alarmingly distended the balloon. They were forced to let out some gas; after which they ascended to an altitude in which it was almost impossible to endure the cold. Their teeth chattered without ceasing. Mr. Robertson's veins swelled, and blood came from his nose. Mr. Lhoest complained that his head swelled so much, that he could not keep on his hat; and they both felt a great degree of numbness, and inclination to sleep. This was at about the height of 2600 toises. Unable to continue any longer they descended, and would have alighted at Badenburg, near Winsen, on the Lube, but the inhabitants fled with the greatest alarm, and took them for spectres. They therefore continued their voyage till they arrived at Wichtenbeck, on the way to Zell. As they first arose the atmosphere was calm, but cloudy; as they ascended, the heat decreased, and they could look at the sun without being dazzled. The barometer fell from 27 to 14 inches, and the thermometer to 4 below zero. As they still ascended, the barometer fell to 12 inches.; but here the cold was insupportable, although the thermometer was only one degree below the freezing point, and they respired very rapidly; the pulsations, also, became greatly accelerated. Mr. Robertson made the following experiments, and observations:

i. He let fall a drop of ether on a piece of glass, and it evaporated in four seconds.

ii. He electrified glass and sealing-wax, but they gave no intimation of an accumulation of fluid that could be communicated to other bodies; and the voltaic pile, which, when the balloon was free from the earth, acted with full force, yielded only one-tenth part of its electricity.

iii. The dipping needle lost its magnetic virtue, and could not be brought to that direction which it had at the surface of the earth.

iv. He struck with a hammer oxygenated muriate of potash. The explosion though it made not a very loud noise, was almost insufferable to the ear, and they moreover, observed that though they spoke very loudly, they could with great difficulty hear each other.

v. Water began to boil with a moderate degree of heat, maintained by quick lime.

vi. Mr. Robertson having carried two birds with him, the rarefaction of the air killed one of them, and the other could not fly, but lay extended on its back and fluttered with its wings. vii. Mr. Robertson could not extract any electricity from the atmospheric electrometer and condenser.

1

viii. The clouds, Mr. R. observed, never rise above 2000 toises, and it was only in ascending and descending through them that he obtained any positive electricity. The greatest altitude during this voyage was 2600 toises.

41. Mr. Robertson also ascended from Petersburg, on the 30th June, 1804, with the professor Sacharof, to make certain experiments proposed by the academy, and took 12 exhausted flasks, a barometer, thermometer, two electrometers sealing wax, and sulphur, compass, a magnetic needle, a seconds watch, a bell, a speaking trumpet, a prism of crystal, unslacked lime, &c. To ascertain the position of the balloon, they

fixed perpendicularly an achromatic telescope, in an aperture in the bottom of the car, which showed terrestrial objects distinctly; two sheets of black paper were also fixed at right angles, suspended from the car with a piece of thread to indicate any variation in the direction of the balloon, which contrivance they called the way-wiser. About a quarter past seven in the evening, the barometer being at thirty inches, and the centigrade thermometer at 19°. they ascended, and at thirty-one minutes past seven, the barometer sunk to twenty-nine inches, and the thermometer to 18°. The first cask was now filled with air, and when the barometer had fallen another inch, another cask was filled. The towns and villages being now obscured by a fog, the paper way-wiser was thrown out, and showed the direction of the balloon, for as the balloon fell, the way-wiser being lighter, and meeting more resistance in falling than the balloon, flew up, and when it rose, sunk down to the full length of its thread.

