360 
DR. DALTON ON THE CONSTITUTION OF THE ATMOSPHERE. 
circumstance, attended by rain and a high wind S.E., might have some influence on 
the proportions of the atmosphere, I made the following experiments. 
Average of six experiments gave 20’75 oxygen per cent. 
When the remainder of this air had been kept five months in the bottle, it then 
yielded on an average of three experiments 20 67 oxygen per cent. 
1825, January 8. — Barometer 30 94, extremely high, after a week of calm weather. 
Filled a bottle with air from the town. 
Average of four experiments with two parts air and one hydrogen gave 21-12 oxygen 
per cent. 
The remainder of this air, kept till August same year, gave 21*1 oxygen per cent. 
June 8. — Average of four experiments from air in the town gave 20-97 oxygen per 
cent. ; barometer 29-90. 
June 10. — Air from a field near the town, barometer being 30’30, thermometer 70°, 
wind S.W. ; sunny and sultry. Two parts of the air with one of pure hydrogen being 
mixed, the average of six experiments gave 20-58 oxygen per cent. 
June 14. — Mixed some pure azotic gas with oxygen gas, which was marked 90 per 
cent, pure, in such proportions as to make a mixture of 21 per cent, oxygen. On 
trial with hydrogen the mixture gave, first experiment 21 -f- oxygen percent.; the 
second experiment 20*9 oxygen per cent. 
November 3. — Air in the town, barometer 28‘76, thermometer 46°, rainy, with S.W. 
wind. Average of ten experiments gave 20-6 oxygen per cent. 
Air from the Summit of Snowdon, 3570 feet above the sea, taken by John Black- 
wall, Esq., May 14, 1826, at 7 p.m. ; wind N.E. light, barometer 26 - 20, thermo- 
meter 42°. 
May 28. — Average of ten experiments gave 20'65 per cent, oxygen. 
Country air three miles from Manchester, analysed the same day, average of six 
experiments gave 20’8 per cent, oxygen. 
Again, Snowdon air in six experiments gave 20"66 oxygen per cent. ; but the bottle 
being now half full of water, I did not examine the rest. 
Another bottle of air was taken at the summit on another occasion, May 18, by the 
same gentleman ; wind S.W., light. 
May 25. — Analysed ; average of six experiments gave 20 - 59 oxygen per cent. 
Country air near Manchester at same time gave average 20‘7 per cent. 
A second bottle of air from Snowdon, taken at the same time. May 18, gave on an 
average of four experiments 20*9 oxygen per cent. 
Air from the town at the same time, on an average of five experiments, gave 2T04 
oxygen per cent. 
1826, July, Air from the Summit of Helvellyn. 
Average of ten experiments gave 20 - 63 oxygen per cent. 
Average of the town air found at same time was 20'73 oxygen per cent. 
