connection with the Climate of Berlin. 217 



rents. The extremes of our weather are regulated by the unequal 

 prevalence of the one or the other of these currents, which, as long- 

 as they preserve a due equilibrium between each other produce 

 the changeable weather which is most characteristic of our climate. 

 The northern current is cold, heavy, and dry ; the southern warm, 

 moist, and light ; with the former the barometer is high and the 

 thermometer low, with the latter it is the reverse. I must, however, 

 remark that when air flows from north to south or vice versa, its 

 direction is affected by the revolution of the earth on its axis. Air 

 which, for example, sets out as due north from Breslau to Vienna 

 arrives there at NNE. ; it would be NE. at Vienna if it set out due 

 north from Konigsberg ; ENE. if it set out from Riga ; and almost 

 east if we consider it as setting out due north from St Petersburg. 

 Therefore, air which has been stationary between Petersburg and 

 Vienna, and is then set in motion towards the south will cause the 

 vanes at Vienna to turn by degrees from north through NE. to east. 

 If, on the contrary, the air has been set in motion towards the north 

 and has set out from Trieste, it will arrive at Vienna as a SSW. 

 wind, — if it had set out from Rome, it would have been a SW. ; 

 WSW. if it had set out from Tunis ; and lastly, almost W. if its 

 cradle had been situated farther towards Africa. Every current of 

 air, therefore, which flows from the north becomes more easterly the 

 longer it lasts, every south wind more westerly. North-east is, 

 therefore, a north wind which sets out from a Greater distance, and 

 south-west is a south wind setting out from a distant place. The 

 coldest, heaviest, driest wind is therefore north-east, not north ; the 

 moistest, lightest, warmest wind, not south, but south-west. 



The mutual struggle of the two opposing currents necessarily pro- 

 duces a revolution ; under these circumstances a south wind would bo 

 followed by a west wind, then by a north, then east, and lastly south 

 again. 



Thaw and continued rain accompany the southern currents, — the 

 most cloudless weather and severest cold come with the east wind, 

 — pleasant dry weather is the most striking sign of the north cur- 

 rent in summer. In September and the beginning of October, 

 when this current predominates, we have, therefore, our most beauti- 

 ful weather which, when it becomes strikingly warm, we call our 

 back summer (after summer). But it is not so regular in the time 

 of its duration as in America, where it is named the Indian summer, 

 because the Indians then go to their hunting grounds, when, as they 

 say, the Great Spirit sends them their summer. In November, on 

 the contrary, on account of the then prevailing south current, we 

 experience that very interesting form of weather which goes by the 

 name of Pomeranian mists. The north current flows slowly then in 

 its ever-widening bed, and therefore in the Petersburg Gazette the 

 cold is already spoken of as having set in before the NE. wind 

 has brought it to us. The south current, on the other hand, 



