phenomena immediately fall into the same arrangement. The continents,
great islands, mountain systems, and non-volcanic ranges and peaks
generally, the oceans, seas, and some bays, gulfs and lakes, evidently
represent the diastatic category of movements. These greater geographic
features have long been named and classified empirically, and can be
referred to their proper places in a genetic taxonomy without change in
terminology. The volcanoes, craters, calderas, lava fields, tuff
fields, tufa crags, mesas, volcanic necks, dykes, etc., however
modified by degradation, alteration, glaciation, or wind action,
exhibit characteristic forms which have often received names indicative
of their origin. The glacial drift with its various types of surface,
the moraines, drumlins, kames, roches de moutonnées, rock basins,
kettles, lacustral plains, aqueo-glacial terraces, loess hills and
plains, etc., have been studied in their morphologic as well as their
structural aspects, and the elements of the configuration commonly
assumed have been described, portrayed, and appropriately named; and
they take a natural place in the classification of products by the
processes giving rise to them. The dunes, dust drifts, sand ridges,
etc., and the wind-scooped basins with which they are associated, are
local and limited, but are fairly well known and fall at once into the
genetic classification of forms and structures. But all of these
geographic forms are modified, even obliterated, by the ever prevailing
process of gradation, which has given origin to nearly all of the minor
and many of the major geographic forms of the earth. The forms
resulting from this second great category of geologic processes have
generally engaged the attention of systematic students, but their
prevalence, variety and complexity of relation are such that even yet
they stand in greatest need of classification.
Lesley thirty years ago regarded the mountain as the fundamental
topographic element; Richthofen recognizes the upland and the plain
("aufragendes Land und Flachböden") as the primary classes of
configuration comprehending all minor elements of topography; Dana
groups topographic forms as (1) lowlands, (2) plateaus and elevated
table lands, and (3) mountains; and these related allocations are
satisfactory for the purposes for which they are employed. But the
implied classification in all these cases is morphologic rather than
genetic, and is based upon superficial and ever varying if not
fortuitous characters; and if it were extended to the endless variety
of forms exhibited in the topography of different regions it would only
lead to the discrimination of a meaningless multitude of unrelated
topographic elements.
In an exceedingly simple classification of geographic phenomena, the
primary grouping is into _forms of construction_ and _forms of
destruction_; but it is evident on inspection of the table introduced
above that such a classification is objectionable unless the greater
geographic elements due to diastatic movements (in which the
constructive action is veritable but different in kind from those in
the other categories) be excluded, and this is impracticable without
limiting the classification to subordinate phenomena. Moreover it is
illogical and useless to unite the constructive phenomena of the
remaining categories, since (1) the processes exemplify widely diverse
laws, which must find expression in any detailed classification whether
genetic or not, and since (2) the differences between the forms united
are much greater than the differences between the forms separated in
such a classification--e.g. the differences between a dune, a drumlin
and a mesa (all constructive forms) are far greater than the
differences between a fresh lava sheet and a deeply cut mesa, between a
drumlin and the smallest drift remnant, or between a dune and a
Triassic mound of circumdenudation; and this is true whether the
distinction be made on analogic, homologic, or genetic grounds. Indeed
it seems evident that while discrimination of constructive and
destructive forms is necessary and useful in each genetic category, the
use of this distinction as a primary basis of classification is
inexpedient.
The classification of topographic forms proposed a few years ago by
Davis, who regards "special peculiarities of original structure" as a
primary, and "degree of development by erosion" a secondary basis, and
Richthofen's arrangement of categories of surface forms as (1) tectonic
mountains, (2) mountains of abrasion, (3) eruptive mountains, (4)
mountains of deposition, (5) plains, and (6) mountains of erosion,[1]
in addition to depressions of the land (Die Hohlformen des Festlandes),
are more acceptable, since they are based in part on conditions of
genesis. But it is clearly recognized by modern students of dynamic
geology that waterways are the most persistent features of the
terrestrial surface; and the most widely applicable systems of
classification of the surface configuration of the earth thus far
proposed have been based substantially on the agencies of gradation.
