324 THE POPULAR SCIENCE MONTHLY. 



who were watching me through glass peep-holes, would not work, and 

 so I had to return to normal pressure, I placed, for a moment, the 

 oxygen-tube under the beak of the bird, and at once he recovered. 



Two other persons have, like myself, entered these cylinders, ex- 

 periencing the same symptoms, and deriving the same benefit from 

 the use of oxygen : these are Messrs. Croce-Spinelli and Sivel, Croce, 

 who was very sensitive to reduced pressure, had turned black at the 

 lips and on the ears, and could hardly see his paper, when he decided 

 to have recourse to the oxygen. The efiect was instantaneous, both 

 upon him, who at once was able to write, and upon me, who observed 

 with some anxiety the purple color of his ear, and was about to let 

 in air. 



Fresh from these experiments, Croce-Spinelli and Sivel made their 

 ascension of March 22, 18V4, during which they rose to the height of 

 7,500 metres (a pressure of 30 centimetres). The faintness, the dis- 

 ordered vision, and the nausea, disappeared every time they "drank a 

 little oxygen," as Sivel would say. 



On the 15th of April, 1875, they made another ascension, in com- 

 pany with Gaston Tissandier. I was not then in Paris, and hence 

 could not, as on the former occasion, superintend the making of the 

 oxygen-bags. I would surely have made them larger, but prob- 

 ably I should no more than any of you have dreamed of what was 

 the true cause of the catastrophe which followed. The oxygen-tube 

 hung at a certain height above their heads, and, knowing that they 

 had but very little of that gaseous cordial, they economized it against 

 the moment when they should be more seriously attacked by 

 sickness. But, when they wanted to take hold of the tube and to 

 apply it to their mouths, their arms were paralyzed. 



This terrible occurrence ought to be a lesson of prudence, but it 

 must not serve as a pretext for discouragement. Croce-Spinelli and 

 Sivel died at 8,600 metres, with a pressure no greater than that reached 

 by me without the slightest shadow of unfavorable symptoms, and it 

 will be easy to devise measures whicb will insure the aeronaut against 

 an attack of sudden paralysis. As for the value of ascensions to great 

 heights, I am surprised to see it questioned by eminent men. What 

 could be a more curious object of inquiry, from the point of view of 

 the meteorologist, than that aerial zone, 10 or 12 kilometres in depth, 

 in which are developed rain, hail, and snow storms ? It is not wise to 

 assign limits either to human activity or to the usefulness of scientific 

 researches. 



But to return to the theory of the symptoms produced by decom- 

 pressioti. The experiments made in the cylinders demonstrate, be- 

 yond the possibility of doubt, that these symptoms depend solely on 

 the tension of the oxygen in the air respired ; an aeronaut breathing 

 common air (21 per cent, oxygen) at one-half common atmospheric 

 pressure is precisely in the same condition as a man who, at normal 



