NORTH UJST. GEOLOGY. 149 



is nearly of the same altitude, but appears about twice as 

 large, its abrupt face looking equally towards the land, 

 while, like the former, the opposed side shelves to the sea 

 in an angle equal to the vertical deviation. Both these 

 rocks are composed of a dark blueish grey and compact 

 basalt, and they are remarkable as being the only rocks 

 of this nature which occur on this coast, or in any part of 

 the chain of the Long Island. 



There are many large veins of trap to be seen on 

 various parts of the eastern shore of North Uist, but 

 two of the most remarkable lie exactly opposite, one 

 to each of, the rocks now described. The vein opposite 

 to the Maddy more is easily seen in a lateral section, 

 in consequence of the fall of the cliff, and offers some 

 interesting appearances. Viewed in front, its section 

 appears parallel to the beds of clay slate which it tra- 

 verses, but when seen from a lateral position it is found 

 to cross them in a curved and somewhat waving course, 

 terminating at the surface nearly at right angles to its 

 original direction, and to the general bearing of the 

 schistose strata. It is about twenty feet thick, and is 

 divided by parallel lines into two or three beds ; of which 

 one, about three feet in thickness, is amygdaloidal, con- 

 taining nodules of mesotype and of analcime. The 

 others have a tendency to split into irregular columnar 

 forms. The phenomenon of stratified trap veins is not 

 uncommon, but this and the accompanying instance are 

 the most perfect examples of this structure that I have 

 met with, since it is accompanied by marked differences 

 in the several strata. This latter example, lying opposite 

 to Maddy grisioch, is nearly straight, and has at first the 

 appearance of a bed, but it is easy to perceive that it has 

 no continuous conformity of position with the schist which 

 it accompanies. In both cases the schist is much confused 

 and distorted. 



What connexion may exist between the detached rorks 

 and these veins, either here, or in Barra and the neighbour- 



