J. D. ENYS ON SAND-WORN STONES EKOM NEW ZEALAND. 87 



wearing away of the stones on this flat ground. Originally of the 

 ordinary shape of broken stone, they begin by showing sloping sides, 

 as in fig. 1; and as the process goes on, the two sides gradually come 

 together, and finally assume the shape of a triangle, as in fig. 2, 

 with even angles and slightly convex sides, with rounded edges at 

 the base. 



Should the long axis of the stone lie in the line of the prevailing 

 wind, the two sides of the stone are worn away to an even angle (fig. 

 2); but should the longer axis be slightly inclined to, or against the 

 prevailing winds, I find that one side is much more quickly worn 

 away than the other ; and the stone then presents a triangular section 

 with the one side longer than the other. 



Amongst these stones I have found some with veins running through 

 them of a harder material ; and the result has been that the Eolian 

 action has proceeded unevenly, leaving these veins standing above the 

 softer matrix, but rounded like the veins in a man's hand (see the 

 left side of fig. 2) ; indeed, when the veins were parallel to the base 

 of the stone, the Eolian action has even undercut these veins. 



A short time since, Mr. Stow, of Wellington, exhibited to the 

 Wellington Philosophical Institute pieces of drift-pumice cut in a 

 similar manner ; these I had the pleasure of seeing at the time. 

 These specimens came from the mouth of the river Waikat. 



Many of the stones were brought to the neighbourhood by the 

 natives to use in their cooking-places. These stones they first heat 

 and then pour water on, which causes them to fracture in a con- 

 choidal manner. These fragments I have seen in all states of manu- 

 facture by Eolian action. 



These interesting stones were first noticed in 1869 by Mr. Hack- 

 worth ; and a paper on them was read by Mr. W. T. Travers before 

 the Wellington Society, Feb. 9th, 1869, which has been published in 

 vol. ii. p. 246 of the ' Transactions of the New-Zealand Institute/ 

 together with a plate. 



Indeed it is only acting on the advice of friends to whom I have 

 shown these specimens, that I have ventured to bring this paper 

 before the Geological Society, that this curious instance of Eolian 

 action may obtain a wider circulation than it has at present in the 

 ' Transactions of the New-Zealand Institute.' The earlier numbers 

 of that valuable work are, indeed, difficult to obtain. 



Discussion. 



Prof. Eamsat agreed with the author in his explanation of the 

 mode of shaping of the stones. He remarked that in England there 

 are numerous examples of Eolian action, which also occur in Egypt 

 on a very large scale, level strata being in the latter country marked 

 with grooves deeply ploughed by blown sand. As an English 

 example he instanced the singular crags on the top of Kinder Scout. 

 This forms part of a great tableland in Lower Carboniferous rocks ; 

 and upon it are club-shaped and mushroom-like pillars of sandstone, 

 the formation of which has often been ascribed, wrongly in Prof. 



