and on the Sulphurets of Lime, 401 



In the following train of experiments on the oxygen in the 

 atmosphere I have mostly used from 50 to 70 measures of hy- 

 drogen for 100 air, unless otherwise mentioned. Possibly this 

 may not be thought the best proportion for securing the com- 

 plete abstraction of the oxygen. The limits are, 100 air with 

 42 of hydrogen for the minimum, and 100 air with 170 hy- 

 drogen for the maximum. In the former case the hydrogen 

 is barely sufficient for the oxygen ; in the latter case the oxy- 

 gen is barely enough to admit of a complete combustion, be- 

 ing only y^^th of the mixture. Perhaps the best proportion 

 would be 100 air to 100 hydrogen to ensure complete com- 

 bustion, because it is about the mean of the two extremes ; but 

 it must be considered that if the hydrogen should contain even 

 a very small portion of oxygen, the whole of it in 100 mea- 

 sures would be included in the atmospheric oxygen, so that 

 in practice it would probably be safest to use a mean between 

 40 and 100 of hydrogen. I have mostly endeavoured to keep 

 between 50 and 70 of hydrogen for 100 air. 



Experiments on the Quantity of Oxygen in Atmospheric Air, 

 Air from the Summit of Helvellyn*, July 14, 1824. 



A phial, containing about half a pint, was filled with water at 

 a clear rivulet on the ascent : this was emptied at the summit 

 and well corked ; the cork was drawn at the foot of the moun- 

 tain in a trough of clear running water, when a quantity of water 

 was found to enter corresponding to the increased pressure 

 of the atmosphere. The phial was then corked and inverted 

 in a cup of water, and the air analysed a week afterwards. 



Average of four experiments on this air"! 20*70 oxygen 

 with hydrogen, about 50 to 100 air, gavej per cent. 



Average of four experiments of the common 

 air taken in Manchester at the time of the 

 analysis, and with same phial of hydro- 

 gen and same proportion, gave 



Average of seven experiments on Helvellyn^ 20*58 oxygen 



air made a day afterwards, gave J percent. 



Average of seven experiments, on air from ^ ^- 



an open place in the town next day with > ^ yg^^ 

 u J I per cent, 



same hydrogen, gave J ^ 



* This mountain, situate at the head of Uilswater, separates Cumber- 

 land from Westmoreland ; its height above the sea, which lies to the S.W., 

 and from which it is distant about 20 miles, is upwards of 3000 feet; it is 

 surrounded by other mountains, mostly of less elevation. 



Phil. Mag, S. 3. Vol. 12. No. 76. May 1838, 2 N 



^20*88 oxygen 

 per cent. 



