a environ 4 degrés de latitude N. et 304 de longitude, prise de l'île de
Fer, est située au pied et sur le penchant d'une montagne escarpée qui
la couvre à l'est; elle domine une plaine de douze lieues de largeur
sur une longueur indéterminée et très considérable, qui présente toute
l'année le riant tableau des plus belles campagnes de l'Europe: les
coteaux toujours verts où les troupeaux bondissent, les prairies
couverts de bétail, les champs bien cultivés, les maisons de campagne
agréables, les hameaux, les villages, les vergers, les jardins, montrent
à la fois, les fleurs du printemps et les fruits de l'automne, que
l'abondance des pluies ou les sécheresses retardent ou avancent
quelquefois mais dont l'éternelle durée bien loin d'inspirer le plaisir,
et d'offrir l'attrait piquant de la nouveauté qui fait le charme de ces
saisons dans nos climats, amène bientôt l'indifférence pour une beauté
toujours le même, pour des agrémens qui ne changent pas.
«Ce climat est d'ailleurs si étrange et tellement constitué, que quand
on est au soleil, on se trouve bientôt incommodé de sa chaleur; est on à
l'ombre? on se sent pénétré d'un air subtil et froid qui transit.
«A trois lieues à-peu-près à l'ouest de la ville, passe la rivière de
Bogota qui, après avoir reçu les eaux de toute la plaine, la rivière de
Serrefuela et les torrens qui se précipitent de la chaîne de montagnes,
dirige son cours paisible vers Tekendama à sept ou huit lieues au
sud-est à-peu-près; c'est-là que ces eaux rassemblées coulent entre
une suite de rochers granitiques, dont le plain incliné accélère leurs
vitesse; elles n'offrent bientôt plus qu'un courant rapide, étroit et
profond qui, au moment de sa chûte, rejaillit sur un rocher placé plus
bas que son lit, d'où il tombe dans une abîme dont on n'a pu jusqu'ici
mesurer la profondeur; c'est la cataracte ou saut de Tékendama.
«Des trous pratiqués dans le roc par les anciens aux endroits les plus
commodes pour voir toute l'étendue de cette chûte prodigieuse, donnent
le moyen d'observer sans risque la continuation des rochers qui
s'avancent à droite et à gauche et annoncent par leurs hauteur qu'avant
le passage que les eaux semblent avoir forcé, la plain de Santa Fée
n'étoit alors qu'un lac d'une très-grand étendue: une tradition
constante du pay, mais peu vraisemblable, porte que les Indiens ont
creusé cette espèce de canal.
«Il y a quelques-uns de ces trous d'où l'on voit confusément le lieu où
finit cette chûte d'eau effroyable; la rivière qui en provient n'offre
plus qu'un foible ruisseau, dont le cours presqu'insensible se perd
parmi les plantes qui croissent sur ses bords; ainsi disparoissent
dans l'éloignement les masses les plus énormes: quelques espèces de
perroquets et d'autres oiseaux de pays chauds, qui habite cette vallée
profonde et inabordable de ce côté, s'élèvent assez quelquefois pour
pouvoir être remarqués d'en-haut; mais le froid subit de ces montagnes
qu'ils craignent, est une obstacle invincible qu'ils ne franchissent
jamais: pour jouir commodément de ce point de vue, à la fois admirable
et effrayant, il faut choisir un jour calme et serein, entre sept à huit
heures du matin.
«Il est necessaire de prendre un long détour et cheminer pendant toute
une journée, presque toujours à travers des rochers et des précipices,
pour parvenir au pied de cette cataracte; on est alors étrangement
surpris de voir que cette rivière à peine sensible d'en haut, soit
encore un torrent prodigieux, dont la chute en cascades dans une angle
de 45 degrés, offre pendant l'espace d'une grande demie lieue des amas
de rochers entassés au hazard, que frappe et détruit sans relâche le
plus bruyant conflict des eaux; c'est après cet espace que le courant,
devenu plus paisible permet encore de comparer la rivière de Bogota à ce
qu'est la Seine dans l'été.
«Un phénomène bien extraordinaire et qui sert en même tems à donner la
plus haute idée de l'étendue prodigieuse de cette cataracte, c'est que
sa chute commence dans un pays très-froid où il gèle souvent pendant
la nuit, et finit dans un autre où la chaleur, égale à nos beaux jours
d'été, offre la végétation prompte et facile de toutes les plantes des
pays chauds: seroit-ce le passage subit de l'air du chaud au froid qui
occasionneroit ces gelées blanches, à-peu-près comme celles qui ont lieu
dans nos climats aux approche de l'hiver et à l'entrée du printemps? car
on en éprouve rarement dans la plane.
«Une autre particularité remarquable de ce pays, c'est le défaut de
poisson dans toutes les rivières qui l'arrosent: on en trouve cependant
dans celle de Bogota où les autres rivières viennent se rendre; mais
c'est une seule espèce très-peu abondante, que les Espagnols appellent
el Capitan, ou le capitaine; la plus grande longueur de ce poisson est
d'environ un pied, sur six pouces de grosseur; il vit dans les eaux
troubles et vaseuses de cette rivière, et jamais dans les eaux claires;
il est gras et excellent à manger: son genre est celui de la _mustelle
fluviatile de France_ et le _Gades_ de Linné.
«Il est certain cependant que les poissons de toutes les sortes abondent
dans les grandes rivières de l'Amérique méridionale et notamment dans
celle de la Magdelaine; ne pourroit-on pas supposer d'après cela, que
puisque toute communication des eaux de tout le pays élevé de Santa Fée
est interrompue avec cette dernière par le saut de Tekendama, ces mêmes
eaux n'ont pu en être peuplées comme celle-ci paroissent avoir été, au
moins en partie, par la mer. Ce même défaut de poisson se remarque dans
la plus part de lacs et des rivières des Cordillères, probablement par
une cause semblable; il n'y en a point dans les deux lacs assez étendus
qui sont près de la ville d'Hyvarra dans la province de _Quito_, non
plus que dans les rivières de la province de Pastos.
«On peut objecter qu'une temperature toujours froide comme celle
de Santa Fée, joint à la limpidité et la rapidité des torrens des
Cordillères, suffisent pour écarter les poissons, de même que cela
arrive dans plusieurs rivières de l'Europe.
«Cette objection seroit vraie pour la plupart des torrens des
Cordillères, mais on observera que la rivière de Bogota quoique froide,
est presque stagnante dans bien des endroits, et coule toujours sur de
la vase qui en rend les eaux bourbeuses; il est à présumer que, s'il
étoit possible d'y tranporter des poissons de nos rivières, ils y
réussiroient aussi bien que les autres productions de l'Europe qui se
sont naturalisées dans ce pays. Quant à la température constante froide
de ces eaux, qui pourroient paroître s'opposer au développement des
oeufs du poisson qui habite les rivières des pays chauds, on y respondra
par le fait suivant.
«A vingt lieues environ au nord de Santa Fée à la même élévation et à la
même température, est un grand lac où l'on trouve des îles habitées,
et qui en a paru assez grand pour être indiqué dans les cartes
géographiques, si on en savoit les dimensions; c'est le lac de
Chiquinquira assez poissonneux pour y faire des pêches abondantes, parce
que la rivière qui en sort n'est pas interrompue par des sauts dans son
cours jusqu'à la rivière de la Magdelaine; cependant les espèces de
poissons qu'on trouve dans ce lac ne sont pas aussi variées que dans
cette grande rivière, sans doute à cause de la rapidité du courant, que
le poisson ne remonte pas également bien.
«Lorsqu'on gravit sur les montagnes escarpées qui dominent la ville de
Santa-Fée, on ne rencontre, depuis leur base jusqu'à leurs sommets,
terminés par des rochers de granité, que des bruyère, des fougères,
quelques plantes sauvages, etc. et pas un arbre qu'on puisse seulement
appeler un boisson excepté dans quelques gorges à l'abri de courans
d'air, où l'on en voit quelques-uns dont les plus grands, n'égale pas
nos prunières; cette végétation engourdie paraît être due au froid vif
et continuel qu'il fait sur ces montagnes; car plus on monte, moins elle
se développe, et enfin finit par cesser tout-à-fait: on remarque à la
moitié de la hauteur d'une de ces montagnes (à une demi-lieue à peu-près
de la ville) une mine de charbon de terre en filon que renferme une
rocher entrouvert, dans une situation verticale[27], les torrens y
roulent de l'or.»
[Footnote 27: Here is an evidence that those vertical strata, now
elevated into the highest stations upon the earth; had been formed
originally of the spoils of the land, and deposited at the bottom of the
sea.]
«Si l'on descend dans la plaine, si l'on remonte sur les collines,
toutes à-peu-près de la même hauteur qui sont entièrement séparées
des montagnes voisines, et situées dans la direction ou courant des
rivières, on remarque aisément qu'elle sont les restes d'une plaine
antérieure que les eaux ont dégradée. Au lieu de ces forêts, et de
ces boissons qui surchargent bientôt nos campagnes lorsque la main de
l'homme cesse de les cultiver, un gazon touffu couvre la plaine et les
collines de Santa-Fée d'une verdure agréable sans nul arbrisseau qui
puisse en altérer l'uniformité, où les graminée, le plantain, le
scorçonnaire, le trèfle, le marrube, la pimprenelle, le pourpier, la
patience, le chardon, le raifort, le cresson, la chicorée sauvage, la
jonquille, la marguerite, le fraisier, la violette, le serpolet, le
thym, et mille autres plantes d'Europe et particulières à ce pays,
offrent les variétés les plus piquantes par la beauté des fleurs et
I'odeur de leurs parfums; des rochers qu'entourent le rosier ou la
ronce, et quelques cavernes que le hazard presente sur ces mêmes
collines, en rendent l'aspect pittoresque et délicieux.»
Here is a picture of a country such as we might find in Europe; only it
is placed under the line, and elevated above the highest of the frozen
summits of the European Alps. We may observe that the same order of
things obtains here as in every other place upon the surface of this
earth; mountains going into decay; plains formed below from the ruins
of the mountains; these plains ruined again, and hills formed in their
place; rivers wearing rocks and breaking through the obstacles which had
before detained their waters; and a gradual progress of soil from the
summits of the continent to the border at the sea, over the fertile
surface of the land, successively destroyed and successively renewed.
