158 PROCEEDINGS OE THE GEOLOGICAL SOCIETY. [Jan. 8, 



ft. in. 



seam. (These beds, from their resemblance in mineral cha- 

 racter to some of the Wealden strata, have been identified with 

 that formation) 26 



(3) Beds of brown, greenish-grey, drab, and black, somewhat sandy- 



clays (fire-clays), with seams of light-coloured argillaceous lime- 

 stone, sometimes in nodules and at other times forming con- 

 tinuous bands. These beds contain some thin seams of imperfect 

 coal, much mingled with pyrites. Fossils are rare in them ; but 

 occasional Cyrence or dwarfed Ostrecs occur, indicating their 

 estuarine character 96 



(4) Coarse white sandstones 39 



(5) Clays like 3 7 



(6) White sandstone 25 



(7) Alternations of sandstone and clay 37 6 



(8) White sandstone (thickness unknown). 



This series of estuarine strata has been proved to the depth of 

 about 230 feet ; but its thickness is probably much greater. 



The coal-bed (1) is seen on the shore at Brora, near the old salt- 

 pans ; and at this place it has frequently been dug. the overlying 

 " roof-bed " having been often removed by blasting ; it now forms a 

 very conspicuous reef on the shore at low water. Along the shore 

 opposite and to the northward of this outcrop, a number of shallow 

 pits have been suuk in the Inverbrora * Links at various dates since 

 1598 for working this bed and those a short distance below. The 

 sites of many of these old pits can still be traced. In the valley of 

 the river Brora, and at a distance of rather more than half a mile 

 from its mouth, pits have been sunk to this coal-seam, which 

 is there about 230 feet from the surface. The same bed of coal is 

 repeated by a fault to the southward, and is seen in the cliff at 

 Strathsteven, and possibly also at Clayside. 



The series (2) is that described by Mr. Robertson as so remark- 

 ably illustrating the fresh- water origin of some of the beds. I saw 

 it well exposed in a trial-hole at Strathsteven cliff. It can only be 

 examined in artificial sections. The carbonaceous shales below the 

 main coal-seam are very inflammable ; they have been tested, in 

 order to discover if they will yield illuminating oils like that ob- 

 tained from the celebrated Torbane-hill mineral. The result of 

 these trials, however, was not encouraging. 



The beds of (3) have been exposed in several borings in search of 

 coal ; and they can also be fairly well traced on the shore, where 

 the harder bands form reefs. During my residence at Brora I had 

 an excellent opportunity of studying the nature and succession of 

 the beds in a shaft and boring which were carried to a depth of 

 75 feet, in a futile endeavour to find coal. 



The strata (4 to 8) can be traced on the shore, and were also pe- 

 netrated by a boring in 1770. The sandstones (8) are evidently of 

 great thickness. As we trace the strata to the southward along 



_* It may be well to mention that the name of Inverbrora was originally 

 given to the fishing-village at the mouth of the river Brora. At the present- 

 time the name is applied to a farm at some distance inland. 



