from D^c' 1823, to D^c. 1824. 



23Y 



from the East side, which is as 2 to 1 nearly: this difference 

 is probably induced in some measure by a contiguous and ex- 

 tensive sea, over which the air is free and unobstructed to- 

 wards the land. 



Causes of the great Difference in the yearly Amount of Rain 

 caught at different Places in the British Isles. 

 For a proof of the facts, I will select five places in which 

 the annual mean depth of rain, for a series of years, has been 

 determined by punctual observations, viz. 



I observed before that we have the full force of the W. and 

 S.W. winds here; and it may be relied on that before the 

 rain that is brought up by the prevailing westerly winds ar- 

 rives in London, it is not only diminished in quantity by pre- 

 cipitation, but the passing nimbi, or rain-clouds, are altered in 

 their electrical state, by inosculating with the warmer land air: 

 this alteration, with the comparative dryness of the land over 

 the sea air, and the artificial heat of populous places over 

 which the rain-clouds pass, tend to absorb and hold in solu- 

 tion a great portion of the passing vapours that would be 

 otherwise condensed and fall in rain in London or at Boston. 

 Upon this principle of reasoning, a less quantity of rain falls 

 at Boston than in London, which we see by the table is the 

 case ; because the tract of land over which it is moved by the 

 prevailing westerly winds is of greater extent from the shores 

 of .South Wales to Boston than it is from the southern shore 

 of England to London ; consequently about one-fourth of the 

 rain is spent in its passage over the land before it arrives at 

 these places. 



With respect to the difference of rain in places of a higher 

 North latitude: — Taking the annual depth at Kendal, in West- 

 moreland, to be one-third more than it is at New Malton, in 

 Yorkshire, which is very near the truth; to account for this 

 great difference in places too that are almost upon the same 

 parallel of latitude, it is necessary in the first place to ascer- 

 tain the character of the prevailing winds in botli })laces, which 

 I find by the meteorological tables to be at least one-fotirth of 

 tln! ycai- from the South-west point, from which quarter the 

 Uritish Isles receive most of the rain, as it conies immediately 

 :icross the Western Ocean. 



'J'he mean yearly depth of rain at Kendal is GO inches, and 



that 



