OUTLINE.--Rivers of different kinds: consequent, antecedent,
superimposed, subsequent, adjusted.--Topography of Northern New
Jersey.--Revived and superimposed rivers in New Jersey.--Drainage of
the Watchung crescent.--Re-arrangement of superimposed rivers by the
growth of subsequent streams.--Application of this principle to the
Green river in the Uinta mountains: Powell's and Emmons' theories.--The
Green river probably superimposed and its branches re-arranged by the
growth of subsequent streams.--Anaclinal and reversed rivers in New
Jersey.
Northern New Jersey is drained by several streams which rise in the
Archean Highlands, flow southeastward across the central Triassic plain
and reach the sea near the inland margin of the Cretaceous formation.
What kinds of rivers are these? Such a question can hardly be answered
until we have examined rivers in many parts of the world, gaining
material for a general history of rivers by induction from as large as
possible a variety of examples; and until we have deduced from our
generalizations a series of critical features sufficient to serve for
the detection of rivers of different kinds wherever found.
The generalizations here referred to may be presented in the form of a
classification, following the ideas of Powell, Gilbert, Heim, Löwl and
others, as follows:
_Consequent rivers_.--Those that have in their birth, at the time of
their original establishment on the country which they drain, selected
courses in accordance with the constructional slopes of the surface;
for example, the Red River of the North and such of its branches as
flow on the even surface of the lacustrine plain of Lake Agassiz; the
several streams that drain the broken lava blocks of Southern Oregon;
certain streams and rivers of the Jura that drain the synclinal troughs
of those mountains. Consequent streams may be divided into definite and
indefinite groups. Definite consequent streams are those that follow
well defined constructional channels, such as the axial line of a
synclinal trough, or the lowest point of an anticlinal arch between two
synclinal basins; they are defined in location as well as in direction.
Indefinite consequent streams are those that flow down constructional
slopes, such as the flanks of an anticline, but whose precise location
depends on those minor inequalities of surface that we term accidental;
they are defined in direction but not in location; and they are as a
rule branches of definite consequent streams.
_Antecedent rivers_.--Those that during and for a time after a
disturbance of their drainage area maintain the courses that they had
taken before the disturbance. In Powell's original definition of this
class of rivers, he said that the valleys of the Uinta mountains are
occupied by "drainage that was established antecedent to the
corrugation or displacement of the beds by faulting or folding."[1] No
limit is set to the amount of corrugation or displacement or to the
strength of the faulting or folding. It therefore seems advisable to
consider what variations there may be from the strongly marked
antecedent type; one extreme being in those cases where the
displacement was a minimum and the perseverance of the streams a
maximum, the other where the displacement was a maximum and the
successful perseverance of the streams a minimum, or zero. The simplest
examples of antecedent rivers are therefore found in regions that have
been broadly elevated with the gentlest changes of slope, so as to
enter a new cycle of topographic development, all the streams retaining
their previous courses, but gaining ability to deepen their former
channels down to the new baselevel; such streams may be called
"revived." Examples of revived streams are very common; nearly all the
streams of the Highlands of New Jersey are of this kind; all the
streams of central and western Pennsylvania seem to belong in the same
class. From these simple and common examples, we shall some day, when
our knowledge of rivers is better developed, be able to form a complete
series leading to what is generally understood as the typical
antecedent river, which has outlived deformation as well as elevation
without suffering either deflection or ponding. Large rivers of strong
slope, well enclosed in steep-sided valleys, or in other words vigorous
adolescent rivers have the best opportunity to persist across a belt of
rising or writhing country,[2] because a great deformation would be
required to throw them from their courses. Small streams or large ones
of faint slope in an open low country are more easily deflected. From
the typical antecedent river, the series may be continued by examples
in which even the larger streams are less or more ponded or deflected
by the deformation, until at the end of the series there is a complete
extinction of the antecedent drainage and the establishment of an
entirely original consequent drainage. The perfectly typical antecedent
river, in the middle of this series, is certainly of rare occurrence,
and is perhaps unknown.
[Footnote 1: Colorado river of the West, 163.]
[Footnote 2: Stur's expression "Gebirgshub oder Gebirgschub" suggested
to me the terms here employed.]
Consequent streams, whose course is taken on a relatively thin,
unconformably overlying mass, for a time preserve their initial
courses, even though they may be quite out of accord with the
underlying structures on which they have descended. Such streams were
first recognized by Marvine, and afterwards named "superimposed,"
"inherited" or "epigenetic" by various authors. A full collection of
examples of this class should begin with streams that depart from true
consequent courses only locally, where they have discovered a small
portion of the underlying formation, like the Merrimack at Manchester
and other water-power towns of New Hampshire, where the stream has sunk
upon rocky ledges beneath the surface drift and sands; or like the
Mississippi and other rivers in Minnesota which have in places cut
through the drift sheet to the underlying crystallines. The series
would conclude with streams that have stripped off the cover on which
they were consequent, and have thus become superimposed on the
underlying formation in their whole length.
There is a curious intermediate type of drainage lately recognized by
McGee in the southern states, a superimposed drainage that is not
inconsequent upon the buried surface beneath the unconformably
overlying surface layer. It occurs in regions where a well-marked
drainage had been established; a brief submergence then allowed the
deposition of a relatively thin mask of sediments; an elevation brought
the masked surface up again, and as it rose, the streams took
possession of lines essentially identical with the courses of their
ancestors, because the mask of newer deposits had not extinguished the
antecedent topography. McGee proposes to call such streams
"resurrected."
Rivers of all classes as a rule develop during their adolescence and
more mature growth certain "subsequent" branches that were not in any
way represented in the early youth of the system. Thus the indefinite
members of the consequent drainage of the Jura mountains have developed
subsequent streams on soft beds of monoclinal and anticlinal
structures, where there could not possibly have been any consequent
drainage lines at the birth of this system, unless we admit the
supposed fracturing of the anticlinal crests, which seems unnecessary
to say the least. Even in the simplest style of drainage, growing on a
level surface, many of the branches must be "subsequent," or as McGee
has called them in such cases, "autogenetic."
Rivers of all classes are subject to spontaneous re-arrangement or
adjustment of their courses to a greater or less extent, in accordance
with the weaker structural lines. This results from the migration of
divides and the consequent abstraction or capture of one stream by
another. The capture is generally made by the headward development of
some subsequent branch. But after this kind of change has advanced to a
certain extent, the divides become stable, and further change ceases.
