HILL-HOUSE-WINCHBURGH. 109 



mass ; when in the latter mode of position it, in every in- 

 stance, rests upon slate-clay, which is indurated to a consi- 

 derable extent, but concerning the appearances which the 

 limestone exhibits when in contact with the traversing mass 

 of trap, the encumbered state of the surface prevents any 

 determination. The only other quarry where the stratified 

 rocks are well exposed, as regards their relations to the 

 trap, is at Hill-house ; the strata consist of slate-clay, sand- 

 stone, and limestone, and dip N. W. under the trap at 40°. 

 None of the Neptunian rocks, however, when in contact 

 with the Plutonic mass, afford altered appearances. The 

 trap which reposes upon this series of strata is a beautifully 

 columnar basalt, and becomes in some places porphyritic, 

 from containing crystals of glassy felspar. The columns are 

 regularly formed, and are arranged, in general, at right angles 

 to the plane of the bed. In the neighbourhood of Linlith- 

 gow, the limestone is quarried at several openings, but can 

 in no place be examined at its junction with the several 

 trap rocks, which are invariably found overlying it. At 

 the village of Winchburgh, there is a mass of trap which, 

 in two places, is found in immediate contact with the strata ; 

 it is in general a greenstone of the common character, 

 but in some places becomes syenitic ; and is frequently 

 globularly arranged, the concretions varying in size. Near 

 the bridge which crosses the Canal, two dykes of green- 

 stone occur, traversing the strata parallelly, and dipping 

 to the north at about 25°, being separated from each other 

 by several layers of slate-clay, which are indurated to a 

 considerable extent, and assume the characters of a slate 

 which is found in a similar situation at Lochend, near 

 Edinburgh. At the line of junction with the trap, the 

 strata exhibit wavings and other indications of violence, 

 and are crossed by an infinity of rents or joints at right 



