194 INUNDATIONS. 
rated current sweeps over it, it must produce precipitation 
which would fall upon it, or at a greater or less distance from it. 
We must here take into the account a very important consid- 
eration. It is not universally or even generally true, that the 
atmosphere returns its condensed humidity to the local source 
from which it receives it. The air is constantly in motion, 
howling tempests scour amain 
From sea to land, from land to sea ; * 
and, therefore, it is always probable that the evaporation drawn 
up by the atmosphere from a given river, or sea, or forest, or 
meadow, will be discharged by precipitation, not at or near the 
point where it rose, but at a distance of miles, leagues, or even 
degrees. The currents of the upper air are invisible, and they 
leave behind them no landmark to record their track. We 
know not whence they come, or whither they go. We have a 
certain rapidly increasing acquaintance with the laws of gene- 
ral atmospheric motion, but of the origin and limits, the begin- 
ning and end of that motion, as it manifests itself at any par- 
ticular time and place, we know nothing. We cannot say 
where or when the vapor, exhaled to-day from the lake on 
which we float, will be condensed and fall; whether it will 
waste itself on a barren desert, refresh upland pastures, de- 
scend in snow on Alpine heights, or contribute to swell a 
distant torrent which shall lay waste square miles of fertile 
corn-land ; nor do we know whether the rain which feeds our 
brooklets is due to the transpiration from a neighboring forest, 
or to the evaporation from a far-off sea. If, therefore, it were 
proved that the annual quantity of rain and dew is now as 
great on the plains of Castile, for example, as it was when they 
were covered with the native forest, it would by no means 
follow that those woods did not augment the amount of precipi- 
tation elsewhere. 
*Und Stiirme brausen um die Wette 
Vom Meer aufs Land, vom Land aufs Meer. 
GoreTHE, Faust, Song of the Archangels. 
