CLIMATES OF GREAT MALVKHN AND LONDOX. 



2^3 



It is a gjeneral fact that winds blowing" over large tracts of land 

 are considerably colder than those blowing over the ocean. The 

 reasons for this it is hardly necessary for us to explain here, but the 

 consequence is that N. E. winds are the coldest, S. W. the warmest j 

 N. VV. are intermediate, with a northerly character 5 the S. E. inter- 

 mediate, with a southerly character. 



From these considerations, therefore, the winds are more accu- 

 rately divided in the following diagram. 



The dew-point can never be higher than the temperature of the 

 air. Supposing, therefore, during the winter in the high regions 

 of Lapland, Sweden, and Norway, the temperature of a breeze to be 

 20° or 24® F., often doubtless very much lower, air of that tempe-* 

 rature cannot hold vapour higher than 20° or 24° This atmos- 

 phere being put in motion, and rushing rapidly to the southern 

 and warmer regions, is constantly acquiring a higher temperature, 

 but passing over only a limited track of ocean, it acquires but little 

 increase in its vapour 5 the dew-point, consequently, remains very 

 nearly the same. 



Let us suppose that such a breeze has reached the temperature of 

 32° or S4° when arriving at the British Isles, the difference 

 between this and the dew-point (20° or 24°) would constitute a 

 very dry harsh wind, little likely to be accompanied with any deposi- 

 tion J on the contrary, drying up all the moisture it meets with, it 

 would have precisely the character of our N. E» toinds in a very 

 marked degree. 



On the other hand, a S. W. breeze coming from the warmer 

 regions and over an immense tract of ocean, into the colder tempe- 

 rature of Britain, would soon become cooled, until the temperature 

 of the air was no greater than the temperature of the vapour 

 it bears with it or the dew-point. At this point, and pursuing still 

 its northerly course, some of the vapour must be precipitated, or 

 take the shape of cloud, in either of which cases it parts with that 

 portion of its temperature which was necessary to its invisible 



May, 1835. — vol. ii, no. x. 2 o 



