IN WINTER QUARTERS WITH CAPTAIN SCOTT 239 



My first lecture was on the principles of physiography. 

 Dr. Bill assisted me to draw some sketches on large sheets 

 of paper, which I pinned on the pudding-board. This rested 

 against a chair on the table, and was lighted by our acetylene 

 branch ! Cherry drew a sketch of the author and pinned it 

 on the gas-jet as a screen. I discussed the evolution of a 

 land surface from an "infantile " plain, such as that of Red 

 River, Canada, through various stages of uplift to the 

 " senile " condition of a peneplain. 



I had made several small models in plasticene, and believe 

 the lecture was fairly successful ; for Simpson said he started 

 sleepy and ended wide awake ! 



I based most of my lecture on my recent work on the 

 geology of the Federal Capital Territory in Australia, and 

 the substance thereof is given in the following paragraphs. 

 This region (about 100 miles each way) illustrates almost 

 all the new concepts in the evolution of a land surface. 



Before the faulting the rivers flowed over fairly open 

 country as the Upper Yass River does now. The Murrum- 

 bidgee River rose on the north of the Tindery Range and 

 the Snowy River on the south. An ancient fault plane 

 assisted the Murrumbidgee to capture the snowy tributaries 

 at Tharwa. The country was broken by two main north- 

 south faults. Thus the head of Yaas River was cut off" to 

 make Lake George. Molongolo River managed to saw its 

 way down through the scarp (as it rose) and so formed the 

 Molongo Defile. All the old snowy tributaries (Upper 

 Murrumbidgee, Gudgenby, etc.) preserved their southward 

 direction as they cut deep gorges in their uplifted beds. 

 These tributaries form " boat-hook " bends where they join 

 the big river. The present divide at Cooma is an insignificant 

 wind-gap. 



The old river-bed draining the Lake George area (which 

 is seventeen miles long) is preserved as a deposit of huge 

 quartz boulders two hundred feet above the lake at Geary's 

 Gap. This may be termed a " dead river." The silts of 

 Lake George are still being added to, and hence this country 

 is below base-level, and may be described as embryo topography. 

 The narrow gorge of the Molongo and those of the Cotter 

 and Gudgenby exhibit infantile erosion features. The lower 

 Molongo River flows through a deep but wider valley with 