At other times it was seen in a diagonal direction, and pointed out with considerable accuracy the general direction and movements of the machine. At twenty-five minutes past eight, the barometer being at twenty-six inches, another cask was filled with air, and another, when it was twenty-five inches, and so on for every inch descent of the mercury. At half-past nine o'clock, the barometer being at twenty-two inches the thermometer at 4°, 30', the voyagers saw the sun which was about half obscured by the fogs or the horizon or both. A piece of sealing wax rubbed with cloth, put in motion Bennet's Electrometer. A magnetic needle placed by M. Sacharof on a pin, elevated its north end, and lowered its south end, making an angle of 10, or 12°, but ever after descending, the same needle assumed an horizontal position. The æronauts experienced no inconvenience except that their ears were benumbed with cold. There were white clouds a great way above the balloon, but the sky was in general clear and bright. They could however see no stars. As they were now floating over some towns and villages, M. Sacharof took his speaking trumpet and directed it toward the earth, and called as loud as he was able; after a lapse of ten seconds his words returned in echo, and sounded distinctly and clearly: calculating by the velocity of sound, he thought himself 5700 feet from the earth! To render the descent as safe as possible, all the instruments, clothing, &c. with an anchor were let down by a rope, but the handle being drawn a considerable distance along the ground, many of the instruments were destroyed, and of the eight casks that had been charged with air at different altitudes, four only were fit for experiment. These last two voyages may be said to be the first ever under. taken with the general view of investigating philosophy and science.

42. Besides the account given by Messrs Robertson and Sacharof, with respect to the magnet, that there was a change in the dipping power of the needle.

M. Saussure, from experiments made on the Col du Geant, at the height of 3435 metres

above the level of the sea, thought he observed a sensible decrease of the magnetic virtue. Some æronauts had stated that at a certain height the power of magnetism entirely vanishes.

43. To ascertain the truth or fallacy of these assertions, and also to try the experiment of Saussure in isolated situations remote from the influence of any local attractions; to explore the constitution of the higher atmosphere, its fitness or unfitness for respiration, &c.; and also to make electrical, chemical, and meteorological observations, M. Biot and Gay Lussac, two young philosophers, educated at the Polytechnic school in Paris, proposed taking an aerial voyage. Their plan was patronised by the French government. The balloon which once visited Egypt, was delivered to these gentlemen, for the purpose of the excursion; the artist who constructed it was appointed to repair it under their direction, and every facility was to be afforded them. Besides the usual provision of barometers, thermometers, hygrometers, and electrometers, they had two compasses, a dipping-needle, and another fine needle carefully magnetized, and suspended by a very delicate silk thread for ascertaining, by its vibrations, the force of attraction in the upper strata of the atmosphere. To examine the electricity of the strata they carried up several metallic wires from sixty to 300 feet in length, and a small electrophorus slightly charged. For galvanic experiments, they had procured a few discs of zinc and copper, with some frogs, insects, and birds. It was also proposed to bring back air collected at as great a height as possible, for chemical analysis, for which purpose they had a glass ball closely shut up, previously exhausted of air; so that they had only to open and shut it up carefully, by means of the stopper.

44. They ascended from the Conservatoire des Arts, or repository of models, formerly the convent of St. Martin; on 23rd of August, 1804, the barometer being 30, 10. inches; the thermometer 61°, 7'. on Fahrenheit's scale, and Saussure's hygrometer 80°, 8'. near the point of absolute humidity. In a few moments they entered the region of the clouds, which seemed like a thin fog, and communicated a slight sensation of humidity. The balloon becoming quite inflated, they let out part of their gas, and threw out some ballast to give a greater elevation. They now shot through the clouds, and reached an altitude of 6500 English feet. Viewed from above, the clouds had the usual whitish appearance, exhibiting an elegant variety of gentle swells and undulations, resembling a wide plain of snow. At this altitude they commenced their experiments, and first of all employed the magnetic needle. This was attracted by iron; but owing to a slow rotatory motion of the balloon, they found it impossible to determine its rate of oscillation. The rotation showed itself, when any of the ropes were brought in a straight line with the edge of the clouds on any terrestrial objects, the contours of which were sensibly distinguishable the one from the other. Electricity was excited by the contact of insulated metals, as upon the earth. An electric pile, prepared with twenty discs of copper, and as many of zinc, exhibited all the

