146 Mr. Prestwich on the Structure of 



England), I conceive, that it belongs to the carboniferous series, and most 

 probably, to be the representative of the millstone grit or mountain limestone ; 

 and, therefore, to be younger than the Caithness schists*. 



APPENDIX. 



[Read May 3, 1837.] 



In the preceding memoir, as read before the Society in April 1835, I stated, 

 that Has fossils had been found in outliers of dark blue clay and sand, which 

 in several places overlaid the older rocks, and upon that evidence, I suggested 

 the beds might be of the age of the English lias. I had not then carefully 

 inspected those deposits, and in the cursory examination which I made, I met 

 with no fossils. Subsequent researches, however, having led me to doubt the 

 correctness of my former surmise, and having again visited the district last 

 summer, 1 now beg to retract that opinion, and to state briefly the conclusions 

 at which I have arrived. It is true, that lias fossils are occasionally found in 

 the cliffs of Blackpots, and in the beds of clay in other places around Banff; 

 but they always occur in separate, rounded nodules and fragments of shale and 

 limestone, associated with pebbles of the schistose rocks, and are disseminated 

 in layers and patches in a dark, tough, or slightly micaceous clay. This ar- 

 gillaceous deposit, forms at Blackpots, cliffs eighty feet high, and rests upon 

 sand which is rarely exposed ; a bed of gravel usually intervening between the 

 clay and sand. 



The stratification of this accumulation is nearly horizontal, but irregular. Above McDufF it caps 

 the hill to a considerable thickness, its lowest bed being grey loam, twenty feet thick, full of angu- 

 lar fragments of slate rocks. Patches of it range eastward by Melrose to Gamrie, and thence by 

 Crovie to the back of Troup ; but it is at Castle Hill, Gamrie, that the deposit is best developed. 

 (Plate X. No. 4.) This hill is about 250 feet high, of a roughly conical form, and is exposed on one 

 side by the cliff, and on two other sides by deep ravines. The base of the hill, to the height of about 

 80 or 100 feet, consists of old red sandstone, upon which reposes a series of sands and clays, and 

 on the summit are the remains of a small vitrified fort. A few fragments of shells scattered on the 

 grass about half way up the hill, induced me to make an excavation, by which I succeeded in ob- 

 taining several well-preserved specimens ; and though the shells were rather numerous, they were 



* Mr. G. Anderson of Inverness has recently informed me that Ichthyolites, the same as those 

 of Gamrie, have been found by Mr. Miller near Cromarty, in a bed of clay, overlying the great 

 system of conglomerates and sandstones 



