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, experiencing the same symptoms, and deriving the same benefit from the use of oxygen: these are Messrs. Crocé-Spinelli and Sivel. Crocé, 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 effect 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, Crocé-Spinelli and Sivel made their ascension of March 22, 1874, during which they rose to the height of 7,500 metres (a pressure of 30 centimetres). The faintness, the disordered 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 company 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 probably 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. Crocé-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 which 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 aërial 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 decompression. The experiments made in the cylinders demonstrate, beyond the possibility of doubt, that these symptoms depend solely on the tension of the oxygen in the air respired; an aëronaut 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
