Atmospherical Phenomena. 269 



masses of vapour arrive, the clouds become denser, and rain 

 descends. As the wind veers to the west, while the barometer 

 at the same time is rising, the rain becomes heavier, the con- 

 densation into clouds also takes place in the lower strata of the 

 atmosphere, but the cirri above disappear. If, finally, while 

 the barometer is rising, the wind veers to the NW. and N., 

 although separate showers of rain occur, yet the sky gradually 

 clears up. 



The series of changes we have noticed is that which more 

 generally takes place, although it does not always occur in the 

 same regular course that has been mentioned above. As the 

 wind veers round during its changes, so is it also with the ac- 

 companying weather, of which one can very easily become con- 

 vinced, by comparing a sufficiently delicate wind-vane and the 

 course of the clouds, with the other phenomena of the weather. 

 I have already mentioned that the moist SW. and the con- 

 tinental NE. are opposed to each other in regard to the falls of 

 rain, but the possibility is not thus denied of rainy weather oc- 

 curring during a NE. and serene weather during a SW. wind. 

 But the falls of rain that take place during the two winds are 

 distinguished from each other in a remarkable manner. Widely 

 extending general rains accompany a SW. wind, and the water 

 falls slowly and in small drops for days together ; while the NE. 

 for the most part drives along violent showers of short dura- 

 tion, which is especially the case when, while the barometer is 

 high, the wind does not veer regularly from N. through N.E. 

 to E., but changes suddenly in an irregular manner back to 

 NW. or W. 



It thus appears that the most important phenomena of the 

 weather may be explained simply by the relations of tempera- 

 ture ; but, on the other hand, the currents of air and the face 

 of the heavens have a great influence on the warmth of a dis- 

 trict, and it is precisely the circumstance of what is the result 

 of one phenomenon becoming the next moment the cause of the 

 succeeding one, that accounts for meteorology being so far be- 

 hind the other departments of physics, owing to the complica- 

 tion of its phenomena. Inasmuch as we can only observe the 

 thermometer near the ground, the temperature there may be 

 very low, although south winds, during a low state of the baro- 

 meter, impart considerable warmth to the upper strata of the 



