26 MONOGRAPH OF DUllA DEN. 



that, in raising a block from the quarry, they are generally 

 attached ; the nodules in the lower bed perforate the more 

 compact substance of the upper, and lead to the conclusion that 

 they are contemporaneous deposits, and were produced under 

 the same circumstances, the heavier portions assuming their 

 position in the bed according to their specific gravity. The 

 fine-grained is uppermost, is generally of a deeper red, and 

 contains more argillaceous matter than the other two ; the mica 

 is also more abundantly distributed in minute grains through 

 the rock. 



Spots of a round spherical form, and of a yellow colour, are 

 common to all the beds, but are most numerous, as well as of 

 larger dimensions, in the upper. In some localities the spots 

 are so abundant as to cover more than a third of the surface, 

 and vary from the minutest points to nearly a foot in diameter. 

 A section of the spot across the plane of stratification is 

 uniformly circular, but when cut at right angles the figure is 

 inv^ariably spherical, wdth a dark-coloured nucleus in the centre, 

 which is occasioned, in all probability, by the discharging influ- 

 ence of animal matter. One thing is certain, that portions of 

 scales and minute bones have been detected in the centre of 

 the spots. Of this I have several specimens from Parkhill and 

 Inchture, which distinctly show the animal matter in the act 

 of solution as it were, and thereby staining the matrix in the 

 manner referred to ; while in a period so prolific in all kinds 

 of marine products, animal and vegetable, innumerable organic 

 particles would be everywhere floating in the waters, and 

 finally enveloped among the mineral deposits. The best 

 specimens of this rock are to be found at Inchture and 

 Ballindean in the Carse of Gowrie, and at Birkhill, the Glen 

 of Abernethy, and Drumdreel in Fifeshire, stretching eastward 

 through Stratheden in the line of Dura Den towards the 

 Guard Bridge. 



The extent and direction of these red sandstones may be 

 briefly traced. On the eastern coast the deposits commence 



