[16 
K THE GEELONG NATURALIST. 
Once we get our sand, whatever be its nature, we soon 
find that when it gets beyond the action of the tides, the wind 
tends to accumulate it into hills or hillocks, provided of 
course that the coast line is of a nature to allow such taking 
place. "These hills or hillocks built up of sand by the agency 
of the wind are known as “ Sand-dunes." 
Looking at one, or a series of these dunes, the observer is 
at once struck by the fact that they possess a very much 
more gentle slope on one side than on the other, and it is' not 
long before he finds out that the gentle slope faces in the 
direction from which the prevailing winds come, while the 
comparatively sudden and steep slope faces in the opposite 
direction. He will also notice that the superficial sand on 
the gentle slope is in almost continual motion. The wind 
gives it no rest, but forces the loose grains up till they reach 
the summit, when they roll over and arrange themselves on 
the leeward side at a much steeper angle. A fresh supply of 
sand is forced up in its turn, and gradually but surely we get 
an increase in the elevation of our dunes, and in the amount 
of coastal région they cover. 
These accumulations, which, if left to themselves, event- 
ually become very great, do not always remain loose, inco- 
herent masses, but sometimes become consolidated into hard 
rock. If our dunes consist of silicious sand thesg#may 
become sandstones by the deposition of some cementing 
material, such as carbonate of lime or oxide ofiron. Ifa cal- 
careous sand, it would, upon consolidation, be called a lime- 
stone. In the latter case the rain water in trickling through 
the sandy mass would dissolve some carbonate of lime during 
its passage, and when this water would be subsequently evap- 
orated that which it held in solution would be precipitated 
round the grains in its neighbourhood and would effectually 
bind them together. 
Limestone formed in this way is common along the 
Victorian coast, for instance at Cape Schanck, Queenscliff, 
Barwon Heads, Spring Creek, Gellibrand coast and 
Warrnambool, and has had the name of * Dune Limestone " 
applied to it. | 
. Itislargely quarried at Warrnambool, but itis of very 
little use for building, though occasionally used locally 
for that purpose. This rock is commonly called a “ sand- 
stone," but several analyses which have been made of 
samples from different localities prove that it contains as. 
much as 8o per cent. and upwards of carbonate of lime. The 
first gentleman to call this rock a limestone based upon . 
analysis was, I believe, Mr. T. E. Rawlinson, C.E., at one 
time secretary to the Royal Society of Victoria, who, as far 
back as June, 1877, communicated his observations on the: 
coastal sand dunes of the Western District, to that Society. 
Two years previously, Mr. R: Etheridge, jr., had communi- 