Thus Powell, Löwl and Richthofen classify valleys by the conditions of
their genesis; Gilbert classifies drainage; and Phillipson, unduly
magnifies the stability and genetic importance of the water parting,
classifies the hydrography through the divides; and, although these
geologists have not dwelt upon and perhaps have failed to perceive the
relation, the same classification is as applicable to every feature of
the local relief as to the streams by which the relief was developed.
[Footnote 1: (1) Tektonische Gebirge, (2) Rumpfgebirge oder
Abrasionsgebirge, (3) Ausbruchsgebirge, (4) Aufschüttungsgebirge, (5)
Flachböden, und (6) Erosionsgebirge.]
In a general classification of the topographic forms developed through
gradation, it would be necessary to include the forms resulting from
deposition as well as degradation, and also to discuss the relation of
base-level plains to antecedent and consequent relief; but in a brief
résumé it will suffice to consider only the modifications produced by
degradation upon a surface of deposition after its emergence from
beneath water level as a regular or irregular terrane; and the
influence of base-level upon the topographic forms developed upon such
a surface may be neglected in a qualitative discussion, though it is
quite essential in quantitative investigation.
The hydrography developed upon terranes affected by displacement both
before and after emergence has already been satisfactorily classified.
Powell, years ago, denominated valleys established previous to
displacement of the terrane by faulting or folding, _antecedent_
valleys; valleys having directions depending on displacement,
_consequent_ valleys; and valleys originally established upon superior
and subsequently transferred to inferior terranes, _superimposed_
valleys; and these valleys were separated into orders determined by
relation to strike and again into varieties determined by relation to
subordinate attitude of the terranes traversed. Gilbert adopted the
same general classification, and so extended as to include certain
special genetic conditions. Tietze, in the course of his investigation
of the Sefidrud (or Kizil Uzen) and other rivers in the Alburs
mountains of Persia, independently ascertained the characteristics of
the class of waterways comprehended by Powell under the term
antecedent; Medlicott and Blanford observed that many of the Himalayan
rivers are of like genesis; and Rütimeyer, Peschel and others have
recognized the same genetic class of waterways; but none of these
foreign geologists have discussed their taxonomic relations. Löwl, who
upon _a priori_ grounds denies the possibility of antecedent drainage,
has recently developed an elaborate taxonomy of valleys which he groups
as (_a_) tectonic valleys, and (_b_) valleys of erosion
(Erosionsthäler). The first of these categories is separated into two
classes, viz: valleys of flexure and valleys of fracture, and these in
turn into several sub-classes determined by character of the
displacement and its relations to structure; and the second, whose
genesis is attributed to retrogressive ("rückwärts fortschreitende" or
"rückschreitende") erosion, is vaguely separated into several
ill-defined classes and sub-classes determined by structure, climate,
and various other conditions. The second of Löwl's categories is also
recognized by Phillipson. Still more recently, Richthofen, neglecting
antecedent drainage, designated the superimposed class of Powell
_epigenetic_, and formulated a classification of the remaining types of
continental depressions (Die Hohlformen des Festlandes) as (_a_)
orographic depressions (Landsenken); (_b_) tectonic valleys, and (_c_)
sculptured valleys; and the last two categories are separated into
classes and sub-classes, corresponding fairly with those of Löwl,
determined by their relations to structure and by various genetic
conditions.
These several classifications have much in common; their differences
are largely due to the diversity of the regions in which the
investigations of their respective authors have been prosecuted; but
combined they probably comprehend all the topographic types which it is
necessary to discriminate.
The American classification and nomenclature, particularly, is
unobjectionable as applied to montanic hydrography; but it does not
apply to the perhaps equally extensive drainage systems and the
resulting topographic configuration developed on emergent terranes
either (_a_) without localized displacement or (_b_) with localized
displacement of less value in determining hydrography than the
concomitant erosion, terracing and reef building; neither does it apply
to the minor hydrography in those regions in which the main hydrography
is either antecedent or consequent; nor does it apply even to the
original condition of the superimposed or antecedent drainage of
montainous regions.
