296 



Dr. W. Marcet on 



[Apr. 11, 



sprinkled over with, water or snow till tlie air it contained had fallen 

 to that of the salt water in the analysis-tube. An assistant holding 

 up the bag I connected it with the tube, into which the air was drawn 

 by letting out the water from the tube into a bottle. 



When the experiments were made walking the jacket was usually 

 dispensed with ; no account was taken of the carbonic acid in the 

 atmosphere, as I invariably experimented in the open air with the view 

 of obtaining results to be considered comparatively with each other. 

 It is true that M. Truchot * has shown that the proportion of carbonic 

 acid in the atmosphere diminishes as the altitude increases ; the 

 difference, however, with respect to the volume of air breathed is so 

 small as to introduce no substantial error in my inquiry. The tem- 

 perature of the air in the bag immediately after it had been filled, and 

 having its jacket on, was higher than that same air when submitted 

 to analysis. When the difference amounted to more than one or two 

 degrees Fahrenheit, which was nearly always the case, a correction was 

 introduced into the calculation. 



Results. 



The influence of food in increasing the amount of carbonic acid 

 expired is well known. This is clearly shown on the present occasion 

 by placing in a tabular form the quantity of carbonic acid expired (in 

 grammes and grains) at successive hours after a meal. The table in 

 full being too voluminous for the present abstract, I append the means 

 only :— 



Mean Weight of Carbonic Acid expired per Minute. 

















Time after a 



Mean of high 

 altitudes, 

 10,292 feet. 



ber c 

 imen 



Mean 

 tempe- 



Low altitude 



cber c 

 imen 



Mean 

 tempe- 



meal. 



B S 



rature 

 of air. 



1,230 feet. 



s ° 



rature 

 of air. 













co 2 







co 2 









grms. grs. 







grms. grs. 







From to 1 hr. 



0-478 - 7-376 



5 



45-°7 F. 



0-434 - 6-697 



6 



56°'0 F. 



„ 1 to 2 hrs. 



0-455 - 7-021 



10 



48°-l 



0-447 - 6-898 



4 



57°-0 



„ 2 to 3 Hrs. 



0-436 - 6-728 



11 



46°-9 



0-413 - 6 373 



11 



57°-0 



„ 3 to 4 hrs. 



0-440 - 6-790 



5 



46°-7 



0-392 - 6-049 



6 



58°-6 



„ 4 to 6 hrs. 



0-431 - 6-651 

 t 



8 



46°-2 



396 - 6-111 



4 



60°-3 



In the experiments made on the mountains at various elevations, 



* Compte-rendus de l'AcadSmie, vol. lxxvii, 1873. 



f It is interesting to observe that the relation between the highest and lowest 

 means of the high altitudes and low altitude respectively is nearly the same, viz., 

 7-376 : 6-651 = 6-697 : 6-039; the lowest means found for the low altitude was 

 6-049. 



