H. Bury — The Chines and Cliffs of Bournemouth. 73 



but is absent from the so-called " Bottoms " which run down to 

 the Stour and the Avon. In Boscombe Chine, as in Branksome 

 Grlen, the older valley is deej) and comparatively long ; but in the 

 shorter chines (Alum, Durley, etc.) the remnant of the old valley 

 is so shallow and extends so little beyond the head of the newer 

 one, as to be easily overlooked (Fig. 3), especially as its natural 

 form has been much altered by the hand of man. It can, however, 

 still be easily traced by slight changes in the gradients of the roads 

 (Western Eoad, West Cliii Road, etc.), as well as, here and there, 

 by terrace-like fragments of the old valley floors. In the valley of 

 the Bourne human interference has obliterated almost all traces of 

 this structure, but some (chiefly in the upper parts of the valley) 

 are still visible, while others can be inferred from historical data. 



Plat, 



Fig. 2. — Longitudinal section of Branksome Chine. 



Fig. 3.— Longitudinal section of Alum Chine. 



It will be observed that the peculiar structure of the valleys 

 described above is in no way accounted for, or even considered, 

 by the hypotheses hitherto put forward to explain the origin of the 

 chines, and we must therefore look elsewhere for the cause. It will 

 hardly be disputed that the smaller size of the newer valleys (to 

 which alone, as a rule, the name " chine " is applied) is mainly, 

 if not wholly, due to meteorological changes. There may have been 

 in the past a far greater rainfall than now, but having regard to the 

 porous nature of the soil, and the way in which the great width 

 of the old valleys is maintained right u]d to their points of origin 

 in the plateau, it is probable that they were formed in a period of 

 intense cold, when the ground was rendered impervious by frost. 

 The floors of these valleys are often covered with gravel and cemented 

 sand, and the evidence on the whole seems to point to their having 

 been formed in the time of the Coombe Rock — that being the latest 

 period of intense cold of which we have clear and widespread 

 evidence along our southern coasts. 



