HuTTON. — Qeologij of the Trelissick Basin. 



395 



and Cragieburn Saddle. The north-west corner of the basin, 

 however, is formed by another short syncHne which runs nearly 

 parallel to the first. As the West Coast Road enters the basin 

 on its eastern side, it does not run along the syncline until after 

 passing the Thomas River. I observed three faults in the 

 district, but there may be others. The first crosses the Porter 

 River just above the first limestone gorge, south of Prebble 

 Hill,* and runs north-westerly to the north side of Castle Hill ; 

 its downthrow is to the north-east ; this fault is clearly seen on 

 the left bank of the Porter River (PI. XXV., Section IV.). The 

 second fault runs from Parapet Hill south-west, and crosses the 

 Broken River at the small gorge under Sugarloaf Hill (PI. XXV., 

 Section II.) with a downthrow to the south-east. The third 

 fault runs east and west along Waterfall Creek, which is the 

 first affluent the Broken River receives from the west after enter- 

 ing the basin ; its downthrow is to the north. 



River gravels are widely spread over the basin. They form 

 the summit of Long Spur, and are found on the ridge behind 

 Castle Hill, at an elevation of nearly 3,000 feet above the sea. 

 I have, however, omitted them in the sections, as I paid no 

 particular attention to them. I saw no marks of glacier action ; 

 indeed such marks could not be expected to occur, for during 

 the last great glacier epoch the Trelissick Basin must have been 

 a snow-field. 



The following altitudes may be found useful : — 



Wext Coast Road — Feet. 



Lake Lyndon . . . . 2,743 



Crossing at River Porter . . 2,266 



Terrace N. of Eiver Porter 2,481 



Terrace S. of Eiver Tliomas 2,285 



Crossing at River Thomas 2,178 



Terrace at Hotel . . . . 2,371 



Terrace S. of Broken River 2,390 



Crossing at Broken River 2,094 



Terrace N. of Broken Eiver 2,350 



Craigieburn Saddle . . 2,619 



Lake Pearson .. .. 2,085 



Waipaea System. 



This system is largely developed on the north and east sides 

 of the basin : a detached portion also occurs at the most 

 southerly point, in Coleridge Creek. Its upper member is a 

 white argillaceous Umestone (Amuri limestone) generally with a 

 platy structure, breaking up into irregular flakes, more or less 

 parallel to the bedding. Below this comes sandstone or grit, 

 underlain by a thick bed of marl ; whilst the lower part of the 

 system consists of grey or green sandstones, very variable in 



* This is the same as Ram Hill in Mr. McKay's Report. The name of 

 " Ram Hill" is not known to Mr. Enys. 



