48 



quartzites the siliceous cement has absorbed the original grains 

 of sand, which cannot always be clearly distinguished from 

 the cement that has blended them all together. In the case 

 of the sarsen stone, the cement, whilst intensely siliceous, is 

 distinct from the- granular constituents of the rock. 



Another point of difference between the two classes of 

 rock is that whilst the Cambrian rock is regularly bedded, 

 possessing a rough surface, and tends to split along the 

 bedding planes, the sarsen stone is generally more or less 

 spheroidal, or irregular in outline, and generally possesses a 

 smooth and glazed surface. It is the finer-textured rocks that 

 exhibit the more complete silicification, as in the case of sands 

 and fine gravel : the coarser gravels are frequently strongly 

 cemented, but they do not show the same clean fracture as is 

 seen in the finer-grained examples. 



II. Pumice and other Substances found as Sea-drift 

 near Cape Banks. 



I am indebted to Mr. G. A. Payne, late Head Keeper at 

 Cape Banks Lighthouse, for a number of interesting objects 

 that he has collected from the beach in that locality. The 

 more interesting of these comprise pumice, scoriaceous lava, 

 torbanite, asphaltum, and native resin. 



PUMICE. 



Mr. Payne states that he has collected from the beach 

 three examples of this rock. He says that "two were about 

 the size of a small loaf of bread and the other the size of two 

 loaves.'" The latter specimen was kindly donated by Mr. 

 Payne to the University Museum. It is slightly water-worn 

 and, roughly, pear-shaped. It measures 13 in. in length and 

 2(H in. in transverse circumference. It is a characteristic 

 example of its kind, greyish-white in colour, rough to the 

 feel, open and vesicular in structure, with numerous large, 

 elongated vesicular gas spaces. The central portion of a 

 second specimen, also forwarded by Mr. Payne, has precisely 

 the same features. The sjDecimens in each case occurred on 

 the southern side of Cape Banks, and were found high up 

 among the sandhills, where, Mr. Payne thinks, they must 

 have been buried for years. 



The occurrence of drift-pumice in this locality was quite 

 unexpected and is difficult to explain. Although the 

 Millicent and Mount Gambier volcanic fields are not very 

 distant from Cape Banks, no pumice is known to occur on 

 either of these fields, and if there was, there is at present no 

 running water that might account for their transportation to 

 the coast. Neither is pumice known to occur along the 