The rivers may then be said to be maturely adjusted. Under certain
conditions, chiefly great initial altitude of surface, and great
diversity of structure, that is, in mountainous regions, the changes
arising from adjustments of this spontaneous kind are very great, so
that the courses of a river's middle age may have little resemblance to
those of its youth, as Löwl has pointed out and as I have tried to show
in the case of the Pennsylvanian rivers. It may be difficult to
recognize in such cases whether the youthful courses of a river system
were consequent, antecedent or superimposed. Adjustments of this kind
were not discussed by Powell, although he makes brief mention of what I
have called subsequent streams. The first appreciation that I gained of
river adjustments came from the writings of Löwl; but I have since
found that the general principles governing their opportunity were
stated by Gilbert in his monograph on the Henry Mountains of Utah (pp.
141, 149), and by Heim in his Mechanismus der Gebirgsbildung (i, 272,
etc., ii, 79, 320).
Where do the rivers of northern New Jersey stand in this general scheme
of river classification? We must again postpone the answer to the
question, while reviewing the history of the general geographical
development of the region.[3]
[Footnote 3: The more detailed statement of this history may be found
in an essay prepared by the author with the collaboration of Mr. J. W.
Wood, Jr., of the class of 1888 in Harvard College, the study being
undertaken as a joint thesis by instructor and student in a second
course in Physical Geography. The essay is published in the Proceedings
of the Boston Society of Natural History, 1889.]
[Illustration: FIG. 1.]
The topography of northern New Jersey may be briefly described as made
up of valleys and lowlands that have been etched in the now elevated
surface of what may be called the Schooley peneplain on the Cretaceous
baselevel. The topographical atlas of New Jersey should be constantly
referred to, in order to follow such a statement as this; but in order
that the reader may without undue difficulty apprehend the meaning of
my descriptions and recognize the various localities yet to be named
without the trouble of searching for them on the maps of the atlas, I
have attempted to draw a generalized bird's eye view of northern New
Jersey, as it would be seen by an observer about seventy miles
vertically above the center of southern New Jersey. The meridians are
vertical and east and west lines are horizontal, but oblique azimuths
are foreshortened. The result is hardly more than a geographical
caricature, and I publish it in part to experiment upon the usefulness
of so imperfect an effort. An active imagination may perceive the long
even crest line of Kittatinny Mountain on the northwest, rising beyond
the rolling floor of the Kittatinny Valley, as the great Alleghany
limestone lowland is here called; then come the Highland plateaus, of
accordant altitude one with another, but without the mesa-like margin
that my pen has not known how to avoid indicating. The Central plain
lies in the foreground, diversified by the various trap ridges that
rise above its surface; First and Second mountains of the double
Watchung crescent near the Highlands; Sourland Mountain in the
southwest; and Rocky Hill, the southwestern re-appearance of the
Palisades intrusive trap sheet, lying a little nearer to us. The
Central plain is also diversified by the Fall-line, a slight but rather
distinct break in its surface from Trenton (Tr.) on the Delaware to a
little below New Brunswick (N. B.) on the Raritan. The important
drainage lines are: the Delaware, forming the western boundary of the
State, trenching Kittatinny Mountain at the Water Gap, cutting a deep
transverse valley through the Highlands where it receives longitudinal
branches, and a shallower trench across the Kittatinny lowland and the
Central plain; the Raritan, whose north and south branches head in the
Highlands, while the Millstone joins it from south of the fall-line,
cutting through Rocky Hill near Princeton (Pr.) on the way; and the
Pequannock-Passaic, rising in the Highlands, gathering tributaries in
the low basin behind the Watchung ridges, and escaping to the front
country as a single stream, the Passaic, through deep gaps at
Patterson. The terminal moraine, marking the furthest advance of the
second glacial invasion of post-tertiary time, is indicated by an
irregular dotted band crossing the State, from the Narrows of New York
Bay, which it defines, on the east, passing over Second Mountain by the
gap at Summit (S), rising midway in the Highlands over Schooley
Mountain, and traversed by the Delaware at Belvidere (B).
The Schooley peneplain is indicated by the crest and summit altitudes
of Kittatinny Mountain, the Highland plateaus and the trap ridges. This
peneplain once lay low and essentially horizontal, the practically
completed work of the processes of denudation acting on a previously
high land through a long period of time: it is now lifted and tilted,
so that its inland portion rises to the height of the Highlands, which
are its remnants, while its seaward portion descends slowly beneath a
cover of unconformable Cretaceous beds, southeast of the fall-line, and
thus hidden sinks gently beneath the Atlantic shore. The cover of
Cretaceous sediments was laid on the southeastern part of the old
peneplain during a moderate submergence of its seaward portion, before
the elevation and tilting above mentioned (fig. 2, below). Much of the
cover has been worn away since the time of elevation (figs. 3-6,
below), which gave opportunity for the opening of deep valleys on the
soft limestones and slates among the hard crystalline rocks of the
Highlands; and for the production of the broad Kittatinny Valley
lowland or peneplain on the wide belt of limestones beyond the
Highlands; and furthermore for the development of a broad baselevelled
plain on the weak Triassic shales and sandstones, where the old
peneplain has been almost entirely destroyed. The Cretaceous cover
remains only near the coast, where it stood too low to be attacked
while the valleys and lowlands just described were carved out. An
interesting peculiarity in the relation between the newer baselevel
plain on the Triassic area and the old Cretaceous peneplain is that
their surfaces mutually intersect at a small angle along the line which
now marks the visible contact between the Triassic and Cretaceous
formations: the newer plain standing beneath the eroded portion of the
older one northwest of this line, while it rises above the buried part
of the older one and obliquely truncates its Cretaceous cover to the
southeast of the line. Finally, the land as a whole has been raised a
little since the making of the newer plain, and shallow valleys
interrupt its broad surface. It is no longer a true plain; it has
become a pastplain. A few words may be allowed me concerning these
terms, peneplain and pastplain. Given sufficient time for the action of
denuding forces on a mass of land standing fixed with reference to a
constant baselevel, and it must be worn down so low and so smooth, that
it would fully deserve the name of plain. But it is very unusual for a
mass of land to maintain a fixed position as long as is here assumed.
Many instances might be quoted of regions which have stood still so
long that their surface is almost reduced to its ultimate form; but the
truly ultimate stage is seldom reached. We can select regions in which
the valley lowlands have become broad and flat, the intermediate "doab"
hills have wasted away lower and lower until they are reduced to forms
of insignificant relief; and yet the surface still does not deserve the
name of plain as unqualifiedly as do those young lands newly born from
seas or lakes in which their geometrically level surfaces were formed.
I have therefore elsewhere suggested[4] that an old region, nearly
baselevelled, should be called an almost-plain; that is, a peneplain.
[Footnote 4: Amer. Jour. Sci., xxxvii, 1889, 430.]