Here are to be observed two states of country along side of each other,
the plain of the Bogota, and the Valley of the Madalena. The courses of
the two rivers show the direction of those ridges of mountains which had
been raised from the deep; they run south and north, as do those valleys
which they drain. At this place we find the valley of the river Cauca,
and the valley of the Magdalena parallel to each other, and also to this
high plain of the Bogota. Now the waters of this high country, instead
of running northward to the sea, as do those of the two valleys below,
run both from the south and north until, uniting together, they proceed
westward, break the rampard of granite rocks at Tekendama, and fall at
once from the high plain down into the valley of the Madalena. Those
water formed plains which we perceive subsisting at unequal levels
immediately adjoining to each other, while they present us with a view
of the degradation of the elevated earth, at the same time illustrate
the indefinite duration of a continent; for, we judge not of the
progress of things from the actual operations of the surface, which
are too slow for the life of man, and too vague for the subject of
his history, but from the state of things which we contemplate with a
scientific eye, and from the nature of things which we know to be in
rule.
In like manner the horizontal situation of the solid strata in the
mountains of that low country, while those of the high country are more
or less inclined, afford the most instructive view of the internal
operations of the globe, by which the Andes had been raised from the
bottom of the sea, and of the external operations of the earth by which
mountains are formed by the wasting of the elevated surface.
With this description of those high plains upon the north side of the
line, let us compare what D. Ulloa has said upon the same subject in
describing the continuation of that high country to the south. I shall
give it from the best French translation.
It is after describing a cut or narrow ravine in the solid rock with
perpendicular sides, about forty yards deep, in which a rivulet runs and
the road passes.
«Cette excavation est, en petit, une modèle des vastes _Quebradas_ ou
profondeurs, et fait comprendre leur origine: elles ne pouvoient être
que semblables à celle-ci: tout s'y est passé de même, ou plus tôt
ou plus tard. Les flancs en ont été plus ou moins perpendiculaires,
jusqu'au moment où ils se sont affaissées, et ont formé des plains
inclinés, lorsque l'eau faisant de plus profondes excavations, eut miné
la base qui les soutenoit. Ne pouvant plus alors persévérer dans leur
premier état, les terrains ont croulé, et ont pris l'inclinaison qu'ils
ont conservée depuis. La même chose arrivera nécessairement à ce passage
de _Conaïca_ lorsqu'avec le laps du tems, les effets des pluies, de
gelées, des rayons solaires, auront fait tomber en ruine ces parois,
quoique de roche rive; car ses agens puissans font sentir leur énergie
aux corps les plus durs. Ainsi les bords du _Chapilancas_ perdront
insensiblement la régularité de leur distance, de leurs côtés rentrans
et saillans, après l'avoir peut-être conservée plus long tems que
d'autres excavations, parce que c'est une pierre dure, qui n'est mêlée
d'aucune veine de terre movible. Nous pouvons le croire sans hésiter;
car ce n'est que le seul frottement de l'eau qui a excavé ce lit jusqu'à
la profondeur qu'il a. Mais le tems, qui réduit les roches les plus
dures en sablon, ira toujours en élargissant la partie inférieure, par
son action continuelle et insensible: aussi voit-on ce ruisseau rouler
de petites pierres qui se détachent sous les eaux, comme on en apperçoit
dans la plaine où il les entraîne, en sortant de la montagne, pour se
décharger dans une terrain plus spatieux.
«Que ce canal ait été excavé à cette profondeur par l'effet continuel
du frottement des eaux, ou qu'il a été ouvert par une secousse de
tremblement de terre qui fit fendre la montaigne, de sorte que le
ruisseau qui couloit d'un autre côté, se soit jetté de celui-ci. il est
certain que cette ouverture profonde est postérieure à l'arrangement que
les terrains eurent après le déluge; et que c'est ainsi que ces énormes
_Quebradas_ de la partie méridionale de l'Amérique, se sont formées
avec le tems, par le frottement du cours rapide des eaux. En effet, on
observe que la force avec laquelle s'écoulent toutes les eaux de
cette partie du globe, suffit pour arracher des roches d'une masse
extraordinaire. C'est pourquoi l'on voit en certaines parages des
marques évidentes de leurs excavations profondes au milieu même des lits
de ces eaux. Ce sont des cubes d'une grandeur énorme, qui n'ont pu être
détachés avec la même facilité que les parties contiguës. La rivière
_d'Iscutbaca_, qui coule près d'une hameau de même nom, nous présente
dans son lit une de ces masses, dont la forme est précisément celle
d'une cube. Lorsque l'eau est basse, ce cube s'élève à sept ou huit
_varas_ au-dessus du courant: chaque côté porte douze _varas_ de face.
Mais ces masses, et autres moindres de différentes formes, qui se voient
dans les eaux, ne peuvent être arrivées à cet état, sans que l'eau les
ait dégarnies peu-à-peu des pierres, des sables que les envelopoient, et
qu'elle a arrachés de tous côtés pour les laisser isolées; or elles se
maintiendrons dans cette position, jusqu'à ce que les eaux, cavant
de plus en plus, rencontrent enfin à la base des veines de matières
friables et dissolubles, qu'elles pénétreront et qu'elles emporteront,
en détruisant l'assiette sur laquelle posent ces masses jusqu'alors
_inamovibles_. Une crue d'eau considérable, et qui ne laissera plus
paroître qu'une _varas_ de cette masse, pourra dans ce tems-là
l'arracher, et la faire rouler; mais ce mouvement, et les chocs qu'elle
éprouvera de la part d'autres masses moins grosses, suffiront pour
en briser les parties saillantes, et la réduire en parties moins
volumineuses, qui rouleront avec plus de facilité; et qui par cette seul
cause diminueront encore. C'est à cette cause qu'on doit attribuer ces
quantités prodigieuses de pierres répandues ça et là sur les bords de
ces eaux, de même que ces roches enormes qu'on y voit détachées, et que
jamais les forces humaines n'auroient pu mettre en mouvement.
«Mais pour donner une idée quelconque de la profondeur de ces
excavations, relativement au terrain ou au sol habitable de la partie
haute de l'Amérique, il est à propos de rapporter quelques expériences.
«Guancavelica est une bourgade, ou un corps municipal, situé dans une de
ces profondeurs, formées par différentes suites d'éminences. Le mercure
du baromètre y descend, et s'arrête à dix-huit pouces une ligne et
demie. Sa plus grande variation y est de 1-1/4 à 1-3/4. Sa hauteur est
donc de 1949 toises, ou 4536-2/3 _varas_ au-dessus du niveau de la
_mer_. Au haut du mont où se trouve la mine de mercure, mont qui est
habitable par-tout, et qui est immédiatement surmonté par d'autres,
autant qu'il s'élève au-dessus de Guancavelica, le mercure descend et
s'arrête à 16 pouces 6 lignes. Sa hauteur est donc de 2337-2/3 toises,
ou de 5448 varas au-dessus du niveau de la mer. Ainsi les eaux ont
encore fait cet autre excavation comme il est facile de le voir par des
indices manifestes. On remarque en effet dans la partie voisine de leur
lit, des roches détachées, toutes semblables à celles qui sont au milieu
des eaux; ce qui prouve que les eaux ont été au même niveau à une époque
beaucoup plus ancienne, et qu'elles ont excavé le sol, a force d'en
arracher les parties agrégées.
«Ces terrains sont couverts par un si grand nombre de courans, qu'il
n'en est aucun ou l'on n'en aperçoive, soit dans des ravins, soit entre
des montagnes. J'ai observé que la superficie des terrains qui en
avoisine les lits, est plus unie aux confluens, où plusieurs de ces
courans se réunissent. Cela vient de ce que l'éminence, qui se trouve au
confluent, paroît avoir été diminuée à la partie où elle a du former
une pointe saillante, à mesure que les eaux l'ont rongée de l'un ou de
l'autres côté, en continuant leurs excavation. Ces surfaces planes
sont comme par étages, les unes plus hautes que les autres, et se sont
insensiblement formées, selon que l'eau s'est plus ou moins arrêtée à
différente hauteur, pendent qu'elle creusoit ces lits. On observe, au
contraire, que les bords élevés dans ces courans, n'ont presque point
de largeur dans les endroits où l'eau a pu suivre son cours
très-directement. C'est cependant sur ces bords étroits et escarpées que
se trouvent pratiqués les chemins par où l'on passe. Le danger y est
très grand: car à peine un animal peut-il poser le pied. Toutes les fois
que le courant fait un détour, la surface des bords a plus de largeur;
cependant moins que lorsque plusieurs se réunissent. Un voit facilement
pourquoi. L'eau forcée de se détourner, s'éloigne plus de la rive que
quand elle va en ligne droite, et ronge ainsi le côté saillant sur
lequel elle fait son détour, et qui en devient comme le centre.
«On peut conclure de ce que je viens de dire, à quelle élévation est
la partie haute ou montagneuse de l'Amérique, relativement à la partie
basse, et qu'il y a des excavations extrêmement profondes; car elles
ont, comme je l'ai déjà dit, 1769-2/3 varas perpendiculaires, ou même
d'avantages: cependant elles ont assez de surface pour devenir le local
de nombre d'habitations fort peuplées, qui en tirent tous les produits
nécessaires à la vie. Parmi ces _Quebradas_, il en est de plus étendues
ou de moins profondes que les autres. Or, c'est en ceci que cette partie
du monde se distingue de toutes les autres.
«Mais il est indifférent pour mes vues que ces vastes ouvertures soient
l'effet des courans d'eau, ou de toute autre cause. Ce que je me
propose, est uniquement de montrer qu'elles sont d'autant plus profondes
et plus vastes, que ces terrains sont immensément hauts.»
M. Monnet considers the natural operations of water, upon the surface of
the earth, as truly forming the shape of that surface; but he draws some
very different conclusions from those which I have formed. It is in his
_Nouveau Voyage Minéralogique, fait dans cette partie du Hainault connue
sou le nom de Thiérache._ Journal de Physique, Aoust 1784.
«Il ne faut pas s'attendre à trouver dans ce pays des hautes montagnes
qui frappent la vue de loin; c'est seulement un pays dont l'élévation
est générale sur tout ce qui l'entoure, et est coupé profondément par
des vallées ou ravin, ouvrage des eaux, qui, la comme ailleurs, ont
use et coupé peu-à-peu les terrains et les roches les plus dures, pour
s'ouvrir un passage; et peut-être pourroit-on dire; si la diminution des
eaux n'étoit pas trop sensible, qu'un jour ce pays offrira des montagnes
hautes est escarpées comme tant d'autres, après que les eaux auront
creusé, pendant des milliers de siècles, ses gorges, ses ravins, et
diminué la largeur des masses de terrain qui sont entr'eux.
«Quant à present, on ne peut y voir que de petites montagnes, ou plutôt
des bosses de terre, avec des platures plus ou moins considérables à
leurs sommets, avec de côtés coupées plus ou moins obliquement, ou plus
ou moins droites. Ce qu'on y trouve de singulier c'est que ces petites
montagnes sont presque toutes plus basses que les plaines qui les
avoisinent, encore ne sont elles que dans la partie calcaire.
