Sir H. H. Howorth — Surface Geology of N. Europe. 263 



determined in its extent by the action of the Gulf Stream. Tn the 

 north-east the current which sets out of the Baltic has evidently 

 deternjined the shape of the sandbanks opposite to the coast of 

 Norway, and produced a circular sweep in them, of which it is im- 

 possible to mistake the cause." (Play fair's "Illustrations," pp. 417-8.) 

 So much for an old master, who was also a champion of Huttonian 

 methods in geology. In more recent times the same lesson has 

 been well and continually pressed by Mr. Kinahan in regard to the 

 Irish eskers, which are really small forms of asar. I will quote 

 a passage or two, which I cannot improve upon. He says : " The 

 eskers are modifications of the banks and shoals which accumulated 

 at the colliding and dividing of the * flow ' tide currents of the 

 esker sea, similar to those that are found in the seas round Great 

 Britain and Ireland at the present day. In the Irish Sea, in the 

 vicinity of the Isle of Man, there iS a meeting of the north and 

 south ' flow ' tide waves or a ' head of the tide.' Here the tidal 

 currents meet and neutralize one another in one place, forming 

 a mass of currentless water that simply ' rises ' and ' falls ' and 

 deposits there silt and other materials. The other heads of the tide 

 in these seas are south and east of England — in the Straits of Dover 

 and between Norfolk and Holland. But in these places there are 

 different results, as the currents collide and pass one another for 

 greater or less distances, and at their edges, or the junction of the 

 different currents, long banks of gravel and shingle accumulate. 

 It is also found that long banks of gravel and shingle may form at 

 the dividing or splitting up of the ' flow ' tide current. This is 

 exemplified off the south-east coast of Ireland. From Greenore 

 Point a main current runs northward up the Irish Sea, while 

 secondary currents branch off into Wexford Bay ; and at the 

 junction of these currents with the main current there are long 

 banks between Greenore and Wicklow Heads." Again, he says : 

 At the half tide or "awash" portions of banks, and in other 

 shallow places where two currents collide, there are esker-like 

 ridges ; as St. Patrick's Bridge between Kilmore and the Saltees, 

 county of Wexford, and on the Dogger Bank, off the mouth of 

 Wexford Harbour. No action hut marine at the present day forms 

 ridges at all like the eshers. (" Geology of Ireland," pp. 225-230.) 



The asar are, in fact, very large and glorified eskers. Tlie shape 

 of the asar, and their occurring in a parallel series of mounds, point 

 to a further fact, namely, that the moving mass of water must have 

 been separated into a number of more or less parallel currents, at 

 whose colliding edges the long banks were accumulated. This 

 feature is also at once explained when we examine the contour of the 

 country, and it has been pointed out by Murchison with his usual 

 insight, and been apparently overlooked by his successors. He 

 points out how the asar in the neighbourhood of Upsala have long 

 ridges of granitic rock running parallel to them, and he says they 

 appear to have here assumed their linear direction in consequence 

 of the rocky elevations on their flanks. The prevalent linear or 



