306 EXPLORATIONS OF THE UPPER ATMOSPHERE. 



millimeters of mercury, which corresponds to a height of 13,843 meters, 

 according to the formula of Laplace. Theu, after a period of equi- 

 librium lasting three hours, the descent commenced, slow at first, then 

 more and more rapid, until it attained a velocity of 3 meters per sec- 

 ond at landing, 4.30 p. m. 



The thermometric diagram showed a regular decrease of temperature, 

 which reached —50° C. at the moment when the descent commenced. 

 But this record, which does not agree with those obtained in preceding 

 experiments, appears somewhat uncertain, and M. Hermite thinks that 

 it may have been falsified by various more or less hypothetical causes — 

 for example, the insufficient ventilation of the apparatus. 



A registering thermometer had been inclosed, as we have said, in 

 the interior of the balloon. An examination of the tracing obtained 

 showed that the temperature of the gas was about 30° C. during the 

 inflation, while the temperature outside was only 18°. But as soon as 

 the ascent commenced the carbureted hydrogen naturally expanded 

 with great rapidity, and the temperature of the gas fell to — 21°, a 

 result to-day well understood. The balloon forms a gigantic actinom- 

 eter, which shows the effects of solar radiation, and the intensity of 

 that radiation increases with the altitude, and is in inverse proportion 

 to the density of the air. 



The apparatus for taking in air appeared to have worked according 

 to the conditions that M. Oailletet had foreseen, and M. Hermite 

 brought it back intact, its orifices hermetically closed, to Paris, where 

 M. Muntz, director of the Laboratory of Agricultural Chemistry, was 

 to analyze it. But as the vacations were about to commence he could 

 not take up this analysis until some months later — in October, and it 

 was then found that, during this long interval, the air in the receiver 

 had resumed its normal pressure. There had therefore been a leakage, 

 and the experiment would have to be repeated. 



It has been found possible to reconstruct the trajectory of the aero- 

 stat from the time of its departure by using the diagrams furnished by 

 the dromograph and the barometric curve. We thus have on the one 

 hand the azimuth of the balloon at every moment, and on the other the 

 angle a, whose value represents the height of the balloon. The sine of 

 the angle a is furnished by the barometric curve, using the formula of 

 Laplace 5 a quite simple trigonometric operation then suffices to resolve 

 the right-angled triangle. In this way also it has been possible to 

 determine the velocity of the currents which transported the Aerophile 

 at different altitudes. This velocity was as follows : 



38 kilometers per hour between 3,000 and 5,000 meters. 



70 kilometers per hour between 5,000 and 6,200 



80 kilometers per hour between 6,200 and 7,000 

 102 kilometers per hour between 7,000 and 7,700 

 132 kilometers per hour between 7,700 and 8,200 

 158 kilometers per hour between 8,200 and 9,700 



