CLIMATOLOGY. 369 



of investigators, serve as one of the main foundations of chapter 

 comparative climatology. Terrestrial magnetism did not ^-^^'l- 

 acquire a right to be regarded as a science, until partial 

 results vi^ere graphically connected in a system of lines 

 of equal declination, equal inclination^ and equal in- 

 tensity.''' 



The subject of climatology involves an extensive and Climatology, 

 extremely interesting class of phenomena, with their 

 resulting laws, — trade winds, land and sea winds, ocean 

 currents, the changes of seasons, &c. It also includes the 

 investigation of the curious results flowing from the ex- 

 tremely differing rates of variation of land and sea. From 

 the last of these arises the important contrast between 

 insular and littoral climates. "This remarkable contrast Differences 

 has been fully developed by Leopold von Buch in all its 

 various phenomena, ))oth with respect to its influence on 

 vegetation and agriculture, on the transparency of the 

 atmosphere, the radiation of the soil, and the elevation 

 of the line of perpetual snow. In the interior of the 

 Asiatic continent, Tobolsk, Barnaul on the Oby, and 

 Irkutsk, have the same mean summer heat as Berlin, 

 Munster, and Cherbourg in Normandy; the thermome- 

 ter sometimes remaining for weeks together at 86° or 88°, Excessive 

 whilst the mean temperature is, during the coldest 

 month, as low as • — 0°'4 to — 4°. These continental 

 climates have, therefore, justly been termed excessive by 

 the great mathematician and physicist, Buffon ; and the 

 inhabitants who live in countries having such excessive 

 climates seem almost condemned, like the sad expur- 

 gated souls in Dante's ' Purgatorio,' to suffer alike the 

 torments of heat and cold. 



" In no portion of the earth, neither in the Canary Is- Astrachan. 

 lands, in Spain, nor in the south of France, have I ever 

 seen more luxuriant fruit, especially grapes, than in 

 Astrachan, near the shores of the Caspian Sea (46^ 21'.) 

 Although the mean annual temperature is 48°, the mean 

 summer heat rises to 70°, as at Bordeaux, whilst not only 

 there, but also farther to the south, as at Kislar on the 



