Speight. — Geological Featvrei< of Chri>itchnrch Artes^ian Area. 429 



stand give a fair idea of tlie thinning-out and thickening of the same bed in 

 different parts of the district. Below the belt where gravel predominates 

 there is a set of beds composed of finer detrital matter, which would pro- 

 bably be continuous if the records of more deep wells were available. It 

 will be noted also that there are very regular and widely distributed peat- 

 beds, especially in the Fendalton and St. Albans area. 



The series shows that there was a general struggle for existence between 

 the land and the sea. The periods when the former got the best of it are in- 

 dicated by the presence of peat, and perhaps by the gravel-beds, and the time 

 when the sea stretched over the area is indicated by the finer-textured 

 beds with their occasional shell-remains. The amount of rise in the wells 

 increases, as a rule, on approaching the coast-line, and this may be put 

 down to the better textural conditions near the coast. Instead of the 

 water being distributed throughout the thick beds of shingle it is concen- 

 trated by the impervious beds into narrower bands, and so gives higher 

 and stronger flows. 



Series No. 4. — Sydenham, Opawa, Heathcote to Estuary. 

 (Plate XII.) 



This series shows the structure of the belt of country which fringes the 

 foot of the Port Hills and extends across the estuary towards New Brighton. 

 The wells of special interest are those close to the hills, in whose records 

 there is frequent mention of the presence of angular matter of volcanic 

 origin. It is probable that the water supplying them comes from rain 

 which falls on the Port Hills, and not from that on the plains, but more 

 detailed work will have to be done before this statement can be maintained 

 for certain. There is no doubt that the rocks of the hills exert a disturbing 

 influence, since some wells which are sunk in their vicinity to beds of shingle 

 yield no water, though a little distance further away similar beds at equal 

 depths are prolific. These beds must be cut off in some way from the main 

 artesian area. Others of them are down very close indeed to the under- 

 lying beds of volcanic rock, especially those near the present estuary, a fact 

 emphasized by the record of the wells sunk by the Sumner Borough Council 

 in their efforts to obtain water for the reservoir which supplies the borough. 

 The ignorance of artesian conditions, as well as the unnecessary expenditure 

 of the pubUc money resulting therefrom, is thoroughly exemplified in con- 

 nection with one well in the estuary near the Fisherman's Flat. After 

 getting a poor flow of water at a depth of 416 ft., the boring was continued 

 41 ft. further, through layers of scoria and hard black basalt, evidently an 

 outlying part of the rocks of the Lyttelton volcano, in expectation of getting 

 a more plentiful supply. Needless to say, this hope was not reahzed. 



The iecords of the wells near the estuary show that beds containing 

 shells are met with very persistently, and it may be inferred therefrom 

 that the conditions on the north side of that part of Banks Peninsula have 

 not altered materially since the beds were first laid down — i.e., the area has 

 been aestuarine for a very long time. 



This series contains the record of two very deep wells : the first sunk 

 to a depth of 708 ft., near the old Heathcote Racecourse, in order to obtain, 

 if possible, a supply for the Lyttelton Waterworks — an unrealized expec- 

 tation ; and, secondly, the well sunk at the Sydenham Water-tov/er, which 

 reached a depth of 572 ft., and gave a flow of water from a depth of 550 ft., 

 which rose 32 1 ft., and was described by the well-sinker (Mr. J. W. Home) 

 as the largest flow he ever got. I believe that this is the deepest flowing 



