October 21, 1897] 



NATURE 



60' 



about 100 pounds (Science, November 13, 1896, p. 718). The 

 meteorograph remained durintj several hours higher than a mile, 

 and good records of the indications of the barometer, thermo- 

 meter, and hygrometer were brought down. More than one 

 hundred records of atmospheric pressure, temperature, and 

 relative humidity of the air, or wind velocity, at intermediate 

 heights up to the extreme altitude just stated, have been 

 obtained, and they are being discussed for publication with the 

 Blue Hill observations for 1896, in the " Annals of the Astro- 

 nomical Observatory of Harvard College." A few general 

 conclusions may be mentioned. At the height of about a mile 

 the diurnal changes of temperature in the free air nearly dis- 

 appear, although in fair weather the days are damper than the 

 nights. " Cold and warm waves" commence in the upper air, 

 as is proved by the temperature decreasing faster than normal, 

 or even increasing abruptly, with altitude before the fall or rise 

 of temperature commences at the earth's surface. Several 

 ascents through clouds have shown the air above them to be 

 usually warmer and drier than the air below. Kites furnish a 

 ready and accurate method of measuring the heights of certain 

 low and uniform clouds, which could not easily be measured 

 otherwise in the day-time. It is interesting to note that this 

 method was used by Espy, about 1840, to verify his calculations 

 of the height at which condensation liegins (" Philosophy of 

 Storms," 1841, p. 75). Changes of wind direction in the 

 different air strata are determined from the azimuths of the 

 kites, and this change sometimes amounts to 180°. The wind 

 velocity usually increases with altitude, and vertical currents 

 commonly prevail near cumulus clouds. During high flights the 

 wire is strongly charged with electricity, but no measurements 

 of its kind or potential have lately been attempted. 



The writer is glad to acknowledge his indebtedness to his 

 assistants, Messrs. Clayton and Fergusson, who have devised 

 and constructed improved kites and apparatus, and during his 

 absence have taken entire charge of the work. To them and 

 to another assistant, Mr. Sweetland, is largely due the succe.ss 

 which has been attained in this novel branch of research. For 

 still higher ascents there will be required a steam engine to 

 operate the windlass, and a meteorograph with a lower pressure 

 scale. With these appliances, for whose purchase a grant has 

 been asked from the Hodgkins Fund "of the Smithsonian 

 Institution, it is probable that records can be obtained three 

 miles above Blue Hill, and possibly higher. 



To reach much higher altitudes, unmanned free balloons, or 

 "ballons sondes" as they are called, have been considerably 

 used both in France and Germany. These balloons, which 

 carry self-recording apparatus, rise until equilibrium is attained 

 in the rarefied air. When they lose their buoyancy and fall 

 to the earth, most of them have been recovered, with the 

 instruments and records uninjured, by the senders, who have 

 been notified by the finder of the place of descent, which is often 

 at a great distance from the starting point. The altitudes 

 are calculated from the barometric pressure, according to 

 Laplace's formula, but the impossibility of knowing the mean 

 temperature of the whole mass of air makes the determination 

 inexact. Theoretically, in order to ascend ten miles above the 

 earth, where the pressure is about one-ninth that at the earth, 

 the balloon must lift itself from the ground when one- ninth 

 filled with gas. Therefore a relatively large balloon is required, 

 and its initial velocity of ascent is great, because it is found 

 advantageous to fill the gas-bag completely. The greatest 

 difficulty has been to protect the thermometers from insolation, 

 and to ensure records being made, notwithstanding the great 

 cold to which the instruments are exposed. 



The first systematic experiments of the kind were made in 

 Paris, in 1893, by (1. Ilermite, who was later associated with G. 

 Besan^on. There have been six high ascents from Paris of the 

 three balloons called V Aerophtk. The second one of the name 

 had an envelope of gold-beaters' skin, with a capacity of 6360 

 cubic feet, which when nearly filled with coal-gas gave an initial 

 lifting power of 235 pounds, in excess of its own weight of 49 

 pounds, and the instruments and screens, which weighed 12 

 pounds. With this balloon, in October 1895, at an approximate 

 height of 46,ocx3 feet, a temperature of - 94° Fahrenheit was 

 recorded, which is the lowest noted in a balloon, and probably 

 the lowest natural temperature observed Jon the earth. The 

 average decrease of temperature was 1° Fahrenheit for 320 feet 

 of height. The instruments used are of the well-known Richard 

 type, and have been tested in a chamber whose pressure and 

 temperature are lowered to the limits which it is expected may be 

 reached by the balloon. They are placed below the balloon in 



NO. 1460, VOL. 56] 



a wicker tube six feet high, lined with silver paper to ward off 

 the sun's rays. It is believed by Ilermite, that during the rapid 

 ascent of the balloon the draught of air through the tube is 

 sufficient to neutralise the heating of the enclosed air by the sun. 