«La plus profonde tranchée de ce pays est, sans contredit, celle ou
coule la Meuse, qui, malgré la dureté des roches d'ardoise et de quartz
au travers desquelles elle passe, a coupé le terrain depuis Charleville
jusqu'â Givet, à une très-grande profondeur. Dans cette distance, on
voit presque par-tout les côtés coupées presque à pic sur la rivière, de
deux à trois cents pieds de hauteur perpendiculaire; et comme c'est une
règle générale, que plus les côtés sont coupées droites, moins elles
sont distantes l'une de l'autre, on conçoit que le canal de la Meuse,
dans cette étendue de terrain, doit être fort étroit, eut égard à
beaucoup d'autres où il coule un bien moindre volume d'eau. Cela
n'empêche pas qu'on n'y aperçoive des marques de la règle général
que fait l'eau, et n'y ait taillé des angles saillans et des angles
rentrans, qui sont très-grands en certains endroits. Nous verrons que
Revin et Fumai, deux lieux principaux des bords de la Meuse, sont situés
sur deux de plus grandes de ces ouvertures où se trouvent des platures
assez vaste pour permettre, outre un emplacement considérable pour les
maisons, l'établissement de beaucoup de jardins, et même des pièces à
grain et des prairies. Aussi, quand on arrive sur la tranchée de la
Meuse, les lieux et les terrains cultivés qu'on voit dans son fond,
paroissent comme séparés sous les autres et comme dans un autre pays.
«Les autres coupures ou ravins de ce pays, quoique moins profonds,
offrent cependant cette singularité, remarquée déjà ailleurs, que leurs
grandeurs et profondeur ne sont point du tout proportionnées au volume
de l'eau qui y coule.
«Le massif sur lequel est situé Beaumont, est coupé presque
perpendiculairement à l'ouest, sud-ouest et cette coupe en fait de ce
côté-là un rempart inaccessibles, ayant plus de 100 pieds de hauteur.
Quand j'ai considéré cette grande coupe, et le détour que fait la petite
rivière qui coule au bas de ce massif, je n'ai pus me refuser à croire
qu'il n'y avoit en là un bien plus grande courant d'eau, qui a battu et
miné ce massif, en s'y brisant avec force; car on ne peut supposer, avec
quelque vraisemblance, que cet ouvrage ait été fait par le volume d'eau
qui y coule actuellement: et il ne faut pas s'étonner de ce disparate;
par-tout vous le trouverez; ce qui démontre évidemment que la quantité
d'eau diminue insensiblement, et que la partie solide de notre globe
augmente à proportion que la partie liquide diminue; et s'il faut encore
étendre ce principe, j'ajouterai, que par-tout vous verrez les bornes
de la mer et des rivières reculées; par-tout vous trouverez d'anciens
courans d'eau desséchés, et même des rivières considérables, à en
juger par les collines ondulées qu'on voit encore. Mais cette partie
essentielle de la minéralogie qui est effrayante par les conséquences
qu'elle presente, et qui peut influer sur le système général du monde,
sera étendue un jour dans un autre memoire, où je décrirai d'anciens
cours de rivières de la France, qui n'existent plus. J'espère fair voir
alors, appuyé par les faits que me fournira l'histoire, que les rivières
et les fleuves actuels ont été plus volumineux qu'ils ne le sont
maintenant, et qu'il existoit en France un grande nombre de vastes lacs,
comme dans l'Amérique Septentrionale, et dont à peine il nous reste des
traces aujourd-hui.»
This opinion of M. Monnet, concerning the diminution of water upon the
earth, does not follow necessarily from those appearances which he has
mentioned. The surface of the earth is certainly changed by the gradual
operations of the running water, and it may not be unfrequent, perhaps,
to find a small stream of water in places where a greater stream had
formerly run; this will naturally happen upon many occasions, as well
as the opposite, by the changes which are produced upon the form of
the surface. Likewise the conversion of lakes into plains is a natural
operation of the globe, or a consequence of the degradation of the
elevated surface of the earth, without there being any reason to suppose
that the general quantity of running water upon the land diminishes,
or that the boundaries of the various seas are suffering any permanent
removal.
Whether we examine the Alps in the Old World, or the Andes in the New,
we always find the evidence of this proposition, That the exposed parts
of the solid earth are decaying and degraded; that these materials are
hauled from the heights to be travelled by the waters over the surface
of the earth; and that the surface of the earth is perpetually changing,
in having materials moved from one place and deposited in another. But
these changes follow rules, which we may investigate; and, by reasoning
according to those rules or general laws, upon the present state of
things, we may see the operation of those active principles or physical
causes in very remote periods of this mundane system, and foresee future
changes in the endless progress of time, by which there is, for every
particular part, a succession of decay and renovation.
CHAP. XIII.
_The same Subject continued._
The Chevalier de Dolomieu, in his most indefatigable search after
natural history and volcanic productions, has given us the description
of some observations which are much calculated to put this subject in a
conspicuous point of view. I give them here as examples of the operation
of water wasting the land and forming valleys in a system where every
thing is tending to the wisest end or purpose; but they are no less
interesting as proper to give us a view of the mineral operations of
the globe. That therefore which, according to the order of the subject,
ought to be cited in another part of this work, is here necessarily
mixed in the narrative of this natural historian.
There is, upon this occasion, such a connection of the facts by which
the mineral operations of the earth, either consolidating the materials
deposited at the bottom of the sea, or elevating land by the power of
subterraneous heat, are to be understood, and of those by which the
operations of the surface are to be explained, that while they cannot be
separated in this narration, they throw mutual light upon each other.
It is in his Mémoire sur les Volcans éteints du Val di Noto en Sicile.
Journal de Physique, Septembre 1784.
«Je trouvai les premiers indices de ces volcans, en allant de Syracuse
à Sortino, à une lieue de cette ville, au fond du profond vallon qui y
conduit. Quelques morceaux de laves entraînés et arrondis par les eaux
m'annoncèrent d'avance que j'allois entrer dans un pay volcanique. Mon
attention se fixa bientôt après sur un courant de laves que je vis
sortir d'une montagne calcaire qui étoit sur ma droite, il étois coupé
par une vallon dont les eaux couloient sur un sol calcaire, et alloit
se perdre dans le massif également calcaire qui étoit sur ma gauche.
Je passai en suite alternativement sur des matières calcaires et
volcaniques, pour arriver à Sortino, ville baronale bâtie sur une
montagne calcaire qui domine la vallon, et qui lui presente des
escarpemens de plus de 200 toises d'élévation, dans lesquels les banc de
pierres dure sont horizontaux, et exactement parallèles.»
Here, it is to be observed, are horizontal beds remaining, which give a
measure of what had been abstracted by some cause, which is our present
subject of investigation. The Chevalier proceeds:
«Les environs de Sortino m'offrirent des phénomènes et des singularités
dont l'explication me parut difficile, et qui tinrent pendant longtemps
mon esprit en suspens. Je vis d'abord les matières volcaniques
ensevelies sous des bancs horizontaux de pierres calcaires,
très-coquillières, contenant sur-tout une infinité de madréporites,
quelques-uns d'un volume énorme. Je vis ensuite des hauteurs dont les
sommets seuls étoient volcaniques, et les noyaux calcaires, sans que
les laves qui couronnoient ces sommets eussent communication avec
aucun courant, et eussent d'autre étendue que le plateau qu'elles
recouvroient. Ces laves n'avoient pu être formées où je les voyois;
elles étoient venues d'ailleurs; mais d'où et comment? etc. Je me
déterminai à consulter les montagnes les plus hautes, qui étoient à
quelque distance. J'en vis de loin plusieurs dont la forme étoit à
peu-près conique, et dont les sommets étoient pointus; elles étoient
vers le nord, ou nord-ouest de Sortino, dans la direction de l'Etna, qui
terminoit mon horizon, à une distance de 13 ou 14 lieues, etc.
«La montagne Saint-George, une des plus hautes de tout le canton du
sommet de laquelle je pouvois prendre une idée topographique de tous le
pays, qui domine tout ce qui entoure, à l'exception de quelques pics
calcaires qui lui sont au sud; (tel que celui de la montagne de
Boujuan); cette montagne, dis-je, dont la forme est conique, et qui est
isolée par des vallées, dont le sol lui étoit sur-abaissé de 3 ou 400
toises, a sa base calcaire. Sur cette première assise repose une couche
volcanique, ensuite une autre tranche volcanique calcaire, à laquelle
succède un sommet formé d'une lave dure. Une autre montagne auprès
du fief de la Copodia, également conique, est toute volcanique, à
l'exception d'une couche de pierre calcaire dure et blanche, qui la
tranche à moitié hauteur parallèlement à sa base. Quelques montagnes où
les couches volcaniques ou calcaires sont plus ou moins nombreuses. La
montagne de Pimalia est volcanique à sa base et calcaire à son sommet;
et enfin la montagne isolée sur laquelle est bâtie la ville de
Carientini est moitié calcaire et moitié volcanique: mais ici la
division des deux substances se fait par un plan verticale, etc. Après
être arrivé à cette limite des volcans, dont je poursuivois le foyer,
je pris du côté de l'est; je suivis jusqu'à Melilli les hauteurs qui
accompagnent la vallée de Lentini, et qui dominent la plaine d'Auguste;
et cheminant à mi côté je vis déboucher du milieu des montagnes
calcaires, qui, réunies par leur base, ne forme qu'une même groupe, sous
le nom de monts Hybleens, _Colles Hyblei_, plusieurs courans de lave qui
se terminent comme s'ils avoient été coupés sans avoir eu le temps de
descendre dans la vallée, et de s'incliner pour en prendre la pente.
Plusieurs de ces courans sont cristallisés en basaltes prismatiques; on
en voit de très-belles colonnes au-près de Melilli. Au delà de cette
ville jusqu'à Syracuse, on ne voit plus de traces de volcans, et les
escarpemens en face du golfe d'Auguste n'offrent qu'un massif calcaire
en bancs horizontaux, etc.
«Je revins a Sortino, et en allant visiter l'emplacement de l'ancienne
Erbessus, connue maintenant sous le nom de Pentarica, je traversai deux
gorges d'une extrême profondeur, dont les encaissemens, taillés presque
à pic, ont plus de 600 pieds d'élévation, etc.»
The Chevalier then found, in the mountain of Santa Venere, an extinct
volcano; and proceeds in his Memoir to give some explanation for those
appearances, as follows:
«Je ne pus pas douter que cette montagne ne fût le volcan que je
cherchois, et qui avoit répandus ses laves à une très-grande distance
autour de lui, sur-tout dans la partie de l'est; mais il me restoit à
résoudre le problème de la formation des montagnes isolées et coniques,
mi-parties volcaniques et calcaires, qui ne tiennent à aucune courant,
et qui sembloient n'avoir aucune relation directe avec mon volcan.
