'•tiiül
It is tlien evident that thefc valleys are the true and only cxtenfive channels formed by
the iinpetuoiity of the fea at the time of the grand débâcle, or revolution, occafioned by ils
fuddcn tranfpofition, which operated fo forcibly on our continents ; and that they have
been, and are ftill brought to their prefent ftate of pcrfedtion, by their rivers. Indeed the
great analogy among the formation, difpofition, and dhef t ion of the different iirata, and
the extreme abruptnefs of the formidable peaks which ihelter or hang on each fide of
them, feem to be unqueftionable proofs of the above aflertion, which will be fupportcd by
feveral examples in tlie courfe of the prefent work.
Thc fe obfervations cannot, however, be applicable to tire fmaller or tranfverfal
valleys which terminate in the fecondary ones, tliofe being moilly watered by impetuous
torrents, which at ceitain feafons of tlic year fweep over the rocks with irrefiilible violence,
and are on that account called by the mountaineers Nant ; for it is vifible that their excavations
are wholly the efFea of thefe torrents, which have by degrees, or from time to time,
made their way through the different fpecies of rock in which their Ijcds are formed.
Wha t with the inceflant friftion of thefe waters, and their continual aélion of undermining
the bafe of the lateral rocks, joindy widi the efFeAs of the froft, which on thofe mountains
is fo extremely intenfe, that the water which generally filters during the hot fummer
months through their ftrata, freezes to fuch a degree, and to fuch a deptli, as to detach
enormous maffes of rock.
Thefe operations of nature are continually feen in mountainous countries ; and, indeed,
there are feveral villages in the Alps where they make ufe of the mere eifedt of congelation
to loofen ftrata from the mountains for their mills, &c. mofliy of the fpecies of
lapis molitoris.
T h e tranfverfal valleys are alfo, in general, filled with large pieces of various kinds of
rock, fcattered without order, and in many places confufedly heaped together, being vifibly
fragments detached from the lateral mountains.
They likewife differ from the fecondary ones, being more contraéted, and extremely
crooked, their fides abrupt, and the di r e a ion of their ftrata correfponding with each other ;
whereas, in the fecondary ones, they are for the moft part anomalous. But in the tranfverlal,
the faliant, or prominent angles, arc uniformly oppofed to the concave ones ; and the
heights of the two fides are nearly the fame, as Baf fon has juftly obferved in his Theory
of the Earth, on the Formation of the Strata, or Beds, in the Rivers. Vol. I. Article
7th.
This fingularity, however, appears merely to relate to the fmaller valleys, and not to the
primilive ones, as that fcientific naturalilt has advanced.
It is therefore evident, as I have before obfei-ved, ift. That the moil: cxtenfive valleys, as
Lombardy, &c. owe their origin wholly to the effeils of the fea, in its retreating and fubf iding;
and their improved fiate and increafe to the continual atteriffements or depofitions of the
rivers. 2d. Tha t the fmaller valleys, as Mai ra, Stura, Grena, &c. owe tlieirs to the fudden
and powerful adtion of the fame element; and their improved fl:ate to the ruins and continual
decompofitions of the neighbouring moimtains, occafioned by rain, fnow, froft, &c.
as alfo to the rivers or torrents which water them. 3d. Tha t the fmalleft, or tranfverfal
valleys, have been formed folely by the efFe¿t of the torrents which flow through their
centre. I ihall here add another obfervalion which I have made in feveral parts of the Alps,
and which I am defirous of having purfued by thofe who arc more equal to the talk than
myfelf, which is, diat as valleys In general conti-atft in proportion as they approach the
mountains from whence they take their origin, I have noticed,. that the convergence of
their adjacent hills, or mountains, is nearly in proportion to the elevation of their foil
above the level of the f e a ; for inftance, the city of Cremona, which is fituated in the
wideft part of the plain of Lombardy, the medium or general inchnation of the foil, is (as
I have already ilatcd) equal to one foot on fix thoufand, which is as fmall a declivity as
can well be for the draining of the waters; whereas at Verua, where the fame plain is confiderably
contradled, the inclination, or declivity, is nearly fix times greater, though the
diftance from thence to the fea is not as far again as it is from Cremona. T h e fame obfcrvation
may likewife be made concerning Coni, where the local fituation is only thirtynine
miles from Tur in, and fifty from Vcrua, yet is neverthelefs one thoufand five hundred
and twelve feet more elevated than that capital; for I found by my barometrical obfervations,
that the efplanade at Coni, from the gate of Nice at the extremity of the glacis, is
three hundred and feventy-five toifes, or two thoufand two hundred and fifty feet above the
level of the fea. Now as Turin, according to Monf. de Luc's obfervations, is one hundred
and twenty-three toifes, or feven hundred and thirty-eight feet above the fame level, the
refult of this calculation mufl: be one thoufand five hundred and twelve feet, which is a
confidcrable diffei-ence, confidering the very fmall diftance betwixt thofe cities; but here,
indeed, the valley is parücularly cont raaed. I am Üierefore of opinion, that in order to
acquire an exaA and determined knowledge, or at leaft as nearly as it can be obtained, of
the relation which exifts between the width and elevation of the foil of the primitive and