G. Hiclding — Old Red Sandstone of Forfarshire. 405 



places completely removed), and by the fact that the beds are so 

 irregular that they cannot all be traced from one side of the little 

 promontory to the other. 



In the more extensive outlier at St. Cyrus essentially the same 

 rock-types occur but in much greater thickness. The ' cornstone ' 

 type is there probably 40 to 50 feet in total thickness, and is 

 covered in turn by another 30 feet of sandstone. The cornstones 

 include a beautiful band of flesh-coloured calcareous sandstone, in 

 which the limy matrix forms crystals up to about half an inch in 

 diameter, the quartz grains being included. The sandstones below 

 pass down into red sandstone with conglomerate exactly similar to 

 the rocks at Arbroath. I have not been able to make a sufficiently 

 detailed examination to estimate the thickness, which could only be 

 ascertained by careful mapping. 



Fig. 2. — Map of the Outlier of Upper Old Red Sandstone near Arbroath. 



The base of the series here, again, is unfortunately not exposed. 

 The junction of the outlier with the porphy rites at the south end is 

 a beautiful fault, not a natural boundary as shown on the Survey 

 map. At the north end the junction with the Lower Old Eed 

 conglomerates is either a fault or the Upper series is banked up 

 against an old cliff of the Lower. 



It is clear from the description which has now been given of these 

 outliers of Upper Old Red that their lithological characters are exactly 

 those of the typical Upper Old Red — red sandstones at the base, 

 passing up into more variegated calcareous sandstones and marls. The 

 upper or cornstone type has long been recognised as indicating 

 peculiar conditions of formation ; what the conditions were we are 