L'étude de la montagne Santa-Venere, et des pays circonvoisins, m'apprit
que ce volcan s'étoit élevé au milieu de la mer qui alors occupoit nos
continens, que sa tête seule s'étoit soulevée au-dessus du niveau des
eaux. Je fus convaincu que, lorsqu'il répandoit autour de lui des
torrens de matières enflammées, la mer entassoit des dépôts calcaires;
que chaque nouvelle éruption trouvoit un sol plus élevé, sur lequel elle
se répandoit; que bientôt les nouvelles matières volcaniques étoient
ensevelies sous de nouveaux dépôts, et qu'ainsi, par l'entassement
successif et régulier des produit du feu et des dépôts de l'eau, s'étoit
formé un énorme massif, á sommet aplati et horizontal. Ce massif
occupoit tout le centre du Val di Noto, recouvroit de plusieurs
centaines de toises le sol sur lequel s'étoit répandu les premières
laves, et fut divisé, morcelé et dégradé par les courans ou par le
ballottement des eaux, lors de la grande débâcle du de la catastrophe
qui changea l'emplacement des mers. Les vallons et les gorges qui se
formèrent au milieu de ce massis, séparèrent les laves de la montagne à
qui elles appartenoient, coupèrent les courans, et façonnèrent, avec les
débris de ce massif des montagnes de toutes les formes, mais la majeure
partie conique, ainsi qu'on peut le voir journellement, lorsque, dans
un terrain argilleux et submergé l'eau, se retirant avec précipitation,
excave par-tout où elles trouve moins de resistance, creuse les premiers
sillons qu'elle a tracés et forme des petits cônes, dont les sommets
sont à la hauteur du sol sur lequel reposoient les eaux. Les parties où
les laves avoient coulé successivement dans la même direction, les unes
au-dessus des autres, ont donné naissance aux montagnes dans lesquelles
les couches volcaniques et calcaires se succèdent parallèlement. Celles
sur lesquelles aucunes laves ne se sont portées, n'ont produit que des
montagnes totalement calcaires que se trouvent entremêlées avec les
autres. Celles enfin sur lesquelles le hazard ou des circonstances
locales out entasse de préférence, et dans le même lieu, les matières
que vomissoit le volcan, sans laisser le temps au dépôt des eaux de
se mêler avec elles, ont produit quelques petites montagnes presque
entièrement volcanique, où les cendres sont agglutinées par une pâte
calcaire, etc. Cette théorie rend raison de tous le phénomènes et de
toutes les singularités qui s'observent dans le mélange des produits
du feu et des dépôts de l'eau, et une infinité de preuves de differens
genres, mais qui seroient étrangères à ce Memoire, concourent à
démontrer, l'existence d'un ancien plateau qui étoit élevé de plusieurs
centaines de toises au-dessus du sol actuel des vallées et du niveau de
la mer, qui couvroit non seulement le Val _di Noto_, mais encore
toute la Sicile, et dont les débris ont formé toutes les montagnes
actuellement existantes, à l'exception de l'Etna.»
It is not the explanation here given by the Chevalier de Dolomieu, of
the manner in which this great mass of land was formed in the sea, that
is concerned with the subject at present under our examination, but
certain facts set forth in the Memoir, and a certain conclusion which is
there endeavoured to be drawn from those interesting facts[28]. This will
be understood by considering; first, it is on all hands acknowledged,
that the stratified matter of the globe was successively deposited in
the bottom of the sea; secondly, it is also agreed, that this great mass
of Sicily, formed originally under the sea, was afterwards placed in the
atmosphere, whether by the retreat of the sea or by the elevation of the
land; and now, lastly, we are of one mind with respect to the present
shape of things, as having been produced by the wasting away of great
part of that mass which had been once continued all over the island, as
high at least as the tops of the mountains, _i.e._ about a mile above
the level of the sea; we only differ in the time and agents which have
been employed in this Operation.
[Footnote 28: In the first part of this work, the distinction has been
made of true volcanic productions, and those which are so frequently
confounded with them; these last, though the creatures of subterranean
fire, and bodies which have been made to flow in a fluid state, are
clearly different from those masses of lava which have issued from a
volcano, as has been there described. I would only here observe, that,
according to this Theory, these bodies, which the Chevalier de Dolomieu
here represented as lava and volcanic production, must be considered as
unerupted lavas, which had been made to flow among the strata of the
earth, where other at the bottom of the sea, or during those operations
by which this land was erected above the level of the ocean.]
On the one hand, the Memoir now before us represents this great effect
as belonging to an unknown cause, so far as we are ignorant of that
grand _débacle_ or _catastrophe_ which changed the situation of the sea.
On the other hand, the Theory now proposed explains this operation,
of forming those conical mountains of Sicily, and hollowing out its
valleys, by known causes, and by employing powers the most necessary,
the most constant, and the most general, that act upon the surface of
the earth.
But, besides explaining this change of land and water by an unknown
cause, our author has here employed, for the removing of this mass
of solid rock, powers which appear to me no ways adequate to the end
proposed. The running of water upon the soft mud left by a river, given
here as an example, corresponds indeed in some respects with the form
of valleys; for, water acts upon the same principle, whether it makes
a channel through the subtile sediment of a river, or through the
travelled materials of a valley. But it is not here that there is
any difficulty in conceiving the rivers of Sicily to have shaped the
mountains and the valleys; it is in removing the masses of solid rock,
which covered the whole surface of this land in successive strata, that
any doubt could occur in ascribing the actual appearances of things to
the natural operations of the earth; but it is here particularly that
the retreat of the sea, in whatever manner supposed to be done, is
altogether incompetent for the purpose which is now considered. I
flatter myself, that when the Chevalier de Dolomieu, who has employed
his uncommon talents in examining and elucidating the effects of fire in
the bowels of those burning mountains, shall consider and examine the
effects of time upon the surface of the earth, he will be ready to adopt
my opinion, that there is no occasion to have recourse to any unknown
cause, in explaining appearances which are every where to be found,
although not always attended with such remarkable circumstances as those
with which his labours have enriched natural history.
It may be proper to give a view of the operations of nature upon the
Apennines. It is from an account of a journey into the province of
Abruzzo, by Sir William Hamilton. Phil. Trans. 1786.
The road follows the windings of the Garigliano, which is here a
beautiful clear trout stream, with a great variety of cascades and
water-falls, particularly a double one at Isola, near which place CICERO
had a villa; and there are still some remains of it, though converted
into a chapel. The valley is extensive, and rich with fruit trees, corn,
vines, and olives. Large tracts of land are here and there covered with
woods of oak and chestnut, all timber trees of the largest size. The
mountains nearest the valley rise gently, and are adorned with either
modern castles towns, and villages, or the ruins of ancient ones. The
next range of mountains, rising behind these, are covered with pines,
larches, and such trees and shrubs as usually abound in a like
situation; and above them a third range of mountains and rocks, being
the most elevated part of the Apennine, rise much higher, and, being
covered with eternal snow, make a beautiful contrast with the rich
valley above mentioned; and the snow is at so great a distance as not to
give that uncomfortable chill to the air which I have always found in
the narrow valleys of the Alps and the Tyrol.
Having thus examined the alpine countries both of the Old World and the
New, it remains to observe some river in a more low or level country
emptying itself into a sea that does not communicate with the ocean. The
Wolga will now serve for this purpose; and we shall take our facts from
the observations of those men of science who were employed by their
enlightened Sovereign to give the natural as well as the economical
history of her dominions.
Russia may be considered as a square plain, containing about 40 degrees
of longitude, and 20 of latitude, that is, between the 47° and 67°
degrees. The east side is bounded by the Oural mountains, running in a
straight line from north to south. The west is bounded by Poland. The
south reaches to the Caspian and Black Seas, as does the north to the
Polar Ocean.
The greatest part of the water which falls upon this extensive country
is delivered into the Caspian by the river Wolga; and this water runs
from the east and west sides, gathered in two great rivers, the Kama and
the Oka. The water thus gathered from the two opposite extremities of
this great kingdom meet in the middle with the Wolga, which receives its
water from the north side. We thus find the water of this great plain
running in all directions to its centre. Had this been the lowest place,
here would have been formed a sea or lake. But this water found a lower
place in the bed of the Caspian; and into this bason it has made its
way, in forming to itself a channel in the great plain of the Wolga.
Our present purpose is to show that this channel, which the Wolga
has cut for itself, had been once a continued mass of solid rock and
horizontal strata, which in the course of time has been hollowed out to
form a channel for those waters. These waters have been traversing all
that plain, and have left protuberances as so many testimonies of what
had before existed; for, we here find the horizontal strata cut down and
worn away by the rivers.
M. Pallas gives us very good reason to believe that the Caspian Sea had
formerly occupied a much greater extent than at present; there are the
marks of its ancient banks; and the shells peculiar to the Caspian Sea
are found in the soil of that part of its ancient bottom which it has
now deserted, and which forms the low saline _Steppe_. He also makes it
extremely probable that the Caspian then communicated with the Euxine or
Black Sea, and that the breaking through of the channel from the Euxine
into the Mediterranean had occasioned the disjunction of those seas
which had been before united, as the surface of the Caspian is lowered
by the great evaporation from that sea surrounded with dry deserts.
However that may he, it is plain, that throughout all this great flat
inland country of Russia, the solid rocks are decaying and wearing away
by the operation of water, as certainly, though perhaps not so rapidly,
as in the more mountainous regions of the earth.
If there is so much of the solid parts worn and washed away upon the
surface of this earth, as represented in our Theory; and if the rivers
have run so long in their present courses, it may perhaps be demanded,
Why are not all the lakes filled up with soil; and why have not the
Black and Caspian Seas become land or marshy ground, with rivers passing
through them to the ocean? Here is a question that may be considered
either as being general to all the lakes upon the earth, or as
particular to every lake which should thus find a proper explanation in
the Theory. With regard to the last of these, the question has already
been considered in this view, when the particular case of the Rhône was
taken as an example; and now we are only to consider the question as
general to the globe, or so far as belonging to the Theory, without
particularising any one case.
It must be evident, that the objection to the Theory, here supposed to
be made, is founded necessarily upon this, that the solid basis of
our continent, on whose surface are found the lakes in question, is
preserved without change, because, otherwise, the smallest variation in
the basis may produce the most sensible effects upon the surface; and in
this manner might be produced dry land where there had been a lake, or a
lake where none had been before. But, as the present Theory is founded
upon no such principle of stability in the basis of our land, no
objection, to the wasting operations of the surface of the earth, can be
formed against our Theory, from the consideration of those lakes, when
the immediate cause of them should not appear.
