BY R. H. CAMBAGB. 433 



"builder as trachyte is quarried. The Hawkesbury Sandstone of 

 the Triassic period shows intermittently towards the Wollondilly 

 for a distance of 22 miles, and its terminal point is of interest, 

 as, in this locality, it marks the south-western edge of the great 

 Permo-Carboniferous coal basin which extends approximately 

 from the Hunter to the Clyde River. After passing the 22-mile 

 post, an area of porphyritic and granitic rocks is entered, and 

 this continues to within a few hundred yards of the Caves, where 

 tlie formation changes to Silurian limestone. 



The plants met with are for the most part those which belong 

 to the coastal area, but with some notable exceptions. The 

 effects of climate and aspect are particularly noticeable along the 

 country passed over. Although Bowral is only about 30 miles 

 from the coast, it is some distance back from the edge of the 

 plateau, and therefore to some extent deprived of coastal influence 

 by the cliffs of the Illawarra Range which rise almost perpen- 

 dicularly to a height of nearly 2000 feet. On the western side 

 of Bowral, towards Wombeyan, there is more exposure to western 

 influence, the result being that the cold south-westerly winds 

 have free access to this area, including the valley of the Wollon- 

 dilly, and we look in vain for the dense vegetation of the coast 

 or of those sheltered valleys in the Blue Mountains which are 

 protected from the chilling and drying influence of the westerly 

 gales. 



Rainfall is also an important factor in the regulation of plant 

 life, and its effects may be seen along the country extending 

 from the coast to Bowral and Wombeyan. According to the 

 records at the Sydney Observatory, the quantity of rain which 

 falls on the coast at Kiama and Wollongong is greater than that 

 at Bowral, from which point it again diminishes towards Taralga 

 just beyond the Caves. The records are as follows: — Kiama 

 54-37 inches (average for 19 years), Wollongong 43-09 (31 years), 

 Robertson 67-95 (14 years), Bowral 39-11 (20 years), Taralga 

 29-47 (19 years), and Goulburn 25*91 (48 years). 



The relation between the rainfall and the vegetation over the 

 area in question is most instructive. In Illawarra we find dense 