On the other hand, an old baselevelled region, either a peneplain or a
truly ultimate plain, will, when thrown by elevation into a new cycle
of development, depart by greater and greater degrees from its simple
featureless form, as young narrow valleys are sunk beneath its surface
by its revived streams. It therefore no longer fully deserves the name
that was properly applicable before its elevation. It must not again be
called a peneplain, for it is now not approaching and almost attaining
a smooth surface, but is becoming rougher and rougher. It has passed
beyond the stage of minimum relief, and this significant fact deserves
implication, at least, in a name. I would therefore call such a region
a pastplain. The area of the weak Triassic shales was, until its late
elevation, as good an example of an ultimate baselevelled plain as any
that I have found; but now it is a pastplain, as any one may see while
traveling across it on the train: its doabs are broad and continuous,
and its valleys are relatively narrow and shallow. The Kittatinny
lowland is intersected by streams whose valleys sink below its
generally even, gently rolling surface; but it was never so smooth as
the Triassic plain. It was only a peneplain, and it is now a roughened
peneplain. Perhaps the more adventurous terminologist will call it a
past-peneplain; but I dare not venture quite so far as that. When the
Highlands were lowlands, their surface well deserved the name of
peneplain; but they were lifted so long ago into so high a position
that they are now cut into a complicated mass of rugged uplands. They
no longer deserve the name of peneplain; and if in preceding paragraphs
I have referred to them as constituting an old peneplain, it is because
no satisfactory name has yet been applied to the particular stage of
development of plains and plateaus in which they now stand. Having
tried in vain to invent a term with which to name the Highlands, let me
now advertise for one in the pages of our Magazine.
* * * * *
WANTED: a name applicable to those broken, rugged regions that have
been developed by the normal processes of denudation from the once
continuous surface of a plain or peneplain. The name should be if
possible homologous with the words, _plain_, _peneplain_ and
_pastplain_; it should be of simple, convenient and euphonious form; it
must be satisfactory to many other persons than its inventor; and its
etymological construction should not be embarrassed by the attempt to
crowd too much meaning into it. The mere suggestion that it was once a
plain and that it is now maturely diversified will suffice.
* * * * *
The topography of northern New Jersey is therefore, like its structure,
polygenetic. It exhibits very clearly a series of forms developed under
three different geographic cycles, and closer search will doubtless
discover forms belonging to yet other cycles, less complete and of
briefer duration than these three. There is the tilted and deeply
eroded peneplain of the Highlands, whose initial form may be called the
Schooley peneplain, from the distinct exhibition of one of its remnants
on Schooley's mountain; this was the product of Jurassic and Cretaceous
denudation. There is the younger central baselevelled plain, developed
during Tertiary time, or thereabouts, on the weaker Triassic and
Cretaceous beds; and the associated valleys of the same age that have
been sunk into the weakest rocks of the Highlands. There are the
shallow valleys in the Central plain, of the latest post-tertiary
cycle, requiring the name of this region to be changed from plain, as
it was lately, to pastplain, as it is now. The first cycle, in which
the Schooley peneplain was produced, witnessed the accomplishment of a
great work; it included in its later part, besides various other
oscillations, the sub-cycle when the seaward or southeastern part of
the peneplain was gently submerged and buried to a slight depth under
Cretaceous deposits. The second cycle was shorter; being a time
sufficient to baselevel the softer beds, but not seriously to consume
the harder parts of the pre-existing surface. We are still in the third
cycle, of which but a small part has elapsed. The question with which
this essay opened may now be taken up.
The streams and rivers of northern New Jersey may be examined, with the
intention of classifying them according to their conditions of origin,
to their degree of complexity as indicated by the number of geographic
cycles through which they have lived, and to the advance made toward
their mature adjustment.
The Musconetcong may be taken as the type of the Highland streams. It
flows southwestward along a narrow limestone valley between crystalline
plateaus on either side, entering the Delaware a little below Easton,
Pa., (E, fig. 1). It drains a country that has been enormously denuded,
and during the Jura-Cretaceous cycle of this deep denudation, there
must have been time for it and its fellows to become thoroughly
adjusted to the structure of the region; it must be chiefly for this
reason that it flows so closely along the weak limestone belt, and has
its divides close by on the adjoining harder crystallines, (M, fig. 2).
Whatever its origin, it has lost every initial feature that was
discordant with the deep structures that it discovered beneath the
initial surface; it is maturely adjusted to its environment. It endured
to an old age during the baselevelling of the Schooley peneplain, and
is now a "revived" stream, in at least its second cycle of work. Most
of the other streams of the Highlands and the country farther inland
are also of this well adjusted, revived kind. The streams of the
Kittatinny valley lowland show not only the first revival of the kind
just described, but also a second revival, in consequence of the recent
uplift that has introduced the third cycle of development; this not
being so clearly manifested in the Highlands, where the rocks are
harder, and the valleys of the second cycle are narrower.
Look now at the drainage of the crescentic Watchung mountains; the
curved edges of two great warped lava-flows of the Triassic belt. The
noteworthy feature of this district is that the small streams in the
southern part of the crescent rise on the back slope of the inner
mountain and cut gaps in both mountains in order to reach the outer
part of the Central Plain. If these streams were descended directly or
by revival from ancestors antecedent to or consequent upon the
monoclinal tilting of the Triassic formation, they could not possibly,
in the long time and deep denudation that the region has endured, have
down to the present time maintained courses so little adjusted to the
structure of their basins. In so long a time as has elapsed since the
tilting of the Triassic formation, the divides would have taken their
places on the crest of the trap ridges and not behind the crest on the
back slope. They cannot be subsequent streams, for such could not have
pushed their sources headwards through a hard trap ridge. Subsequent
streams are developed in accordance with structural details, not in
violation of them. Their courses must have been taken _not long ago_,
else they must surely have lost their heads back of the second
mountain; some piratical subsequent branch of a larger transverse
stream, like the Passaic, would have beheaded them.
The only method now known by which these several doubly transverse
streams could have been established in the not too distant past, is by
superimposition from the Cretaceous cover that was laid upon the old
Schooley peneplain. It has already been stated that when the Highlands
and this region together had been nearly baselevelled, the coastal
portion of the resulting peneplain was submerged and buried by an
unconformable cover of waste derived from the non-submerged portion:
hence when the whole area was lifted to something like its present
height, a new system of consequent streams was born on the revealed sea
bottom. Since then, time enough may have passed to allow the streams to
sink their channels through the unconformable cover and strip it off,
and thus superimpose themselves on the Triassic rocks below: we should
therefore find them, in so far as they have not yet been re-adjusted,
following inconsequent, discordant courses on the under formation. The
existing overlap of the Cretaceous beds on the still buried Triassic
portion of the old Schooley peneplain makes it evident that such an
origin for the Watchung streams is possible; but it has not yet been
independently proved that the Cretaceous cover ever reached so far
inland as to cross the Watchung ridges.
