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agent was changed from its E.S.E. normal course to a direction of ! 
E.N.E., being a deflection of 30° or more. At Stirling Castle rock, 
in consequence of the rock dipping due west, the striating agent 
was changed from its E.S.E. course to a direction of due south, 
being a deflection of 22°. So also by the Dry law boulder the 
striating agent was not merely deflected, but made to flow past in 
two separate streams, each of which differed by several degrees from 
the normal direction. 
Now I feel sure that no glacier, even of moderate dimensions, 
would have been deflected in its normal course by such obstructions. 
It would have gone straight over these rock surfaces in conformity 
with the general movement of the whole body of ice ; and certainly 1 
when it came against the Drylaw boulder, a block weighing less 
than two tons, instead of being divided by it into two separate 
streams, the glacier would have forced the boulder out of its way 
altogether. 
On the other hand, a sea-current would be far more likely to be 
deflected by such obstructions ; and if ice was floating in it of such 
form and thickness as to reach and plough through the sea-bottom, 
the mud and gravel there might be pushed forward in such a way as to 
smooth and striate submarine rocks, whether horizontal or sloping. 
But whilst I advocate this theory of floating ice to account for 
the phenomena in this particular district, I admit that there are 
some difficulties with which the theory has to contend. For ' 
example, if the rock on North Berwick Law, described by Mr 
Stevenson, was smoothed and striated by a mass of clay and stones 1 
pushed and pressed against it, what has become of this detritus ? 
because the rock now stands at least from 20 to 30 feet above the 
detritus at its base. The same remark may be made as to the 
striations on the rocks at Stirling Castle and Abbot’s Craig, which 
are still higher above any detritus now on the plains below these 
rocks. This difficulty, however, vanishes, when regard is had to the 
enormous denudation in every part of Scotland, of which there is 
ample evidence. Moreover, in the case of North Berwick Law, there 
is the remarkable hollow in the detritus along its base on the north 
side, to which reference has been made, showing that the detritus 
there has been scooped out to a considerable extent, and this may 
have happened after the smoothing and striation of the rock. 
