/. W. Judd — On Yokanos. 9 



among those of more ancient date. In such, a subsidence, therefore, 

 we recognize a competent and obvious cause of the production of 

 the rock-basin occupied by Lake Balaton. And the fact of such 

 subsidence is confirmed, as in the analogous case of the island of 

 Mull, by the exceptional state of preservation of the old volcano 

 of Tihany. 



We thus see that an examination of the phenomena presented by 

 the largest of all the lakes in southern Europe leads us to ascribe 

 its origin to the subterranean movements that have accompanied 

 volcanic action. It is interesting to notice the circumstance that by 

 far the largest lake in our own islands exhibits the clearest proofs of 

 having been formed by the same agency. Some years ago, while 

 studying the basaltic rocks of Antrim, I was strongly impressed by 

 the conviction that Lough Neagh must clearly have been formed by 

 subsidence taking place subsequently to the great development of 

 volcanic activity in the district ; and this view is abundantly con- 

 firmed, and indeed placed beyond the possibility of doubt, by the 

 valuable observations made by Mr. E. T. Hardman, of the Geological 

 Survey of Ireland, during his detailed examination of the district. 

 In a communication laid before the British Association in 1874, Mr. 

 Hardman shows conclusively that Lough Neagh (which must origin- 

 ally have had an area nearly, twice as great as at present) existed 

 before the Glacial Epoch ; and that a series of post-Miocene disloca- 

 tions, which he has traced during his survey, would lead to a sub- 

 sidence of the tract occupied by the lake. 



That the very remarkable valley of the Jordan occupied by the 

 lakes of Merom, Tiberias and Asphaltites (Dead Sea), the latter of 

 which is 1300 feet below the Mediterranean, is an ordinary river, 

 valley, which once terminated in the Gulf of Akabah, but in the line 

 of which great depression has taken place, seems now to be clearly 

 proved by the officers who have conducted the Ordnance Survey of 

 Palestine. And there appear to be grounds for connecting this great 

 depression, which was once occupied by a single vast lake, with 

 volcanic action in the district. 



The three examples we have cited represent very fairly the three 

 principal types of lake-basins which exist upon the earth — Balaton 

 being an example of a vast but shallow depression without natural 

 outlet, — Lough Neagh a smaller but deeper lake lying in a system 

 of drainage, — and the Jordan gorge a depression in a line of river- 

 valley, the bottom of which now lies far below the sea- level. 



But in pursuing this line of reasoning we may perhaps go one 

 step further. The interesting accounts that have recently come to 

 hand of the explorations of Mr. Stanley in equatorial Africa suggest 

 the probability that the noble lake of the Victoria Nyanza (which 

 bids fair to prove a rival in size to Lake Superior in North America, 

 and therefore to be the largest sheet of fresh- water in the world) ^ may 



^ There is still some doubt remaining as to the dimensions of the Victoria Nyanza. 

 If Mr. Stanley's map represents the true positions of points on its shores, then the 

 lake would certainly be larger than Lake Superior. If, however, Captain Speke's 

 determinations of positions be accepted as the more accurate, as Mr. Ravenstein 

 adyocates, then the African lake would be about one- sixth smaller than the American. 



