8 PHILOSOPHY OF STORMS. 



in all directions from the centre of the shower, especially 

 in front, while all the time, the air at some distance above 

 is running inwards from the circumference of the cloud at 

 its lower borders, and of course upwards in the centre, and 

 outwards in the upper parts. If we suppose a dew point 

 20 below the temperature of the air, we shall find, by cal- 

 culating according to the law (article 3,) that the lower 

 borders of the cloud will be a little more than twenty hun- 

 dred yards high ; and when the dew point is nearer the 

 temperature of the air, the cloud will be nearer the earth at 

 the lower extremity. This reasoning applies to clouds of 

 moderate size. 



23. But if the cloud is of great size, then the supply of 

 air to keep up the ascending column cannot be afforded 

 without reaching down to the surface of the earth, even 

 when the lower part of the cloud may be at a considerable 

 distance above the surface of the earth. Thus the law will 

 become general, that in all very great and widely extended 

 rains or snows, the wind will blow towards the centre of the 

 storm. 



24. From this law it will be easy to understand (when a 

 round storm is in our neighborhood) not only the direction 

 in which it is raging, but the course in which it is moving. 



For let 



c 



West 



D 



A E B be the direction in which the centre of a storm is 

 moving, say from west to east, and C an observer to the 

 north of that line, and D one to the south, when the storm 

 conies within disturbing influence, as at A, the observer C 

 will have the wind to begin to blow from a point north of 

 east, and the observer D from a point south of east, and to 

 the observer E, due east. When the storm shall have ad- 



