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at a period still more remote the Euganian mountains
may have been islands.

My learned brother of the Institute, M. de Prony,
inspector general of the bridges and roads, has
communicated to me his valuable researches
explanatory of these changes in the shores of the
Adriatic.

EXTRACT FROM THE RESEARCHES OF M. DE PRONY,
ON THE HYDRAULIC SYSTEM OF ITALY.

"Account of the displacement of that portion of the
banks of the Adriatic sea, which is occupied by the
mouths of the Po.

"That part of the coast of the Adriatic, contained
within the southern extremities of the lake, or rather
the lagoons (lagunes,) of Comachio, and the lagoons of
Venice, has undergone since early times vast changes,
attested by many veracious authors, and which is borne
out by the present state of the soil in the districts on
the coast; but it is impossible to detail with precision
the successive progress of these changes, and
particularly the exact measures previously to the
twelfth century of our era.
"We are however sure that the city of Atria, now
Adria, was formerly situated on the sea-coast; and this
gives us a decided and known point of the primitive
shore, whence the shortest distance to the present
shore, taken from the mouth of the Adige, is 25,000
metres,* (l5 1/2 miles and upwards.) The

* We shall find that the farther extremity of the alluvial
promontory formed by the Po, has advanced into the sea
farther by ten thousand metres (64 miles nearly) than the
mouth of the Adige.

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inhabitants of the city have formed very exaggerated
notions, in many instances, on the antiquity of this
city; but it cannot be denied that it is one of the most
ancient in Italy; it gave name to the city which washed
its walls. By some excavations made there, and in the
vicinity, a stratum, mixed with relics of Etruscan
pottery has been discovered, in which there is no
mixture of Roman workmanship; the Etruscan and
Roman are found mingled in an upper stratum, above
which the vestiges of a theatre have been found. Both
layers are very much below the present soil. I have
seen in Adria curious collections, in which the relics
that they contain are arranged separately. The prince
viceroy,to whom I observed how interesting it would
be to history and geology, if a research were made into
all the excavations of Adria, as well in the primitive
soil, as in the successive alluvial deposites, seemed
much struck with my suggestions, but I am not aware
if they were carried into effect.
"On leaving Atria, which was seated at the bottom
of a small gulf,we find, in following the line of coast,
to the south, a branch of the Athesis (Adige) and the
Fossa Philistina, of which the remaining trace
corresponds with what might have been the re-union of
the Mincio and Tartaro, if the Po still flowed
southward of Ferraro. Afterwards we come to the Delta
Venetum, which appears to have occupied the place
now the site of the lake or lagoon of Comachio. This
Delta was traversed by seven branches of the Eridanus,
orVadis Padus, Podincus or Po, as it was variously
called, which had on its left bank, at the various
ramifications of these mouths, the city of Trigopolis
(Trigoboli) whose site could not be very distant from
Ferraro. The seven lakes of the Delta were called
Septem Maria, and Hatria

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is sometimes called Urbs Septem Marium, or the city
of the seven seas or lakes.
"Pursuing the line of coast more north from Hatria,
we reach the principal embouchure of the mouth of the
Athesis, called also Fossa Philistina, and Æstuarium
Altini, an inland sea, separated from the ocean by a
chain of islets, in the midst of which is a small
archipelago of other islands, called Rialtum, on which
cluster Venice now stands. The Æstuarium Altini is the
lagoon of Venice, which only communicates with the
sea by five passages; the small islands which have been
united to form a continuous dyke.
"Eastward of the lagoons, and northward of the city
of Este, are the Euganian mountains, forming in the
midst of a vast alluvial plain, a singular and isolated
group of conical hills, near which the ancients fixed
the spot of the celebrated fall of Phæton. Some writers
assert that this fable originated from the vast masses of
inflamed materials, cast by the volcanic eruptions into
the mouths of the Po. It is certain that a great quanty
of volcanic productions are found in the vicinity of
Padua and Verona.
"The earliest information which I have attained
respecting the situation of coast of the Adriatic, at the
mouths of the Po, has, from the twelfth century some
exactness. At this period all the waters of the Po
flowed southward of Ferraro, in the Po di Volano, and
the Po di Primaro, ramifications which then flowed
over what is now occupied by the lagoon of
Commachio. The two mouths with which the Po
afterwards made an irruption northward of Ferraro,
were called respectively, the river of Corbola,
Longola, or Mazorno; and the river of Toi. The
former, which was most northward, the Tartaro

