FLOODS OF THE ARDECHE. 959 
known except in the local topography of France, contributed 
to the Rhone once and a half, and for three consecutive days 
once and one third, as much as the average delivery of the Nile 
during the same periods, though the basin of the latter river 
probably contains 1,000,000 square miles of surface, or more 
than one thousand times as much as that of the former. 
The average annual precipitation in the basin of the Ar- 
déche is not greater than in many other parts of Europe, but 
excessive quantities of rain frequently fall in that valley in the 
autumn. On the 9th of October, 1827, there fell at Joyeuse, 
on the Beaume, no less than thirty-one inches between three 
o’clock in the morning and midnight. Such facts as this ex- 
plain the extraordinary suddenness and violence of the floods 
of the Ardéche, and the basins of many other tributaries of the 
Rhone exhibit méteorological phenomena not less remarkable.* 
* The Drac, a torrent emptying into the Isére a little below Grenoble, has 
discharged 5,200, the Isére, which receives it, 7,800 cubic yards, and the 
Durance, above its junction with the Isére, an equal quantity, per second.— 
Montuvisant, Note sur les Desséchements, etc., Annales des Ponts et Chaussées, 
1853, 2me sémestre, p. 288. 
The Upper Rhone, which drains a basin of about 1,900 square miles, includ- 
ing seventy-one glaciers, receives many torrential affluents, and rain-storms 
and thaws are sometimes extensive enough to affect the whole tributary 
system of its narrow valley. In such cases its current swells to a great 
volume, but previously to the floods of the autumn of 1868 it was never known 
to reach a discharge of 2,600 cubic yards to the second. On the 28th of Sep- 
tember in that year, however, its delivery amounted to 3,700 cubic yards to 
the second, which is about equal to the mean discharge of the Nile.—Berichte 
der Huperten-Commission tiber die Ueberschwemmungen im Jahr 1868, pp. 
174, 175. 
The floods of some other French rivers, which have a more or less torren- 
tial character, scarcely fall behind those of the Rhone. The Loire, above | 
Roanne, has a basin of 2,471 square miles, or about twice and a half the area 
of that of the Ardéche. In some of its inundations it has delivered above 
9,500 cubic yards per second, or 400 times its low-water discharge. —BELGRAND, 
De V Influence des Foréts, ete., Annales des Ponts et Chaussées, 1854, ler sémes- 
tre, p. 15, note. 
The ordinary low-water discharge of the Seine at Paris is nearly 100 cubic 
yards per second. Belgrand gives a list of eight floods of that river within 
the last two centuries, in which it has delivered thirty times that quantity. 
