258 THE FOREST LANDS OF FINLAND. 
and what happens thus to the heavier masses happens 
there or further in advance, in succession as the velocity is 
reduced, to others of lesser weight. 
But he also refers, as have other writers on Alpine tor- 
rents, to the more remarkable phenomenon of large stones 
seen bounding before the advancing wave of a mountain 
torrent. In regard to this he writes:—‘Some of the 
effects of torrents have appeared so extraordinary that, the 
the law of torrentiality not having been ascertained, the 
imagination set to work to seek out, fanciful explanations 
of what was seen. 
‘Thus, for example, has it been with the general 
allegation, that at the moment of flood large stones set 
off of themselves, rolling in advance before the current had 
touched them, under impulse from a current of air preced- 
ing the advancing head of waters. 
‘Eye-witnesses, and these grave men, have affirmed 
this fact to myself; and M. Surell has collected numerous 
testimonies of this phenomenon, and has sought to 
account for it theoretically. In reality, the fact as 
reported is absolutely impossible. Resistance increases as 
the square of the velocity. Let a calculation be made, 
from the velocity necessary to a current of air to displace 
a stone no larger than an egg; what velocity would require 
to be imparted to a current of air capable of displacing a 
stone such as some of those of which this has been told, 
which must have been at least 50 centimétres, or 20 inches 
in diameter! The thing alleged is physically impossible ; 
and it must be remarked that the people who allege they 
have seen those things occur under their eyes, at a few 
paces from them, do not dream that if they had been 
caught in such a current of air they would, at least, have 
felt it! 
‘When these witnesses are cross-questioned, they all 
declare that they have seen the stones rolling dry before 
them ; but no one says he has seen these stones begin to 
move, The witnesses are trustworthy, in so far as it is 
true that the stones were seen rolling before their eyes; 
