency of the air, and the less extinction of light), on the clearness with which the double stars, the satellites of Jupiter, or certain nebulae, present themselves. Beneath a sky equally serene in appearance, it would seem as if more perfect instruments were employed; so much more distinct and well defined do the objects appear between the tropics. It cannot be doubted, that at the period when equinoctial America shall become the centre of extensive civilization, physical astronomy will make immense improvements, in proportion as the skies will be explored with excellent gla.s.ses, in the dry and hot climates of c.u.mana, Coro, and the island of Margareta. I do not here mention the ridge of the Cordilleras, because, with the exception of some high and nearly barren plains in Mexico and Peru, the very elevated table-lands, in which the barometric pressure is from ten to twelve inches less than at the level of the sea, have a misty and extremely variable climate. The extreme purity of the atmosphere which constantly prevails in the low regions during the dry season, counterbalances the elevation of site and the rarity of the air on the table-lands.
The elevated strata of the atmosphere, when they envelope the ridges of mountains, undergo rapid changes in their transparency.
The night of the 11th of November was cool and extremely fine. From half after two in the morning, the most extraordinary luminous meteors were seen in the direction of the east. M. Bonpland, who had risen to enjoy the freshness of the air, perceived them first.
Thousands of bolides and falling stars succeeded each other during the s.p.a.ce of four hours. Their direction was very regular from north to south. They filled a s.p.a.ce in the sky extending from due east 30 degrees to north and south. In an amplitude of 60 degrees the meteors were seen to rise above the horizon at east-north-east and at east, to describe arcs more or less extended, and to fall towards the south, after having followed the direction of the meridian. Some of them attained a height of 40 degrees, and all exceeded 25 or 30 degrees. There was very little wind in the low regions of the atmosphere, and that little blew from the east. No trace of clouds was to be seen. M. Bonpland states that, from the first appearance of the phenomenon, there was not in the firmament a s.p.a.ce equal in extent to three diameters of the moon, which was not filled every instant with bolides and falling stars. The first were fewer in number, but as they were of different sizes, it was impossible to fix the limit between these two cla.s.ses of phenomena.
All these meteors left luminous traces from five to ten degrees in length, as often happens in the equinoctial regions. The phosph.o.r.escence of these traces, or luminous bands, lasted seven or eight seconds. Many of the falling stars had a very distinct nucleus, as large as the disk of Jupiter, from which darted sparks of vivid light. The bolides seem to burst as by explosion; but the largest, those from 1 to 1 degree 15 minutes in diameter, disappeared without scintillation, leaving behind them phosph.o.r.escent bands (trabes) exceeding in breadth fifteen or twenty minutes. The light of these meteors was white, and not reddish, which must doubtless be attributed to the absence of vapour and the extreme transparency of the air. For the same reason, within the tropics, the stars of the first magnitude have, at their rising, a light decidedly whiter than in Europe.
Almost all the inhabitants of c.u.mana witnessed this phenomenon, because they had left their houses before four o'clock, to attend the early morning ma.s.s. They did not behold these bolides with indifference; the oldest among them remembered that the great earthquakes of 1766 were preceded by similar phenomena. The Guaiqueries in the Indian suburb alleged ”that the bolides began to appear at one o'clock; and that as they returned from fis.h.i.+ng in the gulf, they had perceived very small falling stars towards the east.” They a.s.sured us that igneous meteors were extremely rare on those coasts after two o'clock in the morning.
The phenomenon ceased by degrees after four o'clock, and the bolides and falling stars became less frequent; but we still distinguished some to north-east by their whitish light, and the rapidity of their movement, a quarter of an hour after sunrise.
This circ.u.mstance will appear less extraordinary, when I mention that in broad daylight, in 1788, the interior of the houses in the town of Popayan was brightly illumined by an aerolite of immense magnitude. It pa.s.sed over the town, when the sun was s.h.i.+ning clearly, about one o'clock. M. Bonpland and myself, during our second residence at c.u.mana, after having observed, on the 26th of September, 1800, the immersion of the first satellite of Jupiter, succeeded in seeing the planet distinctly with the naked eye, eighteen minutes after the disk of the sun had appeared in the horizon. There was a very slight vapour in the east, but Jupiter appeared on an azure sky. These facts bear evidence of the extreme purity and transparency of the atmosphere in the torrid zone. The ma.s.s of diffused light is the less, in proportion as the vapours are more perfectly dissolved. The same cause which checks the diffusion of the solar light, diminishes the extinction of that which emanates either from bolides from Jupiter, or from the moon, seen on the second day after its conjunction. The 12th of November was an extremely hot day, and the hygrometer indicated a very considerable degree of dryness for those climates. The reddish vapour clouded the horizon anew, and rose to the height of 14 degrees. This was the last time it appeared that year; and I must here observe, that it is no less rare under the fine sky of c.u.mana, than it is common at Acapulco, on the western coast of Mexico.