Want of other explanation for the Watchung streams is not satisfactory
evidence in favor of the explanation here suggested. There should be
external evidence that the Triassic area has actually been submerged
and buried after it was baselevelled to the Schooley peneplain and
before it was uplifted to its present altitude; other streams as well
as the ones thus far indicated, should bear signs of superimposition;
and if adjustment of the superimposed courses has begun, it should be
systematically carried farthest near the largest streams. I shall not
here state more than in brief form, the sufficient evidence that can be
quoted in favor of the first and second requisites. Suffice it to say
that the overlap of the Cretaceous beds (which contain practically no
Triassic fragments) on the bevelled Triassic strata at Amboy and
elsewhere indicates submergence after baselevelling; and that the
pebbles, sands and marls of the Cretaceous series point clearly to the
Highlands as their source. The submergence must therefore have reached
inland across the Triassic formation at least to the margin of the
crystalline rocks. Some shore-line cutting must have been done at the
margin of the Highlands during Cretaceous time, but the generally
rolling surface of the old peneplain leads me to ascribe its origin
chiefly to subaërial wasting. Moreover, the North Branch of the
Raritan, between Mendham and Peapack (* Fig. 1) and the Lockatong (L),
a small branch of the Delaware on the West Hunterdon sandstone plateau,
give striking indications of superimposition in the discordance of
their courses with the weaker structural lines of their basins, so
unlike the thoroughly adjusted course of the Musconetcong and its
fellows, the Pohatcong, the Lopatcong, and others.
The third requisite of the proof of the inland extension of the
Cretaceous, and the resulting superimposed origin of the Watchung
streams may be stated in detail, as being more in the line of this
essay: has the adjustment that accompanies superimposition
systematically advanced farther near the large streams than near the
small ones? The character of this adjustment should be first examined
deductively. Given a series of streams of different volumes, flowing
southeastward, in the direction of the present dip of the remnant of
the Cretaceous cover, over the former inland extension of this
superposed formation; how will these streams react on one another when
they sink their channels into the underlying Triassic formation?
[Illustration: FIG. 2.]
The conditions during the formation of the cover of Cretaceous beds are
illustrated in fig. 2, where the Triassic portion of the peneplain is
submerged, and the shore-line of the transgressing ocean has reached
the margin of the crystalline rocks. The waste from the crystallines is
spread out as a series of gravels, sands and marls on the baselevelled
Triassic area.
[Illustration: FIG. 3.]
Then follows the elevation and tilting of the peneplain with the cover
on its back; and with this regression of the sea, there is an
equivalent gain of new land; a smooth gently sloping plain is revealed
as the shore line retreats; streams run out across it from the
crystalline area, or begin on its open surface, growing mouthward as
the land rises. Three such streams, A, C, D, are shown in fig. 3; their
opportunity for deep valley-cutting is indicated by the depth of the
new baselevel, BL, below the general surface of the country. While
these streams are deepening their channels in the Cretaceous cover,
which is unshaded with marginal contour lines in the figures, their
subsequent, autogenetic branches are irregularly disposed, because
there is no lateral variation of structure to guide them; but after a
time, the baselevelled surface of the buried Triassic beds is reached,
as is shown by linear shading in the valley bottoms of figs. 4, 5, 6,
7. The growth of the subsequent branches then developed, will be along
the strike of the Triassic softer beds, that is, about square to the
course of the three transverse streams under consideration. The most
rapid growth will be found on the branches of the largest stream, A,
because it will most quickly cut down its channel close to the
baselevel of the time and thus provide steep sloping valley-sides, from
which the subsequent branches cut backwards most energetically. In due
time the main streams discover the particularly resistant transverse
lava sheets in the underlying formation; and then the subsequent
branches of the largest transverse stream on the up-stream side of the
obstructions, for example, F and G, fig. 4, will have a great advantage
over those of the smaller streams. The most rapidly growing subsequent
branch, G, fig. 5, of the largest transverse master stream, A, may grow
headwards so fast as to push away the divide, X, which separates it
from the head of the opposing subsequent branch, J, of the next
adjacent smaller transverse stream, C, and thus finally to capture and
divert the headwaters, H, of the smaller transverse stream to the
larger one, as in fig. 6. The divide creeps while the two opposing
subsequent branches are in contest; it leaps when the successful
subsequent branch reaches the channel of the conquered stream. The
first stream captured in this way must necessarily be the nearest to
the large stream. The diversion of the considerable volume of
headwaters, H, to the channel of the small subsequent branch, G, causes
it to deepen its channel rapidly; the same effect is perceptible in H
for a distance above its point of capture and diversion: the increased
load of sediment thus given to G will be in great part dropped in a
fan-delta where it enters the flat valley of the master stream, A,
(fig. 6).
[Illustration: FIG. 4.]
[Illustration: FIG. 5.]
[Illustration: FIG. 6.]
Gaining strength by conquest, other captures are made, faster for a
time, but with decreasing slowness as the head of the diverting
subsequent branch recedes from the original master: and at last,
equilibrium may be gained when the headwater slope of the diverting
branch is no greater than that of the opposing subsequent branch of the
next uncaptured transverse stream. After the capture of a transverse
stream has been effected in this way, the divide, Y, between its
diverted upper portions, H, fig. 6, and its beheaded lower portion, C,
will be pushed down stream by the growth of an inverted stream, V. This
goes on until equilibrium is attained and further shifting is prevented
on reaching the hard transverse lava sheets, Z, fig. 7; here the divide
is maturely established. In the case of a system of transverse streams,
C, D, etc., fig. 7, successively captured by the subsequent branch of a
single master, the divides (Z, Y'), between the inverted (V, V') and
beheaded (C, D) portions of the captured streams will for a time
present different stages of approach to establishment. The divide on
the line of that one of the original streams, C, that is nearest to the
master stream, A, may reach a final stable position, Z; while on the
next stream further away from the master, the beheaded portion, D, may
still retain a short piece above the gap in the upper lava sheet, not
yet secured by the inverted stream, V'; and a third stream, further
away still from the master (not shown in figure 7) might remain
uncaptured and independent.
[Illustration: FIG. 7.]
It is by such tests as these that we may hope to recognize the
occurrence of partial adjustment in the streams of the Watchung
crescent as a result of their superimposition on the Triassic formation
from its former Cretaceous cover. The greater the degree of complexity
in the tests proposed, the more confidence we shall have in the theory
when the tests successfully meet the facts. Hence the reason for
deductively carrying out the theoretical conditions to their extremest
consequences in order to increase the complexity of the tests that are
to be confronted with the facts. This, as a matter of method, seems to
me of great practical importance in any attempt to decipher the past
progress of geographical development.