 It is admitted that when equilibrium is nearly reached this may 

 not be true, and that the temperature recorded near the highest 

 point may be too high. To avoid freezing of the ink the 

 registration is now made on smoked paper, and to protect the 

 instrument from shocks it is hung by springs in a closed basket, 

 which is itself susjiended in the tube already mentioned. An 

 apparatus for obtaining samples of air at high altitudes has been 

 carried by the balloon, but as yet without success, owing to 

 difficulties in hermetically closing the receiver after the air has 

 entered, since mechanically closing the inlet tube and sealing it 

 by heat generated chemically have each proved ineffectual at 

 great heights. 



By means of a grant from the German Emperor to the 

 Deutsche Verein zur Forderung der Luftschiffahrt, R. Assmann, 

 A. Berson, and others in Berlin, have been able to carry on an 

 extensive series of meteorological investigations with manned 

 balloons, and also with a captive and a free balloon, both 

 equipped with self-recording instruments. The latter, called 

 the Cirrus, of 8830 cubic feet capacity, when inflated with coal- 

 gas had a lifting force of about 290 pounds, besides its envelope 

 weighing 93 pounds, and the meteorological apparatus weighing 

 nearly 6 pounds. This is more complicated than the French 

 instruments, since the registration is photographic, and a con- 

 tinuous ventilation of the alcohol thermometer in Assmann's 

 aspiration apparatus is effected by allowing a weight to drive 

 the aspirator. Even with these precautions, the temperatures 

 are probably too high, and the registration is often defective. 

 There have been seven flights of the Cirrus, one of the highest 

 occurring in September 1894, when the unprecedentedly low 

 barometric pressure of about two inches of mercury was recorded, 

 giving a computed height of 60,500 feet. The lowest tempera- 

 ture, which was registered at a somewhat less altitude, was not 

 below - 88° Fahrenheit, giving rise to the supposition that the 

 thermometer was heated by insolation Hence the average 

 decrease of temperature appears to have been but 1° in 409 feet. 

 This balloon rose from Berlin with the great velocity of about 

 30 feet per second, and travelled 560 miles in an east-north-east 

 direction at a velocity of 83 miles per hour. 



For some time past negotiations have been in progress between 

 the French and the Germans for simultaneous ascents of un- 

 manned balloons at night, using identical instruments, whereby 

 the errors due to insolation, and the discrepancies which might 

 be attributed to different instruments, would be avoided. By this 

 co-operation the simultaneous conditions of the upper air over a 

 wide extent of country can be ascertained, just as these cop- 

 ditions near the earth's surface are daily obtained at the meteor- 

 ological stations in the different countries. The desired result 

 was brought about by the International Meteorological Con- 

 ference which met in Paris in September 1896. Resolutions were 

 adopted favouring scientific ascents with manned balloons, as 

 well as simultaneous flights of unmanned registration balloons 

 in the different countries. The successful use of kites at Blue 

 Hill to lift self-recording instruments over a mile into the air, 

 led to expressed desire that .similar experiments should be tried 

 elsewhere. An international committee was appointed to carry 

 out these resolutions, consisting of Messrs. de Fonvielle and 

 Hermite for France ; Assmann, Erk, and Hergesel for Germany ; 

 Pomortzeff for Russia ; and the writer for the United States. In 

 accordance with the first-named resolutions, a flight of four 

 manned and four registration balloons occurred in France, 

 Germany, and Russia on the night of November 13-14, 1896. 

 Owing to hurried preparations, only the registration balloon 

 liberated from Paris reached a great height ; but in presenting 

 a summary of the results to the French Academy (Compies 

 rendus, vol. cxxiii. No. 22, pp. 918, 961), E. Mascart, the 

 director of the French Meteorological Office, remarks»that there 

 is reason to hope that this international co-operation will con- 

 tribute valuable data to our knowledge of the variations of 

 temperature and wind in the upper atmosphere. 



As the American representative of the International Aero- 

 nautical Committee, the writer hopes that in America a 

 similar exploration of the high atmosphere with registration 

 balloons will be attempted, and he is now preparing an estimate 

 of the cost to submit to the Trustee of the Hodgkins Fund. 

 Since it should supplement his own researches with kites, he has 

 taken the occasion to bring the subject of free registration 

 balloons to the attention of the Academy. 



