Wonderful Balloon Ascents/Part 3/Chapter 1
EXPERIMENTS OF ROBERTSON, LHOEST, SACCAROF, &C.
Robertson is regarded by many as a sort of mountebank; yet such men as Arago have put themselves to the trouble of examining the aerostatic feats of this aeronaut, and of examining the results of his observations.
"The savant Robertson," says Arago, "performed at Hamburg on the 18th of July, 1803, with his countryman, Lhoest, the first aeronautic voyage from which science has been able to draw useful deductions. The two aeronauts remained suspended in the air during five hours, and came down near Hanover, twenty-five leagues from the spot from which they set off."
The first time that Robertson appears in the annals of aerostation is in 1802, on the occasion of the sale of the balloon used at the battle of Fleurus, of which mention will be made in the chapter on military aerostation. But three years previously he had been instructed to make a balloon of an original form, which should ascend in honour of the Turkish ambassador at the garden of Tivoli. The fête was completely successful. Turks, Chinese, Persians, and Bedouins will always be welcome, as on this occasion, at Paris, appearing as they do only at rare intervals, and for a short time.
The fête took place on the 2nd of July. Robertson presented himself at the house of Esseid-Ali, to obtain his autograph. The Turkish ambassador willingly granted the request, and wrote his name in letters, each of which was two inches in height, on a sheet of paper. He then offered the aeronaut coffee and comfits, and promised to be present to witness the balloon ascent. His name was painted in large characters on a balloon fifteen feet in diameter, and on the form of which was the figure of a crescent. The experiment delighted the ambassador, and was well received by the public.
Jacques Garnerin, when he came to make his débût as an aeronaut, made an attempt with the parachute, the following August, at the garden of the Hotel de Biron. The ambassador was asked to honour the fête, but he declined, saying that he had "made up his mind that man was not intended for flying—Mahomet had not so willed it."
Of one of Robertson's more interesting ascents he himself has left us the following sketch:—
"I rose in the balloon at nine a.m., accompanied by my fellow-student and countryman, M. Lhoest. We had 140 lbs. of ballast. The barometer marked twenty-eight inches; the thermometer sixteen degrees Reaumur. In spite of some slight wind from the north-west, the balloon mounted so perpendicularly that in all the streets each of the spectators believed we were mounting straight up above his head. In order to quicken our ascent I discharged a parachute made of silk, and weighted in a way to prevent oscillations. The parachute descended at the rate of two feet per second, and its descent was uniform. From the moment when the barometer began to sink we became very careful of our ballast, as we wished to test from experience the different temperatures through which we were about to pass.
"At 10.15, the barometer was at nineteen inches, and the thermometer at three above zero. We now felt all the inconvenience of an extremely rarefied atmosphere coming upon us, and we commenced to arrange some experiments in atmospheric electricity. Our first attempts did not succeed. We threw over part of our ballast, and mounted up till the cold and the rarefaction of the air became very troublesome. During our experiments we experienced an illness throughout our whole system. Buzzing in the ears commenced, and went on increasing. The pain we felt was like that which one feels when he plunges his head in water. Our chests seemed to be dilated, and failed in elasticity. My pulse was quickened, M. Lhoest's became slower; he had, like me, swelled lips and bleeding eyes; the veins seemed to come out more strongly on the hands. The blood ran to the head, and occasioned a feeling as if our hats were too tight. The thermometer continued to descend, and, as we ascended, our illness increased, and we could with difficulty keep awake. Fearing that my travelling companion might go to sleep, I attached a cord to my thigh and to his, and we held the extremities of the cord in our hands. Thus trammelled, we had to commence the experiments which I had proposed to make.
"At this elevation, the glass, the brimstone, and the Spanish wax were not electrified in a manner to show any signs under friction—at least, I obtained no electricity from the conductors or the electrometer. "I had in my car a voltaic pile, consisting of sixty couples—silver and zinc. It worked very well on the occasion of our departure from the earth, and gave, without the condenser, one degree to the electrometer. At our great elevation, the pile gave only five-sixths of a degree to the same electrometer. The galvanic flame seemed more active at this elevation than on the earth.
"I took two birds with me on coming into the balloon—one of these was now dead, the other appeared stupefied. After having placed it upon the brink of the gondola, I tried to frighten it to make it take to flight. It moved its wings, but did not leave the spot; then I left it to itself, and it fell perpendicularly and with great rapidity. Birds are certainly not able to maintain themselves at such elevations.
"It is notable that the atmosphere, which was of a perfect purity near the earth, was grey and misty above our heads, and the beautiful blue sky seen from the surface did not exist for us, although the weather was calm and serene, and the day the most beautiful that could be. The sun did not seem dazzling to us, and its heat was diminished owing to our elevation.
"At half-past eleven, the balloon was no longer visible from Hamburg. The heavens were so pure beneath us that everything was distinctly seen by us, though very much diminished by distance. At 11.40, the town of Hamburg seemed only a red point in our eyes; the Elbe looked like a straight ribbon. I wished to make use of an opera-glass, but what surprised me was that when I lifted it up it was so cold that I had to wrap my handkerchief around it to enable me to hold it.
"Not being able to support our position any longer, we descended, after having used up much gas and ballast. Our descent caused that degree of terror among the inhabitants which the size of our balloon was calculated to inspire in a country where such machines had never before been seen. We descended above a poor village called Radenburg, a place amid the heaths of Hanover. Our appearance caused great alarm, and even the beasts of the field fled from us.
