238 GEOGNOSY OF EAST LOTHIAN. 



in size from a quarter of an inch to upwards of two 

 inches in diameter. Sometimes the sandstone has 

 a conglomerated aspect, appearing, at first sight, as 

 if composed of fragments of sandstone, contained in 

 a sandstone basis ; but a careful examination proves 

 that this curious variety of rock is not brecciated ; 

 on the contrary, the fragments are cotemporaneous 

 portions of sandstone, of a harder or softer nature 

 than the basis in which they are included. 



These cotemporaneous masses vary in shape and 

 size, being spherical, oval, blunt-angular, sharp-an- 

 gular, and tuberose ; and are from an inch to seve- 

 ral yards in length and breadth. It is particularly 

 interesting to observe the laminae of the slaty va- 

 rieties of sandstone terminating in the sides of the 

 massive cotemporaneous varieties. Fig. 1. and 2. of 

 PL xii. represent laminae of slaty-sandstone termi- 

 nating on massive and hard sandstone. Viewing the 

 sandstone as a chemical formation, this appearance 

 shews how the slaty, and consequently the stratified 

 structures, may be frequently unaffected by the rock 

 they surround. V eins of sandstone occasionally oc- 

 cur, traversing all the varieties of that rock. They 

 terminate in the rock, and are intermixed with it at 

 the line of junction ; hence are of cotemporaneous 

 formation with it. The strata vary in thickness 

 from a foot to several yards, and have the general 

 dip and direction of the rocks already described. 

 The individual strata often exhibit great variety in 

 structure, being waved, disposed in zig-zag lines, 



