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As stated in the previous communication," there are two stationary points 0 and 0' on the equator, if the pole wanders in a meridian plane. The actual motion of the pole, deduced from the climate of the past times, is however complicated, so that the above approximation only applies to the displacement of the earth's axis from the beginning of the quarternary to the present time. If the meridians passing through the pole during its motion do not show great deviations, the points corresponding to 0 and 0' do not remain stationary, but trace out an equatorial curve, having the neighbourhood of its boundary elevated, compatible with the rotation of the earth at that geological period, if the motion of the pole be sufficiently slow to complete the plastic deformation. A good instance is afforded by Tibet during the mesozoic age. Suess assumes the existence of a shallow sea named Tethys, which extended from Europe to Northern India in the late palaeozoic age, comprising a great part of Asia Minor, Persia, Turkestan, and N. China. During the mesozoic age, the normal through the earth's centre to the osculating plane of the curve traced by the wandering pole cut the surface near the southern border of Tethys in the vicinity of the Tibetan boundary, went further east, then making a round, turned westward and formed an incomplete loop through Tibet, passed over to Persia in the cretaceous ; during the eocene it passed twice through the Caucasus describing nearly the same route, and went over to Europe during the tertiary age. The course thus taken by the quasi-stationary point is shown in Fig. 1 : T is the position in the middle of the triassic, J in the jurassic, C in the cretaceous, and E in the eocene. The curve traced by the pole is similarly shown in Fig. 2. Assuming the length of periods to be 70.106 for the triassic,

Formation of Tibetan Plateau Considered from the Wandering of the Pole