104 B. N. A. BOUNDARY COMMISSION. 
lignite beds, forms a resistant capping. Where no such protection is 
afforded, rounded mud-lumps are produced from the homogeneous 
arenaceous Clays. Waste proceeds entirely by the power of falling rain, 
and the sliding town of the half-liquid clays in the period of the 
melting snow in spring. The clay hills are consequently furrowed 
from top to base, by innumerable runnels converging into larger 
furrows below. The small streams rapidly cutting back among 
these hills, have formed many narrow steep-walled gullies, while the 
larger brooks have produced wide flat-bottomed vallies at a lower level, 
in which the streams pursue a very serpentine course. Denudation is 
even here, however, still going on, as from the frequent change in 
the channel of the stream, it is constantly encroaching on the banks 
of the main valley, undercutting them and causing landslips. The 
method of the immense denudation of Tertiary beds, which is proved to 
have taken place over the area of the western plains, is explained by 
the degradation still going on in this way along their present borders. 
252. The general section at this place, which though not exposed as 
a whole at any one spot, is remarkably clear; is naturally divided into 
four parts. 
Taking first the highest bed seen, the order is as follows (Plate VIL., 
Fig. 2.) :— ) | 
a, Yellowish sand and arenaceous clay, sometimes indurated in certain 
layers and forming a soft sandstone. It forms the flat plateau-like 
tops of the highest hills seen. About 50 feet. 
6. Clays and arenaceous-clays, with a general purplish-grey colour when 
viewed from a distance. About 150 feet. 
y. Yellowish and rusty sands, in sorfe places approaching arenaceous 
clays, often nodular. About 80 feet. 
6. Greyish-black clays, rather hard and very homogeneous, breaking 
into small angular fragments on weathering, and forming earthy 
banks. About 40 feet seen. 
The whole of the beds appear to be conformable, and disregarding minor 
irregularities, are quite horizontal to the eye. 
253 The clays and arenaceous clays of the upper part of Division 
B. are very regularly bedded, and include a lignite-bearing zone. Three 
lignite beds, of from one to two feet each in thickness, were observed, but 
they are separated from each other by rather wide clay partings, and are 
not pure or of good quality. A bed rich in the remains of plants, 
immediately overlies the upper lignite. It is composed of a very fine, 