The natural tendency of the operations of water upon the surface of
this earth is to form a system of rivers every where, and to fill up
occasional lakes. The system of rivers is executed by wearing and
wasting away the surface of the earth; and this, it must be allowed, is
perfect or complete, at least so far as consistent with another system,
which would also appear to be in nature. This is a system of lakes with
which the rivers are properly connected. Now, as there are more way
than one by which a lake may be formed, consistent with the Theory, the
particular explanation of every lake must be left to the natural history
of the place, so far as this shall be found sufficient for the purpose.
There are many places which give certain appearances, from which it is
concluded, by most intelligent observators, that there had formerly
existed great lakes of fresh water, which had been drained by the
discharge of those waters through conduits formed by some natural
operation; and those naturalists seem to be disposed to attribute to
some great convulsion, rather than to the slow operation of a rivulet,
those changes which may be observed upon the surface of the earth. Let
us now examine some of those appearances, in order to connect them with
that general system of moving water which we have been representing as
every where modifying the surface of the earth on which we dwell.
It is the P. Chrysologue De Gy, who gives the following description.
Journal de Physique, Avril 1787.
«La principaute de Porrentrui l'emporte encore en ce genre sur le reste
du Jura à ce qu'il paroît. On pourra en juger sur les circonstances
locales que je vais rapporter. Une partie de cette principauté est
divisée en quatre grandes vallées, d'environs quatre lieues de long,
sur trois quarts-d'heure ou une heure de large, séparées par autant de
chaînes de montagnes fort élevés et large en quelques endroits d'une
lieue et demie. Les extrémités de chacune de ces vallées sont plus
élevées que le milieu, et on ne peut pas en sortir par ces extrémités
sans beaucoup monter. Mais ces vallées ont des communications entr'elles
par une pente assez douce à travers ces masses énormes de montagnes qui
les separent, et qui sont coupées au niveau du milieu des vallées sur
300, 400, 500 toises de hauteur et dans toute leur largeur. On pourroit
assez justement comparer ces vallées à des berceaux posés les uns à côté
des autres, dont les extrémités, remplies en talus, seroient plus élevés
que les cotés, et dont ces côtés seroient coupés jusqu'au fond, pour
laisser une passage de l'un à l'autre. Je connois sept à huit passages
semblables à travers ces hautes montagnes, dans une quarré d'environ
quatre à cinq lieues; et dont quatre aboutissent à la vallée de
Mouthier-Grand-Val. Ces passages sont évasés dans le dessus, d'environ
une demi-lieue par endroits; mais leurs parois, en talus, se rejoignent
dans le fond où coule un ruisseau. On a pratiqué des routes sur
quelques-uns de ces talus, mais les roches sont quelquefois si
resserrées et si escarpées, qu'on a été obligé de construire un canal
sur le ruisseau, pour y faire passer la route. C'est-là que l'on voit
à son aise, la nature de ces rochers primitives, leur direction, leur
inclinaison, et tous leurs autres accidens qui demanderaient chacun une
dissertation particulière trop longue pour le moment, et il faut les
avoir vues pour se faire une juste idée des sentimens de grandeur, de
surprise, et d'admiration qu'elles inspirent, et que l'on ne peut pas
exprimer par des paroles. Cependant, les sources de ruisseaux, ou si
l'on veut des rivières qui traversent ces montagnes, sont beaucoup plus
basses que les sommités des montagnes elles-mêmes, ces sources ne font
donc pas la cause de ces effets merveilleux. Il a fallu un agent plus
puissant pour creuser ces abîmes.»
M. de la Metherie has taken a very enlightened view of the country of
France; and has given us a plan of the different ridges of mountains
that may be traced in that kingdom, (Journal de Physique, Janvier 1787).
Now there is a double purpose in natural history to which such a plan as
this may be applied; viz. first, to trace the nature of the solid parts,
on which the soil for vegetation rests; and, secondly, to trace the
nature of the soil or cultivated surface of the earth, on which depends
the growth of plants.
With regard to the first, we may see here the granite raising up the
strata, and bringing them to the light, where they appear on each
side of those centrical ridges. What M. de la Metherie calls _Monts
Secondaires_, I would call the proper strata of the globe, whether
primary or secondary; and the _Monts Granit_, I would consider as
mineral masses, which truly, or in a certain sense, are secondary, as
having been made to invade, in a fluid state, the strata from below,
when they were under water; and which masses had served to raise the
country above the level of the ocean.
But this is not the subject here immediately under consideration; we are
now tracing the operations of rivers upon the surface of the earth,
in order to see in the present state of things a former state, and to
explain the apparent irregularity of the surface and confusion of the
various mineral bodies, by finding order in the works of nature; or a
general system of the globe, in which the preservation of the habitable
world is consulted.
For this last purpose also the mineral map of M. de la Metherie is
valuable. It gives us a plan of the valleys of the great rivers, and
their various branches, which, however infinitely ramified, may be
considered as forming each one great valley watered, or rather drained,
by its proper river. But the view I would now wish to take of those
valleys, is that of habitable and fertile countries formed by the
attrition of those rivers; and to perceive the operation of water
wearing down the softer and less solid parts, while the more hard and
solid rocks of the ridges, as well as scattered mountains, had resisted
and preserved a higher station.
In this map, for example, let us suppose the first and second ridge of
our author's plan to be joined at the mouth of the Loire, and retain the
water of that river, as high as the summit of its surrounding ridges;
this great valley of the Loire, which at present is so fine and fertile
a country, would become a lake; in like manner as the proper valley of
the Rhône, above St Maurice, would be drowned by shutting up that gap of
the mountains through which the Rhône passes in order to enter the plain
of Geneva.
This is the view that P. Chrysologue takes of those small valleys formed
between the ridges of the Jura. But this is not perhaps the just view of
the subject; for though by closing the gap by which the Loire or Rhône,
passes through the inclosing ridge, the present country above would
certainly be overflowed by the accumulated waters, yet it is more
natural to suppose, that the great gap of the Loire, or the Rhône, had
been formed gradually, in proportion as the inclosed country had been
worn down and transported to the sea. We have but to consider, that the
attrition of those transported materials must have been as necessary for
the hollowing out of those gaps in the solid rock of the obstructing
mountains, as the opening of those gaps may have been for the
transporting of those materials to the sea. But it is perhaps
impossible, from the present appearance of things, to see what
revolutions may have happened to this country in the course of its
degradation; what lakes may have been formed; what mountains of softer
materials may have been levelled; and what basons of water filled up and
obliterated.
This general view of the valley of the Loire, and all its branches, is
perhaps too extensive to be admitted in this reasoning from effect to
cause; we must approximate it by an intermediate step, which will easily
be acknowledged as entering within the rule. It is in Forrez, near the
head of the Loire. There we find the plain of Mont Brison, 40,000 toises
or 22 miles long and half as wide, surrounded by a ridge of granite
mountains on every side. Here the river, which is a small branch of
the Loire, enters at the upper end of the plain (as M. de Bournon has
described)[29] «Par une gorge très étroite et tortueuse,» and goes out in
like manner at the under End.
[Footnote 29: Journal de Physique, Mai 1787.]
Those French philosophers, who have seen this plain, have little doubts
of this having been a lake, that is to say, they easily admit of the
original continuity of those ridges of mountains in which the gaps are
now found, through which the river passes. But upon those principles it
must be evident, that the river has hollowed out that plain, at the
same time that it had formed the gaps in those ridges of the granite
mountains. The only solid part, or original stratum, which M. de Bournon
has described as having seen in this plain, is a decomposing _grès_ or
sandstone; but there is reason to suppose, that there had been both
calcareous and argillaceous or marly strata filling the hollow of that
space which is inclosed by the granite mountains; consequently, no
difficulty in conceiving that the river, which must wear away a passage
through those mountains, should also hollow out the softer materials
within, and thus form the plain, or rather a succession of plains, in
proportion as the level of the water had been lowered with the wearing
mountains.
If we are allowed to make this step, which I think can hardly be
refused, we may proceed to enlarge our view, by comprehending, first,
the Vallais of the Rhône, secondly, the countries of the Seine and
Rhône, above the mountains through which those two rivers in conjunction
have broke, below Lyons; and, lastly, that country of the Rhône and
Durance which is almost inclosed by the surrounding mountains, meeting
at the mouth of the Rhône. But this reasoning will equally apply to the
countries of the Garonne, the Loire, and the Seine.
One observation more may now be made with regard to the courses of great
rivers, and the fertile countries which they form in depositing the
travelled soil; it is this. That though those rivers have hollowed out
their beds and raised their banks; though they are constantly operating
in forming fertile soil in one place and destroying it in another; and
though, in many particular situations, the fertile countries, formed
at the mouths of those rivers, are visibly upon the increase, yet the
general progress of those operations is so slow, that human history does
not serve to give us information almost of any former state of things.
The Nile will serve as an example of this fact.
The river Nile, which rises in the heights of Ethiopia, runs an amazing
tract through desert countries, and discharges its waters near the
bottom of the Mediterranean sea, fertilizes a long valley among barren
countries with which it is surrounded, and thus lays the foundation of
a kingdom, which, from its situation and the number of people it can
maintain and easily bring together for any manner of action, is perhaps
the strongest that can well be imagined. Accordingly, it has been of old
a great kingdom, that is to say, a powerful state within itself; and has
left monuments of this power, which have long been the admiration of the
world. The most ancient Grecian Histories mention these monuments as
being no better known, with regard to their dates and authors, than they
are at this day.
The conclusion here meant to be drawn is this, that, in a period of time
much more ancient than the most ancient periods in human history, Egypt
had been a country formed and watered by the Nile in like manner as it
is at present; that though continual changes are making in this as well
as in every other river, yet, on the whole, no sensible alteration can
be discerned within the compass of human experience, consequently, it is
only by considering, in a scientific manner, the nature of things, and
making allowances for operations which have taken place in time past,
that any competent judgment can be formed of the present shape and
condition of countries, or of any particular place upon the surface of
this earth, so far as regards its date, its causes, or its future state.
Nothing, almost, but the kingdom of Egypt would have formed those
stupendous monuments of art and labour; and nothing but the present
state of Egypt, fertilised by the Nile, could have formed that powerful
kingdom which might execute those works.
Thus there is a system of mountains and valleys, of hills and plains,
of rivulets and rivers, all of which are so perfectly connected, and so
admirably proportioned, in their forms and quantities, like the arteries
and veins of the animal body, that it would be absurd to suppose any
thing but wisdom could have designed this system of the earth, in
delivering water to run from the higher ground; or that any thing could
have formed this beautiful disposition of things but the operation of
the most steady causes; operations which, in the unlimited succession
of time, has brought to our view scenes which seem to us to have been
always, or to have been in the original construction of this earth.
