MR MILNE ON THE MID-LOTHIAN AND EAST-LOTHIAN COAL-FIELDS. 273 



just stated. On the other hand, where the dip and direction of the strata pre- 

 sent considerable deflections, the shps cease to be parallel. For example, at the 

 Roman Camp, where the same individual strata wind round the hill, having al- 

 most a quaquaversal dip, the slips present a similar deflection, and converge to- 

 wards the top of the hill. 



(5.) I may add, in reference to the slips, that they vary materially in width. 

 In some of them the sides of the slip are in contact with each other ; and in these 

 cases, I am informed, scratches or ruts are occasionally visible on the sides. The 

 late Mr Grieve mentioned to me one remarkable instance of this he had seen in 

 the great ninety fathom slip of Sherififhall. The scratches, he said, were neither 

 vertical nor horizontal, but formed an angle with the horizon of 30° or 50°, and 

 dipped towards the south-east. 



In other cases, however, the sides of the slip are a few inches or a few feet 

 apart. The table notices several where they are nine feet apart. The chasm is 

 generally fiUed with the debris of the adjoining strata. 



(6.) Sometimes the strata are found to be cast up as well as cast down on 

 the same side of a slip. This arises from the individual strata having been 

 tilted up at their opposite ends after being fractured, so that they, as it were, 

 intersect each other at some intermediate point. An example of this occurs at 

 Stobsgreen. 



Another singular effect of a slip occurs at Prestongrange, where there is a 

 cast-down of a few fathoms at the west end of a slip, on the north side. This 

 cast-down lessens, however, towards the east, so that the coal-seam at last comes 

 up to the level of the same coal on the other side. But a little farther east, the 

 cast-down again increases. The explanation is, that, on the north side, the strata 

 dip from the common point of contact towards the east and west, more rapidly 

 on the north side of the slip than on the south. 



(7.) Another circumstance deserving notice is, that the coal and other strata 

 intersected by slips are much shattered This prevails sometimes to a distance 

 of many yards from the slip. But it has been often observed, that this condi- 

 tion of things exists only on one side of a slip, not on both sides. 



(8.) Very frequently, the strata near the side of a slip, rise suddenly up to- 

 wards it : — and it is important to remark, that this is always the case (so far as 

 I can learn) on that side of the slip where the fractured edges of the intersected 

 strata are lowest. The great slip of Sheriflfhall affords an example of this. 



(9.) It would appear from the table, that the amount of dislocation produced 

 by slips increases towards the centre of the basin or dip of the strata, much more 

 frequently than towards the edge of the basin, or out-crop of the strata. The 

 proportion shewn by the table is as two to one. 



Besides these points, there are many others of great importance, — such as, 

 whether the strata are always most shattered on the up-cast or the down-cast 



VOL. XIV. PART I. M m 