We did not neglect, during the course of our journey from Caracas to the Rio Negro, to enquire everywhere, whether the meteors of the 12th of November had been perceived. In a wild country, where the greater number of the inhabitants sleep in the open air, so extraordinary a phenomenon could not fail to be remarked, unless it had been concealed from observation by clouds. The Capuchin missionary at San Fernando de Apure,* (* North lat.i.tude 7 degrees 53 minutes 12 seconds; west longitude 70 degrees 20 minutes.), a village situated amid the savannahs of the province of Varinas; the Franciscan monks stationed near the cataracts of the Orinoco and at Maroa,* (* North lat.i.tude 2 degrees 42 minutes 0 seconds; west longitude 70 degrees 21 minutes.) on the banks of the Rio Negro; had seen numberless falling-stars and bolides illumine the heavens.
Maroa is south-west of c.u.mana, at one hundred and seventy-four leagues distance. All these observers compared the phenomenon to brilliant fireworks; and it lasted from three till six in the morning. Some of the monks had marked the day in their rituals; others had noted it by the proximate festivals of the Church.
Unfortunately, none of them could recollect the direction of the meteors, or their apparent height. From the position of the mountains and thick forests which surround the Missions of the Cataracts and the little village of Maroa, I presume that the bolides were still visible at 20 degrees above the horizon. On my arrival at the southern extremity of Spanish Guiana, at the little fort of San Carlos, I found some Portuguese, who had gone up the Rio Negro from the Mission of St. Joseph of the Maravitans. They a.s.sured me that in that part of Brazil the phenomenon had been perceived at least as far as San Gabriel das Cachoeiras, consequently as far as the equator itself.* (* A little to the north-west of San Antonio de Castanheiro. I did not meet with any persons who had observed this meteor, at Santa Fe de Bogota, at Popayan, or in the southern hemisphere, at Quito and Peru. Perhaps the state of the atmosphere, so changeable in these western regions, prevented observation.)
I was forcibly struck by the immense height which these bolides must have attained, to have rendered them visible simultaneously at c.u.mana, and on the frontiers of Brazil, in a line of two hundred and thirty leagues in length. But what was my astonishment, when, on my return to Europe, I learned that the same phenomenon had been perceived on an extent of the globe of 64 degrees of lat.i.tude, and 91 degrees of longitude; at the equator, in South America, at Labrador, and in Germany! I saw accidentally, during my pa.s.sage from Philadelphia to Bordeaux,* (* In the Memoirs of the Pennsylvanian Society.) the corresponding observation of Mr.
Ellicot (lat.i.tude 30 degrees 42); and upon my return from Naples to Berlin, I read the account of the Moravian missionaries among the Esquimaux, in the Bibliothek of Gottingen.
The following is a succinct enumeration of the facts:
First. The fiery meteors were seen in the east, and the east-north-east, at 40 degrees of elevation, from 2 to 6 a.m. at c.u.mana (lat.i.tude 10 degrees 27 minutes 52 seconds, longitude 66 degrees 30 minutes); at Porto Cabello (lat.i.tude 10 degrees 6 minutes 52 seconds, longitude 67 degrees 5 minutes); and on the frontiers of Brazil, near the equator, in longitude 70 degrees west of the meridian of Paris.
Second. In French Guiana (lat.i.tude 4 degrees 56 minutes, longitude 54 degrees 35 minutes) ”the northern part of the sky was suffused with fire. Numberless falling-stars traversed the heavens during the s.p.a.ce of an hour and a half, and shed so vivid a light, that those meteors might be compared to the blazing sheaves which shoot out from fireworks.” The knowledge of this fact rests upon the highly trustworthy testimony of the Count de Marbois, then living in exile at Cayenne, a victim to his love of justice and of rational, const.i.tutional liberty.
Third. Mr. Ellicot, astronomer to the United States, having completed his trigonometric operations for the rectification of the limits on the Ohio, being on the 12th of November in the gulf of Florida, in lat.i.tude 25 degrees, and longitude 81 degrees 50 minutes, saw in all parts of the sky, ”as many meteors as stars, moving in all directions. Some appeared to fall perpendicularly; and it was expected every minute that they would drop into the vessel.” The same phenomenon was perceived upon the American continent as far as lat.i.tude 30 degrees 42 minutes.
