in the Neighbourhood of Edinburgh. 43 



this movement, a considerable fault or dislocation was occasioned 

 towards the centre of the section, by which they became bent 

 and distorted in the manner now seen, — their eastern portions 

 having been thrown up, whilst their western portions were cast 

 down, so as to lie unconformably upon the upturned strata. Near 

 the point of junction of these rocks with the trap, the effects of 

 subsidence are very evident, the shattered extremities of the 

 strata having apparently fallen over, being at the same time forced 

 into a more southerly direction, by which they seem to have been 

 brought obliquely into contact with the tabular masses of green- 

 stone, against which they appear to have been precipitated, and 

 upon which the inverted fragments of sandstone, with interven- 

 ing portions of slate-clay or marl, are now seen to rest. 



If the trap had been in a soft state from fusion at the time, 

 some intermixture of the igneous fluid with the stratified rocks 

 must have taken place during this collision ; but no imbedded 

 fragments are to be met with, nor any veins passing from the one 

 into the other ; neither are there any marks or impressions visible 

 on the smooth surface of the greenstone, except some slight su- 

 perficial scratches, such as might have been caused by abrasion 

 during the simultaneous passage upwards of these two descrip- 

 tions of rocks, if both had been consolidated previous to their 

 elevation. The fragments, however, imbedded in the upper part 

 of the rock, as well as the altered nature of some of the contigu- 

 ous strata, shew that, at some period, this rock must have been in 

 a state of fusion, and capable, by its intense heat, of affecting, in 

 this manner, the stratified rocks in its vicinity. 



Although at first sight it might appear difficult to reconcile 

 these opposite and apparently contradictory facts, if we can ad- 

 mit that the stratified rocks had been deposited in seas or lakes, 

 and that the trap had also a subaqueous origin, it must follow 

 that the dry land which they now form, must, at some time or 

 other, have been elevated above the waters, when, in all probabi- 

 lity, a considerable modification of their relations with each other 



f 2 



