FALLS OF RAIN IN CUMBERLAND. 199 



rain than the Valley, that is only 160 feet high, showing 

 that here less rain fell in the higher than in the lower parts; 

 and there are other anomalies that might be pointed out. 

 It is, however, such a place as Seathwaite that shews, in the 

 most palpable and striking way, that the amount of rain that 

 is received by the ground in a particular locality is not de- 

 termined by its height. Seathwaite, not faore than 240 

 feet above the sea, receives more rain than any of the places 

 having a greater elevation ; and Mr. Millar candidly admits 

 that he is *' unable to offer any satisfactory reason for the 

 great excess of rain at Seathwaite over all other valleys ;" and 

 he might have said, over all other places in the locality, 

 high as well as low. 



In order to account for the great and unequal quantities 

 of rain that fall in different parts of this district, it is neces- 

 sary that we should briefly advert to the causes which de- 

 termine the formation of rain at various heights in our 

 atmosphere. The first, is the progressive diminution of 

 temperature from the surface upwards, which is 1° for every 

 300 feet of height ; and it follows from this, that any mass of 

 the atmosphere saturated with aqueous vapour that is forced 

 to ascend 300 feet will be cooled 1°— 600 feet 2°— 900 feet 

 3°, and so on progressively to greater heights, and the 

 aqueous vapour that is intermingled with the air will be 

 condensed in proportion to that cooling. If at any time 

 condensation was slight on the low ground near the sea, it 

 would become greater should the air be forced to ascend 

 the valleys, and climb the sloping sides of mountains ; and 

 the greatest amount of condensation of vapour, and conse- 

 quent formation of rain, would be at some certain height 

 determined by the extent to which the air was saturated 

 with vapour. The following figures will shew the heights 

 at which vapour would be condensed under certain circum- 

 stances ; that is to say, with the air and dew-point of the 

 vapour at the surface both at 59^ when the tension of 