"While our balloon rapidly approached the earth, we waved our hats and flags, and shouted to the inhabitants, but our voices only increased their terror. The villagers rushed away with cries of terror, leaving their herds, whose bellowings increased the general alarm. When the balloon touched the ground, every man had shut himself up in his own house. Having appealed in vain, and fearing that the villagers might do us some injury, we resolved to re-ascend.
"In making this second ascent, we threw over all our ballast; but in this we were imprudent, for after sailing about at a great height, and having lost much gas, I perceived that our descent would be very rapid, and to provide against accident, I gathered together all the instruments, the bread, the ropes, and even such money as we had with us, and placed them in three sacks, to which I attached a rope of a hundred feet in length. This precaution saved us a shock. The weight, amounting to thirty pounds, reached the ground before us, and the balloon, thus lightened, came softly to the ground between Wichtenbech and Hanover, after having run twenty-five leagues in five and a half hours."
After this ascent Robertson became acquainted with some savants of Hamburg, and amongst others with Professor Pfaff, who was interested in aerial travelling as a means of settling certain meteorological problems. Some days after Robertson's ascent, the professor wrote to him— "You speak of a certain height at which the hydrogen gas will find itself in equilibrium in the air of the atmosphere. I believe that this height is the extremity of the atmosphere itself; for as the gas has an elasticity much greater than that of the air, it will go on dilating as it mounts into the higher regions of the atmosphere, and its specific weight will diminish as the weight of atmospheric air diminishes; and it will not cease to mount until it rises above the atmosphere itself, if two conditions be completely fulfilled—1, the condition that the gas may be allowed to dilate without leaving the balloon as it rises; 2, the condition that the gas shall not be allowed to mix at all with the atmospheric air."
Another ascent was arranged for the 14th of August, in which Robertson was to be accompanied by the professor, but the latter, yielding to the entreaties of his family, did not go. "I went up with my friend Lhoest," says Robertson, "at forty-two minutes past twelve midday. In a minute or two we rose up between two masses of cloud, which seemed to open up and offer us a passage. The upper surfaces of these clouds are not uniformly level, like the under sides seen from the earth, but they are of a conical or pyramidal shape. These imposing masses seem to precipitate themselves upon the earth, as if to engulf it, but this optical illusion was due to the apparent immobility of the balloon, which at the moment was rising at the rate of about twenty feet per second.
"The fear of losing the view of the Baltic, which we perceived between the clouds at intervals, obliged us to renounce the project of rising as high as on the last occasion. The barometer was at fifteen inches, and the thermometer one degree below zero, when I let off two pigeons. One descended in a diagonal direction, its wings half open but not moving, with a swiftness which seemed that of a fall. The other flew for an instant, and then placed itself upon the car, and did not wish to quit us. Acting on the hint of Dr. Reimarus, I tried the same experiment with butterflies, but the air was too much rarefied for them; they attempted in vain to raise themselves by their wings, but they did not forsake the car.
"The wind continuing to carry me towards the sea, I resolved to bring my observations to an end. I effected my descent in a meadow, near the village of Rehorst, in Holstein, after having run sixteen leagues from France in sixty-five minutes."
At the commencement of the year 1804, Laplace, at the Institute, proposed to take advantage of the means offered by aerostation to verify at great heights certain scientific points—as, for example, those which concern magnetism. This proposition was made at a favourable time, and was, so far, carried out in the best possible way. The aeronauts who were appointed to carry out the expedition were Biot and Gay-Lussac, the most enthusiastic aeronauts of the period.
The following is their report:—
"We observed the animals we had with us at all the different heights, and they did not appear to suffer in any manner. For ourselves, we perceived no effect any more then a quickening of the pulse. At 10,000 feet above the ground we set a little green-finch at liberty. He flew out at once, but immediately returning, settled upon our cordage; afterwards, setting out again, he flew to the earth, describing a very tortuous line in his passage. We followed him with our eyes till he was lost in the clouds. A pigeon, which we set free at the same elevation, presented a very curious spectacle. Placed at liberty on the edge of the car, he remained at rest for a number of instants, as if measuring the length of his flight; then he launched himself into space, flying about irregularly, as if to try his wings. Afterwards he began his descent regularly, sweeping round and round in great circles, ever reaching lower, until he also was lost in the clouds."
As to the voyagers themselves, this is how they speak of their situation at the height of 3,000 yards:—
"About this elevation we observed our animals. They did not appear to suffer from the rarity of the air, yet the barometer was at twenty inches eight lines.. We were much surprised that we did not suffer from the cold; on the contrary, the sun warmed us much. We had thrown aside the gloves which had been put on board, and which were of no use to us. Our pulses were very quick; that of M. Gay-Lussac, which is 62 in the minute on ordinary occasions, now gave 80; and mine, which is ordinarily 89, gave 111. This acceleration was felt by both of us in nearly the same proportion. Nevertheless, our respiration was in no way interfered with, we experienced no illness, and our situation seemed to us extremely agreeable."
The following is their report to the Galvanic Society:—
"We have known for a long time that no animal can with safety pass into an atmosphere much more dense or much more rare than that to which it has been accustomed. In the first case it suffers from the outer air, which presses upon it severely; in the second case there are liquids or fluids in the animal's body which, being less pressed against than they should be, become dilated, and press against their coverings or channels. In both cases the symptoms are nearly the same—pain, general illness, buzzing in the ears, and even haemorrhage. The experience of the diving-bell has long made us familiar with what aeronauts suffer. Our colleague (Robertson), and his companion, have experienced these effects in great intensity. They had swelled lips, their eyes bled, their veins were dilated, and, what is very remarkable, they both preserved a brown or red tinge which astonished those that had seen them before they made the ascent. This distension of the blood-vessels would necessarily produce an inconvenience and a difficulty in the muscular action."