262 8ir H. Sotvorth — Recent Changes of Level. 



at the same heiglit. lu inlets and coves they seem to rise as we go 

 inland ; elsewhere their elevation is as irregular and sloping as that 

 of the terraces in some of the Scotch inlets is. This seems consistent 

 Bot with a general and widespread elevation of the land, bnt with the 

 rush of a mass of water, which when throttled in a narrow passage 

 would rise to a higher level, and when it had free elbow room would 

 spread out, just in the same way that we can see the Race in the 

 Bristol Channel and in the Gulf of St. Micael spread out. Hence it 

 does not seem to me that we have much good warranty for always 

 separating the high- and the low-level beaches. They are possibly, 

 if not probably, due to the same impulse and the same movement, 

 and merely mark its varying phases, whether it was constricted or 

 had room to flow freely. When it met with a barrier and its flow 

 was rapid it would rise ; hence, probably, the reason for the height 

 of the loeach at Moel Tryfaen. Where it had room to spread it doubt- 

 less reached far into the land until it spent itself. Hence, perhaps, the 

 explanation of the occurrence of Whale's bones and skeletons in the 

 low-lying districts south of the Wash, in Cambridgeshire, and the 

 shells found in the district called the Straits of Malvern, which were 

 once probably overrun by a great Race from the Bristol Channel. I 

 take this to be the most rational explanation of the raised beaches and 

 of the existence of marine debris in certain very local inland districts, 

 which it has been the custom in so many geological manuals to 

 quote as unmistakable witnesses of a general change of level of 

 land and sea where they occur. I would extend this argument to 

 all the cases where there is no clear evidence of the land being in 

 an area of proved upheaval, as in Northern Scandinavia, in Green- 

 land, and in Labrador. I would extend it also to the shell beds 

 such as those at Uddevalla, which no stretch of the imagination 

 would attribute to an old beach, and where 1 have spent many hours 

 among them ; also to some of the so-called raised beaches of Canada, 

 I would of course except some of those cases where the shells have 

 actually been found as they lived ; but even here the greatest caution 

 is necessary in interpreting the facts, for shells with their valves 

 united and enclosed in clay might, under many conditions, be 

 removed with the clay en masse, and thus simulate beds in situ. 

 Within our seas I know of no raised beaches which can unmistak- 

 ably claim to mark old sea-levels, but only the levels of one or 

 more great cataclysmic tide or tides or waves — perhaps the very 

 same wave or waves which spread out the drift and mixed the 

 Boulder-clay and the gravel and sand of the Eskers with fragments 

 of marine shells, etc. 



Another question, of course, remains, and one which is very difficult 

 of solution, namely, as to whether the various raised beaches at 

 different levels which occur round these islands are the results of 

 one considerable wave or of several, occurring at different times. It 

 seems reasonable, at all events, to suppose that the low-level beaches 

 and the high-level beaches belong to different diluvial movements. 

 We have some evidence that one such movement took place in 

 Northern Europe in the second century b.c. in the so-called Cimbric 



