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P Pant lj MOUNTAINS. 37 
(1) Contours or Relief of the Land.—While the surface 
of the land presents endless diversities of detail, its leading features 
may be generalised under the designations of mountains, table-lands, 
and plains. 
_Mountains.—The word “ mountain” is, properly speaking, not a 
scientific term. It includes many forms of ground utterly different 
_ from each other in size, shape, structure, and origin. It is popularly 
applied to any considerable eminence or range of heights, but the 
height and size of the elevated ground so designated vary indefinitely. 
In a really mountainous country the word would be restricted to 
the loftier masses of ground, while such a word as hill would be 
given to the lesser heights. But in a.region of low or gently 
undulating land, where any conspicuous eminence becomes important, 
the term mountain is lavishly used. In Eastern America this 
habit has been indulged in to such an extent, that what are, so to 
speak, mere hummocks in the general landscape, are dignified by the 
name of mountains. 
It is hardly possible to give a precise scientific definition to a term 
so vaguely employed in ordinary language. When a geologist 
uses the word, he must either be content to take it in its familiar 
vague sense, or must add some phrase defining the meaning which he 
attaches to it. He finds that there are three leading and totally 
distinct types of elevation which are all popularly termed mountains. 
1. Single eminences standing alone upon a plain or table-land. This 
is essentially the volcanic type. The huge cones of Vesuvius, Etna, 
and ‘Teneriffe, as well as the smaller ones so abundant in volcanic dis- 
tricts, are examples of it. There occur, however, occasional isolated 
eminences that stand up as remnants of once extensive rock-formations, 
These have no real analogy with volcanic elevations, but should be 
classed under the next type. ‘The remarkable buttes of Western 
America are good illustrations of them. 2. Groups of eminences 
connected at the sides or base, often forming lines of ridge between 
divergent valleys, and owing their essential forms not to underground 
structure so much as to superficial erosion. Many of the more ancient 
uplands both in the Old World and the New furnish examples of 
this type, such as the Highlands of Scotland, the hills of Cumberland 
and Wales, the high grounds betwéén Bohemia and Bavaria, the 
Laurentide Mountains of Canada, and the Green and White Moun- 
tains of New England. 3. Lines of lofty ridge rising into a suc- 
cession of more or less distinct summits, their general external form 
haying relation to an internal plication of their component rocks. 
- These linear elevations, where their existence and trend have been 
determined immediately by subterranean movement, are the true 
mountain-ranges of the globe. They may be looked upon as the 
erests of the great waves into which the crust of the earth has been 
thrown. All the great mountain lines of the world belong to this type. 
Leaving the details of mountain form to be described in Book VIL, 
' we may confine our attention here to a few of the more important 
