IV. — On the Stnicture and Relations of the Deposits contained between 

 the Frimary Rocks and the Oolitic Series in the North of Scotland. 



By the Rev. ADAM SEDGWICK, V.P.G.S. F.R.S. 



(WOODWARDIAN PROFESSOR IN THE UNIVERSITY OF CAMBRIDGE, &C.) 



And RODERICK JMPEY MURCHISON, Esq., Sec. G.S. F.R.S. F.L.S. &c. 



[Read May 16th, and June 6th, 1828.] 



§ 1. Introduction. 



Although no good geological map of Scotland has yet been published, 

 enough is known of its general structure to enable us to state, that nearly all 

 the interior portions of the Highlands are composed of primary rocks gene- 

 rally exhibiting a slaty texture ; and that, on the north-eastern and north- 

 western coasts, as well as on the southern flank of the Grampian chain, these 

 primary rocks are succeeded by enormous masses of red sandstone and con- 

 glomerate, which, in several places (already described by one of the authors of 

 this paper), are surmounted by a system of beds referrible to the lias and oolitic 

 series of England. Our object in this communication is to describe the lower 

 portion of these secondary deposits, viz. the masses of red sandstone and 

 conglomerate ; — to consider the natural groups into which they may be sepa- 

 rated, — and, as far as possible, to bring them (as we have already done in de- 

 scribing the carboniferous series of the Isle of Arran) into comparison with 

 formations of the same age in the southern parts of our island. The accom- 

 panying outline map*, partly constructed from our own observations, and partly 

 derived from the works of M'^CuUoch, M. Boue, and other writers on the 

 geology of Scotland, will convey a general notion of the geographical distri- 

 bution of the masses we are about to describe. A glance of the eye over the 

 map might induce us to suspect that tliey all belonged to one epoch, and even 

 a slight examination of them would confirm tlie conclusion ; for the conglo- 

 merates on the south-east flank of the Grampians are perfectly identical with 

 those at the base of the secondary deposits of the Murray Firth and Caithness : 

 and these, as will be hereafter shown, are strictly analogous to the conglome- 



* See Plate XIII. 



