612 



the carbonic acid and vapour from the expired air. The former is a 

 small dry gas-meter, of improved manufacture, and the latter con- 

 sists of 1 st, a desiccator of sulphuric acid to absorb the vapour ; 

 2nd, a gutta-percha box, with chambers and cells, containing caustic 

 potash, and offering a superficies of 700 inches, over which the 

 expired air is passed, and by which the carbonic acid is abstracted ; 

 and 3rd, a second desiccator to retain the vapour which the expired 

 air had carried off from the potash box. A small mask is worn, so as 

 to prevent any air entering the lungs without first passing through the 

 spirometer, and the increase in the weight of this with the connect- 

 ing tube and the first desiccator gives the amount of vapour exhaled, 

 whilst the addition to the weight of the potash box and the second 

 desiccator gives the weight of the carbonic acid expired. The ba- 

 lances employed weigh to the y^- of a grain, with 7 Ibs. in the pan. 

 By this apparatus the whole of the carbonic acid was abstracted 

 during the act of expiration, and the experiment could be repeated 

 every few minutes, or continued for any number of hours, and be 

 made whilst sleeping and with certain kinds of exertion. 



The amount of carbonic acid expired in the twenty-four hours was 

 determined by several sets of experiments. Four of these, consisting 

 of eight experiments, were made upon four gentlemen, on the author, 

 Professor Frankland, F.R.S., Dr. Murie, and Mr. Moul, during the 

 eighteen hours of the working day. In two of them, the whole of 

 the carbonic acid was collected, and in two others the experiment 

 was made during ten minutes at the commencement of each hour, 

 and of each hour after the meals. The quantity of carbonic acid 

 varied from an average of 24'274 oz. in the author to 16*43 oz. in 

 Professor Frankland. The quantity evolved in light sleep was 4 '88 

 and 4'99 grains per minute, and when scarcely awake 5 '7, 5*94, and 

 6'1 grains at different times of the night. The author estimates the 

 amount in profound sleep at 4*5 grains per minute ; and the whole 

 evolved in the six hours of the night at 1950 grains. Hence the total 

 quantity of carbon evolved in the twenty-four hours, at rest, was, in 

 the author, 7' 144 oz. The effect of walking at various speeds is then 

 given, with an estimate of the amount of exertion made by different 

 classes of the community, and of the carbon which would be evolved 

 with that exertion. 



The author then states the quantity of air inspired in the working 



