Page:Encyclopædia Britannica, Ninth Edition, v. 1.djvu/214

Rh 196 AERONAUTICS [SCIENTIFIC The primary object was to determine the temperature of the air, and its hygrometrical state at different elevations to as great a height as could be reached ; and the secondary objects were (1) to determine the temperature of the dew- point by Daniell s and Regnault s hygrometers, as well as by the dry and wet bulb thermometers, and to compare the results; (2) to compare the readings of an aneroid baro meter with those of a mercurial barometer up to the height of 5 miles; (3) to determine the electrical state of the air, (4) the oxygenic condition of the atmosphere, and (5) the time of vibration of a magnet; (6) to collect air at different elevations; (7) to note the height and kind of clouds, their density and thickness; (8) to determine the rate and direc tion of different currents in the atmosphere; and (9) to make observations on sound. The instruments used were mercurial and aneroid baro meters, dry and wet bulb thermometers, Daniell s dew- point hygrometer, Regnault s condensing hygrometer, maximum and minimum thermometers, a magnet for hori zontal vibration, hermetically sealed glass tubes exhausted of air, and an electrometer. In one or two of the ascents a camera was taken up. One end of the car was occupied by the aeronaut; near the other, in front of Mr Glaisher, was placed a board or table, the extremities of which rested on the sides of the car; upon this board was placed suitable framework to carry the several thermometers, hygrometers, magnet, aneroid barometer, &c. ; a perforation through it admitted the lower branch of the mercurial barometer to descend below, leaving the upper branch at a convenient height for observing. A watch was placed directly opposite to Mr Glaisher, the central space being occupied by his note book. The aspirator (for Regnault s hygrometer) was fixed underneath the centre of the board, so as to be con veniently workable by either feet or hands. Holes were cut in the board to admit the passage of the flexible tubes required for Regnault s hygrometer and the dry and wet bulb thermometers. The first ascent was made, as has been stated, from Wolverhampton on July 17, 1862, and the journey was remarkable on account of a warm current that was met with at a great elevation. The weather, previous to the ascent, had been bad for a long time, and it had been delayed in consequence. The wind was still blowing from the west, and considerable difficulty was experienced in the preliminary arrangements, so that no instrument was fixed before starting. The balloon left at 9.43 A.M., and a height of 3800 feet was reached before an observation could be taken. At 4000 feet clouds were entered, and left at 8000 feet. The temperature of the air at starting was 59 Fahr., at 4000 feet it was 45, and it descended to 26 at 10,000 feet, from which height to that of 13,000 feet there was no diminution. While passing through this space Mr Glaisher put on additional clothing, feeling certain that a temperature below zero would be attained before the height of 5 miles was reached; but at the elevation of 15,500 feet the temperature was 31, and at each successive reading, up to 19,500, it increased, and was there 42. The temperature then decreased rapidly, and was 16 at 26,000 feet. On descending it increased regularly to 37 8 at 10,000 feet. A very rough descent, in which nearly 50 worth of instruments were broken, was effected near Oakham, in Rutlandshire, Mr Coxwell having judged it prudent to descend on account of the proximity, as he supposed, of the Wash. In coming down, a cloud was entered at an elevation of 12,400 feet, and proved to be more than 8000 feet in thickness. The rise of temperature met with in this ascent was most remarkable. The weather on the day (Aug. 18, 1862) of the third as sent was favourable, and there was but little wind. All the instruments were fixed before leaving the earth. A height Ascent of more than 4 miles was attained, and the balloon remained froni v in the air about two hours. When at its highest point y 6 ^ there were no clouds between the balloon and the earth, ^g l8 and the streets of Birmingham were distinctly visible. The descent was effected at Solihull, 7 miles from Bir mingham. On the earth the temperature of the air was 67 8, and that of the dew-point 54 6; and they steadily decreased to 39 5 and 22 2 respectively at 11,500 feet. The balloon was then made to descend to the height of about 3000 feet, when both increased to 56 0- and 47 5 respectively. On throAving out ballast the balloon rose again, and the temperature declined pretty steadily to 24 0, and that of the dew-point to- 10 0, at the height of 23,000 feet. During this ascent Mr Glaisher s hands became quite blue, and he experienced a qualmish sensa tion in the brain and stomach, resembling the approach of sea-sickness; but no further inconvenience, besides such as resulted from the cold and the difficulty of breathing, was experienced. This feeling of sickness never occurred again to Mr Glaisher in any subsequent ascent. The ascent from the Crystal Palace on August 20, 1862, Ascent was merely an ordinary one for the public amusement, in froni C which Mr Glaisher took a place in the car. In these low^~ ^ ascents from places of entertainment, in which other per- an( ffr c sons also were passengers, the large board stretching right Kendo across the car could not be used. A smaller frame Augusi was therefore made, which could be screwed on to the edge of the car, to cany the watch, siphon barometer, aneroid barometer, dry and wet bulb thermometers, grid iron thermometer, 1 and Daniell s and Regnault s hygro meters, which comprised all the instruments usually taken up in these low ascents. In the first low ascent, July 30, this framework was fixed inside the car; but as it seemed possible that the warmth proceeding from the voyagers might influence the readings of the instruments, it was always afterwards fixed outside, and projected beyond the car, so that all the instruments were freely exposed to the surrounding air. The ascent on August 20 was a low one, and presented no remarkable feature except that the balloon was nearly becalmed over London. The earth was left at 6.26 P.M., and the air was so quiet that at the height of three-quarters of a mile the balloon was still over the Crystal Palace. At 7h. 47m. it was over London, and moving so slowly that it was thought desirable to ascend above the clouds in hopes of meeting with a more rapid current of air. At Sh. 5m. the voyagers were above the clouds, and it became quite light again, darkness having come on whilst hovering over London, at which time the gradual illumination by the lights in the streets formed a most wonderful sight, and one never to be forgotten. The roar, or rather loud hum, proceeding from the great city was also most remarkable. After having been above the clouds some time, the lowing of cattle and other agri cultural sounds were heard. Accordingly, the valve-line was pulled, and the balloon descended below the clouds, when the light of London was seen in the distance as a misty glare. The darkness increased as the balloon descended very slowly, and it at length touched the ground so gently in the middle of a field at Mill Hill, near Hendon, that those in the car were scarcely aware of the contact. There were twelve voyagers altogether, and when with some trouble sufficient countrymen were collected to take their places and enable 1 This was a thermometer with a bulb shaped like a gridiron, so aa to have a very great surface exposed to the air. It was thought that the ordinary pea-sized bulb would not permit of the thermometer being- sufficiently delicate to register the rapid changes of temperature due to the quick motion of the balloon, as it requires some little time for such a thermometer to take up the temperature of the surrounding medium.