To suppose the currents of the ocean to have formed that system of
hill and dale, of branching rivers and rivulets, divided almost _ad
infinitum_, which assemble together the water poured at large upon the
surface of the earth, in order to nourish a great diversity of animals
calculated for that moving element, and which carry back to the sea the
superfluity of water, would be to suppose a systematic order in the
currents of the ocean, an order which, with as much reason, we might
look for, in the wind. The diversity of heights upon the surface of the
earth, and of hardness and solidity in the masses of which the land is
formed, is doubtless governed by causes proper to the mineral kingdom,
and independent either of the atmosphere or sea; but the form and
structure by which the surface of the earth is fitted peculiarly to the
purpose of this living world, in giving a fertility which sustains both
plants and animals, is only caused by those powers which work upon the
surface of the earth,--those powers, the operation of which men in
general see with indifference every day, sometimes with horror or
apprehension.
The system of sustaining plants and animals upon a surface where
fertility abounds, and where even the desert has its proper use, is to
be perceived from the summit of the mountain to the shore within the
region of the sea; and although we have principally taken the Alps,
or alpine situations, for particular examples, in illustrating this
operation of the waters upon the surface of the earth, it is because the
effects are here more obvious to every inquirer, and not because there
is here to be acknowledged any other principle than that which is to be
found on all the surface of the earth, a principle of generation in one
sense, and of destruction in another.
We may also find in this particular, a certain degree of confirmation
to another part of the same theory; a part which does not come so
immediately within our view, and concerning which so many contradictory
hypotheses have been formed. Naturalists have supposed a certain
original construction of mountains, which constitution of things,
however, they never have explained; they have also distinguished those
which have evidently been formed in another manner, that is to say,
those the materials of which had been collected in the ocean. Now, here
are two things perfectly different; on the one hand original mountains
formed by nature, but we know not how, endued with solidity, but not
differing in this respect from those of a posterior formation; on the
other hand, secondary mountains, formed by the collection of materials
in the sea, therefore, not having solidity as a quality inherent in
their constitution, but only occasional or accidental in their nature.
If, therefore, it be the natural constitution of things upon the surface
of this earth to indurate and become solid, however originally formed
loose and incoherent, we should thus find an explanation of the
consolidation of those masses which had been lately formed of the loose
materials of the ocean; if, on the contrary, we find those pretended
primitive mountains, those bodies which are endued with hardness
and solidity, wasting by the hand of time, and thus wearing in the
operations natural to the surface of the earth, Where shall we find
the consolidating operations, those by which beds of shells have been
transformed into perfect marble, and siliceous bodies into solid flint?
or how reconcile those opposite intentions in the same cause?
Nothing can be more absurd than to suppose a collection of shells and
corals, amassed about the primitive mountains of the earth, to become
mountains equally solid with the others, upon the removal of the sea; it
would be inconsistent with every principle of sound reasoning to suppose
those masses of loose materials to oppose equal resistance to the
wasting and destroying operations of the surface of the earth, as do
those pretended primitive masses, which might be supposed endued with
natural hardness and solidity; yet, consult the matter of fact, and it
does not appear that there is any difference to be perceived. There are
lofty mountains to be found both of the one kind and the other; both
those different masses yield to the wasting operations of the surface;
and they are both carried away with the descending waters of the earth.
It is not here meant to affirm, that a mass of marble, which is
a calcareous substance, opposes equal resistance, whether to the
operations of dissolution or attrition, as a mass composed of granite or
of quartz; it is only here maintained that there are in the Alps lofty
mountains of marble, as there are in other places lower masses of
granite and its accompanying schistus. But that which is particularly to
be attended to here is this: In all countries of the earth, whether of
primitive masses or those of secondary formation, whether uniform and
homogeneous, or compound and mixed of those two different kinds of
bodies, the system is always the same, of hills and valleys, lakes and
rivers, ravines and streams: no man can say, by looking into the most
perfect map, what is primary or what secondary in the constitution of
the globe. It is the same system of larger rivers branching into lesser
and lesser in a continued series, of smaller rivers in like manner
branching into rivulets, and of rivulets terminating at last into
springs or temporary streams. The principle is universal; and, having
learned the natural history of one river, we know the constitution of
every other upon the face of the earth.
Thus all the surface of this earth is formed according to a regular
system of heights and hollows, hills and valleys, rivulets and rivers,
and these rivers return the waters of the atmosphere into the general
mass, in like manner as the blood, returning to the heart, is conducted
in the veins. But as the solid land, formed at the bottom of the sea or
in the bowels of the earth, could not be there constructed according to
that system of things which we find so widely pursued upon the surface
of the globe, it must be by wasting the solid parts of the land that
this system of the surface has been formed, in like manner as it is by
the operations of the sea that the shape of the land is determined, upon
the shore.
Thus it has been shown, that the general tendency of the operations
natural to the surface of the globe is to wear the surface of the earth,
and waste the land; consequently that, however long the continents of
this earth may be supposed to last, they are on the whole in a constant
state of diminution and decay; and, in the progress of time, will
naturally disappear. Hence confirmation is added to that mineral system
of the earth, by which the present land is supposed to have acquired
solidity and hardness; and according to which future land is supposed to
be preparing from the materials of the sea and former continents; which
land will be brought to light in time, to supply the place of that which
necessarily wastes, in serving plants and animals. But what is here more
particularly to the purpose is this; that we find an explanation of that
various shape and conformation which is to be observed upon the surface
of this earth, as being the effect of causes which are constant and
unremitting in their operation, which are widely adapted to the end or
absolutely necessary in the system of this world, and which, in the
indefinite course of time, become unlimited in their effect, or powerful
in any conceivable degree.
It is not sufficient for establishing the present theory, to refute that
most unscientific hypothesis, adopted by some eminent philosophers, of
mountains and valleys being the effect of currents in the ocean; it is
necessary to see what is their proper cause, and to show that by no
other cause known could the general effect, which is of such importance
in the system of this world, be actually produced. It is for this reason
that we have endeavoured to show that there is a general, an universal
system of river and valley, which renders the surface of this earth a
sort of organized body destined to a purpose which it perfectly fulfils.
But to see the full force of this argument, taken from that order of
things which is perceived in that system of valley and river all over
the earth, let us examine, first, what would be the effect, in the
constitution of this world, of bodies of land formed upon no such
system; and, secondly, what would be the effect of the natural
constitution of this world and meteorological operations of the
atmosphere, if continued for a sufficient length of time, upon a mass of
land without any systematic form.
For this purpose we shall take for example a portion of this earth,
which is the best known to us, that is the south-western part of Europe,
in order to compare its present state, which so perfectly fulfils the
purpose of this world, with that in which no order of valley and of
rivers should be fund.
Let us begin at the summit, which is the Mont-Blanc. At present the
water, falling from the heavens upon this continent, is gathered into
a system of rivers which run through valleys, and is delivered at last
into the Adriatic, the Mediterranean, the Atlantic, and the German Seas;
all the rest of this continent, except some lakes and marshes, is dry
land, properly calculated, for the sustenance of a variety of plants and
animals, and so fulfils the purpose of a habitable earth. Now, destroy
that system of river and valley, and the whole would become a mixture
of lakes and marshes, except the summits of a few barren rocks and
mountains. No regular channels for conveying the super-abundant water
being made, every thing must be deluged, and nothing but a system of
aquatic plants and animals appear. A continent of this sort is not found
upon the globe; and such a constitution of things, in general, would
not answer the purpose of the habitable world which we possess. It is
therefore necessary to modify the surface of such a continent of land,
as had been formed in the sea, and produced, by whatever means, into the
atmosphere for the purpose of maintaining that variety of plants and
animals which we behold; and now we are to examine how far the
proper means for that modification is to be found necessarily in the
constitution of this world.
If we consider our continent as composed of such materials as may decay
by the influence of the atmosphere, and be moved by water descending
from the higher to the lower ground, as is actually the case with the
land of our globe, then the water would gradually form channels in
which it would run from place to place; and those channels, continually
uniting as they proceed to the sea or shore, would form a system of
rivers and their branchings. But this system of moving water must
gradually produce valleys, by carrying away stones and earthy matter
in their floods; and those valleys would be changing according to the
softness, and hardness, destructability or indestructability of the
solid parts below. Still however the system of valley and river would
be preserved; and to this would be added the system of mountains, and
valleys, of hills and plains, to the formation of which the unequal
wearing down of the solids must in a great measure contribute.
Here therefore it is evident, _first_, that the great system upon the
surface of this earth, is that of valleys and rivers; _secondly_, that
no such system could arise from the operations of the sea when covering
the nascent land; _thirdly_, that this system is accomplished by the
same means which, are employed for procuring soil from the decaying
rocks and strata; and, _lastly_, that however this system shall be
interrupted and occasionally destroyed, it would necessarily be again
formed in time, while the earth continued above the level of the sea.
Whatever changes take place from the operation of internal causes, the
habitable earth, in general, is always preserved with the vigour of
youth, and the perfection of the most mature age. We cannot see man
cultivate the field, without perceiving that system of dry land provided
by nature in forming valleys and rivers; we cannot study the rocks
and solid strata of the earth, those bulwarks of the field and shore,
without acknowledging the provident design of nature in giving as much
permanency to our continent, as is consistent with sufficient fertility;
and we cannot contemplate the necessary waste of a present continent,
without perceiving the means for laying the foundation of another. But
the evidence of those truths is not open to a vulgar view; _media_ are
required, or much reasoning; and between the first link and the last, in
this chain, what a distance, from the wasting of hard bodies upon the
surface of the earth, to the formation of a solid rock at the bottom of
the sea.
CHAP. XIV.
_Summary of the Doctrine which has been now
Illustrated._
The system of this earth appears to comprehend many different
operations; and it exhibits various powers co-operating for the
production of those effects which we perceive. Of this we are informed
by studying natural appearances; and in this manner we are led to
understand the nature of things, in knowing causes.
That our land, which is now above the level of the sea, had been
formerly under water, is a fact for which there is every where the
testimony of a multitude of observations. This indeed is a fact which
is admitted upon all hands; it is a fact upon which the speculations of
philosophers have been already much employed; but it is a fact still
more important, in my opinion, than it has been ever yet considered.
It is not, however, as a solitary fact that any rational system may be
founded upon this truth, That the earth had been formerly at the bottom
of the sea; we must also see the nature and constitution of this earth
as necessarily subsisting in continual change; and we must see the means
employed by nature for constructing a continent of solid land in the
fluid bosom of the deep. It is then that we may judge of that design,
by finding ends and means contrived in wisdom, that is to say, properly
adapted to each other.
We have now given a theory founded upon the actual state of this earth,
and the appearances of things, so far as they are changing; and we have,
in support of that theory, adduced the observations of scientific men,
who have carefully examined nature and described things in a manner that
is clear and intelligible. We are now to take a review of the principle
points on which this theory hangs; and to endeavour to point out the
importance of the subject, and the proper manner of judging with regard
to a theory of the earth, how far it is conform to the general system of
nature, which has for object a world.
