INUNDATIONS. 195 
The whole problem of the pluviometrical influence of the 
forest, general or local, is so exceedingly complex and difficult 
that it cannot, with our present means of knowledge, be de- 
cided upon @ priori grounds. It must now be regarded as a 
question of fact which would probably admit of scientific ex- 
planation if it were once established what the actual fact is. 
Unfortunately, the evidence is conflicting in tendency, and 
sometimes equivocal in interpretation, but I believe that a 
majority of the foresters and physicists who have studied the 
question are of opinion that in many, if not in all cases, the 
destruction of the woods has been followed by a diminution in 
the annual quantity of rain and dew. Indeed, it has long been 
a popularly settled belief that vegetation and the condensation 
and fall of atmospheric moisture are reciprocally necessary to 
each other, and even the poets sing of 
Afric’s barren sand, 
Where nought can grow, because it raineth not, 
And where no rain can fall to bless the land, 
Because nought grows there. * 
Before going further with the discussion, however, it is well 
to remark that the comparative rarity or frequency of inunda- 
tions in earlier or later centuries is not necessarily, in most 
eases not probably, entitled to any weight whatever, as a proof 
that more or less rain fell formerly than now; because the ac- 
cumulation of water in the channel of a river depends far less 
upon the quantity of precipitation in its valley, than upon the 
rapidity with which it is conducted, on or under the surface of 
the ground, to the central artery that drains the basin. But 
this point will be more fully discussed in a subsequent chapter. 
In writers on the subject we are discussing, we find many 
= Det golde Strég i Afrika, 
Der Intet voxe kan, da ei det regner, 
Og, omvyendt, ingen Regn kan falde, da 
Der Intet voxer. 
PALUDAN-MULLER, Adam Homo, ii., 408, 
