On the Tkiorp of mixed Gases. 1 13 



to 102 or 104 degrees : this is succeeded by local thunder 

 storms, attended wiih heavy falls of rain and hail, as well as 

 violent hurricanes. I do not pretend to assign the refrige- 

 rating cause, or the agent that produces precipitation in this 

 case; I only have to observe, that the portion of air must 

 lose much of its elasticitv, which is suddenly cooled to 70 

 or 72 degrees, and at the same time parts with the water it 

 held in solution. This partial diminution of spring will 

 destroy the equilibrium of the adjacent parts of the atmo- 

 sphere, and may be supposed to produce the tornadoes of 

 the tropical regions. The same cause probably gives rise 

 to the fluctuations of the barometer in milder climates ; for, 

 though the changes of temperature are less in the milder 

 than in the hottest parts of the globe, the agents that pre- 

 cipitate the water of the atmosphere appear to act on a more 

 extensive scale, and through a longer duration, in the former 

 situations than they do in the latter. Wet weather is neither 

 momentary nor local in Europe ; provinces, and even king- 

 doms, are deluged with rain for weeks together. The air,- 

 which discharges such an abundance of water, v.'ill lose part 

 of its spring, according to Mr. Schmidt's experiments, even 

 when it suffers no change of temperature : now it is evident 

 that the equilibrium cannot be restored in an instant, be- 

 cause the diminished elasticity must be augmented in this 

 case by currents of air coming from remote places. The 

 diminution of spring in the atmosphere is shown by the 

 fall of the barometer, and the subsequent ascent of the mer- 

 cury indicates the arrival of tlie restorative currents. Ac- 

 cording to this explanation the barometer will rise slowly 

 but gradually in the centre of the rainy district, while the 

 motions of it will be more rapid and less regular towards 

 the verge of the storm. lii^h winds will also prevail in wet 

 seasons, which will blow towards the parts where the elasiic 

 force of the air is least; that is, where the rains are most 

 abundant. — I know not what claim to originality is due to 

 the foregoing hints towards the theory of the barometer; they 

 have, however, the merit of being a natural consequence of 

 an established fact; I tnean the great dilatation of air satu- 

 rated with moisture, which must undergo a proportionate 

 contraction when deprived of water. 



V^ol. 24. No. 94. March ISOG. H XX. ^k 



