CLIMATOLOGY. 317 



Sea, and in. the still more ancient and more general acquaint- 

 ance with land and sea winds, lies concealed, as it were, the 

 germ of that meteorological science which is now making such 

 rapid progress. The long chain of magnetic stations extend 

 ing from Moscow to Pekin, across the whole of Northern Asia, 

 will prove of immense importance in determining the law of 

 lite winds, since these stations have also for their object the 

 investigation of general meteorological relations. The com- 

 parison of observations made at places lying so many hundred 

 miles apart, will decide, for instance, whether the same east 

 wind blows from the elevated desert of Gobi to the interior of 

 Russia, or whether the direction of the aerial current first be- 

 gan in the middle of the series of the stations, by the descent 

 of the air from the higher regions. By means of such observ- 

 ations, we may learn, in the strictest sense, wlience the wind 

 cometh. If we only take the results on which we may de- 

 pend from those places in which the observations on the direc- 

 tion of the winds have been continued more than twenty years, 

 we shall find (from the most recent and careful calculations 

 of Wilhelm Mahlmann) that in the middle latitudes of the 

 temperate zone, in both continents, the prevailing aerial cur- 

 rent has a west-southwest direction. 



Our insight into the distribution of heat in the atmospheiv 

 has been rendered more clear since the attempt has been made 

 to connect together by lines those places where the mean an- 

 nual summer and winter temperatures have been ascertained 

 by correct observations. The system of isotliermal, isotheral, 

 and isodiimenal lines, which I first brought into use in 1817, 

 may, perhaps, if it be gradually perfected by the united efforts 

 of investigators, serve as one of the main foundations of com- 

 parative climatology. Terrestrial magnetism did not acquire 

 a right to be regarded as a science until partial results were 

 graphically connected in a system of lines of equal declina- 

 tion, equal inclination, and equal intensity. 



The term climate, taken in its most general sense, indicates 

 all the changes in the atmosphere which sensibly affect our 

 organs, as temperature, humidity, variations in the baromet- 

 rical pressure, the calm state of the air or the action of oppo 

 site winds, the amount of electric tension, the purity of the 

 atmosphere or its admixture with more or less noxious gase- 

 ous exhalations, and, finally, the degree of ordinary transpar- 

 ency and clearness of the sky, which is not only important 

 with respect to the increased radiation from the Earth, the 

 organic development of plants, and the rij- -ning of fruits, but 



