216 Mr. Davy on the State of the Air, fyc. [March, 



sphere, during the preceding experiments, were so small, as not 

 to influence the accuracy of the general results stated. 



With a view to confirm the preceding statements, I made 

 comparative trials upon air collected from the open atmosphere, 

 at the top of the observatory belonging to the Cork Institution ; 

 a situation, perhaps, not less salubrious than any other in Cork. 

 The experiments were conducted in a manner precisely similar 

 to those I have noticed ; part of the same hydrogen was em- 

 ployed, and every precaution used to ensure accuracy. And in 

 every case in which the electric spark was passed through a 

 mixture of the air under examination and hydrogen gas, in the 

 proportion of 0*30 of each, the residual air measured about 

 Q-40. I collected air from Hughes's Lane, a place notorious for 

 the number of cases it had furnished of typhus ; but it yielded, 

 on examination, the same uniformity of result. 



I have made some trials on the other gaseous constituents of 

 the air, collected from the different fever wards, and compared 

 them with similar experiments on air from the observatory of 

 the Institution ; and I have found a very near coincidence in both 

 series of results. 



Thus, judging from the absorption that took place in the 

 bottles of air from the fever wards, when placed for some time 

 in water, and when agitated in this fluid ; and especially from 

 the effects of lime water on the air ; and comparing, by similar 

 trials, air collected from the atmosphere in salubrious situations ; 

 I could scarcely, in either case, discover a perceptible difference 

 in the quantity of carbonic acid gas. In one instance, I filled a 

 two quart ground stoppered bottle with the air from a large ward 

 at the House of Recovery ; and, on the spot, I put into the bottle 

 a small phial of lime water, and well closed it. After much occa- 

 sional agitation, and an interval of about two days, I examined 

 the carbonate of lime formed, and compared it with the quantity 

 produced under similar circumstances from the same bottle filled 

 with air from the observatory, and treated with lime water ; and 

 I was unable, in this way, to detect any appreciable difference. 

 If this method may be relied on, I think I may venture to state, 

 that the air from the ward did not contain nearly one per cent, 

 more of carbonic acid gas than the air from the observatory. 



After I had separated oxygen and carbonic acid gas from the 

 different airs examined, I could not detect the presence of any 

 other gas than nitrogen, which exhibited its characteristic nega- 

 tive properties. The want of leisure prevented me from varying 

 and multiplying my experiments, so as to ascertain the exact 

 proportion of the carbonic acid and nitrogen gases in the airs ; 

 and it may be proper to observe, that during the time I was 

 engaged in this inquiry, the variations of temperature, moisture, 

 and pressure of the atmosphere, were very small, and too often 

 connected with accidental circumstances, to be accurately 

 noticed. . 



