146 Rev. A. Sedgwick and Mr. Murchison on Deposits contained between 



The first appearance of the oldest conglomerates in the course of the Alt- 

 Grant^ is at Meul Tiirach, about a mile below Loch Glass, where it forms a 

 bold pyramidal mass, which rises more than a thousand feet above the level 

 of the river. It rests unconformably on gneiss, and is almost entirely com- 

 posed of large and imperfectly rounded fragments of that rock, with a small 

 proportion of red-coloured cement. This mountain mass is, in its general cha- 

 racter and relations, perfectly identical with the lowest conglomerates of the 

 chain of the Maiden Paps, and is prolonged towards the north and the south 

 in the form of an irregular, broken chain of pyramidal hills, resting upon, or 

 abutting against, the primary mountains. The phaenomena at the points of 

 junction, and the true relations of this immense deposit, may be studied in 

 many parts of the range already pointed out*. Below Meul Turach, the 

 banks of the river are for some distance occupied by morass, but it afterwards 

 makes its way through narrow gorges of the conglomerate ; and, after many 

 devious windings, pierces through the solid rock, and falls at a single plunge 

 into a lower part of the valley. 



As the whole system dips at a considerable angle towards the Cromarty 

 Firth, we must obviously, in descending the transverse valleys, reach in suc- 

 cession the newer portions of the conglomerate series. Continuing then to 

 descend by the banks of the Alt-Grant, we meet with great masses of conglo- 

 merate associated with sandstone or flagstone resembling grauwacke. These 

 are succeeded by great alluvial terraces, which are chiefly composed of white in- 

 coherent sand, and which, for some distance, entirely cover the regular strata. 



About a quarter of a mile above a deep gorge which enters a second zone 

 of conglomerate mountains, there appears on the banks of the river a succes- 

 sion of beds composed of calcareo-bituminous schist, calciferous grit, and flag- 

 stone of a red or greenish red colour, and which cannot be mineralogically 

 distinguished from many of the lower beds associated with the bituminous 

 schists of Caithness. These beds alternate with many masses of sandstone 

 and cono-lo.nerate; and they enter essentially into the composition of a re- 

 markable system of deposits which are interposed between the first and second 

 ridge of conglomerate mountains. They appear in the Alness nearly in the 

 same form, but more mixed with red and greenish red marls. In the hills 

 near Tulloch Castle, they are associated with micaceous sandstone, are less 

 calcareous, and in a great measure lose their mineralogical characters ; but 

 thev may easily be detected when struck by the hammer, by their olTensively 

 bituminous odour. Near Coul (the seat of Sir George Mackenzie), and for 



* For example, in the higher part of the Alness, Tor Achilty j in the hills above Fairburn, 

 Mealfourvonie, Foyers, &c. &c. 



