ON THE GLACTATION OF EAST LOTHIAN SOUTH OF THE GARLETON HILLS. 5 



Dunbar, E. 5° S. (Mr Muff). 



Catcraig Quarry (two miles E. of Dunbar), E. 1 5° S. (Professor Young). 



Shore close to Catcraig, E. and E. 10° N. (Mr Clough). 



A striated pavement, Thorntonloch (5 miles S.E. of Dunbar), E. 10° S. (Professor 

 Young). 



St Abb's Head, E., 25° S. (Professor Young). 

 Professor Young* further noticed that the minor inequalities of the low ground have a 

 tendency to run in lines almost parallel with one another, a fact which is well illustrated 

 in a shaded copy of an Ordinance one-inch map (Sheet 33). He attributed this to the 

 result of direct sub-glacial erosion, and noticed that if a line be taken joining Lothian 

 Edge to Tynemouth (see general map), it separates the lowlands into two districts. 

 West of the line the grooving runs E.N.E. or E. by N., but on its seaward side the 

 features " become much more easterly and even a few degrees south of east." This type 

 of ice modelling is not so widely developed in East Lothian as in many parts of 

 Scotland,t but it is well shown in the district south and east of Haddington. 



The direction of ice flow indicated by the modelling agrees approximately with that 

 of the few strias observed, and thus the erosion effects as a whole, where recognisable, 

 serve as a useful check upon the evidence afforded by the deposits. They clearly 

 demonstrate that in the low-lying parts of the county the ice sheet followed roughly the 

 trend of the central valley, until, debouching upon the North Sea plain, it was forced 

 to take a somewhat southerly course, skirting the termination of the Southern Uplands. 

 The district lying south and east of Haddington affords a good illustration of the 

 special characteristics of an ice-dressed surface upon a large scale. The topography 

 induced is essentially that of a drumlin country. Long low mounds or ridges run 

 parallel with one another, merely separated by shallow broad-bottomed grooves or valleys. 

 If any particular ridge be followed it will presently be observed to sink slowly and 

 gradually until the grooves on either side meet about its termination ; others have, 

 however, by this time arisen situated en echelon to their failing companion, and so the 

 group persists though its individual members prove inconstant. The distinction between 

 these mounds and true drumlins depends upon the fact that they have been fashioned 

 in solid rock and are merely coated over with boulder clay, very thin along the crests 

 of the ridges, instead of being entirely formed of the latter. Wherever an isolated resis- 

 tant mass occurs, this type of sculpture naturally becomes accentuated, and Traprain 

 Law furnishes a familiar example of " crag and tail." By taking note of such where they 

 occur, it becomes evident that the whole grooving must be referred to an ice sheet 

 moving towards the E.N.E. In following this course the current flowed from the area 

 occupied by sedimentary rocks south of Haddington over the igneous rocks occurring 

 south of Traprain Law. The phenomena marking this passage from the soft rocks to 



* The Geology of East Lothian, 1866, pp. 63, 64. 



t Cf. Sir A. Geikie, Geology of East Berwickshire, 1863, p. 52, and J. Goodchild, Glacialisti Magazine, vol. iv. 

 pt. 1, 1896, p. 1. 



