402 Dr. Dalton on the Constitution of the Atmosphere^ 



Average of eight experiments on the country*^ 

 air three miles from Manchester, July [ p, 

 29, with same phial of hydrogen, which )> ^^78^^ 

 now manifested a very slight trace of ^^^ ^^" * 

 oxygen, gave ...J 



1824', November 23. — Barometer 28 inches, very low. Ap- 

 prehending that this 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 experi- 

 ment 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 percent. 



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 + oxygen per 

 cent.; the second experiment 20*9 oxygen per cent. 



November 3. — Air in the town, barometer 28*76, thermo- 

 meter 46°, rainy, with S.W. wind. Average of ten experi- 

 ments gave 20*6 oxygen per cent. 



Air from the Summit of Snowdon, 3570 feet above the sea, 

 taken by John Blackwall, Esq., May 14, 1826, at 7 p.m. ; 

 wind N.E. light, barometer 26*20, thermometer 42°. 



May 28. — Average often 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. 



