476 



(1.) The greywacke strata form the summit of Cockburn-Law, 

 having a strike about NE. and SW. nearly vertical. There appears 

 to be no decided evidence of any organic remains in these strata ; — 

 there are curious markings which are most probably only concretion- 

 ary. At Hoardwheel, situated to the eastward of Cockburn-Law, 

 two varieties of copper ore are found in the greywacke, the green 

 and the grey, the former of which is the most plentiful, and imparts 

 a beautiful hue to the rocks. The oxide of manganese is also widely 

 diffused. 



(2.) The old red sandstone strata lie over the upturned edges of 

 the greywacke, and have therefore been deposited at a more recent 

 epoch. At a distance from the hills they are generally horizontal, 

 or dip away at a gentle angle ; — but at the sides of the hills they 

 are hidily inclined, — a circumstance probably caused by an upheaval 

 of the hills, which took place after the date of this formation. These 

 old red sandstones are extensively developed in Preston Haugh. The 

 lowest bed consists of pebbles or fragments of rocks, both angular 

 and rounded, derived from the wearing down of the greywacke and 

 poi'phyritic rocks. The colour of this formation is, especially towards 

 its base, of a red colour. 



It is in this formation, that the bones, teeth, scales, and spines of 

 the Holoptichius nobilissimus, a large ganoid fish, described by 

 Agassiz, were found by the author in 1840. These are remains of 

 the same kind of fish which have been found in Perthshire, England, 

 Russia, and in other parts of the globe, and which abounded at the 

 epoch of the old red sandstone formation ; for wherever it is found, 

 these particular rocks prevail. The nature of the strata in which it 

 is found — a coarse, gritty sandstone — seems to indicate that the 

 Holoptichius swam about in waters near the shore ; another proof of 

 which is afforded by the ripple marks on the sandstone slabs near 

 their place of sepulture. These interesting relics are vei'y abundant 

 in the strata opposite to Cockburn Mill, and also about half a mile 

 below it, on the right bank of the Whitadder. 



(3.) The coal-measure strata lie above the old red sandstone 

 rocks, but are not disconformable to them in dip. They are to be 

 seen in the Whitadder, below Preston Bridge, and consist of the 

 ordinary sandstones, shales, and strata of ironstone. The only 

 fossils prevailing in them are those of terrestrial vegetables, which 

 probably had been drifted by rivers. 



II. The Igneous rocks were divided by the author into two classes 

 —one of which he described as the Felspathic, the other as the 

 Augitic. 



