850 OCCURRENCE OP A LIMESTONE-F LORA AT GROSE VALE, 



above. Much of the lower portion has, however, been cleared, 

 and only a few patches remain to indicate the once luxuriant 

 nature of the flora. 



The soil, in colour, is a brownish-white, and of a loose granular 

 texture. Where the rock is exposed, it is not unlike basalt, and 

 as such it is locally taken to be, a mistake probably influenced, 

 to some extent, by the vegetation. Where it is weathered, it 

 resembles a very soft sandstone. Mr. H. G. Smith* has recorded 

 deposits of similar limestone from Auburn and from Homebush. 

 Like that at Grose Vale, they occur as deposits in the Wiana- 

 niatta Shales. Mr. Smith informs me that the Gro.se Vale rock 

 contains more sand than the two deposits mentioned, but is 

 almost identical with that found near Lakemba, on the railway 

 between Belmore and Bankstown. Not being naturally exposed, 

 no botanical indications of these deposits were noted by liim. 

 Referring to the Auburn deposit, he sajs : " When first broken, 

 it is of a bine-grey colour, not much unlike basalt; it was spoken 

 of as ' blue metal ' by the quarrymen, who no doubt consider it 

 identical with the igneous rock bearing the same name. On 

 weathering, the limestone becomes lighter grey in colour." In 

 all these deposits no sign of organic structure can be detected 

 under the microscope. Mr. Smith classes them as hydiaulic 

 limestones. The normal soil of the Vale is that of the Wiana- 

 matta Shales, with the usual flora of stringybarks, ironbarks, red 

 gum, blackthorn, etc. 



The explanation of this very distinct and localised plant-com- 

 munity seems to be due to (1) the richness of the soil due to the 

 relatively large amount of lime present, with its accompanying 

 greater availability of plant-foods, and its improved j)hysical 

 nature; (2) the sheltered eastern aspect; and (3) the good rainfall. 



The following is Mr. Smith's analysis of the Auburn rock : — 



CaCOg =39-673% MnCOg =0-425% 



Clay =39-416% MgCO., =1-625% 



FejOg = 2-G86% Alkalies present as chlorides = 0-679% 



FeCOg =13-450% Water =2-260% 



* Smith, H. G., "Preliminary'Noteon Limestone occurring near Sydney." 

 Journ. Proc. Roy. Soc. New South Wales, xxvi., 189-2, p. 302. 



