Vol. III. MAY, 1894. No. 5. 



DYKES IN ANTRIM AND DOWN. 



BY MARY K. ANDREWS. 



The study of every portion of the earth's crust is instructive, 

 but the margin of our coast-lines is specially invested with 

 the most varied and peculiar interest. Here we seem to gain 

 a fuller insight into the architecture, so to speak, of the earth ; 

 the sea, aided by the various sub-aerial denuding agents, rain, 

 frost, wind, &c, constantly wearing down and wearing back 

 the coast-lines, as constantly bringing fresh surfaces to light. 

 Independently of this ceaseless change, there is another 

 reason why this belt of the lithosphere should claim our 

 attention and excite our interest. It is here that we find 

 some of the grandest displays of volcanic action. If we take 

 the borders of the Pacific on the one side, from Cape Horn to 

 the Aleutian Islands, on the other from Kamtschatka to 

 Victoria Land, we find it encircled by volcanic cones, the 

 greatest energy, at the present day, centring around the 

 Sunda Strait. The detonations of Krakatoa in August, 1883, 

 are still fresh in our memories. 



Traversing the Atlantic Ocean from Greenland to Tristan 

 d'Acunha, we have a more interrupted series of volcanic 

 mountains ; many are apparently extinct, but we find active 

 vents in Iceland, in the Azores, in the Canaries and in other 

 islands. In this sinuous band, the volcanic rocks of the North- 

 East of Ireland may be included ; its sheets of basalt and 

 characteristic dykes remain witnesses to the igneous energy of 

 the Tertiary Period. 



Fringing this basaltic plateau, we have very interesting 

 groups of dykes, a few, such as those at the Cave Hill, being 

 exposed at considerable elevations. Several series are well 

 seen on either side of Belfast Lough at low water. Those 

 between Lower Whitehouse and Whiteabbey are particularly 



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