DR. DALTON ON THE CONSTITUTION OF THE ATMOSPHERE. 
359 
azotic gas, but rather less than half of its share of oxygen gas ; that is, it had about 
4 or 5 cubic inches of azote in the gallon, and only 1 cubic inch of oxygen. 
In the following train of experiments on the oxygen in the atmosphere I have 
mostly used from 50 to 70 measures of hydrogen for 100 air, unless otherwise men- 
tioned. 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 1/0 hydrogen for the maximum. In the former case the 
hydrogen is barely sufficient for the oxygen ; in the latter case the oxygen is barely 
enough to admit of a complete combustion, being only -^-th of the mixture. Perhaps 
the best proportion would be 100 air to 100 hydrogen to ensure complete combustion, 
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 measures 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 mountain 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 with hydrogen, about l 2070 oxygen 
50 to 100 air, gave J per cent. 
Average of four experiments of the common air taken in Man--\ 
Chester at the time of the analysis, and with same phial of ^ ox y§ en 
hydrogen and same proportion, gave J P ei cent - 
Average of seven experiments on Helvellyn air made a day i 20'58 oxygen 
afterwards, gave J per cent. 
Average of seven experiments on air from an open place in the "i 21*1 oxygen 
town next day with same hydrogen, gave J per cent. 
Average of eight experiments on the country air three miles ^ 
from Manchester, July 29, with same phial of hydrogen, ox y& en 
which now manifested a very slight trace of oxygen, gave J ^ ei cen ^' 
1824, November 23. — Barometer 28 inches, very low. Apprehending that this 
* This mountain, situate at the head of Ullswater, separates Cumberland 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. 
