286 PROCEEDINGS OF THE COTTESWOLD CLUB 



for roads must necessarily be subject under varying 

 atmospheric conditions ; although of course, other things 

 being equal, the "crushing test" would determine the great 

 superiority of the stone. 



The ordinary weight of normal traffic upon roads may 

 be taken at i)^ tons upon a pair of wheels, or only ^ ton 

 per wheel. 



Now Kirkaldy establishes by scientific and therefore 

 accurate tests that before a 3 inch cube of Dhu Stone 

 cracked only slightly, it bore the enormous pressure 

 equivalent to 1340 tons per square foot, and only crushed 

 under a pressure of 1673 ^ons ! One of three specimens 

 failed only at 1808 tons per square foot crushing weight. 

 If we consider by the light of these facts that the heaviest 

 weight which can be brought upon a roadway is that 

 represented by a steam roller of say sixteen tons on four 

 wheels, or four tons per wheel, and remember the distribu- 

 tion of this load caused by the width of the broad tyres, 

 it will be seen that the power of the Clee Hill stone to 

 resist fracture is so pre-eminently great that the feather 

 weight of four tons per wheel is out of all proportion to 

 the ultimate strength of the stone. Nevertheless, it may 

 be of some interest to compare the Dhu Stone with other 

 hard stones, so as better to realise what the above tests 

 mean. 



lbs. per sq. in. 



Clee Hill Basalt - - - will crush at 28,122 



Penmaenmawr „ 26,837 



Whinstone (Northumberland) ,, 25,702 



Bardon Hill „ 20,742 



Llanbedrog (Carnarvon) - - „ 20,711 



Threlkeld (Cumberland) - - „ 20,128 



xMarkfield - „ 19,096 



Mount Sorrel „ 17,388 



Dalbeattie (Kirkcudbright) - „ 14,071 



Cornish Granite - . - . ,, 14,000 



