Dr Brown on Marine Denudation of the Fricsian Islands. 273 



old historians. Allowing what they say to have been true, 

 it does not at all follow that it was the Rock Island which 

 was so large. On the contrary, I do not think that there 

 is a tittle of evidence to show that the Rock Island was ever 

 very much larger than it is just now, at least in historical 

 periods. It might have extended as far as the rocks under 

 tlie water — " the foundation of the island," as the natives call 

 them — which can be seen for a few yards from the shore all 

 around it, but no more. On the other hand, there is every 

 ground for believing that the Sand Island was within very 

 recent periods very much' larger than it is at present, 

 though the Heligoland tradition that in some remote 

 period it was connected with the Mainland, is very doubtful. 

 Up to the year 1720 the Sand Island was joined to the Rock 

 Island by a line of rock and rubbish, known as de waal (the 

 wall), but in that year it was swept away by the sea, and 

 ever since, the distance between the two islands has been 

 increasing. I send a photograph of an old engraving showing 

 the two islands united by de ivaal, which formed such a 

 breakwater against the North Sea, that many ships could 

 take shelter behind it. There seems little doubt that it was 

 on this Sand Island that the numerous churches and other 

 edifices which the old historians, such as Adam of Bremen and 

 Pontanus, tell us of, and that it is the gradual destruction, still 

 going on, of this and not of the Rock Island, which has given 

 rise to the persistent popular, but I think erroneous, impres- 

 sions on the subject. It must, of course, be acknowleged that 

 parts of the cliffs are every now and then falling. But these 

 encroachments of the sea are trifling, and have been kept 

 a record of from a very early period. Around the shores 

 are many caves and isolated masses of rocks, which are 

 remnants of the ocean's work. But this is what we can 

 see on any part of the shores of countries exposed to the 

 fury of the Xorth Sea. In conclusion, I may add that I have 

 frequently seen it stated that rabbits, by undermining the 

 cliffs, and thus assisting the marine denudation, are rapidly 

 destroying Heligoland. In reply, I can only say, firstly, that 

 Heligoland (proper) is not being destroyed; secomlly, that 

 rabbits are in no way assisting in the work of destruction, 



