fold is called the crest of the syncline or anticline, the two sides are called the limbs of the fold, and a straight line equally dividing the two limbs is called the axis of the fold. The limbs are said to dip at a certain angle to the north, south, east, or west, and so forth, the angle
Fig. 22. A Whale-back, or Pitching Anticline, rising from the GroundThe arrows indicate the "dip" of the beds, and are laid on the "dip-slopes". The lines at right angles to the shafts of the arrows indicate the "strike" of the beds.
being reckoned from the horizontal. The axis of the fold also dips at a given angle, but the extension of the axis right and left, measured along a horizontal plane, is called the strike of the fold. The fold consists of layers of rocks of considerable extent, and the fold
Fig 23. The Axis of the Hex River Syncline, pitching upwards at the Worcester end, as seen from Hex River Station
is greatest where the horizontal thrust is largest; at either side the thrust is not so great, the consequent folding is not so intense, and at a certain distance from the centre the fold gradually dies out. There is then a longitudinal dip as well as a transverse dip, and the fold is said to pitch along its line of strike. An anti-
