PROCEEDINGS OF SECTION C. 447 
known fossiliferous strata. A large portion of the area must 
still have been submerged, but such was not the case for all of it, 
as the high lands of Dundas and the northern part of Normanby 
are old land surfaces. 
One deposit recognised consists of the disintegrated remains of 
granitic, metamorphic, and sandstone rocks belonging to the 
Grampian series. 
There are also beds of ironstone gravel, of no great thickness, 
but covering the surface of the country like a mantle, and resting 
alike on paleozoic, mesozoic, and tertiary strata. A gentleman 
of my acquaintance, who travelled a good deal in this region, was 
so struck by the prevalence of gravel over such wide areas, that 
he could only explain its origin by supposing that it had fallen 
from the clouds. A much more feasible explanation can, however, 
be given. The iron has been precipitated as limonite, or bog-iron 
ore, from water holding it in solution. Fine mammillated nodules 
of bog-iron ore can be obtained*at the bottom of some of the 
swamps in various parts of the district, while small pea-shaped 
- fragments are abundant in every watercourse. The iron oxide 
has also served as a cementing material for masses of sand derived 
from the decay of the rocks just mentioned. The iron itself has 
probably come, in the first instance, from decomposed trappean 
and basaltic rocks, remnants of which still exist in certain portions 
of the region. This explanation would not, perhaps, suffice if the 
swamps and morasses had always been confined within their 
present limits, as ironstone, evidently zz sztw, is abundant in 
places where water now seldom remains on the ground for any 
length of time. But the country is generally level, and it would 
only require a heavier rainfall to flood a great part of it. Professor 
Tate has given sound reasons for concluding that Southern 
Australia has undergone a gradual dessication, the rainfall in past 
ages having been much greater than at present.* Such being 
the case, large tracts would be covered by permanent swamps, 
and the precipitation of iron oxide over an extended area is 
easily accounted for. In fact, the presence of these extensive 
deposits of bog iron-ore lends, I think, strong support to the 
arguments of those who claim for Victoria a humid climate in the 
Pliocene period. It is not, of course, contended that this iron- 
stone gravel was wholly formed 7 stu, a great part having 
undoubtedly been transported by creeks and rivers, whose course 
has been changed, or which have now ceased to flow. 
Incidentally, I may refer here to the numerous lakes and 
swamps which are scattered about the southern half of Lowan. 
The minds of not a few of the more observant residents in the 
county have been much exercised concerning the mode of their 
formation. Being mostly salt, the first idea has generally been 
* “ Post-Miocene Climate in South Australia.” Roy. Soc. S.A., 1885. 