usual symptoms, the pungent taste, the nervous
shock, and the decomposition of water. This
might have been expected, says M. Biot, since
the action of this pile does not cease, even in a
vacuum. They afterwards attained the altitude of
8,940 feet, but afterwards settled at 8,600 feet.
At this great elevation the animals seemed to
suffer from the rarety of the air. They let off a
bee, which flew away making its usual humming
noise. The thermometer had fallen to 56°, 4′.
by Fahrenheit; yet so far were they from
experiencing cold, that they were absolutely
scorched by the rays of the sun, and were ob-
liged to lay aside their gloves from the incon
venience occasioned by the heat. Their pulsa-
tions were much accelerated, that of Gay Lus-
sac was increased from sixty to eighty in a
minute, and his companion's from 79 to 111,
attended, however, with no difficulty of breath-
ing; Gay Lussac, whose frame was less robust,
experienced the less acceleration. The balloon
continued its rotatory motion, which rendered
it still difficult to observe, with accuracy, the
oscillations of the magnetic needle; but on
looking attentively down upon the surface of
of the conglomerated clouds, they observed that
the balloon revolved slowly, first in one di-
rection, next in the contrary one. They there-
fore, seized the few minutes of quiescence be-
tween these opposite motions for their experi-
ments and observations upon the needle; but
in these pauses, though they set the needle to
vibrate, they were rarely able to count more than
from five to ten oscillations. From a number
of trials made between the altitudes of 9,500 and
13,000 feet, they calculated seven for the mean
length of an oscillation, which at the earth is but
7, and attributing so nice a distinction to the
imperfection of the experiment, they concluded
that the force of the magnetic attraction had in no
degree diminished, at the greatest elevation they
could possibly reach; and the direction of this
M.
force, in their opinion, remained the same.
Biot confesses that he was not able to observe
the needle with accuracy, and therefore, cannot
positively assert that it experiences no variation ;
but he thinks it highly probable that it does not,
its horizontal force having undergone no change,
or if any, it must have been very inconsiderable,
because the magnetic bars brought into equi-
librium before their departure, retained their
horizontality during the whole journey.
weather and the disposition of the apparatus,
however, prevented their coming to any nice
conclusion.

The

A

45. At the altitude of 11,000 feet, they liberated a green linnet, which flew away directly; but soon feeling itself abandoned in the midst of an unknown ocean, returned and settled on the balloon, then collecting itself, took a second flight, and darted downward to the earth, describing a tortuous, yet almost perpendicular track. pigeon which they sent off, offered a more curious spectacle: He rested a short time on the edge of the car, and looked down as if measuring the breadth of that unexplored sea before him, then launching into the abyss, fluttered irregularly, and after a few strokes, whirling in spiral like birds of prey, precipitated himself toward

the mass of extended clouds, and became invisible. Our æronauts had now arrived at the altitude of 13,385 feet, and had not yet made electrical experiments. In order to try the apparatus an insulated wire was let down 240 feet in length, and electricity was extracted from its upper extremity, which when applied to the electrometer, appeared to be resinous, or negative, confirming the observations of Saussure and Volta, respecting the increase of electricity, observed in ascending the atmosphere. The experiment was tried, first, by destroying the atmospheric electricity by means of the vitreous electricity, from the electrophorus; and, secondly, by destroying the vitreous electricity, extricated from the electrophorus, by means of the atmospheric electricity. The latter must therefore, have been resinous. The inference drawn from these experiments was, that electricity increases as we ascend farther from the surface of the earth, agreeably to the experiments and observations of Volta and Saussure. The diminution of temperature in the higher regions, was not so great as might have been expected, and less than what is experienced in the same altitude on the tops of mountains, even at the elevation of 12,800 feet. The thermometer was at 51°, by Fahrenheit, while it stood as low as 634, at the observatory, being a decrement of one degree for every 1000 feet of ascent.

