142 Historical Notes on the 



lake. A shingle -fan, descending from the northern slopes of the 

 Thirteen-mile-bush range crosses the valley here, to the existence of 

 which, combined with that at its opposite end towards the Wahna- 

 kariri, the lake, without doubt, owes its existence. Its level, when I 

 visited it, was very low, and I found that not only was no water 

 issuing from it and running towards the Acheron, but that the surface 

 of the water was fully three feet below the point of outlet, and the 

 intervening banks covered with grass. 



Thus the Acheron takes water from the lake, except by leakage, 

 only in spring or after heavy rain. My former supposition, therefore, 

 that the large and ever-flowing springs forming the River Porter, and 

 belonging to the Wahnakariri system form the real outlet of Lake 

 Lyndon, received additional confirmation. These springs are situated 

 205 feet below that lake, and at the northern foot of a large fan, 

 formed by several creeks bounding Lake Lyndon to the north. I 

 may here add that I passed Lake Lyndon on the 4th July of the same 

 year. The lake was then so unusually low that it was divided into two 

 distinct basins, of which the southern one was the largest, whilst the 

 northern, or that situated towards the "Waimakariri valley, occupied 

 only a very small area. The level of the larger basin was, according 

 to Mr. "W. Blake's levels, three inches above the smaller one, although 

 a narrow water-course was continually flowing from the former into 

 the latter. Thus, if there were no subterraneous outlet towards the 

 Waimakariri, it is evident that both basins would stand at the same level. 

 Descending the River Acheron towards its junction, we observe, 

 lying on the western slopes of the doleritic rocks previously described, 

 alluvial beds well stratified, with every appearance of having been 

 deposited in a lake as a lateral delta. In advancing towards its junction 

 with the Rakaia, large beds of silt form high white cliffs, mostly con- 

 sisting of an almost impalpable mud of a bluish white or yellowish 

 colour, covered by banks of shingle, which show hi many places by 

 their flattened shape that they were deposited in a lake. Fighting Hill 

 forms the boundary of this former large lake, and precipitous cliffs, 

 several hundred feet high, situated here at the turn of the river, 

 exhibit well how it was filled up by shingle brought down by the large 

 rivers falling into it, covering and preserving the silt beds, so 

 much more easily destroyed. Moreover, we can trace without difficulty 

 how, after having filled the lake, the Eakaia divided into several 

 branches, running towards the present gorge, and leaving one channel 

 after the other, when they became gorged by masses of shingle. 



