434 Transactions. 



westerly limit about that line, though, by sinking deeper wells still, they 

 may be found to reach much further west at greater depths. 



It is absolutely certain that water sufficient for the supply flows through 

 the shingle. A statement has been repeatedly made to me by reliable 

 persons that their wells flow much better during and after a nor'-wester. 

 Accepting these statements as true, though my observations on the Museum 

 well do not confirm it, the explanation would be that during nor' -westers 

 the rivers are high, owing to heavy rains and melting snows on the main 

 ranges to the west, and so an additional supply would be expected in the 

 underground streams formed by percolation from the river-beds, and there- 

 fore the wells would respond with an increased flow. If the observations 

 on which this conclusion is founded are satisfactory, it would tend to confirm 

 the idea that the major part of the water in the artesian area comes from 

 underground streams which reach the edge of the outcrops of the clay-beds 

 occurring on the eastern fringe of the plains in the neighbourhood of Banks 

 Peninsula. 



Tidal Wells. 



Along the shore-line the height to which water rises is affected very 

 markedly by the tide ; for example, at New Brighton, according to obser- 

 vations carried out by the author, the level reached by water standing in 

 an open pipe varied during a tide as much as 18 in. in the case of a first- 

 stratum well (depth, about 144 ft.), while a second-stratum well (depth, 

 280 ft.) was only affected to the amount of 10 in., both wells being a few 

 yards away from the high-water mark and slightly above it. The influence 

 of the tide on the wells is noticed all along the coast from north of the 

 mouth of the Waimakariri nearly to the mouth of the Rakaia, and its effect 

 is felt inland for a distance of three miles in the neighbourhood of Christ- 

 church, with a gradually diminishing amount as the distance from the 

 sea increases. It is impossible to tell the exact limits of the influence of 

 the tide, owing to local and variable causes masking it when the amount 

 is small. 



It is also noteworthy that these tidal wells are salt. Near the shore 

 the water from the first-stratum wells is so salt as to be unpleasant to drink, 

 while that from the second stratum is less salt, the amount of saltness 

 falling off with greater distance from the sea. No data are at present 

 available as to the amount of saline matter present in these wells, but this 

 will be furnished in a subsequent paper. In certain cases, too, wells sunk 

 some distance from the sea are distinctly saline immediately after being 

 sunk, but lose their salinity after an interval of a few weeks ; but this 

 does not apply to those near the shore, which are permanently salt. 



Natural tidal wells are known from other parts of the world, and I have 

 seen a reference to similar artesian wells round the shore of the Bay 

 of Tokyo, in Japan. I cannot find the article on this subject which drew 

 my attention, but, as far as-T can remember, the writer attributed the 

 variation in level in this case to the loading of the surface of the ground by 

 an additional weight of water at high tide, and cited experiments as to the 

 effect of artificial loading on the height of wells. As far as I can recollect, 

 the two cases are somew'hat parallel ; but the presence of salt water in the 

 Canterbury tidal wells suggests that these wells have access to the sea, 

 which is not explained by the theory just mentioned. 



The combined effect of the tide and the presence of salt may be explained 

 if it is understood that the water-bearing stratum has an outcrop under 