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or Canal Bianco, near the sea; the latter was increased
at Ariano by a branch of the Po, called the river Goro.
"The coast of the sea was possibly inclined from
south to north, at a distance of ten or twelve thousand
metres (between six and eight English miles) from the
meridian of Adria; it then passed the western angle of
Mesola; and Lorea, north of Mesola, was only distant
about two thousand metres (more than a mile.)
"About the middle of the twelfth century, the great
waters of the Po passed across the dykes which
restrained them on the left side of the coast, near the
small city of Ficarolo, situated 19,000 metres (nearly
twelve miles) north-west of Ferrara, and spreading
themselves over the northern territory of Ferrara, and
the Polesine of Rovigo, flowed into the two above-
mentioned canals of Mazzorno and Toi. It is well
known that the labour of man has had much to do in
effecting this diversion of the waters of the Po; and
historians who have mentioned this remarkable fact,
only differ in the detail. The tendency of the river to
follow the new tracks made for it, becoming daily
more and more powerful, the two branches of the
Volano and the Primaro rapidly decreased, and were in
less than a century reduced nearly to the state in which
they now are, and the main channel of the river was
formed between the mouth of the Adige, and the place
now called Porto di Goro. The two canals becoming
inadequate, new ones were dug; and at the beginning
of the seventeenth century, its principal mouth, called
Bocco Tramontana, having approached too nearly to
the mouth of the Adige, it greatly alarmed the
Venetians, who in 1604, dug the new bed called Taglio
de Porto Viro, or Po delle Fornaci, by means of

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which the Bocco Maestrawas diverted from the Adige
towards the south.
During the four hundred years which elapsed from
the end of the twelfth to the end of the sixteenth
century, the alluvial deposites of the Po gained
considerably on the sea. The northern mouth which
flowed in past the situation of the canal of Mazzorno,
and formed the Ramo Tramontana, was, in 1600,
twenty thousand metres (twelve miles) from the
meridian of Adria; and the southern mouth, which had
taken the place of the canal of Toi, was at the same
period seventeen thousand metres (ten miles) from that
meridian; thus the coast had become enlarged nine or
ten thousand metres (five or six miles) to the north,
and six or seven thousand metres (between three and
four miles) to the south. Between the two mouths of
which I have spoken, was part of the coast which
receded a little, called Sacca di Goro.
"It was during the same interval, between the
thirteenth and seventeenth centuries, that the great
works of the embankments of the Po were made, and a
considerable portion of the western declivities of the
Alps were cleared away and cultivated.
"The canal called Taglio di Porto Viro, determines
the progress of the alluvial deposites in the great
promontory formed by the mouth of the Po. In
proportion as their entrances into the sea are distant
the annual quantity of deposites increase in an
alarming degree, as well from the diminution of the
inclination of the waters (the necessary consequence of
the extent of the bed of the river) as from the
confinement of these waters within dykes, and by the
facilities which the recently cultivated sloping lands
afforded of carrying the soil of the mountains into the
plains. Thus the bay of Sacca di Goro was choked up,
and the two promontories formed by the

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two first mouths united into one, the present extremity
of which is thirty-two or thirty-three thousand metres
(nineteen to twenty miles) from the meridian of Adria.
Thus, in two centuries, the mouths of the Po have
gained fourteen thousand metres (nearly nine miles) on
the sea.
"Of this hasty sketch these are the results:
"1st. That at an early period, the precise date of
which cannot be ascertained, the Adriatic sea washed
the walls of Adria.
"2dly. That in the twelfth century, before a passage
had been opened at Ficarolo, for the waters of the Po,
on the left bank, the sea-shore was removed nine or ten
thousand metres (six miles) from Adria.
3dly. That the extremities of the promontories
formed by the two principal mouths of the Po, were, in
1600, before the formation of the canal of Taglio di
Porto Viro, at a mean distance of eighteen thousand
five hundred metres (twelve miles) from Adria; which,
since the year 1200, gives an extent of alluvial
deposite of twenty-five metres (twenty-seven yards one
foot and a fraction, English admeasurement.*)
"4thly. That the extremity of the single promontory,
formed by the present mouths, is thirty-two or thirty-
three thousand metres (nineteen to twenty miles) from
the meridian of Adria; whence we may conclude the
mean progress of the alluvial deposites to be about
seventy metres (upwards of seventy-six yards) per
annum for the last two centuries, which is a rapidity
greater than that of preceding ages.
"DE PRONY."

* The metre was a measure adopted during the French
revolution, of about 39 1/2 inches English measure. —
Translator

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M. de Prony having been employed by the
government to examine what remedies could be applied
to the devastations occasioned by the floods of the Po,
ascertained that this river, since the time when dykes
enclosed it, has elevated its bed so greatly, that the
surface of its waters is now higher than the roofs of
the houses of Ferrara; at the same time its alluvial
deposites have advanced to the sea with so much
rapidity, that on a comparison be tween the ancient
charts and the present state, we find that the shore has
gained more than six thousand fathoms since 1604,
which is an average of one hundred and fifty or one
hundred and eighty, and in some places, two hundred
feet per annum. The Adige and Po are now more
elevated than all the land which lies between them; and
it is only by opening again new channels in the low
lands which they formerly deposited, that we can avert
the disasters with which they now threaten us.
The same causes have produced the same effects
along the branches of the Rhine and the Meuse; and
thus the richest districts of Holland have perpetually
before them the frightful sight of their waters
suspended above their soil at a height of twenty or
thirty feet.
M. Wiebeking, director of the bridges and roads in
the kingdom of Bavaria, has written a memoir on this
progress of things, so important to be well understood
by the people and the government, In which he shows
that this property of elevating their beds belong more
or less to all rivers.
The accumulations along the coasts of the North Sea
are not less quickly formed than in Italy. We can
easily trace them in Friesland and in Groningen, where
the first dykes were constructed by the

