BY C. A. SUSSMILCH AND H. I. JENSEN. 163 



iv. Descriptive Geology. 

 Most visitors to the Cauobolas travel by the Cargo Road as far 

 as German's Hill, and then turn off on to a branch road to the 

 south, which leads to the top of the Old Man Canobolas. From 

 a tourist's point of view this is an excellent trip, as, from the top 

 of the Old Man can be seen one of the most extensive views in 

 New South Wales. From a geologist's point of view, however, 

 this is the least interesting road to take, as the rock-exposures 

 are not particularly good, nor do we meet with many rock-types. 

 A much more interesting route is that by the Towac Road. This 

 road, soon after leaving Orange, crosses the Molong-Forbes Rail- 

 way line near the Orange Racecourse, where some good examples 

 of columnar basalt may be seen, both in the railway cuttings and 

 ill the adjacent municipal quarries. From here, onward for 

 some miles, the road passes through some of the richest orchard 

 a:id agricultural land in the district, the rich soils being derived 

 from the decomposition of the andesite lavas. Passing the 

 Canobolas Public School, the andesites give place to trachytes 

 and comendites until the road reaches Summer or Molong Creek, 

 where basalt again makes its appearance. The road now, after 

 pissing the Tosvac School (8 miles from Orange), plunges into a 

 narrow gorge between The Pinnacle and Watt's Pinnacle, for 

 half-a-mile, and then ends in a beautiful valley entirely encircled 

 by hills, and known locally as the " Devil's Hole." We are now 

 in the centre of the most interesting part of the Canobolas 

 Mountains. Immediately to the west stand the Young and Old 

 Man Canobolas; to the south-west are Towac Mountain and the 

 Bald Hills; to the north, Johnston's and Watt's Pinnacles; and 

 to the north-east stands The Pinnacle. This is the centre of the 

 oldest and most acid lavas (comendites, etc.), and surrounding 

 them, in a roughly concentric fashion, in the following order, are 

 the more basic trachytes, with their associated tuffs, then the 

 andesites, and finally the basalts. 



l.The Lava-Flows and Tuffs. 

 (a) The Leucocratic Trachytes. — These include comendites, pan- 

 tellarites, and the lighter-coloured trachytes, all of which are 



