Prof. James Geikie’s Address. 463 
it. Similar phenomena were encountered in regions where the drift 
underlies the Chalk—the latter presenting the appearance of having 
been smashed and shattered —the fragments having often been 
dragged some distance, so as to form a kind of friction-breccia under- 
lying the drift, while large masses are often included in the clay 
itself. All the facts pointed to the conclusion that these disturbances 
were due to tangential thrusting or crushing, and were not the result 
of vertical displacements, such as are produced by normal. faulting, 
for the disturbances in question die out from above downwards. 
Evidence of similar thrusting or crushing is seen in the remarkable 
faults and contortions that so often characterize the clays and sands 
that occur in the Boulder-clay itself. The only agent that could 
produce the appearances now briefly referred to is land-ice, and we 
must therefore agree with German geologists that glacier-ice has 
overflowed all the drift-covered regions of the peripheral area. No 
evidence of marine action in the formation of the stony clays is 
forthcoming—not a trace of any sea-beach has been detected. And 
yet, if these clays had been laid down in the sea during the retreat 
of the ice-sheet from Germany, surely such evidence as I have 
indicated ought to be met with. To the best of my knowledge the 
only particular facts which have been appealed to, as proofs of 
marine action, are the appearance of bedded deposits in the Boulder- 
clays, and the occasional occurrence in the clays themselves of a 
sea-shell. But other organic remains are also met with now and 
again in similar positions, such as mammalian bones and fresh-water 
shells. All these, however, have been shown to be derivative in 
their origin—they are just as much erratics as the stones and boulders 
with which they are associated. The only phenomena, therefore, 
that the glacialist has to account for are the bedded deposits which 
occur so frequently in the Boulder-clays of the peripheral regions, 
and the occasional silty and uncompressed character of the clays 
themselves. 
The intercalated beds are, after all, not hard to explain. If we 
consider for a moment the geographical distribution of the Boulder- 
clays, and their associated aqueous deposits, we shall find a clue to 
their origin. Speaking in general terms the stony clays thicken out 
as they are followed from the mountainous and high-lying tracts to 
the low ground. Thus they are of inconsiderable thickness in Norway, 
the higher parts of Sweden, and in Finland, just as we find is the 
case in Scotland, Northern England, Wales, and the hilly parts of 
Ireland. Traced south from the uplands of Scandinavia and Finland, 
they gradually thicken out as the low grounds are approached. 
Thus in Southern Sweden they reach a thickness of 48 metres or 
thereabout, and of 80 metres in the northern parts of Prussia, while 
over the wide low-lying regions to the south they attain a much 
greater thickness—reaching in Holstein, Mecklenburg, Pomerania, 
and West Prussia a depth of 120 to 140 metres, and still greater 
depths in Hanover, Mark Brandenburg, and Saxony. In those 
regions, however, a considerable portion of the ‘“ diluvium ” consists, 
as we Shall see presently, of water-formed beds. 