The admirable contoured topographic maps of New Jersey, issued by the
Geological Survey of that state under the leadership of the late
Professor George H. Cook, afforded means of applying the deductive
tests above outlined without the necessity of plodding over all the
country concerned; but however good the maps are, it is hardly
necessary to say that they can be interpreted with a better
appreciation of the facts that they represent after an excursion on the
ground has given the student some personal acquaintance with it. This I
have tried to gain on various occasions, maps in hand.
Atlas sheet number six, including the Central red-sandstone area, and
the five-mile-to-an-inch geological map of the state present in the
clearest manner the facts of form and structure involved in our
problem; and to my mind, the correspondence between theory and fact is
very striking. The Pequannock-Passaic is the master transverse stream
of the region: its preëminence was probably due in the beginning to its
gathering, from the unsubmerged Highlands, a greater amount of drainage
than belonged to any other stream that ran southeastward down the
gentle slope of the newly revealed Cretaceous cover. It was at that
time a compound, composite river:[5] compound because it drained areas
of different ages; composite, because these areas were of different
structures. Existing examples of compound, composite rivers are seen in
the Catawba, the Yadkin-Pedee, the Cape Fear and the Neuse rivers of
North Carolina, which all rise on the inland crystalline area, and
traverse the coastal quaternary plain before reaching the sea. But
unlike these, there must have been, when the old submerged land rose
with the Cretaceous cover on its back, numerous small streams whose
drainage area lay entirely within the Cretaceous plain. These were
simple streams, flowing over a structure of one kind and one age. Their
modern homologues are seen in the Maurice, the Great and Little Egg
Harbor and the Wading rivers of southern New Jersey, and I suppose also
in various relatively short streams of North Carolina, such as the
Lumber, Great Cohera and Moccassin.
[Footnote 5: See terminology suggested by the author. Nat. Geogr. Mag.,
i, 1889, 218.]
It cannot be supposed that the original Pequannock-Passaic possessed
the large southern branch, which I shall call the upper Passaic, by
which Great Swamp is now drained;[6] for had this been the case, the
divides between the branches of the upper Passaic and the heads of the
small streams that now still cross both of the trap ridges, must have
long ago been driven to a stable position on the crest line of the
inner ridge. The upper Passaic member of the Pequannock-Passaic system
must be regarded as a branch of subsequent development, guided by some
of the softer Triassic beds when they were reached beneath the
Cretaceous cover, and very successful in capturing and diverting other
transverse streams that were smaller than its master. For some distance
on either side from the Pequannock-Passaic gap in the trap ridges at
Patterson, the existing streams are perfectly adjusted to the Triassic
structure; that is, the ridges are persistent divides, and the lateral
subsequent branches of the master flow along the strike of the softer
shales and sandstones, except where lately thrown off their courses by
glacial drift barriers. This I interpret as meaning that the
Pequannock-Passaic master stream hereabouts made so early a capture of
adjacent superimposed streams that all traces of their initial
discordant courses have been obliterated by the development of
structurally accordant subsequent streams.
[Footnote 6: It should be recognized that the present round-about
drainage of the Great Swamp is a post-glacial feature, determined by
the morainic barrier that crosses the basin from Summit (S) to
Morristown (M): the pre-glacial drainage of the southern part of the
inner crescent was undoubtedly of a simpler and more direct pattern.]
The Watchung ridges extend only about eight miles northward of the
Paterson gaps, but reach thirty miles southwestward. It is therefore
chiefly in the latter direction that we may expect to find examples of
incomplete adjustment following superimposition and capture. At
Milburn, there is a deep gap in First mountain, and opposite this at
Summit (S, fig. 1) a partly drift-filled gap in Second mountain: this I
am disposed to regard as the former outlet of the Rockaway-Rahway
river, which on account of its considerable size was not captured by
the Passaic until it had cut its passage across the trap sheets almost
to a safe depth. The diverted upper portion--the Rockaway--now joins
the Passaic; its crooked course from the Highlands via Boonton (Bn)
being a post-glacial irregularity; the beheaded lower portion--the
Rahway--heads on the ridge of Second mountain, retains the pair of
subsequent streams between the two ridges, and flows in diminished
volume to the sea: the divide between the two portions being in its
mature stable position on Second mountain.
South of the Milburn gap, there are three streams that maintain water
gaps in First mountain, and five head branches of these three streams
rise behind the crest of Second mountain. These must be interpreted as
remnants of streams that once rose further inland, and whose upper
courses have been captured by the victorious upper Passaic; but it is
noteworthy that here, at the greatest distance from the gap of the
master stream at Paterson, the divides between the diverted and
beheaded portions of these southern streams should lie in unstable
positions, back of the crest line of Second mountain. This is exactly
what the hypothesis of a superimposed origin for these streams would
require; and if the complexity of accordance between deduction and fact
here presented be duly considered, I believe new confidence may be
gained in the hypothesis of superimposition, already rendered likely
from other evidence.
The rectangular courses of the streams that cross First and Second
mountains southwest of Milburn do not militate against their initial
obliquely superimposed courses; for, as Gilbert has shown, oblique
courses across tilted beds, alternately hard and soft, will gradually
shift until they follow rectangular courses, along the strike of the
soft beds and square across the strike of the hard beds. Middle Brook,
at the southern bend of First mountain near Bound Brook (B, B),
presents the peculiarity of branching east and west while on the trap
sheet of the mountain: this may be due to a retention here, where the
dip is moderate, of an initially superimposed bifurcation; or to
guidance by fractures at this point where the course of the mountain
changes rather abruptly; the facts at hand do not serve to make choice
between these alternatives.
The lesson of greatest importance in this study lies, to my mind, in
the gradual development of accordant subsequent streams in a region
where the unchanged superimposed drainage would show no such
accordance. Similar adjustment of subsequent streams to structural
features may characterize drainage systems that were originally
antecedent: and with this principle in mind, I have recently read over
with renewed interest Powell's classic study of the Green river where
it crosses the Uinta mountains.[7] The Green river and the smaller
streams of its lateral cañons and valleys are all regarded as
antecedent. Let us examine the arguments on which this conclusion
rests.
[Footnote 7: Exploration of the Colorado river of the west, Washington,
1875, 152-166. See also the geological map in the Geology of the Uinta
mountains, 1876.]
The Green river itself rises many miles north of the Uinta range,
traverses a relatively low basin before reaching the flank of the
mountains, and then instead of turning away, it boldly enters the great
uplift and trenches it from side to side in a profound cañon, flowing
out to the southwest on its way to the Colorado. There is relatively
low ground at the eastern end of the range, several thousand feet lower
than the summits of the range on either side of the Green river cañon,
and many thousand feet lower than the restored crest of the great
uplift; but the river does not follow this open round-about course.