If it should be admitted, that this earth had been formed by the
collection of materials deposited within the sea, there will then appear
to be certain things which ought to be explained by a theory, before
that theory be received as belonging to this earth. These are as
follows:
_First_, We ought to show how it came about that this whole earth, or by
far the greatest part in all the quarters of the globe, had been formed
of transported materials collected together in the sea. It must be here
remembered, that the highest of our mountainous countries are equally
formed of those travelled materials as are the lowest of our plains; we
are not therefore to have recourse to any thing that we see at present
for the origin of those materials which actually compose the earth;
and we must show from whence had come those travelled materials,
manufactured by water, which were employed in composing the highest
places of our land.
_Secondly_, We must explain how those loose and incoherent materials had
been consolidated, as we find they are at present. We are not here to
allow ourselves the liberty, which naturalists have assumed without
the least foundation, of explaining every thing of this sort by
_infiltration_, a term in this case expressing nothing but our
ignorance.
_Thirdly_, The strata are not always equally consolidated. We often find
contiguous strata in very different states with respect to solidity; and
sometimes the most solid masses are found involved in the most
porous substance. Some explanation surely would be expected for this
appearance, which is of a nature so conclusive as ought to attract the
attention of a theorist.
_Fourthly_, It is not sufficient to show how the earth in general had
been consolidated; we must also explain, how it comes to pass that the
consolidated bodies are always broken and intersected by veins and
fissures. In this case, the reason commonly given, that the earth
exposed to the atmosphere had shrunk like moist clay, or contracted
by the operation of drying, can only show that such naturalists have
thought but little upon the subject. The effect in no shape or degree
corresponds to that cause; and veins and fissures, in the solid bodies,
are no less frequent under the level of the sea, than on the summits of
our mountains.
_Fifthly_, Having found a cause for the fracture and separation of the
solid masses, we must also tell from whence the matter with which those
chasms are filled, matter which is foreign both to the earth and sea,
had been introduced into the veins that intersect the strata. If we fail
in this particular, What credit could be given to such hypotheses as are
contrived for the explanation of more ambiguous appearances, even when
those suppositions should appear most probable?
_Sixthly_, Supposing that hitherto every thing had been explained in the
most satisfactory manner, the most important appearances of our earth
still remain to be considered. We find those strata that were originally
formed continuous in their substance, and horizontal in their position,
now broken, bended, and inclined, in every manner and degree; we must
give some reason in our theory for such a general changed state and
disposition of things; and we must tell by what power this event,
whether accidental or intended, had been brought about.
_Lastly_, Whatever powers had been employed in preparing land, while
situated under water, or at the bottom of the sea, the most powerful
operation yet remains to be explained; this is the means by which the
lowest surface of the solid globe was made to be the highest upon the
earth. Unless we can show a power of sufficient force, and placed in
a proper situation for that purpose, our theory would go for nothing,
among people who investigate the nature of things, and who, founding on
experience, reason by induction from effect to cause.
Nothing can be admitted as a theory of the earth which does not, in a
satisfactory manner, give the efficient causes for all these effects
already enumerated. For, as things are universally to be acknowledged
in the earth, it is essential in a theory to explain those natural
appearances.
But this is not all. We live in a world where order every where
prevails; and where final causes are as well known, at least, as those
which are efficient. The muscles, for example, by which I move my
fingers when I write, are no more the efficient cause of that motion,
than this motion is the final cause for which the muscles had been made.
Thus, the circulation of the blood is the efficient cause of life; but,
life is the final cause, not only for the circulation of the blood,
but for the revolution of the globe: Without a central luminary, and a
revolution of the planetary body, there could not have been a living
creature upon the face of this earth; and, while we see a living system
on this earth, we must acknowledge, that in the solar system we see a
final cause.
Now, in a theory which considers this earth as placed in a system of
things where ends are at least attained, if not contrived in wisdom,
final causes must appear to be an object of consideration, as well as
those which are efficient. A living world is evidently an object in the
design of things, by whatever Being those things had been designed, and
however either wisdom or folly may appear in that design. Therefore the
explanation, which is given of the different phenomena of the earth,
must be consistent with the actual constitution of this earth as a
living world, that is, a world maintaining a system of living animals
and plants.
Not only are no powers to be employed that are not natural to the globe,
no action to be admitted of except those of which we know the principle,
and no extraordinary events to be alledged in order to explain a common
appearance, the powers of nature are not to be employed in order to
destroy the very object of those powers; we are not to make nature act
in violation to that order which we actually observe, and in subversion
of that end which is to be perceived in the system of created things. In
whatever manner, therefore, we are to employ the great agents, fire and
water, for producing those things which appear, it ought to be in such a
way as is consistent with the propagation of plants and life of animals
upon the surface of the earth. Chaos and confusion are not to be
introduced into the order of nature, because certain things appear to
our partial views as being in some disorder. Nor are we to proceed
in feigning causes, when those seem insufficient which occur in our
experience.
Animal life being thus considered as an object in the view of nature, we
are to consider this earth as being the means appointed for that end;
and then the question is suggested, How far wisdom may appear in the
constitution of this earth, as being _means_ properly adapted to the
system of animal life, which is evidently the end. This is taking for
granted, that there is a known system of the earth which is to be
tried--how far properly adapted to the end intended in nature. But,
it is this very system of the earth which is here the subject of
investigation; and, it is in order to discover the _true system_ that we
are to examine, by means of final causes, every theory which pretends
to show the nature of that system, or to assign efficient causes to
physical events.
Here then we have a rule to try the propriety of every operation which
should be acknowledged as in the system of nature, or as belonging to
the theory of this earth. It is not necessary that we should see the
propriety of every natural operation; our natural ignorance precludes us
from any title to form a judgment in things of which we are not properly
informed; but, no suppositions of events, or explanations of natural
appearances, are to be admitted into our Theory, if the propriety of
those alledged operations is not made to appear. We are now to make an
application.
This earth, which is now dry land, was under water, and was formed in
the sea. Here is a matter of fact, and not of theory, so far as it can
be made as evident as any thing of which we have not seen the immediate
act or execution. But the propriety of this matter of fact is only to
be perceived in making the following acknowledgment, That the origin of
this earth is necessarily placed in the bottom of the sea. In supposing
any other origin to this habitable earth, we would see the impropriety
of having it covered with water, or drowned in the sea. But, being
formed originally at the bottom of the sea, if we can explain the
phenomena of this earth by natural causes, we will acknowledge the
wisdom of those means, by which the earth, thus formed at the bottom
of the sea, had been perfected in its nature, and made to fulfil the
purpose of its intention, by being placed in the atmosphere.
If the habitable earth does not take its origin in the waters of the
sea, the washing away of the matter of this earth into the sea would
put a period to the existence of that system which forms the admirable
constitution of this living world. But, if the origin of this earth is
founded in the sea, the matter which is washed from our land is only
proceeding in the order of the system; and thus no change would be made
in the general system of this world, although this particular earth,
which we possess at present, should in the course of nature disappear.
It has already been our business to show that the land is actually
wasted universally, and carried away into the sea. Now, What is the
final cause of this event?--Is it in order to destroy the system of this
living world, that the operations of nature are thus disposed upon the
surface of this earth? Or, Is it to perpetuate the progress of that
system, which, in other respects, appears to be contrived with so much
wisdom? Here are questions which a Theory of the Earth must solve; and
here indeed, must be found the most material part by far of any Theory
of the Earth. For, as we are more immediately concerned with the
operations of the surface, it is the revolutions of that surface which
forms, for us, the most interesting subject of inquiry.
Thus we are led to inquire into the final cause of things, while we
investigate an operation of such magnitude and importance, as is that of
forming land of sea, and sea of land, of apparently reversing nature,
and of destroying that which is so admirably adapted to its purpose. Was
it the work of accident, or effect of an occasional transaction, that
by which the sea had covered our land? Or, Was it the intention of that
Mind which formed the matter of this globe, which endued that matter
with its active and its passive powers, and which placed it with so much
wisdom among a numberless collection of bodies, all moving in a system?
If we admit the first, the consequence of such a supposition would be to
attribute to chance the constitution of this world, in which the systems
of life and sense, of reason and intellect, are necessarily maintained.
If again we shall admit, that there is intention in the cause by which
the present earth had been removed from the bottom of the sea, we may
then inquire into the nature of that system in which a habitable earth,
possessed of beauty, arranged in order, and preserved with economy, had
been formed by the mixture and combination of the different elements,
and made to rise out of the wreck of a former world.
In examining the structure of our earth, we find it no less evidently
formed of loose and incoherent materials, than that those materials had
been collected from different parts, and gathered together at the bottom
of the sea. Consequently, if this continent of land, first collected in
the sea, and then raised above its surface, is to remain a habitable
earth, and to resist the moving waters of the globe, certain degrees
of solidity or consolidation must be given to that collection of loose
materials; and certain degrees of hardness must be given to bodies which
were soft or incoherent, and consequently so extremely perishable in the
situation where they now are placed.
But, at the same time that this earth must have solidity and hardness
to resist the sudden changes which its moving fluids would occasion, it
must be made subject to decay and, waste upon the surface exposed to the
atmosphere; for, such an earth as were made incapable of change, or not
subject to decay, could not afford that fertile soil which is required
in the system of this world, a soil on which depends the growth of
plants and life of animals,--the end of its intention.
Now, we find this earth endued precisely with that degree of hardness
and consolidation, as qualifies it at the same time to be a fruitful
earth, and to maintain its station with all the permanency compatible
with the nature of things, which are not formed to remain unchangeable.
Thus we have a view of the most perfect wisdom, in the contrivance of
that constitution by which the earth is made to answer, in the best
manner possible, the purpose of its intention, that is, to maintain and
perpetuate a system of vegetation, or the various race of useful plants,
and a system of living animals, which are in their turn subservient to a
system still infinitely more important, I mean, a system of intellect.
Without fertility in the earth, many races of plants and animals would
soon perish, or be extinct; and, without permanency in our land, it were
impossible for the various tribes of plants and animals to be dispersed
over all the surface of a changing earth. The fact is, that fertility,
adequate to the various ends in view, is found in all the quarters of
the world, or in every country of the earth; and, the permanency of our
land is such, as to make it appear unalterable to mankind in general,
and even to impose upon men of science, who have endeavoured to persuade
us that this earth is not to change. Nothing but supreme power and
wisdom could have reconciled those two opposite ends of intention, so as
both to be equally pursued in the system of nature, and both so equally
attained as to be imperceptible to common observation, and at the same
time a proper object for the human understanding.
