110 J. T. Jutson: ''Dimpling" of Granite Hills. 



The present writer does not at present desire to discuss the 

 mode of origin further than to state that he agrees with the 

 authors just mentioned as to the commencement of the hole 

 being in some instances due to more easily eroded portions of 

 the rock surface, than other portions, and also as to the effect 

 of joints and of solution in the formation of various gnamma 

 holes. With regard, however, to the " dimples " the subject of 

 this paper, joints, so far as the. writer has observed, have had 

 little or no influence in the excavations. Solution on the other 

 hand has undoubtedly played an important part. In the case of 

 " dimples " formed along a drainage furrow on* the side of a 

 hill, the mechanical action of water, when the holes overflow 

 after heavy rain, and the water passes from one hole to another 

 by a series of low waterfalls, must, to some extent, be responsible 

 for the erosion. 



DESCRIPTION OF PLATE V., Figures 1, 2. 



Fig. 1. — A series of " dimples " in an erosion furrow on a side 

 of the granite hill. The furrow commences at the top 

 towards the right hand side, and runs to the centre of 

 the photograph. 19 Mile Rocks. 



Fig. 2. — An individual " dimple " or rock hole on a side of the 

 hill. A channel is being cut backwards towards the lip 

 of the hole owing to the overflow at the lip. The hole 

 is empty, but the height that the water reaches is clearly 

 shown on the photograph. 19 Mile Rocks. 



