GLACIATION OP THE OKKNEY ISLAITDS. 663 



tliey may liave come from the basin of the Moray Firth or the 

 eastern counties of Scotland lying to the north of the basin of the 

 Forth. The presence of blocks of limestone of Calciferous-Sandstone 

 age in the Odin- Bay section in Stronsa seems to indicate that a 

 portion of the ice which crossed Fife was deflected to the north ; 

 and even if the Saville boulder should prove to be of Scandinavian 

 origin, its position in the north of the group is quite in keeping with 

 the path which would be followed by the Scandinavian ice. 



It is a significant fact that nowhere in the Shetland Boulder-clay 

 did we find a vestige of the Secondary rocks of Scotland ; . and 

 though the evidence is merely negative, it nevertheless confirms 

 the foregoing conclusions. We are inclined to believe also that the 

 absence of marine shells in the same deposit, which we noted in 

 our previous paper, may probably indicate that a portion of the 

 present sea-floor round Shetland formed dry land during the climax 

 of glacial cold. We see, therefore, how the glacial phenomena of 

 Orkney furnish a striking confirmation of the views advocated by 

 Dr. CroU more than ten years ago. 



Though we visited nearly all the islands of the group and tra- 

 versed the greater part of the coast-line, we found no trace of gravel 

 kames or raised beaches indicating recent changes in the relative 

 level of sea and land. 



EXPLANATION OF THE PLATES. 



Plate XXVI. 

 Glacial Chart of the Orkneys. 



Plate XXVIL 

 Chart showing the probable path of the ice in the North Sea, 



