420 



Dr. W. Marcet. 



[Feb. 10, 



our residence during our stay at that place. The experiments were 

 repeated at Y voire near the Lake of Geneva (altitude 1,230 feet), and 

 at Courmayeur (3,945 feet) at the foot of the Col du Geant on the 

 Italian side. Hence, there were three series of data obtained in the 

 course of about three months on two persons in good health, though very 

 different in age, weight, and other respects. Two sets of experiments 

 were made at Courmayeur, the first before ascending to the Col du 

 Geant, and the second on our return ; the object being to ascertain 

 whether the influence of the sojourn at the higher station showed itself 

 on our breathing for some time after we had left it. The experiments 

 were invariably made in the sitting posture, and in the open air, away 

 from every possible source of contamination with carbonic acid, and 

 care was taken to remain perfectly quiet for a short time before collect- 

 ing the air expired. 



With the object of determining the amount of air expired within 

 a given time, and the carbonic acid it contained, breathing was carried 

 on through a face-piece connected with the india-rubber bag, and 

 adapting itself perfectly over the mouth and nose ; the face-piece was 

 supplied with valves, so that fresh air was taken in at each inspiration, 

 while the expired air was collected in the bag. A water gauge, 

 communicating with the bag by india-rubber tubing, showed the pres- 

 sure of the air it contained, and the bag was taken as full when the 

 gauge exhibited a pressure of one inch. By means of a stop-watch 

 registering minutes and seconds only, the time for filling the bag, and, 

 therefore, for expiring 320 cubic feet or 90'6 litres of air, was accurately 

 measured. 



Immediately after the bag had been filled with air from the lungs, 

 it was joined by india-rubber tubing with a cylinder made of very 

 thick glass, and holding exactly two litres, which was placed in an 

 upright position on a tripod stand. After exhausting the cylinder 

 with an air pump, air was let into it from the bag, the operation being 

 repeated, thereby ensuring that two litres of air had been withdrawn 

 into the cylinder for analysis. Before closing the stop-cock and sever- 

 ing the connexion between the bag and cylinder a minute or two were 

 allowed to elapse, and then the temperature of the air in the bag and 

 in the cylinder was read off and noted. Care was taken to observe 

 these temperatures while the bag and cylinder were communicating 

 freely with each other, so as to allow of the equilibrium of pressure 

 being established, should there be any difference between the tempera- 

 ture of the air in the bag and in the cylinder; sometimes the tempera- 

 ture was the same, but it frequently happened that the readings 

 differed by 1° or 2°, the difference very seldom reaching 3° or 4°. A 

 titered solution of baric hydrate was then introduced into the cylinder 

 by a process described in a communication to the Chemical Society ;■* 

 * " Journal of the Chemical Society," July, 1880. 



