is formed of the greatly cooled ancient deep-sea floor, which is already solidified to great depths, and the other side of the sial material of the festoon. The formation of such a marginal fissure between the sial and sima would be very intelligible, and quite in keeping with the tilting of the festoon already referred to.
The bulging outline of the continental margin behind the festoons is strikingly shown in Fig. 39. It is seen, especially if we consider the 200 m. depth contour in addition to the coast-line itself, that the continental margin is always the reflected image of an S-shape, whilst the festoon lying in front forms a simple convex curve.
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Fig. 40.—Manner of origin of island festoons.
A, Section. B, Plan. (The greatly cooled portion of the sima is denoted by dashes.)
This relation is diagrammatically illustrated in Fig. 40, B. The phenomenon is developed in the same manner by all three of the festoons contained in Fig. 39, and is also shown for example by the continental border of East Australia and its former festoon, formed by the south-eastern prolongation of New Guinea and New Zealand. These curved shore-lines denote a compression parallel to the coast, and thus also to the direction of strike of the coastal mountains. They are to be considered as great horizontal folds. We are here dealing with a phenomenon forming part of the powerful compression which the whole of eastern Asia has undergone in a north-east and south-west direction. If the attempt is made to smooth out this sinuous line, the distance between Further India and the Bering Straits, which at present amounts to 9,100 km., would be increased to 11,100 km.
