Decreased Pressure 963 



nomena already observed in the cylinders of my laboratory were 

 reproduced with a certainty that, under the dramatic circumstances, 

 was very striking and inspired in the two aeronauts a reckless con- 

 fidence, which proved fatal to them. 



April 15, 1875, they began another ascent to great heights, taking 

 with them M. Gaston Tissandier. To the ring of the balloon were 

 fastened three gas bags filled with a mixture of 72% of oxygen. 

 These gas bags, I can say today, were quite insufficient in capacity. 

 I was then absent from Paris, and warned by a letter from Croce- 

 Spinelli of their coming expedition, a letter in which he specified 

 the quantity of oxygen which they were going to take with them 

 (it was to be, I think, 150 liters) , I warned him of its insufficiency. 

 "In the lofty elevations where this artificial respiration will be 

 indispensable to you," I said to him, "for three men you should 

 count on a consumption of at least 20 liters per minute; see how 

 soon your supply will be exhausted!" My letter arrived too late, it 

 seems; the day of the ascension was set, and they drew from my 

 observations only this conclusion which was so fatal, that they 

 should wait for absolute necessity to make use of the gas bags. We 

 know what happened; when the aeronauts, feeling asphyxia over- 

 come them, tried to seize the life-giving tubes, their arms were 

 paralyzed. 



M. Gaston Tissandier, the only survivor of the Zenith catas- 

 trophe, wrote 14 a powerful account of it from which I shall borrow 

 freely: 



Thursday, April 15, 1875, at 11:35 in the morning, the balloon 

 Zenith rose from the ground at the gas works of La Villette. Croce- 

 Spinelli, Sivel, and I had taken our places in the basket. Three gas 

 bags filled with a mixture of air with 70% of oxygen were fastened to 

 the ring. At the lower end of each of them, a rubber tube passed 

 through a wash-bottle filled with an aromatic liquid. This appara- 

 tus, in the upper regions of the atmosphere, was to furnish to the 

 travellers the oxygen necessary to maintain life. An aspirator bottle 

 filled with petrol, which the low temperature cannot solidify, was 

 hung outside the basket; it was to be suspended vertically at a height 

 of 3000 meters to force air into the potash tubes intended for the 

 determinations of the carbonic acid .... 



We start, we rise in the midst of a flood of light, emblem of joy, 

 of hope! 



Three hours after the departure, Sivel and Croce-Spinelli were 

 inanimate in the basket! At 8000 meters altitude, asphyxia had struck 

 with death these disciples of science and truth! 



It is for their travelling companion, who miraculously escaped 

 death, to close his heart to grief for a moment, to drive away sad 

 memories and gloomy visions, so that he can report the data gathered 



