74 PHILOSOPHY CF STORMS. 



in rising, and preserves a more erect position, and thus can 

 attain a greater elevation. Hence, the first attempts of 

 columnar clouds to rain are generally failures, because 

 their tops are generally shaved off or pressed over towards 

 the north east, and thus dissipated without raining; each suc- 

 ceeding cloud in its wake finding a stiller air in its upward 

 motion, attains a greater elevation. Finally, one reaches a 

 height sufficient to produce rain, and then a new source of 

 power is called into action, powerfully aiding the formation 

 of sprouts. This is the descending rain cooling the air 

 below the cloud, and causing it by its greater specific 

 gravity, and also by the weight of the drops of rain, to 

 move outwards in all directions from the centre of the rain. 



Now as the air all round the parent cloud is running in 

 at the base of the cloud, and below towards the cloud, this 

 air is obliged to rise up over the stratum of cold heavy air, 

 pressed outwards around the borders of the shower, and 

 thus its upward motion is increased ; and as the dew point 

 is more likely to be higher on the south side of the cloud 

 than on the north, sprouts will on that account be more 

 likely to form on the south than on the north. To see the 

 formation of sprouts to the greatest advantage then, the 

 cloud should be to the north of the observer. 



If these theoretical deductions are correct, and as far as 

 observation extends it does not contradict them, it would 

 follow, that the progress of rain may be from a northern 

 direction, though the upper current may be constantly car- 

 rying the hazy cloud formed from the tops of all these 

 columns towards the east. Further observations are want- 

 ing on this point. 



I would recommend that gentlemen residing in mountain- 

 ous districts, where the clouds sometimes form on the sides 

 of the mountains, should ascertain the perpendicular height 

 of these clouds at their base, and see whether they are one 

 hundred yards high for every degree of Fahr. which the 