Upon terranes emerging without displacement and upon equal surfaces not
yet invaded by valleys, the streams depend for their origin on the
convergence of the waters falling upon the uneroded surface and
affected by its minor inequalities, and for their direction upon the
inclination of that surface. They are developed proximally (or seaward)
by simple extension of their courses by continued elevation, and
distally by the recession of the old and the birth of new ravines; and
since in the simple case it follows from the law of probabilities that
the receding ravine will retain approximately the old direction and
that the new ravines will depart therefrom at high angles, the drainage
systems thus independently developed become intricately but
systematically ramified and more or less dendritic in form. Löwl,
Phillipson, Richthofen, and other continental, as well as different
British and Indian geologists, and Lesley in this country, indeed
recognize this type of drainage, but they do not correlate it with the
montanic types; and Löwl's designation, derived from the manner in
which he conceives it to be generated ("rückschreitende Erosion"), does
not apply to either the completed drainage, or the coincident
topography.
Although its subordinate phases are not yet discriminated on a genetic
basis, this type or order of drainage is sufficiently distinct and
important to be regarded as coördinate with the type represented by the
entire group of categories recognized by Powell and clearly defined by
Gilbert. Such hydrography (which either in its natural condition or
superimposed characterizes many plains, some plateaus, and the sides of
large valleys of whatever genesis) may be termed _autogenous_; while
the drainage systems imposed by conditions resulting from displacement
(which characterize most mountainous regions) may be termed _tectonic_.
Gilbert's classification of drainage may then be so extended as to
include topography as well as hydrography, and so amplified as to
include the additional type.
Drainage systems and the resulting systems of topography (all of which
belong to the degradational class of forms) are accordingly.--
Type 1, Autogenous.
Type 2, Tectonic--
Order A, Consequent, upon
Class _a_, Displacement before emergence, and
Class _b_, Sudden displacement after emergence;
Order B, Antecedent; and
Order C, Superimposed, through
Class _a_, Sedimentation (when the superimposed drainage may
be autogenous),
Class _b_, Alluviation or subaerial deposition, and
Class _c_, Planation (in which two cases the superimposed
drainage may simulate the autogenous type).
In brief, the entire domain of geologic science is traversed and
defined by a genetic classification of the phenomena with which the
geologist has to deal; and the same classification is equally
applicable to geographic forms, as the accompanying table illustrates:
_Representative Geographic Forms as classified by Genesis_.
-----------------------------------+---------------------------------
GENETIC PROCESSES. | GEOGRAPHIC FORMS.
_Category_. _Class_. |
-----------------------------------+---------------------------------
| ELEVATION | Continents, great islands, most
| | mountain ranges, etc., not
DEFORMATION | | classified in detail.
| DEPRESSION | Oceans, great seas and bays,
| some inland valleys and
| lake-basins, etc., not
| classified in detail.
| DEPOSITION | Newly emerged ocean-bottoms
| | (_e.g._, portions of the
| | Coastal plain), playas and
| | mountain-bound deserts, many
GRADATION | | flood-plains, marshes, etc.,
| | not classified in detail.
| DEGRADATION | Drainage-systems and resulting
| topographic elements which
| are--
| 1--Autogenous (not
| classified in detail);
| and
| 2--Tectonic--
| Consequent, upon Displacement
| before emergence, and Sudden
| displacement after
| emergence;
| Antecedent; and
| Superimposed, through
| Sedimentation, Alluviation,
| and Planation.
| EXTRAVASATION | Volcanic peaks, craters,
| | lava-fields, tufa-crags,
| | sinter-cones, volcanic necks,
| | mesas, dykes, some mineral
VULCANISM | | veins, etc., not classified in
| | detail.
| (ANTITHESIS OF DO.) | Sinks, caverns, some fissures,
| etc., not classified in
| detail.
| LITHIFICATION | Minor features of certain
| | topographic forms, _e.g._,
| | reefs, crags, pinnacles,
| | salients, out-cropping veins,
ALTERATION | | some cataracts, etc., not
| | classified in detail.
| DELITHIFICATION | Minor features of certain
| topographical forms, _e.g._,
| pools and basins, reëntrants,
| some fissures and caverns,
| etc., not classified in
| detail.
