The Caucasian., 1910-02-08
produced by this combination of tor.
rents of different origin
Exnan4sanal EiaaI.

| rents or Inherent origin.
Exceptional Floods.
NJ. Lemoine has divided the flood of
the Seine at Paris into three classes,
| denominating floods which rise be-
| tween 1874 and 1871 feet on the Tour
nellie gauge as ordinary large floods,
| those rising between 1877 and % feet
as extraordinary foods and those ris-
ing above % feet as exceptional floods
Between the beginning of the daily
readings of the gauge in 1882 and the
present time there had been but two
exceptional foods before this one in
1910 In December, 1740, the water
rose to a height of 1896 feet, and in
January, 1902, 1t reached 24.37 feet.
Belgrand gives list of five excep-
tlonal floods which occurred between
1649 and 1732-namely, in February,
1649; January. 1861; February, 1858;
April, 1000, and March, iii. That of
1858 alone was higher than the flood
of 1T40, reaching the height of 2S.9
feet, being by nearly three feet the
highest flood on record at Paris until
the present time. The four others
previous TO 1882, though lower than the
food of 1740, all exceeded 24.37 feet,
the record of 1902.
Only two unusually high floods
threatened Paris between 1850 and
1910. They were in March, 1876, and
in January, 1888, reaching 21.33 feet
and 1850 feet respectively, though the
floods of December, 1872, and 1882
were only little lower as they rose
to 1919 and 1915 feet. These last two
floods were the first of unusual height
to which the system of predictions and
warnings was thoroughly and success
fully applied. Both were due in part
to succession Of small inundations
from the torrential tributaries, but
they presented some notable differ
ences. The flood of 1876 was unusually
late in the cold season and followed an
almost continuous rainfall of more than
five weeks, upon melting snow in the
beginning and then upon soil previous
ly saturated by the winter rains. The
river rose almost continuously at Paris
from the middle of February till the
18th of March, when it attained its
maximum. In January, 1888, the ris-
ing of the river was the result of two
distinct periods of heavy rainfall fol-
lowing close upon one another, the first
lasting about month and the second
for ten days.
How Flood Predictions Are Made.
Predictions of the probable height of
floods are based on a system devised
by Belgrand for use In the protection
of Paris. BY series of careful OBJ
servations he was enabled to trace a
relation between the rise of the va
rious tributaries at certain points and
the corresponding rise of the Seine at
Paris or lower down. The usual rule
adopted for calculating the probable
rise at the bridge of Austerlitz in
Paris is to double the mean of the
rises observed on the Yonne at various
points. The mean time occupied by
the maximum flood level In travelling
from the upper tributaries to Paris
is three days and four-tenths and
one day from Paris to Nantes. The
rise at Nantes Is generally the same
as at Paris.
Announcements are generally made
three days In advance, and q corrected
prediction is issued twenty-four hours
later. The heights predicted are usu-
ally somewhat in excess of the actual
rise recorded, owing to the natural
anxiety not to give too low an esti-
mate Of the danger. But remarkable
condolences have occurred. The pre-
diction on March Is, 1876, for the fol
lowing day was 2t.33 feet, and 1t was
exactly verified on the 10th. At Paris |
the exact maximum of the food of |
January, 1888. was predicted on the
evening before.
In the course of the last half cen |
tury many millions of dollars worth |
Of property have been saved by the
needing of these official warnings.
The projections of Paris have been
increased from time to time by the
raising of the quays along the river
and by prolonging the outfall sewers
SO as to place their outlets beyond
the town, and entertainments have been /
built for many of the low lying dis
tricts. The rebuilding also of old
bridges with more ample waterways
and the Improvements In depth for
navigation have greatly increased the
discharging capacity of the river.