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Spanish governor, Gaspar Robles, in 1570. A century
afterwards land had been formed in some places three
quarters of a league beyond these dykes; and the city
of Groningen itself, partly built on the ancient soil, on
a limestone which does not belong to the present sea,
and in which we find the same shells as in our coarse
limestone in the neighbourhood of Paris, is only six
leagues from the sea. Having visited these places, I can
myself testify other well-known facts, the greater
portion of which M. Deluc has already ably
explained.(1) The same phenomenon may he observed,
and with the same exactitude, along the coasts of East
Fries-land, and the countries of Bremen and Holstein,
because the parts are known where the new lands were
enclosed for the first time, and thence we can measure
what has since been gained.
This alluvial plain, so very fertile, formed by the
rivers and the sea, is in this country a gift the more
valuable; as the ancient soil, covered with heath and
turf-bogs (tourbiéres) is incapable of being made to
produce vegetation; the alluvial deposites alone supply
the means of subsistence to the inhabited cities
established along this coast since the middle age, and
which would not have reached their present opulent
state without the rich lands which the rivers produced
for them, and which they are continually augmenting.
If the extent which Herodotus assigns to the sea of
Azof, which he makes nearly equal to that of the
Euxine,(2) was expressed in less ambiguous terms, and
if we clearly knew what he meant by the

(1) In various parts of the two last volumes of his Letters
to the Queen of England.
(2) Melpom, lxxxvi

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Gerrhus(1) we should find there also strong proofs of
the changes produced by the rivers and the rapidity
with which they are effected, for the alluvial deposites
of the river could alone(2) during this epoch, that is,
for two thousand two or three hundred years, have
reduced the sea of Azof to its present size, have closed
the course of the Gerrhus, or that branch of the
Dnieper which would have united with the Hypacyris,
and with that river have thrown its waters into the
gulph Carcinites or Olu-Deignitz, and have reduced the
Hypacyris itself to nearly nothing. (3) We should have
proof no less powerful if it were ascertained that the
Oxus or Sihoun, which now disembogues itself into the
lake Aral, fell once into the Caspian sea; but we have
close at hand proofs sufficiently convincing without
being compelled to have recourse to any in the least
ambiguous, or to make the geographical ignorance

(1) Ibid, lvi.
(2) This supposed diminution of the Black sea, and the sea
of Azof has been attributed to the breaking up of the
Bosphorus, which happened at the pretended epoch of the
deluge of Deucalion; and yet, to establish the fact, recourse is
had to the successive diminutions of the extent assigned to
these seas in Herodotus, Strabo, &c. But, it is quite plain that
if this diminution had arisen from the rupture of the
Bosphorus, it must have been completed long before the time
of Herodotus, and even the period called that of Deucalion.
(3) See Rennel's Geography of Herodotus, p. 56, &c. and a
part of M. Dureau de Lamalle's work, called 'The physical
Geography of the Black Sea,' &c. At present there is only the
very small river of Kamennoipost, which can represent the
Gerrhus or Hypacyris of Herodotus.
M. Dtireau, p. 170, attributes to Herodotus the making the
Borysthenes and Hypanis discharge their waters into the Palus
Mœotis; but Herodotus only says (Meip. liii.) that these two
rivers flow together on to the same lake, that is, Liman, as at
present. He does not carry the Gerrhus and Hypacyris farther.

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of the ancients any grounds for our physical propo
sition. (1)

PROGRESS OF THE DOWNS.

We have already spoken of the downs, or those sand
heaps which the sea throws on flat shores when its
bottom is sandy. Whenever the industry of man has
failed in confining them, these downs advance inland
as irresistibly as the alluvial deposites of rivers
advance towards the sea; they drive before them pools
formed by the rainwater of the lands in their vicinity,
whose progress towards the sea they intercept, and
their advance in many places is made with alarming
rapidity. Forests, buildings, cultivated fields, are
overwhelmed by them. Those of the Bay of Biscay(2)
have already covered a number of villages mentioned
in the accounts of the middle ages, and at this time, in
the single department

(1) For instance, M. Dureau de Larnalle, in his 'Physical
Geography of the Black sea,' quotes Aristotle (Meteor, lib. 1.
c. 13) as "telling us that in his time there were many ancients,
periods and peripli, proving that there was a canal leading from
the Caspian sea to the Pains Mœotis." But Aristotle says in
the passage in question, (ed. de Duval, i. p. 545,) "From the
Paropamisus, amongst other rivers, descend the Bactrus, the
Choaspes, and Araxes, whence the Tanais, a branch of it, takes
its rise into the Palus Mœotis." Who cannot see that this
blunder, founded neither on periods nor peripli, was only the
wild ideas of Alexander's soldiery, who took the Jaxartes or
Tanais of the Transoxian for the Don or Tanais of Scythia?
Arrian and Pliny distinguish them; but this was not the case in
Aristotle's time. How then can geological arguments be derived
from such geographers?
(2) See the Report of the Downs of the Bay of Biscay by
M. Tassin, Mont de Marsan, an X.