GEOGNOSY AND GEOLOGY. 1235 
must also lie included among the valleys of elevation, where the strata lie 
around parallel to the mountain slope. An excellent illustration is found in 
the valley of Pyrmont (pl. 44, fig. 1), where the elevating mass lies under 
the strata, as of the variegated sandstone, without having broken through. 
Upon this he the strata of the muschelkalk, b, and upon this, those of the 
keuper, c. The strata 6, as well as c, occur on both sides, and were formerly 
continuous, having been separated at a subsequent period. When the 
strata were too brittle to admit of a considerable bending, they have been 
broken. Thus, while in this fissure a steep descent on both sides, along the 
axis of elevation, must exist, on the other sides, in a direction transverse to 
this axis, the slope will be more or less gentle. These relations, of no 
unfrequent occurrence, are shown sectionally in figs. 2, 3, 4, and 5. In 
jig.2, the elevating nucleus has broken through, the strata resting on it 
on each side. The steep declivities of the faces of the strata are turned 
towards the head of the nucleus, the planes of stratification lying parallel to 
the slope. In jig. 3, the mass of elevation constitutes only the base of the 
valley, as also in jig. 4, where the strata are of unequal thickness. Should 
an elevation of the latter kind take place under water, as seen in fig. 5, so 
that the strata project only on one side, the mountain chain appears to 
consist of one such lip, the other being concealed by the water. The strata 
may often slope so much along the nucleus, as that this shall occupy the 
higher level, as on the Brocken in the Hartz ( pl. 43, fig, 15), where the 
ganite, a, lies higher than the strata, b, c, d, e, f, of the transition-slate 
formation. Ifthe non-conformable mass be in great preponderance, the 
conformable may be torn entirely asunder. Valleys thus produced are 
called valleys of disruption ( pl. 45, fig. 1). 
Before we proceed further in this part of our subject, it may be advisable 
to mention a few of the technical terms employed in the consideration of 
stratification. The terms dip and strike have already been referred to. If 
we conceive a longitudinal force to act in upheaving a succession of strata, 
the line or plane in which the disturbed strata would meet if produced, 1s 
called the anticlinal axis or line. In other words, it is the line in a chain 
of hills or a valley from which the strata dip in two different directions. 
The synclinal line or axis is that along which opposite strata dip towards 
each other. When strata are parallel to each other, whatever be their 
dip, they are said to be conformable. When strata rest on the edges or 
faces of other strata, in such a manner as to render it evident that all are not 
of contemporaneous origin nor have been exposed to a simultaneous force, 
they are called non-conformable. An out-crop of strata exists when the 
edges of these strata have been elevated by the disturbing force so as to 
come to the surface. When strata have been broken or dislocated by some 
force, so that the continuity of the individual beds is interrupted by the 
sinking down or displacement of one of the portions, a fault is produced. 
When the fissure or split is filled up by injected igneous matter, a narrow 
wall is exhibited, called a dyke. 
Valleys sometimes occur as excavations produced by the abrading action 
of currents of water. This fact can be readily ascertained from an exami- 
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