2 Observations on Sand-dunes 



the top of the mouth of the drive, there was then confined 

 ah- (not compressed), as follows : — Jn the drive, 1,400 cubic 

 feet; in cross-cut, 2,520 cubic feet; total, 3,920 cubic feet. 

 When the water rose to its highest level (52 feet, equal to 

 about one-and-a-half atmospheres) in the shaft ; the confined 

 air was then compressed, according to Boyle and Mariottes' 

 law, to two-fifths or a little less than one-half of its original 

 volume. The space thus occupied by the compressed air, 

 under a pressure of a column of water equal to 1J 

 atmospheres, would be 1,568 cubic feet. The measurements 

 of drive, cross-cut, and height of water in the shaft are 

 only approximate, having been given by the mining manager, 

 Mr. Jackson, roughly ; but they are sufficiently near for all 

 practical purposes, and fully establish the fact that there was 

 a large quantity of compressed air surrounding McCaviston 

 at the end of the drive. 



Art. IV. — Observations on Sand-dunes of the Coast of 

 Victoria. By R Etheridge, Esq., Jun. 



(Of the Geological Survey of Scotland.) 

 [Read 8th June, 1874.] 



The general characters and nature of the sand-dunes of 

 the coast of Victoria are too well known to the members of 

 the Royal Society to need any lengthened description from 

 me. I shall, therefore, confine myself to a . few general 

 observations connected with the subject. 



The usual aspect of that portion of the coast occupied by 

 dunes is low and sandy, rising here and there into hills afew 

 hundred feet high, and composed almost wholly of blown sand. 

 Portions of the coast at which these phenomena may advan- 

 tageously be studied are, amongst others, Anderson's Inlet, 

 Point Nepean, and the coast line at intervals from Cape 

 Otway far into the colony of South Australia. From 

 accounts given by various writers, we may consider the sand 

 of the coast as forming three kinds of hillocks, viz., high 

 well-grassed lengthened ridges ; similar detached more or 

 less conical hills ; and lastly, shifting dunes, devoid of 

 vegetation, and changing their form and position with every 

 breath of wind. One of the more remarkable instances of 

 the long ridge-like dune is that described by Mr. C. S. 

 Wilkinson, on the west side of the Aire River, near Cape 



