INUNDATIONS OF 1856 . 
393 
Guglielmini argued that the gravel and sand of the beds 
of running streams were derived from the trituration of rocks 
by the action of the currents, and inferred that this action was 
generally sufficient to reduce hard rock to sand in its passage 
from the source to the outlet of rivers. Frisi controverted this 
opinion, and maintained that river sand was of more ancient 
origin, and he inferred from experiments in artificially grinding 
stones that the concussion, friction, and attrition of rock in the 
channel of running waters were inadequate to its comminution, 
though he admitted that these same causes might reduce sili- 
cious sand to a fine powder capable of transportation to the 
sea by the currents.* Frisks experiments were tried upon 
rounded and polished river pebbles, and prove nothing with 
regard to the action of torrents upon the irregular, more or 
less weathered, and often cracked and shattered rocks which 
lie loose in the ground at the head of mountain valleys. The 
fury of the waters and of the wind which accompanies them 
in the floods of the French Alpine torrents is such, that large 
blocks of stone are hurled out of the bed of the stream to 
the height of twelve or thirteen feet. The impulse of masses 
driven with such force overthrows the most solid masonry, 
and their concussion cannot fail to be attended with the crush¬ 
ing of the rocks themselves.f 
d. Inundations of 1856 in France. 
The month of May, 1856, was remarkable for violent and 
almost uninterrupted rains, and most of the river basins of 
France were inundated to an extraordinary height. In the 
valleys of the Loire and its affluents, about a million of acres, 
including many towns and villages, were laid under water, 
and the amount of pecuniary damage was almost incal¬ 
culable.^: The flood was not less destructive in the valley of 
pieces of such limestone together.” — Wessely, Die 0esterreicMschen Alpen- 
lander , i, p. 113. 
* Frisi, Del modo di regolare i Fiumi e i Torrenti , pp. 4-19. 
f Surell, Itude sur lee Torrents , pp. 31-36. 
t Champion, Les Inondations en France , iii, p. 156, note. 
