240 PROCEEDINGS OF THE COTTESWOLD CLUB 



One portion of the formation, however, has almost 

 entirely resisted attack, not from its intrinsic hardness, 

 but owing to the protection afforded by the roof 

 of erupted basah just mentioned, much in the same way 

 as a hay-rick is protected by its cover, and the Clee Hills 

 stand out proudly above the denuded country round, as 

 an example of the success of nature in preserving her 

 own handiwork from her own assaults. They are, in fact, 

 gigantic examples of the curious structures known as "Earth 

 Pillars," found in Switzerland, the Tyrol, and above all in 

 Colorado and the Rocky Mountains, where columns of 

 sandstone are seen a foot and upwards in diameter, some 

 of them more than 200 feet in height, each capped with 

 the large over-hanging slab of hard refractory material 

 which has sufficed for hundreds of centuries to pre- 

 serve it. 



The Clee Hill stone is bluish, almost black in colour, 

 hard and close-grained in structure, and composed of a 

 mixture of small crystals of hornblende and felspar. 

 Hornblende predominates and confers on the stone its 

 valuable properties of hardness and durability. This 

 excessive hardness would render the quarrying of it a 

 work of very great dilhculty, were it not for the fact that 

 owing to the conditions of temperature and pressure 

 under which solidification took place, the whole mass is 

 " jointed " and traversed by a network of more or less 

 minute cracks, like a piece of glass which has been 

 suddenly cooled, and probably in part for the same reason. 

 These cracks are often quite imperceptible at the surface, 

 but by lighting a fire against the rock the water which it 

 contains is converted into steam, which finds its way out 

 through the "joints," and forms an easily visible edging of 

 moisture along the line of the crack. The men then 

 drive in wedges, and " prize " off large blocks which are 

 afterwards cleft with sledge-hammers. Much work is 

 also done by blasting, but as no steel drill can make much 



