280 SEDIMENT OF THE PO. 
into the sea at the rate of more than 200 feet ina year.* The 
depth of the annual deposit is stated at eighteen centimetres, or 
rather more than seven inches, and it would cover an area of 
not much less than ninety square miles with a layer of that 
thickness. The Adige, also, brings every year to the Adriatic 
many million cubic yards of Alpine detritus, and the contribu- 
tions of the Brenta from the same source are far from incon- 
siderable. The Adriatic, however, receives but a small propor- 
tion of the soil and rock washed away from the Italian slope of 
the Alps and the northern declivity of the Apennines by tor- 
rents. Nearly the whole of the débris thus removed from the 
southern face of the Alps between Monte Rosa and the sources 
of the Adda—a length of watershed ¢ not less than one hun- 
dred and fifty miles—is arrested by the still waters of the Lakes 
* This change of coast-line cannot be ascribed to upheaval, for a compari- 
son of the level of old buildings—as, for instance, the church of San Vitale and 
the tomb of Theodoric at Ravenna—with that of the sea, tends to prove a de- 
pression rather than an elevation of their foundations. 
A computation by a different method makes the deposits at the mouth of 
the Po 2,123,000 métres less; but as both of them omit the gravel and silt 
carried down at ordinary and low water, we are safe in assuming the larger 
quantity. 
+ Sir John F. W. Herschel (Physical Geography, 137, and elsewhere) spells this 
word water-sched, because he considers it a translation, or rather an adoption, 
of the German ‘‘ Wasser-scheide, separation of the waters, not water-shed the 
slope down which the waters run.” As a point of historical etymology, it is 
probable that the word in question was suggested to those who first used it by 
the German Wasserscheide ; but the spelling water-sched, proposed by Her- 
schel, is objectionable, both because sch is a combination of letters wholly un- 
known to modern English orthography and properly representing no sound re- 
cognized in English orthoepy, and for the still better reason that water-shed, 
in the sense of division-of-the-waters, has a legitimate English etymology. 
The Anglo-Saxon sccadan meant both to separate or divide, and to shade or 
shelter. It is the root of the English verbs to shed and to shade, and in the 
former meaning is the A. 8. equivalent of the German verb schetden. 
Shed in Old English had the meaning to separate or distinguish. It is so 
used in the Owl and the Nightingale, v. 197. Palsgrave (Lesclarcissement, ete., 
p. 717) defines Z shede, I departe thinges asonder; and the word still means 
to divide in several English local dialects. Hence, watershed, the division or 
separation of the waters, is good English both in etymology and in spelling. 
