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Conclusion.
It is hoped that the diagrams given with this paper may be of some interest and use to the general public, as they afford a certain amount of information as to the depths at which the water-bearing beds are to be found, and seeing that these records are put into such a form as to be readily understood.
The main results of this preliminary investigation of the area are to demonstrate,—
(1.) That the geological arrangement of the beds is not so irregular as was anticipated at first, but that certain probable marine beds are persistent over considerable areas.
(2.) That the water-bearing beds, being gravel, and in all probability laid down on a land-surface or by the agency of strong and varying currents, are liable to great variation in thickness and also to be split up by intercalated sandy or clay beds. This increases the number of water-bearing
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beds, and militates strongly against accurate predictions being made as to the precise depth at which water will be struck in any particular locality.
(3.) That the level of the land was gradually depressed for at least 600 ft., probably much more, while the beds were being laid down. This fact has considerable bearing on the explanation of the advance and retreat of glaciers within recent times, and also on the formation of terraces in the Canterbury District. In the face of the positive evidence for depression, the explanation of the formation of the river-terraces as a result of elevation must be taken with great reserve, and the present writer does not believe that elevation was the determining cause for their formation. The reason for the depression of the land is uncertain. It may be the result of a loading of the crust with detritus, or it may be due to some great crustal movement whose prime cause can hardly be indicated at present, considering our scanty knowledge of the changes which affect the body of the earth as a whole.
These are the main results of this inquiry up to the present, but there are several further lines of investigation which could be indicated, such as (1) the chemical properties of the water in relation to the geological conditions, (2) the various interesting hydraulic problems dependent on pressure and supply, and (3) the purely geological one of the actual order and arrangement of the various beds in their bearing on the general mode of construction of delta deposits.