1818.] in the Fever Hospitals of Cork. 215 



ject. I procured air from five large and small wards in the 

 House of Recovery, and from the two wards in Peacock-lane 

 Hospital : I collected it from different parts of the rooms ; as, in 

 the middle, at the sides, near the floor, and at different heights 

 from it, and close to the beds of the patients. In every instance 

 the air was obtained by emptying on the spot bottles that had 

 been previously filled with distilled water, and immediately clos- 

 ing them. The bottles were perfectly air tight, being all fur- 

 nished with well-ground glass stoppers. The air was examined 

 soon after it had been collected. The first and most important 

 object of my inquiry, was to ascertain the quantity of oxygen 

 gas in the several bottles of air. For this purpose, I employed 

 hydrogen gas, and the electric spark ; a method that seems to 

 unite more simplicity and elegance than any other ; and, with due 

 precaution, is susceptible of great accuracy. As the purity of 

 the hydrogen, used in experiments of this kinds, is of conse- 

 quence to the accuracy of the results, it may be proper to notice 

 the mode by which it was obtained ; especially as it has, I 

 think, some little novelty, and seems to be quite unexception- 

 able, precluding all source of error, from the presence of com- 

 mon air. I put some small pieces of zinc into a glass, and 

 nearly tilled it with water that had been boiling for some time. I 

 then filled a tube with the boiling water, and inverted it in the 

 glass, and after adding sulphuric acid, I shortly after collected 

 the gas. 



I made a great number of experiments, using, in every instance, 

 an excess of hydrogen gas. In eveiy trial, I mixed 0*30 of a 

 cubic inch of the air under examination with 0*30 of pure 

 hydrogen gas ; and after agitating the mixture in a long, thick, 

 detonating tube, furnished with wires, the charge of a Leyden 

 phial was passed through the tube ; and the residual air, on being* 

 transferred to the cubic inch measure, occupied about 0*40 of it. 

 I venture to state this as a general result ; tor though, in a few 

 cases, there was a difference of about one per cent, more or less, 

 yet this difference was rather apparent than real, owing to the 

 difficulty of measuring uniform quantities of air, and it was 

 corrected by a careful repetition of the experiments. Now, as 

 two volumes of hydrogen and one of oxygen gas enter into 

 the composition of water ; if the foregoing results are made the 

 basis of a calculation, the apparent quantity of the oxygen gas 

 in the air from the different fever wards will amount to ubout 

 22*22 per cent.; but this is not the real quantity; a slight 

 allowance must be made for a minute portion of air disengaged 

 from the water after the detonation of the mixed gases ; and 

 when this is taken into account, the oxygen may be fairly 

 estimated at about 21 per cent. And, according to the state 

 ments of Sir Humphry Davy, and other able chemists, 21 per 

 cent, is the actual quantity of oxygen gas in the external 

 atmosphere, in different parts of the globe. It maybe remarked, 

 that the variations in the temperature and pressure of the atmo- 



