Notes 0)1 the L'dydale Limestone. S9 



330 feet, and allowing for the average dip of 40°, tiiis would 

 mean a vertical thickness of about 220 feet, but this is only 

 so far as it is at present ex])osed. Its eastern limit may be 

 considered to be about alread}'- reached, for ahnost immedi- 

 ately flanking it on that side may be seen an extensive series 

 of quartzite and conglomerate strata, running conformably 

 with the limestone ; but on the west it is not yet deflned, as it 

 is still partly covered over with basaltic soil and decomj)osing 

 basalt. (See Fig. I.) 



About half a mile off, or rather less, to the west, and on 

 the other side of the valley, are a series of sandstones, shales, 

 and mudstones exposed beneath the basalt in the jyielbourne 

 Road cutting, and seen to be dipping in the same direction 

 as the limestone. 



The lateral extension of this Lilj^dale limestone is a 

 matter of much uncertainty. It is generally believed to be 

 like most other Silurian limestones, and especially in Vic- 

 toria, a mere lenticular or cake-like patch that ra])idly thins 

 out in all directions, but as the country in the neighbour- 

 hood is completely covered over with soil, trees, and verdure, 

 it must remain more or less a matter of conjecture, until 

 someone is enterpiising enough to prospect the country, if 

 not with a diamond drill, at least with a geological cheese- 

 borer. Its uovtltem extension has not been observed at all, 

 but what looks somewhat like a southern extension of it 

 may be seen in the shape of two bosses of the same kind of 

 limestone in the side of the railway cutting, about three- 

 quarters of a mile towards Melliourne, and somewhere about 

 on the line of the strike of the limestone at Cave Hill quai'ry. 



As it is hardl}^ conceivable that the great thickness of the 

 Cave Hill limestone, however lenticular it may be, can thin 

 out so rapidly as all this, these two bosses, or boulders, in 

 the railway cutting are probably mere outlying boulcleis of a 

 southerly extension of the limestone that is mainly concealed 

 beneath the surface. (See Fig. 2.) 



The general colour of the Cave Hill limestone, as it 

 appears in the quarry, when looked at as a whole, and from 

 a distance, is cream, or almost white, especially on weathered 

 exposures; but when freshly broken, it is of different shades 

 of dark or light bluish grey, ])inkish biown, or grey with 

 pinkish brown patches. It is for the most part semi-crystal- 

 line, is here and there somewhat brecciated on a small scale, 

 and is in some ])laces roughly oolitic (a slide of an oolitic 

 specimen on view). 



