Northumberland and Durham. 91 



These strata appear to alternate to a great depth ; they lie nearly 

 horizontally, and seem to run through the whole extent of the hill. 

 The stratification in the west side of the hill is nearly the same as 

 the above, but in the upper stratum of slate-clay nodules of reddish 

 gypsum are intermixed, and in the lower gypsum is disposed in thin 

 irregular strata of amorphous fracture. 



The nodules of gypsum contain numerous dark reddish brown 

 crystals of selenite. Similar nodules are also found in the hillock 

 on which Kelso is built, imbedded in blue shale. The marl of 

 Roxburghshire, when dry, is of a dirty blueish white colour, con- 

 taining small bivalve shells. 



In Mellendean burn the strata, particularly on the eastern side, 

 are exposed to the depth of 60 or 70 feet, and consist of 



1. Gravelly soil, 



2. Marl, 



3. Blue and brown slate-clay, alternating with limestone, 



which contains a large proportion of sand. 



Two hundred yards further up the burn, the strata in its bottom 

 consist of very hard bastard limestone, that is, limestone containing 

 a large proportion of sand. The beds lie horizontally. The upper- 

 most stratum in the bank near the entrance of the Dean is composed 

 of amygdaloid. Wacke, and amygdaloid with a basis of wacke are 

 not uncommon in the valley of the Tweed, where they appear to 

 occur between beds of sandstone, as may be seen at Sprouston 

 Ferry, at the Rapids about 3 miles above Kelso, and at a fall of the 

 river Tiviot about a mile above the same town. 



The covering of Sprouston quarry is of the same kind of sandy 

 and gravelly soil, as generally covers the vale of the Tweed. The 

 sandstone rock of the quarry appears to be of limited extent, and of 

 an irregular oval form, being about 300 yards long and 200 yards 



m2 



