NEW ZEALAND. 44] 
feet thick, and inclined to the east 60°. Yet I could not satisfy myself 
that these were planes of deposition. 
No fossils were observed in this rock. <A single Pecten was 
handed me by Mr. Swain, who picked it up on the Pahia beach, on 
the west side of the Bay; but he could not be certain of its locality. 
A few other imperfect specimens were received from Mr. Waterford ; 
but these also were of undetermined locality. Although we suspect 
the rock to be one of the earlier deposits, belonging in the geological 
series below the coal, we have no decided evidence on this point 
from organic remains. Dr. Dieffenbach places the formation in the 
silurian period. 
The rock afforded us few minerals. With the exception of the 
quartz and iron referred to, and some pyrites, nothing was found in 
the neighbourhood of the Bay. Specimens of manganese are brought, 
it is said, from the Thames; but we know nothing of its position. 
Copper mines have recently been opened in New Zealand; but we 
are not informed as to the containing rock. 
Decomposition and Degradation of the Rocks.——The soft argilla- 
ceous portions of the rock described, undergo rapid decomposition 
when exposed to the action of air and water. Some fresh sections had 
been lately made by cutting a road over the hills leading from the 
Messrs. Williams’s farm, near T'aiamai, towards the Bay: and at the 
time we travelled that road, hardly two years afterward, the rock was 
altered and crumbling to a depth of two feet. Blocks, two or three 
cubic feet in size, lying on the roadside near where they were thrown 
out at the time of the excavation, were so decomposed as to fall to 
pieces when struck lightly with a hammer. The altered rock appears 
fissured in every direction, and is divided by thin ferruginous seams 
into pieces about the size of the fist. ‘The decomposition in progress 
sometimes changes the light yellowish colour toa bright red, owing 
to’ the included iron. 
The hard siliceous varieties of the rock produce nearly the same 
results of decomposition. Over the hills, the peculiar character of the 
rock beneath can seldom be distinguished in the soil, as its character 
is so uniform; though along the cliffs the difference is very appa- 
rent. Alteration takes place more slowly in these harder rocks, and 
the cliffs are therefore abrupt rugged heights, decomposed only at the 
summit; while those consisting of the softer rock, are less steep, with 
a more rounded contour, and usually covered nearly to their foot 
with the crumbling clayey soil. 
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