
PartIIL] | INCLINATION OF ROCKS. 509 
Part III.—INcLINATION OF ROCKS. 
The most casual observation is sufficient to satisfy us that the 
rocks now visible at the earth’s surface are seldom in their original 
position. We meet with sandstones and conglomerates composed 
of water-worn particles, yet forming the angular scarps of lofty 
mountains; shales and clays full of the remains of fresh-water shells 
and land-plants, yet covered by limestones made up of marine 
organisms, and these limestones rising into great ranges of hills, or 
undulating into fertile valleys, and passing under the streets of busy 
towns. Such facts, now familiar to every reader, and even to many 
observers who know little or nothing of systematic geology, point 
unmistakably to the conclusion that the rocks have in many cases 
been formed under water, sometimes in lakes, more frequently in 
the sea, and that they have been elevated into land. 
But further examination discloses other and not less convincing 
_ evidence of movement. Judging from what takes place at the present 
time on the bottoms of lakes and of the sea, we confidently infer that 
when the strata now constituting so much of the solid framework of 
the land were formed, they were laid down nearly horizontally, or at 
least at low angles (ante, p. 477). When, therefore, we find them 
inclined at all angles, and even standing on end, we conclude that 
they have been disturbed. Over wide spaces they have been up- 
raised bodily with little alteration of horizontality ; but in most places 
some departure from that original position has been effected. 
Dip.—The inclination thus given to rocks is termed their Dip. 
Its amount is expressed in degrees measured from the plane of the 

Fic. 226.—CLINOMETER—THE LEAF CONTAINING THE PENDULUM AND INDEX. 
(Half the size of the original.) 
horizon. Thus a set of rocks half-way between the horizontal and 
vertical position would be said to dip at an angle of 45°, while if 
vertical they would be marked with the angle of 90°. The inclina- 
tion is measured with an instrument termed the Clinometer, which 
is variously made, but of which one of the simplest forms is shown in 
Fig. 226. This consists of a thin strip of boxwood, two inches 
broad, strengthened with brass along the edges, and divided into two 
leaves, each 6 inches long, hinged together, so that when opened 
out they form a foot-rule. On the inside of one of these leaves a 
