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.
DEFORMATION ELEVATION Continents, great islands, most mountain ranges, etc., not classified in detail.
DEPRESSION Oceans, great seas and bays, some inland valleys and lake-basins, etc., not classified in detail.
GRADATION DEPOSITION Newly emerged ocean-bottoms (e.g., portions of the Coastal plain), playas and mountain-bound deserts, many 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.
VULCANISM EXTRAVASATION Volcanic peaks, craters, lava-fields, tufa-crags, sinter-cones, volcanic necks, mesas, dykes, some mineral veins, etc., not classified in detail.
(ANTITHESIS OF DO.) Sinks, caverns, some fissures, etc., not classified in detail.
ALTERATION LITHIFICATION Minor features of certain topographic forms, e.g., reefs, crags, pinnacles, salients, out-cropping veins, 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.
GLACIATION GLACIAL CONSTRUCTION Drift-plains, moraines of whatever character, drumlins, kames, aasar, drift-dammed lakes, loess-plains and ridges, etc., not classified in detail.
GLACIAL DESTRUCTION Rock-basins, U-cañons, roches de moutonnées, etc., not here classified in detail.
WIND ACTION WIND CONSTRUCTION Dunes, sand-ridges, bars, spits, etc., not here classified in 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.