46. The hygrometer, or rather hygroscope of Saussure advanced regularly towards dryness in proportion to the altitude they attained. At the time of the ascent, this instrument indicated 80°, 8′, at 16°, 5′ of the centrigade thermometer, but at the elevation of 13,000 feet, it changed from 80°, 8', to 30°, from which it would appear that the air is much drier in the upper regions than at the earth, which was the conclusion of M. Biot. The rectitude of it however, has been questioned. It has been observed that the indications of the hygroscope depend on the relative attraction for humidity possessed by the substance employed, and the medium in which it is immersed. But air has its disposition to retain humidity, always augmented by rarefaction, and consequently such attraction must materially affect the hygroscope. Such are the results of this voyage, which has been considered the most scientific of any that have been hitherto made. Having expended all their ballast they descended gradually till at about the altitude of 4000 feet, they entered the stratum of clouds extending horizontally with the surface of the earth, and at last reached the ground. There being no people near the spot to stop the machine, they were dragged in the car to some distance along the fields. M. Biot was so overpowered by the alarm of their descent as to lose entire possession of himself, and the only

way left of avoiding the dangers that threatened them, was, by discharging the remaining gas.

47. M. Biot afterwards presented himself to the Institute as a candidate for a second ascent. He did not however repeat his excursion; but at the request of several Parisian philosophers M. Gay Lussac made another voyage on the 15th of September, from the same place, at about fortynine minutes past nine in the morning. He reduced his apparatus, and adapted it better to his circumstances. Aware that he could only observe the magnetic needle during the short periods of quiescence, intervening between the rotatory motions of the balloon, he preferred one of not more than six inches long, the oscillations of which were more rapid. The dipping needle was magnetized, and adjusted by M. Coulomb, and the thermometer was inclosed within two concentric cylinders of pasteboard covered with gilt paper, proper to prevent the immediate action of the sun. The hygrometer, on Richer's principle, with four bodies, was sheltered in a similar manner. Two glass vessels were exhausted, with the intention of bringing down air from the higher regions, and the mercurial gauge stood at the twenty-fifth part of an inch. The barometer at the period of ascent, stood at 76,525 centimetres, or 30.66 English inches. The hygrometer at 57.5, and the thermometer at 27.50, of the centigrade, or 82° of Fahrenheit's thermometer. At the elevation of 3000 feet, he saw a light vapour dispersed through the whole atmosphere below him, through which distant objects might be confusedly seen. At the height of 3032 metres, or about 9950 English feet, he commenced his experiments on the magnetic needle, which made twenty oscillations in 83°, the same as it would have made at the earth in 83°, 20°. At the height of 12,680 feet, the needle taking the mean amplitude of the oscillations was 31° as at the observatory. Owing to the wind and other difficulties, he was obliged to renounce any further observations. In his experiments with the dipping needle, he was equally unsuccessful, for the dryness formed by the sun in rarefied air, was so great, that the compass became damaged by the bending of the metallic circle on which the divisions were traced out, by which all his deductions were rendered uncertain: he there fore proceeded to his other experiments.

48. At the altitude of 14,000 feet, a key held in the magnetic direction repelled with one end, and attracted with the other the North Pole of the needle, and even at the increased altitude of 20,150 feet, he found no sensible difference; whence, he concludes magnetism to be the same at the greatest elevation.

The table of observations will, perhaps, give the clearest view of the result of his experiments to the curious reader.

Table of the Observations of M. GAY LUSSAC. in his ascent on the 15th of September, 1804.

of proportions, as that at the surface of the earth; each 1,000 parts being 215 of oxygen.

50. The next voyage which we must notice by way of warning to future adventurers, was one of the few fatal ones. On the 7th April, 1806, M. Mosment ascended from Lisle, apparently under auspicious circumstances. During his ascent, he dropped a dog with a parachute, which came safely to the ground, and about one o'clock something was seen descending slowly through the air, and proved to be the flag of M. Mosment. Soon after, a murmur was circulated that the body of the æronaut was found in one of the fosses of the city, lifeless and covered with blood, which proved in the end but too correct. The misfortune has been attributed to the shallowness of the car, by which, he is supposed to have lost his balance in throwing out the dog, and precipitated to the earth.

