NOTES ON THE CLEVELAND DYKE, 



BY 



lar. Y. YE ITCH, 



President of the Cleveland Naturalists' Field Club. 



The most interesting physiographical feature of this district is 

 the Cleveland Whin dyke, and consequently it has attracted con- 

 siderable attention. Having been carefully examined, several 

 able papers have been written concerning it, and it is no doubt a 

 well worn subject. My aim will be to gather together scattered 

 facts, and the results of the latest investigations relating to the dyke. 



Whinstone is a word loosely used in many parts of England; the 

 porphyrite of the Cheviots is spoken of as whinstone ; the hard 

 sandstone of the Lower Greensand of west Sussex is also so called, 

 any hard sandstone seems to be known as white or grey whin. 



The term whin is here applied to an igneous rock, pertaining in 

 character to a basalt, which has come up through the intermediate 

 stratification in a molten state, forming a wall traversing the country 

 from Maybecks on Sneaton high moor, near Whitby, and about four 

 miles from the sea, to Armathwaite in Cumberland. 



On petrological grounds Mr. Teall says the Armathwaite dyke is 

 a continuation of the Cleveland dyke, it points to the north west 

 direction where great volcanic eruptions took place in tertiary times, 

 generally ascribed to the miocene age. The earlier lava thrown out 

 by those eruptions was acidic, and the composition of the dyke 

 pertains more to acidic than basic, and is most probably the result 

 of the western disturbances mentioned. 