Fourth. In Labrador, at Nain (lat.i.tude 56 degrees 55 minutes), and Hoffenthal (lat.i.tude 58 degrees 4 minutes); in Greenland, at Lichtenau (lat.i.tude 61 degrees 5 minutes), and at New Herrnhut (lat.i.tude 64 degrees 14 minutes, longitude 52 degrees 20 minutes); the Esquimaux were terrified at the enormous quant.i.ty of bolides which fell during twilight at all points of the firmament, and some of which were said to be a foot broad.
Fifth. In Germany, Mr. Zeissing, vicar of Ittetsadt, near Weimar (lat.i.tude 50 degrees 59 minutes, longitude 9 degrees 1 minute east), perceived, on the 12th of November, between the hours of six and seven in the morning (half-past two at c.u.mana), some falling-stars which shed a very white light. Soon after, in the direction of south and south-west, luminous rays appeared from four to six feet long; they were reddish, and resembled the luminous track of a sky-rocket. During the morning twilight, between the hours of seven and eight, the sky, in the direction of south-west, was observed from time to time to be brightly illumined by white lightning, running in serpentine lines along the horizon. At night the cold increased and the barometer rose. It is very probable, that the meteors might have been observed more to the east, in Poland and in Russia.* (* In Paris and in London the sky was cloudy. At Carlsruhe, before dawn, lightning was seen in the north-west and south-east. On the 13th of November a remarkable glare of light was seen at the same place in the south-east.)
The distance from Weimar to the Rio Negro is 1800 nautical leagues; and from the Rio Negro to Herrnhut in Greenland, 1300 leagues.
Admitting that the same fiery meteors were seen at points so distant from each other, we must suppose that their height was at least 411 leagues. Near Weimar, the appearance like sky-rockets was observed in the south and south-east; at c.u.mana, in the east and east-north-east. We may therefore conclude, that numberless aerolites must have fallen into the sea, between Africa and South America, westward of the Cape Verd Islands. But since the direction of the bolides was not the same at Labrador and at c.u.mana, why were they not perceived in the latter place towards the north, as at Cayenne? We can scarcely be too cautious on a subject, on which good observations made in very distant places are still wanting. I am rather inclined to think, that the Chayma Indians of c.u.mana did not see the same bolides as the Portuguese in Brazil and the missionaries in Labrador; but at the same time it cannot be doubted (and this fact appears to me very remarkable) that in the New World, between the meridians of 46 and 82 degrees, between the equator and 64 degrees north, at the same hour, an immense number of bolides and falling-stars were perceived; and that those meteors had everywhere the same brilliancy, throughout a s.p.a.ce of 921,000 square leagues.
Astronomers who have lately been directing minute attention to falling-stars and their parallaxes, consider them as meteors belonging to the farthest limits of our atmosphere, between the region of the Aurora Borealis and that of the lightest clouds.* (*
According to the observations which I made on the ridge of the Andes, at an elevation of 2700 toises, on the moutons, or little white fleecy clouds, it appeared to me, that their elevation is sometimes not less than 6000 toises above the level of the coast.) Some have been seen, which had not more than 14,000 toises, or about five leagues of elevation. The highest do not appear to exceed thirty leagues. They are often more than a hundred feet in diameter: and their swiftness is such, that they dart in a few seconds through a s.p.a.ce of two leagues. Of some which have been measured, the direction was almost perpendicularly upward, or forming an angle of 50 degrees with the vertical line. This extremely remarkable circ.u.mstance has led to the conclusion, that falling-stars are not aerolites which, after having hovered a long time in s.p.a.ce, unite on accidentally entering into our atmosphere, and fall towards the earth.* (* M. Chladni, who at first considered falling-stars to be aerolites, subsequently abandoned that idea.)
Whatever may be the origin of these luminous meteors, it is difficult to conceive an instantaneous inflammation taking place in a region where there is less air than in the vacuum of our air-pumps; and where (at the height of 25,000 toises) the mercury in the barometer would not rise to 0.012 of a line. We have ascertained the uniform mixture of atmospheric air to be about 0.
