1873.] JUDD THE SECONDAKY K0CK8 OP SCOTLAND. 173 



road-side banks, &c, occur the argillaceous beds which are dug at 

 Clay side as already noticed. 



A little to the north of Bakkies there is in the deer-forest an old 

 and deep pit, lying N.N.W. from Dunrobin Castle. The strata seen 

 here consist of coarse white or slightly ferruginous sandstone, occa- 

 sionally passing into grit, with a few pebbles of white quartzite 

 scattered through them. Some of the finer beds are indurated into 

 a kind of pseudo-quartzite. There is about 40 feet of rock exposed 

 in this quarry, the beds dipping E.S.E. 30°. The fossils obtained 

 here consist only of a few very unsatisfactory casts of Ceromya ?, 

 Myacites, or Homomya, and Modiola (?). I am unable to decide 

 whether these beds belong to the Middle or the Lower Oolite ; and 

 the same doubt exists about some of the beds exposed in the neigh- 

 bourhood of Strathsteven. 



These Jurassic sandstones exposed inland often dip at considerable 

 angles, and are greatly disturbed ; probably also they are affected 

 by a series of fractures transverse to the great fault which has 

 thrown them against the Palaeozoic rocks. In the tract where they 

 occur, which, besides being much masked by drift, is almost wholly 

 covered by woods, it is impossible to trace and map the position of 

 these smaller faults, though the effects produced by them are often 

 sufficiently obvious. 



D. Coralline Oolite. — The great series of sandstones just de- 

 scribed, of which the total thickness cannot be less than 400 feet, 

 is probably, like others of the kind in Sutherland, of estuarine 

 origin ; the thin bands containing casts of marine shells, which we 

 have described in it, marking only temporary and local incursions of 

 the sea. It is succeeded, however, by another set of deposits, in 

 which beds with marine characters predominate. These are unfor- 

 tunately not well exposed, so as to admit of the exact tracing of the 

 succession and thickness of the several strata. At the time of 

 Farey's survey of the district, in 1813, there were a number of pits 

 in which the limestones and clays of this series of beds were dug ; 

 and by means of trial-holes he succeeded in tracing their lines of 

 outcrop across the country. Some of these pits appear to have been 

 still open in 1826, when Sir Roderick Murchison made his exami- 

 nation of the district ; but they are now all closed. Portions of the 

 series, however, are visible on both banks of the Brora, below the 

 bridge and at Ardassie Point, though, as the rocks are very im- 

 perfectly exposed and appear also to be faulted, there is some diffi- 

 culty in determining their order of succession and thickness. 



Lying upon the highest beds of the sandstone series, which, as we 

 have seen, contain numerous casts of marine shells, there occurs a 

 bed of bluish grey sandy limestone. This rock is exposed on the 

 left bank of the Brora, but is now only very imperfectly seen ; for- 

 merly, however, it was dug and burnt into lime ; and the rock is said 

 by Farey to be 12 feet thick. This bed and the other limestones of 

 the series, when exposed at the surface, weather, by the removal of 

 the calcareous matter in solution, into a very soft yellowish brown 

 sandy material, of small specific gravity, formerly used for " rotten- 



