342 I. C. Russell—The Jordan- Arabah and the Dead Sea. 
in its history. As a terrace when formed is level—with certain 
slight variations due mainly to the action of the wind in heaping up 
waters in bays, etc.—a measurement of its present relation to a 
horizontal plain will indicate whether or not it has been deformed 
by orographic movement. 
The terraces described in the preceding paragraph are terraces of 
excavation. In nature we find terraces of construction as well. 
These are formed of the debris cut away from the shore by waves 
and currents, and spread out as a belt of shingle along the shore, 
resting usually on a cut terrace. The combination of cut and built 
terraces is the most common of lake-shore records, and the most 
easily identified in abandoned lake-basins. 
The material removed from the shores of a lake during the cutting 
of its marginal terraces, together with much of the debris contri- 
buted from the land by streams, is removed more or less completely, 
and after being assorted by the action of waves and currents, is 
variously distributed. The finer portions remain in suspension for 
a considerable time, and may be carried away from the land, and on 
subsiding contribute to the sedimentation of the basin. ‘The coarser 
portions consisting of sand, gravel and boulders, are too heavy to 
be floated, and therefore remain in close proximity to the shore. 
This material is swept along the lake margin by currents, and 
finally built into beaches, barriers and embankments. 
Bracues.—In the formation of beaches the shore debris remains 
at the lake margin and may coincide with a built terrace, as pre- 
viously noted, or form a terrace along a shore where no excavation 
has taken place. In either instance the material composing the beach, 
usually gravel, is in motion, especially during storms, and is being 
carried forward to where barriers and embankments are forming. 
Barriers.—On lake margins of gentle declivity ridges of gravel 
and sand are formed at some distance from the shore, but connected 
at their extremities with terraces or beaches from which the material 
for their construction is derived. The surfaces of such ridges are 
horizontal and coincide with the storm limit of the waves and cur- 
rents to which they owe their origin. They follow the broader 
sweeps of lake margins but not minor irregularities, and in desiccated 
lake basins appear like railway embankments. They frequently 
close the mouths of bays so as to shut them off from communication 
with the main water body, thus forming lagoons. 
EMBANKMENTS.— When the combined action of waves and currents 
extends a barrier into deep water, an embankment is formed, which 
in many cases becomes of very grand proportions. In the formation 
of embankments the debris of which they are composed is swept 
along the surface of the barrier or terrace leading to them, and 
deposited when deep water is reached. This process continues until 
the embankment has been built up to the water surface. It is then 
prolonged by material carried along its crest and deposited at its 
distal extremity. Both bars and embankments, when seen in cross 
section, having a more or less well-defined anticlinal structure. An 
arch of this character is termed an “anticlinal of deposition.” The 