| GLACIAL | Drift-plains, moraines of
| CONSTRUCTION | whatever character, drumlins,
| | kames, aasar, drift-dammed
| | lakes, loess-plains and
GLACIATION | | ridges, etc., not classified
| | in detail.
| GLACIAL DESTRUCTION | Rock-basins, U-cañons, roches de
| moutonnées, etc., not here
| classified in detail.
| WIND CONSTRUCTION | Dunes, sand-ridges, bars, spits,
| | etc., not here classified in
WIND ACTION | | detail.
| WIND DESTRUCTION | Ponds associated with dunes,
| "blow-outs," "purgatories,"
| etc., not classified in
| detail.
VITAL ACTION | (Not discriminated) |
-----------------------------------+---------------------------------
THE GREAT STORM OF MARCH 11-14, 1888.
A SUMMARY OF THE REMARKS MADE BY BRIGADIER-GENERAL A. W. GREELY, CHIEF
SIGNAL OFFICER OF THE ARMY.
This storm is by no means as violent as others which have occurred in
the eastern part of the United States. It is noted, however, as being
one in which an unusual amount of snow fell, which, drifted by the high
winds caused by the advance of an anticyclonic area in rear of the
storm depression, did an enormous amount of damage to the railways in
Massachusetts, southern New York, and New Jersey.
The storm centre was first noticed in the North Pacific on March 6th;
whence it passed southeast from the Oregon coast to northern Texas by
the 9th. The centre instead of maintaining the usual elliptical form,
gradually shaped itself into an extended trough of low pressure, which
covered the Mississippi and Ohio valleys during the 10th. On the
morning of March 11th the barometer trough extended from Lake Superior
southward to the eastern part of the Gulf of Mexico; in the northern
section over Lake Superior, and the southern part, over Georgia,
distinct centres, with independent wind circulation, had formed.
The northern storm centre moved northeastward and disappeared, while
the southern centre moved slowly eastward, passing off the Atlantic
coast near Cape Hatteras. The pressure on the afternoon of March 11th
was about 29.07 at the centre of both the northern and southern storms,
but during the night of the 11-12th the pressure decreased in the
southern storm centre, and the area instead of continuing its easterly
direction moved almost directly to the north, and on the morning of
March 12th was central off the New Jersey coast.
The causes which underlie the decrease of pressure and consequent
increase in the violence of storms are, as yet, undetermined. The
theory of "surges," that is, atmospheric waves independent of the
irregular variations consequent on storms, has been urged by some, and
especially by Abercromby, as the cause of the deepening of depressions
in some cases or of increasing the pressure in other cases. It is
possible that under this theory a "surge," passing over the United
States to the eastward, as its trough became coincident with the centre
of low pressure increased its intensity or decreased its pressure, and
the consequent increase in barometric gradients added to the violence
of the winds. It should be pointed out, however, that the very heavy
rainfalls from Philadelphia southward to Wilmington during the 11th,
and even the heavier ones over the lower valley of the Hudson and in
Connecticut during the 12th, may have exercised a potent influence in
depressing the barometer at the centre of this storm. However this may
be, it is certain that the storm remained nearly stationary, with
steadily decreasing pressure until midnight of March 12th, at which
time it was central between Block Island and Wood's Holl, with an
unusually low barometer of 28.92 at each station. During this day the
winds were unusually high along the Atlantic coast from Eastport to
Norfolk; the maximum velocities at the various stations ranging from 48
miles at New York City and New Haven to 60 miles at Atlantic City and
70 miles per hour at Block Island. These winds, though high, are not
unprecedented, and if they had been accompanied only by precipitation
in the form of rain, the damage on land would have been inconsiderable,
but, unfortunately for the commercial interests of New York and other
neighboring great cities, the passage of the low area to the eastward
was followed by a cold wave of considerable severity and of unusual
continuance.
The northern storm centre, which had passed eastward on the 11th, had
had the usual effect of drawing in a large quantity of cold air from
British America; a cold wave following the wake of this storm, as is
usual during the winter season. This usual effect was intensified by
the advance of a second, and more violent, cyclonic centre northward;
the effect of which was to augment the cold wave already in progress by
drawing in a still larger amount of cold air to re-enforce it.
