72 GEOLOGY OF THE LOTHIANS. 



ance and its present outline ; what then formed one moun- 

 tain, may now be broken down into several, and the once 

 perfect continuity of a bed of basalt or greenstone over 

 one mountain, may now only be inferred by finding it 

 forming mountain caps to portions of that mountain. * 



In addition to the different points which we have describ- 

 ed, where the relations of the various rocks to each other 

 are observable, there are others ; but few of these exhibit any 

 thing remarkable. In the bed of the river Almond, at the 

 Aqueduct Bridge, the slate and sandstone are associated with 

 a greenstone, which forms, for a considerable length, the en- 

 tire bed of the river ; it is surmounted by an assemblage of 

 shale strata, and in all probability forms a great vein which 

 runs parallel with their direction. On the north side of the 

 bridge these strata are found under a second bed of trap, 

 which can be traced for several hundred yards : the slates, 

 when in contact with the greenstone, are slightly indurated, 

 and the trap as it approaches them, becomes gradually more 

 compact. A short way up the river a vein of trap about 

 four feet broad traverses the sandstone, and near this an- 

 other is to be seen running parallel with the strata, which 

 dip at about 30°, pursuing a determined course for many 

 yards ; it cannot be traced throughout its whole extent, but 

 may be examined in the bed of the river, and also in seve- 

 ral parts of the cliffs. Near Almondell the strata present, 

 within a very short space, several examples of undulation, 

 and are traversed by a vein of greenstone, having a thick- 

 ness of three feet. In the limestone quarries of East Cal- 

 der there are several interesting phenomena attending the 

 relation of the limestone to the greenstone, which is of 



* In the island of Rum there are several good examples of mountains 

 being formed by the decomposition of one. The large granular augitic 

 greenstone ridges of Haleval are only continuations of Aisgobhall, though 

 now both of these mountains are separated by a deep glen. 