Powell says that the river cut through, instead of running around, the
great obstruction, because it "had the right of way; ... it was running
ere the mountains were formed." Had the mountain fold been formed
suddenly, it would have turned the river around it to the east; "but
the emergence of the fold above the general surface of the country was
little or no faster than the progress of the corrasion of the
channel." ... "The river preserved its level, but the mountains were
lifted up.... The river was the saw which cut the mountains in two"
(152, 153). If this interpretation is correct, the Green river would be
the type of a perfect antecedent stream: but it appears to me that the
case is probably overstated in that respect. Perhaps it would have been
more deliberately stated in a later volume if Powell's intention of
describing more fully the three chief kinds of drainage of the region
had been carried out.[8] Not having seen the region, my comments may
have little value; but the context of Powell's report, the description
of the immense series of lacustrine beds, over a mile thick, north of
the mountains, and the eastward deflection of the river where it
traverses the mountains all seem to me to indicate that the Green was
by no means continuously successful in maintaining its antecedent
course across the uplift. It is by no means a typical antecedent river.
The great series of lacustrine beds up-stream from the cañon, with
conglomerates where they rest on the northern flank of the mountains,
are fully recognized in the report, and must mean that the upper
portion of the river was for a time shut back, or ponded. During part
of this time, there may have been no overflow across the growing
mountains, for the lower lacustrine beds contain fossils indicative of
brackish water.[9] The intermittent growth of the mountains and the
repeated return of lacustrine conditions, with gradually freshening
water, is indicated by the strong unconformities that occur at various
points in the lacustrine beds, and by the change in the fossil fauna.
It must be conceded from this that the upper portion of Green river was
repeatedly ponded back by mountain growth across its middle course; we
therefore have not now any close indication of its pre-lacustrine
course above the mountains; the ancient, or pre-Uinta, upper portion of
the river was extinguished by the lacustrine sediments, and to that
extent the Green river departs from the perfect antecedent type.
[Footnote 8: Geol. Uinta mountain, page v.]
[Footnote 9: Geology of the Uinta mountains, 1876, 84; Chapter III, by
C. A. White.]
In the second place, if the original Green river existed upon the upper
surface of the beds that were at a subsequent date raised to form the
Uinta uplift, it does not appear to be clearly proved that its course
at that early time was closely coincident with its present course in
the mountainous area. The first deformations of the mountain growth may
have temporarily interrupted its flow, as is made likely by the
lacustrine deposits already referred to; and when the rise in the level
of the waters of the lake overtook the uplift, probably at a time of
slower mountain growth than that which first formed the lake, the point
of overflow may have been many miles to one side of its previous
drowned-out course. The moderate elevation of the eastern end of the
range, where it connects with the Yampa plateau, may possibly have then
been a little higher than a point farther west, where the overflow was
consequently located. This is perhaps hardly as probable as the
postulates involved in arguing a truly antecedent course for the river;
but its impossibility is not as strictly proved as would be necessary
before a definite conclusion as to the continuous persistence of an
antecedent river could be finally accepted. Such continuity of action
must be rare and should be rigorously demonstrated if possible.
It must, moreover, be remembered that Emmons[10] is of the opinion that
the Colorado river is not antecedent at all, but is superimposed on the
eastern portion of the Uinta range from a course that it had chosen
upon a sheet of horizontal sediments--the Wyoming conglomerate--which
he supposes once stretched unconformably all over the previously deeply
eroded surface of the uplifted range, where the cañon is now cut. He
quotes facts of two kinds in evidence of this; first, the remnants of
the Wyoming conglomerate still lie on ridges as high as those that
enclose the river cañons; second, the Green and certain of its branches
possess tortuous courses, out of accord with the structure of the
range. It might be added that the wide open valley of Brown's park, in
the middle of the range is best explained as the product of a
pre-Wyoming cycle of erosion by rivers that were extinguished when the
Wyoming beds were laid over the mountains. The strongest objection to
Emmons' conclusion seems to be the great amount of erosion that it
requires; erosion sufficient not only to remove the Wyoming
conglomerate from nearly all its former overlap on the Uinta range,
where it had buried and extinguished a pre-Wyoming drainage, but also
to carry away a vast extension of the formation at the same height
north of the range. It may be best to conclude that both antecedent and
superimposed processes must be called on: for one must hesitate before
admitting that the Wyoming beds stretched all across the country north
and east of the Uinta range up to the height at which the remnants are
now found on the range; it seems more likely that some part of the
height of these remnants is due to a relatively local elevation. As far
as this is the case, it gives reason for regarding the Green as an
antecedent river; that is, antecedent to the local elevation of the
Wyoming beds, but long posterior to the elevation of the Uinta range:
but as the river now flows--according to Emmons' theory--on beds lying
unconformably below those on which its course was chosen, it is for
this reason to be classed as superimposed.
[Footnote 10: Fortieth Parallel Survey, ii, 1877, 194, 205, 206.]
The Green river therefore certainly departs from the type of an
antecedent stream; the departure is distinct in its repeated ponding,
whereby its upper course was broadly and indeterminately shifted from
its original location; and is at least possible if not probable in its
defeat at the line of uplift and subsequent superimposition on a new
line of overflow. The mountains wrenched the saw that afterwards cut
them in two.
A study of the Jura drainage, of which a fuller account may be given at
some future time, has led to the provisional conclusion that many of
its streams show a combination of consequent and antecedent
characteristics. They appear to be consequent on the early stages of
the deformation but antecedent to its later growth, and for this kind
of a stream I have no satisfactory name to suggest at present.
Heim has shown that the Reuss and the adjacent smaller transverse
streams of northern Switzerland near Lucerne are in part persistent
across a series of folds, and in part slightly shifted from one course
to another and ponded in Lake Lucerne; but unless the other ranges of
the Alps rise hereafter faster than they have heretofore, the geologist
of the future will reasonably regard the more mature Reuss as an
essentially successful antecedent river.
The Sutlej and other rivers that escape from the inner valleys of the
Himalaya by deep gaps in the outer ranges, are described by Medlicott
as antecedent to the elevation of the ranges through which they flow:
their antecedent origin being argued from the delta-like structure of
the upturned beds in the outer gorges, as if the rivers were now
cutting down the deformed deltas of an earlier time; but the heavy
gravel and sand deposits in their upper valleys indicates that they
were nearly if not quite ponded for a time during the deformation.
Rivers seem to have the habit of cutting down their upturned deltas.
