ME MILNE ON THE GEOLOGY OF ROXBURGHSHIRE. 497 



He remarks on the total absence of lime and sulphur from the clay, as proving 

 that the nodules which contain these two substances, could not have been formed 

 in the clay itself; and this is his chief argument for the organic origin of the 

 stones. 



But this very diversity of chemical character, appears to me to explain the 

 formation of the concretions. If carbonate of lime and sulphur are capable of 

 exciting chemical attraction or repulsion, it is plain that these substances, origi- 

 nally existing in the clay, might easily produce concretions. Innumerable ex- 

 amples occur of the formation in this way, of nodules composed of iron pyrites, 

 carbonate of lime, and many other substances, the particles of which must have 

 separated from the general mass of matter through which they had been inter- 

 spersed, and formed bodies variously shaped.* 



Whilst in this way it would not be difficult, on ordinary and well-known 

 principles, to account for the formations of these fairy stones in the interior of 

 the clay bed, certain it is that they are also formed when exposed to atmospheric 

 influence. Both at the Fairy Dean, and on the banks of the Tweed near Berwick, 

 I have picked up small portions of the clay about the size and shape of a walnut, 

 hard on the surface, but perfectly soft and plastic in the interior. They were 

 evidently in an incipient state of consolidation and chemical arrangement, pro- 

 bably induced by evaporation and the action of the external air. One of these 

 half-consolidated nodules I took home, and in a couple of days it became as com- 

 pact, and nearly as well shaped, as any of the rest. 



I have stated that these stones, besides being of a spherical form, more or 

 less flattened, generally consist of laminae, which are the same in character with 

 the laminae of stratification in the bed of clay. This circumstance affords addi- 

 tional proof that these stones are concretions formed by chemical action in the 

 clay. In this respect they bear a very close resemblance to the calcareous nodules 

 described by DE LA BECHE as existing in the marl beds of Lyme Regis, f 



I here conclude my Memoir on the Geology of Roxburghshire. Whatever 

 may be thought of the description which I have given of its different formations, 

 or of the views which I have offered in explanation of them, this much will be 

 conceded, that it is a district containing many phenomena of novelty and interest, 

 and the study of which is calculated to throw some additional light both upon the 

 structure of the earth and on revolutions which have taken place on its surface. 



* See Lyell's Elements, p. 76, 77, for examples, and an explanation of this concretionary structure, 

 f Geological Researches, p. 95. 



VOL. XV. PABT III. 6 S 



