554 Transactions. — Geology. 



present in this water in proportions greater than are here 

 stated, I consider this water is well adapted for use in the 

 boilers of engines generally." 



Note by Sik J. Hector. 



The artesian wells described by the author are certainly 

 the most powerful and copious which have yet been discovered 

 in New Zealand. The examination of the samples of strata 

 passed through and the details of the various borings prove 

 that the formation pierced is the ancient river-bed deposit of 

 the present Manawatu. The old valley of this river system 

 must be very deep, and it has been filled up by successive 

 layers of material carried forward by the river at a time when 

 the land was at a considerably higher level above the sea than 

 at present. These layers of gravel, sand, and clay were 

 deposited at steeper angles than the present slope of the sur- 

 face. x\s shown in Section C, Ashurst, at the lower end of 

 the Manawatu Gorge, is eleven miles from Longburn, and is 

 238 ft. above the sea ; Palmerston is 103 ft. and Longburn 

 62 ft. above the sea. The general slope of the surface is 

 therefore about 16 ft. per mile. The information obtained by 

 the borings that have been made, and from the inspection of 

 sections along the river-terraces, indicates that the layers of 

 river-deposit dip to seaward at 30 ft. to the mile. AH the 

 absorbent beds in this ancient river-course must be saturated 

 with soakage water from the higher levels, and when the non- 

 absorbent tough layer that seals down a water-carrying bed is 

 pierced by the pipe the water will rise to a height propor- 

 tionate to the altitude of the outcrop of that layer further up 

 the river. 



At this point water absorbed into the porous strata near 

 the junction of the Porangahau and Manawatu at Ashurst 

 will, according to the foregoing estimates, be reached at a 

 depth of 380 ft. above Longburn, but, as the diiJerence of 

 surface-level between the two places is 176 ft., when the water 

 springs to the surface through the artesian-well pipe it must 

 have a very considerable head of pressure notwithstanding 

 that the percolation is through yielding material. 



EXPLANATION OF PLATE LII. 



Pig. 1. Sketch-plan : Longburn to Manawatu River. 



Fig. 2. Rough section of same. 



Fig. 3. Section from Longburn to Ashurst. 