Bonney refers to several such examples among the rivers that flow
northward from the Alps, and transect particularly thick portions of
the upturned marginal conglomerates and sandstones, which he regards as
the deltas formed by the same rivers at an earlier time, when the
mountain folding had not extended outward as far as it does now from
the axis of the Alps. I have suspected that the same kind of evidence
might be used to indicate that the Delaware above Trenton, between
Pennsylvania and New Jersey, is in part of even pre-Triassic origin;
for where it now enters the Triassic belt, there is a particularly
heavy and coarse sandstone, sometimes conglomeratic. Being a large
stream, it might persist in an anaclinal course through the
northwestward monocline formed by the Jurassic uplift of the Triassic
beds, although the smaller streams of the region were then probably
extinguished, to be replaced by a new system consequent upon the new
order of things.
Large rivers, more or less persistent in the face of opposing
disturbance, therefore appear to be generally recognized; but it is
noticeable that those quoted from the Himalaya and the Alps presumably
occupied, at the time of disturbance, well enclosed valleys, from which
it would have been difficult for them to escape backwards or laterally;
and that, even if successful in the end, they for a time suffered
defeat or ponding of greater or less extent and duration. There is no
evidence that the Green river was well enclosed immediately north of
the Uinta mountains at the time of their first elevation; hence the
likelihood of its temporary ponding or enclosure is increased.
It is stated by Powell that not only the Green but even the smaller
streams of the Uintas are of origin antecedent to the mountains. He
writes: "the explanation of the cañons of Green river will assist us in
understanding the origin of the lateral valleys and cañons. The streams
were there before the mountains were made--that is, the streams carved
out the valleys and left the mountains. The direction of the streams is
indisputable evidence that the elevation of the fold was so slow as not
to divert the streams, although the total amount of elevation was many
thousands of feet. Had the fold been lifted more rapidly than the
principal streams could have cut their channels, Green river would have
been turned about it, and all the smaller streams and waterways would
have been cataclinal" (Colorado River, 162).
This appears to me an unproved conclusion, and the evidence of it needs
careful attention. It appears that there are several streams which
descend from the crest of the mountains towards the flanks, but instead
of running all the way out to the margin of the fold, they turn along
the strike of a monoclinal valley, and thus reach the main river by a
short cut. Such streams are cataclinal for a time, then monoclinal. It
is in reference to these that it is said, "the streams were there
before the mountains were made;" and again that "the drainage was
established antecedent to the corrugation or displacement of the beds
by faulting and folding" (163). In approaching this conclusion, Powell
says these streams cannot be consequent; for "valleys consequent upon
the corrugation, which was one of the conditions of the origin of the
Uinta mountains, could not have taken the direction observed in this
system; they would have all been cataclinal, as they ran down from the
mountains, and turned into synclinal valleys at the foot, forming a
very different system from that which now obtains" (166). Nor can the
streams be superimposed, for the "later sedimentary beds, both to the
north and south, were found not to have been continuous over the
mountain system, but to have been deposited in waters whose shores were
limited by the lower reaches of the range" (166). Therefore the
discordant streams must be antecedent.
It appears to me that the possibility of error in this argument lies in
the omission of all consideration of the migration of divides and the
resulting adjustment of stream courses to deep internal structure; but
at the time of the exploration of the Colorado river, this important
process in the development of rivers was not understood. It now seems
only natural that the original, consequent, cataclinal streams, flowing
down the slopes of the range from crest to flanks, should have
permitted the opening of subsequent monoclinal branches on the soft
beds that they discovered; and that the shifting of divides in these
monoclinal valleys should have led to the capture of several cataclinal
streams by that particular one of the subsequent branches that grew out
from the master stream, the Green river itself. Thus it must happen
that the streams "which head near the summit of the range, and, running
down the flank, turn into the Green river, are, in their upper courses,
cataclinal, and when they turn to follow the strike of the rocks into
Green river, are monoclinal" (161): this being a normal result of river
work in cutting down the thousands of feet of rocks of various
hardnesses, here concerned. The smaller streams of the Uinta range are
therefore certainly not of necessity antecedent to the Uinta uplift:
the probability is that they were originally purely consequent, and
that at present they are nicely adjusted to the structures that they
have discovered.
I have learned so much from the doctrine of baselevelling, as presented
in Major Powell's writings, that I shall hope to profit by the lesson
of the Uinta drainage as well: that is, the possibility that an
apparently sound conclusion may be overturned when new processes that
bear upon it are discovered. It is here said that the drainage of the
Watchung crescent in New Jersey is an example of partial adjustment
following a superimposed origin: hence the necessity of watching
closely for the discovery of new principles in the history of river
work that may call for a revision of this conclusion.
There are two other examples of peculiar accidents in the history of
rivers in New Jersey, to which I wish to call attention; both of them
in the latest cycle of the development of the State, that is, in the
cycle which has changed the central region from its even baselevelled
lowland surface, to the pastplain as we now see it. Like the uplift of
the Schooley (Highland) peneplain, the uplift of the Central plain, in
passing from the second to the third cycle, was not uniform throughout,
but was greater in one place than in another. In the neighborhood of
the lower Raritan river, a distinct though gentle slope to the
northwest is apparent in the unconsumed surface of the pastplain; but
this strong river runs southeastward against the slope; it is an
anaclinal stream. The tilting of the pastplain is moderate, and its
rocks are weak; the river is large and strong. Its anaclinal course is
therefore best explained by regarding it as a mild example of an
antecedent stream. But Ambrose's brook, a small stream to one side of
the Raritan, flows northwest with the gentle slope that was given to
the pastplain. Ambrose's brook therefore most likely is not a survivor
from the previous cycle, but is a new stream consequent on the slight
deformation by which the latest cycle here considered was ushered in.
Manalapan and Assanpink are apparently of the same kind. (See fig. 1).
The Millstone river appears to be intermediate as respects origin
between the Raritan and Ambrose's brook. It appears still to lie for
the most part in the channel that it occupied before the elevation and
tilting of the baselevelled Central plain, but the tilting of the plain
seems to have reversed its direction of flow. It rises near the center
of the State and flows northwestward till it joins the Raritan near
Somerville, and on the way it crosses from the thrown or depressed to
the heaved or elevated side of the "fall-line,"[11] and passes through
a deep gap in the trap ridge of Rocky Hill back of Princeton. I believe
there is no other Atlantic river which runs against the fall-line in
this way; and it is certainly at first sight remarkable that a stream
of moderate size like the Millstone should have held its own against a
displacement that sufficed to deflect great rivers like the Delaware
and the Susquehanna from their courses.
[Footnote 11: For an account of the "fall-line" displacement, see
McGee, Seventh Ann. Rep., U. S. G. S., 1888, 616.]