As has been already alluded to, the quantity of snowfall was unusually
great. The easterly and northeasterly winds had drawn a large amount of
aqueous vapor from the Atlantic over New England in advance of the low
area. The sudden change of temperature precipitated by far the greater
portion of the aqueous vapor in the air, with the result of an almost
unprecedented fall of snow over western Massachusetts, Connecticut, and
the valley of the Hudson.
Professor Winslow Upton, Secretary of the New England Meteorological
Society, has gathered estimates of snow from 420 different observers,
which go to show that 40 inches or more of snow fell over the greater
part of the districts named.
The deepening of the area of low pressure and the augmentation of the
cold high area advancing from British America resulted in barometric
gradients of unusual intensity; there being gradients in excess of 6,
when gradients of 5 rarely occur either in the United States or Great
Britain. The high winds caused by these unusual gradients had the
effect of drifting the snow to an unusual extent, so that, as is well
known, nearly every railroad in New Jersey, Connecticut, New York, and
Massachusetts was snow-bound; the earliest and most prolonged effects
being experienced in Connecticut, which doubtless received the full
benefit of the heavy snowfall in the Hudson River valley in addition to
that in the western part of that State.
It is thought by some that the storm re-curved and passed northwest
into Connecticut; an opinion in which I cannot concur. The
international map and reports tend to show that this storm passed
northeastward and was on the Banks of Newfoundland on the 17th of
March. The peculiar shape of the isobars, while the storm could be
clearly defined from observations at hand, was such that it is not
unreasonable to believe that the change of wind to the south at Block
Island was due simply to an off-shoot of the storm from the main
centre, in like manner as the storm itself was the outgrowth of a
previous depression.
The track of this storm across the sea is left to Professor Hayden.
These remarks are necessarily imperfect, as my official duties have
been such as to prevent any careful study or examination of the storm
apart from that possible on the current weather maps of the Signal
Service.
THE GREAT STORM OFF THE ATLANTIC COAST OF THE UNITED STATES, MARCH
11TH-14TH, 1888.
BY EVERETT HAYDEN,
In charge of the division of Marine Meteorology, Hydrographic Office,
Navy Dept.
INTRODUCTION.
The history of a great ocean storm cannot be written with any
completeness until a long interval of time has elapsed, when the
meteorological observations taken on board hundreds of vessels of every
nationality, scattered over the broad expanse of ocean, and bound, many
of them, for far distant ports, can be gathered together, compared,
and, where observations seem discordant, rigidly analyzed and the best
data selected. It is only when based upon such a foundation that the
story can fully deserve the title of history, and not romance, fact and
not hypothesis. At best, there must be wide areas where the absence of
vessels will forever leave some blank pages in this history, while
elsewhere, along the great highways of ocean traffic, the data are
absolutely complete. Last August a tropical hurricane of terrific
violence swept in toward our coast from between Bermuda and the
Bahamas, curved to the northward off Hatteras, and continued its
destructive course past the Grand Banks toward northern Europe;
hundreds of reports from masters of vessels enabled us accurately to
plot its track, a great parabolic curve tangent to St. Thomas,
Hatteras, Cape Race, and the northern coast of Norway. Six months later
a report forwarded by the British Meteorological Office, from a vessel
homeward bound from the Equator, indicated that it originated far to
the eastward, off the coast of Africa, and only the other day the log
of a ship which arrived at New York, March 30th, from Calcutta,
supplied data by means of which the storm track can be traced still
more accurately, westward of the Cape Verde islands. Not only that, but
this same vessel on the 11th of March was about 500 miles to the
eastward of Bermuda, and, while the great storm was raging between
Hatteras and Sandy Hook, was traversing a region to the northeastward
of Bermuda from which our records are as yet very incomplete. It will
thus be clearly understood that while the most earnest efforts have
been made, not only to collect and utilize all available information,
but to be careful and cautious in generalizing from the data at hand,
yet this study must be considered as only preliminary to an exhaustive
treatise based on more complete data than it is now possible to obtain.