THEORY CONFIRMED BY PHENOMENA. 49 



ity, for some time, without overlapping each other, and 

 crossing, which proves that they are on the same horizontal 

 plane, and so demonstrates the existence of a vortex. I need 

 hardly add, that other phenomena show that the motion, af- 

 ter meeting, is upwards, and not downwards. 



80. Clouds have also frequently been seen to ascend, by 

 spectators on mountains, and aeronauts have found their 

 temperature much higher than the surrounding air. Thus, 

 it is demonstrated, beyond all doubt, that there is an upward 

 current in these storms, whether the latent caloric given out 

 by the condensation of the vapor, is the cause of that cur- 

 rent, or not. And, as no fact in physics is better established 

 than that precipitation will instantly take place, if saturated 

 air is suddenly rarefied, we are sure, also, that this upward 

 motion of saturated air will, by causing expansion, produce 

 precipitation. 



81. I had long been desirous to ascertain, by actual obser- 

 vation, how high these vortices carry the condensed vapor, 

 or cloud, into the upper air, and a fine opportunity was af- 

 forded me, on the 31st of July, 1834. This morning, says 

 my journal of that day, "it began to rain early, with the 

 wind and lower clouds north east, middle clouds south, and 

 upper clouds west." Several showers occurred during the 

 morning, and the wind gradually shifted round to the south 

 east. About five o'clock, P. M., a most violent shower, 

 which lasted about fifteen minutes, came up from the north 

 west, and at the moment of the hardest rain, the lower wind 

 being strong from the north west, the lowest visible clouds 

 in a south east direction, were seen to move with great velo- 

 city in the opposite direction, towards the north west. 



As soon, however, as the shower passed off to the south 

 east, the lower clouds changed their course, and followed 

 the shower towards the south east, exposing to view, near 

 the zenith, a most magnificent columnar cloud, with its sum- 

 mit and western side as white as snow, being exposed to a 



7 



