312 EXPLORATIONS OF THE UPPER ATMOSPHERE. 



ill obtaining, by means of the automatic apparatus devised by-M. 

 Heimite, in conjunction with M. Cailletet, member of the institute, the 

 air of unknown regions where respiration can not be supported; an 

 experiment that, as we have above stated, had hitherto failed. The 

 arrangement of this apparatus was as follows: 



The air reservoir, cylindrical in form, is of red copper, tinned within 

 so as to close all fissures and blowholes that might exist in the metal. 

 The tinning has no effect upon the gas imprisoned in the upper atmos- 

 phere, and has the advantage of assuring the complete impermeability 

 of the reservoir. Glass would not have answered because of its fragility 

 and the difficulty of attaching the necessary tubing. 



This receiver, holding about 6 liters, communicates with a tight cock 

 Inclosed in a special box formed by a coil of red co[)per; an ingenious 

 arrangement that obviates, by its elasticity, the ruiDture of the joints 

 from violent shock. 



The box that contains the cock, the essential and delicate organ of 

 this apparatus, is lined inside with felt 2 centimeters thick, surrounding 

 another receptacle of tin filled with acetate of sodium, and within this 

 is the cock that opens and closes the pipe allowing ingress of air. The 

 outer envelope of this cock turns very slowly upon itself, driven by 

 powerful clockwork also set in the receptacle containing the acetate. A 

 needle attached to this cock turns about a graduated dial, and allows 

 one to set the time for opening the cock, which, having a hole 1 millimeter 

 in diameter, remains open for four minutes only. A tube that extends 

 for 2 meters below the apparatus serves to admit the external air to the 

 receiver, in which, it is of course understood, a vacuum has been formed 

 by means of an air pump. Before sending it off the entire apparatus 

 was inclosed in a loose wicker case filled with straw, to protect it against 

 the shock of descent. Its total weight was about 11.5 kilograms. 



It was only with very great diiUculty, after repeated attempts and 

 patient studies, that MM. Cailletet and Hermite attained this result of 

 an absolutely tight cock maintaining a perfect vacuum. 



This cock was constructed by MM. Ducretet & Co. The conduit for 

 ingress of air passing to the reservoir is a canal, hollowed obliquely 

 out of the axis of the movable piece of the cock, so as to end at two 

 points situated at different heights, corresponding to the intake of the 

 air and to its discharge into the reservoir. Thanks to this arrange- 

 ment, the leakage that generally occurs through the circular and 

 almost invisible grooves that result from the wear of metallic pieces 

 upon each other is avoided. In the arrangement adopted these 

 grooves, so difficult to prevent, no longer correspond to the orifices of 

 ingress and egress, and the apparatus may retain its vacuum indefi- 

 nitely. 



The fixed bronze piece in which the key of the cock moves has the 

 form of a sewing thimble, as in the apparatus of M. Carre intended 

 for producing cold. 



