82 



called), due to hard particles or pebbles in the rock, 

 that break the force of the blast and preserve small 

 portions behind each the latter tailing off from the 

 pebbles. Similar wind markings have been observed 

 on the sides of cuttings in peat, sand, and even 

 boulder-clay drift, but in the latter it cannot be as 

 regular, or well marked, on account of the varied 

 nature of the materials forming the mass ;' but, in 

 most of these cases, the wind action may be assisted 

 by the pelting of rain drops. Even in the older 

 rocks of a much harder nature, conspicuous wind 

 work has been noted, such as in the slates on the west 

 coast of Cork and Kerry, where the cleavage planes 

 are opened, and the smooth surfaces transformed into 

 a system of knife-edges. Here, however, the wind 

 is aided by water and heat, the latter opening the 

 cleavage planes through which the water is driven by 

 the wind. The sea, also, must aid the work, as this 

 peculiar weathering was only observed in rocks 

 within reach of its spray. 



Travellers in tropical regions have remarked the 

 weathering out of the joints and cracks in the rocks, 

 by which are carved out fantastic pillar-like masses, 

 or piles like massive cyclopean masonry. This 

 weathering appears nearly solely due to the combined 

 action of heat and wind, aided in some cases by rain ; 

 the first opening out the joints and gradually dis- 

 integrating the adjoining portions of the rocks, 



