Balloon Experiments at High Altitudes
In some experiments which have been made in Berlin, it was found that a balloon ascending to a height of five miles found the fierce rays of the sun unbearable without glasses, intense cold caused cramps in the muscles, with absolutely no bacteria in the atmosphere. Between three and four miles there were heavy snow-storms which never reach the earth. Artificial oxygen was required at the height of three miles; the atmosphere contained one fifth of the germs normally found on the earth's surface. The animals taken up in the balloon began to be frightened at the height of two miles, and at the height of five miles were paralyzed.