256 Dr. Mac Culloch on a 



divided naturally into regular prisms, of a diameter not exceed- 

 ing two or three inches ; which, being detached, may often be 

 found on the beach. It is not possible to ascertain the extent 

 of this appearance, because the greater part of the cliff is abso- 

 lutely inaccessible. Standing alone, it is not a circumstance, 

 perhaps, to have excited much interest ; but when connected 

 with the phenomena next to be described, it forms a valuable 

 addition to a collection of facts as yet, it is true, rather too 

 limited to be of a very satisfactory nature. 



It has long been known, that a collection of columns of 

 considerable size exists at the pier of Dunbar ; and it has been 

 examined, perhaps, by every mineralogist who has resided in 

 or visited this country. This rock has been known by different 

 names, having been called a red basalt, and a columnar jasper. 

 It will presently be seen that it bears no relation to basalt, 

 being a stratified rock ; and that, instead of consisting of one 

 substance only, the prisms are formed of different minerals or 

 rocks, appointed by the common bond of juxtaposition and 

 form. The probable causes of their variety, and of their real 

 nature and origin, will be rendered sufficiently apparent when 

 their true geological connexions are described. 



The whole of this shore consists of that red sandstone 

 already mentioned as reaching from Arran across the centre of 

 Scotland. It is true that, between the two, there is no conti- 

 nuity of connexion visible ; but their relations to the subjacent 

 and superincumbent strata, and their characters, are, in all 

 essential points, the same. This sandstone is the old red sand- 

 stone of certain geologists. 



The substances of which the series consists at this place are, 

 principally, a red argillaceous sandstone, with which are inter- 

 stratified red ferriferous shales, common lead-blue shales, 

 white sandstones, and some slender laminas of an impure cal- 

 careous rock. The principal limestones lie higher up in the 

 series, which, as is well known, is followed by the coal-field of 

 this coast. 



Another circumstance respecting the general structure of this 

 country must yet be noticed, to render the geological descrip- 

 tion complete. It contains, in several places, insulated and 

 superincumbent masses of trap, together with veins of the 



