190 



SOME GEOCxRAPHICAL NOTES, ETC., 



The trellis-work drainage of the summit of Ben Lo- 

 mond (2) seems to show that this diabase plateau is dis- 

 sected along a similar series of fault-planes running north- 

 west to south-east. There is here, however, also a set of 

 cross-faults, and together they have determined the rect- 

 angular shape of the top of the plateau. 



My belief is that the whole island is dominated by fault- 

 blocks and fault-planes, some of which are no doubt later 

 than the intrusion of these diabase sills. Hence the Mount 

 Field Plateau offered unequal resistance to the agents of 

 erosion, with the result stated. This theory must of course 

 be tested further in the field. 



The second problem concerns the agents which have 



Held Wetl 



Field E2isr- 



Wherrer 



"Moraines 





Fig. 2. — Block diagram of the Plateau looking west. The parallel arrangement of the 

 valleys and lakes is apparent. Notice the "shelf" of tarns, the cirque of Lake Seal, and 

 "K" Col. A glacier 5 miles long descended the Broad River Valley. 



given rise to the remarkable topography (see Fig. 2). We 

 have here offered to us the same difficulties as are met 

 with so generally in the elevated portions of the temperate 

 zone. The special facies of the region is due to glacial 



(2) P. & P. Roy. See. Tas., 1913. Map by Colonel Legge. 



