DISTRIBUTION OF THE ROCKS OF THE LOTHIANS. 110 



eminences which are composed of this series approaching 

 more or less to the conical shape ; there are felspar moun- 

 tains, however, having the round- backed form, but gene- 

 rally, it may be stated that they present an outline more 

 or less acute. The trap series also affords those well 

 marked characters of form, which have from their almost 

 universal occurrence, awarded this descriptive title to the 

 group. Large extended and more or less parallel ridges of 

 dark-grey rock, having a face in general approaching to 

 vertical, often perfectly or rudely columnar, and separated 

 from each other by a slope covered with debris or vegetable 

 soil, constitute the general aspect of a trap hill. In the trap 

 valleys, also, there is a system of characteristic forms : they 

 are most frequently of inconsiderable dimensions, and ap- 

 pear, in the generality of cases, to present no indica- 

 tions of any formation but one synchronous with that of 

 the trap deposit in which they form depressions. They 

 are almost always irregular in their levels, and not sufficient- 

 ly extensive to be traversed by any bodies of water, which 

 in size deserve to be raised to a higher rank than that of 

 streams or rivulets, and it is from this circumstance that 

 the lower parts of the trap valleys are frequently more or 

 less in a marshy state. 



Concerning the topographical distribution of the several 

 formations which constitute the Lothians, the highly covered 

 state of the country prevents us from being able to assign 

 to each minute lines of boundary. The bounding line of 

 the transition strata with the secondary deposits which skirt 

 them, is somewhat irregular : it may be stated, however, that 

 in Haddingtonshire, no rocks of this group occur to the 

 east of a line running; almost north and south through 

 Crichness, Kist Hill, Dod, Watchlaw, and East Heartside ; 

 a little to the north of this, the line assumes, at the farm of 