We thus are led to inquire into the efficient causes of this
constitution of things, by which solidity and stability had been
bestowed upon a mass of loose materials, and by which this solid
earth, formed first at the bottom of the sea, had been placed in the
atmosphere, where plants and animals find the necessary conditions of
their life.
Now, we have shown, that subterraneous fire and heat had been employed
in the consolidation of our earth, and in the erection of that
consolidated body into the place of land. The prejudices of mankind, who
cannot see the steps by which we come at this conclusion, are against
the doctrine; but, prejudice must give way to evidence. No other Theory
will in any degree explain appearances, while almost every appearance is
easily explained by this Theory.
We do not dispute the chymical action and efficacy of water, or any
other substance which is found among the materials collected at the
bottom of the sea; we only mean to affirm, that every action of this
kind is incapable of producing perfect solidity in the body of earth
in that situation of things, whatever time should be allowed for that
operation, and that whatever may have been the operations of water,
aided by fire, and evaporated by heat, the various appearances of
mineralization, (every where presented to us in the solid earth, and the
most perfect objects of examination), are plainly inexplicable upon the
principle of aqueous solution. On the other hand, the operation of
heat, melting incoherent bodies, and introducing softness into rigid
substances which are to be united, is not only a cause which is proper
to explain the effects in question, but also appears, from a multitude
of different circumstances, to have been actually exerted among the
consolidated bodies of our earth, and in the mineral veins with which
the solid bodies of the earth abound.
The doctrine, therefore, of our Theory is briefly this, That, whatever
may have been the operation of dissolving water, and the chymical action
of it upon the materials accumulated at the bottom of the sea, the
general solidity of that mass of earth, and the placing of it in
the atmosphere above the surface of the sea, has been the immediate
operation of fire or heat melting and expanding bodies. Here is a
proposition which may be tried, in applying it to all the phenomena of
the mineral region; so far as I have seen, it is perfectly verified in
that application.
We have another proposition in our Theory; one which is still more
interesting to consider. It is this, That as, in the mineral regions,
the loose or incoherent materials of our land had been consolidated by
the action of heat; so, upon the surface of this earth exposed to the
fluid elements of air and water, there is a necessary principle of
dissolution and decay, for that consolidated earth which from the
mineral region is exposed to the day. The solid body being thus
gradually impaired, there are moving powers continually employed, by
which the summits of our land are constantly degraded, and the materials
of this decaying surface travelled towards the coast. There are other
powers which act upon the shore, by which the coast is necessarily
impaired, and our land subjected to the perpetual incroachment of the
ocean.
Here is a part of the Theory with which every appearance of the surface
may be compared. I am confident that it will stand the test of the most
rigid examination; and that nothing but the most inconsiderate judgment
may mistake a few appearances, which, when properly understood, instead
of forming any subject of objection to the Theory, will be found to
afford it every reasonable support or confirmation.
We have now seen, that in every quarter of the globe, and in every
climate of the earth, there is formed, by means of the decay of solid
rocks, and by the transportation of those moveable materials, that
beautiful system of mountains and valleys, of hills and plains, covered
with growing plants, and inhabited by animals. We have seen, that, with
this system of animal and vegetable economy, which depends on soil and
climate, there is also a system of moving water, poured upon the surface
of the earth[30], in the most beneficial manner possible for the use of
vegetation, and the preservation of our soil; and that this water is
gathered together again by running to the lowest place, in order to
avoid accumulation of water upon the surface, which would be noxious.
[Footnote 30: See Dissertations upon Subjects of Natural Philosophy, Part
I.]
It is in this manner that we first have streams or torrents, which only
run in times of rain. But the rain-water absorbed into the earth is made
to issue out in springs, which run perpetually, and which, gathering
together as they run, form rivulets, watering valleys, and delighting
the various inhabitants of this earth. The rivulets again are united in
their turn, and form those rivers which overflow our plains, and which
alternately bring permanent fertility and casual devastation to our
land. Those rivers, augmenting in their volume as they unite, pour at
last their mighty waters into the ocean; and thus is completed that
circulation of wholesome fluids, which the earth requires in order to be
a habitable world.
Our Theory farther shows, that in the ocean there is a system of animals
which have contributed so materially to the formation of our land. These
animals are necessarily maintained by the vegetable provision, which
is returned in the rivers to the sea, and which the land alone or
principally produces. Thus we may perceive the mutual dependence upon
each other of those two habitable worlds,--the fluid ocean and the
fertile earth.
The land is formed in the sea, and in great part by inhabitants of that
fluid world. But those animals, which form with their _exuviae_ such a
portion of the land, are maintained, like those upon the surface of
the earth, by the produce of that land to which they formerly had
contributed. Thus the vegetable matter, which is produced upon the
surface of the earth in such abundance for the use of animals, and
which, in such various shapes, is carried by the rivers into the sea,
there sustains that living system which is daily employed to make
materials for a future land.
Here is a compound system of things, forming together one whole living
world; a world maintaining an almost endless diversity of plants and
animals, by the disposition of its various parrs, and by the circulation
of its different kinds of matter. Now, we are to examine into the
necessary consequence of this disposition of things, where the matter of
this active world is perpetually moved, in that salutary circulation
by which provision is so wisely made for the growth and prosperity of
plants, and for the life and comfort of its various animals.
If, in examining this subject, we shall find that there is nothing in
the system but what is necessary, that is, nothing in the means employed
but what the importance of the end requires; if we shall find that the
end is steadily pursued, and that there is no deficiency in the means
which are employed; and if it shall be acknowledged that the end
which is attained is not idle or insignificant, we then may draw this
conclusion, That such a system is in perfect wisdom; and therefore that
this system, so far as it is found corresponding properly with
natural appearances, is the system of nature, and not the creature of
imagination.
Let us then take a cursory view of this system of things, upon which we
have proceeded in our theory, and upon which the constitution of this
world seems to depend.
Our solid earth is every where wasted, where exposed to the day. The
summits of the mountains are necessarily degraded. The solid and weighty
materials of those mountains are every where urged through the valleys,
by the force of running water. The soil, which is produced in the
destruction of the solid earth, is gradually travelled by the moving
water, but is constantly supplying vegetation with its necessary aid.
This travelled soil is at last deposited upon the coast, where it forms
most fertile countries. But the billows of the ocean agitate the loose
materials upon the shore, and wear away the coast, with the endless
repetitions of this act of power, or this imparted force. Thus the
continent of our earth, sapped in its foundation, is carried away into
the deep, and sunk again at the bottom of the sea, from whence it had
originated.
We are thus led to see a circulation in the matter of this globe, and a
system of beautiful economy in the works of nature. This earth, like the
body of an animal, is wasted at the same time that it is repaired. It
has a state of growth and augmentation; it has another state, which is
that of diminution and decay. This world is thus destroyed in one part,
but it is renewed in another; and the operations by which this world is
thus constantly renewed, are as evident to the scientific eye, as are
those in which it is necessarily destroyed. The marks of the internal
fire, by which the rocks, beneath the sea are hardened, and by which
the land is produced above the surface of the sea, have nothing in them
which is doubtful or ambiguous. The destroying operations again, though
placed within the reach of our examination, and evident almost to every
observer, are no more acknowledged by mankind, than is that system of
renovation which philosophy alone discovers.
It is only in science that any question concerning the origin and end of
things is formed; and it is in science only that the resolution of those
questions is to be attained. The natural operations of this globe, by
which the size and shape of our land are changed, are so slow as to be
altogether imperceptible to men who are employed in pursuing the various
occupations of life and literature. We must not ask the industrious
inhabitant, for the end or origin of this earth: he sees the present,
and he looks no farther into the works of time than his experience can
supply his reason. We must not ask the statesman, who looks into the
history of time past, for the rise and fall of empires; he proceeds upon
the idea of a stationary earth, and most justly has respect to nothing
but the influence of moral causes.
It is in the philosophy of nature that the natural history of this earth
is to be studied; and we must not allow ourselves ever to reason without
proper data, or to fabricate a system of apparent wisdom in the folly of
a hypothetical delusion.
When, to a scientific view of the subject, we join the proof which has
been given, that in all the quarters of the globe, in every place upon
the surface of the earth, there are the most undoubted marks of the
continued progress of those operations which wear away and waste the
land, both in its height and width, its elevation and extention, and
that for a space of duration in which our measures of time are lost, we
must sit down contented with this limitation of our retrospect, as
well as prospect, and acknowledge, that it is in vain to seek for any
computation of the time, during which the materials of this earth had
been prepared in a preceding world, and collected at the bottom of a
former sea.
The system of this earth will thus appear to comprehend many different
operations, or it exhibits various powers co-operating for the
production of those appearances which we properly understand in knowing
causes. Thus, in order to understand the natural conformation of this
country, or the particular shape of any other place upon the globe, it
is not enough to see the effects of those powers which gradually waste
and wear away the surface, we must also see how those powers affecting
the surface operate, or by what principle they act.
Besides, seeing those powers which are employed in thus changing the
surface of the earth, we must also observe how their force is naturally
augmented with the declivity of the ground on which they operate.
Neither is it sufficient to understand by what powers the surface is
impaired, for, it may be asked, why, in equal circumstances, one part is
more impaired than another; this then leads to the examination of the
mineral system, in which are determined the hardness and solidity,
consequently, the permanency of those bodies of which our land is
composed; and here are sources of indefinite variety.
In the system of the globe every thing must be consistent. The changing
and destroying operations of the surface exposed to the sun and
influences of the atmosphere, must correspond to those by which land is
composed at the bottom of the sea; and the consolidating operations of
the mineral region must correspond to those appearances which in the
rocks, the veins, and solid stones, give such evident, such universal
testimony of the power of fire, in bringing bodies into fusion, or
introducing fluidity, the necessary prelude to solidity and concretion.
Those various powers of nature have thus been employed in the theory, to
explain things which commonly appear; or rather, it is from things which
universally appear that causes have been concluded, upon scientific
principles, for those effects. A system is thus formed, in generalising
all those different effects, or in ascribing all those particular
operations to a general end. This end, the subject of our understanding,
is then to be considered as an object of design; and, in this design, we
may perceive, either wisdom, so far as the ends and means are properly
adapted, or benevolence, so far as that system is contrived for the
benefit of beings who are capable of suffering pain and pleasure, and of
judging good and evil.
But, in this physical dissertation, we are limited to consider the
manner in which things present have been made to come to pass, and not
to inquire concerning the moral end for which those things may have been
calculated. Therefore, in pursuing this object, I am next to examine
facts, with regard to the mineralogical part of the theory, from which,
perhaps, light may be thrown upon the subject; and to endeavour to
answer objections, or solve difficulties, which may naturally occur from
the consideration of particular appearances.
END OF VOLUME SECOND.