A r P E N B I X. 



IX. 



Month. 



Barometric range daily. 



ThennomeiriQ range cUilj 



May, 



0.103 



28,4' 



June, 



0.084 



20,3 



July, 



0.062 



0,3 



August, 



0.068 



8,9 



September, 



0.070 



9,5 



October, 



0.070 



J 6,0 



November, 



0.070 



J 8,4 



December, 



0.075 



15,7 



There can be very little doubt therefore that the change of atmospheric pressure is 

 simply caused by the altered specific gravity of the air due to the temperature. The 

 same effect should be visible to a greater extent in the monthly variation of the two 

 instruments, because a wider stratum of air is influenced by the monthly change of 

 heat, than can be by its daily action. To compare the actual motions, I here pre- 

 sent the monthly differences of the Thermometer and Barometer from the annual mean 

 of each, extracted from my Table. 



Barometer. Tliermometer. 



Annual Mean 29.538 Annual Mean 76,94 



4 0.236 —17.28 



4- 0.198 — 1 0.98 



4 0.087 4 3.06 



— 0.0G7 + 12.39 

 . —0.115 4 13.90 



— 0.275 4 15.55 



— 0.301 + 5.26 



— 0.220 4 4.05 



— 0.122 4 4.39 

 4 0.071 — 0.59 

 4 0.237 — 12.78 

 4 0.2G5 —16.91 



The effects here are just five times greater than; in the former table: although they 

 are still only one-third of what would be produced if the whole atmosphere were a- 

 likc acted upon ; that is, if the whole air were heated 



5 degrees the pressure should fall 0.300 inches, 



whereas 15 in a month it falls 0.300 



and 25 . . . . in a day 0.100 



• Month. 



January, 



February, 



March, 



April, 



May, 



June, 



July, 



August, 



September, 



October, 



November, 



December, 



