J. W. JUDD ON THE SECONDARY ROCKS OP SCOTLAND. 681 



escaped removal by denuding forces up to so reeent a period as the 

 Glacial epoch, yet we have at the present time no certain evidence of the 

 existence in situ of any deposits of that age in the Eastern Highlands. 

 In the "Western Highlands, however, I have been so fortunate as to 

 detect such evidences ; and they enable us to arrive at a number of 

 conclusions concerning the physical conditions prevailing in the area 

 in question during the Cretaceous period that are of the most striking 

 significance and the highest interest at the present time. 



In the west of Scotland, as in the north of Ireland, the lowest 

 Cretaceous strata exposed are of Cenomanian (Upper Greensand) age, 

 and, as in the latter district, they are of marine origin. Above these 

 marine beds, however, there occurs a series of sandstones containing 

 thin coal-seams and other evidences of the prevalence of estuarine 

 conditions ; and these are in turn covered by a singular marine re- 

 presentative of the highest beds, of the English Chalk — the Zone of 

 Belemnitella mucronata. Finally, the second series of marine beds 

 is seen in places to be covered by other estuarine and coal-bearing 

 strata, which may represent the highest members of the Cretaceous 

 (the Maestricht, Faxoe, and Meudon beds), or may be intermediate in 

 age between the Cretaceous and Tertiary, or, lastly, may constitute 

 the base of the great Tertiary series of rocks in the Highlands. 



This remarkable series of alternating marine and estuarine strata of 

 Upper Cretaceous age — so different in character from the deep-sea re- 

 presentatives of the same formations in the other parts of our islands — 

 is unfortunately only very imperfectly seen at a few not very accessible 

 points ; and they moreover make their appearance in such a manner 

 from beneath the vast and overwhelming masses of Miocene basalts 

 as to afford but scanty facilities for their study and for the collec- 

 tion of their fossils ; but the fact of the existence of such beds in the 

 extreme north-western part of our archipelago, especially in face of 

 the great development of estuarine Cretaceous strata on the North- 

 American continent, is one of the very highest interest. JNor is 

 that interest lessened by the fact that we find in the same area 

 proof of the presence of a Cretaceous shore-line in the beds of coarse 

 conglomerate into which the strata in question are sometimes found 

 to graduate. 



The Poikilitic strata of the Western Highlands, though not yet 

 proved to be fossiliferous, like their representatives in the east (the 

 reptiliferous sandstones of Elgin, &c), are by no means destitute of 

 interest ; and the circumstance that while, on the one hand, they 

 can be shown to be distinctly superposed on rocks containing un- 

 doubted Carboniferous plants, on the other they are conformably 

 overlain by Infraliassic strata, is of the highest importance in its 

 bearing on the long and vexed controversy concerning the age of the 

 equivalent strata in the Eastern Highlands. 



Although the different members of the Mesozoic formations in the 

 "Western Isles exhibit, as is so frequently the case with strata of lit- 

 toral and estuarine origin, very numerous and rapid changes in 

 thickness and character within comparatively short distances, yet 

 when all the evidence is pieced together by the aid of the palaaonto- 