The Millstone appears to have been a stream of the normal kind in the
previous cycle, before the tilting of the Central plain, when it
probably ran southeastward with its fellows, and carried off its share
of waste in the baselevelling process of that time. No other
supposition than this seems consistent with the general history of the
region. It was during that cycle that the deep gap was cut in the Rocky
Hill trap ridge. Then came the deformation of the baselevelled plain,
the relatively recent elevation and gentle tilting that have permitted
the streams to carve it into a pastplain; and with this, the
dislocation along the fall-line. The inclination of the interstream
surfaces of the pastplain leaves no doubt that it was tilted to the
northwest, and to this tilting we must ascribe the present direction of
the Millstone flow: but why did not the accompanying dislocation on the
fall-line throw this moderate sized stream off of its track and divert
it southwestward to the Delaware at Trenton, or northeastward to the
Raritan below New Brunswick. The effect of the dislocation appears with
considerable distinctness along a line from Trenton towards Amboy, in
the less altitude of the general surface of the pastplain to the
southeast than to the northwest of the line, the difference of altitude
of the two parts being about a hundred feet. The persistence of the
Millstone against such a dislocation seems to require that we should
postulate a slower and smaller movement here than that which deflected
the Delaware.
The reversed course of the Millstone cannot be regarded as an example
of inversion following a capture of its ancient northern headwaters by
a branch of the Raritan; for in such a case, surely the inversion could
not have progressed farther south than the hard trap ridge of Rocky
Hill, where a stable divide would have been formed: nor can the
Millstone be regarded as an original stream, first developed and
consequent upon the deformation of the Central plain, for in that case,
it should consist of two separate parts; one part running from the
actual head of the river to the fall-line, where it would turn
southwest and cross the faint flat divide that separates it from the
Delaware; the other part beginning by Princeton north of the fall-line,
and running thence north to the Raritan. The continuity of these two
parts in the actual Millstone seems to be explicable only by regarding
the river as the upper portion of a single larger river that had
reached an old age in the previous cycle; it was then broken in two at
the head of the present river where the greatest elevation of the
Central plain occurred, and thus had its former head waters reversed
from a southeast to a northwest direction of flow across and against
the fall-line break by the tilting of the plain. Only in this way can
the deep gap in Rocky Hill be explained. The river is thus consequent
on the tilting of the plain, and yet antecedent to the accompanying
faulting. It cannot be called an original stream, for it had an
ancestor in its very channel. It is not a purely consequent stream, for
it runs against the heaved side of a fault. It is not a strictly
antecedent stream, for it flows in a direction determined by a
disturbance that occurred late in its life. It is too exceptional a
stream to have a generic name. We cannot expect to find many others
like it.
The result that has been of the greatest interest to me in these
studies is the discovery of well-recorded and peculiar histories in the
commonplace small-sized rivers of our Atlantic slope. We have looked
for some years to the west as the region where river history should be
illustrated, because it was there that the pioneers in this branch of
study taught us the lessons on which our further work must depend. But
home study as well as distant travel has its rewards, and with the
progress of good topographic work on this side of the country we
confidently await much instruction from a close acquaintance with the
curious histories of many of our rivers which we know now only by name.
Harvard College, January, 1890.
* * * * *
_Supplementary Note_.--Professor Albrecht Penck of Vienna has published
a valuable essay on "Die Bildung der Durchbruchsthäler" (Verein zur
Verbreitung naturwissenschaftlicher Kenntnisse in Wien, 1888) from
which the following historical notes are taken to illustrate the
gradual overthrow of the fracture theory of cross valleys by the
introduction of the idea that rivers can sometimes cut down their beds
as fast as the land is uplifted or upfolded beneath them.
Ferd. Römer. Die jurassische Weserkette. Zeit. d. deutsch. geol.
Gesellsch., ix, 1857, 581. The deepening of valleys by rivers and
streams must keep pace with the gradual elevation of continental
masses. The Porta Westphalica has thus been cut by the Weser in the
Wiehen-Weser range, in the northeastern part of Westphalia.
A similar suggestion was briefly made a little later by Bischoff, to
explain the gorge of the Rhine below Bingen. Lehrb. d. chem. u. phys.
Geol., 2 Aufl., i, 374, 382; and again independently for the same river
by Dücker. Zeitschr. d. Gesellsch. f. Erdk. Berlin, v, 1870, 183.
Gümbel explained the course of the Altmühl, a branch of the Danube
which crosses the Frankish Jura in northwestern Bavaria, by supposing
its course was defined before and maintained during the deformation of
the range. Bavaria: Landes- und Volkskunde des Königreichs Bayern,
1865, iii, 756.
Medlicott recognized that many streams flowing from the inner Himalaya
are older than the outer ranges, and showed reason for believing that
they held their places while the outer ranges were tilted up. Mem.
Geol. Survey India, iii, 1865, 6, 122, 127, 157, 163. A little later,
he applied the same explanation to some Alpine rivers. The Alps and the
Himalayas, a geological comparison. Q. Journ. Geol. Soc., London, xiv,
1868, 47, 52.
Wynne explains the Indus and adjacent rivers as of greater age than the
elevation of the Salt Range in northwestern India. Mem. Geol. Survey
India, xi, 1875; xiv, 1878.
Rütimeyer recognized the possibility of uprising ranges being cut down
by transverse rivers, but regarded the occurrence as a rare one,
thinking that lakes would generally appear behind such a growing
barrier. He emphasized the idea that erosion works upstream, which Löwl
has later developed farther. Ueber Thal- und Seebildung, Basel, 1869; 2
Aufl., 1874.
Tietze regarded the persistence of rivers across growing ranges as the
rule rather than the exception. Die Bildung von Querthälern, Jahrb. d.
k. k. Geol. Reichsanst., 1878, 581.
Hayden was perhaps the first to point out in this country the
antecedent origin of certain headwaters of the Missouri in Montana,
where the mountain ranges are frequently cut across by deep cañons.
Amer. Journ. Science, xxxiii, 1862, 305. Hayden's Sixth Report, 1872
(1873), 85.
Reference may be made also to White, Hayden's Tenth Report, 1876
(1878), 52; Peale, id., 167; Bechler, id., 372. General discussion of
valley making is given by Green, Geology for students and general
readers, London, 1876; Hartung, Zeitschr. Gesellsch. f. Erdkunde,
Berlin, 1878, 308.
In spite of the early date of some of these essays, the idea of the
antecedent origin of rivers did not gain general recognition and
acceptance till it was strongly stated by Powell.
A CRITICAL REVIEW OF BERING'S FIRST EXPEDITION, 1725-30, TOGETHER WITH
A TRANSLATION OF HIS ORIGINAL REPORT UPON IT. With a Map.