51. On the 4th of August, M. Garnerin, ascended from Paris at eleven o'clock in the evening, for the purpose of making nocturnal observations, under the Russian flag. His balloon was illuminated by twenty lamps, and formed a very splendid appearance; rockets let off at Tivoli, seemed to him scarcely to rise above the earth, and Paris appeared studded with numerous stars. In forty minutes he rose to an elevation of 13,200 feet at twelve o'clock, when 3,600 feet from the earth, he heard the barking of dogs; at two o'clock, he saw several meteors flying around him; at half past three, he beheld the sun rising in magnificence and grandeur above the ocean of clouds, and the gas expanding, he rose to the height of 15,000 feet, and after a lapse of more than seven hours, descended at Loges, forty-five leagues from Paris.

52. He took a second nocturnal voyage, on the 21st September, in which he was exposed to great danger. He commenced his voyage as before from Tivoli, and was at first carried with unexampled rapidity to an immense height, when he began to prognosticate a storm. The balloon dilated to an alarming degree, and having neglected his apparatus for conducting the gas away from the lamps in its escape, he could not manage the balloon he therefore with one hand made an opening of two feet diameter, and with the other put out all the lamps he could, and was, without a regulating valve, tossed about from current to current; his ballast was gone, and in this condition, the balloon rose through thick clouds, then sunk, then struck the earth and rebounded to an amazing altitude: the storm dashed him against the mountains, and after many severe shocks he became for a time insensible. On recovering his senses, he found he had been carried to Tonnere, in a storm of thunder. His anchors shortly hooked in a tree, and he alighted in seven hours and a half from his ascension, 300 miles from Paris, having travelled a distance of forty miles in an hour. This, however, is not more than half the distance he travelled on one occasion in this country, when he went from London to Colchester, a distance of fifty miles, in three-quarters of an hour.

53. Since this period, the names of Sadler,

Green, Graham, and other adventurers have been connected with the ascent of balloons, for the purpose of emolument, in England: sometimes exhibiting the triumphs, and sometimes the paucity of scientific attainments in their conductors. But we know of no further efforts than the above, to increase the materials of science itself, by these voyages.

54. The utility of Eronautic studies and experiments has been very much questioned even by philosophical minds. M. Cavallo, well known in the philosophical world, suggested long ago that small balloons, especially those made of paper, and raised by means of spirit of wine, may serve to explore the direction of the winds in the upper regions of the atmosphere, particularly when there is a calm below; and we see the French æronauts adopted this idea, that they might serve also for signals in various circumstances, in which no other means can be used; and letters or other small things may be easily sent by them; for instance, from ships that cannot safely land on account of storms; from besieged places, islands, or the like. The larger arostatic machines, he adds, may answer all the above mentioned purposes in a better manner; and they may, besides, be used as a help to a person who wants to ascend a mountain, or a precipice, or to cross a river; and perhaps one of the machines tied to a boat by a long rope, may be, in some cases, a better sort of sail than any that is used at present. Their conveying people from place to place with great swiftness, and without trouble, may be of essential use, even if the art of guiding them in a direction different from that of the wind should never be discovered. By means of those machines the shape of certain seas and lands may be better ascertained; men may ascend to the tops of mountains they never visited before; they may be carried over marshy and dangerous grounds; they may by that means come out of a besieged place, or an island; they may, in hot climates, ascend to a cold region of the atmosphere, either to refresh themselves, or to observe the ice which is never seen below; and, in short, they may be thus taken to several places, to which human art hitherto knew of no conveyance.

55. The philosophical uses, to which these machines may be subservient, are numerous indeed; and it may be sufficient to say, that hardly any thing which passes in the atmosphere is known with precision, and that, principally for want of a method of ascending into it. The formation of rain, of thunder storms, of vapours, hail, snow, and meteors in general, requires to be attentively examined and ascertained. The action of the barometer, the refraction and temperature of the air in various regions, the descent of bodies, the propagation of sound, &c. are subjects which all require a series of observations and experiments, the performance of which could never have been properly expected, before the discovery of ærostatic machines.'

56. Such speculations have been for years on record the reader will see from our preceding detail that they have but partially been fulfilled.

1