of Respiration at different Periods of the Day. -ill 



47^ Fahrenheit when the bai'ometer stands at 30 inches; we 

 demonstrate the constituents of 100 parts of air which had 

 passed through the kings for this test experiment to be 

 16-79 parts oxygen. 

 3*68 do. carbonic acid gas. 



1'23 do. aqueous vapour at 4-7° Fahr.; barom. 29'5 in. 

 78-35 do. nitrogen, (being the ordinary quantity in 100 



parts of air that contain 1 '23 parts 



100*05 of aq. vap.) 



Consequently there was no error in the abstraction of the 

 carbonic acid. 



Feb. 19. Air respired into a bag, at 9,] a.m. 



110-5 parts, became 105*5 .•. 4-52 per cent. loss. 



124<*33 do. do. 119*33 .*. 4*02 do. 



2)8*54. 

 .*. average loss = 4*27 per cent, 

 which, corrected for tension, will be 4*38 per cent. 



100 parts taken from the same bag over mercury. Baro- 

 meter at 29*5 inches, and temperature 47° Fahrenheit. 



At 11 a.m. a piece of caustic potassa was introduced, and 

 after a lapse of 61 hours it was abstracted. 



5 parts had been absorbed, the thermometer being 

 47° Fahrenheit, and the barometer standing at 29*65 inches. 

 The residue 



95 parts ; barometer at 29*65 inches, are equal to 



95*48 do. do. at 29*5 inches, 

 consequently, only 4*52 parts of the original quantity had 

 been absorbed, which will include both the carbonic acid gas 

 and the aqueous vapour. Now as the aqueous vapour at this 

 temperature and pressure would be 1*23 per cent, there will 

 remain only 3*29 for the carbonic acid gas ; a result which 

 shows some error in the experiment, but still tends to prove 

 that the abstraction of the carbonic acid gas by the means 

 adopted throughout these experiments, viz. by a long and 

 comparatively wide tube with lime-water as the reagent, are 

 not less efficient than a small and closely graduated tube with 

 caustic potassa for the reagent, even although the latter be 

 employed over mercury- 

 Having no ostensible reason for mistrusting my previous 

 experiments, I began to reflect upon the probable sources of 

 error in those of Messrs. Allen and Pepys ; and hure I will 

 detail the most important circumstances attending their re- 

 searches upon the subject in (juestion. 



1st. Their experiments appear to iiave been made with 



