240 
THE GEOLOGY OF NEW ZEALAND. 
This leads to the consideration of the sedimentary deposits. 
These are chiefly marine or lacustrine. The marine are formed 
in the way already mentioned, and the shoal seas around a 
great portion of these Islands mark their extent. On the 
western coast of the North Island, it is evident vast tracts of 
land have been gained from the sea, by the deposits of the 
Wanganui, Rangitikei, and Manawatu rivers. Near the 
coast, in that part, the land is generally low, covered with 
gravel or shingle, and with large quantities of drift timber; 
inland it is alternate swamp and grass with parallel ranges of 
ancient sand hills, now covered with a growth of fern. Near 
the sea, and especially near the mouth of rivers, large quanti¬ 
ties of sand are blown up from the shore, and form drifting 
sand hills. This is, evidently, a portion of the matter brought 
down the rivers by the floods; the mud being precipitated to 
the bottom of the sea by the coagulating action of the salt 
water upon it, there gradually forms a compact mass: but 
the sand having nothing to fix it, is, by constant attrition, 
washed finer and finer, and then thrown up by the high tides 
in large quantities on the shore, whence the sea breeze 
speedily conveys it inland. 
The vallies of New Zealand are not numerous or extensive ; 
indeed the almost entire absence of them, and the acute pointed 
hills, which arc only separated from each other by deep ravines, 
are to be considered as amongst the peculiar features of this 
country, and as most of these have never been touched by the 
hand of man, they enable the Geologist to observe the exact 
state in which they were first upheaved. The remarkable 
way in which the surface of these Islands was fractured when 
first elevated, is yet to be observed as plainly as though it had 
recently taken place; for whilst one side of a hill is covered 
with the debris of primitive rocks, gravel, and vegetable mould, 
the other is either ochre or pipe clay, destitute of any rolled 
stone, without soil; the fern also on one side is of a more 
luxuriant growth than on the other.* 
Another kind of sedimentary deposit remains to be noticed,— 
* The country is cracked at an angle of 45°. 
