Geology.] 
NATURAL HISTORY. 
589 
the author of Travels in Sicily, and of the Survey of the 
Mediterranean recently published by the Admiralty, in- 
forms me, that he has seen these concretions in Calabria, 
and on the coasts of the Adriatic; — but still more remark- 
ably in the narrow strip of recent land, (called the Placca,) 
which connects Leucadia, one of the Ionian Islands, with the 
continent, and so much resembles a work of art, that it has 
been considered as a Roman fabric. The stone composing 
this isthmus is so compact, that the best mill-stones in the 
Ionian Islands are made from it ; but it is in fact nothing 
more than gravel and sand cemented by calcareous matter, 
the accretion of which is supposed to be rapidly advancing 
at the present day. 
The nearest approach to the concreted sand-rock of Aus- 
tralia, that I have seen, is in the specimens presented by 
Dr. Daubeny to the Bristol Institution, to accompany bis 
excellent paper on the geology of Sicily * ; which prove that 
the arenaceous breccia of New Holland is very like that 
which occupies a great part of the coast, almost entirely 
around that island. Some of Dr. Daubeny’s specimens from 
Monte Calogero, above Sciacca, consist of a breccia, con- 
taining angular fragments of splintery limestone, united by 
a cement, composed of minute grains of quartzose-sand dis- 
seminated in a calcareous paste, resembling precisely that of 
the breccia of Dirk Hartog’s Island : and a compound of 
this kind, replete with shells, not far, if at all, different 
from existing species, fills up the hollows in most of the 
older rocks of Sicily ; and is described as occurring, in 
several places, at very considerable heights above the sea. 
Thus, near Palermo, it constitutes hills some hundred feet in 
height; — near Girgenti, all the most elevated spots are 
* Edinb. Phil. Jour. 1825. pp. 116, 117, 118, and 254-5. 
