Crawrorp.—On Bidwill’s Front Hills. 417 
plains is not much above the sea-level, let us say 20 or 80 feet, while the 
height of the ridge in question, I should estimate, in its highest part, to be 
fully 300 feet above the sea. Now this is higher than the level of Greytown 
or Carterton, and the corresponding level will probably be found in the 
middle of the Taratahi Plain. 
At first sight there is nothing extraordinary in finding a spur running 
out from the mountains into a plain, but when we examine the structure of 
this ridge we find much upon which to speculate. I am aware that there 
are some remains of old rocks, apparently belonging to the Rimutaka 
series, in the core of the ridge in question, because years ago I found them 
myself, but the mass of the range appears to be entirely composed of river- 
borne gravels and clays (perhaps the latter would be better described as 
muds). The cuttings for the formation of roads bring this point more 
clearly to view than formerly, 
Now this ridge having been formed of river-borne gravels and clays, the 
water at the time of its formation must have stood or run ata higher level 
than it, the ridge, stands at present, and either great denudation of the 
lower valley must since have taken place on both sides of the ridge, 
or the slope of the ridge must show a tendency to a termination of 
the deposit, either as a talus of materials dropped into a lake or as a finish- 
off of the deposit, when the rivers stood at a level of several hundred feet 
higher than they do now. 
Bidwill’s range is clearly a continuation of the deposits of gravels and 
clays which are found on the front ranges of the Huangaroa station, and 
through which the Ruamahunga has burst, leaving the former range 
isolated. 
It is conceivable that the Ruamahunga and its tributaries ran originally 
along the ranges on the western side of the Wairarapa, until, by the in- 
crease and spread of their deposits, they gradually forced the bed of the 
main river to the eastern side of the valley and against the eastern ranges. 
If at this time we suppose the river to have had a channel over three hun- 
dred feet above its present level, we can account for the formation of 
Bidwill’s range. Afterwards the river would cut its channel through its 
own deposits and carry its material further down the valley. 
I am more disposed to believe in the existence of a former barrier and 
a great extension of the present lake, than to suppose the immense denuda- 
tion of previous deposits of gravel and clay which is probably involved in 
any other supposition. The general evenness of the Wairarapa Plain seems 
to point to a spreading of the surface materials under lake water, and I 
think the appearance of the lower valley, approaching the lake, and 
including Bidwill’s range, gives a similar impression. We might call in 
48 
