BY GRAHAM OFFICER, B.SC. - 155 
From what I have said about the structure of Mount 
Olympus, it might be expected that sandstone should form 
the bed of the Cuvier Valley. But, as before remarked, only 
bosses of greenstone appear through the button-grass, except 
at the upper end, where masses of sandstone and conglomerate 
occur as well. We also found an outcrop of sandstone at one 
point on the south side of the valley, about half-way up its 
course. There can be little doubt that the original relative 
levels of the sandstone and the greenstone have undergone 
considerable changes, but it is quite impossible to say yet 
what the extent of such changes may be. There are several 
feasible explanations of the greenstone masses in the Cuvier 
Valley. 
1. They may simply be the relics of the greenstone which 
once overspread an originally uneven surface of the sand- 
stone. Once worn down to a certain level, the sandstone, on 
account of its horizontal bedding, would not tend to form any 
prominent projections, and would be rapidly concealed 
beneath the accumulations of peaty matter. The greenstone, 
on the other hand, on account of its greater hardness and 
way of weathering, would project here and there through the 
bogs. Some of these masses may have come from Olympus. 
2. They may represent dykes through the underlying 
sandstone. 
3. The Cuvier Valley may occupy the line of a great fault, 
which seems to me not improbable. 
In the accompanying map I have adhered to the first 
explanation. 
We did aot see a sign of the older palseozoic rocks repre- 
sented in Mr. Johnston’s map as occurring in the Cuvier Valley. 
We traversed a good deal of the country lying to the south of 
Lake St. Clair, and found it all of the same general character, a 
succesion of button-grass swamps or flats, with low green- 
stone ridges between. Bedlam Walls, at the entrance to the 
Navarre Plains, consist of a great mass of greenstone, which 
differs from that of Oylmpus in not being columnar. The 
base of Bedlam Walls is about 60 feet above St. Clair. The 
country between the lake and the Nive Plains, some 18 miles 
distant, is all of the same general character, greenstone ridges 
and button-grass flats. The Nive Plains occupy a broad 
depression, five or six miles across, sloping in towards the River 
Nive. They are of a roughly undulating surface, covered 
with dead and fallen trees, the result of a severe frost 50 or 
60 years ago. These plains are basaltic, the basalt in places 
being highly vesicular and decomposed. At the Nive bridge, 
at Marlborough, columnar structure is well developed. 
At “ Bust-gall”. Hill, several miles further on, the green- 
stone country is again reached, forming a plateau considerably 
above the Nive Plains. From here right on to the Dee the 
