407 
of Port Phillip , N. S. Wales. 
from these solid masses, either by the shock that first introduced 
them to their present situation, or by the subsequent operations 
of time and weather. 
An opinion is general among the settlers, that the stones which 
form these rises have been vomited forth by the volcanos that are 
usually found in their vicinity. The circumstance of these rocks 
either running in lines or appearing in rounded tumuli—and these 
are the decided characteristics of these formations—would indi¬ 
cate however that they have originated in situ from an upheaving 
force beneath, which, from the small size and frequently well 
defined sides of the rises, must have operated at a very moderate 
distance from the surface. This view is confirmed by several 
features of these “ rises,” which I shall immediately describe, and 
which further suggest the inference that, in some cases at least, 
some interval must have elapsed between the era which produced 
the vast quantity of trap, or whinstone rock, that has overspread 
a large portion of the country, and the subsequent, appearance of 
the rises; to both of which occurrences we are doubtless in¬ 
debted for many of the present fine arable and pasture lands of 
the district. 
One of the features I have alluded to, as illustrative of these 
rises, is the hollow sound they emit in passing over them, which 
is especially perceptible under the feet of a horse. Cavities have 
been frequently discovered, on clearing away the loose stones and 
earth, and excellent fresh water is occasionally met with below. 
At a station, about two miles north of lake Colac, accident dis¬ 
covered on one occasion a cavity of this description, where a 
subterranean stream of fine fresh water, in ample quantity, ap¬ 
peared to be wending its course to the neighbouring lake. A pump 
was speedily inserted, and the station has since been unfailingly 
supplied during all seasons. Doubtless, supplies of this sort, 
though invisible at the surface, may be thus met with in similar 
descriptions of country, the water probably in most instances 
running at the base of the trap formation. 
Another feature occurs among the rises at Colac. The soil in 
this locality is very productive: many of the rises are richly 
grassed, while upon others small portions of rock still rear their 