003, only to an elevation of 3000 toises; consequently not beyond the last stratum of fleecy clouds. It may be admitted that, in the first revolutions of the globe, gaseous substances, which yet remain unknown to us, have risen towards that region through which the falling-stars pa.s.s; but accurate experiments, made upon mixtures of gases which have not the same specific gravity, show that there is no reason for supposing a superior stratum of the atmosphere entirely different from the inferior strata. Gaseous substances mingle and penetrate each other on the least movement; and a uniformity of their mixture may have taken place in the lapse of ages, unless we believe them to possess a repulsive action of which there is no example in those substances we can subject to our observations. Farther, if we admit the existence of particular aerial fluids in the inaccessible regions of luminous meteors, of falling-stars, bolides, and the Aurora Borealis; how can we conceive why the whole stratum of those fluids does not at once ignite, but that the gaseous emanations, like the clouds, occupy only limited s.p.a.ces? How can we suppose an electrical explosion without some vapours collected together, capable of containing unequal charges of electricity, in air, the mean temperature of which is perhaps 25 degrees below the freezing point of the centigrade thermometer, and the rarefaction of which is so considerable, that the compression of the electrical shock could scarcely disengage any heat? These difficulties would in great part be removed, if the direction of the movement of falling-stars allowed us to consider them as bodies with a solid nucleus, as cosmic phenomena (belonging to s.p.a.ce beyond the limits of our atmosphere), and not as telluric phenomena (belonging to our planet only).
Supposing the meteors of c.u.mana to have been only at the usual height at which falling-stars in general move, the same meteors were seen above the horizon in places more than 310 leagues distant from each other.* (* It was this circ.u.mstance that induced Lambert to propose the observation of falling-stars for the determination of terrestrial longitudes. He considered them to be celestial signals seen at great distances.) How great a disposition to incandescence must have prevailed on the 12th November, in the higher regions of the atmosphere, to have rendered during four hours myriads of bolides and falling stars visible at the equator, in Greenland, and in Germany!
M. Benzenberg observes, that the same cause which renders the phenomenon more frequent, has also an influence on the large size of the meteors, and the intensity of their light. In Europe, the greatest number of falling stars are seen on those nights on which very bright ones are mingled with very small ones. The periodical nature of the phenomenon augments the interest it excites. There are months in which M. Brandes has reckoned in our temperate zone only sixty or eighty falling-stars in one night; and in other months their number has risen to two thousand. Whenever one is observed, which has the diameter of Sirius or of Jupiter, we are sure of seeing the brilliant meteor succeeded by a great number of smaller ones. If the falling stars be very numerous during one night, it is probable that they will continue equally so during several weeks. It would seem, that in the higher regions of the atmosphere, near that extreme limit where the centrifugal force is balanced by gravity, there exists at regular periods a particular disposition for the production of bolides, falling-stars, and the Aurora Borealis.* (* Ritter, like several others, makes a distinction between bolides mingled with falling-stars and those luminous meteors which, enveloped in vapour and smoke, explode with great noise, and let fall (chiefly in the day-time) aerolites. The latter certainly do not belong to our atmosphere.) Does the periodical recurrence of this great phenomenon depend upon the state of the atmosphere? or upon something which the atmosphere receives from without, while the earth advances in the ecliptic? Of all this we are still as ignorant as mankind were in the days of Anaxagoras.
With respect to the falling-stars themselves, it appears to me, from my own experience, that they are more frequent in the equinoctial regions than in the temperate zone; and more frequent above continents, and near certain coasts, than in the middle of the ocean. Do the radiation of the surface of the globe, and the electric charge of the lower regions of the atmosphere (which varies according to the nature of the soil and the positions of the continents and seas), exert their influence as far as those heights where eternal winter reigns? The total absence of even the smallest clouds, at certain seasons, or above some barren plains dest.i.tute of vegetation, seems to prove that this influence can be felt as far as five or six thousand toises high.
A phenomenon a.n.a.logous to that which appeared on the 12th of November at c.u.mana, was observed thirty years previously on the table-land of the Andes, in a country studded with volcanoes. In the city of Quito there was seen in one part of the sky, above the volcano of Cayamba, such great numbers of falling-stars, that the mountain was thought to be in flames. This singular sight lasted more than an hour. The people a.s.sembled in the plain of Exido, which commands a magnificent view of the highest summits of the Cordilleras. A procession was on the point of setting out from the convent of San Francisco, when it was perceived that the blaze on the horizon was caused by fiery meteors, which ran along the skies in all directions, at the alt.i.tude of twelve or thirteen degrees.
CHAPTER 1.11.
Pa.s.sAGE FROM c.u.mANA TO LA GUAYRA.